Jet streams are strong winds that generally blow from west to east at high altitudes near the tropopause. They form when warm and cold air masses meet, causing the warm air to rise and cold air to sink. There are two major types: subtropical jet streams, which circulate above 30-35 degrees latitude year-round; and polar front jet streams, which are more irregular and formed above the convergence of polar and tropical air masses. Jet streams have immense influence on local and regional weather conditions.

1. JET STREAMS
PREPARED BY
MUSHTHAQUE PK

2. Contents
 Definition
 Characteristics of jet stream
 Types of jet streams
 Subtropical jet streams
 Polar front jet streams
 Relation of jet streams with surface weather

3. Definition
 Jet stream is a strong winds that generally blows from west to east at high altitude
usually near the level of tropopause. They impact weather ,air travel and many other
things that take part in our atmosphere.
 According to World Health Organization (WHO),’ a strong narrow current
concentrated along a quasi-horizontal axis in the upper troposphere or in the
stratosphere characterized by strong vertical and lateral wind shear and featuring one
ore more velocity maxima is called a jet stream’.

4. What causes Jet Streams?
 Jet streams form when warm air masses meet cold air masses in the atmosphere.
 When earths warmer and cooler air masses meets each other the warmer air rises up
higher in the atmosphere while cooler air sinks down to replace the warm air.This
movement creates a air current.

5. Characteristics of Jet stream
 The circulation of jet streams is from west to east in a narrow belt.
 160-480 km wide.
 7.5-16 km height in the upper troposphere.
 Speed about 110 km/hr during summer and 190 km/hr during winter because during
winter the equator to pole temperature disparity is at its greatest thus the jet stream reaches
its maximum velocity.
 Generally their circulation is observed between poles and 20 degree latitudes in both the
hemispheres.
 Their circulation path is very wavy and meandering.

6. Types of jet streams
 The two major types are :
 The subtropical jet streams
 The mid-latitude or polar front jet streams

7. Subtropical Jet Stream
 They move in the upper troposphere to the north of the subtropical high pressure belt in
both the hemisphere that is above 30 degrees to 35 degree latitude
 Circulation from west to east and more regular than the polar front jet stream
 It flows through most of the year and is produced by the rotation of the earth.

8. Polar front Jet Stream
 They are formed above the convergence zone(40-60 lats)of the surface polar cold air mass
and tropical warm air mass.
 These move in easterly direction but are irregular.
 The thermal gradient is steepened because of convergence of two contrasting air masses.

9.  Other types:
 Polar night jet
 Barrier jet
 Coastal low level jets
 Valley exit jet
 African easterly jet

10. Relationship between the surface weather
 They have immense influence on local and regional weather conditions
 There is a close relationship between the intensity of temperate cyclones and jet streams.
Severe storms occur when jet streams interfere with surface wind systems.
 They also help in giving a relatively clear picture of the occurance of the events of El
Nino and La Nina.
 They are also used by aviators if they have to fly in the direction of the flow of jet
streams.
 The monsoon of South Asia is largely affected and controlled by Jet streams
 The region on earth below the trough is at low pressure and the region below ridge is at
high pressure.