Jet streams are strong fast meandering narrow currents flowing in the upper troposphere. These are geostrophic westerly winds, which are developed when air masses of different temperatures meet. They usually extend from 20 degrees latitude to the poles in both hemispheres. Jet streams play a significant role in altering the global and regional climate.

• Effect of Jet streams on climate of India:
  • Western Disturbances in North India: The upper jet is responsible for steering of the western depressions [Western Disturbances] from the Mediterranean Sea. The southern branch of the jet stream exercises a significant influence on the winter weather conditions in India. winter weather conditions in India. Winter rain in north-western plains and occasional heavy snowfall in hilly regions are caused by these disturbances. These are generally followed by cold waves throughout the whole of northern plains.
  • Winter Monsoon: During winters the dry winds from high-pressure areas in north-western India which bring cold waves start blowing towards the low-pressure area of the Bay of Bengal. They take up the moisture from Bay of Bengal and pour down as Winter Monsoon along the coast of Tamil Nadu.
  • Indian Monsoon (Southwest Monsoon): With the beginning of summer in the month of March, the Subtropical Jet Stream (STJ) starts marching northwards and weakens. Whereas, an Easterly jet emerges over peninsular India with the northward migration of STJ. This creates low pressure over the Indian subcontinent, which in turn attracts moisture laden winds from southwest. The strength of the easterly jet decides the strength of SWM.
• Impact of Jet Stream on the global climate:
  • Polar Vortex: The jet stream band near the North Pole essentially confines the Polar Vortex. When the jet stream near the pole falls apart, the Polar Vortex can shift its position farther south and allow frigid air to spill toward mid-latitudes which affects the global weather system, bringing in snowstorms in North America. Heat Waves: Scientists are of the viewpoint that a form of double jet stream, when the band of wind splits into two, is responsible for almost all the rise in Western Europe’s heat waves, and about a third of the increased heat waves over Europe as a whole.
  • Ozone Depletion: Jetstream are also known to bring the ozone-depleting substances to the stratosphere hence aiding in the ozone layer depletion by acting as a vehicle.
  • Temperate Cyclones: There is a close relationship between the intensity of temperate cyclones and jet streams. They can either steer the storms away from land or towards populated areas, causing devastation.

Further, the position of the jet stream also plays a crucial role in determining the strength and duration of El Nino and La Nina.