Metadata Report for BODC Series Reference Number 1221317

• 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

Problem Reports

No Problem Report Found in the Database

JC088 MetOcean SVP-Iridium Drifter Data Quality Report

End of normal operation

The data originator in collaboration with BODC has identified the following likely point in time at which each drifter is no longer considered to be operating in its intended state, the reason which has been inferred for this end and the explanation for this determination:

N.B. Whilst the drifter may no longer be operating in its intended state, this does not imply that any of the data points are necessarily incorrect. For example the loss of the drogue would mean a drifter is no longer following the movement of water at 15m or 70m depth, instead it is following the movement of the surface water/affected by surface winds, but the positional information remains accurate.

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

Omega KFH series miniature strain gauges

Pre-wired, miniature strain gauges. The series contains linear pattern precision gauges (0.3 mm to 20 mm grids), planar XY pattern (Tee Rosette) (0 / 90°) gauges (0.6 to 6 mm grids) and planar rosette pattern (0 / 45 / 90°) gauges (0.6 to 6 mm grids). All models are available with 1 or 3 meter leads, 120 or 350 nominal resistance (ohms).

Specifications

Further specifications can be found in the manufacturer's data sheet.

U.S. Sensor Ultra Precision Interchangeable Thermistor

A series of interchangeable, resistive thermistors of electrical component size for use in temperature sensing. Epoxy encapsulated with tinned copper allow wires.

Specifications

Navman Jupiter 32 GPS receiver module

A miniature (17.0 x 15.0 mm, 2 g), 20-channel GPS receiver for use in marine buoys. The unit contains a SiRF GSC3 GPS chipset. The Jupiter 32 is the successor to the Jupiter 30. The product was replaced by the Jupiter 32 xLP. Navman Wireless OEM Solutions is now Telit Wireless Solutions.

Sensitivity (assuming a noise value of 3 dB)

Horizontal and positional accuracy

* position error 50%

Timing 1 PPS output

Further specifications and information is available in the manufacturer's data sheet.

JC088 MetOcean SVP-Iridium Drifter Processing by BODC

The data to be banked by BODC were received as 30 csv files, one for each drifter along with a separate header file. The file for drifter 6 contained no useful information due to failure on deployment and was therefore not processed. The original real-time data files are archived at BODC and are available upon request.

Parameter Mapping

The received files were reformatted to BODC's internal file format which is a NetCDF subset.

Due to the high variability of the Iridium position Circular Error Probability and numerous associated inaccurate Iridium positions, it was decided that the data should only be sampled at the frequency of the GPS position fixes. All other data cycles were removed at the reformatting stage. Whilst this decreases the temporal resolution of the data, it provides a dataset with reliable positional information upon which useful trajectory and temperature data is reliant.

The following table shows how the variables within the csv files were mapped to appropriate BODC parameter codes:

EP = Engineering parameter which is not required for the use of environmental data.

Screening

The reformatted data were visualised using the in-house EDSERPLO software. No data values were edited or deleted at this stage. The improbable data value flag 'M' has been applied where the data appear not to represent valid environmental conditions including strain gauge faults and some instances where the temperature sensor values suggest it has been exposed to the air. Differences in the interval between time stamps exist due to occasional variability in the interval between GPS fixes. Details of the end of each drifter's normal operation are documented in the data quality report.

Banking

Once quality control screening was complete, the data were archived in the BODC National Oceanographic Database and the associated metadata were loaded into an ORACLE Relational Database Management System.

MetOcean SVP-Iridium Drifter Originator Processing

Sampling Strategy

Twenty Metocean SVP drifters were deployed on the shelf break at around 47°35'N as part of cruise D376. The were released in 3 groups and transmitted data including GPS location and sea surface temperature every 3 hours.

For further information please see the D376 cruise report.

Data Processing

The real time drifter data including both environmental and engineering parameters was transmitted through the Iridium satellite network. No processing was undertaken on the data by the originator and the near real-time data was supplied to BODC.

