AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Variations in Aerosol Size and Number During DISCOVER-AQ
EDWARD WINSTEAD, Lee Thornhill, Andreas Beyersdorf, Charles Hudgins, Luke Ziemba, Bruce Anderson, NASA Langley Research Center
Abstract Number: 613 Working Group: Urban Aerosols
Abstract The Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission is a multi-year campaign designed to improve the use of satellites to monitor surface-level air quality. DISCOVER-AQ is addressing its goals by conducting a series of coordinated ground-based and flight experiments over urban areas with well-established air quality issues to obtain vertically resolved measurements of trace gas and aerosol components. The first flight mission consisted of 14 science flights over the Washington D.C. - Baltimore metropolitan area during July, 2011. A large suite of aerosol instruments were flown onboard a NASA P-3B aircraft to measure the microphysical, optical and chemical properties of aerosols during spirals over the ground sites and during low level flights over Interstates 95 and 695 connecting Washington and Baltimore. This presentation examines the variability of aerosol size and number in both time and space over the Baltimore metropolitan region.
Within the atmospheric boundary layer between 0.3 and 1 km, particle number densities and size distributions varied considerable over short time periods and across horizontal distances as short as 1 km. High CN values typically occurred at times when aerosol scattering and hence surface area was relatively low. Values also tended to increase during the day as gas phase precursors were photochemically oxidized to form less volatile species, which in turn condensed to form new particles. Accumulation mode number concentrations often increased during the day, as the nucleation mode particles coagulated and aerosol surface increased to the point where deposition of low volatility precursors on existing particles was favored over new particle formation. Particle number concentrations and size also varied considerably from site to site across the 100-by 30-mile study area. This presentation examines the causes of the variability in more detail.