Journal
ADVANCES IN ATMOSPHERIC SCIENCES
Volume 40, Issue 1, Pages 155-167Publisher
SCIENCE PRESS
DOI: 10.1007/s00376-022-2065-7
Keywords
cloud microphysics parameterization; cloud droplet spectrum; double-moment scheme; shape parameter
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The shape parameter of the Gamma size distribution is crucial for the evolution of cloud droplet spectra. Inaccurate specification of this parameter in commonly used bulk double-moment schemes hinders the reasonable description of cloud droplet spectra during condensation. A newly-developed triple-parameter condensation scheme, which determines the shape parameter through the number concentration, cloud water content, and reflectivity factor of cloud droplets, has been proposed for improving the evolution of cloud droplet spectra.
The shape parameter of the Gamma size distribution plays a key role in the evolution of the cloud droplet spectrum in the bulk parameterization schemes. However, due to the inaccurate specification of the shape parameter in the commonly used bulk double-moment schemes, the cloud droplet spectra cannot reasonably be described during the condensation process. Therefore, a newly-developed triple-parameter condensation scheme with the shape parameter diagnosed through the number concentration, cloud water content, and reflectivity factor of cloud droplets can be applied to improve the evolution of the cloud droplet spectrum. The simulation with the new parameterization scheme was compared to those with a high-resolution Lagrangian bin scheme, the double-moment schemes in a parcel model, and the observation in a 1.5D Eulerian model that consists of two cylinders. The new scheme with the shape parameter varying with time and space can accurately simulate the evolution of the cloud droplet spectrum. Furthermore, the volume-mean radius and cloud water content simulated with the new scheme match the Lagrangian analytical solutions well, and the errors are steady, within approximately 0.2%.
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