安徽暖季对流活动的雷达气候学特征及影响因素

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

为了解安徽地区暖季对流活动的雷达气候学特征,利用多普勒天气雷达拼图资料和ERA5再分析资料,统计分析了2015—2020年安徽省暖季(5—9月)对流活动雷达回波的气候学特征及影响因素。结果表明:(1)安徽暖季对流活动存在显著月际变化和区域差异。对流在江淮梅雨期的6—7月活动最频繁,5、8月次之,9月最少。6、7月对流数量大值区分布呈西南—东北走向。(2)安徽夏季(6—8月)对流数量日变化呈午后主峰和清晨次峰的双峰特征。其中6月对流活动峰值出现于清晨,与夜间到清晨上游地区低空西南气流加强导致安徽地区水汽通量辐合增强有关。7月对流活动主峰出现于午后,清晨为次峰,其中主峰对流活动持续时间更长,这与7月安徽午后对流有效位能明显增强有关,清晨出现次峰的原因同6月类似,但强度弱于6月。8月对流活动特征为午后单一峰值,日变化幅度最显著,为典型的午后热对流型。

In order to understand the radar climatology characteristics of convective activity over Anhui Province,the climatological distribu⁃tion and influencing factors of convective activity during the warm season(May-September)were investigated using Doppler radar mosaic da⁃ta 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 Mei⁃yu period,with the highest frequency in June and July,followed by May and August,and the lowest in September.The region with the high⁃est convective in July and July is mainly distributed in the southwest-northeast direction.(2)It is found that the diurnal variation of convec⁃tive 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 enhance⁃ment 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.