Impact of AMSU and AMSR-E Measurements on Hurricane Prediction

While the skill of hurricane track prediction has been significantly improved during the past decades, the forecast of hurricane track and intensity is still a challenging task. An accurate initial vortex is one of essential factors for a successful prediction. Because of the lack of observation data over ocean, a hurricane initial vortex given by a global model is often too weak and sometimes misplaced. In this study, AMSR-E and AMSU microwave measurements are used to improve hurricane initial conditions with a 4DVAR assimilation system.

In the vortex initialization system, the atmospheric temperature profiles are retrieved from AMSU measurements by a 1DVAR scheme. The Sea-Surface Wind Speed (SSW) and Sea Surface Temperature (SST) under hurricane atmospheric conditions are derived with a physical based algorithm from AMSR-E measurements (Yan and Weng, 2005). A 4DVAR assimilation system is used to assimilate SSW and AMSU temperature data into hurricane initial vortex. By using the derived initial vortex, numerical simulations are performed to study the impacts of AMSR-E SSW and AMSU temperature data on hurricane forecast.

Eight hurricane cases were studied to assess the new vortex initialization scheme during 2005 hurricane season. It was found that the temperature structure under hurricane system was improved after incorporating the AMSU retrieved temperature. The AMSR-E measurements could provide more accurate SSW as verified against the best analysis data. The derived hurricane initial wind field showed reasonable vortex structure at all levels. Several 48-h hurricane model simulations were conducted to study the impacts of the AMSU and AMSR-E data on hurricane forecast. The detailed description of the scheme and results will be given in the presentation.