Tuesday, 11 January 2005: 9:00 AM
Using TRMM to develop a tropical cyclone rainfall climatology model
A major obstacle to improving rain forecasts in tropical cyclones (TCs) is a lack of a comprehensive climatology of TC rain, i.e., a description of the distribution of rain in space and time. Few precipitation climatologies exist for TCs in the United States, and other TC basins have similarly limited climatologies. However, remote sensors such as those on the NASA Tropical Rain Measurement Mission (TRMM) satellite; in particular the microwave imager (TMI, 2A-12), are providing a first cut at a credible TC rain climatology globally. This climatology is precisely what is needed to develop a simple rainfall climatology and persistence (R-CLIPER) model, which can be used to validate numerical models and other rain forecast methods. A TRMM-based R-CLIPER model was implemented at the National Hurricane Center in September 2001 and run for the 2002-2003 hurricane season. This R-CLIPER uses a TMI rain climatology partitioned by storm intensity to provide the storm-centered mean rain rate distribution out to 500 km radius. An important use of the R-CLIPER is to provide a benchmark for the evaluation of other more-general quantitative precipitation forecasting techniques. Another use of the R-CLIPER is to assess the impact of tropical cyclones on global rainfall by using the R-CLIPER to generate estimates of yearly tropical cyclone rain rates for the global tropical cyclone best-track data. These yearly R-CLIPER estimates were compared to global totals of the TRMM-derived global rain estimates of the monthly tropical rainfall amounts (3B-43).