A statistical analysis of hourly heavy rainfall events over the Beijing metropolitan region during the warm seasons of 2007–2014

Abstract

A statistical analysis of the spatiotemporal characteristics of hourly heavy rainfall (HHR) events and rainstorm days, defined as greater than 20 mm h−1 and 50 mm day−1, respectively, is performed using observations at 5‐min intervals from 155 automated weather stations (AWSs) over the Beijing metropolitan region (BMR) during the warm seasons of 2007–2014. Results show pronounced variability in the frequencies and rainfall amounts of both HHR events and rainstorm days across the BMR of less than 150 km width from the west to east. That is, higher‐ (lower) frequency HHR events with more (less) accumulated rainfall amounts take place in eastern Haidian and over the BMR's northeast mountains (west and northwest mountains). Many extreme rainfall and even record‐breaking events, in terms of the frequency, duration, rainfall amount and intensity, are found to occur in the regions of high‐frequency HHR events and rainstorm days. The frequency of rainstorm days with HHR events accounts for more than 50% of that of total rainstorm days over the BMR's plains and near the northeast mountains. Results also show that HHR events occur most frequently in late July, and typically peak during 1600–2000 LST. A comparison of the averaged surface meteorological variables and upper‐air sounding at 0800 LST between HHR and non‐HHR days reveals that the occurrences of the HHR events coincide with the distribution of surface warmer and more humid air as well as organized convergence in the presence of an unstable environment with surface south‐ to southeasterly winds, low‐level south to southwesterly flows and a deep layer of higher moisture content. These results suggest likely the positive influences of urban environment and mountain‐plain circulations on the generation of the HHR events, given favourable larger‐scale conditions.

Enhancement of the summer extreme precipitation over North China by interactions between moisture convergence and topographic settings

“…Sun et al (2015) inferred that the complex terrain surrounding NC interferes with circulation patterns, giving rise to conditions that are conducive to extreme summer precipitation over the region. Li et al (2017) obtained that higher-(lower) frequency hourly heavy rainfall events, along with more (less) accumulated rainfall amounts, occur over Beijing's northeast mountains (west and northwest mountains), and identified the positive effect of mountain-plain circulation on the generation of the hourly heavy rainfall event in warm season. Wang et al (2014) indicated that the simulated moisture transport for a summer torrential rain case over NC was mainly influenced by the Taihang Mountain.…”

An Observational Analysis of Three Extreme Rainfall Episodes of 19–20 July 2016 along the Taihang Mountains in North China

“…A narrow corridor of such a water vapor transport channel in North America is known as an atmosphere river (e.g., Zhu and Newell 1998;Moore et al 2012). Sustained rainfall events require the presence of favorable quasigeostrophic forcing, frontal or orographic lifting, mesoscale cold outflow boundaries, and thermal inhomogeneity including the urban heat island effect to facilitate continuous convective initiation (Baik et al 2001;Xu et al 2012;Houze 2012;Bao and Zhang 2013;Zhong and Yang 2015;Li et al 2017a).…”

Comparison of Environmental and Mesoscale Characteristics of Two Types of Mountain‐to‐Plain Precipitation Systems in the Beijing Region, China

“…The complex underlying terrain, comprising mountains, heterogeneous urban surfaces, and ocean, contributes to complex convective initiation (CI) processes and a variety of convection types. These convection types have drawn the attention of many researchers, who have conducted case studies and climatological analyses of these systems (Chen et al, 2012(Chen et al, , 2014Dou et al, 2015;Li et al, 2017;Meng et al, 2013;Xiao et al, 2015;Yang et al, 2014).…”