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. Backscattering in the water was measured with a Hobilabs HS6 6 channel scattering meter. This viewed backscattered light at wavelengths of 442, 488, 532, 589, 620, and 680nm, and at a viewing angle of ~140°. The HS6 was synchronized with a chlorophyll and CDOM fluorometer, and both instruments were lowered on an instrument frame 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 at the CTD sampling stations, but instrument constraints limited the depth of the profiles to 200 m or less. This data was collected during the same cruises as GRIIDC CTD datasets R4.x257.230:0004 (DP01, R/V Point Sur PS1505, https://doi.org/10.7266/N73R0QSX) and R4.x257.230:0010 (DP02, R/V Point Sur PS1606, https://doi.org/10.7266/N7PV6HS1).

Suggested Citation:

Chuanmin Hu, David English, Charles Kovach. 2016. Near surface fluorescence and optical scattering profiles at CTD sampling stations. Cruises DP01 and DP02 from May 2015 - August 2015. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7TM78J6

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 200 m 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:

Time Coordinated Universal Time (UTC), latitude ° (North positive), longitude (-° are West), depth in meters, particulate backscattering attenuation coefficients expressed per meter at individual measurement wavelengths (e.g. the HOBILabs HS6 measured at 420, 442, 470, 532, 590, and 700nm), estimate of the in situ chlorophyll_a concentration (mg per cubic meter), estimate of the CDOM absorption of 400 nm light (attenuation coefficient, with attenuation per meter). Any values missing in the dataset are indicated by "NaN" .

Instruments:

HOBILabs HS6, with scattering measurements at 420, 442, 470, 532, 590, and 700nm WETLabs ECO BBFL2, with measurements of scattering measured at 650nm, red (chlorophyll) fluorescence, and CDOM fluorescence

Individual Files: