Relationship between drizzle rate, liquid water path and droplet concentration at the scale of a stratocumulus cloud system

[摘要] The recent ACE-2, EPIC and DYCOMS-II field experiments showed that thedrizzle precipitation rate of marine stratocumulus scales with the cloudgeometrical thickness or liquid water path, and the droplet concentration,when averaged over a domain typical of a GCM grid. This feature isreplicated here with large-eddy-simulations using state-of-the-art bulkparameterizations of precipitation formation in stratocumulus clouds. Theset of numerical simulations shows scaling relationships similar to the onesderived from the field experiments, especially the one derived from theDYCOMS-II data set. This result suggests that the empirical relationshipswere not fortuitous and that they reflect the mean effect of cloud physicalprocesses. Such relationships might be more suited to GCM parameterizationsof precipitation from shallow clouds than bulk parameterizations ofautoconversion, that were initially developed for cloud resolving models.

[学科分类] 大气科学