Metadata Report for BODC Series Reference Number 1921509
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
RRS James Cook JC145 Navigation Quality Control Report
Position
Position channels look good. Two gaps just at the start and end of the dataset, which can be trimmed off at the end of processing. flags were automatically applied to this.
Heading
Heading channel looks good. There are some large fluctuations within the permitted maximum and minimum parameter values and there are some parts of the datasets where absent values have been recorded. These absent values were automatically flagged.
Bathymetry
All bathymetry channels show a similar pattern. Both the singlebeam and the multibeam data appear noisy because they were set on alternate trigger pulses that recorded data in 5 minute cycles. The singlebeam and multibeam channels follow GEBCO trend for the most part with the exception of times during which both were disabled whilst communication was undertaken with moorings transducers. The overall quality of the singlebeam and multibeam is quite good during the periods it saw use during the cruise. Both channels show a good level of consistency overall but have some unrealistic values where flags were applied. In addition, periods where the singlebeam and multibeam were disabled had absent value readings where flags were automatically applied.
The multi-beam bathymetry is the superior bathymetry and is retained in the dataset.
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
Kongsberg EM120 Multibeam Echosounder
The EM120 is a low frequency (12 kHz) multibeam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.
The main system units of the EM120 are transducer arrays (separate for reception and transmission), preamplifier unit, transceiver unit and operator unit. Sub-bottom profiling capability is an optional extra. For both transmit and receive arrays standard beamwidth is 1° or 2°, and 4° beamwidth is available for the receive array.
The system has 191 beams with pointing angles automatically adjusted according to achievable coverage or operator defined limits. The beam spacing is normally equidistant, corresponding to 1% of depth at 90° angular coverage, 2% at 120° and 3% at 140°. The transmit fan is split into several individual sectors, each of which is corrected independently for vessel roll, pitch and yaw, which places all soundings on a "best fit" to a line perpendicular to the survey line.
The EM120 supersedes the EM12 and was itself superseded by the EM122 in 2008.
Specifications
Frequency | 12 kHz |
Maximum ping rate | 5 Hz |
Range sampling rate | 2 kHz |
Swath coverage sector | up to 150° |
Swath width | up to 5.5 x water depth |
Depth resolution | 10 to 40 cm |
Depth range | 20 to 11,000 m |
Pulse length | 2, 5 and 15 ms |
Number of beams | 191 |
Beam width | 1° x 1° |
Beam spacing (at angular coverage) | 1% of depth at 90° |
Further details can be found in the manufacturer's specification sheet.
RRS James Cook JC145 Navigation Instrumentation
Instrumentation
Manufacturer | Model | Function | Comments |
Trimble/Applanix GPS | POSMV | DGPS, Attitude and Ship Gyrocompasses | The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. |
C- Nav | 3050 | DGPS and DGNSS | C and C Technologies C-Nav3050 satellite positioning system receiver |
Kongsberg Seatex Seapath | Seapath 200 | DGPS | Sensor-based inertial navigation and Differential Global Positioning System (DGPS) receiver unit, providing heading, attitude and position. |
Kongsberg Seatex DPS | DPS 116 | DPS | A 14-channel, all-in-view, L1 GPS receiver which primarily utilises the free, WAAS, EGNOS and MSAS Satellite Based Augmentation Systems (SBAS) for differential corrections (DGPS). |
Sperry Marine Gyro | -Not Specified- | Gyrocompass | |
Kongsberg Maritime | EA600 | Single Beam Echo Sounder | It comprises a standard EA600 single beam echosounder fitted with an additional 10 kHz transducer. The standard EA600 operates up to four high power transceivers simultaneously. Available EA600 standard frequencies span from 12 to 710 kHz with a variable power output of up to 2 kW and a 160 dB dynamic range. |
Kongsberg Maritime | EM120 | Multibeam Echo Sounder | A low frequency (12 kHz) multibeam echosounder with full ocean depth capability. The transducer array includes 191 beams with angular coverage adjustable up to 150 deg and a swath width of up to 5.5 times water depth. The instrument has pulse lengths of 2, 5 and 15 ms and a depth resolution of 10 to 40 cm. |
Sonardyne | Ranger 2 USBL | Ultra Short BaseLine acoustic positioning system | An acoustic positioning system for deep water, long range tracking of underwater targets and position referencing for dynamically positioned (DP) vessels. |
Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)
The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.
There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.
