Jet Streams

• Jet streams are bands of high velocity winds, much like a river of fast flowing air, which usually flow from west to east.
• There are 2 jet streams in each hemisphere – the polar jet and the subtropical jet.
• They were not actually observed until 1943-44 during WWII when high-flying U.S. military aircraft encountered strong head winds near Japan which gave the aircraft a negative ground speed.
• The properties of fluid mechanics and the Coriolis effect influence the motion of the jet streams.
• Jet streams influence aircraft flight times by creating head and tail winds.

 

The Polar Jet Stream:-

• separates cold polar air from mid-latitude eddies
• is associated with the high and low pressure systems seen on weather maps
• is usually located at altitudes between 9-12 km above the Earth
• is constantly changing its intensity and location over a range of latitudes
• can reach wind speeds of 100 m/s (225 mph)

The Subtropical Jet Stream:

• separates the mid-latitude eddies from tropical air
• forms the poleward boundary of the Hadley Circulation which is considered the "prime mover" of energy in the Earth’s atmosphere
• flows at elevations of 9-13 km above the Earth
• usually stays at the same intensity between roughly 23.5° and 33° latitude