Evaluation of the distribution of subtropical free tropospheric humidity in AMIP-2 simulations using METEOSAT water vapor channel data
Résumé
In the framework of the Atmospheric Model
Intercomparison Project (AMIP) phase 2, we have
established a diagnostic of the free tropospheric humidity
(FTH) distribution using METEOSAT data over the 1984–
1995 period for 14 climate models. The methodology of
evaluation follows a two step ‘‘model-to-satellite’’ approach.
First the raw METEOSAT ‘‘Water Vapor’’ radiances are
simulated from the model profiles of temperature and
humidity using the RTTOV-7 radiative transfer model.
Second, the radiances are converted into FTH using the
same coefficients as in the satellite product offering a direct
comparison. The analysis is focused on the dry subtropical
areas observed by METEOSAT: the Eastern Mediterranean
and the tropical South Atlantic Ocean. Most of the models
reproduce the observed seasonal cycle both in terms of
phasing and magnitude, despite an overall moist bias. A few
models are in close agreement with the satellite data. The
magnitude of the satellite estimated inter-annual variability is
also generally captured by models. Again, a small subset
of models shows close agreement with the observations.
This comparison suggests general improvements of the
models with respect to the AMIP-1 simulations.
Domaines
Océan, Atmosphère
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