Atmospheric jet streams are fast-flowing currents of air found approximately 10 km above sea level in the extratropical regions of both hemispheres. Because these jets influence regional weather patterns, there is great interest in understanding the factors that control their path, their strength and variations in both.
Theory tells us two different dynamical processes can give rise to such jets: heating in the tropics (thermal driving) and storm activity in the the midlatitudes (eddy driving). However, how important each process is in the real world is not well known.
Clouds along a jet stream over North America.
Theory and real-world jets
A new study by researchers at the Bjerknes Centre for Climate Research establishes a clearer link between theory and the real-world jets by identifying how variations in the driving processes affect the jets.
Eddy driving, which creates north-south shifts in the jet, is found to be important for both the Atlantic and Pacific jets; thermal driving, which creates changes in jet strength, is found to be equally important for the Pacific jet.
The results of this study provide an intuitive dynamical description of atmospheric variability in terms of actual fluctuations of the jets. In addition, they have the potential to help evaluate how the jets will respond to climate changes such as global warming.
The location of the jet stream is important for aviation. Commercial use of the jet stream can cut time off the flight. It also nets fuel savings for the airline industry. Within North America, the time needed to fly east across the continent can be decreased by about 30 minutes if an airplane can fly with the jet stream, or increased by more than that amount if it must fly west against it. Source: Wikipedia
Reference:
Thermally driven and eddy-driven jet variability in reanalysis
Camille Li and Justin J. Wettstein, (2012) Journal of Climate, Vol. 25, No. 5, pp. 1587-1596 http://dx.doi.org/10.1175/JCLI-D-11-00145.1