Improving accuracy measurement of optical properties
Download 0.91 Mb.
|
Figure CaptionsFigure 1 – Example flow through system setup. Seawater inflow can be diverted using a three-way ball valve (a) through a 0.2 μm filter (b) or directly to the ac-9 (or ac-s) instrument (d). A stopcock or needle valve (c) with quick-disconnect fitting is used to control flow rates to the instrument and facilitate its removal for cleaning. A volume flow sensor (e) is used to assess fouling of the filter over time. A check valve (f) ensures that no air is drawn into the instrument under a no-flow condition. Figure 2 – (A) Example of uncorrected particulate absorption spectrum (solid line) showing a spectral anomaly between 710 and 750 nm. The continuous lines with circles and triangles represent the spectra derived from using standard correction procedures, Eq. 3\* MERGEFORMAT (), and the residual temperature correction, Eq. 5\* MERGEFORMAT (), respectively. The derived  for this sample data was approximately 0.13 °C. (B) The pure water temperature dependence,  from [Sullivan et al. 2006]. Note the spectral features in  centered near 600 and 740 nm, and that the manufacturer-specified uncertainty is ± 0.005 m-1.
Figure 3 – (A) One-fifth of the one-minute binned, uncorrected  spectra recorded on day 31 of the cruise. (B) Spectra with only the scattering correction applied. (C) Spectra with scattering and traditional temperature and salinity corrections applied. (D) spectra corrected using Eq. 5\* MERGEFORMAT () and the  derived by minimizing Eq. 6\* MERGEFORMAT (). Insets show the red−NIR region where the effects of inaccurate are most apparent. Note the presence of negative in the visible range in (B) and (C).
Figure 4 – (A) Frequency distribution of the measured Figure 5 – Comparison of Figure 6 – Time-series of particle absorption and attenuation measured during a transect crossing the Equator at 125° W. (A) Four hours of high resolution ac-s data from 27 August 2006 shows periodic FSW measurements which are interpolated and subtracted from TSW data. Red traces represent the one-minute binned data mean and plus or minus one standard deviation. (B) Computed Figure 7 – Raw time-series of measured total attenuation (A) and filtered absorption (B). Particle size as indicated by γ derived from spectral beam attenuation. (D) Measured flow rate during the periodic filtered samples (some data are missing due to logging malfunction). Red vertical lines denote filter cartridge replacement by divers. Figure 8 – Flowthrough installed in bilge of R/V Tara, currently underway on three-year mission to measure ocean properties. Flowing seawater enters system at Vortex de-bubbler (A) before three-way electrically-actuated valve (B), which sends flow directly to ac-s instrument (C), or diverts it through 0.2 μm cartridge filter (D) before entering ac-s instrument. Seawater flow is measured using paddle-wheel flow sensor (E). Valve controller and logging computer are located in dry lab space.  
Figure 1 – Example flow through system setup. Seawater inflow can be diverted using a three-way ball valve (a) through a 0.2 μm filter (b) or directly to the ac-9 (or ac-s) instrument (d). A stopcock or needle valve (c) with quick-disconnect fitting is used to control flow rates to the instrument and facilitate its removal for cleaning. A volume flow sensor (e) is used to assess fouling of the filter over time. A check valve (f) ensures that no air is drawn into the instrument under a no-flow condition. 
Directory: documents documents -> Concept stage documents -> Concept stage documents -> The great global switch-off documents -> Nonprofit grant application documents -> The Truth about the Rwandan Genocide documents -> Annual InStructional unit plan documents -> Chaos equipment included Download 0.91 Mb. Share with your friends:
|
determined by flow-through ac-9 and filter pad measurements. Data are shown for measurements made at440 nm, for two different β-correction methods: (A) for the Roesler (1998) 
correction, and (B) for the Bricaud and Stramski (1990) empirical correction. Black lines denote 1:1 relationship.