Coleman, J. E. US Naval Academy,
, . E. ,

The contribution of particles in a given size range to total backscatter (bb) is a function of their backscattering efficiency, number, and cross-sectional area. By utilizing Junge and Mie theories, backscattering efficiency and number of particles become functions of particle size, thereby allowing the contribution of a particular size range to total bb to be parameterized as functions of particle size and the slope of the Junge distribution. I evaluated the relative contributions of different size particles to total bb in waters surrounding the San Juan Islands, Washington. For Junge slopes of m=3 and greater, the backscattering signal should be derived almost entirely from particles less than 0.2 microns. Particles of this size fall under the operational definition of colored dissolved organic material (CDOM). I tested the assumption that CDOM absorption could be used as a proxy for the concentration of particles less than 0.2 microns by evaluating the correlation between bb and CDOM absorption. This relationship was tested utilizing HOBILabs Hydroscat-6 backscatter, 0.2-micron filtered AC-9 absorption, and Coulter Multisizer II particlesize distribution (1-60 microns). For waters with a Junge slope m=2, no correlation was found. However, in waters with a kinked Junge distribution, (i.e., m=2 for larger particles and m greater than 3 for particles less than 0.2 microns), 75-80% of the bb signal is expected to be derived from particles less than 0.2 microns.
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
Code: SS53TH1113S