jet streams and rossby waves, and their formation.
Table of Contents
Introduction
In this article, I will discuss the jet streams, types of Jet stream and their characteristics. These topics are very important for the students of geography. Also, Jet Stream is a hot topic for many entrance exams like UPSC, BPSC and other state exams. After reading this article, you will easily distinguish between the various types of jet streams formed in the atmosphere due to various factors.
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Jet streams
Jet Streams are the fast-flowing winds.They are narrow and meandering air currents in the atmosphere. They flow in narrow cores due to the strong pressure gradient. The speed of the wind is high at the center of the jet stream. The velocity of wind decreases away from the center. They occur near the Troposphere.
The length profile of a jet stream varies between 1600km to 3200km.
They follow the curved and meandering path due to the Coriolis effect.
These streams cover hundreds of kilometres in width and a few kilometres in depth.
The height of the jet stream decreases from the equator towards the pole since the height of the troposphere decreases from the towards the poles.
They do not flow a straight path.
These atmospheric circulations mainly flow a wavy path in the form of Rossby waves.
They are characterized by vertical and lateral wind shear.
They are characterized by great seasonal variations.
During the colder part of the year, they extend towards the equator.
In summers, they narrow down.
when were the jet streams discovered?
Meteorologist came to know about the existence of jet streams during the 2nd World War when the American jet was obstructed by the flow of these meandering waves during the bombing mission over Japan.
why do they move faster during the winters?
These winds have high velocity during the winters because of the steep horizontal temperature gradient.
How Jet streams are formed?
The origin of these atmospheric circulations is associated with the temperature gradient between pole and equator. This gradient induces a westerly component to flow aloft.
Where they normally located?
The Jet stream is found in the upper-level westerlies, where the temperature gradient or pressure gradient becomes stronger. This happens in the vicinity of the polar front and subtropics.
What is the significance of jet streams?
There is a close relationship between the intensity of mid-latitude cyclones and jet streams.
Due to these fast-moving winds, the cyclones become stronger and stormier.
When the jet streams are positioned above temperate cyclones, they yield more precipitation than normal.
Jet streams sometimes break through the tropopause and enter into the Lower Stratosphere.
The stratosphere develops cirrus clouds by injecting some of the water vapour by the jet streams.
The monsoon of South Asia is largely affected and controlled by jet streams.
Types of Jet stream?
Jet streams are broadly divided into four types. They are classified based on their location and metrological properties.
Polar front jet stream
Subtropical jet stream
The tropical easterly jet stream
Polar night jet stream
Somali jet stream or cross-equatorial jet stream
Polar front jet stream
The polar jet stream was discovered by Rossby and this jet stream is also known as the primary jet stream.
Polar front jet streams are formed above the convergence zone (40⁰-60⁰ latitude) of the surface polar cold air mass and the tropical warm air mass. Here the thermal gradient is steep due to two contrasting air masses.
Polar jet streams move from west to east direction.
They follow an irregular path.
They may encircle the entire globe.
Subtropical westerly jet stream
Subtropical jet streams are found in the upper troposphere just to the north of subtropical high-pressure belt i.e. above 30⁰-35⁰ latitudes.
They originate at the meeting point of Hadley and Ferrel cell.
The subtropical jet stream exists due to the increase in velocity. This velocity is induced by the conservation of angular momentum.
They occur as an air parcel and move towards the poles from the equator.
Subtropical jet streams are found at a higher altitude as compared to polar front jet streams.
They move from west to east direction in a more regular manner.
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