The analysis of train effect features of a record-breaking severe rainfall in eastern region of Guangdong in August 2018

Using data of regional radar mosaic products, MICAPS, 6-hourly reanalysis data of CFSR with horizontal resolution of 0.5°×0.5°, and data of national meteorological observatories and regional automatic stations in Guangdong Province, the train effect features of an extremely severe rainfall event in Guangdong with a record-breaking rainfall of 1 056.7 mm within 24 hours in Gaotan of Huidong from 30 to 31 August 2018 is analyzed. The result is shown as follows. The train effect took place in the environment of a favorable atmospheric circulation induced by slowly moving monsoon depression. The most remarkable characteristic was that the high value of vapor flux divergence and potential pseudo-equivalent temperature mainly appeared in the boundary layer below 925 hPa. The wind direction in the boundary layer near Shanwei gradually shifts from southwest to south. The air current produced an upward movement of convergence around the central region of Shanwei. The storm cells of the severe rainfall moved along with southwest monsoon and the Lianhua Moutain from southwest to northeast. Surface mesoscale convergence line, the pulses of southwest-south airflows and the special terrain distribution triggered the generation and development of the train effect. The conditions presented above have resulted in the extremely severe precipitation breaking historical records in Gaotan.