Introduction:-

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 Indian ocean dipole, El nino, La nina, Equatorial Indian Ocean Oscillation (EQUINOO) etc. These phenomena affect the temperature distribution over the oceans and thus affecting the direction and intensity of flow of the moisture laden winds.

There have been recent reports that El Nino may disturb the Indian Monsoon and play badly with Indian agriculture. Monsoon is a familiar though a little known climatic phenomenon. In India, from agriculture to economic policies to disaster management, a lot depends on the monsosoon.

El Nino:-

El Nino and La Nina are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central.

La Nina is sometimes referred to as the cold phase of ENSO and El Nino as the warm phase of ENSO. These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate, including India.

For a normal monsoon season, the pressure distribution is as such:

• The Peruvian coast has relatively high pressure than the areas near north Australia and South-East Asia.
• The Indian Ocean is slightly warmer than the adjoining oceans(west Pacific) and thus the pressure is low relatively due to the warm seas. This is why the moisture laden winds move from near the west pacific to the Indian Ocean and from there on to the lands.
• The pressure on heated Indian land is much lower than that on the Indian Ocean.

This facilitates the movement of monsoon winds from the sea to the Indian land without any significant diversion.

But if for some reason this normal distribution is affected, then there is a change in the way trade winds (or monsoon winds) would blow.

For a El Nino Monsoon, the following is the advance of events:-

• Off the coast of Peru (read in Eastern Pacific and Central Pacific), there is normally cool surface water because of the cold Peruvian current. But El Niño makes it go warm.
• When the water becomes warm, the trade winds, which otherwise flow from East to west, either reverse their direction or get lost.
• Due to this warm water, the air gets up and surface air pressure above Eastern Pacific gets down. On the other hand, the waters cool off in western pacific and off Asia. This leads to rise in surface pressure over the Indian Ocean, Indonesia, and Australia.
• Now as the pressure over the Peruvian coast reduces because of the warm sea water, the flow of moisture laden winds is directed to the Peruvian coasts from the western pacific (the areas near North Australia and South-east Asia).
• Hence, the moisture laden winds that should have moved towards the Indian coast now move towards the Peruvian coast.
• The warm water causes lots of clouds getting formed in that area, causing heavy rains in Peruvian desert during El Niño years.
• This robs the Indian subcontinent of its share in the Monsoon rains. The greater the temperature and pressure difference, the greater would be the shortage in the rainfall in India.

Impact of El Nino :- 

• Normal or High rainfall in Eastern/Central Pacific.
• Drought or scant rainfall in western pacific/Asia.
• In India, almost 50% of the area under cultivation is rain-fed. Indian agriculture is thus heavily dependent on the climate of India: a favorable southwest summer monsoon is critical in securing water for irrigating Indian crops. So, a significant reduction in total rain fall results in a drought like situation.
  Drought in India has resulted in tens of millions of deaths over the course of the 18th, 19th, and 20th centuries.
• In some parts of India, the failure of the monsoons result in water shortages, resulting in below-average crop yields.
• This is particularly true of major drought-prone regions such as southern and eastern Maharashtra, northern Karnataka, Andhra Pradesh, Odisha, Gujarat, and Rajasthan.
• A lot of Farmers suicide because they are not be able to repay the loan they had taken for growing the crop.
• A tighter monetary policy to tame food inflation may affect the economic growth rate of the nation. Besides, lower agricultural production already lower the GDP of the nation dealing a double blow
• Weak monsoons also result in lesser power generation from hydro power dams thus leading to even lesser electricity for irrigation purposes. This further reduces the crop yield.