Abstract:Based on the precipitation data from automatic weather stations and ERA5 reanalysis data, case seletion and classification of synoptic circulation are carried out in this paper to study the warm-sector heavy rainfall in Huizhou during the first rainy season from April to June of 2003-2022. And a comparative analysis is conducted on characteristics of average synoptic circulation and ambient parameters between different types of warm-sector rainfall events. The results show that a total of 48 warm-sector heavy rainfall events occurred in Huizhou during the first rainy season in 2003-2022. Accroding to synoptic circulation, the selected warm-sector rainfall events are divided into three types, i.e., shear line (the first type), shortwave trough with low-level jet (the second type), and the edge of subtropical high with the entrance of low-level jet (the third type). By further comparing the average synoptic circulation between different types of warm-sector rainfall events, we reveal that Huizhou is under the control of the west wind flow and the southwest flow in the periphery of subtropical high at 500 hPa, except the second type of heavy rainfall. In low levels, there are double low-level jet (southwest low-level jet and boundary layer low-level jet) near Huizhou both in the second and third types of heavy rainfall, while in the first type of heavy rain, there is boundary layer low-level jet only to the south of the Pearl River Estuary at 925 hPa. The analysis of the ambient features indicates that the ambient parameters calculated based on ERA5 reanalysis are reliable and applicable. The second and third types of heavy rainfall are superior to the first type of heavy rainfall in moisture and energy conditions. But in terms of dynamic conditions, the vertical wind shear, and the static instability of the first type of heavy rainfall is considerably stronger than those of the other two types of heavy rainfall.