Lightning Activity on the Central Tibetan Plateau as Observed by Lighting Imaging Sensor

Lightning flash activities on the central Tibetan Plateau have been studied by using the Lightning Imaging Sensor (LIS) database from 1998 to 2002. The lightning activity shows a clear diurnal variation on the central Plateau. The lightning discharge is weaker on the Plateau than in other low-altitude continental regions because of the lower convective available poential energy (CAPE) on the Plateau. The CAPE is 12 times lower and the sensitivity of lightning activity to CAPE changes on the Plateau is 30 times more sensitive than other prominent low-altitude regions. INTRODUCTION The Tibetan Plateau exerts profound thermal and dynamical influences on the atmospheric circulation because of its high elevation and great dimension. In particular, the Tibetan Plateau plays a critical role in the onset of the South Asian summer. So far the investigation of lightning on Tibetan Plateau has not been conducted with modern detection tools. Nevertheless, the Plateau is usually covered by active cumulus convection in the summer and there are many thunderstorms, hailstorms, showers and convective clouds on the Plateau (Ye and Gao, 1979). The diurnal variation of convective activity has been studied by examining the cloudiness obtained from meteorological satellite images (e.g. Yanai et al., 1992) or weather radar (e.g. Qin et al., 1984, 1988; Uyeda et al., 2001). The study of lightning activity will be helpful to understand deep convection, the heating process and the water cycle on the Tibetan Plateau. DATA DESCRIPTION The lightning data come from the LIS database(Boccippio et al., 2000; Christian, H. J., et al., 1999) from 1998 to 2002 provided by the Global Hydrology and Climate Center (GHCC) at Marshall Space Flight Center in Huntsville, Alabama. The research region is focused to the central Tibetan Plateau which is the region with the most frequent lightning activity. The lightning flashes occurred in the 2.5o×2.5o square centered at Naqu (32oN, 92oE 4500m asl) have been used. Meanwhile, the lightning activity in Tibetan Plateau are compared with Jingzhou (30oN, 112oE 100m asl), Hubei province in the same latitude belt nearby and other regions. RESULTS 1. Seasonal variation of lightning activities on the Tibetan Plateau Figure 1 shows the seasonal variation of lightning as a percentage of the total flash number. Lightning activity can be found in any month from April to October with an increasing activity from April to June, and then an active flash period during the summer season (78% of flashes). A sharp decrease from August to October marks the end of 0 20 40 60 80 100 120 140 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Fl as h Nu mb er Fig. 1 Annual variations of lightning activities on the Central Plateau