Winter storms that present essential snow and rainfall to northern India are arriving considerably later within the yr in comparison with 70 years in the past, a brand new research has discovered, exacerbating the danger of catastrophic flooding whereas additionally decreasing very important water provides for hundreds of thousands of Indians.
The cyclonic storms, often called western disturbances, sometimes deliver heavy snow to the Himalayas from December to March. This snowpack slowly melts in spring, offering a gradual provide of irrigation water for wheat and different crops downstream.
The research, printed as we speak (Tuesday, 12 March 2024), within the journal Climate and Local weather Dynamics, reveals western disturbances are occurring extra typically throughout India’s summer time. Over the previous 70 years, the storms have elevated in frequency by 60% from April to July, decreasing snowfall and growing the danger of heavy flooding.
Writer Dr Kieran Hunt, of the College of Studying, mentioned: “Robust storms at the moment are twice as prone to happen within the north of India in June in comparison with 70 years in the past. With hotter and moister air right now of yr, these late storms are dumping heavy rainfall as an alternative of snow. This raises the danger of lethal flooding like we noticed in Uttarakhand in 2013 and round Delhi in 2023.
“Some areas of Kashmir noticed no snow in any respect in December or January. It is a severe concern for the 750 million individuals within the Indus and higher Ganges basins who depend on these winter snows for water provides.
“The lack of winter snow and the growing late-season storms that heighten flood dangers is a one-two suckerpunch that underscores the pressing want to reply to the far-reaching impacts of local weather change on this delicate area.”
Warming the Tibetan Plateau
The analysis crew attributes this seasonal shift to adjustments within the subtropical jet stream, a high-altitude air present that steers western disturbances. The speedy warming of the Tibetan Plateau — which is an extended stretch of stage excessive floor on the intersection of Central, South, and East Asia — is creating a bigger temperature distinction with surrounding areas, fueling a stronger jet stream that powers extra frequent and intense storms.
On the similar time, world warming is weakening the temperature distinction between the equator and poles that usually attracts the jet stream northward in summer time. Consequently, the jet stream is more and more lingering at southerly latitudes later into spring and summer time, permitting extra storms to strike North India after the winter snow season.
Arriving within the pre-monsoon warmth, these more and more frequent late-season storms unleash heavy rainfall as an alternative of snow, elevating dangers of devastating flooding. In the meantime, winter snowfall is declining because the area warms, threatening spring water provides.
