Understanding Atlantic and Pacific jet stream fluctuations

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.

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.