Specifications
POS MV 320
Componenet | DGPS | RTK | GPS Outage |
---|---|---|---|
Position | 0.5 - 2 m 1 | 0.02 - 0.10 m 1 | <2.5 m for 30 seconds outages, <6 m for 60 seconds outages |
Roll and Pitch | 0.020° | 0.010° | 0.020° |
True Heading | 0.020° with 2 m baseline 0.010° with 4 m baseline | - | Drift <1° per hour (negligible for outages <60 seconds) |
Heave | 5 cm or 5% 2 | 5 cm or 5% 2 | 5 cm or 5% 2 |
POS MV WaveMaster
Accuracy | DGPS | RTK | GPS Outage |
---|---|---|---|
Position | 0.5 - 2 m 1 | 0.02 - 0.10 m 1 | <3 m for 30 seconds outages, <10 m for 60 seconds outages |
Roll and Pitch | 0.030° | 0.020° | 0.040° |
True Heading | 0.030° with 2 m baseline | - | Drift <2° per hour |
Heave | 5 cm or 5% 2 | 5 cm or 5% 2 | 5 cm or 5% 2 |
POS MV Elite
Accuracy | DGPS | RTK | GPS Outage |
---|---|---|---|
Position | 0.5 - 2 m 1 | 0.02 - 0.10 m 1 | <1.5 m for 60 seconds outages DGPS, <0.5 m for 60 seconds outage RTK |
Roll and Pitch | 0.005° | 0.005° | 0.005° |
True Heading | 0.025° | 0.025° | Drift <0.1° per hour (negligible for outages <60 seconds) |
Heave | 3.5 cm or 3.5% 2 | 3.5 cm or 3.5% 2 | 3.5 cm or 3.5% 2 |
1 One Sigma, depending on quality of differential corrections
2 Whichever is greater, for periods of 20 seconds or less
Further details can be found in the manufacturer's specification sheet.
RRS James Cook JC145 Navigation Data Processing Procedures
Originator's Data Processing
The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) system into daily NetCDF files. The TECHSAS system is used as the main data logging system on NMF-SS operated reserach vessels. The daily TECHSAS NetCDF navigation and bathymetry files were converted to MSTAR by the originator. These were provided to BODC and used for BODC processing. Data were additionally logged into the RVS Level-C format files which have been archived at BODC. Further details on the MSTAR processing can be found on page 23 of the cruise report
Files delivered to BODC
Filename | Content description | Format | Interval | Start date/time (UTC) | End date/time (UTC) | Comments |
bst_jc145_01.nc | Position (latitude and longitude) (Seapath 350) and True heading (POSMV Gyro) | MSTAR | 30 sec. | 28-Feb-2017 08:30:00 | 08-Mar-2017 00:00:00 | |
sim_jc145_01.nc | Depth of Seafloor (EA600) | MSTAR | 5 min. | 28-Feb-2017 08:30:00 | 08-Mar-2017 00:00:00 | Singlebeam set on alternate trigger pulses that records data in 5 minute cycles. |
em120_jc145_01.nc | Depth of seafloor (EM120) | MSTAR | 5 min. | 28-Feb-2017 08:30:00 | 08-Mar-2017 00:00:00 | Multibeam set on alternate trigger pulses that records data in 5 minute cycles. |
BODC Data Processing
Data were banked at BODC following standard banking procedures. Data were averaged to 60 second intervals.
The originator's variables were mapped to appropriate BODC parameter codes as follows:
bst_jc145_01.nc
Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
time | days since 1899-12-30 00:00:00 UTC | Acquisition time | Not transferred | |||
lat | decimal degrees | Latitude north | ALATGP01 | decimal degrees | none | |
lon | decimal degrees | Longitude east | ALONGP01 | decimal degrees | none | |
Heading_av | degrees | True heading | Not transferred. | |||
Heading_av_corrected | degrees | True heading | HEADCM01 | degree | none |
em120_jc145_01.nc
Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
depth | meters | Depth in Meters | MBANSWCB | meters | none | Multibeam |
sim_jc145_01.nc
Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
depth | meters | Depth in meters | MBANZZ01 | meters | none | Single beam |
All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.
Position
A check was run on positional data to identify gaps and improbable values (through the calculation of speed). There was one gap in the positional data at the start and end of the file, produced during loading to the BODC system. These gaps were trimmed after processing was complete.
Ship Velocities
Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures.
GEBCO
GEBCO bathymetry was added to the file using the main latitude and longitude channels.
Distance Run
Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.
Bathymetry
Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. Both the EM120 multi-beam echosounder and the EA600 single beam echosounder set on alternate trigger pulses that recorded data in 5 minute cycles. Unrealistic noisy values and absent data were flagged using BODC in-house EDSERPLO software. The EA600 Singlebeam and the EM120 multibeam echo-sounder datasets are quality sources of bathymetry and follow GEBCO's trend with a high level of consistency.
The multi-beam bathymetry is the superior bathymetry and is retained in the dataset.
Calibration
No field calibrations have been applied.
Project Information
Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)
Scientific Rationale
There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:
- A mooring array spanning the Atlantic at 26.5°N to measure the southward branch of the MOC (Hirschi et al., 2003 and Baehr et al., 2004).
