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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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