Monsoon Updates

Monsoon Updates

Atmospheric Research Testbed in Central India (ART-CI)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Monsoon Core Zone (MCZ) , Monsoon Trough, ART-CI

Mains level: NA

Why in the news-

  • The Ministry of Earth Sciences has commissioned Atmospheric Research Testbed-Central India (ART-CI) near Bhopal.

About Atmospheric Research Testbed

  • ART-CI stands as an innovative testbed facility, pioneering the exploration of monsoon convection and land-atmosphere interactions, marking a significant advancement in climate research.
  • The Indian Institute of Tropical Meteorology (IITM), Pune leads ART-CI, operating under the Ministry of Earth Sciences (MoES).

Mission Objectives

  • ART-CI primarily targets the monsoon trough area, encompassing the Monsoon Core Zone (MCZ), a critical component of the regional climate system.
  • Understanding this zone is paramount for precise weather forecasts and accurate climate modelling within India.

Monsoon Core Zone (MCZ)

 

  • MCZ is a region in India stretching from Gujarat to West Bengal in the east.
  • India Meteorological Department demarcates it as an agricultural region where cropping is mostly rainfed.
  • It is the region within the monsoon trough area that plays a central role in the dynamics of the Indian monsoon system.
  • It is characterized by intense convective activity, significant rainfall, and crucial atmospheric interactions that influence the overall behavior of the monsoon.
  • The MCZ typically experiences a concentration of atmospheric processes that drive the onset, progression, and withdrawal of the monsoon rains across the Indian subcontinent.

Features and Capabilities

  • ART-CI’s development unfolds incrementally as part of the Atmosphere & Climate Research-Modelling Observing Systems & Services (ACROSS) umbrella scheme.
  • The facility will feature an extensive array of remote-sensing and in-situ instruments.
  • These tools would help monitoring of various atmospheric parameters like convection, cloud cover, precipitation, soil moisture, radiation levels, and microphysics.

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Monsoon Updates

Cloud Seeding

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Cloud Seeding

Mains level: Drought mitigation in India

cloud seeding

Central Idea

  • Solapur, a city with limited rainfall due to its location on the leeward side of the Western Ghats, witnessed an 18% relative enhancement in rainfall through a cloud seeding experiment.

What is Cloud Seeding?

Explanation
Definition Weather modification technique to enhance precipitation.
Objective Increase rainfall or snowfall in areas facing water scarcity or drought.
Seeding Agents Silver iodide, calcium chloride, potassium iodide, sodium chloride, etc.
Suitable Clouds Typically convective clouds with moisture and vertical motion.
Methods of Dispersion Aircraft, rockets, ground-based generators, drones.
Environmental Impact Generally considered safe with minimal environmental impact.
Effectiveness Variable; depends on weather conditions and cloud characteristics.

About CAIPEEX Experiment

  • The initiative, known as the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX phase-4), sought to investigate the effectiveness of hygroscopic seeding in deep convective clouds.
  • Over two hours after cloud seeding, an additional 8.67mm of rainfall was recorded, resulting in 867 million litres of augmented water availability.

Importance of the Experiment

  • Growing NCD Burden: As India grapples with a rising burden of non-communicable diseases (NCDs), exacerbated by the consumption of pre-packaged foods, informed consumer choices and food safety become paramount.
  • Cloud Seeding Efficacy: The experiment underscores cloud seeding as an effective strategy for enhancing rainfall, particularly in regions with suitable conditions.
  • Cost-Benefit Analysis: The research evaluates the cost-effectiveness of cloud seeding, estimating the cost of producing water through cloud seeding at 18 paise per litre.

Key Findings and Methodology

  • Randomized Seeding Experiment: The study selected 276 convective clouds, with 150 subjected to seeding and 122 serving as the control group.
  • Criteria for Seeding: Clouds with characteristics such as significant liquid water content, vertical motion indicative of cloud growth, and depth exceeding one kilometre were targeted.
  • Seeding Agent: Calcium chloride flares were employed for cloud seeding, ensuring optimal dispersion and entry into growing clouds.
  • Rainfall Enhancement: Seeded clouds produced more rainfall than unseeded ones, resulting in an 18% relative enhancement.

Implications and Future Prospects

  • Water Management: While cloud seeding alone cannot alleviate droughts, it can contribute to an 18% increase in rainfall and partially address water requirements.
  • Cost Reduction: Utilizing indigenous seeding aircraft could reduce costs by over 50%, making cloud seeding more accessible.
  • High-Resolution Numerical Model: The study has developed a numerical model to help stakeholders identify target locations, suitable clouds for seeding, and effective strategies for enhancing rainfall.

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Monsoon Updates

Southwest Monsoon begins early Withdrawal/Retreat

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Monsoon Withdrawal/Retreat

Mains level: Not Much

monsoon

Central Idea

  • India Meteorological Department (IMD) has announced withdrawal of the monsoon.

What is Monsoon Withdrawal/Retreat?

  • In India, retreating monsoon is the withdrawal of south-west monsoon winds from North India.
  • The withdrawal is gradual and takes about three months.
  • With the retreat of the monsoons, the clouds disappear and the sky becomes clear. The day temperature starts falling steeply.
  • Monsoon rains weaken all over India except few southeastern states.
  • It is helpful in Rabi crop cultivation.

Factors affecting the retreat

Two predominant factors cause the phenomenon:

(1) Land topography

  • First, the low mountain range in each region runs from north to south, shielding it from west-bound winds that trigger summer monsoon.
  • After summer, the range aids in the ‘orographic lift’ or rising of east-bound air mass from a lower to higher elevation, forming clouds and resulting in rain.

(2) Atmospheric convection

  • The second factor is atmospheric convection or vertical movement of air.
  • As the earth is heated by the sun, different surfaces absorb different amounts of energy and convection may occur where the surface heats up very rapidly.
  • As the surface warms, it heats the overlying air, which gradually becomes less dense than the surrounding air and begins to rise.
  • This condition is more favorable from September to February because of the role played by sea surface temperature or water temperature.

Immediate factors influencing withdrawal

  • The withdrawal of the monsoon is based on meteorological conditions such as-
  1. Anti-cyclonic circulation (dry air that is the opposite of a cyclone)
  2. Absence of rain in the past five days and
  3. Dry weather conditions over the region

When does it occur?

  • The monsoon withdrawal is a long-drawn process and extends into mid-October, though the IMD considers September 30 to be the final day of the season over India.
  • The rain after that is categorised as “post-monsoon” rainfall.

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Monsoon Updates

Monsoon and food inflation: a status check

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Monsoon and cropping pattern

Mains level: Monsoon's erratic behavior and its impact on Indian agriculture and food security

Monsoon

What’s the news?

  • As of July 30, the current month has witnessed a significant 15.7% above-normal rainfall, transforming the cumulative deficit into an overall 6% surplus for the period from June 1 to July 30.

Central idea

  • The southwest monsoon made a tardy start, arriving seven days late this year, resulting in 52.6% below-normal rainfall during the first two weeks. By the end of June, there was a cumulative deficiency of 10.1%. However, the scenario changed dramatically from the last week of June, as the monsoon recovered remarkably, covering the entire country by July 2—six days ahead of schedule.

The monsoon’s erratic behavior and its impact on agriculture

  • Delayed Crop Planting: The late arrival of the southwest monsoon raised concerns among farmers about their ability to sow crops on time, potentially affecting overall agricultural productivity.
  • Uneven Rainfall Distribution:
  • During the first two weeks of the monsoon, the country experienced a substantial rainfall deficit, with the overall rainfall being 52.6% below the normal long-period average.
  • Eastern and southern India, except Tamil Nadu and Maharashtra, were among the regions that received insufficient rainfall, which can lead to water stress and impact crop growth and yields.
  • Cumulative Deficiency: By the end of June, the cumulative rainfall deficiency stood at 10.1%. This cumulative deficit further intensified worries about agricultural output and food security, as it could affect the availability of water for crops during crucial growth stages.
  • Crop Recovery: Despite the abysmal start, the monsoon showed signs of recovery. This turnaround led to increased kharif crop plantings, including rice, which had been lagging behind last year’s levels until mid-July.
  • Positive Impact on Sowing: The monsoon’s recovery improved sowing conditions for most major agricultural regions, except for certain areas in Uttar Pradesh, Bihar, Jharkhand, and West Bengal, where rainfall remained deficient.
  • Subsequent Impact on Yields: While the monsoon’s recovery positively impacted crop sowing, the ultimate impact on yields would largely depend on the rainfall during August and September.

El Niño Concerns

  • The Oceanic Niño Index (ONI) in June exceeded the El Niño threshold of 0.5 degrees, reaching 0.8 degrees Celsius.
  • Many global weather agencies predicted that El Niño would persist and strengthen through the 2023-24 winter.
  • El Niño’s potential strengthening raised concerns about its impact on India’s monsoon in the coming months, particularly during August.
  • El Niño is known to suppress rainfall in India, which could lead to a weakening of the monsoon during this crucial period.
  • A weakened monsoon can adversely affect crop growth, yields, and overall agricultural productivity.
  • If rainfall activity becomes progressively weaker due to El Niño’s influence, the implications can extend beyond the kharif season and impact the rabi winter-spring crops as well.
  • Rabi crops, dependent on stored rainwater, might be more vulnerable to a weakened monsoon, leading to potential losses and food production challenges.

Prospects of food security: Food inflation and stock situation

  • Rice and Wheat Stocks: As of July 1, rice and wheat stocks in government godowns were reported to be at 71.1 million tonnes (mt). This stock level is the lowest in five years for this date.
  • Impact of the Delayed Monsoon on Rice Planting:
  • Due to the delayed monsoon, rice acreage initially picked up only after mid-July. It is unclear how much of this acreage is under short-duration varieties (around 125 days from seed to grain maturity).
  • If the rice belt had received rain on time, farmers might have planted more long-duration varieties (around 150–155 days), which yield higher at about 1–2 tonnes per hectare.
  • Re-transplanting in Punjab and Haryana: There are reports of farmers in Punjab and Haryana having to undertake paddy re-transplanting in large areas along the Beas, Sutlej, Ghaggar, and Yamuna rivers. This re-transplanting is likely for shorter duration varieties that usually yield less.
  • Sugar Stocks and Exports: The estimated sugar stocks with mills at the end of September 2023 are projected to be 6.3 mt, a six-year low. The Indian government has already banned exports of sugar to manage domestic supply.
  • Pulses and Edible Oil:
  • Among pulses, arhar (pigeon-pea) and urad (black gram) have registered a dip in acreage due to rain deficiency in Maharashtra, Karnataka, and Telangana. However, Rajasthan is expected to deliver a bumper crop of moong (green gram).
  • Chana (chickpea) has ample stocks due to government procurement, and masoor (red lentil) is being imported at rates below the government’s minimum support price.
  • Edible Oil Inflation: Edible oil inflation is likely to remain low, supported by imports projected to exceed 15 mt, a new all-time high, by the end of the current oil year in October 2023.
  • Milk Production and Prices: The supply of milk is expected to ease with buffalo calvings beginning from August. This will reflect in increased milk production, peaking during the winter and remaining high until next March-April.
  • Vegetables: Vegetable inflation has been on the rise, contributing to an unacceptably high consumer price index inflation number for July. However, with faster supply responses, vegetable inflation is expected to fall as easily as it rose.

Way forward

  • Monitor Monsoon Developments: Continuously monitor the progress of the monsoon and its distribution across regions. Timely and accurate weather forecasting can help farmers make informed decisions about crop planting and irrigation.
  • Crop Diversification: Encourage farmers to diversify their crop choices to reduce dependence on water-intensive crops. Promote the cultivation of climate-resilient crops that require less water and are suitable for specific agro-climatic zones.
  • Strategic Buffer Stock: Maintain a strategic buffer stock of essential food commodities like rice and wheat to address any temporary supply shortages and stabilize food prices during periods of volatility.
  • Supply Chain Management: Improve supply chain logistics to ensure smooth transportation and distribution of agricultural produce. This will help prevent post-harvest losses and ensure the timely availability of food in the market.
  • Price Stabilization Measures: Implement effective price stabilization measures to control food inflation and prevent price volatility. These measures may include regulating exports, imports, and MSP (Minimum Support Price) mechanisms.
  • Encourage Pulses and Oil seed Production: Provide incentives and support to farmers for increasing pulses and oilseed production. This can reduce the country’s dependence on imports and stabilize prices.
  • Support the Dairy Sector: Extend support to the dairy sector to enhance milk production and improve the availability of dairy products. This can help stabilize milk prices and ensure food security.

