The distribution of tropical cyclone precipitation: satellite estimates and flood mitigation

The devastation associated with recent hurricanes like Mitch, Floyd, and Georges highlights the significance of rainfall as a hazard of landfalling hurricanes. Unfortunately, accurate measurement and forecast of tropical cyclone (TC) precipitation remain critical problems and our knowledge of hurricane precipitation structure is limited. The pattern of devastation has raised questions about the adequacy of quantitative precipitation forecasts (QPF), the timing of maximum rainfall intensity, and the susceptibility of certain areas to floods. The Tropical Rainfall Measurement Mission (TRMM) satellite and field campaigns have given us the unprecedented opportunity to explore TC precipitation in great detail. This study examines rainfall variability in the 1998 Atlantic hurricanes and introduces a new approach to quantitative precipitation estimates (QPEs) by combining data from the TRMM Microwave Imager (TMI) and Precipitation Radar (PR), Special Sensor Microwave Imager (SSM/I), and Geostationary Operational Environmental Satellite (GOES) infrared (IR).

Use of satellite data is necessary since most of the tropics lack radar and rain gauge observations. The PR and TMI provide high spatial, but low temporal, resolution rainfall data. However, it is possible to develop relationships among simultaneous TRMM, SSM/I, and GOES IR observations. Such relationships will be useful for improving the rainfall estimates from the more frequently available geosynchronous IR data alone. In preliminary analyses, some IR cloud top characteristics have been identified with the most intense rainfall for different sectors and lifecycle stages of tropical cyclones. Such information is valuable for flood mitigation and for predicting cyclone intensity changes. In addition, the results of this study can be utilized in numerical model initialization and data assimilation. This study contributes to a broader effort to characterize tropical rainfall and reduce risk from floods.