JC088 MetOcean SVP-Iridium Drifter Instrumentation

Thirty MetOcean Surface Velocity Program (SVP)-Iridium drifters were deployed on the European continental shelf break between 55° 12.00' N, 10° 04.52' W and 55° 10.21 N, 10° 05.36 W, on the 17/7/13 to track currents at 15 m and 70 m depth. The SVPs consisted of a spherical surface unit and an underwater holey-sock drogue attached by a long tether.

The surface buoy was made from injection moulded high impact ABS and contained the communications and sensors. It was equipped with a bi-directional Iridium 9601 Short Burst Data transceiver satellite system communications link, which also provided hourly position information. More accurate position information was provided by a Navman Jupiter 32 GPS System module every three hours. The drifter was equipped with a US Sensor Ultra Precision Thermistor sea surface temperature sensor and battery voltage sensor.

The SVP drifter was equipped with a strain gauge drogue presence system to indicate whether the drogue was attached, under increased strain such as during high wave activity or when grounded, or had lost the drogue. The manufacturer supplies the drogue with a tether made from plastic coated stainless steel cable, which centres the drogue at 15m depth (short tether). However the tethers on 15 of the 30 drifters were modified to place the drogues at a depth of 70 m (long tether) to attempt to track water below the mixed layer.

Further information can be found in the product datasheet and the product manual

As described in the cruise report , the drifters were deployed as one group in alternating order (1 long tether, 1 short tether, 1 long tether, and so on) over the 600 m isobath during a period of 1 hour and 20 minutes. The 600 m isobath was chosen as a release site as other experiments had indicated the presence of a slope current in this depth of water.

Project Information

Fluxes Across Sloping Topography of the North East Atlantic (FASTNEt)

Background

The FASTNEt consortium was funded to deliver NERC's Ocean Shelf Edge Exchange Programme. Commencing in October 2011, this four year study aims to couple established observational techniques, such as moorings and CTDs, with the very latest in autonomous sampling initiatives - including use of Autosub Long Range and gliders. With the aid of novel model techniques, these observations will be utilised to construct a new paradigm of Ocean/Shelf exchange.

Shelf edge regions mark the gateway between the world's deep oceans and shallower coastal seas, linking terrestrial, atmospheric and oceanic carbon pools and influencing biogeochemical fluxes. Shelf edge processes can influence near-shore productivity (and fisheries) and ultimately affect global climate.

FASTNEt brings together researchers from multiple UK organisations. Further collaboration has been established with five Project Partners: the UK Met Office, Marine Scotland Science, Agri-Food and Biosciences Institute, Marine Institute Ireland and Scripps Institution of Oceanography.

Scientific Objectives

• To determine the seasonality of physical gradients and exchange across the shelf edge by deploying new observational technologies (gliders, Autosub Long Range) and established techniques (long term moorings, drifters)
• To quantify key exchange mechanisms and to collect new data targeted at testing and improving high resolution models of the shelf edge, by carrying out detailed process studies in contrasting regions of the shelf edge of the NE Atlantic margin
• To develop a new parameterisation of shelf edge exchange processes suitable for regional-scale models, using improved resolution numerical, and new empirical models constrained by the observations
• To test the new parameterisations in a regional model in the context of making an assessment of inter-annual variability of ocean-shelf exchange.

Fieldwork

Three survey sites on the UK shelf edge have been selected for FASTNEt. These are a) the Celtic Sea shelf edge, b) Malin shelf and c) North Scotland shelf. Fieldwork is centred around two research cruises. The first, to the Celtic Sea, on RRS Discovery in June 2012. The second cruise visits the Malin shelf on RRS James Cook, during summer 2013. In addition to these dedicated cruises, opportunist cruise activity to the North Scotland shelf has been agreed with project partner Marine Scotland Science. Autonomous technologies will complement observations made during the cruises and provide knowledge of seasonal and inter-annual variability in exchange processes.

Instrumentation

Types of instruments/measurements:

• Gliders
• Autosub Long Range
• Drifter buoys
• Scanfish
• Microstructure profilers
• Moored CTD/CT loggers and ADCPs
• Shipboard measurements: CTD, underway, nutrients (and other discrete sampling), LADCP, ADCP.

Contacts

Data Activity or Cruise Information

Cruise

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: