The mechanisms of the evolution of a Mei-Yu frontal rain band revealed from multiple Doppler/Polarimetric radar observation in the torrential rain event on June 11, 2012

On June 11 , 2012, a Mei-Yu front was approaching northern Taiwan, a line echo with wave pattern appeared when this east-west oriented rain band was about 100 km north to the northern tip of Taiwan island. Meanwhile the strong low level southwest wind was detected to the west coast of the island. This system brought over 500 mm rainfall to northern Taiwan within 8 hours. The numerical weather predictions were not able to forecast the three stages movement and the extreme rainfall. The purpose of this study is to utilize the Doppler radar network data near northern Taiwan to study the dynamical reasons for the evolution and movement of this torrential rain event. Through a variational multiple Doppler wind synthesis algorithm by Liou et al.2012, the three dimensional winds at different time stages are retrieved. The wind fields will be further applied to the calculation of the perturbation pressure and temperature fields. The changes of the vertical motion and the new cell propagation will be studied in detail. The interactions between the low level jet, the Mei-Yu front and the high terrain will also be discussed. A C-band polarimetric radar had observed the whole life cycle of this system, it will provide bounty information to study the micro-physical features associated with the evolution of this intense convective system.