Impacts Of Mhs Data Assimilation Of Tibet Plateau On Lower Reaches Rainfall Forecasts

The Tibetan Plateau has a significant impact on the precipitation in the lower reaches. Forecasted precipitation with assimilated satellite data in plateau is often closer to the actual situations. Using Gridpoint Statistical Interpolation (GSI) system and The Weather Research and Forecasting Model (WRF), three experiments were designed to evaluate the impacts of MHS data assimilation of Tibetan Plateau on lower reaches rainfall forecasts. The results showed that the assimilation of satellite MHS radiance can improve the accuracy of the prediction of precipitation intensity and precipitation zone in the lower reaches. A preliminary analysis of the reasons showed that the MHS data assimilation affected the initial water vapor fields, such that the model had better humidity conditions at the initial stage. The assimilation of conventional wind data increased the wind speed over the plateau. The interaction of water vapor and wind fields increased the accuracy of precipitation forecast in the study case.