Metadata Report for BODC Series Reference Number 1033285
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
Data Description |
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Time Co-ordinates(UT) |
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Parameters |
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Problem Reports
No Problem Report Found in the Database
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
Falmouth Scientific NXIC CTD Series
The FSI NXIC CTD Series is a collection of rugged Conductivity-Temperature-Depth profilers that utilise the patented Non-eXternal Inductive Cell (NXIC) conductivity sensor, which was originally developed for the US Navy DT-705 Sound Velocity/Salinity sensor. The CTDs are fast sampling, fully integrated instruments with optional battery power, datalogging and external analog sensor input.
Models in the collection include the NXIC CT Bio Direct Read-500M, NXIC CTD Bio Direct Read-500M, NXIC CTD Bio Auto-500M, NXIC CTD Direct Read-500M, NXIC CTD Direct Read-700M, NXIC CTD Auto-500M, NXIC CTD Auto-700M, NXIC CTD-ADC with external sensors, and the NXIC ETSG Thermosalinograph. Parameters are measured to an accuracy ranging from 0.002-0.010 mS/cm for conductivity, 0.005 degC for temperature and 0.08% for full scale pressure. Now marketed by Teledyne RD Instruments.
Specifications
| Conductivity | Temperature | Pressure | |
|---|---|---|---|
| Sensor type | Inductive cell | Thermistor | Precision-machined Silicon |
| Range | 0 to 9.0 S m-1 | -5 to 45°C | user specified |
| Accuracy | ± 0.0002 S m-1 | ± 0.005°C | 0.08 % full scale |
| Stability | ± 0.00005 S cm-1 month-1 | 0.0005°C month-1 | ± 0.004 % |
| Resolution | 0.00001 S m-1 | 0.001°C | 0.001 % full scale |
| Response | 5.0 cm at 1 m sec-1 flow | 100 msec | 25 msec |
Further details can be found in the manufacturer's specification sheet and Series Brochure.
Instrument Description
CTD Unit and Auxiliary Sensors
A Sea-Bird Electronics SBE 25 Sealogger CTD unit was used. Water samples were collected with a SBE 35 Carousel, which was attached to the CTD frame. The CTD unit included the following sensors.
| Sensor | Manufacturer | Model | Serial number | Calibration date |
|---|---|---|---|---|
| Pressure | Sea-Bird | 0583 | 2006-06-14 | |
| Temperature | Sea-Bird | 4357 | 2008-02-12 | |
| Conductivity | Sea-Bird | 2864 | 2008-02-08 | |
| Fluorometer | Sea-Tech | 206 | ||
| Transmissometer | Sea-Tech | 238D | 1996-08-02 | |
| Oxygen | Sea-Bird | 0450 | 2008-03-03 |
BODC Processing
Data were received by BODC in one ASCII format file that was subsequently split into 69 separate files, one for each CTD profile. The series were reformatted to the internal QXF format using BODC transfer function 340. Sample calibrations were applied to the conductivity data. The following table details mapping of variables to BODC parameter codes.
| Original parameter name | Original Units | Description | BODC Parameter Code | BODC Units | Comments |
|---|---|---|---|---|---|
| Pressure | Decibars | Pressure exerted by the water column | PRESPR01 | Decibars | |
| Temperature | °C | Temperature of the water column | TEMPST01 | °C | |
| Conductivity | mS cm -1 | Electrical conductivity of the water column calibrated against independent measurements | CNCLCCI1 | S m -1 | Conversion by transfer (mS cm -1 x 0.1). Sample calibrations applied by transfer. |
| Salinity | Salinity of the water column | PSALST01 | Dimensionless | Derived by transfer using UNESCO 1983 algorithm |
Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO. Any data considered as suspect were flagged. Flags from the originator marking suspect data were retained during transfer.
Originator's Data Processing
Sampling Strategy
A total of 69 CTD casts were performed on FRV Alba Na Mara cruise 1709A part b (24 October 2009 - 04 November 2009) in approximately 20 sea lochs along the West Coast and Western Isles, including surveys of lochs South of Mull. The data were collected between 16:02 hours on 24 October 2009 and 19:00 hours on 03 November 2009. Data were supplied in two parts due to a change in CTD equipment.
Water samples were collected in order to obtain independent salinity measurements. The sample data were used to derive calibrations for the conductivity profiles collected by the CTD.
Data Processing
The raw CTD data files were processed through the SeaBird Electronics SeaSoft data processing software following standard procedures. The originators used in-house interactive visual display editing software to edit out individual spikes in the primary temperature and conductivity channels. In addition, a low-pass filter (Sy 1985) was applied to particularly noisy data. An ASCII file was generated for each CTD cast and all files from a cruise were concatenated into one ASCII file which was submitted to BODC.
Sy A., 1985. An alternative editing technique for oceanographic data. Deep Sea Research Part A: Oceanographic Research Papers, 32 (12), 1591-1599.
Field Calibrations
Independent salinity samples, obtained from the sample bottle and spread throughout the cruise, were used to calibrate the CTD conductivity data. Outlying points were discarded, and 59 data points were used to derive the calibrations. The sample analyses yielded a straight line conductivity calibration of the form y = mx + c, where m = 1.020951 and c = -0.829331.
| Parameter | Value of m (y=mx+c) | Value of c (y=mx+c) | Equation |
|---|---|---|---|
| Conductivity | 1.020951 | -0.829331 | C(cal) = 1.020951C(obs) - 0.829331 |
The calibrated and uncalibrated data were submitted to BODC, who applied the appropriate corrections.
Project Information
No Project Information held for the Series
Data Activity or Cruise Information
Cruise
| Cruise Name | 1709A |
| Departure Date | 2009-10-22 |
| Arrival Date | 2009-11-04 |
| Principal Scientist(s) | Matt Gubbins (Marine Scotland Aberdeen Marine Laboratory) |
| Ship | FRV Alba Na Mara |
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 |
