南海雷暴大风时空分布及闪电和对流活动特征

Temporal and Spatial Distribution of Thunderstorms and Strong Winds with Characteristics of Lightning and Convective Activities in the South China Sea

  • 摘要: 利用2019—2020年风云四号气象卫星A星(FY-4A)多通道扫描成像辐射计(AGRI)提供的云顶数据和地基全球闪电定位网(WWLLN)提供的闪电数据,结合MICAPS气象观测站和海洋浮标记录的极大风数据,研究南海区域(5°~30°N,105°~125°E)71次雷暴大风过程的时空分布及其闪电和对流活动特征。结果表明:观测站记录的雷暴大风主要分布在南海北部;雷暴大风主要发生在5—9月,峰值出现在8月,3月发生次数最少;雷暴大风主要发生在07:00—12:00(北京时,下同),10:00频次最高,午后频次减少。雷暴大风闪电密度的极大值分布在广东南部近海区域,且闪电集中发生在距离观测站40~80 km半径范围内;孤立雷暴大风过程首次闪电跃变的发生时刻相对大风峰值时刻超前30 min至2 min。在对流特征方面,在雷暴大风风速峰值时刻,观测站处的云顶亮温为200~220 K,云顶高度为12.5~15 km。孤立雷暴大风云团云顶亮温最低值(即最强对流发生位置)与大风观测站点的距离平均为77.2 km,云顶亮温平均相差2.6 K。

     

    Abstract: Using the cloud top data provided by Fengyun-4A (FY-4A) multi-channel scanning imaging radiometer (AGRI) and lightning observations provided by the ground-based global lightning positioning network (WWLLN) during 2019-2020, combined with the meteorological and oceanographic data from MICAPS and extreme wind data recorded by buoys, the spatial-temporal distribution and convective activity characteristics of 71 thunderstorm and strong wind processes in the South China Sea are studied. Results show that the thunderstorms and strong winds recorded by the observatory are mainly distributed in the northern part of the South China Sea. Thunderstorms and strong winds mainly occur from May to September, with the peak in August and valley in March. Thunderstorms and strong winds mainly occur in the morning (0700-1200 BT), with the highest frequency at 1000 BT, a sharp decrease in the frequency in the afternoon, and the lowest frequency between 2100 BT and 2300 BT. The maximum value area of lightning density is distributed in the offshore area of southern Guangdong, and the lightning concentration occurs in the radius of 40 km to 80 km of the observation station. There is an obvious lightning jump in the isolated thunderstorms and strong winds process, and the occurrence time of the first jump is 30 min to 2 min ahead of the peak time of the wind, showing that the lightning activity is indicative of the peak of thunderstorms and strong winds. In terms of convection characteristics, at the peak moment of thunderstorms and wind speed, the cloud top brightness temperature at the location of the observation station is concentrated at 200-220 K, and the cloud top height is concentrated at 12.5 km to 15 km. The distance between the lowest brightness temperature value of isolated thunderstorms and strong winds cloud cluster (i.e., the location of the strongest convection) and the strong winds observation site (i.e., the location of the thunderstorms and strong winds) is 77.2 km on average, and the average difference of brightness temperature value is 2.6 K.

     

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