Metadata Report for BODC Series Reference Number 1224942
Metadata Summary
Problem Reports
Data Access Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
SeaDataNet Quality Flags
Metadata Summary
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Problem Reports
No Problem Report Found in the Database
AMT22 RRS James Cook (JC079) Inherent optical properties - Data Quality Report
The data were screened using the BODC in-house software, Edserplo. Date were flagged in accordance with BODC flagging procedure.
The data had a few spikes across parameters which were flagged as 'M' and were considered to be possible bubbles by the data originator. Negative values that occurred through the dataset for optical parameters were flagged as M. Cycle numbers that had spikes flagged 'M' are given in the table below. Data that exceeded the Null value (-9.00) for ATTNXAC9 at cycle number 853 were flagged as N.
| Parameter | Cycle Numbers Flagged |
|---|---|
| BB117XXX | 438, 854, 1413, 2984, 3059, 3163, 3312, 2984 |
| ATTNXAC9 (ac-s - wavelengths to 730) | 853, 1266, 1267, 1413, 2807, 2808, 2809, 2984,3059, 3163, 3312 |
| ABSPXAC9 (C-Star - wavelengths 526 and 651) | 2984, 3163, 3312 |
| ABSPXAC9 | 854,1266, 1267, 1413, 2807, 2808, 2809, 2984, 3163, 3312 |
The entire bin at wavelength 730 nm the particulate absorption spectrum (ABSPXAC9) was set to zero by the originator's code. These data were flagged as 'M' as the values are either zero, negative or too small to fit within parameter's LFM.
The raw data is available upon request.
Data Access Policy
Public domain data
These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.
The recommended acknowledgment is
"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."
Narrative Documents
WETLabs ac-s in-situ spectrophotometer
The WETLabs ac-s in-situ spectrophotometer is based on the ac-9 flow through sensor offering increased spectral resolution of in-situ absorption and beam attenuation. The ac-s can have 80 (+/- 5) wavelength outputs with a range of 400-730 nm. The ac-s consists of a 10 or 25 cm pathlength, a 4nm resolution, an accuracy of 0.001 - 10 m-1, an operational temperature range of 0 - 30 °C and an operational depth rating of 500 m.
Specification
Mechanical
| Diamater | 10.4 cm |
|---|---|
| Length | 79 cm |
| Weight in air | 5.9 kg |
| Weight in water | 0.8 kg |
Electrical
| Input Voltage | 10-35 VDC |
|---|---|
| Output | RS232, RS485 |
| Current draw | 0.83 A @12 V nominal |
| Connector | MCBH6MP |
Environmental
| Temperature range | 0 - 30°C |
|---|---|
| Depth rating | 500 m |
Optical
| Spectral range | 400 - 730 nm |
|---|---|
| Bandpass (FWHM), nm | 400: 10-18 |
| 450: 10-16 | |
| 550: 10-15 | |
| 650: 10-18 | |
| 730: 10-25 | |
| Pathlength, cm | 10 or 25 |
| Beam cross-section | 8 mm dia. (nominal) |
| Linear dispersion | 6 - 7.0 nm/mm |
| Resolution | 4 nm |
| Precision, 400 to 449 nm | ±0.003 m-1 typ., 0.006 m-1 max @ 1 Hz |
| ±0.005 m-1 typ., 0.012 m-1 max @ 4 Hz | |
| Precision, 450 to 730 nm | ±0.0005 m-1 typ., 0.0015 m-1 max @ 1 Hz |
| ±0.001 m-1 typ., 0.003 m-1 max 4 1 Hz | |
| Accuracy | 0.001 - 10 m-1 |
For more information see the manufacturer's brochure or user guide.
WETLabs C-Star transmissometer
This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.
Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.
This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.
Specifications
| Pathlength | 10 or 25 cm |
| Wavelength | 370, 470, 530 or 660 nm |
| Bandwidth | ~ 20 nm for wavelengths of 470, 530 and 660 nm ~ 10 to 12 nm for a wavelength of 370 nm |
| Temperature error | 0.02 % full scale °C-1 |
| Temperature range | 0 to 30°C |
| Rated depth | 600 m (plastic housing) 6000 m (aluminum housing) |
Further details are available in the manufacturer's specification sheet or user guide.
AMT22 RRS James Cook (JC079) Inherent optical properties - Instrumentation
| Instrument | Serial number | Parameter | Wavelength (nm) |
|---|---|---|---|
| WET Labs C-star(526_nm) Transmissometer | CST687G | ATTNXAC9 | 526 |
| WET Labs C-star(650 nm) Transmissometer | CST686R | ATTNXAC9 | 650 |
| WET Labs ECO-BB3 | BB3-349 | BXXXVSF | 470 and 526 |
| WET Labs ac-s in-situ Spectrophotometer | ACS-007 | ATTNXAC9 | Every 5 nm from 400 to 750 nm |
| WET Labs ac-s in-situ Spectrophotometer | ACS-007 | ABSPXAC9 | Every 5 nm from 400 to 750 nm |
AMT22 RRS James Cook (JC079) Inherent optical properties - Data Processing Documentation
Originator's Processing
Measurements and Methods
Optical measurements were conducted on water passing through the ship's non-toxic flow-through system.
- Beam attenuation co-efficients were measured at 526 and 651 nm by WET Labs C-star transmissometers.
- Hyperspectral beam attenuation and absorption coefficients were also measured between 400 and 750 nm by a WET Labs AC-s.
- The volume scattering function at a central angle of about (117°) was measured by a WET Labs ECO-BB3 at 470 nm and 526 nm.
