Parameterization of cloud droplet formation in global climate models
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چکیده
An aerosol activation parameterization has been developed, based on a generalized representation of aerosol size and composition within the framework of an ascending adiabatic parcel; this allows for parameterizing the activation of chemically complex aerosol with arbitrary size distribution and mixing state. The new parameterization introduces the concept of “population splitting”, in which the CCN that form droplets are treated as two separate populations: those which have a size close to their critical diameter, and those that do not. Explicit consideration of kinetic limitations on droplet growth is introduced. Our treatment of the activation process unravels much of its complexity. As a result of this, a substantial number of conditions of droplet formation can be treated completely free of empirical information or correlations; there are, however, some conditions of droplet activation for which an empirically derived correlation is utilized. Predictions of the parameterization are compared against extensive cloud parcel model simulations, for a variety of aerosol activation conditions that cover a wide range of chemical variability and CCN concentrations. The parameterization tracks the parcel model simulations closely and robustly. The parameterization presented here is intended to allow for a comprehensive assessment of the aerosol indirect effect in GCMs.
منابع مشابه
Continued Development of a Cloud Droplet Formation Parameterization for Global Climate Models
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تاریخ انتشار 2012