一次强冰雹天气环境场及卫星云参数特征分析

Analysis of the Environmental Field and Satellite Cloud Parameter Characteristics of a Severe Hailstorm

摘要:

运用高空和地面逐小时常规观测数据以及FY-4A卫星产品，对2023年6月26日延安一次强冰雹过程环境场和云参数演变特征进行分析。结果表明：（1）此次强对流过程为高空冷平流强迫类，大气层结“上干冷、下暖湿”，地面辐合线触发不稳定产生大范围雷暴；（2）此次过程受高度组织化的中β尺度对流系统影响，TBB值的陡降能够提前20 min以上预警冰雹。TBB降至-32 ℃以下时降雹开始，TBB降至-70 ℃以下大概率预示有大冰雹；（3）成熟阶段的雷暴云团前沿云顶高度梯度大值区与100或200 hPa云区上风方气压梯度大值区对应着降雹区，云顶高度达到10 km以上则是降雹开始的重要条件；（4）成熟的雷暴云主体为冰云，上风方有卷云、混合云和过冷水云的过渡区，下风方为多层云；（5）对流初生产品能提前识别出雷暴云的初生位置，并预示其增强过程。

Abstract:

Using hourly high-altitude and ground conventional observation data, as well as FY-4A satellite products, we analyzed the characteristics of the environmental field and cloud parameter evolution associated with a severe hailstorm in Yan'an. The results show that: (1) The strong convective process was characterized as a cold advection forcing type at high altitude, with the atmospheric stratification described as "dry and cold aloft, warm and humid below", and the ground convergence line triggered instability, leading to widespread thunderstorms. (2) The process was influenced by a highly organized medium-β scale convective system, and the steep drop in TBB values provided an early warning for hail occurrence more than 20 minutes in advance. Hailfall began when the TBB dropped below -32 ℃, and values below -70 ℃ were likely indicative of a hailstorm. (3) The high value area of cloud top height gradient at the front of the mature thunderstorm cloud cluster and the high value area of pressure gradient on the upwind side of the 100 or 200 hPa cloud area correspond to the hail area. The cloud top height exceeding 10 km was an important condition for hailfall onset. (4) The main body of mature thunderstorm cloud was composed of ice clouds. On the upwind side, a transition zone of cirrus, mixed and supercooled water cloudswas observed, and multi-layered cloud structures on the downwind side. (5) The convective initiation product can identify the incipient location of thunderstorm clouds in advance to some extent and predict the enhancement process of these clouds.