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Temperature trends derived from Stratospheric Sounding Unit radiances: The effect of increasing CO 2 on the weighting function
Author(s) -
Shine Keith P.,
Barnett John J.,
Randel William J.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl032218
Subject(s) - weighting , stratosphere , depth sounding , environmental science , brightness , function (biology) , atmospheric sciences , altitude (triangle) , brightness temperature , meteorology , remote sensing , physics , geology , mathematics , optics , oceanography , evolutionary biology , acoustics , biology , geometry
Stratospheric Sounding Units (SSU) on the NOAA operational satellites have been the main source of near‐global temperature trend data above the lower stratosphere. They have been used extensively for comparison with model‐derived trends. The SSU senses in the 15 μ m band of CO 2 and hence the weighting function is sensitive to changes in CO 2 concentrations. The impact of this change in weighting function has been ignored in all recent trend analyses. We show that the apparent trends in global‐mean brightness temperature due to the change in weighting function vary from about −0.4 Kdecade −1 to 0.4 Kdecade −1 , depending on the altitude sensed by the different SSU channels. For some channels, this apparent trend is of a similar size to the trend deduced from SSU data but ignoring the change in weighting function. In the mid‐stratosphere, the revised trends are now significantly more negative and in better agreement with model‐calculated trends.