Metadata Report for BODC Series Reference Number 663554
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
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Time Co-ordinates(UT) |
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Parameters |
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Problem Reports
No Problem Report Found in the Database
Data Access Policy
Open Data
These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.
If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:
"Contains public sector information licensed under the Open Government Licence v1.0."
Narrative Documents
RRS Discovery 264 300kHz Lowered ADCP (LADCP)- Absolute backscatter
Deployment and originators processing
The instrument setup was consistent throughout the cruise and the details are listed in the following table.
Frequency of instrument (kHz) | 300 |
Number of bins: | 16 |
Beam angle | 20.0 |
Number of pings per ensemble | 1 |
Bin length (cm) | 1000 |
Blank before transmit (cm) | 500 |
Absolute backscatter coefficient was calculated by the method of Deines (1990). The coefficients used are listed in the table below.
Coefficient | |
---|---|
Alpha | 0.069 |
C | -148.2 |
PdbW | 15.4 |
Rayliegh distance | 2.64 |
The LADCP deployments are listed in the following table with data originators comments
Station No. | Status | Comments |
---|---|---|
14697 | Processed | |
14703 | Processed | |
14712 | Processed | |
14717 | Processed | |
14726 | Processed | |
14729 | Processed | |
14723 | Processed | |
14744 | Processed | |
14763 | Processed | |
14772 | Processed | |
14777 | Processed | |
14788 | Processed | |
14791 | Processed | |
14794 | Processed | |
14804 | Processed | |
14810 | Processed | |
14819 | Processed | |
14825 | Processed | |
14834 | Processed | |
14849 | Processed | |
14856 | Processed | |
14861 | Processed | |
14879 | Processed | |
14881 | Processed | |
14894 | Processed | |
14896 | Processed | |
14899 | Processed | |
14902 | Processed | |
14912 | Processed | |
14917 | Processed | |
14927 | Processed | |
14933 | Processed | |
14944 | Processed | |
14964 | Processed | |
14976 | Processed | |
14983 | Processed | |
14988 | Processed | |
14997 | Processed | Harmonic interference? |
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.
Description | Units | Originators variable |
---|---|---|
Pressure | Decibars | d.z |
Absolute backscatter (MVBS) | Decibels | d.mvbs |
Distance from transducer | Metres | d.zd |
Screening and Data quality
The data have been visually screened for obvious problems using the BODC EDSERPLO software. No significant problems were detected. In all casts the quality of the data deteriorates with distance from the transducer, characterised by regular spikes in the time series of each bin. The cause for these was unknown and consequently no attempt has been made to flag potentially suspect values.
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:
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To identify the dominant spatial and temporal scales of physical parameters and zooplankton population dynamics, by observation, modelling and retrospective analysis
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To parameterise the critical processes governing zooplankton dynamics by observations and experiments
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To construct and validate spatially explicit models of zooplankton and their food and predators, capable of resolving short term changes in population structure
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To provide data for model validation by developing and applying new interdisciplinary techniques to a wide spectrum of biological and physical parameters
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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
Cruise Name | D264 |
Departure Date | 2002-07-25 |
Arrival Date | 2002-08-28 |
Principal Scientist(s) | Andrew S Brierley (Gatty Marine Laboratory) |
Ship | RRS Discovery |
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:
Flag | Description |
---|---|
Blank | Unqualified |
< | Below detection limit |
> | In excess of quoted value |
A | Taxonomic flag for affinis (aff.) |
B | Beginning of CTD Down/Up Cast |
C | Taxonomic flag for confer (cf.) |
D | Thermometric depth |
E | End of CTD Down/Up Cast |
G | Non-taxonomic biological characteristic uncertainty |
H | Extrapolated value |
I | Taxonomic flag for single species (sp.) |
K | Improbable value - unknown quality control source |
L | Improbable value - originator's quality control |
M | Improbable value - BODC quality control |
N | Null value |
O | Improbable value - user quality control |
P | Trace/calm |
Q | Indeterminate |
R | Replacement value |
S | Estimated value |
T | Interpolated value |
U | Uncalibrated |
W | Control value |
X | Excessive difference |
SeaDataNet Quality Control Flags
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
Flag | Description |
---|---|
0 | no quality control |
1 | good value |
2 | probably good value |
3 | probably bad value |
4 | bad value |
5 | changed value |
6 | value below detection |
7 | value in excess |
8 | interpolated value |
9 | missing value |
A | value phenomenon uncertain |
B | nominal value |
Q | value below limit of quantification |