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Source: The post is based on the article “Here is the science behind unseasonal rains and hailstorms that flattened crops in India” published in Down To Earth on 27th March 2023.
What is the News?
Large parts of the country experienced hailstorms which were also accompanied by torrents of rain. The hail and rains have led to extensive damage to standing crops in many states, such as Maharashtra, Rajasthan and Punjab.
What are the reasons for these unseasonal rains and hailstorms?
Firstly, the rainfall and the storms were caused by multiple western disturbances (WD) and many troughs, which are extended low-pressure areas, formed due to the interaction of the WDs and associated systems with winds blowing in from the east, mainly the Bay of Bengal.
Secondly, a warming Arabian Sea could also be responsible for the intense storm activity and rain.
Thirdly, India Meteorological Department(IMD) also cited a strong subtropical westerly jet stream, a band of winds that circles the subtropical regions of the planet in the upper layers of the troposphere, as a reason for the storm activity.
– This was aided by the incursion of moisture-laden winds from the Bay of Bengal and the lowering of the freezing level in the atmosphere, which helped in the formation of hail.
What is Western Disturbance(WD)?
A Western Disturbance(WD) is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northern parts of the Indian subcontinent, which extends as east as up to northern parts of Bangladesh and Southeastern Nepal.
The meaning of WD lies in its name: The disturbance travels from the “western” to the eastern direction.
– Disturbance means an area of “disturbed” or reduced air pressure.In the term “extra-tropical storm”, storm refers to low pressure.“Extra-tropical” means outside the tropics.
Impact of WD: A WD is associated with rainfall, snowfall and fog in northern India.Upon its arrival in Pakistan and northern India, clouds along with rain and snow also arrive.The moisture which WDs carry with them comes from the Mediterranean Sea and/or from the Atlantic Ocean.
