Why El Nino might lead to India getting less rains this year

The signs are not very positive. There are high chances that El Niño conditions will develop late summer this year. For the third month in a row, the US government weather agencies have said that this natural phenomenon will develop around July-August this year. An El Niño usually results in poor monsoon rains over India. This means prolonged heat waves, poor crop production and water shortage, among other problems. The US weather agencies have said there's a possibility of an El Nino forming in late summer this year... The US agencies, under the National Oceanic and Atmospheric Administration (NOAA), give monthly updates on conditions prevailing in the Pacific. The March update was released last week. It indicates that the probability for an El Niño happening is 48 per cent in July. It rises to 56 per cent by August. Signs for an El Niño has persisted for the third month in a row. The US forecast is an average of many weather models. This means the signs are strong. Next month’s forecast will be crucial as it will consider the conditions over the Pacific in spring when temperatures change with the season. What is El Niño? El Niño is a weather phenomenon that takes place in the Pacific Ocean. Picture the Pacific on the globe. It is the biggest ocean in the world. To the east is South America and to the West are Indonesia and Australia. Trade winds blow on the Equatorial region of the ocean. These winds were used in the olden times to navigate ships. These normally blow from east to west. When they blow over the surface of the Pacific, they push surface warm water towards the west, that is Indonesia and Australia. As a result, western part of the Pacific becomes warmer. There is more evaporation and therefore, more rainfall. This is the scenario when there is no La Niña or El Niño. During El Nino, trade winds get disrupted, for various reasons. Instead of moving west, they start moving towards the east, taking warm water there. This results in more rainfall in the central and eastern Equatorial Pacific. This disruption in the normal rainfall pattern brings about changes in the wind patterns, affecting weather across the globe. Pacific is a huge area, so occurrences in the Pacific have ramifications across the world. La Nina is the opposite. During La Nina, trade winds strengthen, blowing at a higher pace than usual. So, there is more rainfall in Indonesia and Australia than usual. This also has implications on weather across the world. How does El Nino impact monsoon rainfall in India? This has been a subject of research for long. The current knowledge is this: Trade winds move from east to west. There is more rainfall close to Indonesia. So trade winds move further west, along with moisture. To the west of this region is the Bay of Bengal and the Indian Ocean. Usually, it brings moisture which helps the Indian monsoon. During El Nino, this area becomes dry because of the shift in rainfall from the west of the Pacific towards the central and eastern parts. At this time, trade winds also blow in the opposite direction. Also, there is evidence of subsidence. This means that dry winds sink into the Bay of Bengal and the Indian Peninsular region, which also impedes monsoon rainfall. Will El Nino impact the common man? Usually, during El Nino years, monsoon rainfall in India is less than normal. It has implications on agriculture. Much of Indian agriculture continues to depend on monsoon. Even in states like Punjab and Haryana, and in western Uttar Pradesh, where irrigation facilities exist, prolonged dry periods lead to water stress for the crop. Since the implication is on agriculture, by extension it has implication on the country’s GDP as well. It also impacts water availability. Monsoon recharges our water storage systems. Less monsoon rainfall means people will have less access to water. One must look out for that. Does summer monsoon in India always get adversely affected during the El Nino years? That is the case usually, but there are exceptional cases. If one looks at the last 10 El Nino years —from 1991 to 2018, which was the last El Nino year — monsoon was adversely affected six or seven times. In 1991, monsoon was partially affected. In 1994 and 2006, El Nino set in very late, around September, which is the last month of monsoon season in India. The usual example when a strong El Nino did not impact monsoon is 1997. The year witnessed one of the strongest El Ninos in recent history. So, it is perceived that there is no one-to-one relationship of El Nino with monsoon in India. There are other factors as well, such as the Indian Ocean Dipole and the Madden-Julian Oscillation. These have a good effect on monsoon rainfall when in the right phase. The Eurasian snow cover also has an impact on monsoon rainfall. What El Nino does is that it subdues the largescale positive factors for monsoon in India, but there could be other factors that offset the impact of El Nino. When will we know for sure that El Nino is coming this year? This is only March. Projections by weather models have considered the conditions that existed in February. We will get a better idea about whether El Nino is forming this year or not by April or May. This will be the time when spring season would have set in fully. We have to take into account what the forecasts are saying because we need to prepare for the worst. Audio Production: Anil Chauhan