Evaluation of the distribution of subtropical free tropospheric humidity in AMIP-2 simulations using METEOSAT water vapor channel data

Hélène Brogniez (1) , Rémy Roca (2) , Laurence Picon (2)

1 CETP - Centre d'étude des environnements terrestre et planétaires
2 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

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

Hélène Brogniez, Rémy Roca, Laurence Picon. Evaluation of the distribution of subtropical free tropospheric humidity in AMIP-2 simulations using METEOSAT water vapor channel data. Geophysical Research Letters, 2005, 32 (19), pp.L19708. ⟨10.1029/2005GL024341⟩. ⟨hal-00159814⟩