The Characteristics of the Atmospheric Components of Tropical Hydrological Cycle as Determined from Satellite

The complex ocean-atmosphere interaction in the equatorial western Pacific warm pool region holds the key to understanding global climate, particularly the El Nino/Southern Oscillation (ENSO) phenomena. Clouds, precipitation, and water vapor in the atmosphere, along with the ocean, complete the hydrological cycle that vividly participates in the air-sea interaction processes. The objectives of this study have been to retrieve the atmospheric components of the hydrological cycle using satellite observations and to diagnose the relationships between them, focusing on anomalous wind regimes. To retrieve atmospheric humidity from satellite, six microwave algorithms have been tested against conventional soundings in the tropics. The behaviors of the humidity variations have been found to be closely tied to the anomalous wind regimes in the warm pool region. A new satellite retrieval scheme for rainfall has been developed by combining the superior physical relationship between microwave radiance and rainfall and the abundant coverage of visible/infrared (VIS/IR) observations. The statistically based VIS/IR retrieval has been shown to increase its accuracy when the pixel-by-pixel retrievals are averaged in space and/or time. The retrieved rainfall rates yield a high bias compared to radar observations. Good agreement is found between the satellite retrieval and a shipborne optical rain gauge. The 5-day running mean satellite rainfall accumulation compares very well with that derived using large-scale moisture budget. Cloud properties and vertical structure are retrieved using both microwave and VIS/IR in the context of a satellite cloud classification scheme along with large-scale relative humidity analysis. The products of the retrieval are the number of cloud layers, cloud heights of single and multi -layer clouds, and cloud liquid and ice water contents. Cloud layering statistics agree well with the statistics obtained from a cloud co-occurrence climatology. It is found that cloud types, precipitable water, cloud structures and precipitating patterns all display very distinct behaviors between a westerly wind burst event and an easterly wind burst event during the TOGA COARE IOP.