Question

What are jet streams and how do they affect the climate of India?

Answer 1

Hint: The term ‘jet’ gives us an idea that these are a kind of fast flowing current. In order to know whether it is a current of wind or water, we need to figure out what affects the climate significantly- water current or wind current.

Complete answer:
Jet streams
They are the fast flowing, narrow, and meandering air currents in the atmosphere of Earth. They generally are located near the altitude of the tropopause and are westerly winds (flowing west to east) due to the Coriolis Effect (movements of water and air currents induced due to the rotation of the earth).
An air current is a flowing movement of air within a larger body of air; they flow in the layers of air surrounding the Earth. They are formed due to the uneven heating of the Earth by the sun. As the warmed air expands due to heating it becomes lighter than the surrounding air; thus, it rises and creates a warm air current. Cooler and heavier air then steps in to replace the arisen warm air thereby forming a cool air current. Jet streams are the air currents found in the highest part of the atmosphere.
Indian Monsoon Mechanism and the Role of SubTropical Jet Streams
1. The jet streams impact the onset of monsoon which depends upon the upper air circulation dominated by SubTropical Jet Streams (STJ). The south west monsoon in India is directly related to the tropical easterly stream.

2. The north east monsoon or more commonly called the winter monsoon is related to the subtropical westerly Jet Stream. It is a cold wind which pushes downwind to the surface thereby creating a high pressure on the surface.

3. Then the dry winds from this high pressure area which is in the north western part of India, start blowing towards the low pressure area or the Bay of Bengal. These winds are also responsible for the cold waves flowing in winter in the northern part of the country including UP and Bihar.

4. After reaching the Bay of Bengal, the westerly jet streams form the cause of north east monsoon and as this wind reaches the coast of Tamil Nadu, it causes rainfall due to the humidity received from the Bay of Bengal.

Note:
Jet streams are characterized by specific wind motions that are responsible for generating strong vertical shearing action, which is largely responsible for clear air turbulence. They are also one of the strongest winds in the atmosphere and their speed ranges from 129 to 225 kilometers per hour, but they can reach more than 443 kilometers per hour. They are relatively faster in winter due to the striking temperature differences between tropical, temperate, and polar air currents.