Effects of ATOVS Data Assimilation Schemes on the Simulation of Heavy Rain

In this paper, the Weather Research and Forecasting (WRF) model and its 3DVar assimilation system were used to examine a heavy rain event that occurred in Hefeng, Hubei Province, from 0000 UTC June 29 to 0000 UTC June 30, 2009, for which assimilation experiments were conducted with various schemes of Advanced Television and Infrared Observational Satellite (TIROS; ATOVS) including advanced microwave sounding unit (AMSU)-A, AMSU-B, and High-Resolution Infrared Sounder (HIRS) data. The effect on the simulation of heavy rain differed according to the assimilation of the three different types of ATOVS data. HIRS data produced a larger improvement on the simulation of heavy rain; AMSU-B data was inferior to the HIRS data; and the AMSU-A data appeared to show the poorest improvement. AMSU-A data produced the main effect on the assimilation result, which was close to the effect of assimilating the three types of ATOVS data simultaneously. The assimilation of the optimal combination containing AMSU-B and HIRS data was the best. Assimilation of various types of data led to varied effects on the initial field. AMSU-A data contributed mainly to the adjustment of the atmospheric temperature, whereas the effect of AMSU-B data was mainly at the middle and upper atmosphere. The assimilation of HIRS, resulted in the collaborative change on the humidity and wind field at the lower atmosphere that was most conducive to improvement of the precipitation simulation. When the model resolution was unchanged, best thinning resolution was noted.