第七届青年地学论坛

The observation of raindrop size distribution (abbreviated as DSD) is an important part of rainfall observation. DSD plays an important role in quantative precipitation estimation based on radar reflectivity and rainrate (Z-R) relation. However, it means a lot to obtain the profile of the DSD due to the angle of weather radar dectection. Based on three laser optical Parsivel disdrometers installed at different heights on meteorological tower, which is widely used to detect DSD data, combine with wind speed detected by ultrasonic anemometer and inclination of the tower detected by inclinometer, the vertical distribution characteristics of raindrop size distribution(DSD) and the influences on rainfall measurement by radar in the lower atmospheric boundary layer were investigated, during 31 precipitation episodes in Beijing from June to August 2020.
The results show that, the break-up process is dominant on the falling path of raindrops from 280m to 140m, which lead to the decrease of large scale raindrops and the increase of small scale raindrops. Whereas, from 140m to ground, the collision-coalescence process is dominant on the falling path of raindrops, which lead to the decrease of large and small scale raindrops, and the increase of medium scale raindrops. Because of the great influence by break up, large scale raindrops decrease rapidly with height. The DSD of convective rain in Beijing is different from oceanic-like cluster and continental-like cluster, with the generalized intercept parameter log₁₀N_w≈3.6-3.8 and the mass-weighted mean diameter D_m≈1.7-1.9. Due to the change of DSD with height, characteristic parameters of rainfall vary nonlinerly. A ‘Z-R mismatch error’ would be caused when using ground precipitation data for correction of the meteorological radar rainfall estimation, which lead to an error in radar detection of rainfall.

raindrop size distribution,Vertical Distribution