Accurate parameterization of precipitation particles' fall speeds for bulk cloud microphysics schemes
Journal
ATMOSPHERIC RESEARCH
Journal Volume
273
Date Issued
2022-08-01
Author(s)
Abstract
A set of formulas emphasizing accuracy was developed to describe raindrops' and ice particles' fall speed for use in multi-moment microphysical parameterizations applying gamma-type size distributions. The formulas considered fall speed's variation with particle properties (size, density, and shape) and air density based on a robust theoretical framework. Root-mean-square errors from these formulas are about 1.4% and 4%, respectively, for raindrops and ice particles. Most deviations are within ±3% for raindrops and 8% for ice particles under a wide range of particle properties and atmospheric conditions. The accuracy is significantly higher than existing formulas applied in meteorological models. One-dimensional dynamic model tests considering only the raindrop sedimentation process indicate that our formulas can properly simulate the vertical profiles of raindrops' three moments compared to the numerically integrated theoretical values. All three moments evolved consistently in time and space, with the gravitational sorting effect revealed by the faster sedimentation in the higher moments. Other less accurate formulas either misplaced the peak raindrop content's altitude or produced substantial vertical spread.
Subjects
Group fall speeds; Bulk parameterization; Gamma size distribution; Precipitation particles; Aspect ratio; Gravitational sorting; TERMINAL VELOCITY; WATER-DROPS; SIZE DISTRIBUTIONS; MODEL DESCRIPTION; HABIT PREDICTION; VAPOR-DEPOSITION; DOPPLER RADAR; POWER LAWS; PART II; ICE
SDGs
Publisher
ELSEVIER SCIENCE INC
Type
journal article