BATHINDA: The winter season ended with temperatures higher than normal and rainfall lower than normal. The Western Disturbances continued to dodge the Himalayas, resulting in uneven and low precipitation. December resulted in a deficit of 65%, January had a rain deficit of 91% which is the second lowest since 1901 and February made up for the average deficit bringing it to 33%.
The rise in minimum temperatures continued, decreasing the diurnal temperature variation between night and day.
The research based consulting initiative Climate Trends analysing the weather patterns stated that December 2023 started on a warmer note, with no rain and snowfall, winter chill kept evading the entire north western plains as well as the hilly states. The month recorded 6.6 mm of rain against the normal average of 18.9 mm, resulting in a deficit of 65%. January saw four WDs, out of these only one WD (28-31 Jan) caused rain or snowfall over Western Himalayas and adjoining plains areas. However, the remaining three WDs were feeble and did not affect the region significantly. Northwest India recorded a mere 3.1 mm of rainfall against the normal 33.8 mm for the core winter month of January. This resulted in a rain deficit of 91%, which is the second lowest since 1901.
February had begun on a brighter note, with increased passage of WDs, bringing rain and snow across the hilly regions as well as the plains of Northwest India. In total, the month saw eight WDs, out of which six were active, which helped to improve rainfall deficiency for the country from 58% on January 31 to 33% on February 29. Despite the widespread precipitation, both the maximum and minimum temperatures have settled above normal average.
Changing Weather Trends, the rise in minimum temperatures: Global warming continues to push mercury to new levels. Initially it was maximum temperatures that registered the rise, but now minimum temperatures are also following the same route. The diurnal temperature variation, which is the difference between daily maximum and minimum temperatures, has decreased. February witnessed the second highest minimum temperature in the month since 1901, while January recorded the fourth highest minimum temperature since the IMD started keeping records.
The Role of El Niño: The oceanic phenomenon of El Niño is known for its truant nature that develops in the Pacific Ocean on average every two to seven years, and typically lasts up to nine to 12 months. An El Niño condition occurs when surface water in the equatorial Pacific becomes warmer than average. El Nino is invariably linked with below normal Monsoon, warmer winters and foggy days. Similar weather conditions were witnessed in the season so far.
“Though there is no rule book but if you have El Niño conditions, warm air increases near the tropical region and it pushes the cold air towards the north. Hence, it limits the passage of western disturbances in the Indian region. Due to large-scale features like the El Niño, minimum temperatures were higher-than-normal, making it a warm winter season in the country,” said Mrutyunjay Mohapatra, Director General, India Meteorological Department (IMD).
Another aspect that has contributed to the warming is the constant rise in ocean heating. According to a research by IMD, sea surface temperatures (SSTs) of the Arabian Sea and the Bay of Bengal are rising and there is strong positive correlation between land surface temperatures and sea surface temperatures suggesting significant contribution of warmer sea waters which may have important climatic implications over neighbouring regions. SSTs in the tropical latitudes have increased and as a response to this increase in ocean water temperature, tropical land surface temperatures as well as tropical tropospheric temperatures have also trended upward.
Erratic Western Disturbances (WD) ruled the season: The interplay of WDs with the topography of the western Himalayas determines the spatial and vertical distribution of precipitation. Hence, it becomes very important to read the role of climate change and its impact on WDs. According to scientists, WDs are getting lighter due to more convection and heat coming in due to increasing global warming.
“Based on the data from 1990 onwards, there is a trend that frequency of WDs is showing a decreasing trend for December to February months. The same is reflected in rainfall precipitation trends. Subtropical high is also shifting towards the north because of global warming, due to which WDs are also shifting north, hence affecting precipitation over Northwest India, which will also decrease. The sub tropics is the region which has high pressure belts where WDs develop and if this shifts north, the frequency, intensity and movement of the WDs will also be affected,” said Mohapatra.
“Heatwave in the Arctic region due to global warming have become quite frequent now. Hence, it is a major cause of concern as it directly impacts the circulations affecting the Asia region. Warming in the Arctic region pushes air upwards leading to the formation of a low-pressure area, which attracts circulations in the subpolar region. This has been the case last season and this season as well. The intensifying Arctic heatwave pulled up the weather systems including Western Disturbances northwards, making them travel in higher latitudes and thus, it did not affect the weather over India,” said Mahesh Palawat, Vice President – Meteorology and Climate Change, Skymet Weather.
Increase in glacial lakes: Potential disaster threat to the Himalayas Climate change and associated glacier recession have led to the formation of new glacial lakes and the expansion of existing ones across the Himalayas. Many pose a potential glacial lake outburst flood (GLOF) threat to downstream communities and infrastructure.
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