子計畫：台灣地區梅雨與颱風伴隨西南氣流之研究

This study examines the impact of dropsonde data on the simulation of a heavy rainfall event associated with strong southwesterly flow, using the observation system simulation experiments (OSSEs). The results show that WRF model performs well in simulating precipitation, southwesterly flow, moisture, temperature, and geopotential height in Southeast Asia when virtual dropsonde data over mainland China are assimilated through the ETKF system. When dropsonde data are added further over the South China Sea, the model can have better moisture and wind fields in the initial conditions, and thus obtain better rainfall simulation in terms of intensity and timing. It is thus suggested that dropsonde data should be released in the upstream area of southwesterly flow. Even a small amount of data can have great positive impact on the rainfall simulation in Taiwan. However, it is suggested that more dropsonde data covering a larger upstream region can provide more accurate forecasts of rain in Taiwan.