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OASIS 2006 meeting, February 2 nd , WHOI

OASIS 2006 meeting, February 2 nd , WHOI. MISC lab report Emmanuel Boss & Wayne Slade. Processed data (available on our FTP site) includes O(12days) of 1min averages of: C-side ac-9. LISST-FLOC. LISST-B. BBRT ( b (117)) Nortek ADV (3D velocity. Acoustic backscattering).

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OASIS 2006 meeting, February 2 nd , WHOI

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  1. OASIS 2006 meeting, February 2nd, WHOI MISC lab report Emmanuel Boss & Wayne Slade • Processed data (available on our FTP site) includes O(12days) of 1min averages of: • C-side ac-9. • LISST-FLOC. • LISST-B. • BBRT (b(117)) • Nortek ADV (3D velocity. Acoustic backscattering). Signs of biofouling are evident in LISST’s data towards the end of the deployment.

  2. Ac-9 data: Cp: Trend towards smaller g Suggests filtration system worked well for 12 days. Large and rapid changes in beam attenuation.

  3. Ac-9 data: Cp: Change of relationship in time (disaggregation ?).

  4. Ac-9 data: Colored dissolved organic material: • Suggests filtration system worked well for 12 days. • 676nm absorption increases as function of time (Organic coating of windows/ instrumental drift). Removal of red signal removes much of the increase. • Influence of particulate resuspension events is not observed.

  5. Combine LISST-B and Floc data: LISST-F 3 random 1min averages samples Black-floc Red-B Petzold, LISST-B Ac-9 Matching LISST-FLOC and LISST-B to obtain the phase function (and ultimately the VSF) in the near forward. How do the beam attenuation’s compare?

  6. LISST-B&FLOC data: Order of beam-c is consistent with acceptance angles (0.02, 0.1, 0.7). High frequency changes in beam attenuation (changes 2-7 fold in < 6 hrs). Drift in LISST relative to ac-9 (t>12) and relative to each other (t>15).

  7. Ac-9, LISST-B&FLOC data: Trend towards higher R • Ratio to cLISST-B varies from 0.35 to 1.0 (Rmedian=0.63, to LISST-F Rmedian=0.57). • Petzold: between 1535% of scattering is between 0.10.8. • Diver visibility ~ 4/c. Which c?

  8. ADV-backscattering, BBRT and cp,ac-9: • bbp/cp ~0.025 throughout. • Acoustic scattering behave differently.

  9. Interesting puzzles: • Size distribution changes as turbidity increase are towards: • Larger particles based on cp spectrum inversion. • Smaller particles, based on LISST inversion & ratio of cac9/cLISST D Single grain Micro floc Macro floc Possible explanation: Resuspended single-grain particles are larger as bottom stress increases. Macro floc break at higher shears becoming smaller. Particulate properties cycle is ~12hr. If shear due to tidal current dominated the stress cycle would be ~6hr. Possible explanation: cycle is driven by interaction of directional waves with the tides.

  10. Still to process: ABS (AQUAScat) Sontek ADV BB-9 A-side ac9 • Issues to discuss: • Calibration of acoustics devices. • Depth resolution of optical properties in future deployments. Papers: Submitted: Optics Express: Calibrating the LISST to obtain VSF. Synthesis: Particle dynamics –floculation, setling and breakup.

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