New Delhi: India may need to brace itself for a below-normal or deficient monsoon for a second consecutive year, with weather scientists predicting a 68 per cent probability that rainfall will be poor.
The India Meteorological Department (IMD), releasing the first stage of its annual long-range forecast for the 2015 monsoon season, said rainfall over India as a whole was likely to be 93 per cent of the long period average of 89cm from June to September.
Weather scientists said the impact of a below-normal rainfall on crops depended on how the rains are distributed across time and space during the four-month season India receives<>.
“Government departments and all states will be alerted,” Harsh Vardhan, the Union science and technology minister said, announcing the forecast today. “The cabinet secretariat and the Prime Minister’s Office have been informed about the forecast,” he added.
The IMD currently believes there is a 35 per cent probability that overall rainfall will be below normal and 33 per cent probability that it will be deficient. It has said there is a 28 per cent probability that rains will be normal and only 4 per cent probability that it will be above normal.
The 2014 monsoon was 88 per cent below average, classified as deficient.
“For agriculture, how rainfall is distributed is as important as how much rain falls,” said Laxman Singh Rathore, director-general of the IMD. Weather scientists will continue to observe the ocean and atmosphere, and plan to issue a second long-range forecast in early June in which they will predict how rains will be distributed across the four regions: the north-western region, central India, peninsula India, and eastern India.
Agrometerological experts say rainfall during July and August is critical for crops, particularly for transplanting rice. Maize, soya bean, pulses, and sugarcane are among other common crops sown during the monsoon season.
A home-grown experimental monsoon forecasting model – based on computer simulations of the weather and developed by scientists at the Indian Institute of Tropical Meteorology and the IMD – has also predicted a below normal rainfall at 91 per cent.
This experimental model also suggests that the north-western grain-basket states and central India are likely to receive below-normal rainfall, while eastern India and peninsular India will receive normal rainfall.
The first-stage long-range forecast relies on five distant meteorological predictors that have been statistically correlated with the behaviour of the monsoon over India. One of these five parameters – a rise in the sea surface temperature in the equatorial Pacific ocean, also called El Nino – which has been linked to poor monsoon performance in the past looks unfavourable for this year’s monsoon too, IMD scientist Sivananda Pai said.
“But there is no strict one-to-one relation with El Nino or any other parameter,” Rathore said. Since the 1950s, meteorologists have documented 14 El Nino years, of which India had poor monsoon rainfall in only eight.
One of the other four predictors – the land surface temperature over Europe – is favourable for this year’s monsoon, while the other three related to sea temperatures in the Atlantic, the Pacific, and the Indian oceans and sea-level pressures in East Asia are neutral, Pai, the IMD scientist, said.
