不同类型大尺度环流背景下强对流天气的短时临近预报预警研究

利用2001-2014年共14 a的北京首都国际机场(以下简称机场)观测资料和Micaps高空及地面观测资料, 将发生在机场的雷暴日分为八类(即强雷暴、弱雷暴、湿对流、干对流、弱冰雹、强冰雹、冰雹大风和混合对流), 对每种类型雷暴的气候特征进行了统计研究, 得出如下结论:(1)机场雷暴以弱雷暴为主, 其次为干对流。弱雷暴和干对流在6月出现最多, 强雷暴和湿对流在7月最多, 弱冰雹出现在春末夏初及秋季, 而冰雹大风出现在6-7月, 混合对流仅在7月出现一次。(2)从500 hPa形势来看, 西风槽造成的雷暴过程最多, 其它为西北气流型。500 hPa为西风槽和低涡、西北气流时, 地面辐合线触发的雷暴最多, 其次为冷锋。500 hPa为横槽时, 冷锋触发的雷暴比例增加, 没有由地形辐合线触发的雷暴。而副高边缘和低压倒槽类型的雷雨过程, 触发系统主要为辐合线。(3)从月分布来看, 低涡和西北气流型造成的雷雨在6月最多, 但横槽和西风槽造成的雷雨出现最多的分别在7月和8月。西风槽、低涡和西北气流型造成的弱雷雨均最多, 其次为干对流。而雷暴的地面触发系统以辐合线最多, 主要出现在6月, 冷锋触发的雷雨主要集中在5-6月, 地形辐合线主要集中在7、8月。(4)横槽、西北气流型雷暴的日循环分布只有一个峰值, 分别出现在05-12UTC和08-14UTC, 但低涡和西风槽却有两个峰值, 主峰值分别出现在12-13UTC和08-17UTC, 次峰值分别在07-08UTC和00-01UTC。

General Features of Squall Lines in East C hina

Based on thunderstorm observation data at the capital international airport from 2001 to 2014, and conventional observation data, different thunderstorm types were classified.The results show as follows:(1) The thunderstorms happen at the capital airport are dominated by the weaker precipitation, next to the dry-convective thunderstorms.Moreover, the weaker precipitation and dry thunderstorms occur mostly in June.The heavy rainfall and wet convective thunderstorms occur mostly in July.The weak-hail appears in late spring, early summer and autumn.and The hail-with-gale thunderstorms appear in June and July, and the mixed convective thunderstorms appear only in July.(2) Thunderstorms occur the most frequently when there are westerly troughs at 500 hPa, followed by northwest-flow type.When there are westerly troughs, vortexes and northwest-flow at 500 hPa, the thunderstorms are the most frequently caused by convergence line, next to the cold front.When the transversal trough is at 500 hPa, the proportion of thunderstorms triggered by the cold front increased, but no thunderstorms triggered by the topographic convergence existed.When 500 hPa is at the edge of subtropical high and depression trough, the main trigger system on the ground is convergence line.(3) The thunderstorms caused by vortex and northwest-flow are mostly observed in June, but those caused by transversal trough and westerly trough mostly happen in July and August.Westerly trough, vortex and northwest-flow type mostly cause weaker thunderstorms, next to the dry-convective thunderstorms.The most frequent ground system that triggers thunderstorms is convergence line, which mainly concentrates in June, and followed by the cold front which concentrates in May and June, but topographic convergence lines only trigger thunderstorms in July and August.(4) The thunderstorm forming time for transversal trough is (05UTC-12UTC)2-3 h earlier than that of northwest airflow type (08-14UTC), and thunderstorms of vortex have a obvious peak at 12-13UTC, but the thunderstorms of westerly trough mainly concentrate at 8-17UTC.