Refinements to Ice Particle Mass Dimensional and Terminal Velocity Relationships for Ice Clouds. Part II: Evaluation and Parameterizations of Ensemble Ice Particle Sedimentation Velocities

This two-part study addresses the development of reliable estimates of the mass and fallspeed of single ice particles and ensembles. Part I of the study reports temperature dependent coefficients for the mass-dimensional relationship, m = aDb, where D is particle maximum dimension. The fall-velocity relationship, Vt = ADB, is developed from observations in synoptic and low-latitude, convectively-generated, ice cloud layers, sampled over a wide range of temperatures using an assumed range for the exponent b. Values for a, A, and B were found that were consistent with the measured particle size distributions (PSD) and the ice water content (IWC).
To refine the estimates of coe±cients a and b to fit both lower and higher moments of the PSD and the associated values for A and B, Part II uses the PSD from Part I plus coincident, vertically -pointing Doppler radar returns. The observations and derived coe±cients are used to evaluate earlier, single moment, bulk ice microphysical parameterization schemes as well as to develop improved, statistically-based, microphysical relationships. They may be used in cloud and climate models and to retrieve cloud properties from ground-based Doppler radar and spaceborne,
conventional radar returns.