Metadata Report for BODC Series Reference Number 1204467

• 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

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

RD Instruments- Ocean Surveyor 75kHz Vessel mounted ADCP.

¹ Ranges at 1 to 5 knots ship speed are typical and vary with situation.
² Single-ping standard deviation.
³ User's choice of depth cell size is not limited to the typical values specified.

Profile Parameters

• Velocity long-term accuracy (typical): ±1.0%, ±0.5cm/s
• Velocity range: -5 to 9m/s
• # of depth cells: 1 - 128
• Max ping rate: 0.7

Bottom Track

Maximum altitude (precision <2cm/s): 950m

Echo Intensity Profile

Dynamic range: 80dB
Precision: ±1.5dB

Transducer and Hardware

Beam angle: 30°
Configuration: 4-beam phased array
Communications: RS-232 or RS-422 hex-ASCII or binary output at 1200 - 115,200 baud
Output power: 1000W

Standard Sensors

Temperature (mounted on transducer)

• Range: -5° to 45°C
• Precision: ±0.1°C
• Resolution: 0.03°

Environmental

Operating temperature: -5° to 40°C (-5° to 45°C)*
Storage temperature: -30° to 50°C (-30° to 60°C)*

*later instruments have greater range.

Web Page

Further details can be found on the manufacturer's website or in the specification sheet

Ashtech Global Positioning System receivers (ADU series)

The ADU series of Global Positioning System (GPS) receivers are designed to give real-time three-dimensional position and attitude measurements. Attitude determination is based on differential carrier phase measurements between four antennas connected to a receiver, providing heading, pitch and roll, along with three-dimensional position and velocity.

The ADU2 model receives information from 48 channels, while the upgraded model (ADU5) uses 56 channels. The ADU5 also features a unique Kalman filter with user selectable dynamic modes to match operating conditions. It also incorporates signals from Satellite Based Augmentation Systems (SBAS) and features an embedded 2-channel 300 kHz beacon receiver for easy differential GPS (DGPS) operations.

Specifications

Further details can be found in the manufacturer's specification sheets for the ADU2 andADU5.

D376 75 kHz and 150 kHz VMADCP Originator Processing

The following information is an adapted summary of the D376 cruise report on the vessel-mounted ADCP (VMADCP).

Configuration and acquisition

RRS Discovery was fitted with a RD Instruments 75kHz (OS75) and 150 kHz (OS150) Ocean Surveyor ADCP at a depth of 5.3m. Positional and attitude information were provided via an Ashtech ADU5 multi-receiver GPS attitude sensor. The RDI proprietary software VMDAS was used to configure the ADCP and perform velocity mapping to the reference frame of the vessel. Bottom tracking was enabled where possible. A suite of MATLAB routines were used to perform data screening and transformation to absolute velocities in Earth coordinates. A summary of the configuration and processing steps is given below.

OS75 VMADCP Configuration:

• No. of bins = 100
• Bin size = 8 m
• Blank after transmit = 8 m
• Transducer depth = 5.3 m
• Bottom track (when on) maximum depth 1100 m
• Time between pings = as fast as possible (typically 5s)
• Low-resolution long-range processing mode

OS150 VMADCP Configuration:

• No. of bins = 96
• Bin size = 4 m
• Blank after transmit = 4 m
• Transducer depth = 5.3 m
• Bottom track (when on) maximum depth 500 m
• Time between pings = as fast as possible (typically 5s)
• Low-resolution long-range processing mode

Summary of Matlab processing steps

The RDI binary file with extension ENX (single-ping ADCP ship referenced data from VMDAS) and extension N2R (ascii NMEA output from ADU5 saved by VMDAS) were read into the MATLAB environment. Ensembles with no ADCP data were removed and ensembles with bad or missing ADU5 GPS heading data were identified and the substituted for the ship's GYRO heading.

The attitude information was time-merged with single ping data and the heading data was used to rotate single ping ADCP velocities from the vessel centreline reference to the True North reference. The transducer misalignment error was corrected for (derived from the misalignment determination - see 'Calibration' below).

The ship's velocity was derived from ADU5 positional information.

