Raindrop shapes and fall velocities in "turbulent times"

Abstract

Raindrop shapes and fall velocities measured by 2-dimensional video disdrometer are presented for 2 high-wind/turbulent events. The shapes were reconstructed using a relatively new technique. 10m height wind sensor data are used to derive proxy-indicators for turbulent intensities. Our results show strong gusts, directional wind shifts (i.e. shear) 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 (20%-35%) of asymmetric drops (>2mm) deviating from the most probable axisymmetric shapes were also detected for some events with high turbulent intensities.