Publication Date:
2019-07-17
Description:
An intercomparison of radiation codes used in retrieving upper tropospheric humidity (UTH) from observations in the v2 (6.3 microns) water vapor absorption band was performed. This intercomparison is one part of a coordinated effort within the GEWEX Water Vapor Project (GVaP) to assess our ability to monitor the distribution and variations of upper tropospheric moisture from space-borne sensors. A total of 23 different codes, ranging from detailed line-by-line (LBL) models, to coarser resolution narrow-band (NB) models, to highly-parameterized single-band (SB) models participated in the study. Forward calculations were performed using a carefully selected set of temperature and moisture profiles chosen to be representative of a wide range of atmospheric conditions. The LBL model calculations exhibited the greatest consistency with each other, typically agreeing to within 0.5 K in terms of the equivalent blackbody brightness temperature (T(sub b)). The majority of NB and SB models agreed to within +/- 1 K of the LBL models, although a few older models exhibited systematic T(sub b) biases in excess of 2 K. A discussion of the discrepancies between various models, their association with differences in model physics (e.g. continuum absorption), and their implications for UTH retrieval and radiance assimilation is presented.
Keywords:
Meteorology and Climatology
Format:
text
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