Berlin, Apr 21: The Indian monsoon's yearly onset and withdrawal can now be forecast significantly earlier than previously possible, thanks to a novel prediction method developed by scientists, a breakthrough that may help maximise the subcontinent's food and hydro-power supplies.
The method is based on a network analysis of regional weather data, and the researchers will propose this approach to the Indian Meteorological Department.
The heavy summer rains are of vital importance for millions of farmers feeding the subcontinent's population. Future climate change will likely affect monsoon stability and hence makes accurate forecasting even more relevant.
"We can predict the beginning of the Indian monsoon two weeks earlier, and the end of it even six weeks earlier than before - which is quite a breakthrough, given that for the farmers every day counts," said Veronika Stolbova from the Potsdam Institute for Climate Impact Research (PIK) in Germany, the lead-author of the study.
"We found that in North Pakistan and the Eastern Ghats, a mountain range close to the Indian Ocean, changes of temperatures and humidity mark a critical transition to monsoon," said Stolbova.
Conventionally, the focus has been on the Kerala region on the southern tip of India. Rainfall timing is key for growing rice, but also for generating hydro power, researchers said.
Information about monsoon timing is key for Indian farmers to determine when to carry out the sowing. Crops like rice, soybean and cotton are normally grown during the June to September monsoon rainy season.
Even a slight deviation of the monsoon can lead to droughts or floods, causing damages. Also, the length of the monsoon is relevant for planning hydro power generation since the rains are necessary to fill the dams and reservoirs.
The scientists tested their method with historical monsoon data. It gives correct predictions for onset in more than 70 per cent and for withdrawal in more than 80 per cent of the considered years.
The main advantage of the proposed approach is that it allows to improve the time horizon of the prediction compared to the methods currently used in India, researchers said.
The study was published in the journal Geophysical Research Letters.