Metadata Report for BODC Series Reference Number 662410

• 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 264 600kHz Lowered ADCP (LADCP)- Absolute backscatter

Deployment and originators processing

The instrument setup was consistent throughout the deployment period and is listed in the following table.

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

The LADCP deployments are listed in the following table with data originators comments

BODC processing

A total of 37 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 EDSERPLO software. No significant problems were detected.

References

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

RRS Discovery 264 Lowered ADCP deployments

The following has been extracted from the cruise report.

Two Lowered Acoustic Doppler Current Profilers (LACDPs) were fitted to the CTD rosette frame on Discovery 264, RDI 300 kHz and RDI 600 kHz workhorse ADCPs. The 600 kHz had been used on the two previous MarProd cruises, Discovery 258 and 262, and was principally intended for mean volume backscatter (MVBS) studies, to establish whether MVBS at a suitable frequency can be calibrated and used as a proxy for Calanus and similar sized zooplankton. The 300 kHz was in use for the first time on a MarProd cruise, but had been trialed previously by Brian King on a JCR cruise.

The LADCPs were used on all full depth CTD casts. They were not switched on for the shallow "chlorophyll max" casts, whose primary purpose was to collect water for on-board experiments. The raw data files were FTP-transferred from the dedicated LADCP PC in the deck lab to the shipboard system and processed using the Visbeck 2002 software. Most attention was paid to establishing good bottom tracking, as all casts went to within 10m or less of the bottom. It was found that both instruments gave similar readings for near-bottom velocities, where the velocity (current) profiles are well constrained by the absolute reference of the velocity of the package relative to ground. Thus the 600 kHz can be used to give reasonable velocity profiles near bottom (within 60-80 m).

Once constrained by the bottom-tracking, the Visbeck inverse velocity profiles were clearly better than those derived from the shear method, or downcast only. When compared with the two vessel mounted (VM) ADCPs (which inter compared within 1-2 cm/s), the Visbeck solutions were usually a reasonably match to the VM profiles, with 49 out of 66 differences being less than 3 cm/s, and the worst offset being 9 cm/s. We favour the Visbeck technique for future use, but conclude that the inverse calculation should be constrained by matching to the VM profiles near surface.

Backscatter was logged from both LADCPs for all profiles using the software developed by Nick Crisp and Sophie Fielding on Discovery 262. Profiles plotted for 4 bins differed sufficiently that it was clear that range corrections were needed. It is suspected that the RDI software has already made some allowance for the attenuation coefficient alpha, because application of the correct alpha coefficient for the frequency did not collapse the profiles on top of each other. Because information from RDI is awaited, the profiles were not analyzed further at sea. It was also noted that there were spikes to high MVBS at quasi-regular intervals. The cause of these has not been sought.

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: