Weather is the state of the atmosphere which describes the degree or intensity to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. It is driven by air pressure, temperature and moisture differences between one place and another. Jet stream is one of the natural phenomena that directly affect our weather.
What is Jet Stream?
The Jet stream is very fast blowing air current system in the upper atmosphere (9 to 18 km). Its speed is maximum (340 km/h) in the middle part.
In other words, it is fast flowing, narrow, meandering air currents in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). The path of the stream have a meandering shape which may start, stop, split into two or more parts, combine into one stream, or flow in various directions including opposite to the direction of the remainder of the jet.
How Jet Stream impact on the global weather system?
The jet stream works as a cover over the Earth which affects the weather of the lower atmosphere. It is located at the boundary between the troposphere and the stratosphere at a level called the tropopause. It is an atmospheric highway located at the level where jets cruise. This stream spread over the three belts over the hemispheres of the globe which are scattered from just north and south of the equator to just south or north of the poles. When the jet stream flows from west to east then it is often distorted with northward bulges and southern plunges.
For Example: During winter season the upper air westerly jet streams are positioned in Asia. These are bifurcated in two branches due to Tibet Himalayan obstruction. North branch blows north of Himalayas and the Tibetan Plateau. Southern branch blows south of the mighty mountains.
During summer season as sun falls vertically over the Tropic of Cancer the polar surface high pressure is weakened and upper air circum polar whirl shift northward as a result of which the upper air westerly jet are also withdrawn from southern slopes of the Himalayas. The removal of jet stream to north of the Tibetan plateau results in reversal of the curvature of How of free air to the north and north-west of the subcontinent. This event may well be the trigger that sets off the ‘burst’ of the monsoon.
Hence, we can say that the jet stream band near the North Pole essentially confines the Polar Vortex. When the jet stream near the pole fall apart, the Polar Vortex can shift its position farther south and allow frigid air to spill toward mid-latitudes which will affects the global weather system.