| Based on the TRMM data including Gridded lightning climatology data 3B43 precipitation data and Precipitation Features data from University of Utah), this study examines the climatological characteristics of lightning activities and features of precipitation cloud,over the Qinghai-Tibet Plateau. The main results are as follows..The largest densities of lightning are located over the central and northeast parts of the plateau, with the maximum lightning density over the central plateau reaching to 6.2 fl km-2 yr-1. Nevertheless, the strongest precipitation occurs over the southeast part of the plateau where the value is universally above 800 mm year-1. Both the lightning activity and precipitation move westward on May and then retreat on September over most parts of the plateau, while the strong lightning activity over the northeast of the plateau move little. Unlike the lightning activity which features center of large density, the precipitation show a cascade change from southeast to northwest. In chosen specified areas, the lightning and precipitation show parallel changes in general, including their active periods from May to September and single peak patterns. Except for the west and southeast parts of the plateau, the peak months of lightning and precipitation in other areas are same. The geographic distribution of the rain-yield per flash(RPF) is then investigated and exhibits that the minimum RPF appears over the central and west parts of the plateau, ranging from 5×107 to 7×107 kg fl-1, and the large RPF, having the value above 1×109 kg fl-1, appears over the area going along the Himalayas and stretching to the southeast part of the plateau and the area located in the north of the plateau and near to the Kunlun Mountains.The area of PFs with lightning is an order of magnitude larger than that of the PFs without lightning. Horizontal area of PFs with lightning is generally above 1400 km2 over the northeast of plateau, while the minimum is below 500 km2 over the southeast( central in 29°N, 97°E). In the plateau, cloud height of PFs with lightning is 2-4 km higher than the PFs without lightning. The maximum cloud height of PFs with lightning is over south-central plateau with the value above 12 km, and minimum height is less than 10 km near the Zangnan district. The maximum height of 20 d BZ radar reflectivity over the plateau is similar and slightly smaller than that over the plain to the south of Himalaya region, but the maximum height of 40 d BZ radar reflectivity over the plateau is bigger than that over the plain. PFs with lightning over west and northeast plateau have larger mean lightning density than other regions.Over the main part of plateau, the proportion of PFs with lighting to the total PFs is big in the afternoon and peaks during the Beijing time of 16:00-20:00, while the minimum proportion occurred during 08:00-10:00. But over Zangnan, the maximum proportion of PFs with lightning occurred in midnight. The vertical and horizontal scales of the precipitation cloud with lightning both increase around the midnight and decrease around the noon, but over Zangnan, the PFs with lightningtend to be the largest during 08:00-10:00. Except for the Zangnan and northeast parts of the plateau, the peak months of vertical and horizontal scales of PFs with lightning are all occurred in July. Nevertheless, they both show double-peak structure over Zangnan, with main peak in April and minor peak in August. About the occurring possibility of maximum radar reflectivity, the peak occurred at 7 km over northwest, north and south part of the plateau, 6 km over the northeast of the plateau and 2 km over Zangnan.The PFs with lightning over the most part of the plateau are in the largest probability to have the area between 100-300 km2, while the value for those over Zangnan is between 500-800 km2 and above 2000 km2. The maximum heights of 20 d BZ and 40 d BZ radar reflectivity over the main part of the plateau are most likely betwwen 10-11 km and 7-8 km, respectively. The corresponding values over Zangnan are 7-8 km and 5-6 km, respectively. |
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