Statistical Characteristics of Raindrop Size Distributions and Parameters in Central China During the Meiyu Seasons

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.