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North Atlantic Aerosol Radiative Impacts Based on Satellite Measurements and Aerosol Intensive Properties from TARFOX and ACE-2We estimate the impact of North Atlantic aerosols on the net shortwave flux at the tropopause by combining maps of satellite-derived aerosol optical depth (AOD) with model aerosol properties. We exclude African dust, primarily by restricting latitudes to 25-60 N. Aerosol properties were determined via column closure analyses in two recent experiments, TARFOX and ACE 2. The analyses use in situ measurements of aerosol composition and air- and ship-borne sunphotometer measurements of AOD spectra. The resulting aerosol model yields computed flux sensitivities (dFlux/dAOD) that agree with measurements by airborne flux radiometers in TARFOX. It has a midvisible single-scattering albedo of 0.9, which is in the range obtained from in situ measurements of aerosol scattering and absorption in both TARFOX and ACE 2. Combining seasonal maps of AVHRR-derived midvisible AOD with the aerosol model yields maps of 24-hour average net radiative flux changes at the tropopause. For cloud-free conditions, results range from -9 W/sq m near the eastern US coastline in the summer to -1 W/sq m in the mid-Atlantic during winter; the regional annual average is -3.5 W/sq m. Using a non- absorbing aerosol model increases these values by about 30%. We estimate the effect of clouds using ISCCP cloud-fraction maps. Because ISCCP midlatitude North Atlantic cloud fractions are relatively large, they greatly reduce the computed aerosol-induced flux changes. For example, the regional annual average decreases from -3.5 W/sq m to -0.8 W/sq m. We compare results to previous model calculations for a variety of aerosol types.
Document ID
20000052544
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Russell, Philip B.
(NASA Ames Research Center Moffett Field, CA United States)
Bergstrom, Robert W.
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Schmid, Beat
(Bay Area Environmental Research Inst. San Francisco, CA United States)
Livingston, John M.
(SRI International Corp. Menlo Park, CA United States)
Date Acquired
August 19, 2013
Publication Date
February 28, 2000
Publication Information
Publication: Analysis of Atmospheric Aerosol Data Sets and Application of Radiative Transfer Models to Compute Aerosol Effects
Subject Category
Environment Pollution
Meeting Information
Meeting: Sixth Scientific Conference of the International Global Atmospheric Chemistry Project (IGAC)
Location: Bologna
Country: Italy
Start Date: September 13, 1999
End Date: September 17, 1999
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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