AIRS impact on precipitation analysis and forecast of tropical cyclones in a global data assimilation and forecast system

Abstract

The impact of assimilating quality-controlled Atmospheric Infrared Sounder (AIRS) temperature retrievals obtained from partially cloudy regions is assessed, with focus on precipitation produced by the GEOS-5 data assimilation and forecasting system, for three tropical cyclones: Nargis (April 27 - May 03, 2008) in the Indian Ocean, Wilma (October 15–26, 2005) and Helene (September 12–16, 2006) in the Atlantic. It is found that the precipitation analysis obtained when assimilating AIRS cloudy retrievals (AIRS) can capture regions of heavy precipitation associated with tropical cyclones much better than without AIRS data (CONTRL) or when using AIRS clear-sky radiances (RAD). The precipitation along the storm track shows that the AIRS assimilation produces larger mean values and more intense rain rates than the CONTRL and RAD assimilations. The corresponding precipitation forecasts initialized from AIRS analysis show reasonable prediction skill and better performance than forecasts initialized from CONTRL and RAD analyses up to day-2.