Tags:
Journalism of Courage
Even before analysts could total the cumulative loss to agricultural yields because of the unseasonal rains in recent weeks over the Indian subcontinent, speculation over the El Nino factor in influencing changing weather patterns over the Indian sub-continent continues to grow.
While the India Meteorological Department maintains that the country will record a normal monsoon this year, irrespective of the El Nino factor, experts from the field are now not denying that it could have played a part in catalysing the recent spate of thunderstorms and rain, in places as distant from each other as central Maharashtra, Rajasthan and Uttar Pradesh. Some experts even maintain that this factor continued to influence weather-patterns over the sub-continent even after the southwest monsoon, which accounts for 80 per cent of the annual rainfall, receded.
But what exactly is El Nino Spanish for quot;child Christquot; all about? Vast expanses of the central and equatorial Pacific Ocean are the seat of lower than 26 degrees celsius sea surface temperature SST and the lowest SST over tropical Pacific Ocean occurs in the waters off Peru and Equador. The SST field over these regions is known to undergo an episodic warming over and above the seasonal cycle. Such an episodic warming of the equatorial Pacific SST is known as El Nino. During a warm episode, the warming usually begins in April-May and reaches its maximum during the December-March period, that is, during the ensuing summer of the southern hemisphere.
The El Nino effect causes a warm ocean current called the Equatorial Counter Current in the mid-Pacific region to be strengthened. This current, in turn, disrupts the Humbolt Current, a cold current in the south Pacific Ocean region. This phenomenon, which is believed to occur once a decade, results in disturbing the weather patterns in the entire region.
While the El Nino is a global phenomenon, going by meteorological data over the past years, including those periods when the country experienced long spells of drought, it would appear to influence the Indian monsoons quite decisively.
Rainfall over South Asia is predominantly due to the summer and winter monsoon systems, with only a small fraction being associated with cyclonic storms and other atmospheric disturbances traversing certain parts of the region, mostly during the transition periods, says Pant.
The southwest monsoon, which usually visits the sub-continent from June to September, accounts for about 70-90 per cent of the annual rainfall over a major part of South Asia. The northeast monsoon, during the months of October to January, serves as a major source of rainfall over the southern Indian peninsula and Sri Lanka.
Pant feels that Indian scientists must now study more closely the relationship between the El Nino and these rainfall patterns. Said Pant, quot;In order to analyse the causes and effects of the phenomenon accurately, the rainfall data and, more importantly, the sea surface temperature data of Asia, South East Asia and also South China should be gathered and processed adequately.quot;
But there are others who doubt whether Indian meteorologists are properly equipped to understand the phenomenon. Blaming it on the lack of the necessary technical infrastructure to study complex phenomena such as El Nino, expert meteorologists are now pointing to the grey areas in complex meteorological studies. Said a senior weatherman: quot;It is true that the country does not have sufficient data to study the relation of El Nino and its relation with Indian monsoon in greater detail.quot;
Scientists explain that in order to study the phenomenon, satellite measurements of sea surface temperature over a large oceanic area are required, whereas the INSAT satellites, currently being used for meteorological purposes, do not have microwave sensors to perform this function. As a result, the satellites are unable to measure this temperature accurately, once its optical remote sensing capabilities are hampered by the monsoon clouds. As one expert put it, quot;The main purpose of studying the sea surface temperature phenomenon fails just at the time when it is required the most.quot;
But V. Thapliyal, Deputy Director General of Meteorology Climatology, maintains that the understanding the El Nino phenomenon completely remains a distant dream because quot;efforts to develop the technique to solve non-linear mathematical equations have not been successful so farquot;.
Whether it is an inadequacy in remote sensing capabilities or in mathematics, the El Nino, crucial as it seems in influencing Indian weather conditions, remains largely a mystery wrapped in an enigma.