Conclusion

  • The monsoon’s erratic behavior has impacted crop sowing and food inflation in India. While the recovery has been promising, concerns over El Niño persist, making it vital for the government to monitor the agricultural sector closely and implement appropriate measures to ensure food security.

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Monsoon Updates

Indian Ocean Dipole : What is it, how it can limit El Nino effects?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: El nino, la nina, IOD

Mains level: impacts of El Nino on the Indian monsoon and interplay between ENSO and IOD from the mains perspective

Central Idea

  • With the El Nino phenomenon set to affect the Indian monsoon this year, there is growing optimism surrounding the development of a positive Indian Ocean Dipole (IOD) and its ability to mitigate the effects of El Nino. The IOD, a weaker ocean-atmosphere interaction in the Indian Ocean, has demonstrated limited impacts in the past but holds potential in offsetting the adverse effects of El Nino, particularly in neighbouring regions.

*Relevance of the topic*

*Questions on Indian ocean dipole and El nino and its impact on Indian monsoon have been asked multiple times in previous years.

*Relate this topic with Indian monsoon, and its impact on Indian agriculture as, Rainfed agriculture occupies about 51 percent of country’s net sown area and accounts for nearly 40 percent of the total food production.

The current status of the Indian Ocean Dipole (IOD) and El Nino

  • IOD:
  • The IOD is currently in a neutral phase. This means that there is no significant temperature difference between the western and eastern sides of the Indian Ocean along the equator.
  • However, international climate models suggest the possibility of a positive IOD event developing in the coming months.
  • The India Meteorological Department (IMD) has also reported an 80% chance of a positive IOD during the June-August 2023 season. The development of a positive IOD would have implications for weather patterns in the Indian Ocean region.
  • El Nino:
  • El Nino has already established itself in the Pacific Ocean this year. El Nino occurs when the prevailing wind systems weaken, resulting in reduced displacement of warm waters in the eastern side of the Pacific.
  • This abnormal warming of the eastern Pacific can have impacts on global weather patterns, including the Indian monsoon. The presence of El Nino raises concerns about its potential impact on the Indian monsoon rainfall.

Understanding El Nino and IOD

Phenomenon El Nino Indian Ocean Dipole (IOD)
Definition Warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean Ocean-atmosphere interaction in the Indian Ocean
Cause Weakening or reversal of trade winds Temperature difference between the western and eastern parts of the Indian Ocean along the equator
Impact on Weather Disrupts atmospheric circulation patterns globally, leading to droughts, floods, and changes in temperature and precipitation patterns Influences regional weather patterns in the Indian Ocean basin and its surrounding landmasses
Indian Monsoon Suppresses rainfall, leading to drought conditions in some regions Positive IOD enhances rainfall along the African coastline and over the Indian subcontinent; negative IOD suppresses rainfall in affected regions
Opposite Phase La Nina (cooling of sea surface temperatures in the central and eastern equatorial Pacific) Opposite effects based on the temperature gradient between the western and eastern parts of the Indian Ocean
Relative Impact Significantly affects global weather patterns Weaker impacts compared to El Nino and La Nina, but still influences local weather patterns

The interplay between the El Nino Southern Oscillation (ENSO) and IOD

  • Triggering Mechanism: ENSO events, specifically El Nino, can trigger the development of a positive IOD in the Indian Ocean.
  • External Drivers: While external factors such as ENSO can initiate IOD events in some cases, there is evidence to suggest that IOD events can also occur due to local circulations or subsurface processes within the equatorial Indian Ocean.
  • Internal Dynamics: IOD events largely develop and mature through internal dynamics, even when triggered by external drivers. They have the potential to exhibit independent existence and can impact weather patterns in the Indian Ocean region.
  • Impact on IOD: During El Nino, the Pacific side of Indonesia tends to be cooler than normal, which influences the Indian Ocean side, leading to the development of a positive IOD.
  • Mutual Interaction: The circulation patterns of IOD and ENSO can impact each other when both events are strong. The interaction between the two phenomena can influence the intensity and duration of each event.
  • Contrasting Associations: Positive IOD events are often associated with El Nino, while negative IOD events are sometimes linked to La Nina. However, this association is not absolute, and IOD events can occur independently or have different associations depending on the specific conditions.
  • Combined Impacts: Strong IOD and ENSO events can have combined effects on weather patterns, as their circulation patterns can interact and influence each other.

The impacts of Indian Ocean Dipole

  • Rainfall Distribution: IOD significantly influences rainfall patterns in the Indian Ocean region. During a positive IOD, there is increased convection and rainfall along the African coastline and over the Indian subcontinent. Conversely, a negative IOD leads to suppressed rainfall in these regions.
  • Drought and Floods: Positive IOD events can bring above-average rainfall to the affected regions, which can alleviate drought conditions and replenish water resources. However, this increased rainfall can also result in flooding and water-related disasters in certain areas.
  • Agricultural Productivity: IOD has implications for agriculture as it affects the availability and distribution of rainfall. Positive IOD events can enhance agricultural productivity in the affected regions, while negative IOD events may lead to reduced crop yields and agricultural challenges.
  • Fisheries: IOD impacts the productivity of marine ecosystems. During positive IOD, increased upwelling of nutrient-rich waters occurs, which promotes higher fish stocks and benefits fisheries. In contrast, negative IOD can disrupt the marine food chain and impact fish populations.
  • Coral Bleaching: IOD influences sea surface temperatures, and prolonged positive IOD events can contribute to increased sea surface temperatures in the affected regions. This can lead to coral bleaching, negatively impacting coral reefs and marine biodiversity.
  • Indian Monsoon: IOD can influence the strength and distribution of the Indian monsoon rainfall. Positive IOD events are generally associated with enhanced monsoon rainfall over the Indian subcontinent, while negative IOD events can lead to reduced monsoon rainfall.
  • Weather Extremes: IOD can contribute to the occurrence of extreme weather events such as heatwaves, storms, and tropical cyclones in the Indian Ocean region.
  • Economic and Social Impacts: The impacts of IOD on rainfall, agriculture, fisheries, and other sectors have direct economic and social implications. These impacts can affect livelihoods, water availability, food security, and overall economic development in the affected regions.

Impacts of El Nino on the Indian monsoon

  • Weakened Monsoon Winds: During El Nino, the trade winds that blow from the east across the Indian Ocean weaken. These winds are responsible for carrying moisture-laden air towards the Indian subcontinent, facilitating the monsoon rainfall. With weakened winds, the supply of moisture is reduced, leading to a decrease in rainfall.
  • Delayed Onset: El Nino can cause a delayed onset of the Indian monsoon. The normal onset of monsoon rainfall in India is around June, but during El Nino years, the monsoon arrival may be delayed, resulting in a late start to the rainy season.
  • Deficient Rainfall: El Nino events often lead to below-average rainfall during the monsoon season in India. The reduced moisture transport and altered atmospheric circulation associated with El Nino result in deficient rainfall across various parts of the country.
  • Regional Variations: The impact of El Nino on the Indian monsoon is not uniform throughout the country. Certain regions, particularly central and northern India, are more prone to experiencing below-average rainfall during El Nino years. However, some areas in southern India may receive near-normal or even above-normal rainfall during these periods.
  • Drought Conditions: El Nino-induced deficient rainfall can result in drought conditions in affected regions. This can have adverse effects on agriculture, water availability, and livelihoods, leading to crop failures, reduced agricultural productivity, and water scarcity.
  • Temperature Extremes: El Nino can contribute to increased temperatures during the monsoon season in some parts of India. The reduced cloud cover and rainfall can lead to heatwaves and higher temperatures, posing health risks and impacting human well-being.

Conclusion

  • While the IOD’s ability to counterbalance the effects of El Nino is limited, there is hope that a positive IOD event may develop in the coming months. Past instances, such as the strong IOD event in 2019, have demonstrated the potential of IOD in compensating for monsoon rainfall deficits. As researchers continue to study the interplay between ENSO and IOD, the development of a positive IOD this year would be welcomed, offering some respite from the anticipated impacts of El Nino on the Indian monsoon.

Also read:

What is El Nino and How it impacts the Monsoon?

 

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Monsoon Updates

What is El Nino and How it impacts the Monsoon?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: ENSO, El Nino, La Nina, Monsoon

Mains level: Read the attached story

el nino

Central Idea

  • Delay in Monsoon: Any discussion on Indian monsoon delay these days invariably has references to the El Nino phenomenon.
  • Sudden rise of El Nino: This year’s monsoon is also progressing under the cloud of an El Nino in the Pacific Ocean.

Understanding El Nino and La Nina

  • El Nino and La Nina are two opposite phases of the El Nino-Southern Oscillation (ENSO) cycle.
  • ENSO is a naturally occurring phenomenon that involves the interaction between the ocean and atmosphere in the equatorial Pacific.

Here is a detailed comparison of El Nino and La Nina

El Nino La Nina
Definition Warmer-than-normal sea surface temperatures Cooler-than-normal sea surface temperatures
Frequency Every two to seven years Every two to seven years
Duration Several months to a year or more Several months to a year or more
Impact on winds Weakens trade winds, leading to changes in patterns Strengthens trade winds, leading to changes in patterns
Impact on rains Reduces rainfall and can cause droughts Increases rainfall and can cause flooding
Impact on temp. Warmer-than-average temperatures Colder-than-average temperatures
Global effects Droughts in Asia and Africa, floods in Americas Floods in Asia and Africa, droughts in South America

 

Impact on India

El Nino La Nina
Associated with weak monsoons and drought-like conditions in India Associated with above-normal rainfall and floods in India
Sea surface temperature in the equatorial Pacific Ocean rises above normal levels Sea surface temperature in the equatorial Pacific Ocean drops below normal levels
Changes in the atmospheric circulation patterns Changes in the atmospheric circulation patterns
Shift in the location of the jet stream, affecting the strength and direction of the monsoon winds Increase in the strength of the monsoon winds, bringing more moisture and rainfall to India
Results in reduced rainfall, dry spells, and heatwaves, leading to crop failures and water scarcity Excessive rainfall can also lead to floods and landslides, causing damage to crops and infrastructure

 

El Nino and Indian Monsoon

  • El Nino and its impact on Indian monsoon: El Nino refers to abnormal warming of surface waters in the equatorial Pacific Ocean, which tends to suppress monsoon rainfall in India.
  • Phases of El Nino Southern Oscillation (ENSO): ENSO consists of three phases in the Pacific Ocean: El Nino, La Nina (abnormal cooling), and a neutral phase with sea surface temperatures close to long-term averages.
  • Ocean and atmospheric conditions: ENSO involves not only temperature abnormalities of sea surface waters but also atmospheric conditions, including differences in sea-level air pressure and wind strength and direction.
  • Southern oscillation and the role of winds: Southern Oscillation Index measures the difference in sea-level air pressure over the western and eastern sides of the Pacific Ocean, while wind patterns play a crucial role in ENSO.

Factors triggering El Nino

  • Weakening trade winds: When the trade winds in the tropical Pacific weaken, it contributes to the occurrence of El Nino by reducing the movement of warm surface waters.
  • Changes in ocean currents: Alterations in the normal patterns of ocean currents can trigger El Nino events as they affect the distribution and accumulation of warm water in the central and eastern Pacific.
  • Variations in atmospheric pressure: Fluctuations in atmospheric pressure patterns disrupt the typical circulation associated with trade winds, which can initiate the onset of El Nino conditions.
  • Influence of oceanic Kelvin waves: The presence and behavior of oceanic Kelvin waves, large-scale waves that transport warm water eastward, play a role in the development and intensification of El Nino events.
  • Interactions with other climate modes: El Nino can be influenced by the interactions and connections with other climate phenomena such as the Indian Ocean Dipole and the Madden-Julian Oscillation, which can impact the oceanic and atmospheric conditions in the Pacific region.

Measuring the Cycle

(1) Oceanic Nino Index (ONI)

  • Measures the oceanic component of El Nino Southern Oscillation (ENSO).
  • Tracks the departure from average sea surface temperatures in the tropical Pacific Ocean.
  • Helps quantify the intensity and duration of El Nino or La Nina events.
  • Typically based on a rolling three-month average of sea surface temperature anomalies in specific regions.

