【摘要】 通过七次冰雹天气过程的分析,发现浙江地区大范围降雹过程之前,对流层中下层并不一定有大尺度辐合和上升运动,而是与边界层辐合却有着十分密切的关系.降雹前,边界层中都有辐合线存在,与此相应,有较强的质量和水汽通量辐合.无辐合线,则无大范围的冰雹天气发生.冰雹区的水汽通量散度垂直分布有明显特点,水汽辐合多集中于边界层内,辐合最大值在950百帕附近,850百帕以上辐合很小,甚至是辐散.还发现边界层辐合的强度与冷锋位置有关.更多还原

【Abstract】 Analysing seven large-area hail events in Zhejiaug, we have found that prior to the occurrence of events, the large-scale convergence and ascending motion are not necessary to have in the middle and lower troposphere. However, hail events are closely related to the boundary layer convergence. For all the seven cases, the convergence lines with stronger mass/moisture convergence in boundary layer are in existence prior to hail shooting. Large-area hail shooting event is unlikely to occur without the boundary layer convergence line. The averaged vertical profile of moisture flux divergence in hail shooting area has the following remarkable features: The moisture convergence is concentrated in the boundary layer with the maximum convergence existing around 950 hPa and the convergence above 850 hPa is so small that sometimes it becomes divergence. It is also found that the intensity of boundary layer convergence is related to the location of cold front.更多还原