Abstract:

Spectral Absorption and Attenuation data (AC-s meter, Sea-Bird Scientific, WET Labs instrument) was collected underway using the R/V Pelican flow-through system during the Fall cruise on November 2-7, 2015. The AC-s instrument was coupled with temperature and salinity from the ship flow-through system. The data includes the date, time, location, temperature, salinity, absorption (a) and attenuation (c) at 85 wavelengths. The ship flow-through system is located at 2-m depth.

Suggested Citation:

Inia M. Soto Ramos, Robert Arnone, Ryan Vandermeulen. 2017. Spectral Absorption and Attenuation underway data (AC-s meter, Sea-Bird Scientific, WET Labs instrument) collected during Fall R/V Pelican Cruise, November 2-7, 2015. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N71V5CCQ

Purpose:

The AC-s instrument allows to measure the inherent optical properties of the water and can be use to characterize the ocean color and its constituents such as chlorophyll-a, colored dissolved organic matter and detrital material.

Data Parameters and Units:

Year (YYYY), Month (MM), Day (DD), Hour (HH), Minutes (MM), Seconds (SS), Matlab_time (CTZ), Latitude (dd), Longitude (dd), Temperature (C), Salinity (psu), Attenuation coefficient (c; units: m-1; wavelengths: 401.2, 405.5, 409.6, 413.9, 417.8, 422.6, 427.0, 431.5, 435.6, 439.8, 444.4, 449.0, 453.6, 458.2, 462.7, 467.1, 472.0, 477.1, 481.8, 486.7, 491.1, 495.8, 500.5, 505.4, 510.4, 515.2, 520.3, 524.8, 529.4, 534.1, 538.5, 543.0, 547.6, 552.4, 556.9, 561.5, 565.6, 570.0, 574.1, 578.0, 582.0, 586.1, 590.3, 594.7, 599.1, 603.6, 608.3, 612.9, 617.4, 621.9, 626.2, 630.4, 634.7, 639.2, 643.3, 647.6, 652.1, 656.3, 660.9, 665.0, 669.3, 673.4, 677.6, 681.6, 685.6, 689.4, 693.1, 696.6, 700.2, 703.4, 706.8, 710.0, 713.2, 716.6, 719.7, 722.9, 725.4, 728.1, 731.1, 733.4, 735.6, 738.0, 739.9, 741.8, 743.5), Absorption coefficient (a; units: m-1; wavelengths: 403.9, 408.0, 412.1, 416.2, 420.6, 425.4, 429.9, 434.1, 438.2, 442.8, 447.4, 452.2, 456.6, 461.1, 465.7, 470.6, 475.4, 480.4, 485.2, 489.7, 494.4, 498.9, 503.6, 508.5, 513.5, 518.5, 523.0, 527.9, 532.5, 537.2, 541.6, 546.3, 550.7, 555.5, 560.1, 564.4, 568.6, 572.7, 576.6, 581.7, 586.1, 590.3, 594.5, 598.9, 603.3, 608.0, 612.5, 616.9, 621.4, 625.7, 630.0, 634.4, 638.5, 642.8, 647.1, 651.4, 655.8, 660.1, 664.6, 668.7, 672.9, 677, 681.2, 685.0, 688.9, 692.6, 696.0, 699.6, 702.9, 706.2, 709.5, 712.8, 715.8, 718.9, 722.2, 725.1, 727.8, 730.4, 732.7, 735.3, 737.0, 739.4, 741.5, 743.2, 744.8)

Methods:

A CTD (Seabird 19) and Spectral Absorption and Attenuation data (AC-s meter, Sea-Brid Scientific, WET Labs instrument) was connected to the underway flow-through system of the R/V Point Sur. To ensure stability and reliability, the ac-s instrument was placed in a temperature-stabilized water bath to dissipate the instruments’ heat and maintain a constant temperature. The ac-s and CTD was interfaced with a WET Labs DH4 data logger with additional inputs from the ship’s flow-through system (coordinates, time, and date). These inputs were required for the standard protocol corrections during the post processing of the ac-s data. The ac-s instruments were calibrated prior to and post cruise. Calibration of the ac-s included running Nanopure water through the systems using a gravity feed as the instruments were allowed to stabilize for some time interval (≈5 min to ≈10 min). The calibration procedure included obtaining the clear water calibration before and after cleaning the absorption and scattering tubes. An update to instrument device files was applied in real-time if it was deemed that new corrections were necessary to assure good quality measurements. Post processing of the ac-s data will follow the WET Labs protocols (http://wetlabs.com/ac-s). First, the ac-s data is merged and binned with the ship CTD data using the WetLabs Archive Processing Software (WAP). The software can be found here: http://wetlabs.com/software/wet-labs-archive-processing-wap. Water absorption corrections for temperature and salinity will be applied using the ships flow-through data following [Pegau et al., 1997; DOI: 10.1364/ao.36.006035]. The final correction was the scattering correction. For this, we used the method outline in Rottgers et al., 2013 (DOI: 10.1016/j.mio.2013.11.001)

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