Metadata Report for BODC Series Reference Number 971987


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 Dr Meric Srokosz
Originating Organization James Rennell Centre for Ocean Circulation (now National Oceanography Centre, Southampton)
Processing Status banked
Project(s) WOCE
UK WOCE
 

Data Identifiers

Originator's Identifier CTD62A12
BODC Series Reference 971987
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1991-09-13 23:13
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 2.0 decibars
 

Spatial Co-ordinates

Latitude 62.64433 N ( 62° 38.7' N )
Longitude 5.21600 W ( 5° 13.0' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 2.97 m
Maximum Sensor Depth 542.99 m
Minimum Sensor Height 20.11 m
Maximum Sensor Height 560.13 m
Sea Floor Depth 563.1 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
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 62A CTD Data Documentation

Introduction

CTD profile data are presented from the ERS-1 validation cruise Charles Darwin 62A, as reported by Srokosz et al. (1992). The data collection and calibration procedures have been described by Tokmakian et al. (1992).

Instrumentation and Methodology

Instrumentation Summary

The CTD profiles were taken with a Neil Brown Systems MkIIIb CTD mounted beneath a bottle rosette. The CTD was fitted with a pressure sensor, conductivity cell, platinum resistance thermometer, a dissolved oxygen sensor, an Aquatracka fluorometer, a Sea Tech 25cm path transmissometer and an IOS 10kHz pinger.

Data Acquisition

Lowering rates for the CTD package were generally in the range 0.5 -1 .0ms -1 but could be up to 1.5ms -1 . CTD data were logged at 16 frames per second. The CTD deck unit passes raw data to a dedicated Level A microcomputer where 1 second averages are assembled. During this process the Level A calculates the rate of change of temperature and a median sorting routine detects and removes pressure spikes. These data are sent to the Level B for archival. The data are then passed to a Level C workstation for conversion to Pstar format and calibration.

A total of 27 stations (01 - 29) were occupied. Station 01 was a test dip and station 10 a failure. Station 11 was a repeat of station 10. The reversing thermometer T260 was only used at station 02.

Data Processing

The 1 second data passed to the Level C were converted to Pstar format and initially calibrated with coefficients from laboratory calibrations. The up cast data were extracted for merging with the bottle firing codes, on time, thus the CTD variables were reconciled with the bottle samples. Final calibrations were applied using the sample bottle data.

The data were worked up to WOCE standards by the data originators before being supplied to BODC. The oxygen, fluorometer and transmissometer data cannot be used because of problems with the calibration coefficients supplied by RVS.

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.

The CTD data were received as 2db averaged pressure sorted down cast data. Parameters were pressure (dbar), temperature (°c), and salinity (psu). The oxygen, fluorescence and attenuance data were ignored.

The data were converted into the BODC internal format (PXF) to allow the use of in-house software tools, notably the graphics editor. During this process all the oxygen, fluorometer and transmissometer data were set null. 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. These data from cruise CD62A required little flagging and just a few points were set suspect.

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 time the CTD reached the bottom. The start time is more precisely the start of data logging. Latitude and longitude are the mean positions between the start and end times calculated from the master navigation in the binary merged file.

References

Srokosz, M.A. et al. (1992). RRS Charles Darwin Cruise 62A. Institute of Oceanographic Sciences Deacon Laboratory, Cruise Report No. 229, 49pp.

Tokmakian, R.T. et al. (1992). CTD and XBT collected on ERS-1 validation cruise RRS Charles Darwin Cruise 62A, Iceland-Faeroes region. Institute of Oceanographic Sciences Deacon Laboratory, Report No. 294, 86pp.


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 CD62A
Departure Date 1991-09-06
Arrival Date 1991-09-28
Principal Scientist(s)Meric Srokosz (James Rennell Centre for Ocean Circulation)
Ship RRS Charles Darwin

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NameWOCE-AR18
CategoryOffshore area
Latitude65° 0.00' N
Longitude9° 0.00' W
Water depth below MSL

World Ocean Circulation Experiment (WOCE) Atlantic Area 18 (AR18)

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

AR18 encompasses the Norwegian Sea basin and stations lie within a box bounded by 69°N, 38°W at the northwest corner and 60°N, 16°E at the southeast corner. The area was occupied between September 1991 to September 1997. A table of all AR18 cruises is presented below:

Cruise Cruise dates Country
Charles Darwin 62A 1991-09-06 to 1991-09-28 UK
Johan Hjort 1092 1992-07-12 to 1992-07-28 Norway
Aranda 1993 1993-08-23 to 1993-09-24 Finland
Johan Hjort 0894 1994-07-23 to 1994-08-16 Norway
Johan Hjort 19941029 1994-10-29 to 1994-11-23 Norway
Bjarni Saemundsson 1495 1995-09-05 to 1995-09-14 Iceland
Aranda 1997 1997-08-05 to 1997-09-25 Finland

Other Series linked to this Fixed Station for this cruise - 971883 971895 971902 971914 971926 971938 971951 971963 971975 971999 972002 972014 972026 972038 972051 972063 972075 972087 972099 972106 972118 972131 972143 972155 972167 972179


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