Blog Archive

Saturday, April 26, 2008

Changes in the Troposphere, Jet Streams, and Tropical Belts

BLOGGER'S NOTE: A commenter on the realclimate blog has recently left links to 3 abstracts of interest and concerning changes in the temperatures, locations, and winds of the troposphere and stratosphere.

Nature Geoscience 1, 12-13 (2008). DOI: 10.1038/ngeo.2007.53

Atmospheric science: Raising the roof

Tiffany A. Shaw1 & Theodore G. Shepherd1

  1. Tiffany A. Shaw and Theodore G. Shepherd are in the Department of Physics, University of Toronto, 60 Saint George Street, Toronto M5S 1A7, Canada.

The atmosphere's lowermost 10 km have long been assumed to be almost solely responsible for weather and climate on Earth. Emerging evidence points to the layer above as an important influence on surface winds and temperatures on seasonal to decadal timescales.


Science, 26 May 2006. Vol. 312, No. 5777, p. 1179. DOI: 10.1126/science.1125566

Enhanced Mid-Latitude Tropospheric Warming in Satellite Measurements

Qiang Fu,1,2*
Celeste M. Johanson,1 John M. Wallace,1 and Thomas Reichler3

The spatial distribution of tropospheric and stratospheric temperature trends for 1979 to 2005 was examined, based on radiances from satellite-borne microwave sounding units that were processed with state-of-the-art retrieval algorithms. We found that relative to the global-mean trends of the respective layers, both hemispheres have experienced enhanced tropospheric warming and stratospheric cooling in the 15° to 45° latitude belt, which is a pattern indicative of a widening of the tropical circulation and a poleward shift of the tropospheric jet streams and their associated subtropical dry zones. This distinctive spatial pattern in the trends appears to be a robust feature of this 27-year record.

1 Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195, USA.
2 College of Atmospheric Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.
3 Department of Meteorology, University of Utah, 135 S 1460 E, Room 819 (WBB), Salt Lake City, UT 84112-0110, USA.

* To whom correspondence should be addressed. e-mail:


Nature Geoscience 1, 21-24 (2008)
Published online: 2 December 2007. DOI: 10.1038/ngeo.2007.38

Widening of the tropical belt in a changing climate

Dian J. Seidel1, Qiang Fu2, William J. Randel3 & Thomas J. Reichler4

Some of the earliest unequivocal signs of climate change have been the warming of the air and ocean, thawing of land and melting of ice in the Arctic. But recent studies are showing that the tropics are also changing. Several lines of evidence show that over the past few decades the tropical belt has expanded. This expansion has potentially important implications for subtropical societies and may lead to profound changes in the global climate system. Most importantly, poleward movement of large-scale atmospheric circulation systems, such as jet streams and storm tracks, could result in shifts in precipitation patterns affecting natural ecosystems, agriculture, and water resources. The implications of the expansion for stratospheric circulation and the distribution of ozone in the atmosphere are as yet poorly understood. The observed recent rate of expansion is greater than climate model projections of expansion over the twenty-first century, which suggests that there is still much to be learned about this aspect of global climate change.

  1. NOAA Air Resources Laboratory, Silver Spring, MD, USA
  2. University of Washington, Department of Atmospheric Sciences, Seattle, WA, USA
  3. NCAR, Atmospheric Chemistry Division, Boulder, CO, USA
  4. University of Utah, Department of Meteorology, Salt Lake City, UT, USA

Correspondence to: Dian J. Seidel1 e-mail:


Geophysical Research Letters, Vol. 35 (2008) L08803. DOI: 10.1029/2008GL033614

Historical trends in the jet streams

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


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.

Received 12 February 2008; accepted 14 March 2008; published 18 April 2008.


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