Effects of chemical composition on aerosol optical properties: Hygroscopicity and absorption enhancements in an urban environment during NASA DISCOVER-AQ
Abstract
Observations of aerosol optical, chemical, and microphysical properties were made aboard the NASA P-3B aircraft in July 2011 in support of the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) mission. Aerosol optical properties (scattering and absorption) are the basis for complex remote sensing retrievals and their relationships with chemical composition can bridge the gap between satellite observations and air quality source apportionment. Aerosol hygroscopicity, the propensity of a particle to take up water, is an important parameter for understanding how particles scatter visible light. Both hygroscopicity and absorption enhancements are inherently related to the chemical composition of particles; changes to that composition (photochemical aging) can result in increased hygroscopicity and absorption. This results in a complex vertical and spatial distribution of aerosol properties in urban environments. We present aerosol hygroscopicity and absorption observations as a function of chemical composition from airborne observations in the Washington D.C./Baltimore region. Hygroscopicity is derived from dry (relative humidity (RH) < 40 %) and humidified (RH > 75 %) scattering coefficients measured by two nephelometers, and absorption by a particle soot absorption photometer (PSAP). Composition measurements were made using a particle-into-liquid sampler (PILS, inorganic ion and water-soluble organic carbon content) and single particle soot photometer (SP2, black carbon mass concentration). Vertical profiles (from 0.3 to 4.5 km) and aerosol optical depth (AOD) are presented as a function of time-of-day, day-of-week, and geographic location in the Washington D.C./Baltimore region. Specific focus will be on relating boundary layer with column-averaged properties for different conditions encountered.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.A21B0063Z
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0345 ATMOSPHERIC COMPOSITION AND STRUCTURE / Pollution: urban and regional