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Utility of Radiosonde Wind Data in Representing Climatological Variations of Tropospheric Temperature and Baroclinicity in the Western Tropical Pacific
 

Summary: Utility of Radiosonde Wind Data in Representing Climatological Variations of
Tropospheric Temperature and Baroclinicity in the Western Tropical Pacific
ROBERT J. ALLEN AND STEVEN C. SHERWOOD
Department of Geology and Geophysics, Yale University, New Haven, Connecticut
(Manuscript received 5 June 2006, in final form 27 February 2007)
ABSTRACT
The utility of the thermal wind equation (TWE) in relating tropospheric (850300 hPa) wind and tem-
perature on climatological time scales is assessed, based on data from 59 radiosonde stations in the western
tropical Pacific during 19792004. Observed long-term mean and seasonal variations closely obey geo-
strophic balance; incorporating additional (ageostrophic) terms yields negligible improvement. The authors
conclude that observed winds offer a useful constraint on the horizontal structure of monthly and longer
temperature variations (although the reverse is not true close to the equator where f 0). This conclusion
is also supported by general circulation model output.
Wind data show a slowing of the midlatitude jets in the Maritime Continent region since 1979, indicating
that tropical thicknesses and temperature have increased less than those poleward of 25N/S. This pattern
is consistent with Microwave Sounding Unit temperature trends in the region but is exaggerated south of
the equator in trends obtained directly from the temperature data. The latter are however sensitive to which
stations are used and how the data are averaged, and the discrepancy is fairly small in a homogenized
climatology from the Hadley Centre (HadAT). The discrepancy is most easily explained by spurious cooling
at stations in the near-equatorial western Pacific.

  

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

 

Collections: Geosciences; Environmental Sciences and Ecology