Today we are going to discuss jet stream.
What is Jet Stream?
Jet Stream are the wind blowing with great velocity near the Tropopause. The jet stream are active in 150 km wide and 2-3 km thick transition belt.
The general velocity of these wind is about 150-200 km/hour. But the sometime the velocity at the core of jet stream is found to be 325km/hour.
Jet Stream are generally found in the North Hemisphere only. In the South Hemisphere, they are found over the South Pole, though they are found in the light Rossby Waves over other latitudes also.
Reason behind the origin of the Jet Stream is the difference in surface temperature and pressure gradient.
Types of Jet Streams:
Jet Streams are of four types-
1) Polar Night Jet Stream: These are found beyond the 60 degree latitudes in both the hemispheres.
2) Polar Frontal Jet Streams: These are found over the zone between 30 degree to 70 degree latitudes at a height of 9-12 km.
These are related to polar fronts and follow wave like inconsistent paths. The average velocity of this jet stream is 150-300 km/hr and average pressure is 200-300 mb. Since this jet stream was made known by Swedish scientist Rossby, it is called Rossby waves.
3) Sub-Tropical Westerly Jet Streams: These are found between 20 degree to 35 degree North latitudes at a height of 10-14 km. Their average velocity is 340-385 km/hr and average pressure is 200-300mb. The main reason behind their origin is the north-eastern flow of the air rising through the convection in the equatorial region in the Tropopause. These jet streams are responsible for bringing the western disturbances to India in the months from December to February.
4) Tropical Eastern Jet Streams: All the other jets follow a westerly direction, but, these streams follow the north-easterly direction. These jet streams are found in the zone of 25-35 degree latitudes. These jet streams originate in the North Hemisphere in the summers. This jet stream originate in a zone of 100-150 mb pressure at a height of 14-16 km. The average speed of this jets is about 180 km/hr. These are responsible for the origin of the Indian monsoon. Since, these jet streams are warm, they lift hot and humid surface air and cause convectional rainfall and in this way this jet stream is responsible for the bursting of monsoon in India.
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