Metadata Report for BODC Series Reference Number 648220

• 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

RRS Discovery 253 Lowered ADCP (LADCP)

Introduction

The two Lowered Acoustic Doppler Current Profilers (LADCP) used on the FISHES cruise were RDI 150kHz BroadBand ADCP's (phase III) with 25 degree and 30 degree beam angles. They were mounted vertically within the CTD frames with the bottom of the transducers protected by the base of the CTD frame.

The 20 degree instrument was installed on the frame with the Neil Brown Mk III CTD at the beginning of the cruise. The 30 degree instrument was mounted on the frame with the Sea-Bird 9/11 plus CTD.

A few minutes before each cast, a command file was downloaded to the LADCP unit from a PC in the deck lab via a serial link. On this cruise the same command file was used for the whole cruise (an annotated listing is given in an Appendix at the end of this section).

Bottom tracking was used throughout. This reduced the number of water track pings but was justified because it allowed a second independent estimate of the bottom current to be made. At regular intervals the instrument emitted a bottom ping to test for range. Once the bottom was found the instrument recorded the velocity of the ground with respect to the package. It was hoped to use this to provide a check of the quality of the absolute velocity data calculated by the more round about route described below.

The data were recorded internally and downloaded at the end of each cast by connecting a data link to the package from the PC. RDI utilities BBTALK and BBSC were used to interrogate the profiler and to download data to the PC. Power was supplied to the profiler via the serial cable in order to conserve the battery pack.

Processing

Data were transferred to the UNIX workstations via FTP and then processed using a combination of PERL scripts and MATLAB m-files developed by Eric Firing at the University of Hawaii.

Processing was done in a number of steps which are briefly described below.

1. The binary data were first scanned to find useful information from the cast such as time at the surface, time at the bottom and the number of ensembles.
2. The data were then read into a CODAS database. Magnetic variation and position were added to the database at this stage.
3. When CTD data were available the pressure temperature and salinity data were added to the database in order to correct for the variation of sound speed with depth.
4. Absolute velocities were then found by calculating horizontal velocity shear to eliminate package motion, integrating with time to calculate the barotropic terms and then merging with navigation data to remove the motion of the ship.

Bottom velocity data were not included in the processing path and had to be extracted manually from the binary file on the PC and processed separately from the water track data.To aid processing a number of master scripts were written. These were:

• dowater - performed all water data steps, from reading in the data from the RDI binary file to calculation of absolute velocity; all intermediate files in the calculation being replaced or edited for each cast so that no old information was mistakenly used.
• dobottom - calculated near bottom water velocities by using bottom track data;
• donav - created file of GPS data which had been edited for bad fixes by screening the resulting speed over ground velocities;
• docomp - created a file merging LADCP data with on station averaged 150 kHz VM-ADCP data
• dopict, dodisp - two scripts which created summary plots of LADCP and ADCP data for all stations.

RRS Discovery 258 150 kHz lowered ADCP (LADCP)- Absolute backscatter

Deployment and originators processing

The 150 kHz LADCP was configured as for previous cruises and processed in exactly the same way using Eric Firings software. See for example, Allen JT et al, 2001; SOC Cruise Report 37, Discovery 253 (FISHES). Some details of the setup are included in the following table:

Absolute backscatter coefficient was calculated by the method of Deines (1990). The coefficients used are listed in the table below.

Occasionally there were problems with time stamps. The profiles marked suspect in the table below are where there was disagreement between the ADCP depth and CTD depth.

BODC processing

A total of 26 station files where submitted to BODC. The Data were supplied in Matlab binary format. The following variables were transferred to BODC QXF format. A large number of additional variables, including CTD and navigation data, were also present in the files. These were not transferred.

Screening and Data quality

The data have been visually screened for obvious problems using the BODC XERPLO software. No spikes were evident but discontinuities were observed in two series (14254 and 14288). These were present in the originators files.

References

RDI, (1990). Calculating Absolute Backscatter. Technical bulletin ADCP-90-04, R D Instruments, San Diego, CA, USA.

Project Information

Marine Productivity programme (MarProd)

The Marine Productivity programme (MarProd) was a Thematic Programme of the Natural Environment Research Council. It was funded for a period of five years starting in 2000. Its main goal was "to develop coupled modelling and observation systems for the pelagic ecosystem, with emphasis on physical factors affecting zooplankton dynamics" with the following specific objectives:

• To identify the dominant spatial and temporal scales of physical parameters and zooplankton population dynamics, by observation, modelling and retrospective analysis

• To parameterise the critical processes governing zooplankton dynamics by observations and experiments

• To construct and validate spatially explicit models of zooplankton and their food and predators, capable of resolving short term changes in population structure

• To provide data for model validation by developing and applying new interdisciplinary techniques to a wide spectrum of biological and physical parameters

• To develop a database and information system for historic and new data and models.

The programme was composed of two phases: Phase 1 projects (2000-2002) focused on the use of historical datasets and existing biological models, complemented by laboratory experiments and remote-sensing analyses to gain a better understanding of the dynamics of zooplankton populations in shelf seas. The main, field-based Phase 2 of the programme (2001-2005) focused on the open ocean. The fieldwork phase took place between November 2001 and December 2002 and consisted of four surveys in the northern North Atlantic in early winter 2001 and 2002, and in spring and summer 2002.

MarProd was a major UK contribution to the international Global Ocean Ecosystem Dynamics project (GLOBEC).

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: