Assimilation Experiments of Different Types of ATOVS Data on Simulation of a Snowstorm Weather in Northern China

Based on the advanced microwave sounding unit( AMSU- A),AMSU- Band high resolution infrared sounder( HIRS) data from advanced television and infrared observational satellite( ATOVS),conventional station data,TRMM 3B42 data and NCEP reanalysis data,the experiments of assimilating different types data on simulation of a snowfall process occurring in Northern China from 2 to5 March 2007 were carried out by using Weather Research and Forecasting( WRF) model and its 3DVAR assimilation system,the effect of assimilation to three types of ATOVS data on simulation of the snowstorm process was discussed. The results showed that compared to the positive effect of conventional data assimilation on simulated intensity and center position of precipitation,the improvements of assimilating AMSU- A or AMSU- B data on precipitation were less,while that of assimilating HIRS data was very significant. The simulation of assimilating AMSU- A and AMSU- B data had a fewer improvement on rainfall,while the assimilation of AMSU- B,HIRS data and conventional observation data to WRF model could effectively adjust the distribution of wind field and moisture field,so as to significantly generate the moisture convergence in precipitation center and adjacent areas over the lower level of troposphere,which was very beneficial to improve the precipitation simulation.