Raindrop Size Distribution Measurements at High Altitudes in the Northeastern Tibetan Plateau During Summer

Characteristics of raindrop size distribution during summer are studied by using the data from six Parsivel disdrometers located in the northeastern Tibetan Plateau. The analysis focuses on convective and stratiform precipitation at high altitudes from 2434 m to 4202 m. The results show that the contribution of the stratiform and convective precipitation with the precipitation intensity (R) of 1–5 mm h−1 to total precipitation increases with the altitude, and the microphysical characteristics of raindrops in convective precipitation are more obvious than that in stratiform precipitation. The droplet size spectra of both stratiform and convective precipitation show a single peak with a peak particle size >0.5 mm, and they have essentially the same peak particle size and number concentration at the same altitude. The maximum spectral widths of stratiform clouds are between 4 mm and 5 mm, while those of convective clouds range from 4 mm to 8 mm. Both the Marshall-Palmer and Gamma raindrop size distributions are more appropriate for both precipitation types, where the Gamma distribution is more suitable than the Marshall-Palmer distribution in terms of the actual raindrop spectrum distribution. The stratiform precipitation particles are relatively smaller with higher number concentration, while the opposite is true for the convective precipitation particles. The convective precipitation particles drop faster than stratiform precipitation particles when the particle size exceeds 2 mm, and the falling velocity of raindrops after standard curve fitting is underestimated during the observation period. Moreover, conventional radar estimation methods would underestimate the precipitation in the northeastern Tibetan Plateau with the radar reflectivity (Z) rain intensity (R) relationship of stratiform precipitation is Z=401R1.91, and that of convective precipitation is Z=454R1.89.