The Raindrop Size Distributions for Heavy Rainfall during the Mei-Yu Season in the Middle of China

Meiyu is a unique and seasonal rainy season during the East Asian summer monsoon. The meiyu season mainly lasts from mid-June to mid-July over the middle area of China bringing heavy rainfall and floods. Raindrop Size Distributions (DSD) is a fundamental microphysical property of precipitation, and for the Middle of China we still knew little about them. The six Parsivel sites data during the 2016–2018 in meiyu seasons are analyzed to improve our understanding of the DSD characteristics.The frequency occurrence for RR < 5 mm h⁻¹ is 83.9%, which contributes only 30.5% to the total accumulated rainfall; for RR > 10 mm h⁻¹, its 7.4% and 52.1% for frequency occurrence and the total accumulated rainfall. The rain rate (RR) and total accumulated rainfall over the middle reaches are greater than those over the lower reaches in central China, especially for heavy rainfall. The quality-controlled 1-min raindrop data are classified into CR and SR. This study shows higher number concentrations of raindrops than the lower reaches of the Yangtze River Valley in China. The SR raindrops increase with RR over both the middle and lower reaches of the Yangtze River Valley, whereas the N_w values over the middle reaches are much higher than those over the lower reaches. Opposite to the SR results, the CR N_w values over both the middle and lower reaches are similar to one another, but the CR raindrops over the middle reaches are larger than those over the lower reaches. A rainstorm is studied by radar and the Parsivel disdrometers during meiyu, it is shown that the precipitation of meiyu is dominated by CR. The Dm and Nw for SR are smaller than CR. The zero-layer bright band are obviously on the radar reflectivity, and the convective cell only lasts for a few hours.