根据雷达反射率因子和径向速度产品演变特征,结合天气实况,对山东短时极端强降水反射率因子和流场结构进行了综合分析。结果表明,山东极端对流性强降水单体演变特征有4种类型:后向传播型、前向传播型、准静止型和再生型。后向传播型的主体降水回波产生的下沉气流与一侧的低层环境气流产生辐合上升运动,激发新的对流单体;前向传播型的主体回波后部下沉气流在地面附近辐散形成低层前沿的阵风锋,而低层暖湿入流经过阵风锋抬升进入到回波前沿的对流塔成为上升气流;准静止型回波常与中低层长时间维持的γ尺度气旋性涡旋有关;再生型回波的再生区内总是有新的单体不断生成,常与稳定少动的局地辐合区相对应。在大范围的强降水过程中,包含两种或以上演变方式。
Based on the radar data and extreme rainfall events,the reflectivity characteristics and airflow structures of extreme rainstorms occurred in Shandong Province were analyzed comprehensively. The results showed that the evolution of extreme rainstorms have four patterns: backward propagation, forward propagation, quasi-stationary and regeneration. For backward propagation pattern, the outflow from multicell cluster of storms interacted with the surface wind and formed areas of strong surface convergence on the upwind side, this strong convergence triggered new cells, thereby causing a cell propagation vector in the opposite direction of the steering flow. For forward propagation pattern, at low levels, cooler air diverging from the downdraft intersects the inflowing air along a gust front, creating a region of strong low- level convergence favorable for new updrafts. The quasi-stationary or motionless rainstorms often accompanied by γ-scale cyclone vortex sustaining long time in the middle-low level for the quasi-stationary pattern. As regards to regeneration pattern, regeneration zone where new cells were constantly inspired often correspond with stable and less moving local convergence zone. Two or more patterns were included in process of large scale heavy precipitation.
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