(2) Southern Oscillation Index (SOI)

  • Measures the atmospheric component of ENSO.
  • Quantifies the difference in air pressure between two locations: Tahiti and Darwin.
  • Positive SOI values indicate higher pressure in the eastern Pacific and lower pressure in the western Pacific.
  • Negative SOI values indicate lower pressure in the eastern Pacific and higher pressure in the western Pacific.
  • Reflects the strength and changes in the atmospheric circulation patterns associated with ENSO.
  • Used to assess the phase and strength of ENSO and its impact on global weather and climate patterns.

Economic impact of El Nino on Indian Agriculture

  • Drought and reduced rainfall: El Nino events often lead to below-average monsoon rainfall in India, resulting in drought conditions in various regions.
  • Crop failure and lower yields: Lack of adequate water availability can lead to crop failure or lower yields for major crops such as rice, wheat, pulses, and oilseeds.
  • Increased input costs: During El Nino-induced droughts, farmers may need to invest in additional irrigation, water management, and supplementary feeding for livestock, leading to increased input costs.
  • Price fluctuations: Reduced crop production due to El Nino can affect market supply, leading to price fluctuations and potential inflation in food prices.
  • Livestock and fisheries: Water scarcity and changes in marine ecosystems can negatively affect animal husbandry and fishing activities, disrupting the livelihoods of those dependent on these sectors.
  • Rural livelihoods and migration: The economic stress created can impact rural livelihoods, leading to increased migration from rural to urban areas in search of alternative employment opportunities.

Try this PYQ:

La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino?

  1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
  2. El Nino has an adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

 

Post your answers here.
1
Please leave a feedback on thisx

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Monsoon Updates

Monsoon onset in Kerala on June 4

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Monsoon terminologies

Mains level: Not Much

monsoon

Central Idea: The monsoon is likely to set in over Kerala with a “slight delay” on June 4, the India Meteorological Department (IMD) said. The usual onset date over Kerala is June 1, within a seven-day window.

What does the “Onset of Monsoon” mean?

  • The onset of the monsoon over Kerala marks the beginning of the four-month, June to September southwest monsoon season over India.
  • It brings more than 70 per cent of the country’s annual rainfall.
  • It marks a significant transition in the large-scale atmospheric and ocean circulations in the Indo-Pacific region.
  • The IMD announces it only after certain newly defined and measurable parameters, adopted in 2016, are met.
  • The onset is a significant day in India’s economic calendar.

How does IMD predict the monsoon?

  • Broadly, the IMD checks for the consistency of rainfall over a defined geography, its intensity, and wind speed:
  1. Rainfall: The IMD declares the onset of the monsoon if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep record at least 2.5 mm of rain for two consecutive days at any time after May 10.
  2. Wind field: The depth of westerlies should be upto 600 hectopascal (1 hPa is equal to 1 millibar of pressure) in the area bound by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE. The zonal wind speed over the area bound by 5-10ºN latitude and 70-80ºE longitude should be of the order of 15-20 knots (28-37 kph) at 925 hPa.
  3. Heat: The INSAT-derived Outgoing Longwave Radiation (OLR) value (a measure of the energy emitted to space by the Earth’s surface, oceans, and atmosphere) should be below 200 watt per sq m (wm2) in the box confined by 5-10ºN latitude and 70-75ºE latitude.
  • The onset is not officially declared until the prescribed conditions (above) are met.

Factors considered by IMD

  • The IMD uses a specialised model that forecasts the arrival dates within a four-day window.
  • It uses six predictors:
  1. Minimum temperatures over northwest India
  2. Pre-monsoon rainfall peak over south Peninsula
  3. Outgoing long-wave radiation (OLR) over the South China Sea
  4. Lower tropospheric zonal wind over the southeast Indian Ocean
  5. Upper tropospheric zonal wind over the east equatorial Indian Ocean, and
  6. OLR over the southwest Pacific region

Back2Basics: Long Period Average (LPA)

  • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
  • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
  • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
  • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
  • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

Why LPA is needed?

  • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
  • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
  • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
  • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
  • It also takes into account the increasingly common extreme weather events caused by climate change.

Range of normal rainfall

The IMD maintains five rainfall distribution categories on an all-India scale. These are:

  1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
  2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
  3. Above normal, when actual rainfall is 104-110% of LPA;
  4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
  5. Excess, when the departure of actual rainfall is more than 110% of LPA.

 

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Monsoon Updates

IMD predicts normal monsoon despite El Nino effect

Note4Students

From UPSC perspective, the following things are important :

Prelims level: ENSO, El Nino, La Nina, IOD

Mains level: Factors affecting Indian Monsoon

nino

Central idea

  • India’s four-year run of abundant summer monsoon rainfall is likely to end this year, with the India Meteorological Department (IMD) forecasting a 4% shortfall in the coming season.
  • The monsoon forecast for 2022 is still categorized as “normal” but at 96% of the long-period average (LPA), it is at the lowest end of the range.
  • El Nino, a cyclical phenomenon of warming in the central Pacific, is believed to be the key factor responsible for the below-normal forecast.

Factors affecting the forecast

  • El Nino: It has been linked to diminished rainfall in six out of 10 years in India, and 2022 is expected to see its development.
  • La Nina: It has been influencing the rainfall in India since 2019 and is expected to end this year.
  • Reduced snow cover in Eurasia: It can have a positive impact on the monsoon forecast, and this year’s snow cover in Eurasia was below normal.
  • Positive phase of the Indian Ocean Dipole (IOD): IOD could result in more moisture and rainfall over India during August and September, and therefore, have a reduced impact of the El Nino.
  • IMD’s dynamical monsoon forecast techniques: It involves the simulation of global atmospheric and ocean conditions to forecast climate conditions, which the IMD has started to rely on more heavily in recent years.

What is El Nino and La Nina?

  • El Nino and La Nina are two opposite phases of the El Nino-Southern Oscillation (ENSO) cycle.
  • ENSO is a naturally occurring phenomenon that involves the interaction between the ocean and atmosphere in the equatorial Pacific.

Here is a detailed comparison of El Nino and La Nina

El Nino La Nina
Definition Warmer-than-normal sea surface temperatures Cooler-than-normal sea surface temperatures
Frequency Every two to seven years Every two to seven years
Duration Several months to a year or more Several months to a year or more
Impact on winds Weakens trade winds, leading to changes in patterns Strengthens trade winds, leading to changes in patterns
Impact on rains Reduces rainfall and can cause droughts Increases rainfall and can cause flooding
Impact on temp. Warmer-than-average temperatures Colder-than-average temperatures
Global effects Droughts in Asia and Africa, floods in Americas Floods in Asia and Africa, droughts in South America

 

Impacts on India

El Nino La Nina
Associated with weak monsoons and drought-like conditions in India Associated with above-normal rainfall and floods in India
Sea surface temperature in the equatorial Pacific Ocean rises above normal levels Sea surface temperature in the equatorial Pacific Ocean drops below normal levels
Changes in the atmospheric circulation patterns Changes in the atmospheric circulation patterns
Shift in the location of the jet stream, affecting the strength and direction of the monsoon winds Increase in the strength of the monsoon winds, bringing more moisture and rainfall to India
Results in reduced rainfall, dry spells, and heatwaves, leading to crop failures and water scarcity Excessive rainfall can also lead to floods and landslides, causing damage to crops and infrastructure

 


Back2Basics: Long Period Average (LPA) study of Monsoon

  • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
  • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
  • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
  • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
  • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

IMD Rainfall Distribution Categories

Rainfall Distribution Categories Percentage Departure of Actual Rainfall from LPA
Normal or Near Normal +/- 10% of LPA (between 96-104% of LPA)
Below Normal Less than 10% of LPA (90-96% of LPA)
Above Normal 104-110% of LPA
Deficient Less than 90% of LPA
Excess More than 110% of LPA

 

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Monsoon Updates

Southwest Monsoon begins early Withdrawal/Retreat

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Retreat of Monsoon

Mains level: Not Much

The southwest monsoon rainfall, 7% more than normal, has started to withdraw.

What is Monsoon Withdrawal/Retreat?

  • In India, retreating monsoon is the withdrawal of south-west monsoon winds from North India.
  • The withdrawal is gradual and takes about three months.
  • With the retreat of the monsoons, the clouds disappear and the sky becomes clear. The day temperature starts falling steeply.
  • Monsoon rains weaken all over India except few southeastern states.
  • It is helpful in Rabi crop cultivation.

Factors affecting the retreat

Two predominant factors cause the phenomenon:

(1) Land topography

  • First, the low mountain range in each region runs from north to south, shielding it from west-bound winds that trigger summer monsoon.
  • After summer, the range aids in the ‘orographic lift’ or rising of east-bound air mass from a lower to higher elevation, forming clouds and resulting in rain.

(2) Atmospheric convection

  • The second factor is atmospheric convection or vertical movement of air.
  • As the earth is heated by the sun, different surfaces absorb different amounts of energy and convection may occur where the surface heats up very rapidly.
  • As the surface warms, it heats the overlying air, which gradually becomes less dense than the surrounding air and begins to rise.
  • This condition is more favorable from September to February because of the role played by sea surface temperature or water temperature.

Immediate factors influencing withdrawal

  • The withdrawal of the monsoon is based on meteorological conditions such as-
  1. Anti-cyclonic circulation (dry air that is the opposite of a cyclone)
  2. Absence of rain in the past five days and
  3. Dry weather conditions over the region

When does it occur?

  • The monsoon withdrawal is a long-drawn process and extends into mid-October, though the IMD considers September 30 to be the final day of the season over India.
  • The rain after that is categorised as “post-monsoon” rainfall.

Try this PYQ:

Q.The seasonal reversal of winds is the typical characteristic of:

(a) Equatorial climate

(b) Mediterranean climate

(c) Monsoon climate

(d) All of the above climates

 

Post your answers here.
6
Please leave a feedback on thisx

 

Also read:

Various terms related to Indian Monsoon

 

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Monsoon Updates

What is a Triple-Dip La Nina?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Triple Dip La-Nina

Mains level: Read the attached story

nina

Parts of the world are expected to experience severe weather for the rest of the year and into 2023, as part of a rare “triple dip La Nina” event, according to the World Meteorological Organization (WMO).

 What is the “Triple-Dip” La Nina?

  • A “triple-dip” La Nina is a multiyear cooling of the surface temperature of the equatorial Pacific Ocean, which can cause droughts, fierce winds and heavy rainfall.
  • According to WMO, the current La Nina is projected to span three consecutive northern hemisphere winters. It began in September 2020.
  • If it continues for the next six months, it will be the first “triple-dip” La Nina event of the 21st century, WMO says.

How rare is this triple-dip?

  • It is exceptional to have three consecutive years with a la Nina event.
  • Its cooling influence is temporarily slowing the rise in global temperatures – but it will not halt or reverse the long-term warming trend.
  • La Nina’s are usually preceded by El Nino, a weather pattern that warms the surface of the eastern tropical Pacific Ocean.
  • However, an El Nino event did not occur before the current La Nina.

Has it happened before? Will it happen again?

  • La Nina’s occurred several times between 1903 to 2010 and 2010 to 2012.
  • This would be the first “triple-dip” La Nina this century.
  • However, it is not unprecedented for the weather pattern to last more than nine months to a year, which is typical for a La Nina.

Evaluating the likely impact

  • In the Indian context, La Nina is associated with good rainfall during the monsoon season.
  • This is the opposite of El Nino which is known to suppress monsoon rainfall.
  • Thus, a continued spell of La Nina could lead to expectation of another year of good, or normal, rainfall during the monsoon.
  • Until now, the monsoon season this year has produced 7% more rain compared to normal. Last year, the seasonal rainfall was almost 100%.
  • But, even though powerful, ENSO condition is only one of the several factors affecting monsoon rainfall in India.

Impact on rainfall

  • There is no one-on-one correlation between the ENSO condition and the amount of rainfall.
  • Also, the influence of ENSO is at a macro level.
  • There are wide variations in rainfall at the local level, which are getting exacerbated by climate change.

Differential impacts of this triple-dip event

  • The continuance of La Nina further into 2023 is not bad news from the Indian standpoint. But it is not the same for many other regions where La Nina has very different impacts.
  • In most parts of the United States, for example, La Nina is associated with very dry winters.
  • In Australia and Indonesia, and generally in the tropical region, La Nina is expected to bring more rainfall.
  • The excessive rainfall in Pakistan, which is experiencing its worst flooding disaster, can also be blamed in part on La Nina.
  • It said that the persistence of La Nina was most likely to result in a worsening of the drought in Africa.

