Jet Streams
Jet Streams - World Meteorological Oganisation (WMO) defines it as a strong narrow current concentrated along a quasi-horizontal axis (i.e., it is neither horizontal nor vertical, it is wave like) in the upper troposphere or in the stratosphere characterised by strong vertical and lateral wind shear and featuring one or more velocity maxima.
Characteristics of Jet Streams
- The jet streams exist for 1000s of KM in length covering the entire latitude and few 100s of KM in width.
- They normally blow from west to east.
- They are stronger in winter.
- The entire system follows the sun, changing its position from season to season.
- They follow zig-zag path like rossby waves.
Conditions which leads to the formation of jet streams
- The temperature difference between the two regions, i.e., tropical and polar or maritime & within the continental (local jet stream) results in difference in pressure gradient with altitude above different air masses, which results in strong winds between the two regions.
- Larger the temperature difference, stronger the winds blow.
- In winter, temperature difference between Temperate and Tropical zone is large, that's why jet streams are stronger in winter.
Types of jet streams
1. Polar Jet Streams -
- It is formed in the regions where temperate and polar air masses interact.
- They are irregular and discontinuous.
- They blow from west to east all across the globe.
2. Sub-Tropical westerlies Jet Streams -
- They are associated with temperature gradient at the poleward limit of Hadley cell.
- They blow from west to east all across the globe.
- They are more consistent and strong.
3. Tropical Easterlies jet streams -
- They are formed over India and Africa over summer due to the intense heating of Tibetan plateau and the desrt.
- They blow from east to west.
- They are associated with Indian monsoon.
- They are not present in Southern hemisphere.
4. Polar night jet streams/Stratospheric Sub-polar jet stream -
- They are above the Stratosphere over the polar region during the winters.
- They blow strongly from west to east and confines the cold and dry air of the polar regions with in the poles.
- They are also associated with the formation of Ozone holes.
5. Local jet streams
- They are formed due to the local thermal and dynamic conditions.
- Example - Somali jet stream of coast of East Africa.
Significance of jet streams
- Jet streams help in generation of cyclones and anti-cyclonic circulations on the surface.
- They affect and change the local weather conditions.
- They help in transportation of pollutants and its disposal in the regions where there is an accumulation of higher quantity of air pollutants and particulate matters.
(Divergence at upper troposphere → Vertical upliftment of air → sucks pollutants
Example - In India, Sub-tropical westerlies jet stream which is strong in winter sucks the pollutants from Delhi. That's why pollution level in December is low in Delhi)
- They help in the movement of aircraft in the upper troposphere and also save fuel.
- They help in intensification of temperate cyclones.
- Monsoon of South Asia is controlled by Sub-tropical westerlies jet stream as well as Tropical easterlies jet stream.
(Jet Stream - convergence in the upper troposphere → formation of high pressure zone on the surface → Anti-cyclonic circulations
Also, convergence → Subsidence of air → no cloud formation & restricts precipitation)
(Divergence in the upper troposphere → formation of low pressure zone on the surface → Cyclonic circulations
Also, Convergence → Convection of air → formation of clouds and Precipitation)
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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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