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Proceedings Paper

A model for the assessment of UV penetration into ocean waters from space-based measurements and full radiative transfer calculations
Author(s): Alexander P. Vasilkov; Jay R. Herman; Ziauddin Ahmad; B. Gregory Mitchell; Mati Kahru
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Paper Abstract

Increased levels of biologically harmful Uv radiatonhave beenshown to affec aquatic ecosystems, marine photocynmetiry, and their imapct on carbon cycling. A quantiative assessment of UV effectw requires an estimate of the in-water raiationfield. An esitmate of underwater UV radiatonis porosed based on satellit meausrments fromthe TOMS and SeaWiFS and modesl fo radiatve transfer (RT). The Hydrolight code, modified toe xtnd it to the 290 - 400 nm wavleength range, is used for REt calucaitons in theocean. Solar direc tandidffuse radiances at the ocean surfce are calculated using a fulll RT code for clear-sky coditions, whicha re then modified for clouds and aerosols.Teh TOMS total column ozone and reflectivity productsa reinputs for RT calcuaitons in the atmosphere. An essential component of the in-water RT model is a model of seawater inherent optical properties (IOP). The IOP model is an extension of the Case-1 water model to the UV spectral region. Pure water absorption is interpolated between experimental datasets available in the literature. A new element of the IOP model is parameterization of particulate matter absorption in the UV based on recent in situ data. The SeaWiFS chlorophyll product is input for the IOP model. The in-water computational scheme is verified by comparing the calculated diffuse attenuation coefficient Kd, with one measured for a variety of seawater IOP. The calculated Kd is in a good agreement with the measured Kd. The relative RMS error for all of the cruise stations is about 20%. The error may be partially attributed to variability of solar illumination conditions not accounted for in calculations. The conclusion is that we are now able to model ocean UV irradiances and IOP properties with accuracies approaching those visible region, and in agreement with experimental in situ data.

Paper Details

Date Published: 4 November 2003
PDF: 7 pages
Proc. SPIE 5156, Ultraviolet Ground- and Space-based Measurements, Models, and Effects III, (4 November 2003); doi: 10.1117/12.506030
Show Author Affiliations
Alexander P. Vasilkov, Science Systems and Applications, Inc. (United States)
Jay R. Herman, NASA Goddard Space Flight Ctr. (United States)
Ziauddin Ahmad, Science and Data Systems, Inc. (United States)
B. Gregory Mitchell, Scripps Institution of Oceanography (United States)
Mati Kahru, Scripps Institution of Oceanography (United States)


Published in SPIE Proceedings Vol. 5156:
Ultraviolet Ground- and Space-based Measurements, Models, and Effects III
James R. Slusser; Jay R. Herman; Wei Gao, Editor(s)

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