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Aerosol-Induced Radiative Flux Changes Off the United States Mid-Atlantic Coast: Comparison of Values Calculated from Sunphotometer and In Situ Data with Those Measured by Airborne PyranometerThe Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) measured a variety of aerosol radiative effects (including flux changes) while simultaneously measuring the chemical, physical, and optical properties of the responsible aerosol particles. Here we use TARFOX-determined aerosol and surface properties to compute shortwave radiative flux changes for a variety of aerosol situations, with midvisible optical depths ranging from 0.06 to 0.55. We calculate flux changes by several techniques with varying degrees of sophistication, in part to investigate the sensitivity of results to computational approach. We then compare computed flux changes to those determined from aircraft measurements. Calculations using several approaches yield downward and upward flux changes that agree with measurements. The agreement demonstrates closure (i.e. consistency) among the TARFOX-derived aerosol properties, modeling techniques, and radiative flux measurements. Agreement between calculated and measured downward flux changes is best when the aerosols are modeled as moderately absorbing (midvisible single-scattering albedos between about 0.89 and 0.93), in accord with independent measurements of the TARPOX aerosol. The calculated values for instantaneous daytime upwelling flux changes are in the range +14 to +48 W/sq m for midvisible optical depths between 0.2 and 0.55. These values are about 30 to 100 times the global-average direct forcing expected for the global-average sulfate aerosol optical depth of 0.04. The reasons for the larger flux changes in TARFOX include the relatively large optical depths and the focus on cloud-free, daytime conditions over the dark ocean surface. These are the conditions that produce major aerosol radiative forcing events and contribute to any global-average climate effect.
Document ID
20000052529
Document Type
Reprint (Version printed in journal)
Authors
Russell, P. B. (NASA Ames Research Center Moffett Field, CA United States)
Livingston, J. M. (SRI International Corp. Menlo Park, CA United States)
Hignett, P. (Meteorological Office Hampshire United Kingdom)
Kinne, S. (Meteorological Office Hampshire United Kingdom)
Wong, J. (Dalhousie Univ. Halifax, Nova Scotia Canada)
Chien, A. (Symtech Corp. Alameda, CA United States)
Bergstrom, R. (Bay Area Environmental Research Inst. San Francisco, CA United States)
Durkee, P. (Naval Postgraduate School Monterey, CA United States)
Hobbs, P. V. (Washington Univ. Seattle, WA 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
Report/Patent Number
Paper 1998 JD200025
Distribution Limits
Public
Copyright
Other