Characteristics of different types of precipitation and their influences on drought and flood over Hainan Island in summer

Base on daily observational precipitation at 18 stations in Hainan province and the daily weather system in Hainan province during 1966—2018, the characteristics of different types of summer precipitation and its influence on summer drought and flood are analyzed. The result shows: (1) Tropical cyclone precipitation (TCR) is the most important precipitation type in summer over Hainan Island, accounting for 35.6% of summer precipitation (SUMR), followed by tropical convergence zone precipitation (ITCZR) accounting for 29.4%, and southwest monsoon trough precipitation (SWTR) and subtropical high edge precipitation (STHR) account for 15.3% and 14.7%, respectively. (2) The spatial distribution of different types of SUMR and their contribution rate to SUMR have different characteristics. (3) In summer, the frequency of TCR is the smallest, but its intensity is the largest over Hainan Island. The frequency of ITCZR is the largest, but its intensity is the second largest. Heavy rain and above are mainly caused by TCR and ITCZR. (4) In recent 53 years, SUMR in Hainan Island showed a weak increasing trend, which was mainly due to the significant increase of ITCZR. Conversely, SWTR and STHR contributed negatively to its increasing trend. The frequency of SUMR has a weak increasing trend, in which the frequency of ITCZR is significantly increased, the frequency of SWTR and STHR is significantly reduced, and the frequency of TCR is slightly reduced. The frequency of torrential rain and above has a weak increasing trend, the corresponding frequency of ITCZR has a significant increasing trend, and the corresponding frequency of the other three types have weak decreasing trends. (5) TCR and ITCZR have an important influence on the summer drought and flood over Hainan Island. Summer drought often occurs in the years with less TCR and ITCZR, but their influence on the summer flood has inter-decadal change, which results in the occurrence of summer flooding. It also leads to more precipitation in summer flooding years in this period.