Metadata Report for BODC Series Reference Number 339803

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Guildline Model 8705 Digital CTD  salinity sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization Ministry of Agriculture, Fisheries and Food Lowestoft Fisheries Laboratory (now Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) Joint Nutrient Study I (JoNuS)

Data Identifiers

Originator's Identifier CO1/92/51
BODC Series Reference 339803

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1992-01-16 19:46
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 decibars

Spatial Co-ordinates

Latitude 53.07880 N ( 53° 4.7' N )
Longitude 0.50070 E ( 0° 30.0' E )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 2.0 m
Maximum Sensor or Sampling Depth 27.8 m
Minimum Sensor or Sampling Height 6.2 m
Maximum Sensor or Sampling Height 32.0 m
Sea Floor Depth 34.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling 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


BODC CODERankUnitsTitle
PRESPR011DecibarsPressure (spatial coordinate) exerted by the water body by profiling pressure sensor and correction to read zero at sea level
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPST011Degrees CelsiusTemperature 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

Centre for Environment, Fisheries and Aquaculture Science (Cefas) data access conditions

The Centre for Environment, Fisheries and Aquaculture Science (Cefas) is an Executive Agency of the Department of Environment, Food and Rural Affairs (Defra), formerly the Ministry of Agriculture, Fisheries and Food (MAFF). It was also known previously as the Directorate of Fisheries Research (DFR). This data policy refers to data collected by the organisation under all titles.

Narrative Documents

Guildline 8705 CTD

The 8705 CTD is a conductivity-temperature-pressure profiler designed for marine applications down to depths of 6000 m. The instrument includes an anodised aluminium tube with a steel cage to protect the temperature and conductivity sensors and a urethane cap to protect the pressure sensor.


Parameter Range Accuracy Resolution Stability Response time
Pressure 0 to 6000 dbar ± 0.15% of full range ± 0.01% of full range - < 50 ms
Temperature -2 to 30 °C ± 0.005 °C ± 0.0005 °C

± 0.002 °C over 30 days

± 0.0025°C over 6 months

< 50 ms
Conductivity * 100 ppm to 40 ppt ± 0.005 ppt ± 0.001 ppt ± 0.002 ppt over 6 months < 50 ms

* Conductivity specifications are given in terms of equivalent salinity

Further details can be found in the manufacturer's specification sheet.

RV Corystes Cruise 1/92 CTD Data Documentation


The CTD used was S/N 45056. The transmissometer used during the cruise was S/N 479, with a 5 cm path.

Sampling Protocol

Eighty-two CTD profiles were obtained during the cruise. Reversing thermometers were fitted to the Niskin used to collect samples from close to the seabed. Samples for salinity analysis were collected from both near the surface and close to the seabed.


Not all the calibration data collected were used to calibrate the CTD sensors for the following reasons:

  1. Thermometer differences too large (>0.02).

  2. It was clear from the profiles obtained at the time of station that some T and/or S values measured by the CTD were variable, believed real, not an instrument malfunction, and unsuitable for calibration use. Eighteen data sampling points were not used because of this.


The pressure sensor was corrected using the laboratory calibration of September 1991 at T = 12 °C.

P(cor) = P(ctd) - 1.6

Normally this is checked by comparing CTD pressure with that derived from water depth and altimeter height, but a fault with the altimeter throughout this cruise made this impractical.


The temperature sensor was corrected using laboratory calibration of December 1991.

T(cor) = T(ctd) + dT

dT = a*T(ctd)*T(ctd) + b*T(ctd) + c


a = -2.59480e-6
b = -1.60314e-4
c = 3.128e-3

These coefficients are equivalent to a correction of approximately 2 mK for the range of temperatures encountered during the cruise.

A comparison between thermometer and uncorrected CTD temperatures is shown in Fig. 1. If it is assumed that the thermometer temperatures are accurate to 0.02 °C and the CTD to 0.01 °C then all differences to within 0.03 °C are acceptable. Only four out of sixty-nine values are outside this range and the mean difference is 0.002 °C.


One hundred and forty two salinity samples were used to calibrate the conductivity sensor.

CR(cor) = CR(ctd)*[ a*T(cor) + b*P(cor) + c ]


a = -1.467061e-5
b = 2.790880e-6
c = 0.999653

The rms difference between salinometer and corrected CTD salinity was 0.018.

Fig. 2 shows how effective these coefficients are in correcting the CTD salinity estimates for the calibration samples. Note that the CTD salinity of the upper histogram was derived after the CTD temperature and pressure had been corrected but prior to applying corrections to the CTD conductivity ratio. The Figure gives an indication of how well the CTD conductivity is corrected.

