In the upper layers of the mid-latitudes of the troposphere, near the tropopause, very fast blowing winds are called “Jet Streams”. These are strips of narrow, windy and fast currents. They keep on rotating around the earth. Their width ranges from 40 to 160 km. and thickness is from 2 to 3 km. Their speed is more than 120 km. per hour. Their speed is more intense in winters.
The status of these wind currents varies according to the weather. The path of jet stream shifts towards.the poles in the summer and towards the equator in the winter. The first information about these air currents was obtained during the World War II. After the end of the war, extensive research was done on them. Although weather scientists are unanimous on their places of origin and some other aspects, they are used favorably by the aircraft fliers by taking enough information about them.
Types of Jet Stream:
Jet Stream is divided mainly into the following two categories:
1. Sub – Tropical Jet Stream: Their location is found in both the hemispheres between 30° to 35° latitudes near the tropopause. It flows throughout the year. Their origin is due to the rotation of the earth. This rotation of the Earth produces maximum motion in the atmosphere above the equatorial zone. As a result, the above – mentioned wind streams in the equatorial zone move upwards towards north and down wards in the south and start blowing at a faster speed .
These wind currents are deflected on the right side of the Northern Hemisphere due to the Coriolis force and to their left side in the southern hemisphere. These same wind streams reach approximately 30° latitude and become sub-tropical jet stream.
2. Latitudinal or Polar Front Jet Stream: Their origin is due to heat and is closely related to polar front. Their position is between 40° to 60° latitude in both hemispheres. Their condition is more variable than the Sub-Tropical Jet Stream. In summer, they move towards the poles and they shift towards the equator in the winter season. These two types of jet stream are shown with the help of the following diagram.
Importance: Although the concept of jet stream has not yet been fully understood, however, they have a significant impact on seasonal conditions. These air streams have an important role in creating, inducing and causing fierce weather events such as cyclones, anticyclones, monsoons, furious winds and storms.
