Metadata Report for BODC Series Reference Number 175931


Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
NameCategories
Neil Brown Smart CTD  CTD; water temperature sensor; salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Scottish Office Agriculture and Fisheries Department Aberdeen Marine Laboratory (now Marine Scotland Aberdeen Marine Laboratory)
Processing Status banked
Project(s) -
 

Data Identifiers

Originator's Identifier 27/06/0198
BODC Series Reference 175931
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1988-06-25 11:06
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval -
 

Spatial Co-ordinates

Latitude 59.00010 N ( 59° 0.0' N )
Longitude 5.00480 W ( 5° 0.3' W )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor Depth 1.59 m
Maximum Sensor Depth 71.81 m
Minimum Sensor Height 4.18 m
Maximum Sensor Height 74.41 m
Sea Floor Depth 76.0 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
CNDCPR01 1 Siemens per metre InSituCond Electrical conductivity of the water body by in-situ conductivity cell
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
PSALPR01 1 Dimensionless P_sal Practical salinity of the water body by conductivity cell and computation using UNESCO 1983 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

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."


Narrative Documents

Neil Brown Smart Conductivity, Temperature and Depth profiler

The Smart CTD was developed by WHOI, Neil Brown Instrument Systems and MIT and consists of an internally recording CTD which can be programmable to accommodate various sampling schemes. The data retrieval is done via connectors to a computer, where it is digitally logged.

This instrument was designed to be used with minimal technical expertise and to be replaced if problems arise, rather than being repaired at sea.

RV Scotia 6/68 Leg 2 CTD Data Documentation

Introduction

Documentation for CTD data collected on R.V. Scotia Cruise 6/88 leg 2 (17 th - 28 th June 1988) by the Department of Agriculture and Fisheries for Scotland, Aberdeen, UK under the direction of E. Henderson.

Instrumentation

The instrument used was a Neil Brown Instrument Systems SMART CTD which logged data into its internal memory. Conductivity, temperature and pressure only were logged. The instrument has two modes of operation: either raw or averaged data can be collected. The former produces data at a rate of 5 scans/second and the latter 1 scan every 0.96 sec. So far the instrument has always been used in the averaging mode. An EPROM in the instrument contains a routine which does the averaging, and also introduces the time lags required for matching the responses of the different sensors. The internal memory of the instrument is 40,000 scans of data.

Sampling

The CTD was lowered, at rates of between 30 and 40 metres/minute, (i.e. 1 scan approximately every metre) to within 5-10 m of the sea floor (this depth being taken from soundings). Although CTD data were collected both on the downcast and the upcast; only the data from the downcast were used and compared with the bottle samples. The CTD data were then read back into the shipborne computer, an HP85, salinity was calculated and data plotted out - as a quick look check on the data.

A calibration station (using reversing thermometers and water bottles) was taken every 4-5 CTD stations. CTDs and bottle samples may be taken at the same site; in which case the CTD cast was carried out first, and the bottle station immediately afterwards - this only occurred when the bottle stations were required for chemical data. The ship's winches are too close together to allow the two to be done simultaneously. At the hydrographic stations 2, 3 or 4 bottle samples were taken together with reversing thermometer measurements.

Calibration

The CTD is returned occasionally to the manufacturer in the USA for re-calibration at the factory - this was done in January 1985 and again in April 1988. At the factory the re-calibration is burnt into the EPROM. Memory is available on the EPROM for the addition of software for bench testing temperature and pressure, if required. However the CTD is not calibrated at DAFS as there is no calibration facility. Although there is little drift in the instrument, over a couple of years there is sufficient to warrant returning the instrument to the factory.

Data Processing

In the laboratory, the data were transferred onto a VAX 11/750 computer together with the header information from the log. Any spikes encountered were treated in one of the following ways:

  1. If the spike is small, (i.e. less than 4 observations) the data values were deleted, leaving a gap.

  2. Data were interpolated for spikes of greater than 4 observations. Usually, for data below the thermocline a linear interpolation was applied; for data in the thermocline a cubic spline was employed.

Pressure, temperature and conductivity data values were supplied to BODC. Conductivity was converted to conductivity ratio and then converted to salinity using UNESCO recommended routines.

Caution

The following 2 series are very noisy over the depth range specified and should be treated with caution:

Originator's Reference BODC Series Reference Depth range (decibars)
27/06/0150 175408 0 - 19
27/06/0156 175470 9 - 27

Note also, the temperature, conductivity and salinity data from the top 12 decibars of the water column for Originator's Reference 27/06/0236 (i.e. BODC Series Reference 176344) appear suspect and should be treated with caution.

Reference

Fofonoff, N.P. and Millard Jr., R.C. (1983).
Algorithms for the computation of fundamental properties of sea water. UNESCO Technical Paper on Marine Science 44.


Project Information


No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Cruise Name 0688S_2
Departure Date 1988-06-17
Arrival Date 1988-06-28
Principal Scientist(s)J H Anthony Martin (Scottish Office Agriculture and Fisheries Department Aberdeen Marine Laboratory)
Ship FRV Scotia

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