Metadata Report for BODC Series Reference Number 2102304

• 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

Kongsberg Simrad EA500 bathymetric echosounder

The EA500 is a bathymetric echosounder that can be used in water as deep as 10,000 m. It features triple frequency operation with a separate digitiser for each channel and high transmitted power with an instantaneous dynamic range of 160 dB. The instrument can operate with several pulses in the water simultaneously and has bottom tracking capabilities. A wide range of transducers (single beam, split beam or side-looking) is available and the ping rate is adjustable up to 10 pings per second. The split beam operation measures the athwartships inclination angle of the seabed.

This instrument was introduced in June 1989 and and replaced by the EA 600 in 2000.

Specifications

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

Ashtech G12 Global Positioning System Receiver

The Ashtech G12 Global Positioning System (GPS) uses all-in-view tracking and 12 channels to provide real time three-dimensional positional measurements. It is Differential GPS (DGPS) ready, offering an accuracy of better than 40 cm, position latency better than 50 ms, and exact position latency to millisecond accuracy.

Specifications

Further details can be found in the manufacturer's 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.

Chernikeeff Aquaprobe Mk5 Electromagnetic Speed Log

The Aquaprobe Mk5 EM Speed Log operates on the principle that a conductor (such as water) passing through an electromagnetic field will create a voltage whose magnitude increases as the speed of the conductor increases. The EM log includes one or two hull-mounted transducers, which generate an electromagnetic field and measure the voltage created by the flow of water through that field, thereby deducing the speed of the vessel through the water.

The EM log has the options of single or twin transducers, single or dual axis speed measurements and gate-valved (retractable) hull fitting or fixed transducers. The microprocessor calibration control ensures a high accuracy through the entire speed range.

Specifications

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

Trimble 4000DS Global Positioning System receiver

The Trimble 4000DS Differential Surveyor is similar to the 4000RS (a Maxwell-based receiver that is oriented toward precision positioning applications. It is intended for use as a DGPS base station, generating RTCM-104 corrections). The 4000Ds can apply RTCM-104 corrections to the satellite data it receives in order to generate accurate position fixes in real time.

UK SOLAS Cruise D313 Underway Navigation, Meteorology and Sea Surface Hydrography Processing Document

Cruise details

Content of data series

Instrumentation

Navigation and bathymetry

Meteorology

Surface hydrography

Data processing by originator

Raw data were logged to NetCDF format through the ship's Techsas system. Data were converted to RVS binary format on a daily basis, for manual data processing including merging the navigation streams, deriving absolute winds and salinity, and correcting bathymetric depth data. Data were supplied to BODC in RVS ASCII format.

Navigation and bathymetry

Several GPS systems where used on the ship. These are treated hierarchically, with two used as backups to the first. The standard processing software, BESTNAV, identifies gaps in the preferred GPS stream, then fills them with data from the second choice stream, and finally, if necessary, with data from the third choice stream.

Meteorology

Meteorology data were collected from sensors mounted at 18.5 m height on the foremast platform. The ship's heading and course over ground were used to correct relative wind data to absolute values.

Sea surface hydrography

The surface water component consisted of a flow through system with a pumped pickup at 5 m depth. The TSG flow was set to approximately 25 L/min, and the fluorometer and transmissometer to a flow rate of approximately 3 L/min. The TSG conductivity and housing temperature were used to derive salinity.

BODC Data Processing

The data was received by BODC in ASCII format and converted into a single file with common time channel. During transfer, data were time-averaged to a common time interval, with directional data being averaged over a unit circle. All parameters were visually screened, and spikes flagged as suspect. Screening took into account comparisons between different parameters, and the environmental context.

Navigation and bathymetry

Bestnav latitude and longitude had some gaps, including one significant loss, due to the power failure, 02:08-03:47 02/12/2006. Gaps in the navigation channels were filled by linear interpolation.

Meteorology

BODC applied manufacturers' calibrations to the pyranometers and PAR sensors. Port and starboard PAR were merged, taking the maximum measured value from the pair for each cycle, to eliminate the shading effect of the ship. Port and starboard TIR were treated in the same way.

Wind data were screened with reference to the ship's heading, to account for the sheltering effect of the ship. BODC recalculated absolute wind speed and direction, from relative wind parameters and the ship's speed and heading, taking into account the vane orientation (0° at the stern). Air temperature were also screened with reference to heading, to identify instances of stack pollution.

Sea surface hydrography

TSG salinity was calibrated against CTD salinity averaged over the surface 10 m of the water column. A calibration dataset of 7 data pairs was analysed. There was no significant trend in instrument response with salinity, and although there was a suggestion of a temporal drift, the calibration dataset was too small for confidence. BODC has applied a mean offset calibration:

PSALSG01 = PSALSU01 - 0.1784

Hull temperature was calibrated against CTD temperature averaged over the surface 10 m of the water column. A calibration dataset of 8 data pairs was analysed. There was no significant trend in the instrument response with either time or temperature. BODC has applied a mean offset calibration:

TEMPHG01 = TEMPHU01 - 0.0903

Quality control report

Navigation and bathymetry

The echo sounder data have not been corrected for density affects. Bathymetric depth was found to be generally very poor. The data were heavily flagged by the originator, and BODC added further quality control flags where the data were particularly noisy, and when they severely deviated from GEBCO atlas bathymetry.

The navigation data suffered an outage between 02:08-03:47 02/12/2006. According to the cruise report the ship was hove to, sheltering off Rhum, during this period. BODC has judged it safe to fill the missing position data by linear interpolation.

Meteorology

Atmospheric temperature was rather erratic, with many sudden drops followed by a slow recovery. Wind speed and direction were rather noisy at times. Spikes in wind data associated with ship manoeuvres have been flagged.

Sea surface hydrography

No independent chlorophyll measurements were made on the cruise for calibration of chlorophyll fluorescence data. The fluorometer channel has been left as raw instrument output voltage.

Project Information

UK SOLAS, Field Observations of Sea Spray, Gas Fluxes and Whitecaps (SEASAW)

This project was led by the University of Leeds, in association with the National Oceanography Centre, Southampton, and the University of the Highlands and Islands.

Sea spray aerosol particles, generated primarily by the action of the wind on the ocean surface, make a major contribution to the atmospheric aerosol over the global oceans. Their ability to participate in heterogeneous atmospheric chemical processes and especially their activity as cloud condensation nuclei make them very important in global climate processes. Similarly, the air-sea fluxes of trace gases, are influenced by wind speed and whitecap processes. The flux of carbon dioxide between atmosphere and ocean is a controlling factor on the concentration of CO2 in the atmosphere, but there are large uncertainties in the size of the flux as a function of wind speed; and the effects of factors such as wave breaking, surfacants, etc are almost entirely unknown.

SEASAW aimed to measure gas and particle fluxes across the air-sea interface by direct eddy-covariance methods and other techniques in order to determine their dependence on environmental factors.

Fieldwork comprised one dedicated open ocean research cruise: D317, and participation in another UK SOLAS cruise: D313. The observational data include:

• sea state, whitecapping and wave breaking
• bubble properties
• air-sea gas fluxes
• aerosol properties

More detailed information on this project may be found in the official cruise reports for D313 and D317.

NE/C001869/1

Project Page

Funding: UKRI Gateway to Research

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: