Abstract:Based on the data from June 2009 to May 2011 over the Tibetan plateau, the temporal and spatial distribution of lightning is analyzed. Results show that the average value of lightning intensity was 61.89 kA; the negative ground flash took up 78.2% of the total; and the average of negative ground flash intensity was 55.97 kA. The positive ground flash took up 21.8% of the total, and the average of negative ground flash intensity was 83.14 kA. The lightning flashes were mainly positive ground flashes, which took up 73% before rainy season. The positive ground flashes took only 9% during the rainy season. The daily variation of lightning frequency showed the obvious single peak pattern, with the high frequency period in 15:00-21:00 (the peak at about 17:00) and the low frequency period in 03:00-12:00. The lightning density distribution had obvious regional difference. The high density areas of lightning were the mid eastern Naqu, western Changdu, eastern Rikaze, and Shannan. The negative flashes had two high density centers: Jiali and Langkazi. The Cuona was also a positive high density center. The lightning intensity was higher in winter and lower in summer. The monthly average intensity was greater than 50 kA. A probability equation is set up according to the lightning intensity, the positive and the negative flash lightning intensity, and the corresponding cumulative frequency. The fitting rate between the measured values and the calculated is higher than 0.99.
