HR: 0800h
AN: A41A-0013    [Abstracts]
TI: Multiwavelength In-situ Aerosol Extinction, Scattering and Absorption During the NEAQS-ITCT 2004 Field Campaign
AU: * Sierau, B
EM: bsierau@atmos.washington.edu
AF: University of Washington, Department of Atmospheric Sciences, Box 351640, Seattle, WA 98195 United States
AU: Covert, D S
EM: dcovert@u.washington.edu
AF: University of Washington, Department of Atmospheric Sciences, Box 351640, Seattle, WA 98195 United States
AU: Baynard, T
EM: tbaynard@al.noaa.gov
AF: NOAA Aeronomy Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Coffman, D
EM: derek.coffman@noaa.gov
AF: NOAA Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: Quinn, P K
EM: patricia.k.quinn@noaa.gov
AF: NOAA Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AU: Bates, T S
EM: tim.bates@noaa.gov
AF: NOAA Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AB: {\it In-situ}, three wavelength-measurements of aerosol extinction, scattering and absorption of the New York/Boston urban pollution outflow were carried out aboard the NOAA research vessel {\it Ronald H. Brown} during the NEAQS-ITCT 2004 (New England Air Quality Study-Intercontinental Transport and Chemical Transformation Study) field campaign. Aerosol extinction, scattering and absorption-coefficients were measured using an Optical Extinction Cell (OEC) coupled with an integrating nephelometer and multiwavelength, filter-based absorption photometers (PSAP), respectively, operating on a common inlet at low relative humidity ($<$ 30% RH). The samples were limited to particles $<$ 1$\mu$m to focus on the largely pollution related accumulation mode and to minimize the uncertainty due to highly variable near-surface seasalt aerosol. Additionally, two nephelometers and a second PSAP measured the total and sub-micron scattering and backscattering and total absorption, respectively, at $\sim$ 60% RH. Combining the aerosol scattering and extinction coefficients $\sigma_{sp}$ and $\sigma_{ep}$ yields the single-scattering albedo, $\omega=\sigma_{sp}$/$\sigma_{ep}$, and the absorption coefficient, $\sigma_{ap}=\sigma_{ep}-\sigma_{sp}$. Both are key parameters in estimating aerosol direct radiative forcing and were measured in-situ by the coupled OEC/nephelometer-system. Determining $\sigma_{ap}$ by difference using the OEC and nephelometer data and comparing it with the filter based $\sigma_{ap}$ moreover provides a test of the methods and their uncertainties. Additional parameters to be derived from the OEC and nephelometer measurements are the $\AA$ngstrom exponents for $\sigma_{ep}$, $\sigma_{sp}$, and $\sigma_{ap}$, and the hemispheric backscattering ratio. These are important for relating in-situ optical properties to those sensed remotely, eg., ground optical depth from sun photometry or satellite measured radiance and extinction profiles from lidar. The suite of parameters and wavelength dependence provide constraints on model building and closure studies with physical and chemical aerosol properties. The measured and derived data will be discussed in relation to other measurements and the prevailing meteorology and the upwind sources.
UR: http://saga.pmel.noaa.gov/NEAQS-ITCT/
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting