Metadata Report for BODC Series Reference Number 1921085

• 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

Shipboard ADCP data from cruise JC159 Quality Report

Screening and Quality Control

The result of manual removal of bad data by the originator are gaps in the eastward and northward velocity data and current speed data at the following times (to the nearest 5 minutes):

For the 75kHz ADCP:

• 09 Mar 2018 15:25 hours and 19:20 hours
• 19 Mar 2018 23:10 hours and 23:20 hours
• 21 Mar 2018 23:35 hours and 23:45 hours
• 28 Mar 2018 13:55 hours and 14:15 hours, 20:30 hours and 220:50 hours
• 31 Mar 2018 17:20 hours and 17:35 hours
• 02 Apr 2018 00:05 hours and 00:15 hours

For the 150kHz ADCP:

• 19 Mar 2018 23:15 hours and 23:25 hours
• 25 Mar 2018 01:12 hours and 01:22 hours
• 31 Mar 2018 17:20 hours and 17:30 hours
• 02 Apr 2018 16:10 hours and 16:20 hours, 22:20 hours and 22:40 hours
• 03 Apr 2018 00:30 hours and 00:55 hours, 05:40 hours and 14:40 hours

The originator's text below explains the existence of gaps in the data.

All data sequences were visually inspected by the originator and 'bad' bins and profiles were removed. This was carried out with 'gautoedit.py' which is a GUI for manual editing of data. It allows the display of sections of different velocity components and navigation, and different options to select and remove spurious data. Different quality standards can be applied to automatically remove low quality data. For this cruise, the standard criteria given by Gautoedit were used. Then, after visual inspection, the manual removal of bad bins was done by drawing a box around them with the cursor, or by selecting complete profiles to be removed.

The quality of the data was good through most of the cruise and little manual editing was required. Most of the bad bins were found near the bottom in the shelves, where the instruments reached the seafloor. The reflection of the acoustic signal from the seafloor was generally identified and removed, but sometimes it introduces a bias at the bottom layer, especially in the slopes when the depth approaches the limit of the instrument's skill to detect the bottom. The spurious data are identified as a few of the bottom bins (3 to 6 bins) showing an abnormal high velocity, sometimes with a direction incoherent with the rest of the profile.

When the ship changed its heading and speed sharply, when approaching or leaving some stations, it would also produce some bad data. This was identified as a sequence of 1 to 3 profiles with strong velocities throughout the full water column. The sharp changes could not be adequately removed by the instrument and resulted in anomalous data. Note that this effect is different to a transducer misalignment. These bad profiles irrupted occasionally between coherent velocity sections, regardless of whether it changed from transit to on-station. The misalignment effect shows consistently, as a strong velocity contrast between sections of different ship speed and are fixed separately with an angle correction.

Finally, further editing was applied to single anomalous pings. Especially in the last transect, from Walvis Bay to Cape Town. Rougher weather conditions were encountered and the effect of bubbles could be clearly seen as abnormal strong velocity bins towards the surface layers. These were also removed. It is interesting to note that this transect was carried out with the drop keel up, being more susceptible to surface interferences.

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

ORCHESTRA cruise JC159 Shipboard ADCP Originator data processing

The following was taken from the JC159 cruise report. Data were collected using a Teledyne RDI Ocean Surveyor 75kHz ship-mounted ADCP and Teledyne RDI Ocean Surveyor 150kHz vessel-mounted ADCP.

Configuration and acquisition

VMADCP (Vessel Mounted Acoustic Doppler Current Profiler) transducers (75Hz and 150Hz) were mounted on port-side drop keel and were setup using the following configuration:

BBTalk software version 3.09 was used to communicate with and test the instruments. The file 'testOS.rds', provided by Teledyne was used to test the instruments; The instrument checks were positive and also provided useful metadata, such as the beam angle of the transducers (30 degrees) and the receive bandwidth of each beam (showing all beams worked correctly).

