Lightning Activities in China Offing Sea Area Observed by Satellite based Lightning Imaging Sensor

Using observation data of the optical transient detector and the lightning imaging sensor on satellites from April 1995 to April 2006, the spatial and temporal distribution of lightning activities in China offing sea area (including the Bohai Sea, the Yellow Sea, the East China Sea, the South China Sea and some parts of the Pacific in China's terrestrial sea) are statistically examined. The relationship between the lightning activities and the sea temperature is also studied by combing those data with the reanalysis data from the NOAA optimum interpolation SST. The result indicates that the average flash densities in China offing sea area is 3.39 fl·km^-2·a^-1, which is about 5 times higher than the global ocean average value. The high flash density areas are mostly in the boundary of the land and the sea, especially in the sea areas around the islands, indicating the difference of lightning activity between the sea alongside land and the ocean. The lightning activities in the Bohai Sea and the South China Sea are more frequent than those in the Yellow Sea and the East China Sea. There is a clear tendency that the flash density in China offing sea area decreases gradually with the increasing of latitude and the distance off the coast. The flash densities in the sea around the Taiwan Island and the Bohai Sea are the highest. The lightning activity is most frequent in summer, then spring, and in winter it is rare. The sea temperature in the black tide area is higher in winter and spring, and the lightning activity is more frequent than the East China Sea and parallel ocean sea areas, indicating that the black tide area is a strong lightning activity area. The annual and diurnal change of lightning activities in China offing sea area take on a similar changing trend as that on the land of the same latitude. For the lightning activities of the Bohai Sea and the East China Sea, there's one single peak, while in the South China Sea and the Yellow Sea, lightening activities take on the similar double peak trends as those in the land of subtropical zone. The lightning activities' annual change is obviously positively correlated to the sea temperature in China offing sea area. But the flash activity is insensitive to the annual change of the sea temperature, indicating that the sea temperature's annual change isn't the main cause for lightning activities' annual change.