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.
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