Data were acquired using the RD Instruments VmDas software package version 1.48. VmDas collects and stores real-time single ping data, and averages profiles in short and long term averages. The averaging periods are defined in the configuration and are useful for data pre-visualisation in VmDas or WinRiver. However, the final data averaging is carried out from single-ping data and the averaging period can be changed or set later. A standard averaging period and the one we used later in the processing was 5 minutes (300 seconds).

Processing

Data were processed in the python UH CODAS (Common Ocean Data Access System) suite v32 (2017-09-20) and read into mexec NetCDF.

Long-Term Average processing (LTA):

Long-term averaged data allows little room for post-processing, as single-ping profiles are averaged before any changes are applied. However, it provides a useful tool to quickly visualise the first sequences of data, to spot any possible issues and to primarily assess the misalignment of the transducer from the ship's axis.

A processing directory was generated using the adcp_tree.py command. This command creates a subset of folders designed to contain all the processed data and information. It is run in the form: <adcp_tree.py os150nb --datatype lta --cruisename os150_lta_017> Inside the new folder (os150nb in this example) a control file was written and named 'q_py.cnt', which contains the information to start the processing. This file contained the following information:

• yearbase 2018
• cruisename os150_lta_017
• dbname a15017
• datatype lta
• sonar os150nb
• ens_len 300 (this will be our LTA time average)

The basic CODAS processing can then be run using the quick_adcp.py command. This is done with the command file as:
<quick_adcp.py --cntfile q_py.cnt --auto>
The 'auto' option runs all the steps automatically and it was the preferred choice during the cruise.

Navigation was ploted to help determine that the NMEA data were being read and processed adequately. This was done by running the command <plot_nav.py nav/a15017.gps>. The name of the navigation file (in the 'nav' folder) contains the database name (in this example it is a15017) with the extension 'gps'. This will plot the trajectory of the ship during the ADCP sequence and it will also plot latitude and longitude as a function of time.

To visualise the actual data, the command <dataviewer.py> provided the best tool to plot velocity data. This script opened a GUI that allows the selection of variables (different velocity components and data quality metrics) together with information about the navigation (speed and heading). These preliminary plots were used to ensure data were being recorded adequately and to find out how deep the instruments could measure. They also informed about misalignment of the transducers, as changes in ship speed or heading result in sharp changes in the velocity sections when the instrument is not correctly aligned. It was also a useful tool to identify sources of bad data (such as bottom reflection, possible acoustic interferences, low scatter layers, interference of bubbles at the surface, etc.). It was found that data were generally good quality, even as long-term averaged profiles. They required some post-processing at the single-ping level but with little manual editing. The need to correct the transducers' angles was also identified.

ENR Processing:

ENR files are binary and contain the raw single ping data. The best quality of data is achieved when the processing is done at single-ping data, before these are averaged into consistent profiles. This allows the removal of bad data and misalignment errors at individual pings. VmDas records these data in the files with the ENR extension. However, the CODAS processing software does not support the direct processing of this data type. The data need to be converted into the UHDAS format. This section explains how ENR data are converted to UHDAS and how those are processed:
Within the 'config' folder in the enr processing folder the command <reform_vmdas.py ../../..> was run, whcih prompts a GUI that allows the selection of the VmDas data folder and the 'fake_uhdas_data' which is where the converted data will be saved. The path given after 'reform_vmdas.py' was the starting directory from where to browse the VmDas and UHDAS data. After running the GUI, a file is generated with the variable names to use later (reform_defs.py) and a program to be run next (vmdas2uhdas.py). The command <python vmdas2uhdas.py> was run to convert the data into UHDAS. It first recast the NMEA data within the VmDas data folder and then it converted the data to UHDAS, inside the 'fake_uhdas_data' folder.

