洞庭湖区域雷暴大风分型及预报分析研究

使用S波段双偏振天气雷达资料，对2021年5月15日洞庭湖区一次强对流过程的多单体风暴阶段和飑线阶段分阶段进行了分析，并重点对前阶段的超级单体风暴I2进行了分时段分析，结果表明：(1) I2初始发展时段，水平反射率因子(Z_H)＞55 dBz区域、差分反射率因子(Z_DR)柱(＞2.5 dB)扩展至湿球零度层WBZ高度，对应区域差分相移率(K_DP)较大(＞1.7 °·km^-1)、相关系数CC在0.9~0.99，说明该时段降水相态是以夹杂着大雨滴的水凝物为主。(2) I2冰雹碰并增长时段，Z_H强度和发展高度急速增长，垂直液态水含量VIL出现明显跃增，Z_H强中心(＞60 dBz区域)扩展至-10℃高度以上，对应的Z_DR降至低于0，Z_DR柱(＞2.5 dB)扩展至-10℃高度；CC下降、K_DP出现“空洞”，说明该时段降水以固态粒子为主，且处于增大时段。(3) I2成熟降雹时段，Z_H强中心(＞60 dBz)底部降至WBZ高度以下、CC局部低至0.8、对应区域存在Z_DR负值区、K_DP空洞，说明冰雹下落的拖曳作用削弱上升气流的强度，预示冰雹即将落地。(4)飑线阶段和多单体风暴阶段不同，飑线阶段K_DP值异常偏大、Z_DR大于1。(5)飑线阶段的极端大风发生前，55 dBz强回波、27 m·s^-1速度大值区扩展至1 km以下，强回波区域K_DP明显偏大，与强下沉气流相对应。另外，高空降水粒子在下降过程中融化导致的强降水拖曳作用加剧了极端大风的产生。

Synoptic situation classification and forecast analysis of thunderstorm in Dongting Lake

The multi-cell storm stage and squall line stage of a severe convective weather process over the Dongting Lake on 15 May 2021 in this study are analyzed mainly based on S-band dual-polarized doppler weather radar data. The study focuses on the analysis of the supercell storm I2 in the multi-cell storm stage. The results are as follows. (1) During the initial period of the I2, the strong echo area (the horizontal reflectivity factor, Z_H > 55 dBz) and the differential reflectivity factor (Z_DR) column (Z_DR > 2.5 dB) extend to Wet Blub Zero (WBZ) level, corresponding to the areas with large specific differential phase (K_DP) (> 1.7 °·km^-1) and large correlation coefficient (CC) (0.9-0.99). It indicates that during this period, the precipitation phase is dominated by water condensate mingled with large raindrops, and these supercooled raindrops provide hail embryos for the later hail development. (2) During the hail colliding-growth period of the I2, Z_H intensity and height increase rapidly, and vertically integrated liquid water content (VIL) shows an obvious leap increase. The strong-echo center (Z_H > 60 dBz) extends to the level of above -10 ℃. In the corresponding regions, the Z_DR drops below 0, the Z_DR column (Z_DR> 2.5 dB) extends to the level of -10 ℃, CC drops, and a