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

Any doubts?


  1. mahesh sahu

    thank you sir..

  2. Pravin Kumar

    excellent

  3. Nagesh S

    Excellent

  4. joe george

    thank you. that was a good explanation

  5. Kshitij Dubey

    Why India sign indus water treaty

    1. Er S

      follow the forum. this is a story on El Nino

  6. शक्ति सहाय

    thnx for hindi explanation.. nice initiative

  7. vasista

    excellant

  8. Prasad Datar

    very nicely explain
    thanks

  9. deepak rathor

    Cud u pl explain reason for mascarene high pressure?

    1. inder inkhia

      the lw pressure air of tibetian plateu and australian east coast , ascend and it decend at mascarene basin near madagascar island , where high pressure take place bcz of descend of air ,,,

El Nino is weaker than anticipated, says IMD

Note4students:

Mains Paper 1: Geography | Salient features of world’s physical geography

From UPSC perspective following things are important:

Prelims level: El Nino, La Nino and IOD concepts.

Mains level: These kind of phenomenons are important for the static part of the syllabus. Expect a direct question
if already not asked


News:

  1. What: The India Meteorological Department(IMD) is expecting better this year
  2. Why: Because El Nino would be much weaker than anticipated
  3. New monsoon forecast system: IMD has shifted to a new monsoon forecast system, called a dynamical model that works by supercomputers simulating the weather and extrapolating it(i.e. Deducing the weather by assuming that existing trends will continue)

What is El Nino?

  1. The El Nino is characterised by surface waters of the equatorial Pacific warming up by more than half a degree
  2. It is known to negativey affect monsoon rain every six out of 10 years
  3. A positive Indian Ocean Dipole (IOD) is said to buffer the impact of El Nino and contribute to better rains
  4. The Indian Ocean Dipole (IOD) is also known as the Indian Niño. IOD is an irregular oscillation of sea-surface
    temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the
    eastern part of the ocean
  5. The IOD is a swing in surface temperatures that turns the western Indian Ocean alternately warmer and then
    colder than the eastern part of the ocean

India got 3% less rain than normal: IMD

  1. IMD: India has ended up with 3% less rain than normal during the monsoon months of June to September
  2. This is the first time since 2011 that the IMD was not able to forecast the overall ‘sign’ of the monsoon
  3. It expected heavy rain but ended up with less than normal
  4. In 2014 and 2015, it could not anticipate the severity of the droughts but had indicated that monsoon would be below normal
  5. In 2011, the IMD said India would get below normal (95% of the average) rain, but the country ended up with 2% more rain than normal

What is El-Nino?

El_Nino


  1. Definition: El Nino is defined by prolonged warming in the Pacific Ocean sea surface temperatures when compared with the average value
  2. The U.S NOAA definition: a 3-month average warming of at least 0.5 °C (0.9 °F) in a specific area of the east-central tropical Pacific Ocean
  3. Ocean water: It is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific, including off the Pacific coast of South America
  4. Pressure: El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific.
  5. Why called El-Nino? In Spanish, the capitalized term “El Nino” refers to the Child Jesus, so named because the pool of warm water in the Pacific near South America is often at its warmest around Christmas
  6. Teleconnections: El Nino can significantly influence weather patterns, ocean conditions, and marine fisheries across large portions of the globe for an extended period of time

Learn about El Niño–Southern Oscillation (ENSO)

  1. What? a naturally occurring phenomenon that involves fluctuating ocean temperatures in the equatorial Pacific.
  2. It is irregularly periodic.
  3. The warmer waters essentially oscillate back and forth across the Pacific, much like water in a bath tub
  4. Fluctuates between two states: warmer than normal central and eastern equatorial Pacific SSTs (El Niño) and cooler than normal central and eastern equatorial Pacific SSTs (La Niña)
  5. Sea surface temperatures (SSTs): often used to identify this oscillation
  6. For North America and much of the globe, the phenomenon is known as a dominant force causing variations in regional climate patterns.
  7. Walker circulation: The two phases relate to the Walker circulation, discovered by Gilbert Walker during the early twentieth century

Monsoon to be normal: IMD

  1. The India Meteorological Department (IMD) said the monsoon will be normal this year
  2. It has gone back on its earlier forecast of above normal monsoon
  3. Why? Due to delay in La Nina weather pattern
  4. Background: India has been hit by drought in the last two years, with the last monsoon being affected by El Nino
  5. However, it was expected that this year there would be a gradual transition to La Nina phenomenon, which would have boosted monsoon and given excess rain in September

Discuss: Discuss the significance of the normal monsoon rains on Indian economy. How good rains should be used to recharge groundwater through policy means?