What is its climate change link?

  • Every unusual weather event these days is attributed to climate change, but science is not conclusive right now.
  • The occurrences of El Nino or La Nina are not very regular.
  • Sometimes they emerge every two years, at other times there has been a gap of even seven years.
  • Historical records do not go very far in the past.
  • As a result, the natural variability of ENSO is not understood very clearly.
  • And when the natural variability itself is not clear, the influence of global warming is difficult to quantify.
  • But there is clearer evidence of another kind of linkage with global warming.
  • During La Nina years, the colder surfaces allow the oceans to absorb more heat from the atmosphere.
  • Consequently, the air temperatures tend to go down, producing a cooling effect.

 

 

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Monsoon Updates

Abnormal’ La Nina conditions impacting India’s monsoon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: El-Nino, La-Nina

Mains level: ENSO impact on Indian Monsson

In what may be termed as an uncommon ocean phenomenon, the prevailing La Nina conditions over the equatorial Pacific Ocean have entered the third consecutive year.

What is the news?

  • The current La Nina phase has been prevailing since September 2020.
  • Since the 1950s, La Nina lasting for more than two years has been recorded only on six instances (see graph below), data by the India Meteorological Department (IMD) stated.
  • It confirmed that India’s La Nina conditions are here to stay till the end of 2022.

What is El Nino and La Nina?

  • While El Nino (Spanish for ‘little boy’), the more common expression, is the abnormal surface warming observed along the eastern and central regions of the Pacific Ocean (the region between Peru and Papua New Guinea).
  • The La Nina (Spanish for ‘little girl’) is an abnormal cooling of these surface waters.
  • Together, the El Nino (Warm Phase) and La Nina (Cool Phase) phenomena are termed as El Nino Southern Oscillation (ENSO).
  • These are large-scale ocean phenomena that influence the global weather — winds, temperature and rainfall. They have the ability to trigger extreme weather events like droughts, floods, hot and cold conditions, globally.
  • Each cycle can last anywhere between 9 to 12 months, at times extendable to 18 months — and re-occur after every three to five years.
  • Meteorologists record the sea surface temperatures for four different regions, known as Nino regions, along this equatorial belt.
  • Depending on the temperatures, they forecast either as an El Nino, an ENSO neutral phase, or a La Nina.

Why has La Nina conditions continued for 3 years?

  • It is surprising that it has continued for the last three years. It may be good for India but not for some other countries.
  • Under climate change conditions, one must expect more such instances. Climate change could be a factor driving such anomalous conditions.

Issues with La Nina

  • La Nina years are infamous for frequent and intense hurricanes and cyclones in the Atlantic Ocean and the Bay of Bengal.
  • Chances of more cyclones are likely due to multiple aiding factors, including high relative moisture and relative low wind shear over the Bay of Bengal.

 

Try this PYQ:

Q. La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino?

  1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
  2. El Nino has an adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

 

Post your answers here.
14
Please leave a feedback on thisx

 

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Monsoon Updates

Monsoon sets in over Kerala

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Various terms related to Monsoon

Mains level: Indian Monsoon

The monsoon has reached Kerala, the India Meteorological Department (IMD).

What does the “Onset of Monsoon” mean?

  • The onset of the monsoon over Kerala marks the beginning of the four-month — June-September — southwest monsoon season over India.
  • It brings more than 70 per cent of the country’s annual rainfall. This marks a significant day in India’s economic calendar.
  • IMD announces it only after certain newly defined and measurable parameters, adopted in 2016, are met.
  • Broadly, the IMD checks for the consistency of rainfall over a defined geography, its intensity, and wind speed.

(1) Rainfall

  • The IMD declares the onset of the monsoon if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep.
  • The 14 enlisted stations are: Minicoy, Amini, Thiruvananthapuram, Punalur, Kollam, Alappuzha, Kottayam, Kochi, Thrissur, Kozhikode, Thalassery, Kannur, Kasaragod, and Mangaluru.
  • It records at least 2.5 mm of rain for two consecutive days at any time after May 10.
  • In such a situation, the onset over Kerala is declared on the second day, provided specific wind and temperature criteria are also fulfilled.

(2) Wind field

  • The depth of westerlies should be up to 600 hectopascal (1 hPa is equal to 1 millibar of pressure) in the area bound by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE.
  • The zonal wind speed over the area bound by 5-10ºN latitude and 70-80ºE longitude should be of the order of 15-20 knots (28-37 kph) at 925 hPa.

(3) Heat

  • According to IMD, the INSAT-derived Outgoing Longwave Radiation (OLR) value (a measure of the energy emitted to space by the Earth’s surface, oceans, and atmosphere) should be below 200 watt per sq m (wm2).
  • This is measured in the box confined by 5-10ºN latitude and 70-75ºE latitude.

Is it unusual for the monsoon to hit the Kerala coast early?

  • Neither early nor late onset of the monsoon is unusual.
  • In 2018 and 2017, the onset over Kerala occurred on May 29 and May 30, respectively.
  • In 2010, onset was realised on May 31.
  • In 2020 and 2013, the monsoon was exactly on time, hitting the Kerala coast on June 1.

Does an early onset foretell a good monsoon?

  • No, it does not — just as a delay does not foretell a poor monsoon.
  • The onset is just an event that happens during the progress of the monsoon over the Indian subcontinent.
  • A delay of a few days, or perhaps the monsoon arriving a few days early, has no bearing on the quality or amount of rainfall.

How does the monsoon spread across the country after hitting Kerala coast?

  • The northward progression of the monsoon after it has hit the Kerala coast depends on a lot of local factors, including the creation of low pressure areas.
  • Though this year monsoon has arrived early, it is possible that despite a late onset over Kerala, other parts of the country start getting rain on time.
  • After its onset over Kerala, the monsoon spreads over the entire country by July 15.

Back2Basics:

Various terms related to Indian Monsoon

 

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Monsoon Updates

What is Onset of Monsoon?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Various terms related to Monsoon

Mains level: Read the attached story

The monsoon is slated to make its earliest arrival in 13 years over Kerala, informs the India Meteorological Department (IMD).

What does the “Onset of Monsoon” mean?

  • The onset of the monsoon over Kerala marks the beginning of the four-month, June to September southwest monsoon season over India.
  • It brings more than 70 per cent of the country’s annual rainfall.
  • It marks a significant transition in the large-scale atmospheric and ocean circulations in the Indo-Pacific region.
  • The IMD announces it only after certain newly defined and measurable parameters, adopted in 2016, are met.
  • The onset is a significant day in India’s economic calendar.

How does IMD predict the monsoon?

  • Broadly, the IMD checks for the consistency of rainfall over a defined geography, its intensity, and wind speed:
  1. Rainfall: The IMD declares the onset of the monsoon if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep record at least 2.5 mm of rain for two consecutive days at any time after May 10.
  2. Wind field: The depth of westerlies should be upto 600 hectopascal (1 hPa is equal to 1 millibar of pressure) in the area bound by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE. The zonal wind speed over the area bound by 5-10ºN latitude and 70-80ºE longitude should be of the order of 15-20 knots (28-37 kph) at 925 hPa.
  3. Heat: The INSAT-derived Outgoing Longwave Radiation (OLR) value (a measure of the energy emitted to space by the Earth’s surface, oceans, and atmosphere) should be below 200 watt per sq m (wm2) in the box confined by 5-10ºN latitude and 70-75ºE latitude.
  • The onset is not officially declared until the prescribed conditions (above) are met.

Factors considered by IMD

  • The IMD uses a specialised model that forecasts the arrival dates within a four-day window.
  • It uses six predictors:
  1. Minimum temperatures over northwest India
  2. Pre-monsoon rainfall peak over south Peninsula
  3. Outgoing long-wave radiation (OLR) over the South China Sea
  4. Lower tropospheric zonal wind over the southeast Indian Ocean
  5. Upper tropospheric zonal wind over the east equatorial Indian Ocean, and
  6. OLR over the southwest Pacific region

Where is the early arrival noticed?

  • The monsoon’s arrival over India is marked by rain over south Andaman Sea, which then advances north-westwards across the Bay of Bengal.
  • In general, the Andaman and Nicobar Islands start receiving monsoon rainfall between May 15 and May 20 every year.
  • And it usually starts raining along the Kerala coast in the last week of May.

Does an early onset foretell a good monsoon?

  • No, it does not — just as a delay does not foretell a poor monsoon.
  • The onset is just an event that happens during the progress of the monsoon over the Indian subcontinent.
  • A delay of a few days, or perhaps the monsoon arriving a few days early, has no bearing on the quality or amount of rainfall, or its regional distribution across the country.

Back2Basics: Long Period Average (LPA)

  • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
  • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
  • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
  • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
  • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

Why LPA is needed?

  • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
  • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
  • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
  • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
  • It also takes into account the increasingly common extreme weather events caused by climate change.

Range of normal rainfall

The IMD maintains five rainfall distribution categories on an all-India scale. These are:

  1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
  2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
  3. Above normal, when actual rainfall is 104-110% of LPA;
  4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
  5. Excess, when the departure of actual rainfall is more than 110% of LPA.

Also read

Various terms related to Indian Monsoon

 

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Monsoon Updates

What is the ‘Long Period Average’, IMD’s benchmark for monsoon prediction?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: LPA, Indian Monsoon

Mains level: Not Much

India is likely to receive a normal monsoon for the fourth consecutive year, the India Meteorological Department (IMD) said in its first Long Range Forecast (LRF) for this year.

What is Long Period Average (LPA)?

  • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
  • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
  • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
  • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
  • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

Why LPA is needed?

  • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
  • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
  • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
  • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
  • It also takes into account the increasingly common extreme weather events caused by climate change.

Range of normal rainfall

The IMD maintains five rainfall distribution categories on an all-India scale. These are:

  1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
  2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
  3. Above normal, when actual rainfall is 104-110% of LPA;
  4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
  5. Excess, when the departure of actual rainfall is more than 110% of LPA.

Also read:

Various terms related to Indian Monsoon

 

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Monsoon Updates

No El Nino expected this year

Note4Students

From UPSC perspective, the following things are important :

Prelims level: El-Nino, La-Nina

Mains level: ENSO impact on Indian Monsson

The southwest monsoon is likely to be “normal” in 2022, though rainfall in August, the second rainiest month, will likely be subdued, according to the private weather company Skymet.

El Nino and La Nina

  • While El Niño (Spanish for ‘little boy’), the more common expression, is the abnormal surface warming observed along the eastern and central regions of the Pacific Ocean (the region between Peru and Papua New Guinea).
  • The La Niña (Spanish for ‘little girl’) is an abnormal cooling of these surface waters.
  • Together, the El Niño (Warm Phase) and La Niña (Cool Phase) phenomena are termed as El Niño Southern Oscillation (ENSO).
  • These are large-scale ocean phenomena which influence the global weather — winds, temperature and rainfall. They have the ability to trigger extreme weather events like droughts, floods, hot and cold conditions, globally.
  • Each cycle can last anywhere between 9 to 12 months, at times extendable to 18 months — and re-occur after every three to five years.
  • Meteorologists record the sea surface temperatures for four different regions, known as Niño regions, along this equatorial belt.
  • Depending on the temperatures, they forecast either as an El Niño, an ENSO neutral phase, or a La Niña.

Impact on India

  • El Nino during winter causes warm conditions over the Indian subcontinent and during summer, it leads to dry conditions and deficient monsoon.
  • Whereas La Nina results in better than normal monsoon in India.
  • It has been established that Indian summer monsoon is a fully coupled land-atmosphere-ocean system and that it is linked to ocean temperature variability.
  • In an agricultural country like India, the extreme departure from normal seasonal rainfall seriously affects the agricultural output and thus the economy of the country.

Try this PYQ:

Q. La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino?

  1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
  2. El Nino has an adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

 

Post your answers here.
6
Please leave a feedback on thisx

 

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Monsoon Updates

[pib] International Monsoons Project Office (IMPO)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: International Monsoons Project Office (IMPO)

Mains level: Not Much

Union Minister of Science & Technology has launched the International Monsoons Project Office (IMPO).

