Aerosol properties and their influences on marine boundary layer cloud condensation nuclei at the ARM mobile facility over the Azores

A multiplatform data set from the Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (MBL) Graciosa, Azores, 2009-2010 field campaign was used to investigate how continental aerosols can influence MBL cloud condensation nuclei (CCN) number concentration (N-CCN). The seasonal variations of aerosol properties have shown that the winter and early spring months had the highest mean surface wind speed (> 5ms(-1)) and greatest contribution of sea salt to aerosol optical depth (AOD), while continental fine mode aerosols were the main contributors to AOD during the warm season months (May-September). Five aerosol events consisting of mineral dust, pollution, biomass smoke, and volcanic ash particles were selected as case studies using Atmospheric Radiation Measurement (ARM) mobile facility measurements. The aerosols in Case I were found to primarily consist of coarse mode, Saharan mineral dust. For Case II, the aerosols were also coarse mode but consisted of volcanic ash. Case III had fine mode biomass smoke and pollution aerosol influences while Cases IV and V consisted of mixtures of North American pollution and Saharan dust that was advected by an extratropical cyclone to the Azores. Cases I, IV, and V exhibited weak correlations between aerosol loading and N-CCN due to mineral dust influences, while Cases II and III had a strong relationship with N-CCN likely due to the sulfate content in the volcanic ash and pollution particles. The permanent Eastern North Atlantic ARM facility over the Azores will aid in a future long-term study of aerosol effects on N-CCN.