The erratic behaviors of Western Disturbances have been in the news recently due to their effect on rainfall levels and temperature fluctuations in different regions of India. These weather phenomena originate from the Caspian Sea or Mediterranean Sea and are responsible for non-monsoonal rainfall in northwestern India, according to the India Meteorological Department (IMD).
Understanding Western Disturbances
Western Disturbances are essentially storms that have their roots in the Caspian and Mediterranean Seas. They are often referred to as an extra-tropical storm originating in the Mediterranean region and are areas of low pressure that bring sudden precipitation (rain, snow) and fog in northwest India.
The term Western Disturbance is derived from the fact that these disturbances move from the west towards the east. They travel at high altitudes on westerly jet streams, which are large ribbons of fast-moving winds moving from west to east across the earth. The term “disturbance” signifies an area with reduced air pressure. By nature’s balance, air in an area will attempt to normalize its pressure.
The prefix “extra-tropical” in “extra-tropical storm” denotes that the storm originates outside the tropical region. Consequently, Western Disturbances are associated with rainfall, snowfall, and fog in Northern India, bringing rain and snow to Pakistan and northern India. The moisture carried by these disturbances primarily comes from the Mediterranean Sea and the Atlantic Ocean.
Impact of Western Disturbances
Western Disturbances play a significant role in bringing winter and pre-monsoon rain, which contributes significantly to the Rabi crop growth in the Northern subcontinent. However, these disturbances aren’t always beneficial – they can also lead to extreme weather events like floods, flash floods, landslides, dust storms, hail storms, and cold waves which can have devastating effects on people, infrastructure, and livelihoods.
Recent Variations in Western Disturbances
In 2021, Delhi experienced its rainiest October in 65 years due to the Western Disturbances, with the Safdarjung weather observatory recording 122.5 mm rainfall against a normal of 28mm. There were also reports of excess rainfall in January and February of the same year. Conversely, there was no recorded rainfall in November 2021 and March 2022. Early heatwaves started in summer at the end of March 2022, and active western disturbances were absent from northwest India in March 2022. This resulted in high temperatures due to lack of cloud cover and rain.
Possible Causes of Variation
The increasing frequency of Western Disturbances can be attributed to a warming atmosphere, or global warming. These disturbances are essentially low-pressure areas. When it’s a feeble western disturbance, it lacks enough moisture for precipitation. As the atmosphere warms, there is less moisture available for precipitation.
Moreover, due to the warming atmosphere, western disturbances are being observed at higher elevations. Generally, they move in subtropical westerly jets, and now they are becoming lighter and moving higher, above 200 hectopascals. Experts suggest that these variations will have to be monitored over the next few years to determine the overall impact of climate change.
Western Disturbances thus play a critical role in the Indian climate and weather, impacting not just agricultural rhythms but also extreme weather events. Their recent erratic behavior calls for close monitoring and study, especially in light of ongoing climatic changes.
Last Modified: February 15, 2024