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

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.

Keywords

• lightning
• thunderstorms and strong winds
• convection