Metadata Report for BODC Series Reference Number 91801


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Bissett-Bermann 9006 STD system  CTD; water temperature sensor; salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Scottish Marine Biological Association (now Scottish Association for Marine Science)
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier C876/063
BODC Series Reference 91801
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1976-05-29 03:45
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 56.83330 N ( 56° 50.0' N )
Longitude 6.08330 W ( 6° 5.0' W )
Positional Uncertainty Unspecified
Minimum Sensor Depth 4.86 m
Maximum Sensor Depth 102.72 m
Minimum Sensor Height 7.28 m
Maximum Sensor Height 105.14 m
Sea Floor Depth 110.0 m
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 Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODE Rank Units Short Title Title
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
SSALPR01 1 Parts per thousand UspSal Salinity of the water body by conductivity cell
TEMPST01 1 Degrees Celsius WC_temp_CTD Temperature of the water body by CTD or STD
 

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

Inspection of the pressure records from this cruise revealed several negative values (by up to 3 dB) at the start of some profiles. Reasonable temperature and salinity values accompanied the negative pressures, which casts some doubt on the accuracy of the pressure calibration. The affected data values have been flagged as suspect.


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

Bissett-Berman 9060 Salinity Temperature and Depth

The B-B 9060 STD measured salinity, temperature and depth and whose analogue output was in graphical form. The plots created were of salinity and temperature versus depth which had to be manually digitised.

RRS Challenger 8/76 STD Data Documentation

Introduction

Documentation for the STD data collected on RRS Challenger Cruise 8/76 (May 1976) by the Scottish Marine Biological Association, Oban, Argyll, Scotland, UK, under the direction of D. J. Ellett.

Caution

Inspection of the pressure records from this cruise reveals several negative values (by up to 3db) at the start of some records, (while the temperature and salinity values appear reasonable), thus casting some doubt on the accuracy of the pressure calibration. These data values have been flagged.

Note that the sea floor depths for C876/036 and C876/041 (BODC Series Reference 91512 and 91573) are given as 47m and 70m respectively, these are less than the maximum depth attained by the STD by more than 10 per cent.

Instrumentation

The instrument used was a Bissett Berman STD system and the data were logged on a Hewlett Packard 9820. Instrument lowering and raising speeds between 0.5 m/s and 1 m/s. An acoustic pinger was placed above the STD to give an accurate depth measurement, this could then be used to check the STD pressure calibration. An NIO bottle with reversing thermometers was placed above the pinger, within 2m of the STD system. A bottle sample was taken at the bottom of the cast providing the temperature and salinity are uniform at that point. If large temperature or salinity gradients were present then the bottle sample was triggered at a suitable site on the upcast. A surface salinity sample was also taken at the start of the dip.

Calibration

The STD was not calibrated in the laboratory. The manufacturer's calibration was used and water samples taken to check the calibration and apply corrections where necessary.

Temperature

The manufacturer's calibration was used to convert the raw data to physical units using the equation below:

Temperature (°C) = (10 6 /Pt - 2238.68)/55.84
where Pt is the temperature period in microseconds

These values were then plotted against the water bottle (i.e. reversing thermometer) temperatures and a regression line fitted to the data such that:

Temperature(WB) = m x Temperature(STD) + c

Then the regression coefficients (m and c) were applied to correct the STD temperature data - these are given in the table below.

Salinity

The manufacturer's calibration was used to convert the raw data to physical units using the equation below:

Salinity (ppt) = (10 6 /Ps - 4995)/290.6 + 30
where Ps is the salinity period in microseconds

These values were then plotted against the STD salinity and a regression line fitted to the data such that:

Salinity(WB) = m x Salinity(STD) + c + (m1 x Pressure + c1)/1000

Then the regression coefficients were applied to correct the STD salinity data. The data showed a salinity - pressure dependency, this was corrected by plotting delta-S (i.e. calibrated salinity - calculated salinity) against pressure to determine the slope (m1) and intercept (c1). These were then incorporated into the equation as shown above. The regression coefficients are given in the table below.

Pressure

The depths from the acoustic pinger were noted where the bottle samples were taken and then used to check the calibration of the pressure sensor - unless calibration values were available from the reversing thermometers. The equation below was used to convert the pressure period to physical units.

Pressure = (10 6 /Pd - 9712)/0.26267
where Pd is the pressure period in microseconds

A regression fit was carried out using the calibration values and the slope and intercept determined. The pressure values could then be corrected using:

Pressure (CORR) = m x Pressure(STD) + c

The fit of the STD data to the water bottle calibration data is given in the table below:

Variable Slope (m) Intercept (c) Standard
Deviation
Temperature (°C) 0.9949 0.0891 0.008
Salinity (ppt) 1.0060 -0.2831 0.022
Pressure (dbar) 0.4969 -4.5858 3.684
Delta-S -0.0122 29.8937 8.545

Data processing

Obvious wild points were edited out of the calibration file and the calibration programs run to obtain values for the slopes and intercepts for temperature, pressure and salinity. These were then applied to the uncalibrated data and sigma-t was calculated. The data values were then sieved to ensure a minimum separation between pressure values of 1 dbar. The data were then visually inspected and major spikes flagged.

