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Warming maximum in the tropical upper troposphere deduced from thermal winds

Warming maximum in the tropical upper
troposphere deduced from thermal winds
Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA
*e-mail: robert.allen@yale.edu
Published online: 25 May 2008; doi:10.1038/ngeo208
Climate models and theoretical expectations have predicted that the upper troposphere should be warming faster than the surface.
Surprisingly, direct temperature observations from radiosonde and satellite data have often not shown this expected trend. However,
non-climatic biases have been found in such measurements. Here we apply the thermal-wind equation to wind measurements from
radiosonde data, which seem to be more stable than the temperature data. We derive estimates of temperature trends for the upper
troposphere to the lower stratosphere since 1970. Over the period of observations, we find a maximum warming trend of 0.650.47 K
per decade near the 200 hPa pressure level, below the tropical tropopause. Warming patterns are consistent with model predictions
except for small discrepancies close to the tropopause. Our findings are inconsistent with the trends derived from radiosonde
temperature datasets and from NCEP reanalyses of temperature and wind fields. The agreement with models increases confidence
in current model-based predictions of future climate change.
It has long been recognized that radiosonde temperature data
are affected by non-climatic artifacts due to station relocations,
observation time changes and radiosonde type or design changes1


Source: Allen, Robert J. - Department of Earth Sciences, University of California at Riverside


Collections: Geosciences; Environmental Sciences and Ecology