Model simulations of aerosol, cloud, and precipitation effects in comparison with ARM data

Description

The objectives of our proposal are to evaluate the capabilities of the Community Atmosphere Model version 5 (CAM5) model to capture cloud-aerosol-precipitation interactions, to identify weaknesses, and to ascertain possible improvements. This study will be carried out through a combination of cloud system-resolving model (CSRM) studies, studies with CAM5 and the CAM5 single-column model (SCM), and comparison of both with ARM measurements. We will carry out simulations and compare the CSRM with the CAM5 SCM model to test the response of CAM5 SCM low-level clouds to increases in aerosols. We would also systematically degrade our CSRM simulation to the physics represented in CAM5 in order to understand the causes of differences.

The first step in our proposal is to examine the data from the ARM Southern Great Plains (SGP) site to pick time periods that can be informative for determining the proper representation of aerosol/cloud interactions in global models. We focus on data from the SGP site, since this site has a wide variety of cloud types as well as the most up-to-date and complete data systems. Our intension is to separate low liquid water path (LWP) clouds from high LWP clouds, in order to focus on specific aerosol-precipitation response regimes (Li et al. 2011). We pick time periods within this regime with low and high aerosol concentrations to test the CSRM. We examine whether these periods have similar large-scale forcing data. In this poster we report our progress in examining the ARM data for representative time periods that can be used in our study.