Raindrop Size Distribution Measurements at 4,500 m on the Tibetan Plateau During TIPEX-III

As part of the third Tibetan Plateau Atmospheric Scientific Experiment field campaign, raindrop size distribution (DSD) measurements were taken with a laser optical disdrometer in Naqu, China, at 4,508 m above sea level (asl) during the summer months of 2013, 2014, and 2015. The characteristics of DSDs for five different rain rates, for two rain types (convective and stratiform), and for daytime and nighttime rains were studied. The shapes of the averaged DSDs were similar for different rain rates, and the width increased with rainfall intensity. Little difference was found in stratiform DSDs between day and night, whereas convective DSDs exhibited a significant day-night difference. Daytime convective DSDs had larger mass-weighted mean diameters (D-m) and smaller generalized intercepts (N-W) than the nighttime DSDs. The constrained relations between the intercept N-0 and shape mu, slope Lambda and mu, and N-W and D-m of gamma DSDs were derived. We also derived empirical relations between D-m and the radar reflectivity factor in the Ku and Ka bands.