El Nino, La-Nina- effects on Indian Agriculture

Topic

El Nino- effects on Indian agriculture, La-Nina

Normal year

  • Peru Current = Humboldt Current = Cold Current.
  • During normal year two things are “STRONG”
    • Cold Peru Current
    • Trade Winds
  • As a result, cold water is dragged from Peru towards Australia. (observe following image)

Results in:

  • In above image, the red (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.
below water Moving of water from Peru to Australia. @Peru cold water upwelling brings nutrient to surface=more lunch for Plankton= more fishes = good for Peru fishermen.
above water Moving of air from Australia towards Peru. Warm water + low atmospheric pressure = good rainfall over Australia & Indonesia.
  • Descending air = anti-cyclonic condition = high pressure = stability = no cloud/rain = Drought in Atacama Desert.

So in a way two cycles are created

What happens in La-Nina year?

Same things as in a “normal” year, but those two things become even “stronger”

  1. Cold Peru Current
  2. Trade Winds

Therefore,  There are  abundant  fishes in Peru coast, oversupply of fishes= prices become dirt cheap and too much rain / flood over Australia and Indonesia.

 What happens in El-nino year?

  • two things become “WEAK”
    1. Cold Peru Current
    2. 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).

Since Pressure is inversely related with amount of rainfall, the results are following

  1. Rain & Floods @Peru, Atacama and even Southern USA
  2. Drought @Northern Australia, Indonesia- even bushfires.
  3. Storms and Hurricanes in East Pacific.
  4. Coral bleaching (high temperature coral dies)
  5. El Nino decreases earth’s rotation rate decreases Coriolis force and increases length of day. (La Nina creates opposite). How? Because El Nino changes the wind pattern, hence Earth needs change speed to conserve its angular momentum of Earth-Atmospheric system.

What is El-nino?

  • Warming of Pacific Ocean
  • Near Western coast of Peru and Ecuador.
  • Occurs @every 3-4 years; [In theory, it should occur @every 12 years].
  • Its impact usually lasts for 9-12-18-24 months.
  • 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 measure Southern Oscillation by observing the pressure difference between

  1. Tahiti (French Polynesia) and
  2. Darwin (Australia).

 Impact of Southern Oscillation (SO)?

Low Index High SO
·         Smaller pressure difference between (tropical) oceans

·         of Eastern vs. Western Hemisphere

Higher pressure difference
associated with El Nino hence the name ENSO = El Nino-Sothern Oscillation La Nina
Weak trade winds Strong trade winds
poor monsoon good monsoon

 

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 learned that during normal year, the warm water moves towards Australia, this pool of warm water is called Western Pacific Pool (WPP). From WPP air rises above and moves towards two walker cells

  1. Towards Peru coast = this affects rainfall in South America.
  2. Towards Mascarene High Pressure zone near East Africa. = This affect Indian monsoon.
DURING NORMAL YEAR DURING EL NINO YEAR
·         strong WPP

·         strong trade winds

·         strong Mascarene High

·         Strong push for moisture laden winds towards India

·         good rain

·         weak WPP

·         weak trade winds

·         weakening of winds flowing towards Mascarene high

·         weak push to Monsoon winds towards India

·         Less rainfall / weak monsoon.

During La Nina years, this push is even stronger = heavy rain and floods. ·         El Nino caused severe drought in India (2009-10). Sugar price were highest in 30 year history.
El Nino= Little  boy in Spanish. Hence its opposite is called

·         La Nina (little girl)

·         El Vejo= old man, but La Nina more popular term nowadays.

·         Similar drought situation in Australia, Southeast Asia and Africa. (And floods in Brazil and USA Midwest.)

·         Such condition prevails for 9-24 months.

 

El-nino and India

  • Poor monsoon / drought like condition = commodities prices will rise especially sugar, pulses and edible oil. Government needs to stock them up, put restriction on exports, before black marketers start hoarding.
  • Farmers need to device alternate farming strategy, change the seeds and irrigation strategy for the drought like situation.

 

El-nino from economic survey

What is El-Nino?

