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热带气旋“巴威”北上引发辽宁省强降水的形成机制分析

Analysis on the formation mechanism of heavy precipitation in Liaoning Province caused by northward-moving tropical cyclone "Bavi"

  • 摘要: 利用地面观测资料、多普勒雷达资料、中央气象台热带气旋资料、数值模式预报资料以及全球再分析资料等,对北上热带气旋(TC)“巴威”引发的辽宁不同阶段降水特征和强降水形成机制进行分析。结果表明:(1)北上热带气旋“巴威”影响下,辽宁强降水过程分为TC远距离影响、外围螺旋雨带影响和TC本体影响三个阶段;前两个阶段辽宁均产生了对流性强降水,第二阶段对流强度弱于第一阶段,而第三阶段辽宁产生稳定性降水,降水强度偏弱。(2)TC北上过程中为辽宁降水提供持续的水汽和能量输送,前两个阶段均存在干冷空气作用和锋生强迫动力机制:TC输送的暖湿气流与辽宁境内干冷空气相互作用产生较强锋生,通过锋生强迫作用,第一阶段在对流不稳定下激发垂直对流,而第二阶段在湿对称不稳定下形成倾斜对流。TC本体影响阶段,TC强度快速减弱,辽宁位于TC热动力均减弱明显的偏西侧,同时缺乏适当的冷空气而锋生较弱,导致降水偏弱。(3)TC外围螺旋雨带影响时,强降水与850 hPa强锋生区域基本吻合,对TC降水预报具有一定指示作用。

     

    Abstract: The precipitation characteristics and the formation mechanism of heavy precipitation in Liaoning Province in different stages caused by the northward-moving tropical cyclone (TC) "Bavi", are analyzed based on the routine observations, the Doppler radar data, the tropical cyclone data from the Central Meteorological Observatory, the numerical model prediction data, and the global reanalysis data. The results are shown below. (1) The heavy precipitation in Liaoning Province can be divided into three stages: the stage of long-distance influence by the TC, the stage of outer spiral rainband influence by the TC, and the stage of TC body influence. In the first two stages, convective heavy precipitation occurred in Liaoning Province. In the second stage, the convective intensity was weaker than that in the first stage, while in the third stage, stable precipitation occurred in Liaoning Province with weak intensity. (2) The northward movement of TC "Bavi" provided continuous transport of water vapor and energy for precipitation in Liaoning Province. Dry and cold air effect and frontogenesis forcing were present in both the long-distance and outer spiral rainband influence stages. The strong frontogenesis developed in Liaoning Province due to the warm and moist air transported by the TC. Through frontogenesis forcing, vertical convection was formed under the convective instability in the first stage, and inclined convection was formed under moist symmetric instability in the second stage, respectively, which led to convective heavy precipitation being generated in both stages. At the stage of TC body influence, the TC degraded rapidly, and Liaoning Province was located at the west side of TC, where both thermal and dynamic forces weakened significantly. At the same time, it lacked proper cold air, and frontogenesis developed weakly, resulting in weak precipitation. (3) The heavy precipitation area in the stage of outer spiral rainband influence corresponded to the strong frontogenesis area at 850 hPa that is certainly indicative for forecasting of precipitation caused by the TC.

     

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