Rain deficiency 100% in 6 states, 2 UTs, says IMD
Several states and union territories in India are experiencing a nearly 100% rain deficiency in January, following a large deficit in December. The lack of winter precipitation is due to the absence of strong western disturbances in the region, which is causing cold wave conditions and impacting the Rabi (winter) crop. The unusual weather pattern may be attributed to global warming, Arctic Sea ice melting, or natural variability. The lack of rain and snow is also affecting Himalayan glaciers and water resources in the region.
At least six states and two union territories have recorded a nearly 100% rain deficiency in January after a large deficit in December – the two peak winter months for north India — and the season is likely to end on a dry note, weather experts said.
The rain deficiency has come amid spells of dense to very dense fog, and cold day and cold wave conditions over the northern plains for at least two weeks, with experts attributing the lack of winter precipitation largely to the absence of strong western disturbances (WDs) over the region.
North India is seeing a unique situation, experts said, with western disturbances not touching the country at all as they sweep by through more northern latitudes.
Generally, five to seven WDs impact north India between December and January. This winter, however, no active WD has impacted the region.
“The jet stream is also moving north of India. WDs form along with jet stream instability but that instability is not within the Indian region. They are all moving north of India,” said M Rajeevan, former secretary, ministry of earth sciences.
On Monday, a WD could be seen in satellite images above the Indian region, when seen on a map. Jet stream winds of 240 to 250 kmph at 12.6km above mean sea level are also prevailing over the plains of North India. This is causing cold air to subside, which in turn is strengthening cold wave/cold day conditions over the region. Similar intensity of jet stream is likely to continue for the next three-four days, the IMD warned.
It is not clear exactly what may be triggering this unusual pattern. “We can see a small system now that is again slightly above India. The westerly jet stream is moving north, which is likely to be a result of global warming or Arctic Sea ice melting. It may be a result of natural variability and north Atlantic oscillation,” Rajeevan said, adding that a detailed study of the factors is needed.
The lack of active WDs can also be attributed to El Nino conditions over the equatorial Pacific, the IMD had said in a note on January 17.
“Jet stream winds are very strong. The jet stream, which is north of the Himalayas in summer, moves through slightly lower latitudes in winter. A weaker jet stream indicates higher western disturbance activity. There is cold air incursion from the jet stream,” explained DS Pai, senior scientist at IMD.
Under the influence of a fresh western disturbance, light isolated rainfall/snowfall is likely over Western Himalayan Region from January 25 to 28, the IMD said on Monday. “The impact may be limited to higher elevations and may not penetrate the plains,” said M Mohapatra, director general, IMD.
In January so far, there has been no rain or snow in Delhi, Punjab, Haryana, Jammu and Kashmir, Ladakh and Chandigarh. Uttarakhand and Himachal Pradesh have recorded 99% rain deficiency.
Some northeastern states that recorded significant rain deficiency during monsoon months have also recorded 100% rain deficiency in January. These include Manipur, Mizoram and Tripura, data from IMD showed.
In December, J&K recorded a 79% rain deficiency; Himachal Pradesh 85%; Uttarakhand 75%; Punjab 70% and Haryana 54%.
The meteorological reality has been starkly in contrast to what the IMD predicted on January 1, when it said monthly rainfall for January 2024 over north India — consisting of seven meteorological subdivisions (East Uttar Pradesh, West Uttar Pradesh, Uttarakhand, Haryana, Punjab, Himachal Pradesh, Jammu & Kashmir and Ladakh) — was likely to be above normal (>122% of Long Period Average). Monthly rainfall over the country as a whole during January 2024 is also most likely to be above normal (>118% of LPA), the Met department had said.
HT reported on January 13 that dry, snowless peaks have cast a shadow on tourism in Kashmir and Himachal Pradesh but the impact of the underlying causes on the next few months is far more worrying -- for they could portend a warmer spring.
“The transition will not happen immediately. Bare, snowless peaks will absorb solar radiation and whatever little snow cover, if there is snowfall after this can melt easily. That can cause warming in spring season,” Pai said.
The absence of active western disturbances and shortage of rain and snow will have implications for the Rabi (winter) crop, experts said.
Rajeevan said while artificial irrigation may be able to protect the winter Rabi crop, including the staple wheat, there could be cause for alarm if dry soil conditions continue.
Precipitation falling as snow is essential for Himalayan glaciers, which in turn feed rivers that are lifebloods for downstream population of the Indian subcontinent. The climate crisis has affected the Himalayas, which is noticeable through lower snowfall and higher snowmelt, leading to critical water resource stresses and managements, a 2022 paper by scientists from IMD and Jawaharlal Nehru University published in International Journal of Climatology states.
The paper concluded that WDs are showing a decreasing trend in frequency and intensity in the present and near-future. But in far-future intensity of WDs shows an increasing trend.
Another paper, published in the Journal of Climate in 2019 led by University of Reading, said there is likely to be a further decrease in WD frequency in various climate crisis scenarios. The decline in WD frequency and intensity will cause a decrease in mean winter rainfall over Pakistan and northern India amounting to about 15% of the mean — subject to the ability of the models to represent the responsible processes.