A Statistical Analysis of Hail Events and Their Environmental Conditions in China during 2008–15

Abstract

AbstractAn 8-yr (i.e., 2008–15) climatology of the spatiotemporal characteristics of hail events in China and their associated environmental conditions are examined using hail observations, L-band rawinsondes, and global reanalysis data. A total of 1003 hail events with maximum hail diameter (MHD) of greater than 5 mm are selected and then sorted into three hail-size bins. Hail events with the largest MHD bin correspond to the median vertical wind shear in the lowest 6-km layer (SHR6) of 21.6 m s−1, precipitable water (PW) of 34.8 mm, and convective available potential energy (CAPE) of 2192 J kg−1. Hail with different MHD bins share similar freezing-level heights (FLHs) of about 4000 m. The thickness of the hail growth zone is thinner for hail events with the largest MHD bin. Hail events with different MHD bins display seasonal variations associated with the summer monsoon; that is, the hail season starts in South China in spring and then shifts to North China in summer. Larger hail is mainly observed during the spring in South China before monsoon onset in the presence of an upper-level jet and a low-level southwesterly flow accounting for large SHR6 and PW. In contrast, smaller-MHD hailstorms occur mainly during the summer in North China when surface heating is high and the low-level southerly flow shifts northward with pronounced baroclinicity providing large CAPE and PW, moderate SHR6, and low FLH. Environmental CAPE and SHR6 for large hailstones in China are comparable in magnitude to those in the United States but larger than those in some European countries.