The raindrop size distribution and its moments are fundamental in many areas, such as radar measurement of rainfall using polarimetry and numerical modeling of the microphysical processes of rain formation and evolution. We develop a technique which uses advanced radar measurements and complete drop size distributions using two collocated instruments to retrieve the lower-order moments such as total drop concentration and rain water content. We demonstrate a proof-of-concept using a case study.

Raindrop shapes and fall velocities are presented for two high-wind/turbulent events. Results show strong gusts, directional wind shifts and/or inferred high turbulence intensity are correlated with reduced fall speeds, reaching values ~ 25–30 % less than the expected values, i.e. sub-terminal fall speeds. Significant percentage of asymmetric drops deviating from the most probable ax-isymmetric shapes was also detected during high turbulent intensities.

Raindrop fall velocities are important for rain rate estimation, soil erosion studies and in numerical modelling of rain formation in clouds. The assumption that the fall velocity is uniquely related to drop size is made inherently based on laboratory measurements under still air conditions from nearly 68 years ago. There have been very few measurements of drop fall speeds in natural rain under both still and turbulent wind conditions. We report on fall speed measurements in natural rain shafts.