Metadata Report for BODC Series Reference Number 648232


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 D14244
BODC Series Reference 648232
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2001-11-22 12:30
End Time (yyyy-mm-dd hh:mm) 2001-11-22 14:39
Nominal Cycle Interval -
 

Spatial Co-ordinates

Start Latitude 61.04020 N ( 61° 2.4' N )
End Latitude 61.04250 N ( 61° 2.5' N )
Start Longitude 37.04980 W ( 37° 3.0' W )
End Longitude 37.04580 W ( 37° 2.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 9.95 m
Maximum Sensor Depth 2881.87 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
ACBSA150 2 Decibels Sv_150kHz Acoustic backscatter (absolute) in the water body by 150kHz 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 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:

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:

Frequency of instrument (kHz) 150
Number of bins: 10
Beam angle 20.0
Number of pings per ensemble 1
Bin length (cm) 1600
Blank before transmit (cm) 1600

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

Coefficient  
Alpha 0.044
C -153.3
PdbW 24
Rayliegh distance 1.88

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.

Station No. Status Comments
14191 Processed  
14199 Processed  
14200 Processed  
14205 Processed  
14206 Processed  
14211 Processed  
14212 Processed  
14213 Processed  
14214 Processed  
14215 Processed  
14223 Processed  
14231 Processed  
14239 Processed  
14244 Processed  
14245 Processed Suspect profile
14249 Processed  
14254 Processed Suspect profile
14259 Processed  
14263 Processed  
14267 Processed  
14275 Processed  
14283 Processed  
14287 Failed  
14288 Processed  
14289 Processed  
14294 Processed  
14295 Processed  

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.

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 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:

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 D258
Departure Date 2001-11-01
Arrival Date 2001-12-18
Principal Scientist(s)Raymond T Pollard (Southampton Oceanography Centre), Steven J Hay (Fisheries Research Services Aberdeen 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