The data were processed as described by Dall'Olmo (Dall'Olmo et al. 2009, Dall'Olmo et al., 2012) with the use of a 0.2 µm cartridge filter in order to provide a baseline for the absorption and attenuation measurements. The C-star and AC-s optical measurements were averaged into 1-min time intervals before further processing. To compute particulate beam attenuation and absorption coefficients (cp and ap , respectively), the median values of the beam attenuation and absorption coefficients measured during each of the 0.2-µm filtration times were linearly and piecewise interpolated between hours and subtracted from the bulk measurements. This procedure allowed the determination of calibration-independent particulate beam-attenuation and absorption coefficients, with the uncertainties determined mostly by the instrument precision (Boss et al., 2007).
Originator's Quality Control
AC-s cp and ap spectra were further processed to:
- remove a spurious spectral step that was at times observed in the green spectral region
- remove the scattering error from the ap data
- account for variations in sample temperature between consecutive 0.2 µm filtered data points
Calibrations
No calibration files were provided for these AC-s and Cstar data, because these data were derived using the filter-no-filter technique (Dall'Olmo et al., 2009, 2012; Slade et al., 2010). The following scaling factors and uncertainties are given below:
| Wavelength (nm) | Scaling factor (1/(m sr counts)) | Uncertainty (%) |
|---|---|---|
| 470 | 7.4033x10-6 | 8.3 |
| 526 | 4.2179x10-6 | 8.4 |
Wall effects (bb_{wall} see Dall'Olmo et al., 2009) were derived from two measurements of 0.2-um filtered MilliQ water during the cruise. These wall effects were:
| Wavelength (nm) | Wall effect (1/m) | Uncertainty (1/m) |
|---|---|---|
| 470 | 3.7029x10-4 | 0.8327x10-4 |
| 526 | 3.1437x10-4 | 0.5218x10-4 |
Dark counts were also determined during the cruise:
| Wavelength (nm) | Average dark count | Standard Deviation |
|---|---|---|
| 470 | 56.65 | 1.29 |
| 526 | 51.29 | 1.12 |
BODC Processing
The data were received by email as a zipped text file. The data were then transferred to the BODC format and loaded to the database.
Parameter codes defined in the BODC parameter dictionary were assigned to the variable as shown in the table below:
| Originator's Parameter Name | Originator's Units | BODC Parameter Code | BODC Units | BODC Description |
|---|---|---|---|---|
| lat | degrees (+ve N) | ALATZZ01 | Latitude north | Degrees |
| lon | degrees (+ve E) | ALONZZ01 | Longitude east | Degrees |
| cp (particulate beam-attenuation co-efficient) | 1/m | ATTNXAC9 | per metre | Attenuance (unspecified single wavelength) per unit length of the water body by transmissometer and calibration to read zero in clear water |
| ap (particulate beam-absorption co-efficient) | 1/m | ABSPXAC9 | per metre | Light absorbance (unspecified single wavelength) by the water body by transmissometer and calibration to read zero in clear water |
| bbp (particulate backscattering coefficient) | 1/m | BSXXXVSF | per metre | Attenuance due to backscatter (unspecified single wavelength) in the water body by scattering photometer and computation from volume scatter data |
| wavelength | nm | LAMBIN01 | Nanometres | Wavelength of electromagnetic radiation measurement |
N.B. The same parameter was used for the C-Star (cp526 and cp651) attenuation co-efficients as the AC-s attenuation co-efficients.
Screening
Once transferred the reformatted data were imported into the BODC in-house visualisation software, Edserplo.Data were appropriately flagged and double checked for any anomalous results. Further details are given in the data quality report.
References
Dall'Olmo G., Westberry T. K., Behrenfeld M. J., Boss E. and Slade, W. H., (2009). Significant contribution of large particles to optical backscattering in the open ocean. Biogeosciences, 6, pp. 947-967.
Dall'Olmo G., Boss E., Behrenfeld M. J., and Westberry T. K. (2012). Particulate optical scattering coefficients along an Atlantic Meridional Transect. Optics Express, 20, pp. 21532-21551.
Slade W. H., Boss E., Dall'Olmo G., Langner M. R., Loftin J., Behrenfeld M. J., Roesler C., and Westberry T. K. (2010). Underway and moored methods for improving accuracy in measurement of spectral particulate absorption and attenuation. Journal of Atmospheric and Oceanic Technology, 27(10), pp. 1733-1746.
Project Information
No Project Information held for the Series
Data Activity or Cruise Information
Cruise
| Cruise Name | JC079 (AMT22) |
| Departure Date | 2012-10-10 |
| Arrival Date | 2012-11-24 |
| Principal Scientist(s) | Glen A Tarran (Plymouth Marine Laboratory) |
| Ship | RRS James Cook |
Complete Cruise Metadata Report is available here
Fixed Station Information
No Fixed Station Information held for the Series
BODC Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | Below detection limit |
| > | In excess of quoted value |
| A | Taxonomic flag for affinis (aff.) |
| B | Beginning of CTD Down/Up Cast |
| C | Taxonomic flag for confer (cf.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| I | Taxonomic flag for single species (sp.) |
| K | Improbable value - unknown quality control source |
| L | Improbable value - originator's quality control |
| M | Improbable value - BODC quality control |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
SeaDataNet Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
| Flag | Description |
|---|---|
| 0 | no quality control |
| 1 | good value |
| 2 | probably good value |
| 3 | probably bad value |
| 4 | bad value |
| 5 | changed value |
| 6 | value below detection |
| 7 | value in excess |
| 8 | interpolated value |
| 9 | missing value |
| A | value phenomenon uncertain |
| B | nominal value |
| Q | value below limit of quantification |
