In North India, decline in snowfall, rainfall spells doom

Winters are getting warmer and drier in north India with hilly areas of the region worst affected. Uttarakhand has reported ‘large deficient rainfall’ of minus 76 per cent departure from normal rainfall for October to December months of the last year followed by minus 49 per cent ‘deficient rainfall’ in the hilly state of Himachal Pradesh for the same time period. Jammu and Kashmir has minus 29 per cent rainfall departure, whereas Punjab has minus 47 per cent rainfall departure in the last three months. The worst affected state in north India is Uttar Pradesh whose West Uttar Pradesh subdivision and East Uttar Pradesh division has minus 96 per cent and minus 95 per cent rainfall departure, respectively. Winter precipitation is important for the north Indian states as it has a direct bearing on both water resources and rabi crops (winter rains help maintain soil moisture). 

Along with a decline in winter rainfall, Uttarakhand and parts of Himachal Pradesh have witnessed significantly warmer winter as the maximum temperature has remained a few degrees above normal in the last three months. Last month, in December, Uttarakhand and Himachal Pradesh recorded maximum temperature 2-4 degree Celsius above the normal. The maximum temperature in Jammu and Kashmir, too, was 1-2 degree Celsius above normal in the last three months.

The hill states of the North India —- Himachal Pradesh, Uttarakhand, and J&K, in particular — are facing a double whammy of rising maximum temperatures and declining precipitation in the winter months. And, this is not a one-off event, but, a trend recorded in the IMD’s 2013 monograph, ‘State Level Climate Change Trends in India’. This monograph is based on long-term (50 years, ie, from 1951 to 2010) temperature and rainfall data from hundreds of weather monitoring stations spread across India.

The IMD monograph notes that in the 50 years period, “the highest increase in winter mean maximum temperature [across India] was obtained for Himachal Pradesh (plus 0.06 degree C/year)”. Uttarakhand showed a significant increase (plus 0.02 degree C/year) in winter mean maximum temperature, too. In the monograph, winter months include December, January and February; October and November are post-monsoon months.

Apart from an increase in the temperature, the 2013 IMD study has also reported a decline in winter rainfall trends over Himachal Pradesh, Uttarakhand, and Uttar Pradesh. In contrast, the annual rainfall trends have significantly increased over J&K (plus 1.88 mm/year). The trend of increased rainfall in Kashmir region has also been documented in the research studies conducted by the Department of Earth Sciences of Kashmir University in Srinagar. 

The department’s research shows an increase in average temperature in upper Indus basin region in the winter months of December and January. Whereas total precipitation (rainfall and snowfall) in the Kashmir region has not changed, the snowfall is showing a decreasing trend and rainfall is on the rise. The J&K State Climate Change Action Plan, too, notes that “amount of snowfall has reduced over the years”. Such changes in rainfall and snowfall can have long-term impacts on the region’s water security, as snowfall feeds the glaciers, which provide freshwater throughout the year. There are already reports of decreasing thickness of glaciers; the Kolahoi glacier in Pahalgam is retreating at a rate of 20 metres every year.  

Meteorologists claim that rising winter temperature and declining winter precipitation in North India is linked to the changes observed in the Western Disturbances. A  Western Disturbance (WD) is an extra-tropical storm (low pressure) which originates in the Mediterranean region and travels to the eastern direction bringing rainfall and snowfall in the northern parts of the country during the winter season. But, the frequency and strength of these extra-tropical storms seem to be declining in the winter season. 

An investigative research study, published in February 2017 issue of the Asia-Pacific Journal of Atmospheric Sciences, has linked low precipitation in northwestern India with anomalously low western disturbance activity. The researchers of the study note that “despite the fact that WDs play a very important role in India’s winter weather, limited research has been done to investigate the causes of their inter-annual variability.” 

It is clear that winter climate of north India is changing and is expected to have far-reaching impacts. Scientists have projected that winter temperature rise of 0.5 degree Celsius will reduce rain-fed wheat yield by 0.45 tonnes per hectare in India. Impacts on our water security are yet to be ascertained. 

There is an urgent need to study the changing pattern of the WDs that bring winter precipitation in north India. Along with it, there is a need to collate real-time data on snowfall in the upper Himalayan region of the country to ascertain trends in snowfall departure. 

The author is an independent journalist based in Mumbai