Establishment Of Thunderstorm Cloud Feature Dateset And Characteristics Of Thunderstorm Activity Over Land And Adjacent Seas Of China

Thunderstorm clouds yield lightning discharges and are often accompanied by damaging weather;therefore,they are important concerns for weather monitoring and forecasting.At present,the research on the thunderstorm activity in China is deficient;and the available thunderstorm cloud dataset with high temporal-spatial resolution and big spatial coverage is rare.In this study,the black body temperature(TBB)product and the cloud classification(CLC)product provided by the Fengyun-2E(FY-2E)satellite and the lightning location data from the World-Wide Lightning Location Network(WWLLN)were combined together to establish a thunderstorm cloud feature dataset(TFD).Based on this dataset,we investigated the characteristics of thunderstorm activity over the land and adjacent seas of China,and further analyzed the difference of WWLLN lightning activity from the traditional knowledge over the Tibetan Plateau(TP).The following results have been achieved.(1)A TFD is established.Thunderstorm cloud is determined as at least one WWLLN lightning is in the area with TBB ?-32? or its fitted ellipse.The parameters including time,location,cloud area,TBB features and internal strong convective cores(the continuous areas with TBB ?-52?)are obtained to form the TFD.(2)The characteristics of thunderstorm activity and thunderstorm cloud structure over China's land and adjacent seas are revealed.Thunderstorms are most active over the South China,Southwest China,TP and South China Sea(SCS).There are obvious differences in thunderstorm activity between land and sea.The peak of monthly variation occurs between June and August over the land,while there are two peaks over the SCS: May and the months after August,respectively.The lower the latitude,the later the second peak appears.The peak of daily variation occurs in the afternoon over land and occurs in the morning over SCS.The spatial distribution of thunderstorm cloud area generally shows large value in the east and small value in the west.Thunderstorm clouds over the seas obviously have larger average area than those over the land.In diurnal variations,the thunderstorm cloud area reaches peak in the afternoon over the SCS and night or morning over the land.The number of strong convective cores inside the thunderstorm clouds in the SCS and TP is larger,and their diurnal variation hits the peak in the afternoon to evening.The ratio of the strong convective core area to the thunderstorm cloud area is the greatest in the SCS,followed by the southern China.(3)Expose the characteristics of extreme thunderstorm clouds over the land and adjacent seas of China.The extreme thunderstorm clouds include the lighting cluster where the lightning frequency is in the top 10%.Extreme thunderstorms are more active over the SCS and Southern China.The peak of monthly variation occurs from June to September,and the peak of daily variation occurs in the afternoon but later than that of the thunderstorm activity in land areas except for northeast and north China.The area and the number of strong convective cores inside the extreme thunderstorm clouds are larger in the SCS and TP.As for the ratio of strong convective core area to the extreme thunderstorm area,it is greatest over the SCS,while it is relatively small over the TP.(4)Some new understandings on the spatiotemporal distribution of lightning activity over the TP have been obtained.The differences between the spatiotemporal distributions of lightning activity suggested by the WWLLN and Lightning Imaging Sensor(LIS)are revealed.The spatial distribution of lightning activity between WWLLN and LIS is different in the northeast and southwest TP.TBB data from the FY-2E satellite(as a proxy of deep convection)and thunderstorm-day data support the spatial distribution of the WWLLN lightning more.For seasonal variation,the main and second peaks of WWLLN lightning are August and September,respectively,while the main and second peaks of LIS lightning are July and June,respectively.The TBB data are more analogous to the LIS data,whereas the cloud-to-ground(CG)lightning data from a local CG lightning location system are closer to the WWLLN data.It is speculated that the different WWLLN and LIS observation modes may cause their data to represent different dominant types of lightning,thereby leading to differences in the spatiotemporal distributions of their data.The results may further imply that there exist regional differences and seasonal variations in the electrical properties of thunderstorms over the TP.