Further data screening was performed:

• Max heading change between pings (10 degrees per ping) excluded
• Max ship velocity change between pings (>2ms^-1 pingrate^-1) excluded
• Error velocity greater than double the standard deviation of error velocities of the single ping profile excluded
• All data averaged into 120-second super-ensembles (user selectable - note that the cruise report states 600-second super-ensembles but the data are at 120 second spacing)
• Absolute water velocities were determined from either bottom track derived ship velocity or ADU5 GPS derived ship velocity, dependent on depth

Calibration

D376 operated both on and off the continental shelf so bottom tracking was possible on some program runs. Alignment and amplitude corrections were calculated for and applied to subsets of the data. They were as follows:

OS75 VMADCP Calibration:

• Files 2-6:
  • Misalignment = -3.2881^o
  • Amplitude = 0.996432
• Files 7-11:
  • Misalignment = -3.2512^o
  • Amplitude = 0.995536
• Files 12-16:
  • Misalignment = -3.3509^o
  • Amplitude = 0.996260

OS150 VMADCP Calibration:

• Files 2-6:
  • Misalignment = 0.7324^o
  • Amplitude = 1.006998
• Files 7-11:
  • Misalignment = 0.6319^o
  • Amplitude = 1.007483
• Files 12-16:
  • Misalignment = 0.6601^o
  • Amplitude = 1.007250

D376 75 kHz and 150 kHz VMADCP Processing by BODC

The data to be banked by BODC were received as 6 MATLAB files as follows:

For the 75 KHz VMADCP:

• D376_OS7500x_000000_6_abs.mat; series 2 to 6; 18:47 on 11/06/2012 to 05:52 on 17/06/2012 (Departure from Swansea to start of the Scanfish line to Jones Bank).
• D376_OS7500x_000000_11_abs.mat; series 7 to 11; 05:52 on 17/06/2012 to 13:53 on 22/06/2013 (Start of the Scanfish line to end of the VMP survey).
• D376_OS7500x_000000_16_abs.mat; series 12 to 16; 13:53 on 22/06/2013 to 09:47 on 01/07/2012 (End of the VMP survey to the end of science work).

For the 150 KHz VMADCP:

• D376_OS15000x_000000_6_abs.mat; series 2 to 6; 18:47 on 11/06/2012 to 05:52 on 17/06/2012 (Departure from Swansea to start of the Scanfish line to Jones Bank).
• D376_OS15000x_000000_11_abs.mat; series 7 to 11; 05:52 on 17/06/2012 to 13:53 on 22/06/2013 (Start of the Scanfish line to end of the VMP survey).
• D376_OS15000x_000000_16_abs.mat; series 12 to 16; 13:53 on 22/06/2013 to 09:47 on 01/07/2012 (End of the VMP survey to the end of science work).

The file number corresponds to the highest series number contained therein. Whilst the *_abs.mat files should be sufficient for most purposes, BODC has archived all of the originators source and intermediate files which are available upon request.

Parameter Code Mapping

The received files were reformatted to BODC's internal file format which is a NetCDF subset. Due to the large size of both files *16_abs.mat, it was split into two separate files with the split occurring at midnight on the 26th/27th June.

Note: Despite the files being labelled *OS75* and *OS150*, the variables in both sets of files were named OS75*.

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

The following variables were not included in the transferred data:

Screening

No quality control flags were provided by the originator. The reformatted data were visualised using the in-house EDSERPLO software. Improbable data values were flagged 'M'. Between 1830 and 2330 hours on 23rd June 2012 a period of high water velocity (see LCEWAS01, LCNSAS01) across all bins in the 75 kHz data the were noted by the originators as being erroneous, and these have been flagged as improbable. Some water body velocity channels in the 75 kHz and 150 kHz data (see LCEWAS01, LCNSAS01, LRZAAS01) have a small number of individual bins that exceed the parameter limits and were flagged as improbable, however it may be possible that these may be valid observations which result from intense tidally driven flows over the shelf-break.

In all the files some data cycles were entirely blank including the time and position channels, and these have been deleted. In addition to intermittent absent data cycles, there was a longer period between 04:54:27 on 12/06/2012 and 14:48:25 on 13/06/2012 when data was absent. No other data were edited or deleted.

The cruise report notes that rough weather caused the frequent presence of air bubbles under the hull and across the transducer face resulting in water profiles that were often poor (less than 50% good at depths as shallow as 180 m).

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.

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: