子計畫:台灣地區豪大雨定量降水預報技術之研究(I)

This project used WRF model to study the heavy rainfall case on June 2 2017. Nine physics combinations, including 3 microphysics schemes and 3 cumulus parameterization schemes, were used in WRF simulations to test which combination performed the best in quantitative precipitation forecast (QPF). The results show that the WRF model with Goddard microphysics scheme and New Tiedtke cumulus scheme produced the best rainfall forecasts. The second part of the project was to examine the impact of ETKF (ensemble tranform Kalman filter) data assimilation on rainfall simulations. It is found that the setting of using 10 cycles of ETKF data assimilation produced the best QPF. We also found that the run with model initial time set at 1200 UTC 1 June 2017 performed the best among several other choices. The last topic of this project was to exmaine the relationship between rainfall and wind and moisture fields using 32-member ensemble simulations. It is found that southwesterly flow played an important role on the rainfall of this case.