The Hindu : `An above normal monsoon or only a small deficit'

Online edition of India's National Newspaper
Tuesday, May 27, 2003

Southern States

Southern States - Kerala

`An above normal monsoon or only a small deficit'

By N. Gopal Raj

THIRUVANANTHAPURAM MAY 26. In the face of a whole range of forecasts on the outcome of the south-west monsoon, there are concerns about whether India could face a second year of poor monsoons. But an examination of the country's historical rainfall record suggests that such an outcome is improbable.

The south-west monsoon, which provides more than three-quarters of the country's annual rainfall, is said to be normal if the nationwide rainfall during June to September is within 10 per cent of the long-term average. If the country receives more than 10 per cent, it is seen as an excess monsoon year. A deficit of more than 10 per cent is categorised as a national drought year. Last year's monsoon showed a deficit of 19 per cent.

The India Meteorological Department's has forecast that the coming monsoon would be 96 per cent of the long-term average, making it a near-normal monsoon year. It has also predicted that there is only a 21 per cent probability of a drought.

The model developed by A.K. Sahai and his colleagues at the Indian Institute of Tropical Meteorology, Pune, using sea surface temperatures alone, was one of the few which correctly predicted a drought last year. Although the model's forecast for this year has not been made public, it is believed to have shown an above normal monsoon.

With computer simulations using a Global Circulation Model (GCM), the National Centres for Environmental Prediction in the United States had also predicted last year's drought. The results of the latest GCM simulations suggest that this year too, there would be a deficit, but not as bad as last year's.

The Bangalore-based Centre for Mathematical Modelling and Computer Simulations (CMMACS), on the other hand, has predicted a 15 per cent deficit this year. CMMACS had predicted a normal monsoon last year.

What are the chances of India having a second year of poor monsoon rains? Since the country possesses over 160 years of rainfall data, the past offers interesting lessons.

"India has had alternating 30-year epochs of good and bad monsoons," says P.V. Joseph, who has spent a lifetime studying the monsoon and is currently associated with the Cochin University's Department of Atmospheric Sciences. "Fortunately, we are currently in a good epoch."

In an epoch of poor monsoons, not only are there more droughts, but also such droughts can occur in successive years. There were nine drought years in the 1841-1870 period, six droughts in the 1901-1930 period and 10 droughts during 1961-1990.

Moreover, in each of these poor monsoon epochs, at least once there would be droughts in successive years. There were three successive years of drought starting in 1985.

By contrast, there were only three drought years in the good monsoon epoch of 1871-1900, two during 1931-1960 and just one (last year's drought) since 1991. Further, there have never been successive years of drought during a good epoch. In fact, in the five droughts which occurred in the previous good epochs, the following year gave an above normal monsoon. Only in 1952 was there a shortfall after the previous year's drought. Then too, the shortfall was only 7 per cent, which is within the range for a normal monsoon year.

"So, the odds are that this year we will have either an above normal monsoon or only a small deficit," says Dr. Joseph.

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