Passive microwave observations of water vapor profiles during two ENSO events

A physical algorithm is used to retrieve water vapor profiles from Special Sensor Microwave Temperature-2 (SSM/T-2) data. Observations from the eastern Indian Ocean and tropical Pacific during the 1995-96 La Nina and 1997-98 El Nino are used to investigate the feedback between surface temperature and water vapor and to address Lindzen's hypothesis that an enhanced convective cycle leads to drying of the upper troposphere. The parts of the water vapor signal that are correlated with local SST and rainfall are removed in an attempt to isolate the effects of the large scale circulation from local thermodynamics. Regions of drying due to large scale effects in the middle to upper subtropical troposphere are found which correspond to increased rainfall at nearby portions of the Intertropical Convergence Zone, in support of Lindzen's hypothesis. Model-calculated and observed outgoing longwave radiation (OLR) differences will also be presented.