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Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other MeasurementsThe Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances. More tests are needed of the consistency among different methods and of the effects of changing humidity on aerosol.
Document ID
20010092160
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Russell, Philip B.
(NASA Ames Research Center Moffett Field, CA United States)
Redemann, J.
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Schmid, B.
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Livingston, J. M.
(SRI International Corp. Menlo Park, CA United States)
Bergstrom, R. W.
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Ramirez, S. A.
(Symtech Corp. United States)
Hipskind, R. Stephen
Date Acquired
August 20, 2013
Publication Date
January 15, 2001
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: Chapman Conference on Atmospheric Absorption of Solar Radiation
Location: Estes Park, CO
Country: United States
Start Date: August 13, 2001
End Date: August 17, 2001
Funding Number(s)
PROJECT: RTOP 622-44-75-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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