International Monsoons Project Office (IMPO)

  • IMPO will be hosted at the Indian Institute of Tropical Meteorology (IITM), Pune, an institution under the Ministry of Earth Sciences, Govt of India, initially for five years.
  • Setting up the IMPO reiterates the importance of monsoons for the national economy.
  • It would encompass activities and connections related to international monsoon research that would be identified and fostered under the leadership of the World Climate Research Programme.
  • Both the World Climate Research Programme and World Weather Research Programme are international programmes coordinated by the United Nations World Meteorological Organisation (WMO).

Significance of IMPO

  • Setting up the IMPO in India would mean expanding an integrated scientific approach to solve the seasonal variability of monsoons, enhancing the prediction skill of monsoons and cyclones.
  • It would promote knowledge sharing and capacity building in areas of monsoon research crucial for agriculture, water resources and disaster management, hydropower and climate-sensitive socio-economic sectors.
  • It is a step towards making India a global hub for monsoon research and coordination in a seamless manner for addressing common and region-specific aspects of the monsoons around the world.

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Back2Basics:

Various terms related to Indian Monsoon

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Monsoon Updates

What is Samba Cultivation?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Samba Cultivation

Mains level: NA

Around four lakh more acres have been brought under the Crop Insurance Scheme for the Samba Cultivation season of 2021-22 in Tamil Nadu.

What is Samba Cultivation?

  • It is a Tamil name for paddy cultivation season.
  • Other paddy seasons in Tamil Nadu include:
  1. Kuruvai: June-July
  2. Samba: August
  3. Late Samba / Thaladi: September- October
  4. Navarai: December- January

Back2Basics: Major crop seasons

(1) Kharif Crop

  • Kharif crops, monsoon crops, or autumn crops are cultivated and harvested in the monsoon season.
  • The farmers sow seeds at the beginning of the monsoon season and harvest them at the end of the season. i.e., between September and October.
  • Kharif crops need a lot of water and hot weather for proper growth.
  • Examples: Rice, Maize, Millet, Soybean, Arhar, Cotton. etc.

(2) Rabi Crop

  • Rabi means spring in Arabic. Crops grown in the winter season [October to December] and harvested in the spring season [Aril-May] are called Rabi crops.
  • These crops require a warm climate for germination and maturation of seeds and need a cold environment for their growth.
  • Rain in winter spoils the Rabi crop but is good for the Kharif crop.
  • Examples: Wheat, Gram, Barley, Peas, Oats, Chickpea, Linseed, Mustard, etc.

(3) Zaid Crop

  • Zaid crops are grown between Kharif and Rabi Seasons, i.e., between March to June.
  • They require warm, dry weather as a vital growth period and longer day length for flowering.
  • Zaid crop is significant for farmers as it gives fast cash to the farmers and is also known as gap-filler between two chief crops, Kharif and Rabi.
  • Examples: Cucumber, Pumpkin, Bitter gourd, Watermelon, Muskmelon, Sugarcane, Groundnut, Pulses, etc.

 

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Monsoon Updates

Western Disturbances to bring rain in New Delhi

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Western Disturbances

Mains level: Not Much

Under the influence of two consecutive western disturbances, New Delhi is in for a wet spell.

Western Disturbances

  • A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
  • It is a non-monsoonal precipitation pattern driven by the westerlies.
  • The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
  • Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
  • In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
  • Western disturbances are more frequent and strong in the winter season.

Impact: Winter Rainfall and Extreme Cold

  • Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
  • They are the cause of most winter and pre-monsoon season rainfall across northwest India.
  • An average of four to five western disturbances forms during the winter season.

Its significance

  • Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.
  • Wheat among them is one of the most important crops, which helps to meet India’s food security.

Try this PYQ:

Q. Consider the following statements:

  1. The winds which blow between 30°N and 60°S latitudes throughout the year are known as westerlies.
  2. The moist air masses that cause winter rains in the North-Western region of India are part of westerlies.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

 

 

Post your answers here.
9
Please leave a feedback on thisx

 

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Monsoon Updates

Various terms related to Indian Monsoon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian monsoon

Mains level: Economic dependency on Monsoon

The monsoon is likely to begin withdrawing from the mainland from October 6, said the India Meteorological Department (IMD).

Let us learn all terminologies related to Monsoon.

What is Monsoon?

  • Indian monsoon, the most prominent of the world’s monsoon systems, which primarily affects India and its surrounding water bodies.
  • It blows from the northeast during cooler months and reverses direction to blow from the southwest during the warmest months of the year.

Onset of Monsoon

  • This process brings large amounts of rainfall to the region during June and July.
  • As the high-sun season (that is, the Northern Hemisphere summer) moves northward during April, India becomes particularly prone to rapid heating because the highlands to the north protect it from any incursions of cold air.
  • There are three distinct areas of relative upper tropospheric warmth—namely, (1) above the southern Bay of Bengal, (2) above the Plateau of Tibet, and (3) across the trunks of the various peninsulas that are relatively dry during this time.
  • These three areas combine to form a vast heat-source region.
  • In contrast, a heat sink appears over the southern Indian Ocean as the relatively cloud-free air cools by emitting long-wavelength radiation.
  • Monsoon winds at the surface blow from heat sink to heat source.

Peak period

  • The position of the easterly jet controls the location of monsoonal rains, which occur ahead and to the left of the strongest winds and also behind them and to the right.
  • The surface flow, however, is a strong, south-westerly, humid, and unstable wind that brings humidifies of more than 80 percent and heavy squally showers that are the “burst” of the monsoon.
  • The overall pattern of the advance follows a frontal alignment, but local episodes may differ considerably.

Key areas

  • Most spectacular clouds and rain occur against the Western Ghats in India, where the early monsoonal airstream piles up against the steep slopes, then recedes, and piles up again to a greater height.
  • Each time it pushes thicker clouds upward until wind and clouds roll over the barrier and, after a few brief spells of absorption by the dry inland air, cascade toward the interior.
  • Various factors, especially topography, combine to make up a complex regional pattern.

Break in Monsoon

  • During the south-west monsoon period after having rains for a few days, if rain fails to occur for one or more weeks, it is known as break in the monsoon.
  • These dry spells are quite common during the rainy season.
  • In northern India rains are likely to fail if the rain-bearing storms are not very frequent along the monsoon trough or the ITCZ over this region.
  • Over the west coast the dry spells are associated with days when winds blow parallel to the coast.

Withdrawal of Monsoon

  • By August the intensity and duration of sunshine have decreased, temperatures begin to fall, and the surge of south-westerly air diminishes spasmodically almost to a standstill in the northwest.
  • In September, dry, cool, northerly air begins to circle the west side of the highlands and spread over north-western India.
  • The easterly jet weakens, and the upper tropospheric easterlies move much farther south.
  • Because the moist southwesterlies at lower levels are much weaker and variable, they are soon pushed back.
  • The rainfall becomes extremely variable over most of the region, but showers are still frequent in the south-eastern areas and over the Bay of Bengal.
  • By early October, variable winds are very frequent everywhere.

Winter rains

  • At the end of the month, the entire Indian region is covered by northerly air and the winter monsoon takes shape.
  • The surface flow is deflected by the Coriolis force and becomes a north-easterly flow.
  • Tropical depressions and cyclones are important contributing factors.
  • Most of India thus begins a sunny, dry, and dusty season.
  • Conversely, the western slopes of the Karakoram Range and Himalayas are then reached by the midlatitude frontal depressions that come from the Atlantic and the Mediterranean.
  • The winter rains they receive, moderate as they are, place them clearly outside the monsoonal realm.

 

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Monsoon Updates

The Atlantic Niño’s role in India’s erratic monsoon

Note4Students

From UPSC perspective, the following things are important :

Prelims level: El nino and La nina

Mains level: Paper 1- Challenges in monsoon prediction

Context

Last month, farmers from Madhya Pradesh threatened to take IMD to court for the inaccurate monsoon forecast this year. A question was also raised in Parliament about whether the Arctic warming had led to an erratic monsoon this year.

Understanding the role of Atlantic Niño in monsoon prediction

  • Monsoon predictions are a monumental challenge, especially when it comes to the spatial distribution and the northward migration of the monsoon trough.
  • Forecast models tend to rely heavily on El Niño for monsoon predictions.
  • But only about 50 per cent of the dry years are explained by El Niño.
  • Clearly, Atlantic Niño is a significant player in monsoon evolution and models and forecasters must pay attention to this Atlantic teleconnection.
  • Atlantic Niño is El Niño’s little cousin in the Atlantic, also known as the Atlantic Zonal Mode.
  • Indian scientists from INCOIS have argued that the Atlantic Niño is in fact predictable up to three months in advance.
  • Every few years, from June to August, there is a warming in the eastern equatorial Atlantic, which does not get as much attention as its big brother El Niño.
  • The biggest rainfall deficits from the Atlantic Niño tend to occur over the Western Ghats and the core monsoon zone.

How Atlantic Niño plays a role if Indian and Atlantic Oceans are not connected?

  • The Atlantic and Indian Oceans are not directly connected in the tropics via the ocean.
  • The Atlantic Niño affects the monsoon by producing atmospheric waves, which propagate into the Indian Ocean.
  • These waves affect air temperatures over the Indian Ocean and influence the land-ocean thermal contrast as well as Low Pressure Systems (LPS).

Way forward

  • Overall, monsoon prediction skill has gone up in the IMD but even a 70 per cent accuracy means the forecasts will be wrong 30 per cent of the time.
  • Many of the Atlantic Niños occur during non-El Niño years and this offers a window of opportunity to increase forecast skills based on the accurate prediction of the Atlantic Niño.

Conclusion

No forecasts will ever be 100 per cent accurate. Climate scientists are also aware of the monsoon prediction challenge and they will continue to try to improve monsoon forecasts.

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Back2Basics:  El Niño and La Niña

  • These periodic weather patterns occur as a result of fluctuating ocean temperatures in one part of the world, namely the east-central equatorial Pacific Ocean.
  • This can lead to extreme weather.
  • When warm water builds up along the central and eastern tropical Pacific Ocean, an El Niño occurs.
  • Conversely, when cool water builds up along the same region, a La Niña occurs with the opposite impact.

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Monsoon Updates

Cyclone Gulab

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Tropical cyclones

Mains level: Frequent cyclonic activities in India

As a very rare occasion during monsoons, Cyclone Gulab has been developed in the Bay of Bengal and later made landfall close in Andhra Pradesh.

Tauktae, Amphan, Fani, Titli, Bulbul, Gaja… And now Gulab. As and when cyclones with intriguing names approach the Indian coasts, a common question comes to our minds: Who names these storms?

 

This time it is Pakistan, not India, who proposed this name Gulaab!

About Tropical Cyclones

  • A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure centre, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rains.
  • Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone.
  • A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and the northeastern Pacific Ocean, and a typhoon occurs in the north-western Pacific Ocean.
  • In the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

Cyclone Gulab

  • Three factors —in-sync phase of Madden Julian Oscillation (MJO), warm sea surface temperatures over the Bay of Bengal, and the formation of a low-pressure system.
  • The system’s intensification phases between low pressure – well-marked low pressure – depression – deep depression and to finally becoming Cyclone Gulab was rather rapid, even as the system moved closer to the south Odisha – north Andhra Pradesh coast, where it also made landfall.

What makes Gulab special?

  • India has a bi-annual cyclone season that occurs between March to May and October to December. But on rare occasions, cyclones do occur in June and September months.
  • Cyclones are less common during the June to September monsoon season, as there are limited or almost no favourable conditions for cyclogenesis due to strong monsoon currents.
  • This is also the period when the wind shear — that is, the difference between wind speeds at lower and upper atmospheric levels — is very high.
  • As a result, clouds do not grow vertically and monsoon depressions often fail to intensify into cyclones.
  • So it can be stated that this year, the cyclone season commenced earlier than usual. The last time a cyclone developed in the Bay of Bengal in September was Cyclone Day in 2018.

Also read

[Burning Issue] Tropical Cyclones and India

 

 

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Monsoon Updates

What is lightning, and how does it strike?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Lightening and Thunderstorms

Mains level: Not Much

With the monsoon making a slow revival over several parts of India, except the northwest region, there is a rise in lightning-linked deaths.

What is lightning?

  • Lightning is a very rapid — and massive — discharge of electricity in the atmosphere, some of which is directed towards the Earth’s surface.
  • These discharges are generated in giant moisture-bearing clouds that are 10-12 km tall.
  • The base of these clouds typically lies within 1-2 km of the Earth’s surface, while their top is 12-13 km away.
  • Temperatures towards the top of these clouds are in the range of minus 35 to minus 45 degrees Celsius.

