Lightning activities on the Tibetan Plateau as observed by the lightning imaging sensor

Lightning flash activities on the Tibetan Plateau are investigated using observations from the lightning imaging sensor. About 95% of the flashes are found to occur during May to September with a single peak in the summer from June to August. There is substantial lightning activity in May on the plateau, especially on the southern and eastern plateau. The diurnal variation of the lightning activity shows a prominent peak from 1500 to 1700 LT for most of the plateau with earlier activity on the eastern and southern plateau and a delay on the western, northern, and central plateau. Few lightning flashes are observed between 0000 and 1000 LT. The highest flash density is found in the grassland central plateau with a value of 4.5 flashes km(-2) yr(-1), while the minimum is found in the semiarid western plateau with a value of 1.5 flashes km(-2) yr(-1). The optical radiance of flashes fits a lognormal distribution. More energetic flashes are found on the mountainous eastern and northern plateau, and weaker flashes are found on the wet southern and semiarid western plateau. A nonlinear relationship between lightning activity and monthly averaged convective available potential energy (CAPE) is found. The flash number per CAPE on the Tibetan Plateau is much larger than it is for other regions with prominent lightning activity (but low altitude).