Weather conditions that promote El Nino persistent, says Met department; drought feared
In its first monsoon forecast in late April, the India Meteorological Department (IMD) had announced that monsoons would be normal this year and there was a little chance of El Nino—associated with dry spells west of the Pacific—arriving in the second half of the season. But of late, IMD seems to have shifted its stand. Now the weather agency is openly admitting El Nino could influence the monsoons set to hit Kerala coast by June 6. In recent years, strong correlation between El Nino and aberrant weather has been observed. Several El Nino years have coincided with droughts in India—2009 being a prime example. IMD's warnings have important implications for the country's agriculture, 60 per cent of which is rain-fed.
D S Pai, director of long-range forecasting at IMD, however, is guarded in his remarks. “There has not been any change in IMD's stand. We had maintained in our long-range forecast given out in April that there is a noticeable chance of El Nino re-emerging later during the season,” he says. He adds that it's just that the conditions favouring El Nino have persisted, so the prospect of El Nino occuring seems more likely now. “Anyway, it's difficult to get a clear picture of El Nino in April. Things take shape only in May and June.” He informs that in it's June forecast, the Met department would be able to inform whether El Nino is strong enough to influence the monsoon and whether there is a probability of the occurence of drought.
Why is El Nino so dreaded?
El Nino/La Nina-Southern Oscillation or ENSO is an ocean-atmospheric phenomenon that occurs in a cycle. La Nina, which is one part of the cycle, is signified by a decrease of 3-5°C in sea surface temperature across the Equatorial Pacific Ocean and it is favourable for monsoons in India. El Nino, which is La Nina’s counter-phenomenon, is often accompanied by drought in India and heavy rainfall in the Pacific coast of Latin America.
Over the years, research has shown there is an association between El Nino and deficient rainfall in India. However, all El Nino years are not deficient in rainfall. Pai says 1997 saw the strongest El Nino phenomenon in the last century, but the monsoon rainfall that year was 101 per cent of long-period average (average of 50 years), which means it was marginally more than 89 cm. The five major droughts of the past 20 years—1982, 1987, 2002, 2004 and 2009—were accompanied by El Nino. A research analysis between 1880 and 2004 by Krishna Kumar of Indian Institute of Tropical Meteorology (IITM) shows that in 13 instances of El Nino occurrence, India experienced normal monsoon rainfall, while in 10 instances rainfall was below normal.
Degree of uncertainty
World Meteorological Organisation (WMO) in its latest update has maintained a guarded stand on El Nino. It says that while El Nino could emerge later in the season, there's still some uncertainty about it's occurrence. “Uncertainty regarding neutral or El Nino conditions for later in 2012 is due to questions over whether the warming of the Pacific Ocean will be large enough to cause changes in the atmosphere, which is a necessary condition to sustain an El Nino event,” WMO states.
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