Near surface fluorescence and optical scattering profiles at CTD sampling stations, cruise DP05, May 2017

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2017-05-02 to 2017-05-12


Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC)




Optical absorption and scattering are the primary determinants of the flow of radiant energy in the ocean’s surface waters. Particles in the water are the principle source of scattering, and the scattering measurements can indicate the amount and/or type of particles present. While a complete measurement of the scattered light field is complex and cumbersome, a measurement of the backscattering at particular angles can usually be related to the total backscattering of light. The backscattering of light not only provides information about the particles present, it is important for understanding variations in remote sensing reflectance. We measure backscattering in the water with 6 channels (442, 488,532,589,620, 680nm at ~140°) and 700nm (at ~117°) scattering meters. These instruments also measure chlorophyll fluorescence. The instruments are lowered through the upper portion of the water column to obtain vertical profiles of the in situ chlorophyll and CDOM fluorescence, as well as the amount and spectral shape of the backscattering. These profiles were made at most of the CTD sampling stations, but instrument constraints limit the depth of the scattering profiles to <300m. This data was collected during the same cruise as GRIIDC CTD datasets R4.x257.230:0013.


The combination of in situ backscattering and fluorescence measurements can be used to examine the amount and type of particles is the water column. Profiles of the measurements through the upper 200m of the water column allow estimation of the vertical distribution of phytoplankton particles with little chlorophyll-a, and the concentration of dissolved colored material in the water column.

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