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Monsoon alert, word on crop impact awaited

New Delhi, April 24: The monsoon rainfall over India this year will be 5 per cent below average, the national weather agency said today in a preliminary forecast.

Scientists said the prediction was primarily meant to stir the nation into thinking about contingency planning.

The India Meteorological Department (IMD) said the rainfall over India as a whole from June through September would be 95 per cent of the long-period average.

It said there was a 56 per cent chance that India would receive below-normal or deficient rainfall this monsoon season.

“This is only a broad indication of which side of the normal the 2014 summer monsoon will stand,” D. Sivananda Pai, head of the long-range forecasting division at the IMD, Pune, told The Telegraph. “There may be significant variations at the regional and local levels.”

Meteorologists say the preliminary long-range forecast will allow the agriculture, power and water resources departments at the Centre and the states to prepare for a possibly poor-performing monsoon. India’s long-period average monsoon rainfall is 89cm.

The IMD forecasts the amount of monsoon rainfall over India with the help of five predictors: sea surface temperatures in the southern Indian, northern Atlantic, northern Pacific and equatorial Pacific oceans, and land temperatures in northwest Europe.

“A warming trend in the sea surface temperatures currently observed over the equatorial Pacific is a significant negative signal for the monsoon,” Pai said. “But the impacts of the other four predictors are close to neutral.”

Computer simulations of the global weather have indicated a 60 per cent probability that the rising equatorial Pacific temperatures could reach levels that scientists call El Nino, a weather condition associated in the past with poor monsoon performance over India.

The IMD is expected to issue a revised forecast in June with predictions for overall rainfall behaviour in northwest, central, southern and eastern India from June to September, with more specific predictions for July and August — the months for agriculture.

Rice, sugarcane, soybean, pulses (black gram, green gram, pigeon pea), maize and peanuts are among the common crops sown across India during the monsoon season. But the long-range forecasts have a limited use in agricultural planning.

Regional variations could mean some areas will receive above average, even excess, rainfall while others will get poor rainfall — even as the nation as a whole records below-normal monsoon.

Agricultural scientists have over the years evolved alternative crop strategies for the years of deficit or delayed monsoon rain.

“But such strategies are tailored for specific areas with locally available and viable options,” Shamarao Jahagirdar, a scientist at the University of Agricultural Sciences, Dharwad, told this newspaper.

Scientists say crop planning also relies on the seven-day forecasts issued by the National Centre for Medium Range Weather Forecasting, Noida, that are distributed to farmers across the country through state agricultural universities.

Experimental forecasting techniques based on simulations of the global weather on supercomputers have also predicted a below-normal or deficit monsoon.

A simulation run by the Indian Institute of Tropical Meteorology, Pune, suggests that monsoon rainfall this year will be 96 per cent of the average. Another experimental forecast based on ocean data extracted from a US model indicates the rainfall could be 88 per cent of the average.

“But these are experimental models,” Pai said.

“Such simulation-based models need to be improved for accurate monsoon forecasts.”