DIRECT COMPARISON OF METEOSAT WATER-VAPOR CHANNEL DATA AND GENERAL-CIRCULATION MODEL RESULTS

Following a model to satellite approach, this study points out the abi lity of the general circulation model (GCM) of the Laboratoire de Mete orologie Dynamique to reproduce the observed relationship between trop ical convection and subtropical moisture in the upper troposphere. Tho se parameters are characterized from Meteosat water vapor equivalent b rightness temperatures (WVEBT) over a monthly scale. The simulated WVE BT held closely resembles to the observed distribution. The pure water vapor features and the convective areas are well located and their se asonal variations are captured by the model. A dry (moist) bias is fou nd over convective (subsiding) areas, whereas the model globally best acts over Atlantic ocean than over Africa. The observed and simulated seasonal variations show that an extension of the ITCZ is correlated t o a moistening of the upper troposphere in subtropical areas. Those re sults imply a positive large scale relationship between convective and subsiding areas in both observation and simulation, and suggest the r elevance of our approach for further climatic studies.