Multidimensional Lidar, Sunphotometer and Aircraft Observations of Urban Aerosols during the DISCOVER-AQ Mission

The Deriving Information on Surface Conditions from COlumn and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Mission is a five-year multisite experiment to better understand the relationship between satellite measured variables (columnar) with surface concentrations, required for air quality assessment and regulation. The first DISCOVER-AQ experiment was held in the Baltimore-Washington urban corridor during July 2011 and involved eleven lidars and two aircraft to provide the vertical profiles needed to close the vertical column with surface measures. In addition, over 40 sunphotometers were employed on a grid to add to the horizontal dimension during the DRAGON experiment, running concurrently. This paper is a preliminary look at a range of results from the experiment from very clear days, where the closure is relatively simple, to highly complex and varied aerosol regimes. Clearly important in the closure is the humidification of the aerosol that showed spatial variations in all three dimensions and may, in fact, dominate the relationship between aerosol optical depth and particle mass on a single day basis. Aerosol speciation analysis and in-situ microphysics from the aircraft is still being assessed and may explain scattering differences seen in depolarization of the aerosol and in aerosol layers confined to the PBL and aloft.