Metadata Report for BODC Series Reference Number 1742677

• 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

From examination of the periods when the recorded pressure is significantly greater than the nominal depth of the moored instrument, BODC consider that for the following periods, data quality is significantly affected by knockdown of all the moorings:

• Beginning of the mooring deployment to 23rd September 2012.
• 27th January 2013 to 31st January 2013.
• 16th February 2013 to 20th February 2013.
• 6th March 2013 to 7th March 2013.
• 20th April 2013 to 25th April 2013.
• 3rd May 2013 to 8th May 2013.
• 21st May 2013 to 8th June 2013.

During these periods, all parameters have been flagged as suspect and users are advised to use this data with extreme caution.

OSMOSIS RRS Discovery D381A and D381B Moored Current Meter Quality Report

The data originator notes that the quality of this data varies, in that the vertical gradient tends to show pronounced errors at 150m. It was not possible to fully explain or resolve this feature, but it was thought that it could relate to acoustic reverberation from nearby instruments or mooring-related structures.

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

Nortek Aquadopp Open Water Current Meter

This instrument provides 3D acoustic doppler current measurements along with standard measurements of temperature, pressure, tilt and direction. It can be used in real time measurement situations or can log to an internal recorder powered by internal batteries. It can also be configured to measure surface wave height, period and direction concurrently. It has the unique feature of being run in 'diagnostic' mode when set to collect data at 1 Hz frequency in user specified intervals. This allows studies of mooring motion and the performance of other current meters to be conducted. It can be set in various configurations with titanium housings for deployment at greater depths.

Standard Measured Parameters

• 3D current velocity (East/North/Up, X/Y/Z or Beam 1/2/3)

• Acoustic signal strength (Beam 1/2/3)

• Compass

• Tilt

• Temperature

• Pressure

• Battery voltage

• Status code

• Error code

Surface wave monitoring

The standard Aquadopp is suitable for measuring surface wave height, period, and direction, which are calculated using the PUV method whereby spectra are estimated based on a combination of the pressure signal recorded by the instrument (P) and two horizontal components of the wave orbital velocity (U and V). More specifically, the pressure signal is used to provide an estimate of the wave frequency spectrum. The energy in this spectrum is then used to estimate wave height and period. The measurements of the wave orbital velocities are used to provide an estimate of the wave direction. Since these estimates are based on the distribution of wave energy and are not direct measurements of the free surface, they should be considered inferred estimates.

Both the dynamic pressure and the orbital velocities are driven by surface waves. The signals that are associated with these properties are complicated by the fact that they attenuate (that is the signals are weaker) with depth. The exact behaviour of the attenuation is determined by the water depth and the wavelength being observed. The greater the water depth the greater the attenuation; likewise, the shorter the wavelength (or higher the frequency of the wave) the greater the attenuation for a given water depth. This means that the estimation of wave parameters is limited by both water depth and wave frequency.

Specifications

Further details can be found in the manufacturer's specification sheets for the Aquadopp, Aquadopp 3000 and Aquadopp 6000.

BODC Processing

The data arrived at BODC in 60 Matlab files representing each Nortek sensor deployed during cruises D381A and D381B. No data file was received from the NE outer mooring serial number 1420, as this failed to log any data.

The data were reformatted to a BODC internal NetCDF format. The following table shows the mapping of variables within the Matlab file to appropriate BODC parameter codes:

Following reformatting, the data were screened using BODC in-house visualisation software, EDSERPLO.

Originator's Data Processing

Sampling strategy

A cluster of 9 moorings were deployed in the vicinity of the Porcupine Abyssal Plain Observatory. Each mooring contained between 5 and 13 Nortek Aquadopp single-point current meters.

Data Processing

The originator carried out the following processing:

• Data were converted from .aqd files to Matlab files using Nortek "bin2mat" software
• One Matlab file was created per mooring.
• The positions of the deployments were taken from the cruise report and added to the Matlab files.
• The files were truncated to cut off the deployment and recovery times of the mooring. These were identified by changes in the pressure channel.

The originator also created raw and gridded versions of the files, which are available on request.

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

Data Activity

OSMOSIS centre mooring

The short term moorings were deployed and recovered during cruise RRS Discovery D381A as part of the Ocean Surface Mixing, Ocean Submesoscale Interaction Study (OSMOSIS) project.

The target for the centre mooring was 48° 41.340' N, 16° 11.400' W in approximately 4,830 m of water. The mooring consisted of 48 Star-Oddi thermistors, one upward pointing 75 kHz ADCP, four 600 kHz ADCPs, thirteen Nortek single-point current meters and thirteen SBE 37 MicroCAT sensors. In addition, a light and Argo tag were fixed at the top of the mooring.

Instruments deployed on the mooring

Related Data Activity activities are detailed in Appendix 1

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:

Appendix 1: OSMOSIS central

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.