January is usually the month when Kashmir and Himachal Pradesh are blanketed with snow. This winter has however seen these regions extremely dry. Places like Gulmarg and Pahalgam, known to be popular destinations for skiing, have been unable to offer avenues for the winter sport.
Himachal Pradesh, again a state famous for several mountain resorts, has also witnessed dry slopes and valleys of brown grass. The Himalayan ranges of Uttarakhand have also reported minimal snowfall, with the first bout of snow in January at Auli, a popular hill resort, only reported on January 19.
Records from the India Meteorological Department (IMD) suggest Himachal Pradesh has registered its driest January since 1901, with a 99.7% shortfall in January rain compared to what is normal. Until this year, the record for the driest January this year was 1996, which reported a 99.6% shortfall.
What is the reason for the lack of snowfall?
Snowfall requires adequate moisture as well atmospheric temperatures to be 0 degrees C or lower. Temperatures have been fairly low since December. An analysis by the IMD in mid-January reported that maximum temperatures were running 5-8 degrees C ‘below normal’ over the plains of North India since December 29.
Minimum temperatures were also below 4 degrees C at many stations in Northwest India for most of January. This also resulted in very dense fog persisting over the plains of Northwest India. Several cities in the region reported zero visibility over the entire North Indian plains, from Amritsar to Dibrugarh, across Haryana, Delhi, Uttar Pradesh, and Bihar.
While moisture and high aerosol loads contribute to fog, there were three major reasons behind the lack of snowfall, and consequently intense cold waves over North India. These were a drastic fall in the number of Western Disturbances (WDs) over Northwest India; prevailing El Niño conditions, and the absence of a strong jet stream.
How do these three factors influence snowfall?
WDs are storms that originate in the mid-latitude regions and travel thousands of kilometres to bring rains across northern India. Such WDs in the winter dissipate fog and increase the sunshine incident on the ground, raising temperature there. When the temperatures are low, they also result in snowfall and water being available as snow melt. Melting glaciers contribute to the water available to the Ganga, the Indus, and the Yamuna rivers.
On the other hand, WDs can also result in hail, which is destructive to standing wheat crops. Usually, five to seven WDs affect Northwest India in the period from December to January. But this winter, there have been none. (There were actually two WDs in this period but their impact was mainly confined to Gujarat, north Maharashtra, East Rajasthan and Madhya Pradesh.) As a result, the Western Himalayan Region received 80% less rain than normal.
Prevailing El Niño conditions over the equatorial Pacific Ocean, or warmer ocean temperatures, may have had a role to play. But irrespective of an El Niño – or its converse, the La Niña – the number of WDs in December and January have generally been on the decline. In the winter of 2022-2023 (December and January), India reported its hottest ever December. The country’s northwest, which usually reports nearly a third of its rainfall in this season, reported an 83% rainfall deficit.
Conversely, the number of WDs in February and March have been rising of late, causing flash floods particularly in Uttarakhand and Himachal Pradesh. Last year, for instance, there was record-breaking rain in February.
In general, the traditional pattern of WDs has been disrupted since 2019, which was the last year we had a conventional WD pattern. The resulting instances of extended dry periods and intense wet spells are characteristic of global warming, as several meteorologists and climate scientists have been pointing out in recent years.
What role do jet streams play?
Jet streams are powerful winds, ranging in speed from 250 to 320 km/hr, travelling at about 12 km above mean sea level. They are the carriers of WDs. However, a lack of moisture means they have been contributing to the subsidence of cold air so far, thus enhancing the cold over north India.
The jet streams set in after the monsoon withdraws and are also able to draw in moisture from the Arabian Sea. In recent years, the jet streams have been shifting northwards.
This, emerging research has suggested, is a result of the warming of the Arctic seas, which then affects the natural gradient of temperature required to ensure the strength and direction of the jet streams.
- January is usually the month when Kashmir and Himachal Pradesh are blanketed with snow
- As per IMD, Himachal Pradesh has registered its driest January since 1901, with a 99.7% shortfall in January rain compared to what is normal
- Three main reasons behind lack of snowfall - drastic fall in the number of Western Disturbances; prevailing El Niño conditions, and the absence of a strong jet stream
Published - January 25, 2024 09:45 am IST