How are the source of rainfall in the north-west part of India different from the rain experienced on the coastal area of the eastern India in winter??
Answers
The North West part of India receives rainfall primarily from the Western disturbances which originate over the Mediterranean sea.
The moisture in these storms usually originates over the Mediterranean Sea and the Atlantic Ocean.
They carry moisture usually in the upper atmosphere (unlike tropical storms where it is carried in the lower atmosphere).
In India, moisture is sometimes shed as rain when the storm system encounters with the Himalayas.
In the Himalayan region of India, monsoon current progresses from east to west. But the WDs move across north India from west to east, with consequent rise in pressure and cold pool of air in the rear.
Western disturbances which are the moisture laden cyclones originating over Mediterranean sea usually influence the weather of the north and north-western regions of India.
Due to the impact of an approaching western disturbance, the wind direction changes. The moist easterly wind which blows which increases the humidity levels and causes light rain in Northern India. They cause winter rains in the North western part of India.
The coastal area of the eastern India on the other hand receive rainfall from the North east trade winds., which blow from Bay of Bengal.
The Arabian Sea branch gradually advances northwards. It reaches Mumbai by 10th June.
The Bay of Bengal branch spreads rather rapidly over most of Assam. The normal date of its arrival at Kolkata is 7th June.
On reaching the foothills of the Himalayas the Bay branch is deflected westward by the Himalayan barrierand it advances up the Gangetic plain.
The two branches merge with each other mostly around Delhi to form a single current.
Both the branches reach Delhi more or less at the same time.
The combined current gradually extends to west Uttar Pradesh, Haryana, Punjab, Rajasthan and finally to Himachal Pradesh and Kashmir.
By the end of June the monsoon is usually established over most parts of the country.
By mid-July, the monsoon extends into Kashmir and the remaining parts of the country.
By this time it reaches Kashmir, it has shed most of its moisture.