Clear-column radiative closure during ACE-Asia: Comparison of multiwavelength extinction derived from particle size and composition with results from Sun photometry

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Read Full Article (file size: 1986053 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D23, 4688, doi:10.1029/2002JD002465, 2002 Clear-column radiative closure during ACE-Asia: Comparison of multiwavelength extinction derived from particle size and composition with results from Sun photometry J. Wang Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA R. C. Flagan Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA J. H. Seinfeld Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA H. H. Jonsson Department of Meteorology, Naval Postgraduate School, Monterey, California, USA D. R. Collins Department of Atmospheric Sciences, Texas A&M University, College Station, Texas, USA P. B. Russell NASA Ames Research Center, Moffett Field, California, USA B. Schmid Bay Area Environmental Research Institute, Sonoma, California, USA J. Redemann Bay Area Environmental Research Institute, Sonoma, California, USA J. M. Livingston SRI International, Menlo Park, California, USA S. Gao Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA D. A. Hegg Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA E. J. Welton NASA Goddard Earth Sciences and Technology Center and University of Maryland Baltimore County, Greenbelt, Maryland, USA D. Bates Physics Department, University of Miami, Coral Gables, Florida, USA Abstract From March to May 2001, aerosol size distributions and chemical compositions were measured using differential mobility analyzers (DMA), an aerodynamic particle sizer (APS), Micro-Orifice Uniform Deposit Impactors (MOUDI), and denuder samplers onboard the Twin Otter aircraft as part of the Aerosol Characterization Experiment (ACE)-Asia campaign. Of the 19 research flights, measurements on four flights that represented different aerosol characteristics are analyzed in detail. Clear-column radiative closure is studied by comparing aerosol extinctions predicted using in situ aerosol size distribution and chemical composition measurements to those derived from the 14-wavelength NASA Ames Airborne Tracking Sun photometer (AATS-14). In the boundary layer, pollution layers, and free troposphere with no significant mineral dust present, aerosol extinction closure was achieved within the estimated uncertainties over the full range of wavelengths of AATS-14. Aerosol extinctions predicted based on measured size distributions also reproduce the wavelength dependence derived from AATS-14 data. Considering all four flights, the best fit lines yield Predicted/Observed ratios in boundary and pollution layers of 0.97 ± 0.24 and 1.07 ± 0.08 at λ = 525 nm and 0.96 ± 0.21 and 1.08 ± 0.08 at λ = 1059 nm, respectively. In free troposphere dust layers, aerosol extinctions predicted from the measured size distributions were generally smaller than those derived from the AATS-14 data, with Predicted/Observed ratios of 0.65 ± 0.06 and 0.66 ± 0.05 at 525 and 1059 nm, respectively. A detailed analysis suggests that the discrepancy is likely a result of the lack of the knowledge of mineral dust shape as well as variations in aerosol extinction derived from AATS-14 data when viewing through horizontally inhomogeneous layers. Published 5 December 2002. Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305). Read Full Article (file size: 1986053 bytes) Cited by Citation: Wang, J., et al. (2002), Clear-column radiative closure during ACE-Asia: Comparison of multiwavelength extinction derived from particle size and composition with results from Sun photometry, J. Geophys. Res., 107(D23), 4688, doi:10.1029/2002JD002465. Copyright 2002 by the American Geophysical Union.

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