The Phenomenon of Diurnal Variations for Summer Deep Convective Precipitation over the Qinghai-Tibet Plateau and Its Southern Regions as Viewed by TRMM PR

Abstract

This study analyzed the diurnal variations of summer deep convective precipitation (DCP) over the Qinghai-Tibet Plateau (QTP) and its southern region. The results show that DCP is the main type of precipitation over the QTP. The precipitation intensity of DCP is less than 3 mm/h over the QTP, which is much lower than the precipitation intensity in non-plateau regions. DCP over non-plateau regions is related to the convergence of surface wind, but that over the QTP are not. The mean maximum echo of DCP is less than 26 dBZ over the QTP, less than in non-plateau regions. The mean altitude of maximum echo decreases from about 7.5 km in the western plateau to 6 km in the eastern plateau, while it reaches only 4.5–5 km in the non-plateau region. The DCP frequency peak occurs in the afternoon in the major area of the QTP including valley region. The peak time of DCP frequency is different from its intensity, and the former is 1 to 2 h earlier. Study also indicates strong diurnal variations in frequency, intensity, and the maximum echo over the QTP, which is consistent with diurnal changes of geopotential height fields of 500 hPa and 200 hPa.