New equations for the terminal velocity of precipitation droplets in a standard atmosphere

Abstract

New equations are presented which give the terminal velocity of water droplets in three physically distinct drag regimes explicitly as functions of equivalent drop radius and height in a standard atmosphere. It is shown that at h = 0 , the expressions give results which agree with Gunn and Kinzer's terminal velocity measurements with an overall divergence less than the measurement uncertainty of the data. Results are also compared with the semi-empirical formulations of Beard and shown to be in good agreement at all drop sizes 0.25 r₀ 3500 μm and heights -1.5 h 5 km in the atmosphere.