  1. El Niño effect occurs when surface temperatures in the Pacific Ocean continuously rise above average for several months, which in turn adversely affects weather in many parts of the world.
  2. El Nino occurs every 3-5 years.
  3. South-west (SW) monsoon (from June to September) accounts for ~75% rainfall. Any shortage here.
  4. El Nino often begins to form during June-August, and typically lasts 9-12 months.

El Nino’s negative impact

  1. Rainfed regions of central, south, and north-west India
  2. Maharashtra, Gujarat, Rajasthan, Karnataka, Jharkhand, and Bihar.
  3. Rice, soybean, cotton, maize, jowar, groundnut, and sugarcane will be affected.
  4. Kharif pulses and oilseed

 

The El-nino effect and agriculture in India.

El Nino is a climatic phenomenon which impacts the western coast of South America, Australia, Indonesia and the monsoon regions of South Asia. It lasts for a year. A strong El Nino usually leads to drought-like conditions in the affected areas. There is no fixed pattern as to when it occurs, but it has a periodicity of eight to ten years. But its frequency is increasing as a result of global warming. The year 2014 is supposed to be an El Nino year.

The trade winds over the Pacific Ocean create a Warm Pacific Pool. This acts as a low pressure area over the ocean and a high pressure in the upper Troposphere. This high pressure has a sinking arm at the Mascarene High near Madagascar. This creates a high pressure over Mascarene, which propels the South-West Monsoon winds giving rain to India. In El Nino years, there is a high Sea Surface temperature which prevents the formation of Warm Pacific Pool and subsequently weakens the South-West Monsoon winds blowing towards India. This leads to poor rainfall in India.

India is an agrarian country; it contributes to sixteen percent of India’s Gross Domestic Product (GDP) and employs more than sixty percent of the working population. But, agriculture in India is largely rainfed. that is, it is monsoon dependent. The erratic nature of Indian monsoon leads to the vagaries in the agricultural productivity. In order to make Indian agriculture monsoon-proof, irrigation is required. Even after undertaking large scale irrigation projects, only thirty percent of India’s land has irrigation. Moreover, India cannot have all its agricultural land under irrigation and fifty million hectares out of one hundred forty-five million hectares will always be dependent on monsoon. Hence, poor rainfalls affect agriculture and El Nino years inevitably lead to poor agricultural productivity.

El Nino is linked to drought, which is an agricultural condition where prolonged water shortages lead to crop failure. But every El Nino year does not lead to drought, for example in the year 2002. The drought prone regions of India include areas with rainfall less than 60 cm of rain like the plateau of peninsular India like Deccan plateau, the desert areas of Thar and Saurashtra in Western India and the upland regions of Tamil Nadu. These regions are also poor regions and droughts affect the people much more than people of other regions.

The main consequence of El Nino is poor productivity which affects the poor farmers of peninsular India. Since majority of population is employed in agriculture, the effects of poor productivity are far reaching. The poor productivity leads to increased incidence of poverty and famine. Even the milch animals go hungry and it leads to poor production of milk. Poor productivity, which causes shortage of food, also leads to high food inflation throughout the country. High food inflation affects the poor disproportionately. The poor population, which has to shell more money for food. have less income to spend on other dietary needs like proteins. In order to curb inflation, RBI increases the interest rates which affects the common man also. Thus the effects of El Nino are not just confined to farmers but the whole of India.

As India Meteorological Department (IMD) has predicted the occurrence of El Nino in 2014, the government should take necessary steps to offset its effects. Government should promote the production of coarse grains. Coarse grains are able to meet all the dietary requirements of the people while at the same time require less water and are drought resistant. The Minimum Support Price of these grains should be made attractive to promote its production while that of rice and sugarcane, which are water intensive, should be reduced. The Public Distribution System for these grains should also be upgraded. There should be sale of seeds of crops which use less water. Government should make use of drought funds in case of serious drought and provide extra days of NREGA in such drought affected areas. It should release the stock of stored grains so that the food inflation does not rise unexpectedly.

We cannot control the weather phenomenon. The occurrence of El Nino is beyond our control. But we can take steps to minimize its effects to make sure that the poor population of the country doesn’t go hungry.

 

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