Hourly station‐based precipitation characteristics over the Tibetan Plateau

ABSTRACT Based on precipitation data collected from 100 surface stations on the Tibetan Plateau, the summer climatology of the hourly characteristics of precipitation events, including hourly frequency and intensity, frequency–intensity structure, diurnal circle, and duration, was comprehensively analysed. Both hourly frequency and intensity are high (low) over the southeastern (western and northern) plateau. In the Yurlung Zangbo River valley, which is located on the central southern plateau, the precipitation frequency is low and the intensity is high. The proportion of strong (weak) precipitation, in terms of frequency, is relatively large (small) in this valley, and similar features with respect to the frequency–intensity structure were also found for the northeastern plateau. In contrast, precipitation over the southern edge of the plateau is characterized by high frequency and low intensity, and the percentage of weak precipitation hours is higher than in other regions. Most stations over the plateau exhibit precipitation peaks either in late afternoon or around midnight. The late afternoon (midnight) peak is mainly contributed to by precipitation events that are short (long) in duration. These ‘short‐afternoon’ and long‐nighttime' types constitute the two major modes of precipitation over the plateau. Extreme events tend to begin in late afternoon, reach a maximum around midnight, and stop in the morning. The possible mechanisms are discussed. The quantity of available water vapour determines the geographical distribution of precipitation frequency through modulating the duration of precipitation events. High‐intensity events are related to well‐organized convective systems. The ratio of short‐afternoon and long‐nighttime precipitation is significantly influenced by local topography.