陇东两类夏季雷暴的活动特征及影响因素分析

Activity Characteristics and Influence Factors of Two Kinds of Summer Thunderstorms in Longdong

利用ECMWF-ERA5再分析资料、常规观测资料分析了甘肃陇东2009—2018年夏季雷暴活动特征及环境条件。结果表明:陇东年均雷暴日数为18.8~23.6 d,夏季雷暴占68.5%~74.7%。夏季雷暴主要分为偏北气流型和低槽影响型,其中偏北气流型以分散性干雷暴为主,较大的垂直温差、高空冷平流强度和近地面高温对雷暴发生具有显著影响;低槽影响型多伴有明显降水过程,显著影响因素为较高的低空温度、湿度和较强的不稳定能量。低槽影响型和偏北气流型雷暴分别占总数的30.5%和60%,这两种类型的雷暴更容易出现在陇东北部地区。低槽影响型雷暴呈逐月增加趋势,最大值出现在8月;偏北气流型雷暴呈单峰分布,最大值出现在7月。各站雷暴日数年际变化趋势在6、7月一致性较高;月雷暴日数均有3~5 a的变化周期,其中7、8月同步性较好。雷暴日数的月、年变化与相应类型主导因素相关明显。植被覆盖、气候带以及地形差异也对雷暴空间分布产生了重要影响。

Using ECMWF-ERA5 reanalysis data and conventional observation data,the summer thunderstorm activity characteristics and environmental conditions in Longdong,Gansu province from 2009 to 2018 were analyzed.The results showed that the average annual thunderstorm days in Longdong were 18.8-23.6 d,of which summer thunderstorm accounted for 68.5%~74.7%.The thunderstorms in summer were mainly divided into northerly airflow type and low trough influence type,of which the northerly airflow type was dominated by dispersive dry thunderstorm,large vertical temperature difference,high-altitude cold advection intensity and near surface high temperature had significant influence on thunderstorm occurrence.The low trough influence type was mostly accompanied by obvious precipitation process,on which higher low altitude temperature,humidity and strong atmospheric instability energy had significant influence.30.5%and 60%of the total thunderstorms were caused by low trough influence and northerly airflow respectively,which were more likely to occur in the north of Longdong region.The low trough influence type increased month by month,and the maximum value appeared in August.The northerly airflow type presented single peak distribution,and the maximum appeared in July.The interannual variation trend of thunderstorm days in June and July was relatively consistent,but there was a big difference in August.The monthly thunderstorm days had a 3~5-year change cycle,in which July and August had good synchronization,and there was a large deviation from June.The monthly and annual variation of thunderstorm days was significantly related to the corresponding types of dominant factors.Vegetation coverage,climate zone and terrain differences also had important effects on the spatial distribution of thunderstorm.