References

Sharples, F. (1987).
A new data bank of SMBA STD/CTD observations in the Rockall Trough 1975-84. SMBA Marine Physics Group Report No. 36.

Graham, J.M., Sharples, F., Meldrum, D.T. and Edwards, A. (1987).
STD observations in the Rockall Trough 1975-77. SMBA Marine Physics Group Report No. 39.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name CH8/76
Departure Date 1976-05-19
Arrival Date 1976-06-01
Principal Scientist(s)David J Ellett (Scottish Marine Biological Association)
Ship RRS Challenger

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameDML Line HD
CategoryOffshore route/traverse

DML Line HD

Line HD is a survey section crossing the Sea of the Hebrides, between Loch Boisdale (South Uist, Scotland) and Loch Moidart on the west coast of Scotland (to the south east of the Isles of Eigg and Muck). The line comprises nine fixed STD/CTD stations, which were established as part of routine monitoring work on the Scottish continental shelf by Dunstaffnage Marine Laboratory (DML). The line was occupied in the mid 1970s to early 1990s.

Line HD has also occasionally been referred to as Line DN.

Nominal station details

DML Line HD: Loch Boisdale (South Uist, Scotland) - Loch Moidart (mainland Scotland)

Station Nominal latitude Nominal longitude Approx.
depth (m)
Comment
HD1 57° 08.3' N 07° 11.0' W 106 Near Loch Boisdale
HD2 57° 05.3' N 07° 00.5' W 135  
HD3 57° 02.3' N 06° 50.0' W 100  
HD4 56° 59.0' N 06° 38.0' W 110 South of Canna
HD5 56° 56.5' N 06° 29.2' W 80  
HD6 56° 54.0' N 06° 21.0' W 84 Sound of Rhum
HD7 56° 51.5' N 06° 12.2' W 55 South of Eigg
HD8 56° 49.5' N 06° 05.0' W 88  
HD9 56° 48.0' N 05° 56.0' W 62 Near Loch Moidart

Other Series linked to this Fixed Station for this cruise - 91794 91825

Other Cruises linked to this Fixed Station (with the number of series) - CH10/81 (1) CH14 (9) CH2/78 (9) CH2/84 (9) CH22 (9) CH4/85 (8) CH6/78 (7) CH6A/81 (7) CH71A (10) CH8/85 (6) CH89B (3) CH9 (4) CH9/78 (7) FR18/87 (9) LF2/89 (9) S5/79 (2)

Fixed Station Information

Station NameDML Line HD Station HD8
CategoryOffshore location
Latitude56° 49.50' N
Longitude6° 5.00' W
Water depth below MSL88.0 m

DML Station HD8

Station HD8 is one of nine fixed STD/CTD stations crossing the Sea of the Hebrides, between South Uist and the west coast of Scotland. The station was established by scientists at Dunstaffnage Marine Laboratory (DML).

Other Cruises linked to this Fixed Station (with the number of series) - CH14 (1) CH2/78 (1) CH2/84 (1) CH22 (1) CH4/85 (1) CH6/78 (1) CH6A/81 (1) CH71A (1) CH9/78 (1) FR18/87 (1) LF2/89 (1)

Fixed Station Information

Station NameDML Sea of the Hebrides STD/CTD Sections
CategoryOffshore area
Latitude56° 57.39' N
Longitude6° 47.91' W
Water depth below MSL

DML Sea of the Hebrides STD/CTD Sections

The Sea of the Hebrides lies between the southernmost islands of the Outer Hebrides and, to the east, the northern Inner Hebridean islands and Scottish mainland. This area of the shelf has been surveyed since the mid 1970s by numerous research and government institutes. The region contains many repeated hydrographic stations, which collectively form transects. These repeated survey transects form part of a greater network of similar sections on the western Scottish continental shelf, which were established by Dunstaffnage Marine Laboratory (DML).

Map of standard Sea of the Hebrides STD/CTD Stations

BODC image

Map produced using the GEBCO Digital Atlas.

The triangles and squares indicate the nominal positions of individual Line HD and HE stations respectively. Measurements made at repeated Sea of the Hebrides STD/CTD stations lie within a box bounded by co-ordinates 56.6° N, 7.664° W at the south west corner and 57.313° N, 5.933° W at the north east corner.

Several repeated hydrographic stations on the Ellett Line/Extended Ellett Line occupy the southern area of the Sea of the Hebrides. Further information about these survey transects are summarised here.

Nominal station details:

DML Line HD: Loch Boisdale (South Uist, Scotland) - Loch Moidart (mainland Scotland)

DML Line HE: Loch Bracadale (Skye, Scotland) - north west of Canna (Scotland)

Other Series linked to this Fixed Station for this cruise - 91794 91825

Other Cruises linked to this Fixed Station (with the number of series) - CH10/81 (7) CH14 (14) CH2/78 (9) CH2/84 (9) CH22 (14) CH4/85 (13) CH6/78 (10) CH6A/81 (12) CH71A (15) CH8/85 (6) CH89B (8) CH9 (4) CH9/78 (9) FR18/87 (14) LF2/89 (14) S5/79 (7)


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