Metadata Report for BODC Series Reference Number 1221575
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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Time Co-ordinates(UT) |
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Parameters |
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Problem Reports
No Problem Report Found in the Database
AMT20 RRS James Cook (JC053) Underway Dissolved Nitrous Oxide Data Quality Report
Data Quality Report
The data had undergone quality control by the originator. Limited BODC flagging was applied.
Data Access Policy
Open Data supplied by Natural Environment Research Council (NERC)
You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."
Narrative Documents
Los Gatos Research (LGR) Inc. N2O and CO Analyser
Basic Information
The Los Gatos Research (LGR) N2O/CO Analyser can measure ambient levels of N2O/CO in real time with a precision better than 0.1 ppb in 1 second. The model N2O/CO-23-d reports water vapour as mole fraction simultaneously. The analyser makes use of LGR's Off-axis Internal Cavity Output Spectroscopy (OA-ICOS), which is a laser absorption technology.
Performance Specifications
| Precision(1σ, 1 second / 3 minutes): | N2O: 0.1 ppb / 0.050 ppb |
|---|---|
| CO: 0.1 ppb / 0.050 ppb | |
| H2O: 50 ppm / 10 ppm | |
| Measurement Rates: | All parameters measured simultaneously at user-selectable rates up to 10 Hz (optional pump required for flow rates >1Hz) |
| Maximum Drift (Exhanced Performance models)(15 min average, at STP, over 24 hrs): | N2O: 0.1 ppb |
| CO: 0.1 ppb | |
| H2O: 50 ppm or 1% reading, whichever greater | |
| Linear Dynamic Range (meets all specs): | N2O: 5 - 4000 ppb |
| CO: 5 - 4000 ppb | |
| Dynamic Range: | N2O: 0 - 10 ppm |
| CO: 0 - 10 ppm | |
| Temperature/Humidity: | Sample Temperature: -30 to 50 °C |
| Operating Temperature: 10 - 35 °C (Standard Model) 0 - 45 °C (Enhanced PerformanceModel) | |
| Ambient Humidity: non-condensing (0-100% RH) |
Other information
| Dimensions (rackmount compatible): | 19" x 30" x 14" (Standard Model) |
|---|---|
| 17" x 34" x 17.5" (Enhanced Performance Model) | |
| Weight: | 36 kg (Standard Model) |
| 68 kg (Enhanced Performance Model) | |
| Fittings: | Inlet: 3/8" |
| Outlet (internal pump): 1/4" | |
| Outlet (optional external vacuum pump): 1/2" |
Further information may be found in the LGR specification sheet.
AMT20 RRS James Cook (JC053) Underway Dissolved Nitrous Oxide Instrumentation
| Instrument | Model number | Parameter |
|---|---|---|
| Los Gatos Research N2O/CO ICOS Analyser | N2O/CO-23d | Dissolved Nitrogen Oxide |
AMT20 RRS James Cook (JC053) Underway Dissolved Nitrous Oxide Processing Document
Originator's Processing
Measurements and Methods
An N2O/CO ICOS analyser was coupled with a percolating packed bed equilibrator for continuous measurements in the surface ocean. Water flow through the equilibrator from the ship's pumped seawater supply was set to 1.8 L min-1. The water temperature in the equilibrator and the headspace were measured with two Pt100 temperature probes, and recorded every 10 seconds to monitor temperature changes between the seawater intake and equilibrator. Water vapour in the circulating gas headspace was reduced with a cold trap (5°C). Residual H2O was measured by the instrument for calculation of N2O dry mole ratios. A basic linear interpolation was applied to the latitude and longitude to get a higher spatial resolution.
Calibrations
Dried Air with 323.7 nmol mol-1 N2O was used as a working reference, calibrated against IMECC/NOAA primary standards. Every 8 hours, the analyser was calibrated by switching from equilibrator headspace to the reference gas for 20 minutes. This was followed by another reference measurement after 40 minutes to assess short-time drift. Only the last 5 minutes of each measurement were analysed to allow for complete flushing of the measurement cell. For the first 15 minutes after switching back to the equilibrator headspace or to the marine air measurements were not used for evaluation. Instrument offset and drift were corrected with a linear interpolation between reference gas measurements.
Originator's Quality Control
As mentioned above for calibrations, the first 15 minutes after a change of gas streams were discarded from the evaluation to allow for measurement cell and equilibrator flushing. The same was done after any changes to the setup (e.g. re-adjustment of water flow through equilibrator, pausing the analyser for maintenance). When change of water flow through the equilibrator was noticed, data back to the last observation of correct water flow were flagged.
BODC Processing
Data were submitted to BODC as a .mat file containing the data as 4 double arrays, consisting of date and time, N2O, latitude and longitude. In addition to the .mat file a Microsoft Word document was submitted containing the methodology. The data was 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 |
|---|---|---|---|---|
| N2O partial pressure in ppb | Parts per billion (ppb) | MXRM2OMS | Nanomoles per litre | Mixing ratio (equilibrated marine sample) of nitrous oxide |
| Latitude | ALATGP01 | Degrees | Latitude north (WGS84) by unspecified GPS system | |
| Longitude | ALONGP01 | Degrees | Longitude east (WGS84) by unspecified GPS system |
Screening
Suspect data was flagged 'M' as suspect following screening.
Project Information
Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)
The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.
The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:
- give early warning of any fundamental change in Atlantic ecosystem functionng
- improve forecasts of the future ocean state and associated socio-economic impacts
- provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.
The specific objectives are:
- To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
- To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
- To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases
The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).
More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10
Weblink: http://www.oceans2025.org/
Data Activity or Cruise Information
Cruise
| Cruise Name | JC053 (AMT20) |
| Departure Date | 2010-10-12 |
| Arrival Date | 2010-11-25 |
| Principal Scientist(s) | Andrew Rees (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 |
