Deep tropospheric warming and mass flux, produced by the convection associated with organized tropical precipitation, is responsible on monthly and seasonal time scales for the presence of the Hadley and Walker circulations. In El Ni¿o--Southern Oscillation (ENSO) event years such as 1982--1983, in response to a perturbed sea surface temperature (SST) field in the equatorial Pacific Ocean, a major displacement in the ascending branch of these thermally direct, planetary-scale cells occurs. As the northern winter monsoonal rainfall develops over the tropical Pacific Ocean near the date line, normal precipitation over Indonesia and the Amazon and Congo river valleys is suppressed. Later, as the SST maximum approaches the coast of South America, flooding occurs over Ecuador. As a direct result of the induced anomalies in the general circulation, droughts are caused not only in Indonesia but also in northern Australia and in the northern subtropical Pacific Ocean along an axis from the Phillipines to Hawaii. The scanning multichannel microwave radiometer (SMMR) on board the Nimbus 7 spacecraft has been used to derive estimates of atmospheric water vapor.

The correlation between the satellite and verifying radiosonde data is better than 0.83 at all stations considered. The Earth radiation budget experiment flown on the same satellite observes the terrestrial net radiation, albedo, and outgoing longwave radiation (OLR). The OLR fields have been related to the 200-mbar divergence fields in the tropics during the First GARP Global Experiment with a correlation of 0.8. The derived relationship has been successfully extended to realistically map the irrotational flow and divergent circulation present in the troposphere both prior to and during the 1982--1983 ENSO event. Together, the two data sets yeild a joint estimate of the convergent flux of water vapor, a critical controlling parameter for organized convection. The derived water vapor flux convergences are analyzed during the recent El Ni¿o episode to map the evolution of the parameter, inferred deep convection, and estimated rainfall over regions impacted by the event. The inferred monthly rainfall amounts are compared with observations for 14 island and coastal stations in the Pacific Ocean. For the stations, linear models are developed that explain up to 71% of the variance of the signal.

For a rainfall model developed using the ensemble of stations, skill is demonstrated in describing the temporal and spatial evolution of the drought and flood anomalies present during 1982 and 1983. Over an equatorial belt extending from Indonesia to the coast of South America, positive rainfall anomalies reaching 40 cm month-1 are present. Due to changes in the Hadley and Walker circulations, these flood regions are bordered on all sides by rainfall deficits which are in excess of -20 cm month-1. ¿ American Geophysical Union 1987