标题：Representing Precipitation Ice Species With Both Spherical and Nonspherical Particles for Radiative Transfer Modeling of Microphysics‐Consistent Cloud Microwave Scattering Properties
期刊名称：Journal of Advances in Modeling Earth Systems
电子版ISSN：1942-2466
出版年度：2018
卷号：10
期号：4
页码：1011-1028
DOI：10.1002/2017MS001226
出版社：John Wiley & Sons, Ltd.
摘要：Cloud microwave scattering properties for the Community Radiative Transfer Model (CRTM) have previously been created to be consistent with the particle size distributions specified by the WSM6 single‐moment microphysics scheme. Here substitution of soft sphere scattering properties with nonspherical particle scattering properties is explored in studies of Hurricane Karl (2010). A nonsphere replaces a sphere of the same maximum dimension, and the number of particles of a given size is scaled by the ratio of the sphere to nonsphere mass to keep the total mass of a given particle size unchanged. The replacement of homogeneous soft sphere snow particles is necessary to resolve a highly evident issue in CRTM simulations: precipitation‐affected brightness temperatures are generally warmer at 183 GHz than at 91.7 GHz, whereas the reverse is seen in observations. Using sector snowflakes resolve this issue better than using columns/plates, bullet rosettes, or dendrites. With sector snowflakes, both of these high frequencies have low simulated brightness temperatures compared to observations, providing a clear and consistent suggestion that snow is being overproduced in the examined simulation using WSM6 microphysics. Graupel causes cold biases at lower frequencies which can be reduced by either reducing graupel water contents or replacing the microphysics‐consistent spherical graupel particles with sector snowflakes. However, soft spheres are likely the better physical representation of graupel particles. The hypotheses that snow and graupel are overproduced in simulations using WSM6 microphysics shall be examined more systematically in future studies through additional cases and ensemble data assimilation of all‐sky microwave radiance observations.
关键词：radiative transfer modeling;CRTM;nonspherical particles;tropical cyclones;ice particle radiative transfer
