The role of the gamma function shape parameter in determining differences between condensation rates in bin and bulk microphysics schemes
The condensation and evaporation rates predicted by bin and bulk microphysics schemes in the same model framework are compared in a statistical way using simulations of non-precipitating shallow cumulus clouds. Despite other fundamental disparities between the bin and bulk condensation parameterizat...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/4599/2017/acp-17-4599-2017.pdf |
| Summary: | The condensation and evaporation rates predicted by bin
and bulk microphysics schemes in the same model framework are compared in a
statistical way using simulations of non-precipitating shallow cumulus
clouds. Despite other fundamental disparities between the bin and bulk
condensation parameterizations, the differences in condensation rates are
predominantly explained by accounting for the width of the cloud droplet
size distributions simulated by the bin scheme. While the bin scheme does
not always predict a cloud droplet size distribution that is well
represented by a gamma distribution function (which is assumed by bulk
schemes), this fact appears to be of secondary importance for explaining why
the two schemes predict different condensation and evaporation rates. The
width of the cloud droplet size is not well constrained by observations, and
thus it is difficult to know how to appropriately specify it in bulk
microphysics schemes. However, this study shows that enhancing our
observations of this width and its behavior in clouds is important for
accurately predicting condensation and evaporation rates. |
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| ISSN: | 1680-7316 1680-7324 |