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Tuesday, April 21, 2009

C. L. Archer & K. Caldeira, GRL, 35 (2008), Historical trends in the jet streams

Geophysical Research Letters, 35 (2008) L08803; doi:10.1029/2008GL033614.

Historical trends in the jet streams

Cristina L. Archer and Ken Caldeira (Department of Global Ecology, Carnegie Institution of Washington, Stanford, CA, U.S.A.)

(Received 12 February 2008, revised 10 March 2008, accepted 14 March 2008, published 18 April 2008.)


Jet streams, the meandering bands of fast winds located near the tropopause, are driving factors for weather in the midlatitudes. This is the first study to analyze historical trends of jet stream properties based on the ERA-40 and the NCEP/NCAR reanalysis datasets for the period 1979 to 2001. We defined jet stream properties based on mass and mass-flux weighted averages. We found that, in general, the jet streams have risen in altitude and moved poleward in both hemispheres. In the northern hemisphere, the jet stream weakened. In the southern hemisphere, the sub-tropical jet weakened, whereas the polar jet strengthened. Exceptions to this general behavior were found locally and seasonally. Further observations and analysis are needed to confidently attribute the causes of these changes to anthropogenic climate change, natural variability, or some combination of the two.

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