"Jet Stream" & "Western Disturbance" - The Main Reason for Snowfall in Northern Part of Himalaya.
We all like snowfall for which we go to Kashmir, Shimla, Manali, Mussoorie, Auli etc in Winter. But, do you ever think, what is reason for snowfall in Winter ? How clouds form in Winter ?
Here is the answer :-
In Winter ( Nov to March ), The strong wind flows 6 to 12 kilometers above the ground in the north of the Himalayas, Middle East Asia, Tibet and China, called "Western Jet Stream". This Jet Stream flows from west to east.
In the winter, the direct sunlight shifts from the Equator to the Tropic of Capicorn (Southern Tropical), as of which the summer season happens in the Southern Hemisphere and the winter season happens in Northern Hemisphere.
In the month of November- December, due to the sunlight falling directly on Tropic of Capricorn, "Jet Stream" also changes its direction from north to south. When the jet stream comes from north to south then Himalaya creates obstruction in the passage of the jet stream and the jet stream is divided into two parts. 1. The 'northern branch' which flows in Tibet Side and the 'southern branch' which flows in north India.
The southern branch of the jet stream starts flowing from west to east in northern India. In fact, this Southern Branch of Jet Stream puts a significant impact on the weather of North India during the Winter Season. This southern branch of jet stream brings "Western Disturbance into North India and because of the western disturbance, rain falls in the plane area of North India as well as snow falls in the Mountain Area.
What is Western disturbances ? : -
Western disturbances is a tropical cyclone, which is born above the Mediterranean Sea in Europe in the winter season. Western disturbance starts flowing from west to east with the help of jet stream. This Tripocal cyclone has very good moisture content as it flows over the three major sea i.e. Mediterranean Sea, Black Sea and the Caspian Sea. When this tropical cyclone enters into India through Southern Branch of Jet Stream is called as “Western Disturbance” and it rains or snowfalls in the winter season in India. In fact, the rainfall or snowfall happens during the winter season in the Northern India can only be received by these moistured winds.
This Western Disturnance has good moisture and it brings snowfall in the mountainous terrain of India (Jammu and Kashmir, Himachal Pradesh and Uttarakhand), and rainfall in the northern region of India (Punjab, Haryana and Delhi). If, this cyclone has very good amount of moisture, then it rains upto West Bihar. As long as this tropical cyclone progresses from west to east, the amount of rainfall or snowfall goes down, This is the reason, Kashmir in India as well as Gilgit, Karakoram Range in Pakistan receives the maximum snowfall in comparison to Himachal and Uttrakhand.
Western Disturbances plays very important role for apple farming in Mountains as well as for "Rabi Crops i.e. wheat in plane area of North India.