HR: 0800h
AN: A31A-0806    [Abstracts]
TI: Multiwavelength In-Situ Aerosol Scattering and Absorption During the NEAQS-ITCT 2004 Field Campaign: Aerosol Classification, Case Studies, and Data Interpretation
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
EM: dcovert@u.washington.edu
AF: University of Washington, Department of Atmospheric Sciences, Box 351640, Seattle, WA 98195 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
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
EM: tim.bates@noaa.gov
AF: NOAA Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115 United States
AB: In-situ, three wavelength measurements of aerosol scattering and absorption of the New York and Boston urban pollution outflow were carried out aboard the NOAA research vessel Ronald H. Brown during the NEAQS-ITCT 2004 (New England Air Quality Study-Intercontinental Transport and Chemical Transformation Study) field campaign during July 2004 in the Gulf of Maine. Aerosol scattering, backscattering and absorption-coefficients were measured using integrating nephelometers and multiwavelength, filter-based absorption photometers (PSAPs) at ~55-60% RH (nephelometers). Two data sets were collected, one for particles with diameters d_p<10μm and one for particles <1μm. The purpose of the latter was to focus on the largely pollution related accumulation mode and to minimize the uncertainty due to highly variable near-surface sea salt aerosol. Combining the aerosol scattering and absorption coefficients σ_sp and σ_ap yields the derived, intensive parameters, single-scattering albedo, ω=σ_sp/(σ_sp+σ_ap), Ångström exponents, å, for σ_sp, and σ_ap, the hemispheric backscattering ratio, and the fine mode fraction of the aerosol, FMF =σ_sp(d_p<1μm)/σ_sp(d_p<10μm). These are key parameters in estimating aerosol direct radiative forcing and they provide constraints on model building and closure studies with physical and chemical aerosol properties. They are important for relating in-situ optical properties to those sensed remotely, e.g., optical depth from ground- or aircraft-based sun photometry or optical depth from satellite, and to the FMF retrieved from satellite data. The measured and derived data will be classified based on a trajectory analysis of the sampled air masses to identify distinct aerosol populations and sources. Case studies describing the aging of pollution plumes are calculated and analyzed in context of other measurements and the prevailing meteorology and the upwind sources. The obtained relationship between in-situ Ångström and FMF will be compared to earlier field-campaigns (INDOEX, ACE Asia, NEAQS 2002) and in context of current satellite retrieval results.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 3359 Radiative processes
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005