How does it strike?

  • As water vapour moves upward in the cloud, the falling temperature causes it to condense.
  • Heat is generated in the process, which pushes the molecules of water further up.
  • As they move to temperatures below zero degrees Celsius, the water droplets change into small ice crystals. They continue to move up, gathering mass — until they are so heavy that they start to fall to Earth.
  • This leads to a system in which, simultaneously, smaller ice crystals are moving up and bigger crystals are coming down.
  • Collisions follow and trigger the release of electrons — a process that is very similar to the generation of sparks of electricity.
  • As the moving free electrons cause more collisions and more electrons, a chain reaction ensues.
  • This process results in a situation in which the top layer of the cloud gets positively charged, while the middle layer is negatively charged.

Making of the thunder

  • The electrical potential difference between the two layers is huge — of the order of a billion to 10 billion volts.
  • In very little time, a massive current, of the order of 100,000 to a million amperes, starts to flow between the layers.
  • An enormous amount of heat is produced, and this leads to the heating of the air column between the two layers of the cloud.
  • This heat gives the air column a reddish appearance during lightning. As the heated air column expands, it produces shock waves that result in thunder.

How does this current reach the Earth from the cloud?

  • While the Earth is a good conductor of electricity, it is electrically neutral.
  • However, in comparison to the middle layer of the cloud, it becomes positively charged.
  • As a result, about 15%-20% of the current gets directed towards the Earth as well.
  • It is this flow of current that results in damage to life and property on Earth.
  • There is a greater probability of lightning striking tall objects such as trees, towers or buildings.
  • Once it is about 80-100 m from the surface, lightning tends to change course towards these taller objects.
  • This happens because air is a poor conductor of electricity, and electrons that are travelling through air seek both a better conductor and the shortest route to the relatively positively charged Earth’s surface.

What precautions should be taken against lightning?

  • Lightning rarely hits people directly — but such strikes are almost always fatal.
  • People are most commonly struck by what are called “ground currents”.
  • The electrical energy, after hitting a large object (such as a tree) on Earth, spreads laterally on the ground for some distance, and people in this area receive electrical shocks.
  • It becomes more dangerous if the ground is wet (which it frequently is because of the accompanying rain), or if there is metal or other conducting material on it.
  • Water is a conductor, and many people are struck by lightning while standing in flooded paddy fields.
  • For the reasons given above, taking shelter under a tree is dangerous. Lying flat on the ground too can increase risks.
  • People should move indoors in a storm; however, even indoors, they should avoid touching electrical fittings, wires, metal, and water.

Answer this PYQ in the comment box:

Q.During a thunderstorm, the thunder in the skies is produced by the:

  1. meeting of cumulonimbus clouds in the sky
  2. lightning that separates the nimbus clouds
  3. violent upward movement of air and water particles

Select the correct option using the codes given below (CSP 2011):

(a) 1 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) None of the above

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Monsoon Updates

Retreating Monsoon is a global phenomenon: Study

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian monsoon

Mains level: Monsoon and climate change

Rainfall during retreating monsoon, which parts of South India experience every year, is not a local anomaly and is global in nature and scale, according to a recent study by the University of Sydney.

What is Retreating Monsoon?

  • In India, retreating monsoon is the withdrawal of south-west monsoon winds from North India.
  • The withdrawal is gradual and takes about three months.
  • With the retreat of the monsoons, the clouds disappear and the sky becomes clear. The day temperature starts falling steeply.
  • Monsoon rains weaken all over India except few southeastern states.
  • It is helpful in Rabi crop cultivation.

What has the research found?

  • The research has identified regions in the northern hemisphere that receive the bulk of the rainfall during September, October and November and southern hemisphere that receive most of the rainfall from March to August.
  • The discovery that these are part of a global pattern and not one-off occurrences means they can be systematically studied, which will help understand how these communities could be affected by climate change.
  • Peninsular India and parts of South-East Asia are among the eight regions examined in the study.

Factors affecting the retreat

  • The eight global regions identified by the study that receive most of their rainfall after summer, have several things in common.
  • They lie on the eastern fringes of landmasses and are in close proximity to mountain ranges with modest heights.

Two predominant factors cause the phenomenon:

  • First, the low mountain range in each region runs from north to south, shielding it from west-bound winds that trigger summer monsoon.
  • After summer, the range aids in the ‘orographic lift’ or rising of east-bound air mass from a lower to higher elevation, forming clouds and resulting in rain.
  • The second factor is atmospheric convection or vertical movement of air.
  • As the earth is heated by the sun, different surfaces absorb different amounts of energy and convection may occur where the surface heats up very rapidly.
  • As the surface warms, it heats the overlying air, which gradually becomes less dense than the surrounding air and begins to rise.
  • This condition is more favorable from September to February because of the role played by sea surface temperature or water temperature.

Answer this PYQ in the comment box:

Q.The seasonal reversal of winds is the typical characteristic of:

(a) Equatorial climate

(b) Mediterranean climate

(c) Monsoon climate

(d) All of the above climates

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Monsoon Updates

[pib] Northern Limit of Monsoon (NLM)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Northern Limit of Monsoon (NLM)

Mains level: Indian Monsoon

The Northern Limit of Monsoon (NLM) continues to pass through Diu, Surat, Nandurbar, Bhopal, Nowgong, Hamirpur, Barabanki, Bareilly, Saharanpur, Ambala & Amritsar.

Try this question from CS Mains 2017:

Q.What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 percent of the won population residing in Monsoon Asia?

What is the Northern Limit of Monsoon?

  • NLM, is the northernmost boundary of India up to which monsoon rains have advanced on any given day.
  • So, it is a way of tracking the progress of monsoon clouds as they move over India’s landmass.
  • The India Meteorological Department (IMD) adds that the monsoon “advances northwards, usually in surges, and covers the entire country around July 15″.

What are the Eastern and Western Arms?

  • It is the mountains of southern India that split the south-western winds, giving the Indian monsoon its ‘two arms.
  • The western arm of the monsoon is deflected northwards, by the Western Ghats, to (Mumbai) and then on to Pakistan.
  • The eastern arm travels up through the Bay of Bengal to (Kolkata) and Assam and is deflected north-westwards by the Himalayas.

Also refer this link:

Explain the formation of Indian monsoons. Highlight the link between monsoons and India’s cropping pattern. (15 marks)

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Monsoon Updates

Anti-hail guns to mitigate hailstorms crop damage

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Hailstorms

Mains level: NA

To help out horticulturists who face crop damage due to hailstorms, the Himachal Pradesh government will be testing the use of indigenously developed ‘anti-hail guns’.

What are anti-hail guns?

  • An anti-hail gun is a machine that generates shock waves to disrupt the growth of hailstones in clouds, according to its makers.
  • It comprises a tall, fixed structure somewhat resembling an inverted tower, several metres high, with a long and narrow cone opening towards the sky.
  • The gun is “fired” by feeding an explosive mixture of acetylene gas and air into its lower chamber, which releases a shock wave (waves that travel faster than the speed of sound, such as those produced by supersonic aircraft).
  • These shock waves supposedly stop water droplets in clouds from turning into hailstones, so that they fall simply as raindrops.

Answer this PYQ in the comment box:

Q.During a thunderstorm, the thunder in the skies is produced by the

  1. meeting of cumulonimbus clouds in the sky
  2. lightning that separates the nimbus clouds
  3. violent upward movement of air and water particles

Select the correct option using the codes given below:

(a) 1 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) None of the above

How do they ‘prevent’ a hailstorm?

  • It is this hail formation process that the shock waves from anti-hail guns try to disrupt in a radius of 500 meters, so that the water droplets fall down before they can be lifted by the updrafts.
  • The machine is repeatedly fired every few seconds during an approaching thunderstorm.
  • However, the effectiveness of anti-hail guns has remained a contentious issue.

How do Hailstorms occur?

  • Hail is produced by cumulonimbus clouds, which are generally large and dark and may cause thunder and lightning.
  • In such clouds, winds can blow up the water droplets to heights where they freeze into ice.
  • The frozen droplets begin to fall but are soon pushed back up by the winds and more droplets freeze onto them, resulting in multiple layers of ice on the hailstones.
  • This fall and rise is repeated several times, till the hailstones become too heavy and fall down.

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Monsoon Updates

Monsoon onset over Kerala delayed: IMD

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Onset of Monsoon, ITCZ, etc.

Mains level: Factors that influence the onset of south-west monsoons, Indian Monsoon

  • The monsoon’s arrival over Kerala has been delayed to June 3, according to an update by the India Meteorological Department (IMD).
  • Private weather forecast agency, Skymet, however, said that the monsoon had arrived.
  • This was because two of the three criteria — as defined by the IMD — had been met.
  • Currently, IMD’s own data indicated that except for the OLR, the other criteria were met. Thus, there is an element of subjectivity in arrival.

What are those criterias defined by IMD?

  1. Rain-bearing westerlies being at a minimum depth and speed;
  2. At least 60% of the available 14 stations in Kerala and coastal Karnataka, reporting rainfall of 2.5 mm or more for two consecutive days after May 10;
  3. A certain degree of clouding, indicated by a parameter called ‘outgoing long wave radiation(OLR), being below 200 W/square meter.

What is meant by ‘Outgoing Long Wave Radiation’ (OLR)?

  • Outgoing Long-wave Radiation (OLR) is electromagnetic radiation of wavelengths from 3–100 μm emitted from Earth and its atmosphere out to space in the form of thermal radiation.
  • It is also referred to as up-welling long-wave radiation and terrestrial long-wave flux, among others.
  • The flux of energy transported by outgoing long-wave radiation is measured in W/m.
  • In the Earth’s climate system, long-wave radiation involves processes of absorption, scattering, and emissions from atmospheric gases, aerosols, clouds and the surface.
  • Over 99% of outgoing long-wave radiation has wavelengths between 4 μm and 100 μm, in the thermal infrared part of the electromagnetic spectrum.

Factors responsible for south-west monsoon formation:

  1. Intense heating of Tibetan plateau during summer months.
  2. Permanent high pressure cell in the South Indian Ocean (east to north-east of Madagascar in summer).

Factors that influence the onset of south-west monsoons:

  1. Above points +
  2. Subtropical Jet Stream (STJ).
  3. Tropical Easterly Jet (African Easterly Jet).
  4. Inter Tropical Convergence Zone.

Factors that influence the intensity of south-west monsoons:

  1. Strengths of Low pressure over Tibet and high pressure over southern Indian Ocean.
  2. Somali Jet (Findlater Jet).
  3. Somali Current (Findlater Current).
  4. Indian Ocean branch of Walker Cell.
  5. Indian Ocean Dipole.

Factors responsible for north-east monsoon formation:

  1. Formation and strengthening of high pressure cells over Tibetan plateau and Siberian Plateau in winter.
  2. Westward migration and subsequent weakening of high pressure cell in the Southern Indian Ocean.
  3. Migration of ITCZ to the south of India.

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Monsoon Updates

How Asian desert dust enhances Indian summer monsoon?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian Monsson : Onset and Withdrawal

Mains level: Determinants of Indian Monsoon

A new study has revealed how dust coming from the deserts in West, Central and East Asia plays an important role in the Indian Summer Monsoon.

Try this PYQ:

With reference to ‘Indian Ocean Dipole (IOD)’, sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?

  1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
  2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.

Select the correct Option using the code given below:

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

Why study dust?

  • Many studies have shown that the dust emission scheme is extremely sensitive to climate change.
  • Understanding these mechanisms and effects of dust will help us understand our monsoon systems in the face of global climate change.

Impact of dust on Indian Monsoon

  • Dust swarms from the desert when lifted by strong winds can absorb solar radiation and become hot.
  • This can cause heating of the atmosphere, change the air pressure, wind circulation patterns, influence moisture transport and increase precipitation and rainfall.
  • A strong monsoon can also transport air to West Asia and again pick up a lot of dust.
  • The researchers say this is a positive feedback loop.

Role of the Iranian plateau

  • Not just the dust from the Middle East, the Iranian Plateau also influences the Indian Summer Monsoon.
  • The hot air over the Iranian Plateau can heat the atmosphere over the plateau, strengthen the circulation over the deserts of the Arabian Peninsula and increase dust emission from the Middle East.
  • The researchers also explain how the Indian Summer Monsoon has a reverse effect and can increase the winds in West Asia to produce yet more dust.

