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Severe hailstorms frequently occurred in Beijing between May and August 2021, leading to extensive hail damage. These hailstorms were observed by radar and satellite data, and reported by surface observers. In this study, the spectral and cloud microphysical characteristics of typical Beijing events in 2021 were analyzed using Himawari-8 satellite products and ground-based S-band weather radar data obtained from the Beijing Meteorological Bureau. The relationship between Himawari-8 brightness temperature differences (BTD) and radar reflectivity was also investigated. The results revealed that the significant spectral depression of brightness temperatures (BTs) in hail clouds was observed by a satellite. Furthermore, the stronger the radar reflectivity was, the more rapidly BTD decreased, with a nonlinear relationship between them. The results of cloud physical characteristics show that, for cloud-top heights above 10 km, the cloud effective radius was about 25 μm, with a cloud-top temperature of 225 K during these hail events. By means of Gaussian fitting, the BT threshold value (11.2 μm) was determined by satellite at 230 K, with a BTD focused on 1.9 K when hailstorms occurred. These results will help us better understand the characteristics of hailstorms, while also providing information for future hail suppression in Beijing. [ABSTRACT FROM AUTHOR]

Stable oxygen isotope composition (δ18O p) and deuterium excess (d p) in precipitation carry important climate and hydrological information on the history of water from evaporation, transport to precipitation. This study aims to quantify the effect of potential factors on site-specific intra-event δ18O p and d p dynamics during three precipitation events in a mid-latitude region Beijing, China. The tested factors included moisture source (M s) and upstream rainout fraction (U p) obtained by HYSPLIT backward trajectory model, radar reflectivity factor (Z e) that corresponds to raindrop size by weather radar, sub-cloud evaporation fractionation (f e) by an isotope-evaporation model, local precipitation amount (L p) and precipitation intensity (I) by rain gauge, and relative location of the sampling sites (downwind or upwind). Intra-event δ18O p had an amplitude of 10.3‰, and 84% of the variance could be explained, in the descending order of importance, by M s , site, Z e , f e and I. Intra-event d p had an amplitude of 16.5‰, and 57% of the variance could be explained by f e , site, M s and I , in the descending order of importance. Absolute values of intra-event δ18O p and d p differed between two sites, 30 km apart, by up to 4.7‰ and 9.7‰, respectively. This site-specificity in δ18O p and d p was mainly caused by differences in rainout effects and I. This work provides new insights into separating the effects of various climatic and hydrological variables on high-frequency dynamics of δ18O p and d p. • Intra-event δ18O p and d p vary largely over time and between neighboring sites. • Moisture sources and sub-cloud evaporation mainly impact intra-event δ18O p and d p. • Rainout and precipitation intensity cause site-specific intra-event δ18O p and d p. [ABSTRACT FROM AUTHOR]

The values of ratio a of the linear relationship between specific attenuation and specific differential phase vary significantly in convective storms as a result of resonance scattering. The best-linear-fit ratio a at X band is determined using the modified attenuation correction algorithm based on differential phase and attenuation, as well as the premise that reflectivity is unattenuated in S band radar detection. Meanwhile, the systemic reflectivity bias between the X band radar and S band radar and water layer attenuation (ZW) on the wet antenna cover of the X band radar are also considered. The good performance of the modified correction algorithm is demonstrated in a moderate rainfall event. The data were collected by four X band dual-polarization (X-POL) radar sites, namely, BJXCP, BJXFS, BJXSY, and BJXTZ, and a China's New Generation Weather Radar (CINRAD/SA radar) site, BJSDX, in Beijing on 20 July 2016. Ratio a is calculated for each volume scan of the X band radar, with a mean value of 0.26 dB deg−1 varying from 0.20 to 0.31 dB deg−1. The average values of systemic reflectivity bias between the X band radar (at BJXCP, BJXFS, BJXSY, and BJXTZ) and S band radar (at BJSDX) are 0, −3, 2, and 0 dB, respectively. The experimentally determined ZW is in substantial agreement with the theoretically calculated ones, and their values are an order of magnitude smaller than rain attenuation. The comparison of the modified attenuation correction algorithm and the empirical-fixed-ratio correction algorithm is further evaluated at the X-POL radar. It is shown that the modified attenuation correction algorithm in the present paper provides higher correction accuracy for rain attenuation than the empirical-fixed-ratio correction algorithm. [ABSTRACT FROM AUTHOR]