This may lead to further food insecurity in a region already grappling with depleting Rabi crop production since past few years
The lack of snow and rain over the western Himalayas — that has continued from December 2023 into January 2024 — could give way to heat waves in March and April and heavy rainfall in the pre-monsoon season over northwest India, experts have told Down To Earth (DTE).
This may lead to further food insecurity in a region already grappling with depletion of Rabi crop production since the past few years.
From January 1 to January 23, six states in northwest India have received no rainfall. Two states (Himachal Pradesh and Uttarakhand) have received 99 per cent less rains than normal, and the rest have also received next to no rain. Rajasthan has recorded a rainfall deficit of 88 per cent and Uttar Pradesh of 73 per cent.
The India Meteorological Department (IMD) put out a statement on January 18 that attributed the extreme lack of precipitation (80 per cent less than normal for December) in the Western Himalayan region to a lack of active western disturbances.
Western disturbances are extra tropical storms that travel from the Mediterranean region towards India and bring most of the winter snowfall in the high mountains and rainfall in the lower hills and plains.
Generally, there are 5-7 active western disturbances that affect northwest India during December and January, according to IMD. This year there have been only two of these storms (one in December and one in January) and “their impact was mainly confined to Gujarat, north Maharashtra, east Rajasthan and Madhya Pradesh,” said IMD.
DTE analysed data from IMD to find that India has been impacted by 21 western disturbances between October 1 and January 23. Of these, only four have been active — one in each month. This is why post-monsoon rainfall in states such as Uttarakhand and Himachal Pradesh was much lower than normal.
IMD says that one of the reasons for the decrease in western disturbance activity is the El Nino phenomenon in the equatorial Pacific Ocean.
El Nino is the warmer-than-normal phase of the El Nino Southern Oscillation (ENSO) phenomenon that causes weather disruptions all around the world, including a general lack of rainfall and heightened temperatures in India.
The World Meteorological Organization declared the prevalence of El Nino conditions in July 2023, which is currently at its peak.
“Snowfall deficit is mostly consistent with the trend of reduced western disturbance and reduced precipitation. The winter so far is consistent with the El Nino in terms of being restricted to northwest and northern India but the Arabian Sea warming has pulled it down over to Mumbai as well,” Raghu Murtugudde, a climate scientist at the Indian Institute of Technology, Bombay and University of Maryland, United States, told DTE.
Earlier, DTE had reported that the trend of decrease in western disturbance activity could be due to global warming and consequent climate change.
Northwest India is currently undergoing a period of cold day / cold wave and dense fog conditions. During a ‘cold day’, the maximum temperature (daytime temperature) becomes much less than the normal. During a ‘cold wave’, the minimum temperature (night-time temperature) falls much below normal.
This is due to strong jet stream winds over northern India, according to the IMD. The jet stream is a band of winds circulating the Earth in the upper layers of the atmosphere that has an influence on the weather conditions in the lower layers of the atmosphere.
This shift in the jet stream may also be tied to the El Nino, according to Murtugudde. Usually, during an El Nino event, ‘cold wave’ days are less than normal and IMD says that there have been “lesser number of Cold Wave Days during December and January”.
A research paper published in the journal Weather and Climate Extremes on January 11 shows that the frequency and duration of cold wave events was higher during La Nina years than in El Nino years between 1982 and 2020. La Nina is the other phase of the ENSO phenomenon and generally brings colder temperatures and more rainfall to India.
The scientists from India and Brazil analysed data on normal and intense cold wave events, classified on the basis of their intensity. They found the intense events to be tied to warming in the Arctic region.
According to experts, the Arctic region is warming at a rate much faster (three to four times) than the rest of the world. This primarily because of warming from the excess greenhouse gases in the atmosphere due to human activities.
The cold days and nights in north India may soon give way — first to early heat waves in March and April for the region and then heavy rainfall in the pre-monsoon season due to El Nino.
“I would expect heat waves in the usual spots of states like Uttar Pradesh, Bihar, Jharkhand and so on. But the northwest should see some heavy pre-monsoon rain because of the Arabian Sea warming. But March-April will see heat waves over the northwest including Mumbai, I think,” said Murtugudde.
“The lack of sufficient snowfall is definitely a concerning thing for hill states. This is because snow and ice reflect the incoming solar radiation, helping the land surface to remain cool. Thus, if the snowfall activity continues to remain subdued in February, hill states could witness above normal maximum temperatures,” Akshay Deoras, a research scientist at the National Centre for Atmospheric Science and Department of Meteorology, University of Reading, United Kingdom, told DTE.
“For other regions of the country, it is a bit early to estimate if the lack of snowfall will have an impact on the summer season and heat waves,” Deoras added.
“Having said so, the presence of El Nino is likely going to cause a warmer-than-normal summer season in India—this has happened in the past. However, it will be important to see if the western disturbance activity rejuvenates in the summer season or not, since that would cause a wetter and cooler than normal summer season such as in 2023,” Deoras concluded.
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