Metadata Report for BODC Series Reference Number 942645

• 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.

CH115_a Sea surface navigation instrument details

Navigation was conducted using a Global Positioning System and ship-mounted single-beam echo sounder. Instrument details are given in the table below.

CH115_a Sea surface Hydrography, Meteorology and Navigation Series

Instrumentation

Seawater was continuously pumped from the hull of the ship (at a depth of about 4m). This is known as the ship's non-toxic supply. The thermosalinograph was fed through a small (100-litre) header tank. A large plastic tank on the starboard deck was fed directly from the non-toxic manifold and contained the transmissometer and fluorometer. Baffles in the tank ensured that a continuous flow was maintained over the instruments. The nutrient autoanalyser was fed from plastic tubing connected to taps on the non-toxic supply.

Calibration samples were either taken from the non-toxic tap on the wet laboratory sink or the thermosalinograph outlet. A separate clean system was fitted to supply seawater to the trace metal analysis system. A specially adapted PES fish was deployed on the port side just aft of the bow at a depth of between 1m and 3m. A plastic hose led from this directly to the analytical equipment. Water was driven through the system by a large perisaltic pump.

Data Acquisition

For most parameters, data logging and initial processing was handled by the RVS ABC system. The Level A sampling microcomputer digitised an input voltage, applied a time stamp and transferred the data via the Level B disk buffer onto the Level C where the data records were assembled into files. The exception to this was the trace metal analyser that was logged by a PC. Care was taken to ensure that the PC clock was synchronised with the master clock used for the Level A time stamps.

Sampling rates varied from 10 seconds to several minutes. The Level C included a suite of calibration software, which was used to apply initial calibrations to convert raw ADC counts into engineering units. At the end of the cruise, the Level C disk base was transferred to BODC for further processing.

BODC Data Processing Procedures

Data from the underway files were merged into a common file (the binary merge file) with a sampling interval of 30 seconds using time as the primary linking key. Data sampled at higher frequencies were reduced by averaging. Data logged as voltages (e.g. PAR, nutrients) were converted to engineering units.

Each data channel was inspected on a graphics workstation and any spikes or periods of dubious data were flagged. The power of the workstation software was used to undertake all possible comparative screening checks between channels.

CH115_a Underway Navigation Series

Navigation Processing Notes

Positional Data

GPS was the primary navigation system used on this cruise. When no GPS fixes were available, the ship's position was determined by dead reckoning based upon the ship's gyro and EM log. Once a fix was obtained after a period of dead reckoning, the surface drift velocity was computed. If this exceeded 4 knots the data were automatically flagged suspect. The positional error due to surface drift was then retrospectively applied over the period of dead reckoning.

At BODC a program was run which located any null values in the latitude and longitude channels and checked to ensure that the ship's speed did not exceed 15 knots. The bridge logs were used to manually enter as many positions as possible during periods when navigation wasn't automatically logged. These cover critical points such as course alterations and arrival/departure at stations. Any remaining null values were filled by linear interpolation. The maximum gap interpolated for this cruise was 1 minute.

Bathymetry

Bathymetric depth was logged by the ABC system from an EA500 dual channel echo sounder, which recorded the depth of water under the keel (i.e. depth less 4 metres). A correction was applied at BODC to convert this to the true water depth.

Project Information

LOIS River-Atmosphere-Coast Study (LOIS - RACS)

Introduction

The Land-Ocean Interaction Study (LOIS) was a NERC research programme designed to study processes in the coastal zone. The Rivers, Atmosphere and Coasts Study (RACS) was a major component of LOIS that looked at land-sea interactions in the coastal zone and the major exchanges (physical, chemical and biological) between rivers and estuaries and the atmosphere. The study focused on the east coast of the UK from the Wash to the Tweed.

RACS included several sub-components

• BIOTA - A study of salt marshes of the Humber and Wash
• RACS (A) - An atmospheric chemistry study looking at air mass changes from the Wash into East Anglia
• RACS (C) - A study of the estuaries, coasts and coastal waters between Great Yarmouth and Berwick upon Tweed.
  1. The coastal oceangraphic survey
  2. The Humber estuarine study
  3. The Tweed estuarine study
  4. The Holderness experiment
• RACS (R) - A study of rivers that drain into the North Sea

RACS (A) was coordinated by the University of East Anglia and RACS (C) by the Plymouth Marine Laboratory.

RACS (A)

The bulk of the RACS (A) data set was collected during two field campaigns in the winter (October/November) of 1994 and the summer (May/June) of 1995. During these campaigns data were collected continuously from the University of East Anglia Atmospheric Observatory at Weybourne on the north Norfolk coast. An instrumented vessel was stationed offshore to provide a second sampling site to allow changes in a given air mass to be monitored. The Imperial College Jetstream research aircraft made one flight during each campaign to provide a link between the two surface stations. The Jetstream made four additional flights in 1996 and 1997.

RACS (C)

The coastal oceanographic survey

The coastal oceanographic data set was collected during a series of 17 RRS Challenger cruise legs. Most cruises covered two survey grids. One from Great Yarmouth to the Humber designed around the distribution of the sandbanks and a second simple zig-zag grid from the Humber to Berwick on Tweed. A large number of anchor stations, usually over one or two tidal cycles, were worked in the area of the Humber mouth or the Holderness coast.

The Humber estuarine study

The Humber estuarine data set was collected during a series of 33 campaigns on the Environment Agency vessels Sea Vigil and Water Guardian in the Humber, Trent and Ouse river systems at approximately monthly intervals between June 1993 and December 1996. Each campaign consisted of two or three one-day cruises. The tracks covered the estuary from the tidal limits of both Trent and Ouse to Spurn Point. Instrumental and sample data are available from a series of fixed stations that were sampled during every campaign.

The Tweed estuarine study

The Tweed estuarine data set was collected during a series of 13 campaigns using RV Tamaris in association with a rigid inflatable vessel at approximately monthly intervals between July 1996 and July 1997. Each campaign covered the tidal reaches of the River Tweed.

The Holderness experiment

The Holderness Experiment was designed to monitor the process of sediment transport along the Holderness coastline. It consisted of three moored instrument deployments during the winters of 1993-1994, 1994-1995 and 1995-1996. Mooring platforms were deployed at eight stations along two lines off the Holderness coast. A northerly and a southerly line of four stations each were used (N1 - N4 and S1 to S4) with the lowest numbers being inshore. Both lines were approximately perpendicular to the coast, although the S4 station lay to the south of the S line, off Spurn Head.

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: