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. El Niño has an inverse relationship with monsoons, which means rainfall is usually subdued during such a year. This results in lower sowing and thus lower crop yields, thereby impacting farm incomes. India last witnessed the El Niño effect in 2018.
In a normal monsoon year (without El Nino), 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. This normal pressure distribution is affected in case of El Nino and hence, the monsoons are affected.
In El Nino years, the cool surface water off the Peruvian coast goes warm. 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.
Analysts say that rainfall deficit is a major factor that catalyses rural slowdown. Hence, there is a need to stress on three dimensions of rainfall – timing, total quantity, and distribution. Contingency plan at the district level should be in place; Seeds of late sowing variety should be available if the arrival of rainfall gets delayed; government should initiate water conservation and management, and closely watch the monsoon while maintaining water bodies; policymakers should have safeguards against too much dependence on rainfall to minimize the El Niño impact.