Metadata Report for BODC Series Reference Number 663498


Metadata Summary

Data Description

Data Category Currents -subsurface Eulerian
Instrument Type Acoustic doppler current profiler
Instrument Mounting lowered unmanned submersible
Originating Country United Kingdom
Originator -
Originating Organization Southampton Oceanography Centre (now National Oceanography Centre, Southampton)
Processing Status QC in progress
Project(s) Marine Productivity
 

Data Identifiers

Originator's Identifier W14729
BODC Series Reference 663498
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2002-08-01 04:18
End Time (yyyy-mm-dd hh:mm) 2002-08-01 05:50
Nominal Cycle Interval 1.04 seconds
 

Spatial Co-ordinates

Latitude 62.35503 N ( 62° 21.3' N )
Longitude 28.53470 W ( 28° 32.1' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 10.15 m
Maximum Sensor Depth 1697.83 m
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum -
 

Parameters

BODC CODE Rank Units Short Title Title
DISTTRAN 0 Metres Tran_dist Distance (from transducer along measurement axis)
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
ACYCAA01 1 Dimensionless Record_No Sequence number
PRESPR01 1 Decibars Pres_Z Pressure (spatial co-ordinate) exerted by the water body by profiling pressure sensor and corrected to read zero at sea level
ACBSA300 2 Decibels Sv_300kHz Acoustic backscatter (absolute) in the water body by 300kHz broadband acoustic doppler current profiler (ADCP) and calibration using protocols of Deines (1999)
 

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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 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:

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 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