Statistical Characteristics and Environmental Conditions of the Warm-Season Severe Convective Events over North China

Ruoyun Ma,Shuanglei Feng,Hong Han,Shuanglong Jin,Jianhua Sun,Shijun Sun,Shenming Fu

doi:10.3390/atmos12010052

Abstract

Based on severe weather reports, surface precipitation observations, surface routine observations, and the European Center for Medium-Range Weather Forecasts ERA5 reanalysis dataset during the warm seasons (May–September) of 2011–2018 over North China, this paper analyzes the statistical characteristics and environmental conditions of three types of severe convective events. Results are compared between events with different altitudes (i.e., mountains and plains), severities (i.e., ordinary and significant), and months. Hail and thunderstorm high winds (THWs) are more common over the mountains whereas short-duration heavy rainfall (SDHR) is more frequent over the plains. The occurrence frequency of severe convective events exhibits distinct monthly and diurnal variations. Analyses of the environmental parameters provide reference for the potential forecasting of severe convective events over this region. Specifically, the 850–500 hPa temperature lapse rate (LR85), pseudo-equivalent potential temperature at 500 hPa (thetase500), and precipitable water (PW) are skillful in distinguishing hail and THW environments from SDHR environments, and thetase500 is useful in discriminating between hail and THW environments. The convective environments over the plains are characterized by significantly higher (lower) PW (LR85) compared with mountains. The skill of these parameters in forecasting the severity of the convective hazards is limited. Probability distributions in the two parameters space indicate that the occurrence of significant hail requires both higher most unstable convective available potential energy (MUCAPE) and stronger 0–6 km bulk wind shear (SHR6) compared with ordinary hail. Compared with ordinary THWs, the significant THWs over the mountains depend more on the SHR6 whereas those over the plains rely more on the MUCAPE. The significant SDHR events over the plains tend to occur under a variety of instability conditions. The thermodynamic parameters (i.e., MUCAPE, thetase500, and downdraft convective available potential energy), and PW are significantly higher in July–August, whereas the LR85 and vertical wind shear are apparently higher in May, June and September.

Highlights

According to the National Meteorological Center (NMC), China Meteorological Administration (CMA), severe convective weather refers to ≥ 5 mm hail, thunderstorm highAtmosphere 2020, 11, x FOR PEER REVIEW wwininddss(T(THHWWss))wwitihthwwininddspspeeededss≥≥1177.2.2mms−s−11 oorr BBeeaauuffoorrtt ssccaallee88,sshhoorrt-t-dduurraattioionnhheeaavvyy rraaiinnffaallll(S(SDDHHRR))wwitihthhhoouurlrylypprerceicpipitiattaitoionn≥≥2200mmmmhh−−11, aanndd aannyy ttoorrnnaaddoo [[11]]
Since there is a distinct increase in the number of precipitation stations in the study domain during the study period, the precipitation stations in 2011 are Atmosphere 2020, 11, x FOR PEER REuVsIeEdWin analyzing the statistical characteristics of the short-duration heavy rainfall (SDHR) events (Figure 2a)
The distribution reveals the pronounced impact of topography: hail and thunderstorm high winds (THWs) frequently occur over the mountains, whereas Atmosphere 2020, 11, x FOR PEER REVSIEDWHR primarily occurs over the plains (Figure 3a,b)

Summary

Introduction

According to the National Meteorological Center (NMC), China Meteorological Administration (CMA), severe convective weather refers to ≥ 5 mm hail, thunderstorm high. Atmosphere 2021, 12, 52 counting for large SHR6 and PW, whereas smaller hail occurred mainly during the summer over North China when pronounced baroclinicity providing large convective available potential energy (CAPE) and PW, moderate deep-layer shear, and low freezing level height. We pay attention to comparing the environments between three types of severe convective events (i.e., hail, THWs, and SDHR), as well as between events with different severities (i.e., ordinary and significant) occurring over different altitudes (i.e., mountains and plains) and months using environmental parameters. The environments under which various severe convective events are most likely to occur are analyzed in two-parameter spaces. These results will provide reference for the potential forecasting of severe convective events over North China

Data and Methodology

The SWRs Dataset

Parameter Computation

Spatial and Temporal Distributions of the Severe Convective Events