Vertical Profiles of Aerosol Extinction over the Southeastern US during the Summer

Recent studies have shown that the summertime aerosol extinction in the southeastern United States measured in situ at the surface is lower than the extinction above the surface measured by satellite-based LIDAR. Regional modeling is able to reproduce the extinction at the surface, however not the higher extinction above ground. Enhanced secondary organic aerosol above the surface layer, possibly associated with aqueous processing, has been proposed as a possible explanation for the discrepancy. During June and July 2013, in situ measurements of aerosol extinction, hygroscopicity, and particle size distributions were collected from the NOAA WP-3 aircraft as part of the Southeast Atmosphere Study. Over 100 vertical profiles were collected at altitudes between 500 m and 5000 m above ground level. We present a preliminary analysis of aerosol extinction in these profiles and compare the extinction with ground-based measurements and previous studies. Measurements of aerosol composition and trace gases aboard the aircraft are used to assess the prevalence of secondary aerosol mass production above the surface.