Aerosols, clouds, and precipitation in the marine boundary layer at the Azores AMF

Poster PDF

Description

The Clouds, Aerosols, and Precipitation in the Marine Boundary Layer Project (CAP-MBL) aims to better understand cloud-aerosol-precipitation interactions. This project utilizes continuous measurements from the ARM Mobile Facility (AMF) deployment at Graciosa Island in the Azores during May 2009–December 2010. Here we present a few preliminary results from CAP-MBL. The Azores region of the North Atlantic hosts a variety of cloud types in the MBL including stratocumulus, trade cumulus, and transitional clouds. Back trajectories from the MBL at Graciosa imply diverse geographic sources of aerosol, including anthropogenically modified air from Europe and northern North America and relatively pristine air from the Arctic. We find that ground-based sunphotometer measurements of AOD at Graciosa agree reasonably well with daily MODIS AOD measurements over a four-month period starting in July 2009. Measured surface CCN concentrations correlate only weakly with the AOD. We compare output near Graciosa of a collection of NCAR CAM 5.0 and GFDL AM3p9 global forecast-mode simulations for the same period. These new GCM versions include aerosols interactive with cloud microphysics. The models produce reasonable simulations of daily variations of cloud and boundary layer depth, but have difficulty reproducing variations of AOD at Graciosa.