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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
Bay Area Environmental Research Institute, Sonoma, California, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA
Physics Department, University of Miami, Coral Gables, Florida, USA
Bay Area Environmental Research Institute, Sonoma, California, USA
NASA Ames Research Center, Moffett Field, California, USA
SRI International, Menlo Park, California, USA
Center for Interdisciplinary Remotely Piloted Aircraft Studies, Marina, California, USA
Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA
Department of Chemical Engineering, California Institute of Technology, Pasadena, California, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Goddard Earth Sciences and Technology Center, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
Cooperative Institute for Research in the Environmental Sciences, NOAA Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado, USA
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.
Citation: (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.
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