Climate change has hampered forecasting agencies' ability to accurately predict severe events, and weather bureaus around the world are focusing on increasing observational network density and weather prediction modelling to improve predictability, according to India Meteorological Department (IMD) Director General Mrutyunjay Mohapatra.
He also stated that, while the country's monsoon rainfall has not shown any significant trend, the number of heavy rainfall events has increased while the number of light rainfall events has decreased due to climate change.
"We have digital data on monsoon rainfall since 1901." Rainfall is decreasing in parts of north, east, and northeast India, while it is increasing in parts of the west, including west Rajasthan.
When asked about the impact of climate change on the Indian monsoon, the IMD chief said, "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 informed Parliament that the southwest monsoon rainfall in Uttar Pradesh, Bihar, West Bengal, Meghalaya, and Nagaland had decreased significantly over the previous 30-year period (1989-2018, both years included). The annual rainfall in these five states, as well as Arunachal Pradesh and Himachal Pradesh, has also shown significant decreasing trends, according to the report.
According to Mohapatra, an analysis of day-to-day rainfall data since 1970 shows that the number of very heavy rainfall days has increased while the number of light or moderate rainfall days has decreased. "That is to say, if it isn't raining, it isn't raining." It is raining heavily if it is raining. When there is a low-pressure system, the rainfall is more intense. This is one of the most significant trends observed in the tropical belt, which includes India. "Studies have shown that climate change is causing this increase in heavy rainfall events and decrease in light precipitation," he told in an interview.
The senior meteorologist explained that climate change has increased the temperature of the surface air, which has increased the rate of evaporation. Because warmer air holds more moisture, it causes heavy rain.
"Climate change has increased atmospheric instability, resulting in an increase in convective activity- thunderstorms, lightning, and heavy rainfall." Cyclones in the Arabian Sea are becoming more powerful. Forecasters are being challenged by the increased frequency of extreme weather events. Climate change has hampered the ability to predict heavy rainfall, according to studies," he said.
To improve predictability, the IMD is expanding its observational network with radars, automatic weather stations, rain gauges, and satellites. Its forecast accuracy for severe weather events such as cyclones, heavy rains, thunderstorms, heat waves, cold waves, and fog has improved by about 30 to 40% in the last five years due to improvements in the observational network, modelling, and computing systems of the IMD and the Ministry of Earth Sciences (MoES).
Sister organizations such as the IITM and the NCMRWF conduct atmospheric modelling, while the INCOIS conducts ocean state modelling and assists the IMD in improving forecasting.
"We have installed six radars in the northwest Himalayas, with four more planned for this year." The procurement of eight radars in the northeast Himalayan region is currently underway.
"There will be some gaps in the rest of the country that will be filled with 11 radars." The number of radars will rise from 34 now to 67 by 2025, according to Mohapatra. The MoES also intends to upgrade its high-performance computing system, which currently has a capacity of 10 petaflops, to 30 petaflops in the next two years, in order to assimilate more data into the model, which can then be run at higher resolutions.
The IMD/MoES weather modelling system (global forecasting system) currently has a resolution of 12 kilometres. The goal is to run six kilometres. Similarly, the regional modelling system's resolution will be reduced from three to one kilometre. The higher the resolution and precision of a weather model, the lower its range.
"We are currently providing forecasts up to the district and block levels." "In the future, we will provide forecasts up to panchayat clusters and specific locations within cities," Mohapatra said.
"Climate change is a fact, and we need to plan all of our activities accordingly," he said of climate change's increasing fragility of the Himalayas. According to a study conducted by the Indian Institute of Tropical Meteorology, the frequency of mini-cloud bursts (five cm or more of rain in an hour) is increasing in the Himalayas. It can also cause harm, according to Mohapatra.
According to the IMD director, the number of deaths caused by cyclones, heat waves, and other natural disasters has decreased over the years due to advancements in early warning lead time and preparedness, planning, prevention, and mitigation approaches.
"In the last three years, there has been a tremendous improvement in service delivery — weather information for health, power, agriculture, air quality, hydrology, airports, and marine sectors," Mohapatra, who took over as IMD chief in 2019, said.
