The Indian Meteorological Department (IMD) is set to announce that it has reached a new sophistication in forecasting rainfall which, next year, could give farmers information about the movement of the monsoon in their region 20 days in advance, instead of the current five days.
“Predicting breaks and active cycles is the biggest challenge for meteorology. But we expect to be able to make these 20-day-advance forecast, at least by next year,” said Madhavan Rajeevan, director, National Climate Centre, which primarily handles IMD’s forecasting activities.
If IMD is successful, it could greatly influence sowing patterns among farmers, most of whom depend heavily on IMD’s periodic forecasts.
Some “95% of our farmers depend on the weather bulletins issued by the IMD”, said Chengal Reddy, president, Indian Farmers Association. “So, better forecasting abilities naturally influence farmer’s decisions.”
The summer monsoon is crucial for India’s 234 million farmers and their crop of rice, soyabeans, peanuts and lentils—referred to as the kharif crop.
Except for states such as Punjab and Haryana, which are primarily irrigated, agriculture in most states is dependent on the monsoon.
IMD’s methodology is not known yet, but the underlying principle involved is modelling the low-pressure system that passes over India during the monsoon, along with factors that aid or obstruct its progress.
Short-term forecasts, which are primarily handled by the National Centre for Medium Range Weather Forecasting in Noida, use numerical models, which record a host of oceanic and atmospheric weather parameters on a given day, crunch it in supercomputers and give a fairly accurate forecast for three-four days.
IMD has had a rather mixed record in long-term forecasts. In the past four years, it has correctly predicted the June-September summer monsoon only twice.
Last week, IMD had to revise its initial predictions of an early onset of the monsoon over Kerala. On 14 May, it predicted the monsoon’s arrival on 24 May, using a climate model specifically designed for this purpose.
However, on 23 May, it withdrew the first prediction and put out another forecast, claiming that “unforeseen anomalous weather conditions had obstructed the monsoon’s progress.”
Hence, it is hardly surprising that IMD’s effort to put out a 20-day forecast is being met with scepticism. “In the last 10 years, IMD has been experimenting with a wide range of models,” said P. Goswami of the Indian Institute of Tropical Meteorology who has published a number of papers on the active/break cycles in the monsoon. “But given that the Indian monsoon is rather tricky, it would require considerable work to determine the robustness of this (IMD’s new model).”
Anuj Kumbatt, who is part of a pilot project in Andhra Pradesh that attempts to provide farmers with accurate weather information, said IMD’s plans were welcome but overtly ambitious.
“Farmers rely a lot on their experience and gut feeling, along with the meteorological department’s forecast. I think the IMD scheme will be useful if it can predict impending droughts,” he said.
India faced droughts in 1998 and 2002, none of which IMD was able to predict.