Metadata Report for BODC Series Reference Number 978311


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Prof Andy Watson
Originating Organization Plymouth Marine Laboratory (now Marine Biological Association of the UK)
Processing Status banked
Project(s) WOCE
UK WOCE
 

Data Identifiers

Originator's Identifier CTD180
BODC Series Reference 978311
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1993-05-11 05:33
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars
 

Spatial Co-ordinates

Latitude 24.50217 N ( 24° 30.1' N )
Longitude 35.25583 W ( 35° 15.3' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 9.94 m
Maximum Sensor Depth 496.2 m
Minimum Sensor Height 5454.41 m
Maximum Sensor Height 5940.67 m
Sea Floor Depth 5950.61 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 Chart reference - Depth extracted from available chart
 

Parameters

BODC CODE Rank Units Short Title Title
POTMCV01 1 Degrees Celsius WC_Potemp Potential temperature of the water body by computation using UNESCO 1983 algorithm
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
PSALST01 1 Dimensionless P_sal_CTD Practical salinity of the water body by CTD and computation using UNESCO 1983 algorithm
SIGTPR01 1 Kilograms per cubic metre SigTheta Sigma-theta of the water body by CTD and computation from salinity and potential temperature using UNESCO algorithm
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

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

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.

Specifications

These specification apply to the MK3C version.

Pressure Temperature Conductivity
Range

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm -1
Accuracy

0.0015% FS

0.03% FS < 1 msec

0.0005°C

0.003°C < 30 msec

0.0001 S cm -1

0.0003 S cm -1 < 30 msec

Further details can be found in the specification sheet .

RRS Charles Darwin 78 CTD Data Documentation

Introduction

CTD profile data are presented from the North Atlantic Tracer Release Experiment cruise Charles Darwin 78 as reported by Watson & Ledwell et al. (1993).

Instrumentation and Methodology

Instrumentation Summary

The CTD profiles were taken with a Neil Brown Systems MkIII CTD (s/n 01-1195) mounted beneath a bottle rosette. The CTD was fitted with a pressure sensor, conductivity cell, and a platinum resistance thermometer.

Data Acquisition

Lowering speeds were about 30m/min to 50m and then slowly increased to about 60m/min to 500m.

A total of 207 casts were conducted (001 - 241). There were no casts in the numbering sequence 066 - 099.

Data Processing

The raw data were averaged down to 1db values.

Temperature

A laboratory temperature calibration performed just prior to the cruise indicated that the primary PRT was within 0.0005°C of the bath standard. No adjustment was made for a temperature offset.

Pressure

The pressure sensor read high by 4.7db at the surface, and this amount was subtracted from all pressures throughout the cruise.

Salinity

Salinity samples taken on each cast showed the salinity reading from the system to be low by 0.028-0.029psu during the first few stations. The constants in the acquisition system had already been set to compensate for a raw salinity that was low by 0.018psu. Thus, another 0.011psu were added to the salinity calculated using these constants.

Note: the cruise report goes on to say that the CTD was re-calibrated after station 53. Archived data for stations 1-53 were re-calculated using the new calibration.

BODC Data Processing

No further calibrations were applied to the data received by BODC. BODC were mainly concerned with the screening and banking of the data. BODC have not received the CTD data from casts 218 and 241.

The CTD data were received as 1db averaged pressure sorted down cast data. Parameters were pressure (dbar), temperature (its-90) and salinity (pss-78).

The data were converted into the BODC internal format (PXF) to allow the use of in-house software tools, notably the graphics editor. Spikes in the data were manually flagged 'suspect' by modification of the associated quality control flag. In this way none of the original data values were edited or deleted during quality control.

Some files had bad final few cycles where pressure was over ~500db and these cycles were deleted. Also, had to edit out from 10-70db for cast 6 because T+S were corrupt.

Very little flagging was required for these data.

Once screened, the CTD data were loaded into a database under the Oracle relational database management system. The start time stored in the database is the CTD deployment time, and the end time is the start time + 60 minutes. 1 day was subtracted from all these times after comparison with the cruise report.

