Column closure studies of lower tropospheric aerosol and water vapor during ACE-Asia using airborne Sun photometer and airborne in situ and ship-based lidar measurements

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Read Full Article (file size: 7099525 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. D23, 8656, doi:10.1029/2002JD003361, 2003 Column closure studies of lower tropospheric aerosol and water vapor during ACE-Asia using airborne Sun photometer and airborne in situ and ship-based lidar measurements B. Schmid Bay Area Environmental Research Institute, Sonoma, California, USA D. A. Hegg Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA J. Wang Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA D. Bates Physics Department, University of Miami, Coral Gables, Florida, USA J. Redemann Bay Area Environmental Research Institute, Sonoma, California, USA P. B. Russell NASA Ames Research Center, Moffett Field, California, USA J. M. Livingston SRI International, Menlo Park, California, USA H. H. Jonsson Center for Interdisciplinary Remotely Piloted Aircraft Studies, Marina, California, USA E. J. Welton Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA J. H. Seinfeld 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 D. S. Covert Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA O. Dubovik Goddard Earth Sciences and Technology Center, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA A. Jefferson Cooperative Institute for Research in the Environmental Sciences, NOAA Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado, USA Abstract We assess the consistency (closure) between solar beam attenuation by aerosols and water vapor measured by airborne Sun photometry and derived from airborne in situ and ship-based lidar measurements during the April 2001 Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The airborne data presented here were obtained aboard the Twin Otter aircraft. Comparing aerosol extinction σ_ep(550 nm) from four different techniques shows good agreement for the vertical distribution of aerosol layers. However, the level of agreement in absolute magnitude of the derived aerosol extinction varied among the aerosol layers sampled. The σ_ep(550 nm) computed from airborne in situ size distribution and composition measurements shows good agreement with airborne Sun photometry in the marine boundary layer but is considerably lower in layers dominated by dust if the particles are assumed to be spherical. The σ_ep(550 nm) from airborne in situ scattering and absorption measurements are about ∼13% lower than those obtained from airborne Sun photometry during 14 vertical profiles. Combining lidar and the airborne Sun photometer measurements reveals the prevalence of dust layers at altitudes up to 10 km with layer aerosol optical depth (from 3.5 to 10 km altitude) of ∼0.1 to 0.2 (500 nm) and extinction-to-backscatter ratios of 59–71 sr (523 nm). The airborne Sun photometer aboard the Twin Otter reveals a relatively dry atmosphere during ACE-Asia with all water vapor columns <1.5 cm and water vapor densities ρ_w < 12 g/m³. Comparing layer water vapor amounts and ρ_w from the airborne Sun photometer to the same quantities measured with aircraft in situ sensors leads to a high correlation (r² = 0.96), but the Sun photometer tends to underestimate ρ_w by 7%. Received 26 December 2002; accepted 21 April 2003; published 19 August 2003. Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry. Read Full Article (file size: 7099525 bytes) Cited by Citation: Schmid, B., et al. (2003), Column closure studies of lower tropospheric aerosol and water vapor during ACE-Asia using airborne Sun photometer and airborne in situ and ship-based lidar measurements, J. Geophys. Res., 108(D23), 8656, doi:10.1029/2002JD003361. Copyright 2003 by the American Geophysical Union.

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