Characteristics of convective storm activity during the warm season over Anhui Province based on radar mosaic climatology and the possible causes

In order to understand the radar climatology characteristics of convective activity over Anhui Province, the climatological distribution and influencing factors of convective activity during the warm season (May-September) were investigated using Doppler radar mosaic data from five Next Generation Weather Radars and ERA5 reanalysis data between 2015 and 2020. Results indicate that: (1) There are obvious inter-monthly variations and spatial differences of convective activity during the warm season. The convective activity peaks during the Meiyu period, with the highest frequency in June and July, followed by May and August, and the lowest in September. The region with the highest convective in July and July is mainly distributed in the southwest-northeast direction. (2) It is found that the diurnal variation of convective number is bimodally distributed in summer (June-August), with the main peak in the afternoon and a subpeak in the early morning. In June, the peak convective activity mainly occurs in the early morning, which is related to the strengthening of low-level southwest airflow from night to early morning, and thus enhancing the moisture flux convergence in Anhui. In July, the peak convective activity appears in the afternoon, with a subpeak in the early morning. Note that the main peak is stronger and the duration is longer, which is related to the enhancement of convective available potential energy in Anhui in July. The second peak in early morning is also caused by the strengthening of the low-level southwest airflow, which is similar to that in June, but the intensity is weaker. Convective activity in August exhibits a single peak in the afternoon with the most significant diurnal variation, which shows a typical afternoon thermal convection type.