Abstract:

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 particle present, it is important for understanding variations in Rrs. We measure backscattering in the water with either a 2 channel (700 & 532nm at ~117°), 6 channel (442, 488, 532, 589, 620, 680nm at ~140°), or 2 channel (420 & 700nm) scattering meter. We synchronize this instrument with a chlorophyll and CDOM fluorometer, and lower them on an instrument frame through the upper portion of the water column to obtain vertical profiles of the in situ chl. and CDOM fluorescence, as well as the amount and spectral shape of the backscattering. These profiles will be made at the CTD sampling stations, but instrument constraints will limit the depth of the profiles to <300m. This data was collected during the same cruise as GRIIDC CTD datasets R4.x257.230:0011 and R4.x257.230:0012.

Suggested Citation:

Hu, Chuanmin. 2017. Near surface fluorescence and optical scattering profiles at CTD sampling stations, cruises DP03 and DP04 from January 2016 - December 2016. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N70Z71NN

Purpose:

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 evaluation of the vertical distribution of phytoplankton, particles with little chlorophyll_a, and the concentration of dissolved colored material in the water column.

Data Parameters and Units:

For a variety of depths near the ocean's surface, measurements of optical scattering, Beta(140° @6 wavelengths) (m^-1 sr^-1), and an estimate of the backscattering (bb) at that wavelength (m^-1), relative chl_a fluorescence, and CDOM fluorescence, cruise, cast, time (UTC), latitude (decimal degrees), longitude (decimal degrees), depth (m)

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