A UHDAS configuration file was also required before running the actual processing. This file was generated with another GUI by running the command <proc_starter.py reform_defs.py>. This GUI required some information about the ADCP instruments, such as the beam angle, the transducer depth and its angle correction (if any is required or known). In this cruise, the angle correction was set to 0 for the os150. An initial correction of 8.5° was applied to the os75 (known from previous cruise reports), this allowed the data to be processed further before determining a more accurate correction.

With the new configuration file processing was continued in a similar way to the LTA data. First, an adcp_tree.py folder was created (this time for UHDAS data). A similar q_py.cnt control file was written for UHDAS data, with the addition of the following lines:

• update_gbin
• configtype python
• max_search_depth 1500 (maximum depth where the bottom is searched)

Finally, the quick_adcp.py command was run to carry out the main processing steps.

Calibration

The SADCP operated continuously in narrowband mode. Calibrations were obtained from the bottom track mode. For the os75 instrument the angle misalignment, calculated as the average of the medians of each sequence, weighted by the number of points is of -0.0144° (relative to the initially accounted deviation of 8.5°, applied during processing). This means that, with the drop-keel down, the misalignment of the os75 transducer is of 8.5 degrees (as initially applied). This was the angle correction applied to all the processed sequences for this instrument. For the os150 instrument the median misalignment was of -0.3317°. No previous correction had been applied. Considering this result, a correction of -0.3 was applied to the os150 instrument. The keel was brought up shortly after station 123 until the end of the cruise, it was determined that the angle of misalignment did not change significantly as a result of the position of the keel.

Processing by BODC of RRS James Cook JC159 Ship Mounted ADCP data

The data arrived at BODC in two .nc (MStar) files containing data collected from the 75kHz and 150kHz ship mounted ADCPs during cruise JC159. The data were reformatted to BODC's internal NetCDF format. The following table shows the mapping of variables within the MStar files to 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 Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA)

The Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) is a £8.4 million, five year (2016-2021) research programme funded by the Natural Environment Research Council (NERC). The aim of the research is to to advance the understanding of, and capability to predict, the Southern Ocean's impact on climate change via its uptake and storage of heat and carbon. The programme will significantly reduce uncertainties concerning how this uptake and storage by the ocean influences global climate, by conducting a series of unique fieldwork campaigns and innovative model developments.

Background

ORCHESTRA represents the first fully-unified activity by NERC institutes to address these challenges, and will draw in national and international partners to provide community coherence, and to build a legacy in knowledge and capability that will transcend the timescale of the programme itself.

It brings together science teams from six UK research institutions to investigate the role that the Southern Ocean plays in our changing climate and atmospheric carbon draw-down. It is led by British Antarctic Survey, in partnership with National Oceanography Centre, British Geological Survey, Plymouth Marine Laboratory, the Centre for Polar Observation and Modelling and the Sea Mammal Research Unit.

The oceans around Antarctica play a critical a key role in drawing down and storing large amounts of carbon and vast quantities of heat from from the atmosphere. Due to its remoteness and harsh environment, the Southern Ocean is the world's biggest data desert, and one of the hardest places to get right in climate models. The ORCHESTRA programme will make unique and important new measurements in the Southern Ocean using a range of techniques, including use of the world-class UK research vessel fleet, and deployments of innovative underwater robots. The new understanding obtained will guide key improvements to the current generation of computer models, and will enhance greatly our ability to predict climate into the future.

The scope of the programme includes interaction of the Southern Ocean with the atmosphere, exchange between the upper ocean mixed layer and the interior and exchange between the Southern Ocean and the global ocean.

Further details are available on the ORCHESTRA page.

Participants

Six different organisations are directly involved in research for ORCHESTRA. These institutions are:

• British Antarctic Survey (BAS)
• National Oceanography Centre (NOC)
• Plymouth Marine Laboratory (PML)
• British Geological Survey (BGS)
• Centre for Polar Observation and Modelling (CPOM)
• Sea Mammal Research Unit (SMRU)

GO-SHIP are a third party organisation that, although not directly involved with the programme, will conduct ship based observations that will also be used by ORCHESTRA.

