Jet streams are high altitude westerly wind system blows at a height of 6 to 14 km, with very high speed up to 450 km/h in wavy form at both hemispheres. As they encircle the poles they are called as ‘Circum polar wind system’ (Figure 6.20).
Although the jet streams flow at higher altitude they also influences the surface weather pattern of the Earth.
1. Creation of Polar vortex: Polar westerly jet stream will carry cold polar air masses towards temperate region which creates severe cold waves in North America and Eurasia during winter.
2. Sudden burst of South west monsoon:
Sudden withdrawal of polar westerly jet stream from Indian sub continent to northern part of Pamir, leads to sudden burst of South west monsoon into Indian Sub continent.
3. Late and early monsoon in South Asia: Rate of with drawl of polar westerly jet stream decides the onset of south west monsoon. Slower and faster rate of with drawl leads to late and early onset of south west monsoon.
4. Intensity of monsoon rainfall: The arrival of tropical easterly jet stream influences the intensity of south west monsoon. This leads to increasing intensity of rainfall during south west monsoon.
5. Bringing rainfall to India by western disturbances: Polar westerly jet stream carries rainy clouds from cyclones formed over Mediterranean Sea during winter towards India. These clouds piles up on the Himalayas and results in rainfall over the states of Punjab and Haryana. This assists in the cultivation of wheat in India.
6. Development of super cyclone: The condition at which the speed of the jet stream is transferred to tropical cyclone may leads to development of super cyclone.