Surface-Based Remote Sensing of the Aerosol Indirect Effect at Southern Great Plains

We have demonstrated first measurements of the aerosol indirect effect using ground-based remote sensors at the Southern Great Plains (SGP) site. The response of non-precipitating, ice-free clouds to changes in aerosol loading is quantified in terms of a relative change in cloud-drop effective radius (re) for a relative change in aerosol extinction under conditions of equivalent cloud liquid water path (LWP). This is done in a single column of air at a temporal resolution of 20 s (spatial resolution of ~100 m). Cloud-drop re is derived from a cloud radar and microwave radiometer (MWR). Aerosol extinction is measured below cloud base by a Raman lidar. Results suggest that there is good correlation (0.67) between the cloud response and a measure of cloud turbulence. We have not found clear relationships between the cloud response and the back trajectories.