Development of a cloud microphysical model and parameterizations to describe the effect of CCN on warm cloud

[摘要] First, a hybrid cloud microphysical model was developed that incorporatesboth Lagrangian and Eulerian frameworks to study quantitatively the effectof cloud condensation nuclei (CCN) on the precipitation of warm clouds. Aparcel model and a grid model comprise the cloud model. The condensationgrowth of CCN in each parcel is estimated in a Lagrangian framework. Changesin cloud droplet size distribution arising from condensation and coalescenceare calculated on grid points using a two-moment bin method in asemi-Lagrangian framework. Sedimentation and advection are estimated in theEulerian framework between grid points. Results from the cloud model showthat an increase in the number of CCN affects both the amount and the areaof precipitation. Additionally, results from the hybrid microphysical modeland Kessler's parameterization were compared.Second, new parameterizations were developed that estimate the number andsize distribution of cloud droplets given the updraft velocity and thenumber of CCN. The parameterizations were derived from the results ofnumerous numerical experiments that used the cloud microphysical parcelmodel. The input information of CCN for these parameterizations is onlyseveral values of CCN spectrum (they are given by CCN counter for example).It is more convenient than conventional parameterizations those need valuesconcerned with CCN spectrum, C and k in the equation of N=CS^k, or, breadth,total number and median radius, for example. The new parameterizations'predictions of initial cloud droplet size distribution for the bin methodwere verified by using the aforesaid hybrid microphysical model. The newlydeveloped parameterizations will save computing time, and can effectivelyapproximate components of cloud microphysics in a non-hydrostatic cloudmodel. The parameterizations are useful not only in the bin method in theregional cloud-resolving model but also both for a two-moment bulkmicrophysical model and for a global model. The effects of sea salt,sulfate, and organic carbon particles were also studied with theseparameterizations and global model.

[学科分类] 大气科学