Climate change making prediction difficult for weather agencies across world: IMD DG

Impact of climate change on Monsoon


On climate change increasing the fragility of the Himalayas, he said, “Climate change is a fact and we need to plan all our activities accordingly.”

A study by the Indian Institute of Tropical Meteorology, MoES says the frequency of mini-cloud bursts (five cm or more rainfall in an hour) is increasing in the Himalayas. And it can also cause damage, Mohapatra said.

Asked about the impact of climate change on the Indian monsoon, he said: “We have got the digital data of the monsoon rainfall since 1901. Parts of north, east and northeast India show a decrease in rainfall, while some areas in the west, such as west Rajasthan, show an increase in precipitation.

“Thus, there is no significant trend if we consider the country as a whole – the monsoon is random and it shows large-scale variations.”

On July 27, the government had told Parliament that Uttar Pradesh, Bihar, West Bengal, Meghalaya and Nagaland have shown significant decreasing trends in the southwest monsoon rainfall during the recent 30-year period (1989-2018, both years included).

The annual rainfall over these five states, along with Arunachal Pradesh and Himachal Pradesh, has also shown significant decreasing trends, it said.

Mohapatra said an analysis of the day-to-day rainfall data since 1970, however, shows that the number of very heavy rainfall days has increased and that of light or moderate rainfall days has decreased.

“That means if it is not raining, it is not raining. If it is raining, it is raining heavily. The rainfall is more intense when there is a low-pressure system.

“This is one of the most important trends found in the tropical belt, including India. Studies have proved that this increase in heavy rainfall events and decrease in light precipitation are due to climate change,” he said.

The IMD head explained that climate change has increased the surface air temperature, which in turn has increased the evaporation rate. Since warmer air holds more moisture, it leads to intense rainfall.

Improved accuracy of IMD forecast


He said the IMD’s forecast accuracy has improved by about 30 to 40 per cent for severe weather events like cyclones, heavy rains, thunderstorms, heat waves, cold waves and fog in the last five years due to an improvement in the observational network, modelling and computing systems.

Sister organisations such as the Indian Institute of Tropical Meteorology and the National Centre for Medium Range Weather Forecasting carry out atmospheric modelling and the Indian National Centre for Ocean Information Services carries out ocean state modelling and supports the IMD’s forecasting improvement.

The weather bureau chief said the number of deaths due to cyclones, heat waves etc. has reduced over the years because of an improvement in the early warning lead time and preparedness, planning, prevention and mitigation approaches.

He said the IMD’s cyclone prediction with pinpoint accuracy is appreciated worldwide. The accuracy of heat wave forecasts is 92 percent. Heavy rainfall forecast accuracy at the meteorological sub-divisional level has improved from around 60 percent five years ago to 79 percent at present.

The forecast accuracy with a five-day lead time is 60 percent which gives more time to the general public and agencies to prepare for extreme weather.

The weather bureau’s location-specific rainfall forecasts have improved by up to 30 percent in the last five years. False alarms have decreased to 20 percent.

The IMD is providing forecasts for 1,096 cities and towns, up from 350 stations in 2019.

Nowcast forecast for the next three hours is being issued for 1,116 stations as compared to just 120 stations in 2013.

“There has been a tremendous improvement in service delivery — weather information for health, power, agriculture, air quality, hydrology, airports and marine sectors — in the last three years,” Mohapatra, who took over as the IMD chief in 2019, said.

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