EL NINO

Subject : Geography

Context : A new study carried out by researchers of the Indian Institute of Science’s (IISc) Centre for Atmospheric and Oceanic Sciences (CAOS) has found that El Niño alone is not be blamed for droughts that in the Indian subcontinent.

Concept :

• El Nino refers to the large-scale ocean-atmosphere climate interaction linked to periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. It is associated with high pressure in the western Pacific. El Nino adversely impacts the Indian monsoons and hence, agriculture in India.

El Nino impacts on India:

• In a normal monsoon year (without El Nino), the pressure distribution is as follows:
• The coast of Peru in South America has a higher pressure than the region near northern Australia and South East Asia.
• The Indian Ocean is warmer than the adjoining oceans and so, has relatively lower pressure. Hence, moisture-laden winds move from near the western Pacific to the Indian Ocean.
• The pressure on the landmass of India is lower than on the Indian Ocean, and so, the moisture-laden winds move further from the ocean to the lands.
• If this normal pressure distribution is affected for some reason, the monsoons are affected.
• El Nino means lesser than average rains for India. Indian agriculture is heavily dependent on the monsoons and because of this, lesser rainfall during the monsoons generally translates to below-average crop yields.

What happens because of El Nino?

• The cool surface water off the Peruvian coast goes warm because of El Nino. When the water is warm, the normal trade winds get lost or reverse their direction.
• Hence, the flow of moisture-laden winds is directed towards the coast of Peru from the western Pacific (the region near northern Australia and South East Asia).
• This causes heavy rains in Peru during the El Nino years robbing the Indian subcontinent of its normal monsoon rains. The larger the temperature and pressure difference, the larger the rainfall shortage in India.