- Additional moorings deployed in the western boundary along 26.5°N (by Prof. Bill Johns, University of Miami) to resolve transport in the Deep Western Boundary Current (Bryden et al., 2005). These moorings allow surface-to-bottom density profiles along the western boundary, Mid-Atlantic Ridge, and eastern boundary to be observed. As a result, the transatlantic pressure gradient can be continuously measured.
- Monitoring of the northward branch of the MOC using submarine telephone cables in the Florida Straits (Baringer et al., 2001) led by Dr Molly Baringer (NOAA/AOML/PHOD).
The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.
The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:
- Eastern Boundary (EB) array defined as a box with the south-east corner at 23.5°N, 25.5°W and the north-west corner at 29.0°N, 12.0°W
- Mid Atlantic Ridge (MAR) array defined as a box with the south-east corner at 23.0°N, 52.1°W and the north-west corner at 26.5°N, 40.0°W
- Western Boundary (WB) array defined as a box with the south-east corner at 26.0°N, 77.5°W and the north-west corner at 27.5°N, 69.5°W
References
Baehr, J., Hirschi, J., Beismann, J.O. and Marotzke, J. (2004) Monitoring the meridional overturning circulation in the North Atlantic: A model-based array design study. Journal of Marine Research, Volume 62, No 3, pp 283-312.
Baringer, M.O'N. and Larsen, J.C. (2001) Sixteen years of Florida Current transport at 27N Geophysical Research Letters, Volume 28, No 16, pp3179-3182
Bryden, H.L., Johns, W.E. and Saunders, P.M. (2005) Deep Western Boundary Current East of Abaco: Mean structure and transport. Journal of Marine Research, Volume 63, No 1, pp 35-57.
Hirschi, J., Baehr, J., Marotzke J., Stark J., Cunningham S.A. and Beismann J.O. (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophysical Research Letters, Volume 30, No 7, article number 1413 (DOI 10.1029/2002GL016776)
RAPID Climate Change - Atlantic Meridional Overturning Circulation (RAPID-AMOC)
RAPID-AMOC is an £8.4 million, 7 year (2013-2020) research programme that builds on the success of the Natural Environment Research Council's (NERC) RAPID and RAPID-WATCH programmes and will deliver a 16 year long time series of the Atlantic Meridional Overturning Circulation (AMOC).
Background
The Atlantic Meridional Overturning Circulation (AMOC) is a critical element in the energy balance of the global climate system. The AMOC consists of a near-surface, warm northward flow of ocean water, compensated by a colder southward return flow at depth. This heat is transferred from the ocean to the atmosphere at mid-latitudes, with a substantial impact on climate and, in particular, on that of the UK and northwest Europe.
Observing and understanding changes in the AMOC is critically important for identifying the mechanisms of decadal climate variability and change, and for interannual-to-decadal climate prediction. This includes predicting changes in the location, frequency and intensity of Atlantic hurricanes, storms in the North Atlantic and over Europe, shifts in tropical and European precipitation patterns, and the response of sea level to changing radiative forcing. Sustained observations are also critical for assessing the possibility of abrupt change in the AMOC that are known to occur in palaeoclimatic records.
Since 2004 the NERC RAPID and RAPID-WATCH programmes, in partnership with the National Science Foundation and the National Oceanic and Atmospheric Administration in the US, have supported an observing system to continuously measure the AMOC at 26.5°N via a trans-basin array of moored instruments. This measures the basin-wide strength and vertical structure of the AMOC, and its components.
Observations from the array have already revolutionised understanding of AMOC variability and documented its variability on seasonal to interannual timescales. The first few years of observations, demonstrated the feasibility of AMOC measurement, provided new insights into the seasonal cycle, and allowed apparent trends in previous historical 'snapshots' to be seen in the context of natural variability. RAPID-AMOC will extend the AMOC time series.
Objective
RAPID-AMOC's overall objective is to determine the variability of the AMOC, and its links to climate and to the ocean carbon sink, on interannual-to-decadal time scales
This will be achieved by the continued support of the monitoring array and supporting the use of the data in three key areas:
- Application of array data for improved ocean state estimation;
- Use of array data to understand the role of the AMOC in climate variability and predictability;
- Addition of biogeochemical sensors to the array and use to constrain biogeochemical fluxes.
Three projects have been funded to address the objectives of RAPID-AMOC:
- Reanalysis of the AMOC
- DYNamics and predictability of the Atlantic Meridional Overturning and Climate (DYNAMOC)
- Atlantic BiogeoChemical fluxes (ABC Fluxes)
Data Activity or Cruise Information
Cruise
Cruise Name | JC145 |
Departure Date | 2017-02-28 |
Arrival Date | 2017-04-08 |
Principal Scientist(s) | David Smeed (National Oceanography Centre, Southampton) |
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 |