Jet stream is the term used to describe a fast moving band of air, usually located in the high altitudes, at or just below the top of the troposphere. It is also described as the ‘upper level winds’ and could fluctuate slightly to the north and to the south for short periods. However, jet streams generally flow from west to east and have also been described as narrow bands of high flow winds flowing over the mid-latitudes.
Formation and maintenance of the jet streams
Jet streams can be formed and maintained due to many different reasons and among them, the temperature gradient, pressure gradient and the coriolis effect are the three most important. The temperature gradient is the result of warmth of the air near the equator and the gradual cold that take place in the air toward the poles. The gradients reverse at higher levels, and scientists believe that such reversal can give rise to the formation of jet streams.
In the absence of any other intervening factors, the middle layers of the atmosphere hold the most significant pressure gradient in comparison to the relatively low pressure gradients experienced in the bottom and the top layers of the atmosphere. Thus, in theory, the middle layers of the atmosphere should be home to the fastest flow. However, as a result of the earth’s rotation, it is impossible for such pressure gradients to remain within the middle layers of the atmosphere. Scientists have uncovered that due to the rotation of the Earth on its own axis, chunks of air from the northern hemisphere are being deflected into the right and therefore balance the pressure gradient. This phenomenon is known as the “coriolis effect” and is said to be responsible for the west to east flow of the jet streams as against a south to north wind direction.
Usefulness of jet streams
The study of jet streams has enabled scientists to predict weather patterns and storm flows in many parts of the world. For instance, the dull and wet summer weathers experienced in the UK in the years 2007, 2008 and 2009 have been attributed to the unusually low altitude of the northern or polar jet stream, which prevented the air from the Atlantic to move in. It is also interesting to note that the jet stream usually separates the warm and cold air. This knowledge would also be useful for the meteorologists to predict certain weather patterns on an ongoing basis. Furthermore, the main industrial use of jet streams can be attributed to the airline industry, as flying against a jet stream would be far more time-consuming and fuel-burning than flying with a jet stream. Thus, using jet streams would allow planes to cut down on travel time as well as the fuel costs incurred during most international routes.
