The rain parameters derived from the laser OTT second‐generation Particle Size Velocity (Parsivel²), the two‐dimensional video disdrometer (2DVD), and DZZ5 tipping‐bucket rain gauge (RG) during the Integrative Monsoon Frontal Rainfall Experiment (IMFRE) in summer 2018 are compared. The total rainfall amounts observed by Parsivel, 2DVD, and RG during IMFRE were 178.07, 176.76, and 182.5 mm, while their total rainy hours were 113, 113, and 90. The mean D_m (mass‐weighted mean diameter) and LWC (liquid water content) values derived from Parsivel and 2DVD were 1.03 and 1.01 mm and 0.247 and 0.223 g m⁻³. The rainy samples from six Parsivel sites over the middle reaches of the Yangtze River during the 2016–2018 Meiyu seasons have been collected and analyzed. The occurrence frequencies for rain rates (RR) < 5 and >10 mm hr⁻¹ were 83.9% and 7.4%, respectively, but they contributed 30.5% and 52.1% of the total accumulated rainfall. Compared with the results over the lower reaches of the Yangtze River, the total accumulated rainfall percentages for RR < 5 mm hr⁻¹ and RR > 10 mm hr⁻¹ observed at XN site were higher and lower, respectively. The stratiform rain (SR) raindrop size increases with RR over both the middle and lower reaches, whereas the N_w values over the middle reaches are much higher. Opposite to the SR results, the convective rain (CR) raindrops from this study are larger, while their N_w values are similar to one another. For gamma‐type‐size distribution, the μ − λ and Z − R relations are strongly dependent on geographical location.

During July 19–21, 2021, Henan Province in China experienced a historically rare heavy rainfall event, with the maximum hourly rainfall amount appearing in Zhengzhou City, the capital of Henan Province, on 20 July (hereafter “7.20” HRE). In this study, the “7.20” HRE is analyzed based on the observations of 215 ground‐based GNSS stations and 118 national meteorological stations in Henan Province, and ERA5 reanalysis data. By comparing the surface precipitation intensity, water vapor, and atmospheric energy conditions across temporal and spatial scales, it is shown that the area with heavy rainfall near Zhengzhou did not exhibit extreme atmospheric energy values or vertical environmental instability. The environmental conditions in the southeast of Zhengzhou were more conducive to the occurrence and development of precipitation, but there was no obvious precipitation on the ground. The analysis of water vapor consumption rate ( V _c ) and precipitation flux ( F ) reveals that a large amount of water vapor was consumed in the southeast of Zhengzhou, resulting in the formation of substantial precipitation above the 600 hPa level. The precipitation was carried to Zhengzhou by the southeast wind, leading to the precipitation content over Zhengzhou and its nearby areas increasing rapidly as altitude decreased from 600 hPa to 1000 hPa. The overlay of precipitation provided by both dynamic transport from the southeast and cloud microphysical production over Zhengzhou was the main cause of the “7.20” HRE under the background of an atypical weak environmental field.

Heavy precipitation in Northeast China is frequently modulated by the Northeast China Cold Vortex (NCCV), although the microphysical processes within squall lines under such conditions remain insufficiently understood. This study presents a comprehensive analysis of an NCCV-influenced squall line in Liaoning Province, utilizing coordinated S-band polarimetric radar and surface disdrometer observations. The raindrop size distribution (DSD) characteristics and three-dimensional microphysical structure are systematically examined for both convective and stratiform regimes. A comparative analysis of DSD and warm-rain microphysical mechanisms is also conducted with a Mei-yu event. Results show that convective rain in the NCCV squall line exhibits a continental-type DSD, characterized by fewer but larger raindrops compared to other heavy rainfalls in China. In contrast, the Mei-yu frontal convection under NCCV influence exhibits a transitional DSD pattern between the maritime and continental types, with raindrops smaller and denser than those in the NCCV squall line. Vertical structure of the mature squall line shows prominent differential reflectivity (Z_DR) and specific differential phase (K_DP) columns above the melting level within the convective region, indicating vigorous riming growth of graupel and hail driven by strong updrafts. Meanwhile, the stratiform region is characterized by ice crystals and aggregates, formed primarily through deposition and aggregation processes. The subsequent melting of ice-phase particles followed by collision–coalescence and evaporation-driven size sorting shapes the large but sparse raindrops in the NCCV squall line. Comparison with Mei-yu convection demonstrates that surface DSD is shaped by environmental conditions and vertical microphysics. The drier, more unstable environment in the NCCV squall line favors deep convection with active ice-phase processes, while the relatively moist and stable environment of the Mei-yu convection supports shallower convection dominated by warm-rain processes. Future multi-case studies with integrated observations are needed to quantify how environmental and aerosol conditions modulate these heavy precipitation processes.

Due to system interactions, the formation and maintenance of dual squall lines are more complex than for single squall lines. In this study, we use upper-air soundings, ERA5 reanalysis data, high-density surface automatic weather station observations, and Doppler radar data to analyze a dual squall-line system that occurred over North China on 13 June 2022 under the Northeast China Cold Vortex. We focus on the differences between the two squall lines in mesoscale environments, convective triggering mechanisms, and maintenance processes. The main results are as follows: (1) The dual squall-line event occurred in different sectors of the Northeast China Cold Vortex, with both lines exhibiting a “dry-cold aloft, warm-moist below” stratification. However, significant spatiotemporal differences in mesoscale thermodynamic and dynamic conditions across Hebei and Shandong provinces led to distinct evolutionary pathways between the two squall lines. (2) Squall Line 1 (SL1) was triggered by the superposition of cold-pool outflow from convective cells over the Bohai Bay and convergence lines associated with surface cyclonic circulations. Squall Line 2 (SL2) was triggered by the thermal instability in the overlapping region of the temperature and dew-point fronts on the eastern slope of the Taihang Mountains, in conjunction with topographic uplift driven by the easterly flow. (3) This case study shows that squall-line maintenance depends not only on environmental CAPE and vertical wind shear but may also be closely related to the coordinated interplay between local thermal conditions and low-level shear. SL1, situated in a high-CAPE, low-LCL warm-moist environment, experienced relatively weak low-level shear; however, the ratio of cold-pool propagation speed to low-level shear remained near the RKW optimum, favoring persistence. Additionally, cold-pool spreading on the southern flank triggered new convection that merged into the southern end of the squall line, enhancing the cold pool via evaporative cooling and further promoting longevity. By contrast, SL2 displayed a pronounced north–south disparity: the northern segment failed to satisfy RKW balance due to insufficient cold-pool propagation relative to shear, leading to rapid echo dissipation; the southern segment, featuring an overly strong cold pool and low-CAPE, high-LCL conditions, inhibited deep convection. As a result, SL2 gradually split due to the spatial mismatch of thermodynamic and dynamic conditions along its north–south extent.