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东北冷涡背景下两类强对流天气的雷达特征对比分析

Comparison of radar characteristics of two types of severe convective weather under the background of Northeast cold vortex

  • 摘要: 在冷涡发展的不同阶段,其不同象限会出现不同的强对流天气类型,为深化对冷涡系统影响下强对流天气形成机制的理解,精准识别不同类型强对流天气。本文利用常规观测资料、双偏振雷达数据及ERA5再分析数据,主要对东北冷涡背景下辽宁2020年8月31日强降水(简称为“8.31”强降水)和2021年9月10日大冰雹(简称为“9.10”大冰雹)强对流过程的雷达特征进行了对比分析,并比较不同类型强对流天气风暴的发展演变和微物理结构的异同,结果表明:(1) “8.31”强降水过程出现在冷涡发展阶段东南象限,强降水出现是由冷涡前部低空暖平流强迫引发的;“9.10”大冰雹过程出现在冷涡成熟阶段西南象限,冷涡后偏北气流携带高纬度地区的强干冷空气向南侵入,高空的干冷平流是造成层结不稳定增长的主要因子。(2) “8.31”强降水过程中低层暖湿强迫的发展与雷达基本反射率在垂直方向上的发展和Zdr柱的高度变化相对应,降水的增强过程伴随较显著的低相关系数(CC)梯度区和径向速度大值区等低层入流特征;“9.10”大冰雹出现前中层径向辐合先加强,随后向下发展,低层的径向辐合加强,配合上升运动(径向速度柱发展),与强垂直风切变等共同作用,使强风暴维持并加强;(3) 强降水出现位置与Zdr柱和中层最大的径向速度区相邻;而大冰雹则出现在中层最大的径向速度区,与Zdr环、Zdr柱和CC谷的位置重合,这些关键信息在短时临近预报预警中将有很好的指导作用。

     

    Abstract: At different stages of the development of the cold vortex, different types of severe convective weather occur in different quadrants. In order to deepen understanding of the mechanism of severe convective weather under the influence of the cold vortex system and to accurately identify different types of severe convective weather, this article uses routine data, dual-polarization radar data and ERA5 reanalysis data. The radar characteristics of the severe precipitation (referred to as "8.31" heavy rain) in Liaoning on 31 August 2020 and the large hail (referred to as "9.10" large hail) on 10 September 2021 under the background of the Northeast cold vortex are compared and analyzed, and the development and evolution of different types severe convective weather and the similarities and differences of the microphysical structure are compared. The results are as follows. (1) The "8.31" heavy rain process occurred in the southeastern quadrant during the development stage of the cold vortex. The development of stratification mainly related to strong warm and humid advection at lower levels. The "9.10" large hail process occurred in the southwestern quadrant during the stage of the cold vortex. The northerly flow behind the cold vortex carried strong dry and cold air from high latitudes to the south, and the cold advection at high altitudes was the main factor causing the increase in instability. (2) The development of low-level warm and moist forcing during the strong precipitation process corresponded to the development of radar reflectivity Z in the vertical direction and changed in the height of the Zdr column. The enhancement of precipitation accompanied by significant low correlation coefficient (CC) gradient zones and large radial velocity zones as low-level inflow characteristics. Before the production of large hail, the strong storm top first experiences strong divergence, which together with upward motion (radial velocity column development) and-level convergence (radial velocity convergence), interacted with strong vertical wind shear to help maintain and strengthen the strong storm. (3) The most severe weather phenomena in the two types of severe convective weather have a good correspondence with the weak echo region, Z-pillar and Zdr column, mid-level radial convergence, velocity convergence region, Zdr ring and CC valley, and these key information will have a good indication significance in the short-time forecast and early warning.

     

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