Acceptance angle effects on the beam attenuation in the ocean

Boss, EB, Slade, WH, Behrenfeld, M and Dall’Olmo, G 2009 Acceptance angle effects on the beam attenuation in the ocean. OPTICS EXPRESS, 17 (3). 1535-1550. https://doi.org/10.1364/OE.17.001535

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Abstract/Summary

The beam attenuation serves as a proxy for particulate matter and is a key parameter in visibility algorithms for the aquatic environment. It is well known, however, that the beam attenuation is a function of the acceptance angle of the transmissometer used to measure it. Here we compare eight different transmissometers with four different acceptance angles using four different deployment strategies and sites, and find that their mean attenuation values differ markedly and in a consistent way with instrument acceptance angle: smaller acceptance angles provide higher beam attenuation values. This difference is due to variations in scattered light collected with different acceptance angles and is neither constant nor easy to parameterize. Variability (in space or time) in the ratios of beam attenuations measured by two different instruments correlates, in most cases, with the particle size parameter (as expected from Mie theory), but this correlation is often weak and can be the opposite of expectations based on particle size changes. We recommended careful consideration of acceptance angle in applications of beam transmission data especially when comparing data from different instruments. (C) 2009 Optical Society of America

Item Type:	Publication - Article
Subjects:	Marine Sciences Oceanography
Divisions:	Plymouth Marine Laboratory > National Capability categories > National Centre for Earth Observation
Depositing User:	Giorgio Dall'Olmo
Date made live:	03 Jun 2014 15:40
Last Modified:	25 Apr 2020 09:56
URI:	https://plymsea.ac.uk/id/eprint/6022

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