Application of Doppler Radar Data to the Landfalling Typhoon Saomai Simulation

The mesoscale model ARPS and its data analyzing system ARPS 3DVar developed by CAPS of Oklahoma university has a good potential to utilize in China. Using ARPS and its 3DVar assimilation system, the Doppler weather radar (CINRAD SA) reflectivity and radial velocity are assimilated. In order to test the effects of Doppler radar data on the initial field and on the forecast field, numeric study is carried out on super typhoon Saomai (0608) which lands at east China and causes a large damage. Comparison between experiments with and without radar data assimilation shows that Doppler radar assimilation can help obtain more realistic precipitation, wind and reflectivity structures within 6 hour initial time windows. The radar assimilation by ARPS 3DVar has the ability to improve the forecast on the mesoscale rain cell position and intensity. The improvement on typhoon track forecast is due to the effective adjustment of the typhoon vortex and eye structure by radar data assimilation. The result of precipitation forecast is improved significantly, mainly because of the physical quantities in assimilation test displaying typical characteristics of mesoscale system. However, there are some inadequate aspects still needing improvements in the stimulation of typhoon intensity.