Metadata Report for BODC Series Reference Number 1749720

• 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

OSMOSIS Cruise D381 Vessel Mounted ADCP Data Quality Report

The data were visually inspected and found to be noisy. This variability was generally coherent throughout all depth bins, but was particularly apparent in the shallower bins. Obvious spikes were flagged as suspect, but considerable noisiness remains.

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

Fugro SeaSTAR 9200-G2 Receiver

The SeaSTAR 9200-G2 is a dual frequency (L1/L2) receiver that incorporates global positioning system (GPS) and global navigation satellite system (GLONASS) reception capability while tracking the Fugro L-Band satellite broadcast of Differential Global Satellite Navigation System (DGSNS) corrections. These corrections can also be received via internet, as a backup.

The SeaSTAR 9200-G2 can be used in conjunction with other services as HP (GPS network solution), XP (GPS or orbit and clock solution) and G2 (Composite GPS/GLONASS orbit and clock solution). These are also dual frequency carrier phase solutions, which allows for a decimeter level accuracy.

The 72 channels received by the SeaSTAR include GPS- L1 C/A code and L1/L2/L2C full cycle carrier, GLONASS- L1/L2 full cycle carrier, Satellite Based Augmentation System (SBAS) and the Fugro L-Band service.

Specifications

Further details can be found in the manufacturer's specification sheet.

Originator's Data Processing

Sample collection

A vessel mounted Ocean Survey 75 kHz ADCP was attached to the RRS Discovery during the second of the two legs of the D381 cruise which was undertaken as part of the Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS), funded by NERC.

The ADCP was operational from the ships departure from Falmouth on 14 September 2012 to the study region around the Porcupine Abyssal Plain in the North east Atlantic Ocean; until the ships return to dock on 1 October 2012 .

A hull-mounted Ocean Surveyor broadband 150 kHz ADCP had been operational at the start of the first leg of the D381 cruise which began on 28 August 2012. However part way through the cruise two of the beams stopped reporting velocity. The unit was not able to be repaired on board and was switched off for the entirety of the second leg of the cruise. No data were supplied to BODC for this instrument.

The operational ADCP was mounted in a well 4.15 m forward and 2.5 m to starboard of the 150 kHz well which was 1.75 m to port of the keel, 33 m aft of the bow at the waterline, at an approximate depth of 5.3 m.

Configured by RDI software VmDAS v1.46, the ADCP sampled 96 bins of 8 m lengths over 2 minute intervals using a 30° beam angle. The ADCP was fed with data from the ships GPS, Gyro and ADU systems in order to calculate the true speeds and directions of the currents below the ship.

Data Processing

The ADCP data were processed by RDI software VmDAS v1.46 using routines established during the RRS Discovery cruise D253.

The data were converted into Pstar format, with the velocities scaled to cm/s, the amplitude to 0.45 db, and the time corrected to GPS. An offset of 13 m was applied to the bin depths which equated to the depth of the ADCP below the surface.

The data were then edited according to status flags, where a flag value of 1 indicated bad data. Velocity data where the percentage of pings was greater than 25% when more than one beam had been bad were then replaced with absent data values.

The resulting data were then merged with the navigational files. The velocities were converted to speed and direction so that the heading corrections could be applied before being returned to east and north to apply the misalignment angle and scaling factor.

The time base of the ADCP profile was then shifted to the centre of the 2 minute ensemble.

Field Calibrations

A calibration was achieved using bottom tracking data made available from the departure of the ship from Falmouth.

Using straight, steady speed sections of standard two minute ensemble profiles over reasonably constant bottom depth the following calibrations were derived:

References

Allen, J.T. et al. (2013). 'RRS Discovery Cruise 381, 28 Aug - 03 Oct 2012. Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study'. Cruise Report No. 18, National Oceanography Centre, Southampton.

Processing by BODC of RRS Discovery D381 Vessel Mounted ADCP data

The data arrived at BODC in a single Matlab file which contained the processed data collected from the vessel mounted ADCP during the second of the two legs of the D381 cruise, D381B (14 Sept - 1 Oct 2012).

The data were reformatted to BODC's internal NetCDF format and the following table shows the mapping of variables within the .mat file to the appropriate BODC parameter codes:

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.

Project Information

Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS)

Background

The Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS) consortium was funded to deliver NERC's Ocean Surface Boundary Layer (OSBL) programme. Commencing in 2011, this multiple year study will combine traditional observational techniques, such as moorings and CTDs, with the latest autonomous sampling technologies (including ocean gliders), capable of delivering near real-time scientific measurements through the water column.

The OSMOSIS consortium aims to improve understanding of the OSBL, the interface between the atmosphere and the deeper ocean. This layer of the water column is thought to play a pivotal role in global climate and the productivity of our oceans.

OSMOSIS involves collaborations between scientists at various universities (Reading, Oxford, Bangor, Southampton and East Anglia) together with researchers at the National Oceanography Centre (NOC), Scottish Association for Marine Science (SAMS) and Plymouth Marine Laboratory (PML). In addition, there are a number of project partners linked to the consortium.

Scientific Objectives

• The primary goal of the fieldwork component of OSMOSIS is to obtain a year-long time series of the properties of the OSBL and its controlling 3D physical processes. This is achieved with an array of moorings (two nested clusters of 4 moorings, each centred around a central mooring) and gliders deployed near the Porcupine Abyssal Plain (PAP) observatory. Data obtained from this campaign will help with the understanding of these processes and subsequent development of associated parameterisations.
• OSMOSIS will attempt to create parameterisations for the processes which determine the evolving stratification and potential vorticity budgets of the OSBL.
• The overall legacy of OSMOSIS will be to develop new (physically based and observationally supported) parameterisations of processes that deepen and shoal the OSBL, and to implement and evaluate these parameterisations in a state-of-the-art global coupled climate model, facilitating improved weather and climate predictions.

Fieldwork

Three cruises are directly associated with the OSMOSIS consortium. Preliminary exploratory work in the Clyde Sea (September 2011) to hone techniques and strategies, followed by a mooring deployment and recovery cruise in the vicinity of the Porcupine Abyssal Plain (PAP) observatory (in late Summer 2012 and 2013 respectively). Additional opportunist ship time being factored in to support the ambitious glider operations associated with OSMOSIS.

Instrumentation

Types of instrumentation and measurements associated with the OSMOSIS observational campaign:

• Ocean gliders
• Wave rider buoys
• Towed SeaSoar surveys
• Microshear measurements
• Moored current meters, conductivity-temperature sensors and ADCPs
• Traditional shipboard measurements (including CTD, underway, discrete nutrients, 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: