Inland frontal heavy rainfall (FR) and coastal warm‐sector heavy rainfall (WR) are two typical types of precipitation in South China during the pre‐summer rainy season. FR and WR are found to be generated by different mechanisms, but their differences in microphysical features and relevant possible reasons are not well understood. In the present study, dual‐polarization observations merged from 10 radars are utilized to investigate microphysical characteristics of two coexisting convective systems producing FR and WR. Overall, the WR has a stronger convection intensity, larger raindrop size, and higher liquid water content than the FR. The larger raindrops might be partly attributed to the deeper warm‐sector convection evidenced by stronger convective updrafts, which could potentially promote mixed‐phase processes. Raindrops in the WR are still larger even when the WR has a similar convection intensity with the FR, which might be explained by the active warm rain processes associated with higher low‐level humidity and more evident low‐level rotation in the WR. In addition, the FR was originally developed near the front and then vacated from the front into the warm sector, exhibiting an obvious temporal evolution in microphysical characteristics. Despite weaker convection intensity, the FR away from the front manifests a larger mean raindrop size than the FR near the front possibly because of more abundant environmental moisture in the warm sector.

Extreme precipitation is an issue of worldwide concern, but its microphysics remain elusive. The convective and microphysical characteristics of extreme precipitation features (EPFs) in a monsoon coastal area (South China) are investigated mainly using 2‐year observations from a dual‐polarization radar and distrometers. The EPFs are accompanied by a broad range of convective intensity, and categorized into the “intense”, “moderate”, and “weak” convection accounting for 17.3%, 48.6% and 34.1% of the total population, respectively. The EPFs with weaker convection show weakened size sorting and less breakup of large raindrops, but a larger ratio of liquid water path to ice water path and more prominent coalescence warm‐rain process. All the three categories are dominated by the coalescence in the liquid‐phase processes, and have much more populous raindrops than the “continental” with a mean size larger than the “maritime” regime. These results improve our understanding of extreme precipitation from the microphysical perspective.

China New Generation Doppler Weather Radar (CINRAD) plans to upgrade its hardware and software to achieve polarimetric function. However, the small-magnitude polarimetric measurements were negatively affected by the scattering characteristics of ground clutter and the filter’s response to the ground clutter. This polarimetric contamination was characterized by decreased differential reflectivity (Z_DR) and cross-correlation coefficient (ρ_hv), as well as an increased standard deviation of the differential phase (Φ_DP), generating a large-area and long-term observational anomaly for eight polarimetric radars in South China. Considering that outliers simultaneously appeared in the radar mainlobe and sidelobe, the variations in the reflectivity before and after clutter mitigation (ΔZ_H) and ρ_hv were used for quantitatively describing the random dispersion caused by mainlobe and sidelobe clutters. The performance of polarimetric algorithms was also reduced by clutter contamination. The deteriorated membership functions in the hydrometeor classification algorithm changed the proportion of classified echoes. The empirical relations of R(Z_H, Z_DR) and R(K_DP) were broken in the quantitative precipitation estimation algorithm and the extra error considerably exceeded the uncertainty caused by the drop-size distribution (DSD) variability of R(Z_H). The above results highlighted the negative impact of clutter contamination on polarimetric applications that need to be further investigated.

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 (Z_W) 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 Z_W 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.