Transported aerosols

  • Deserts across the globe play important roles in monsoons.
  • The dust aerosols from deserts in West China such as the Taklamakan desert and the Gobi Desert can be transported eastward to eastern China and can influence the East Asia summer monsoon.
  • And in the southwest United States, we have some small deserts that influence the North African monsoon.

Anthropogenic contributions

  • Some studies have found that the anthropogenic aerosols emitted from the Indian subcontinent can decrease summer monsoon precipitation.
  • However, some others found that absorbing aerosols such as dust can strengthen the monsoon circulation.

Minor components

  • Earlier it was believed that dust from deserts across the globe will have the same components.
  • But it was found that different deserts have different chemical compositions and this can influence the dust’s properties.
  • For example, dust from the Middle East has the more absorbing ability of solar radiation than dust from North Africa and this difference in absorbing ability might influence monsoon systems.

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Monsoon Updates

Mawsynram: Wettest place on Earth sees a decreasing trend in rainfall

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mawsynram

Mains level: Not Much

A recent study that looked at the rainfall pattern in the past 119 years found a decreasing trend at Cherrapunji and nearby areas.

Try this PYQ:

Q.“Climate is extreme, rainfall is scanty and the people used to be nomadic herders.” The above statement best describes which of the following regions?

(a) African Savannah

(b) Central Asian Steppe

(c) North American Prairie

(d) Siberian Tundra

Mawsynram

  • Mawsynram is a town in the East Khasi Hills district of Meghalaya state in northeastern India, 60.9 kilometres from Shillong.
  • Mawsynram receives the highest rainfall in India.
  • It is reportedly the wettest place on Earth, with an average annual rainfall of 11,872mm but that claim is disputed.
  • According to the Guinness Book of World Records, Mawsynram received 26,000 millimetres (1,000 in) of rainfall in 1985.

Why it rain highest in Mawsynram?

  • Because of the uneven relief of India due to the presence of a number of hill ranges, the monsoon is not able to shed its moisture evenly over India.
  • Windward sides receive more rainfall and leeward sides receive less rainfall.
  • Mawsynram lies in the funnel-shaped depression caused by the Khasi range in Meghalaya.
  • The Bay of Bengal branch of monsoons is trapped in it and causes heavy rainfall.

Decreasing rainfall trends

  • The research analysed daily rain gauge measurements during 1901–2019 and noted that the changes in the Indian Ocean temperature have a huge effect on the rainfall in the region.
  • There was a reduction in the vegetation area in northeast India in the past two decades, implying that human influence also plays an important role in the changing rainfall patterns.
  • The traditional way of cultivation known as Jhum cultivation or shifting cultivation is now decreased and being replaced by other methods.
  • Also, previous studies have noted there is sizable deforestation in the region.

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Monsoon Updates

[pib] National Monsoon Mission

Note4Students

From UPSC perspective, the following things are important :

Prelims level: National Monsoon Mission

Mains level: Determinants of Indian Monsoon

Under the National Monsoon Mission (NMM), Ministry of Earth Sciences has developed the state-of-the-art weather and climate prediction models, which are now in operational use.

Tap to read about the mechanism of Indian Monsoon System at:

The Southwest Monsoon Season (Jun – Sep) | Part 1

National Monsoon Mission (NMM)

  • Ministry of Earth Sciences (MoES) had launched NMM in 2012 with a vision to develop a state-of-the-art dynamical prediction system for monsoon rainfall on different time scales.
  • The responsibility of execution and coordination of this mission is vested to the Indian Institute of Tropical Meteorology (IITM), Pune.
  • Climate Forecast System (CFS) of USA has been identified as the basic modelling system for the above purpose, as it is one of the best among the currently available coupled models.

Targets of NMM

  • Development of a seamless prediction system using monsoon mission model, on different time scales, like Seasonal (for whole Monsoon season), extended-range (upto 4 weeks), short-range prediction (up-to 5days).
  • Initiate and coordinate the working partnership between Indian and foreign institutes to develop a system for prediction of extremes and climate applications
  • Develop and implement the system for climate applications having social impacts (such as agriculture, flood forecast, extreme events forecast, wind energy, etc.
  • Advanced data assimilation system for preparing high-quality data for model predictions.

Achievements of NMM during the last 3 years

  • Setting up of an advanced prediction system for Seasonal prediction; Extended range prediction and Very high-resolution Short-range prediction.
  • Commissioning of a Global Ensemble Forecast System (GEFS) for short and medium-range prediction at 12km.
  • The Cyclone track and intensity prediction has also shown a steady improvement over the last three years.
  • The operationalization of Monsoon Mission dynamical model (MMCFS) to prepare operational seasonal forecast of monsoon rainfall and temperatures during the hot and cold weather seasons over India.
  • Development of an algorithm to monitor and predict the Monsoon Intra-seasonal Oscillations (MISO) and Madden-Julian Oscillation (MJO) on the extended range.
  • Development of an index to predict the genesis and evolution of tropical cyclones and other cyclonic disturbances over the north Indian Ocean.

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Monsoon Updates

What are Rossby Waves?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian Monsoon, ENSO, Planetary Winds

Mains level: Determinants of Indian Monsoon

Droughts in India have historically been associated with El Nino, anomalous warming of the equatorial Pacific, but Indian scientists have found some relevance in Rossby Waves.

Q.The determinants of Indian Monsoon are no more limited to the Pacific and the Indian Ocean. Discuss.

El-Nino alone do not cause drought

  • The study says that nearly six out of 10 droughts, in non-El Nino years occurred during the Indian summer-monsoon season in the past century.
  • They may have been driven by atmospheric disturbances from the North Atlantic region.
  • In an El Niño year, abnormally warm equatorial Pacific waters pull moisture-laden clouds away from the subcontinent.
  • But the IISc Bangalore study shows that in non-El Nino years, these droughts are a consequence of a sudden and steep drop in rainfall in late August.

Then, how were droughts induced?

  • In an El Nino year, the rainfall deficit departure from a long-term average set in early around mid-June and progressively worsen.
  • Researchers tried to trace this drought back to a forcing agent or system that influences the behaviour over India.
  • They found, the winds that were prevalent in these non-El Niño drought years.

Another factor: The Rossby Waves

  • The researchers noted that winds in the upper atmosphere are interacting with a deep cyclonic circulation above the abnormally cold North Atlantic waters.
  • The resulting wave of air currents called a Rossby wave, curved down from the North Atlantic squeezed in by the Tibetan plateau and hits the subcontinent around mid-August.
  • This has a suppressing effect on rainfall and throws off the monsoon that was trying to recover from the June slump.

Now scratch your basics on Planetary Winds. “Go back to the NCERTs !”

What are Rossby Waves?

  • They are giant meanders in high-altitude winds that have a major influence on the weather.
  • They are influenced by the Coriolis force and pressure gradient.
  • The wave’s usual course is to go from west to east, but not towards the equator.

Points to be noted ……

  • The Indian Ocean and the Pacific Ocean seem to be at the forefront of all discussions surrounding Indian monsoon droughts.
  • Thus beyond looking at the Pacific Ocean it is important to consider other influences on the Indian monsoon from outside the tropics.
  • It is perhaps time to focus just as much on mid-latitude influences, which might aid in getting a better handle on enhanced predictability of monsoon variability.

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Monsoon Updates

Why has the Northeast Monsoon remained deficient this year?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Indian Monsson : Onset and Withdrawal

Mains level: El Nino and La Nina

Rainfall over the Southern peninsular region has been deficient so far due to prevailing La Nina conditions according to the India Meteorological Department (IMD).

Try this PYQ:

Q.La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino?

  1. La Nina is characterized by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean.
  2. El Nino has an adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

What is the Northeast monsoon?

  • India receives rainfall during two seasons.
  • About 75 per cent of the country’s annual rainfall is received from the Southwest monsoon between June and September.
  • The Northeast monsoon, on the other hand, occurs from October to December and is a comparatively small-scale monsoon, which is confined to the Southern peninsula.
  • After the complete withdrawal of the Southwest monsoon from the country takes place by mid-October, the wind pattern rapidly changes from the south-westerly to the north-easterly direction.
  • Also called the winter monsoon, the rainfall associated with the Northeast monsoon is important for almost entire South India.

Why it is important?

  • Tamil Nadu records about 48 per cent (447.4 mm) of its annual rainfall (943.7 mm) during these months, making it the key factor for undertaking agricultural activities and reservoir management in the state.
  • Some South Asian countries such as Maldives, Sri Lanka and Myanmar also record rainfall from October to December.

Why there are distortions?

  • The majority of districts in Tamil Nadu remain highly rain-deficient up this time.
  • The period after the Southwest monsoon season, from October to December, is the peak time for cyclonic activity in the North Indian Ocean region — covering the Arabian Sea and the Bay of Bengal.
  • The winds associated with the formation of low-pressure systems, depressions, or cyclones influence this monsoon, and therefore, the rainfall.
  • Officials at IMD have linked it to the prevailing La Niña conditions in the Pacific Ocean.

La Nina  link with the NE monsoon

  • While La Niña conditions enhance the rainfall associated with the Southwest monsoon, it has a negative impact on rainfall associated with the Northeast monsoon.
  • During La Niña years, the synoptic systems — low pressure or cyclones — formed in the Bay of Bengal remain significantly to the north of their normal position.
  • Besides, instead of moving westwards, these systems recurve. As they lie to the north of their normal position, not much rainfall occurs over southern regions like Tamil Nadu.

Back2Basics: El Nino and La Nina

  • While El Niño (Spanish for ‘little boy’), the more common expression, is the abnormal surface warming observed along the eastern and central regions of the Pacific Ocean (the region between Peru and Papua New Guinea).
  • The La Niña (Spanish for ‘little girl’) is an abnormal cooling of these surface waters.
  • Together, the El Niño and La Niña phenomena are termed as El Niño Southern Oscillation (ENSO).
  • These are large-scale ocean phenomena which influence the global weather — winds, temperature and rainfall. They have the ability to trigger extreme weather events like droughts, floods, hot and cold conditions, globally.
  • Each cycle can last anywhere between 9 to 12 months, at times extendable to 18 months — and re-occur after every three to five years.
  • Meteorologists record the sea surface temperatures for four different regions, known as Niño regions, along this equatorial belt.
  • Depending on the temperatures, they forecast either as an El Niño, an ENSO neutral phase, or a La Niña.

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Monsoon Updates

What is Global Warming Hiatus (GWH)?

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Mascerene High, Global Warming Hiatus (GWH)

Mains level: Impact of global warming on Indian Monsoon

A new study on variability in the Mascarene High (MH) in the Southern Indian Ocean during global warming hiatus (GWH) has revealed that the region experienced significantly increased sea surface temperature (SST) during this period (1998-2016).

Try this PYQ:

Q.With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? (CSP 2020)

  1. OMT is measured upto a depth of 26 degree Celsius isotherm which is 129 meters in the south-western Indian Ocean during January-March.
  2. OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.

Select the correct answer using the code given below:
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

What is Global Warming Hiatus (GWH)?

  • A global warming hiatus is referred to a global warming pause, or a global warming slowdown, which is a period of relatively little change in globally averaged surface temperatures.
  • The hiatus, however, can result in an increase in the SST.

What is Mascarene High (MH)?

  • The Mascarene High (MH) is a semi-permanent subtropical high-pressure zone in the South Indian Ocean.
  • It is also called the Indian Ocean subtropical high, which is a high-pressure area located between 20° to 35° South latitude and 40° to 90° East longitude.
  • It is a region from where the cross-equatorial winds blow to India.
  • It has been named after the Mascarene Islands, in the Indian Ocean east of Madagascar consisting of the islands belonging to Mauritius as well as the French Réunion Islands.
  • Apart from its large influence on African and Australian weather patterns, it also helps in driving the inter-hemispheric circulation between the Indian Ocean in the south and subcontinental landmass in the north.

Role of MH

  • The warming in SST due to global warming has resulted in a decrease in the pressure gradient between the MH and the Indian landmass.
  • This in turn suppressed the intensity of low-level cross-equatorial winds over the western Indian Ocean affecting the onset of the monsoon over the Indian subcontinent and rainfall over East Asia.

