An Investigation of Aerosol-Cloud-Precipitation Interactions in the South-East Pacific Using DOE G-1

Abstract

The effect of aerosol particles on albedo and rain formation in marine stratocumulus clouds plays a key role for Earth’s radiative forcing and is a sustained focus of the DOE Atmospheric System Research program. Most recently, the VOCALS-REx field campaign (Wood et al., 2011), with participation by the DOE G-1 aircraft produced an extensive data set of aerosol and cloud measurements in the stratocumulus-capped marine boundary layer (MBL) of the South-East Pacific.
We propose to analyze aerosol and cloud data from the DOE G-1 mission during VOCALS-REx, to conduct WRF/Chem large eddy simulations (LES), to investigate aerosol-cloud-precipitation interactions in the South-East Pacific marine boundary layer, to bridge the scale gap between small- scale and large-scale models, and to describe sub-grid scale processes of climate models. Large eddy simulations will be conducted on comparably large domains (~ 100 km x 100 km). We will investigate (1) the role of longitudinal gradients in wind speed, sea surface temperature, ocean fluxes, and lower tropospheric temperature and humidity across the South-East Pacific in regulating the effect of aerosol (natural or anthropogenic) on cloud properties, precipitation, and open cell formation, (2) the effect of the observed secular trend towards increasing ocean surface wind speeds on emissions of sea salt aerosol, surface fluxes, cloud properties and precipitation, and on the transition from closed to open cells, and (3) effects of induced variations in the aerosol in the system. The results of this work will provide understanding of the interaction of aerosol, marine boundary layer clouds, and precipitation in a changing climate.