Research details

Three Work Packages have been funded by the ORCHESTRA programme. These are described in brief below:

• Work Package 1: Interaction of the Southern ocean with the atmosphere
  WP1 will use new observations of surface fluxes and their controlling parameters in order to better constrain the exchanges of heat and carbon loss across the surface of the Southern Ocean.

• Work Package 2: Exchange between the upper ocean mixed layer and the interior.
  This work package will combine observationally-derived data and model simulations to determine and understand the exchanges between the ocean mixed layer and its interior.

• Work Package 3: Exchange between the Southern Ocean and the global ocean .
  This WP will use budget analyses of the hydrographic/tracer sections to diagnose the three-dimensional velocity field of the waters entering, leaving and recirculating within the Southern Atlantic sector of the Southern ocean.

• Fieldwork and data collection

  The campaign consists of 12 core cruises on board the NERC research vessels RRS James Clark Ross and RRS James Cook and will include hydrographic/tracer sections conducted across Drake Passage (SR1b), the northern Weddell Sea/Scotia Sea (A23), the northern rim of the Weddell Gyre (ANDREXII) and across the South Atlantic (24S). Section I6S will be performed by GO-SHIP Project Partners. Measurements will include temperature, salinity, dissolved oxygen, velocity, dissolved inorganic carbon, total alkalinity, inorganic nutrients, oxygen and carbon isotopes, and underway meteorological and surface ocean observations including pCO₂.

  Tags will be deployed on 30 Weddel seals and these will provide temperature and salinity profiles that can be used alongside the Argo data.

  Autonomous underwater ocean gliders will conduct multi-month missions and will deliver data on ocean stratification, heat content, mixed layer depth and turbulent mixing over the upper 1 km, with previously-unobtainable temporal resolution. These gliders will be deployed in the Weddell Gyre and the ACC.

  Field campaigns with the MASIN meteorological aircrafts will be conducted flying out of Rothera and Halley research stations and the Falkland Islands. These campaigns will deliver information on key variables relating to air-sea fluxes (surface and air temperature, wind, humidity, atmospheric CO₂, radiation, turbulent fluxes of heat, momentum and CO₂), in different sea ice conditions and oceanic regimes.

  Eart Observation datasets will be used to inform the programme on the properties of the ocean, sea ice and atmosphere and on interactions between them.

  A cluster of 6 deep ocean moorings in the Orkney Passage will collect year round series of AABW temperatre and transport. This work connects to the NERC funded project Dynamics of the Orkney Passage Outflow (DYNOPO).

  The UK Earth System model (UKESM) and underlying physical model will be used to conduct analyses of heat and carbon uptake and transport by the Southern Ocean and their links to wider climate on decadal timescales.

  An eddy-resolving (1/12°) sector model of the ocean south of 30°S with 75 vertical levels, will be built using the NEMO model coupled to the Los Alamos sea ice (CICE) model. The improvements on the ocean boundary layer will be based from the results from the NERC-funded OSMOSIS project and the inclusion of tides.

  20-5 year runs of an adjoint model will be conducted to determine how key forcings and model states affect the uptake and subduction of heat and carbon by the ocean.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

WHP One Time Survey Section A095

This section is a complete full depth, hydrographic section from continent-to-continent from South America to Africa. The section is repeated to the highest international standards (World Ocean Circulation Experiment - WOCE), therefore, a full suite of physical, chemical and tracer measurements are made. It was occupied for the first time in 1983 as it was believed that flux calculations (heat, freshwater, tracers) could be performed better than at 30° S (WOCE A10), however transient tracers were not measured at this time and the cruise did not contribute to WOCE or CLIVAR.

The image below shows the location of this section in relation to both continents.

History of Occupations

Related Fixed Station activities are detailed in Appendix 1

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: WHP One Time Survey Section A095

Related series for this Fixed Station 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.