References

Watson, A.J. & Ledwell, J.R. et al. (1993). RRS Charles Darwin Cruise CD78, The North Atlantic Tracer Release Experiment: Final Sampling Leg. Plymouth Marine Laboratory, Cruise Report.


Project Information

World Ocean Circulation Experiment (WOCE)

The World Ocean Circulation Experiment (WOCE) was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate.

WOCE had two major goals:


UK WOCE

The UK made a substantial contribution to the international World Ocean Circulation Experiment (WOCE) project by focusing on two important regions:

  1. Southern Ocean - links all the worlds oceans, controlling global climate.
  2. North Atlantic - directly affects the climate of Europe.

A major part of the UK effort was in the Southern Ocean and work included:

In the North Atlantic the UK undertook:

Satellite ocean surface topography, temperature and wind data were merged with in situ observations and models to create a complete description of ocean circulation, eddy motion and the way the ocean is driven by the atmosphere.

The surveys were forerunners to the international Global Ocean Observing System (GOOS). GOOS was later established to monitor annual to decadal changes in ocean circulation and heat storage which are vital in the prediction of climate change.


Data Activity or Cruise Information

Cruise

Cruise Name CD78
Departure Date 1993-04-21
Arrival Date 1993-05-25
Principal Scientist(s)Andrew J Watson (Plymouth Marine Laboratory)
Ship RRS Charles Darwin

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameWOCE Atlantic Area 10 (AR10)
CategoryOffshore area
Latitude27° 0.00' N
Longitude32° 30.00' W
Water depth below MSL

World Ocean Circulation Experiment (WOCE) Atlantic Area 10 (AR10)

WOCE was a major international experiment which made measurements and undertook modelling studies of the deep oceans in order to provide a much improved understanding of the role of ocean circulation in changing and ameliorating the Earth's climate. WOCE established numerous areas and repeat sections in the Atlantic Ocean as illustrated in the map below.

BODC image

The AR10 'Beta-triangle' experiments where centred at 27.0°N, 32.5°W in the southwestern end of the North Atlantic subtropical gyre, with the area occupied between May 1992 to May 1993. A table of all AR10 cruises is presented below:

Cruise Cruise dates Country
Charles Darwin 68 1992-05-08 to 1992-06-08 UK
Oceanus 1992-09-21 to 1992-10-21 USA
Oceanus 1992-10-29 to 1992-11-16 USA
Hudson 1993-04-05 to 1993-05-14 Canada
Charles Darwin 78 1993-04-22 to 1993-05-24 UK

Other Series linked to this Fixed Station for this cruise - 976709 976710 976722 976734 976746 976758 976771 976783 976795 976802 976814 976826 976838 976851 976863 976875 976887 976899 976906 976918 976931 976943 976955 976967 976979 976980 976992 977006 977018 977031 977043 977055 977067 977079 977080 977092 977111 977123 977135 977147 977159 977160 977172 977184 977196 977203 977215 977227 977239 977240 977252 977264 977276 977288 977307 977319 977320 977332 977344 977356 977368 977381 977393 977400 977412 977424 977436 977448 977461 977473 977485 977497 977504 977516 977528 977541 977553 977565 977577 977589 977590 977608 977621 977633 977645 977657 977669 977670 977682 977694 977701 977713 977725 977737 977749 977750 977762 977774 977786 977798 977805 977817 977829 977830 977842 977854 977866 977878 977891 977909 977910 977922 977934 977946 977958 977971 977983 977995 978009 978010 978022 978034 978046 978058 978071 978083 978095 978102 978114 978126 978138 978151 978163 978175 978187 978199 978206 978218 978231 978243 978255 978267 978279 978280 978292 978323 978335 978347 978359 978360 978372 978384 978396 978403 978415 978427 978439 978440 978452 978464 978476 978488 978507 978519 978520 978532 978544 978556 978568 978581 978593 978600 978612 978624 978636 978648 978661 978673 978685 978697 978704 978716 978728 978741 978753 978765 978777 978789 978790 978808 978821 978833 978845 978857 978869 978870 978882 978894 978901 978913 978925 978937 978949 978950

Other Cruises linked to this Fixed Station (with the number of series) - CD68 (44)


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