Australia signals end of El Nino

  1. Context: Australia’s current climate model suggest that La Nina will begin in second half of monsoon
  2. La Nina: Reverse condition of El Nino
  3. El Nino: A warm current replaces cold current in tropical pacific region and affect the Indian monsoon
  4. La Nina will bring heavy rains over India
  5. Effects: Good for Kharif crops, the area under crops is expected to increase

Cyclonic storm over Bay of Bengal to intensify: IMD

  1. Context: Season’s first cyclone will be brought by cyclonic depression form in Bay of Bengal
  2. Effect: Will bring rain fall in Kerala, Chennai and Andhra Pradesh
  3. Conditions are favourable for advance southwest monsoon in some parts of Bay of Bengal, entire south Andaman Sea and Nicobar Islands
  4. The forecast of delayed monsoon in Kerala remains same

Remnants of El Nino holding up monsoon- II

  1. Signs of Monsoon: Raining over Andman with Cyclones in month of May
  2. But raining over Andman is decreasing because they are not sufficiently fuelled by cross equatorial flows
  3. No cyclones have been seen seen yet
  4. Prediction: Lag in seasonal transition, pre monsoon rains over Tamil Nadu and Kerala around 1 June
  5. Earlier: IMD predicted that there would be rains early than usual and above normal level and 106 % of 89 cm

Remnants of El Nino holding up monsoon

  1. Context: Monsoon may be delayed due to effects of El Nino
  2. El-Nino effect: This time the rain bearing winds doesn’t begin to draw across equator
  3. Therefore, Cross Equatorial flows haven’t developed

What caused the monster El Nino in 2015?

  1. Context: New study gives the reason for EL Nino 2015
  2. Reason: Presence of warm water current due to effect of El Nino of previous year (2014)
  3. El Nino: A warm ocean current which replaces cold Peru Current into warm current
  4. It gives rise to heavy precipitation in Peru coast while drought and less rainfall in eastern pacific region & affects monsoon badly

India to see a hotter-than-normal summer this year

  1. News: IMD has predicted that the above-normal heat wave conditions are very likely over central and northwest India during the summer
  2. The strong El Nino conditions in the Pacific are now on the decline
  3. For this season, IMD will provide extended range forecasts of heat wave conditions over the country every five days for the next 15 days
  4. Fact: 2015 was the third hottest year since 1901 and it was the third warmest year ever recorded since 1901

Experts unsure if El Nino will fade away

  1. News: Meteorologists expect the monsoon in 2016 to be normal but are unclear if El Nino will completely fade away during the crucial monsoon months
  2. About: El Nino refers to an anomalous heating up of the waters in the central-eastern regions of the equatorial Pacific
  3. This implies a consistent, average rise in temperature of 0.5 degree Celsius above normal
  4. Relevance: Historically that translates to the monsoon drying up over India 6 in 10 years
  5. About La Nina: when waters in the same regions dip at least 0.5 degree Celsius and generally considered favourable for the monsoon, is only expected to set in after Sept
  6. Relevance: 2015 was only the fourth time in a 100-yr span that El Nino-like conditions raged on for 2 consecutive yrs

El-Nino is receding

  1. Context: World Meteorological Organization (WMO) said El Niño has passed its peak and is in retreat
  2. Relief: Should bring relief for policy planners in India after two consecutive years of drought
  3. One of the most powerful: We have just witnessed one of the most powerful ever El Niño events
  4. Effects: Caused extreme weather in countries on all continents and helped fuel record global heat in 2015
  5. But not a time to celebrate: In meteorological terms El Niño is now in decline but we cannot lower our guard as it is still quite strong
  6. Future impact: in humanitarian and economic terms, its impacts will continue for many months to come
  7. Effect on India: A normal monsoon would help improve India’s macroeconomic prospects and boost rural demand
  8. Rural distress: A challenge for India is rural distress, triggered by a combination of consecutive droughts and a collapse of global commodity prices

What’s the fuss about El Niño?

 

  1. The El Niño is a weather phenomenon resulting in warmer than expected ocean temperatures in the central and eastern parts of the tropical belt of the Pacific Ocean.
  2. The effects of El Niño include reversal of wind patterns across the Pacific, drought in Australasia, and unseasonal heavy rain in South America.
  3. Indian Ocean Dipole is warmer sea temperatures in the western Indian Ocean and a cooler eastern Indian Ocean.
  4. It kept ocean temperatures high in the south Bay of Bengal resulting in strong weather systems in the South Andaman Sea.

El Nino may have only a minor impact

  1. Contrary to an 8% average decline in agri output in previous El Nino years, this projected El Nino year will reduce output only by ~4.5%.
  2. Cotton will not be much impacted because of an increase in area under cultivation and long sowing periods.
  3. Majority of sugarcane is grown in irrigated areas which insulate it from El Nino effect.


:( We are working on most probable questions. Do check back this section.







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