Stormy History

MUCH of weather prediction across the world, strangely enough, is guesswork, albeit supported by certain scientific data. In the early 1880s, the first Director General of Meteorology (DG Met) in India, Henry Blanford, departed from the traditional modes of prophecy and used Himalayan snowfall as the sole criterion for predicting monsoons. While this model met with initial success, changes in climatic conditions over the years made this model ineffective although the Himalayan snowfall has remained one of the determinants of monsoon.

Around 1920, another DG Met, Sir Gilbert Walker, sifted through more than 3,000 parameters and arrived at a few important determinants which had a statistical correlation with the nature of monsoons. Though this model succeeded where the Blanford one had failed, it could predict monsoons for only a part of India rather than give a complete national forecast. 

Later, following a total failure of monsoon predictions in the drought year of 1987, a new model of monsoon measurement was put into place by Indian scientists under the leadership of the then secretary, Department of Science and Technology, V.R. Gowarikar. The new parametric and power regression model, put into operation in 1988, uses 16 regional and global land-ocean-atmospheric parameters to provide a quantitative monsoon rainfall forecast for the country as a whole. For a few parameters, observations up to May-end in a year are required while for others, readings are taken in the preceding winter itself. And while some readings are taken at the ground level, some are taken high above the ground and some at sea level.

But scientists note that the power regression model is prone to error. Also, it can predict only the aggregate figures of monsoon for the entire four-month season and is unable to give any time-specific or area-specific information. However, universities and institutions like the IITs have developed new models which are being tried out as test cases to determine time-specific and area-specific monsoons which, if successful, will be adopted by the Government.