Understanding Atlantic and Pacific jet stream fluctuations
Published: 29/3 - 2012 Last updated: 6/6 - 2012
A recent study by Bjerknes Centre scientists demonstrates the link between observed fluctuations of atmospheric jet streams and the theoretical concepts that describe why jet streams exist.
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.
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
NASA Aerial Super Highway
Meandering around the planet like a rollicking roller coaster in the sky, the Northern Hemisphere's polar jet stream is a fast-moving belt of westerly winds that traverses the lower layers of the atmosphere. Animation: NASA/ Goddard Space Flight Center