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.
Highlights
It is well known that the diurnal variation of atmospheric parameters in the troposphere is a common phenomenon
This study aims to find out more details about the characteristics of precipitation diurnal variation over the Qinghai-Tibet Plateau (QTP) and its southern region using precipitation data issued by Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) observations in the summer, from 1998 to 2012
Based on TRMM PR observations over 15 years, the diurnal variation characteristics of deep convective precipitation (DCP) are analyzed in terms of the frequency, intensity, and maximum echo and its altitude, as well as the altitude of echo top, in order to improve the cognition of precipitation natures over the QTP
Summary
It is well known that the diurnal variation of atmospheric parameters in the troposphere is a common phenomenon. Haurwitz and Cowley [1] pointed out the existence of diurnal oscillation of surface pressure, Bonner et al [2] indicated strong diurnal variations of maximum wind in frequency in the low atmosphere, and Short and Wallace [3] revealed the variations of cloud cover during day and night. The diurnal variation of atmospheric parameters essentially reflects the dynamical nature of the atmosphere. Yang and Slingo [9] revealed that the intensity of continental deep convection generally reaches its peak in the evening, but there are differences in peak time over regions under the influence of sea-land breeze, mountain valley breeze, and the life cycle of the mesoscale convective system.
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