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Monsoon Updates

Boreal Summer Intra-Seasonal Oscillation (BSISO)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: BSISO

Mains level: Indian monsoon and its prediction

Researchers at the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad have reportedly found a way to better forecast the Boreal Summer Intra-Seasonal Oscillation (BSISO).

Try this PYQ:

Q.With reference to ‘Indian Ocean Dipole (IOD)’ sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? (CSP 2017)

  1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
  2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.

Select the correct answer using the code given below:

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

What is BSISO?

  • The BSISO of the Asian summer monsoon (ASM) is one of the most prominent sources of short-term climate variability in the global monsoon system.
  • It is the movement of convection (heat) from the Indian Ocean to the western Pacific Ocean roughly every 10-50 days during the monsoon (June-September).
  • Compared with the related Madden-Julian Oscillation (MJO) it is more complex in nature, with prominent northward propagation and variability extending much further from the equator.
  • It represents the monsoon’s ‘active’ and ‘break’ periods, in which weeks of heavy rainfall give way to brilliant sunshine before starting all over again.
  • The active phase also enhances monsoon winds and hence the surface waves.

Why predict BSISO behaviour?

  • Some phases of boreal summer intraseasonal oscillation or BSISO induce high wave activity in the north Indian Ocean and the Arabian Sea, the researchers claimed.
  • Wave forecast advisories based on the BSISO would be more useful for efficient coastal and marine management.
  • This finding has a great significance in developing seasonal and climate forecast service for waves and coastal erosion for India.

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Monsoon Updates

Bay of Bengal Boundary Layer Experiment (BoBBLE)

Note4Students

From UPSC perspective, the following things are important :

Prelims level: BoBBLE

Mains level: Indian monsoon and its prediction

A team from IISc Bengaluru and UK based researchers has created a blueprint for accurate prediction of monsoon, tropical cyclones and another weather-related forecast under the BoBBLE Experiment.

Aspirants must note:

1) BoBBLE is headed by which organizations?

2) Its purpose and application

What is BoBBLE?

  • The Bay of Bengal Boundary Layer Experiment or BoBBLE in short is a project funded by Union Ministry of Earth Sciences and the Natural Environment Research Council of UK.
  • BoBBLE tries to determine, quantify and model ocean-atmosphere interactions that drive variability in the South Asian monsoon.
  • The experiment created a blueprint for future weather system observational experiments for accurately forecasting monsoon rainfall.

Why need BoBBLE?

  • The Bay of Bengal (BoB) plays a fundamental role in controlling the weather systems that make up the South Asian summer monsoon system.
  • In particular, the southern BoB has cooler sea surface temperatures (SST) that influence ocean-atmosphere interaction and impact the monsoon.
  • Compared to the southeastern BoB, the southwestern BoB is cooler, more saline receives much less rain, and is influenced by the summer monsoon current (SMC).
  • To examine the impact of these features on the monsoon, the BoB Boundary Layer Experiment (BoBBLE) was undertaken.

BONUS:

1) How technology development in monsoon forecasting can benefit realizing the dream of doubling farmers income by 2022?

2) Discuss the role of Bay of Bengal in monsoon dynamics. (Hint: the link between the two lies in Indian Ocean Dipole (IOD))

How is the experiment carried out?

  • BoBBLE will deploy two ships, six ocean gliders and eight floats to collect an unprecedented range of oceanic and air-sea flux observations.
  • These will occupy locations in the southwest and southeast Bay, as well as tracing east-west and north-south paths between those locations, measuring ocean temperature, salinity and currents.

With inputs from http://www.walker.ac.uk/research/projects/bay-of-bengal-boundary-layer-experiment-bobble/

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Monsoon Updates

Explained: What new monsoon dates mean

Note4Students

From UPSC perspective, the following things are important :

Prelims level: Monsoon: Its onset and retreat

Mains level: Various factors causing uncertainty in monsoon predictions

 

The India Meteorological Department (IMD) had decided to revise the normal onset and withdrawal dates for the monsoon in some parts of the country from this year.

Onset of Monsoon

  • The four-month southwest monsoon season, which brings as much as 70 per cent of the country’s annual rainfall, officially begins on June 1, with the onset over Kerala, and ends on September 30.
  • It takes about a month and half after onset on the Kerala coast to cover the entire country; and about a month, beginning from the northwestern parts of the country on Sept. 1 to withdraw completely.
  • Although the June 1 date for the onset of the monsoon on the Kerala coast is unlikely to be changed, the dates for onset in many other parts of the country are expected to be revised.
  • Mumbai, for example, expects to start getting rain from June 10 the revision is likely to push this date back by a few days.
  • Effectively, the monsoon is now expected to have later arrival and withdrawal dates in most parts of the country.

Why was this revision needed?

  • The main reason for the revision in the normal dates is the changes in precipitation patterns that have been taking place over the last many years.
  • In the last 13 years, for example, only once has the onset over the Kerala coast happened on June 1.
  • While two or three days of earlier or later onset falls within the yearly variability in several years the onset happened five to seven days late.
  • Similarly, the commencement of withdrawal has happened in the first week of September only twice during this period, and last year, the withdrawal started as late as October 9 — and was completed in around just a week.

Recent peculiarity with the exam

  • One of the significant changes being noticed is that rainfall is getting increasingly concentrated within a narrow band of days within the monsoon season.
  • So, there are extremely wet days followed by prolonged periods of dry days.
  • IMD data show that over several previous years, nearly 95 per cent of monsoon precipitation in 22 major cities of the country had happened over a period of just three to 27 days.
  • Delhi, for example, had received almost 95 per cent of its monsoon rainfall over just 99 hours. And half of Mumbai’s monsoon rain had fallen over just 134 hours, or five and a half days, on average.

Regional variations

  • Patterns of regional variations in rainfall are also changing
  • Areas that have traditionally received plenty of rainfall are often remaining dry, while places that are not expected to get a lot of monsoon rain have sometimes been getting flooded.
  • Climate change could be one of the factors driving these changes, but there could be other reasons as well.

What will be the impact of IMD’s move?

For Farmers

  • The revisions are meant to reflect the changes in precipitation patterns in recent years.
  • New dates will likely nudge farmers in some parts of the country to make slight adjustments in the time of sowing their crops.
  • It would definitely have an impact on our agriculture practices — when to start sowing, when to harvest.
  • So, even if there is a delay in the arrival of monsoon by three to four days over a region, it would not matter much if there is a fairly good rainfall distribution thereafter.
  • The change in dates would affect water management practices as well.

For Industries

  • The planning that goes to beat the heat — several cities execute heat action plans — just ahead of the monsoon would have to factor in the need to be prepared for longer periods of heat.
  • Rajeevan said many other activities including industrial operations, the power sector, or those using cooling systems, would also need to change their behaviour.
  • The power grid can, for example, have more realistic planning for peak periods of electricity consumption in certain months.

Way Forward

  • The changed dates are expected to be announced in April, when the IMD makes its first forecast for the monsoon.
  • Agro-meteorologists, however, agree that more than the onset, it is the information about the spatio-temporal distribution of rainfall that will be more helpful for farmers.
  • Ultimately, the change in normal dates of the onset and withdrawal of the monsoon would help people understand when to expect rains, and to plan their activities accordingly.

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How does El Nino affect Indian Monsoon? A Comprehensive Explainer

As many reports speculated that El Nino is the main cause of the worsening Indian Monsoon and has played badly with Indian agriculture, we thought that we should take a big picture of El Nino and it’s scope in India.


 

  • The Monsoon is basically a result of the flow of moisture laden winds because of the variation of temperature across the Indian Ocean.
  • There are a number of climatic phenomena which affect it namely the El nino, La nina etc.
  • We will look at their origin, impact and way forward.

Now, let’s take a overview and develop our understanding. 

What happens in a Normal Year?

  • Peru Current = Humboldt Current = Cold Current.
  • During normal year 2 things are very strong – Cold Peru Current and Trade Winds.
  • As a result, cold water is dragged from Peru towards Australia.

What would be the result of this exchange?

  • Warm water region around Australia is called Western Pacific Pool (WPP).
  • WPP = low pressure = warm air ascends = cloud formation = rain over North Australia
  • This air also joins walker cell and begins descending near Peru.
  • Descending air = anti-cyclonic condition = high pressure = stability = no cloud/rain = Drought in Atacama Desert.

(Simply, Walker cell is the result of a difference in surface pressure and temperature over the western and eastern tropical Pacific Ocean)

What happens below the water from Peru to Australia ?

At Peru coast, cold water upwelling brings nutrient to surface + more lunch for Plankton + more fishes = Peru fishermen gets happy.

What happens above the water from Australia towards Peru?

Warm water + low atmospheric pressure = good rainfall over Australia & Indonesia.

What happens in La Nina Year?

Same things as in a “normal” year, but 2 things become even “stronger” –

  • Cold Peru Current
  • Trade Winds

What’s the Result?

  • Too many fishes at Peru coast = oversupply of fishes = prices become dirt cheap.
  • Too much rain / flood over Australia and Indonesia.

This is what happens in normal and La Nino year, Let’s back to El Nino!


 


 

What happens in an El Nino year?

Two things become weak.

  • Cold Peru Current
  • Trade Winds
  • As result, cold water is not dragged from Peru to Australia.
  • But reverse happens, warm water is dragged from Australia towards Peru.
  • Consequently, warm water + low pressure condition develops in the Eastern Pacific (Peru) and Cold condition + high pressure in Western Pacific (Australia).

What will happen if pressure is inversely related with amount of rainfall ?

  • Rain & Floods at Peru, Atacama and even Southern USA
  • Drought at Northern Australia, Indonesia- even bushfires.
  • Storms and Hurricanes in East Pacific.
  • Coral bleaching (high temperature coral dies)

But, what is the El Nino?

  • El Nino is an Oceanic and Atmospheric phenomenon that leads to unusual warming of water in the Peru coast, occurs every 3-5 years.
  • Consequently, warm water + low pressure condition develops in the Eastern Pacific (Peru) and Cold condition + high pressure in Western Pacific (Australia).
  • Since Pressure is inversely related with amount of rainfall, El Nino causes drought situation in Australia and South East Asia.
  • It weakens the trade winds and changes in Southern Oscillation, thereby affects the rainfall pattern across the world.

el-nino-phenomenon


What is Southern Oscillation?

  • Alternating of (tropical) sea level pressure between the eastern and western hemispheres.
  • We can measure Southern Oscillation by observing the pressure difference between Tahiti (French Polynesia) and Darwin (Australia).

How does El Nino affect Indian Monsoon?

  • El Nino-Southern Oscillation (ENSO) water circulation happens between Australia and Peru.
  • But, the wind movement is part of larger atmospheric circulation hence affects the rainfall over India. But, how?
  • We have learned that During normal year, the warm water moves towards Australia, this pool of warm water is called Western Pacific Pool (WPP).

So, from WPP air rises above and moves towards two walker cells –

  • Towards Peru coast = this affects rainfall in South America.
  • Towards Mascarene High Pressure zone near East Africa. So, this affect Indian monsoon.

Why should India worry about?

  • Drought condition decreases the agriculture output, leads to food inflation.
  • Declined supply of cotton, oilseeds and sugarcane negatively affects the textile, edible oil and food processing industries respectively.

What is the way forward?

Let’s discuss first Near-term Solutions?

  • Government must expand farm insurance cover and advice financial institutions to settle crop insurance claims in the drought-hit areas without delay. Otherwise, it results in farmer suicides (e.g. Maharashtra farmers’ suicide ).
  • High quality seeds of alternative crops must be distributed among farmers in drought-affected areas.
  • Need of realistic assessment of ground level situation in order to estimate the shortfall of oilseeds and pulses and help traders with market intelligence.
  • Scrapping the APMC Act and allowing free flow of agricultural goods among the states.
  • This would help bridge the mismatch of demand and supply of goods, which is the underlying factor contributing inflation.

What should be the Long-term Solutions?

  • Developing drought free crop varieties and distributing its subsidized seeds to the farmers. It is a part of National Action plan on climate change in Agriculture.
  • Using low water use technologies like drip and sprinkler irrigation.
  • The MSP regime in India has to provide more remuneration for less water consuming crops.
  • Strengthening community watershed management and development by protecting and conserving local water sources like ponds, lakes etc.
  • Developing early warning systems and alerting the farmers much in advance like recently launched Kisan SMS scheme.

Do you find more solutions or any way out? then, Let us know!


 

Published with inputs from Arun
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