Laboratory Measurements of Sedimentation Velocity of Columnar Ice Crystals

The terminal velocity of cloud particles may be particularly important to climate studies, because they may have a non‐negligible effect on the radiation budget of the planet, and on the lifetime of clouds. In the present study, the terminal velocity of individual columnar ice crystals was measured under controlled laboratory conditions. The size and fall orientation were determined for ice crystals with maximum dimensions less than 160 µm. The results, which are in agreement with the fall velocity presented in previous studies, show a random orientation of the columnar ice crystals during free fall with a fall velocity which is best represented by their capacitance. A linear relationship between fall velocity and ice crystal capacitance is presented that could be used in cloud modelling. Although the mass of ice crystals was not measured, an estimation of this parameter was made and an empirical Best–Reynolds power‐law relationship was found.