Multi-scale observations of small cloud systems

 

Authors

Allison C. McComiskey — Brookhaven National Laboratory
Graham Feingold — NOAA- Earth System Research Laboratory
Andrew M. Vogelmann — Brookhaven National Laboratory

Category

Aerosol-Cloud-Radiation Interactions

Description

Shallow cumulus dominates cloud feedbacks in general circulation models (GCMs) and also exhibits the greatest amount of inter-model spread. A major challenge for this cloud regime is that the horizontal dimension of a GCM grid cell is large relative to the high frequency variability that governs radiative forcing. Evaluation of these models is often based on means, or sometimes simple distributions of properties retrieved from space; however, simple averaging of sub-grid scale variability may create biases in the representation of individual properties or parameterizations that are not based in physics. Sub-grid distributions of cloud liquid water, cloud fraction, and microphysical properties are essential for representing accurate grid-scale radiative fluxes but raise some questions: To what extent do distributions of cloud characteristics vary under different conditions of aerosol concentrations or environmental variables? What are the factors controlling the various distributions? Do distributions vary as a function of observational approach or scale? To answer these questions, we combine surface, in situ (RACORO), and satellite observations at ARM’s Southern Great Plains site. We analyze radiatively pertinent characteristics of small clouds and their determining factors, including the larger-scale environmental state, cloud-scale dynamics, and aerosol. The internal consistency of these systems is examined using multivariate distributions of many of these properties.