Fig. 3 displays the spread in the ratio of conductivity-ratio of the CTD to that of the water samples prior to applying the correction.

Fig. 4 shows the difference between the water sample salinity and the uncorrected CTD equivalent before any of the CTD sensors are corrected; the CTD is generally 0.02 too high.

Fig. 5 shows the difference between the water sample salinity and the corrected CTD equivalent after all three sensors (pressure, temperature and conductivity ratio) have been corrected.

Stations 23 to 45 are at or near the entrance to the Humber Estuary, stations 62 to 74 are well into the Wash whilst station 80 is at the outer Thames Estuary. The differences are relatively larger at these stations.

If the CTD is assumed to have an accuracy of 0.01 in terms of salinity and the salinometer of 0.006 then the corrected CTD salinity values should lie within 0.016. In this instance 28 out of 142 samples (20%) fall outside this range (see Fig. 2). If the data from the above stations are removed from the calibration this figure is reduced to 6 from 85 (7%) and the rms difference between corrected CTD and water sample salinity is 0.011; 7 from 85 lie outside ±0.013.

Suspended Load

The suspended load estimates from %transmission were calculated from the following:

suspended load (mg/litre) = B * ln (%transmission) + C

station number B C
1 to 21 -54.5 215.8
23 to 36 -69.0 263.8
37 to 48 -55.0 217.6
49 to 74 -52.1 205.0
77 to 83 -103.0 397.4
84 to 99 -79.1 309.1

These coefficients derived from suspended load measurements on samples collected whilst transmission being logged, two samples per station.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

Joint Nutrient Study I (JoNuS)

Concerns by the scientific community about the impact of nutrient inputs to the sea; a lack of information on inputs from the UK and on the spatial and temporal distribution and cycling of nutrients in UK waters provided the impetus for the JoNuS project.

The project sought to quantify the input of nitrogen, phosphorus and silicon from UK estuaries to the North Sea through a good understanding of the estuarine processes that control the flow of these nutrients. It focussed on the Great Ouse/Wash and the Humber outflows. Its specific objectives were:

The Centre for Environment, Fisheries and Aquaculture Science (CEFAS) hosted the project, which involved scientists from CEFAS, the University of East Anglia, the University of Essex, the Plymouth Marine Laboratory and the National Rivers Authority (now the Environment Agency). It was funded by the then Ministry of Agriculture, Fisheries and Food (MAFF) and the Department of Environment, now the Department of Environment, Food and Rural Affairs (Defra).

The project ran from April 1990 to March 1995, with marine field data collection between May 1990 and December 1993. Data collection involved ship based surveys which were complemented by estuarine transects and specific process studies.

Initially, the surveys were on a quarterly basis up to October 1992, however monthly surveys were carried out during 1993. During this intensive survey period, the programme focused on the Great Ouse/Wash; with a continuing, but lower level, of activity devoted to the Humber. An additional multi-project cruise, carried out in January 1995, also complemented the JoNuS data set. Further details of the JoNuS I cruises are provided below:

Cruise identifier Date Comments
RV Cirolana CIR5/90 1990-05-03 - 1990-05-20 None
RV Cirolana CIR7/90 1990-07-06 - 1990-07-25 None
RV Cirolana CIR10/90 1990-10-29 - 1990-11-16 None
Seeker 2/90 1990-10-29 - 1990-11-03 Sediment and water sample collection only
RV Cirolana CIR1/91 1991-01-05 - 1991-01-23 None
RV Cirolana CIR4/91 1991-04-12 - 1991-05-02 None
RV Cirolana CIR8A/91 1991-09-25 - 1991-10-09 None
RV Corystes (88-04) COR1/92 1992-01-03 - 1992-01-20 None
RV Corystes (88-04) COR3A/92 1992-02-14 - 1992-02-26 None
RV Cirolana CIR8/92 1992-07-29 - 1992-08-06 None
RV Corystes (88-04) COR11/92 1992-09-28 - 1992-10-12 None
RV Cirolana CIR1/93 1993-01-08 - 1993-01-22 None
RV Corystes (88-04) COR2A/93 1993-02-03 - 1993-02-07 None
RV Corystes (88-04) COR2C/93 1993-02-18 - 1993-02-24 None
RV Corystes (88-04) COR5A/93 1993-05-04 - 1993-05-10 None
RV Corystes (88-04) COR6A/93 1993-06-08 - 1993-06-14 None
RV Cirolana CIR7B/93 1993-07-26 - 1993-08-02 None
RV Corystes (88-04) COR9/93 1993-08-20 - 1993-08-26 None
RV Cirolana CIR9B/93 1993-09-30 - 1993-10-11 None
RV Corystes (88-04) COR13/93 1993-12-15 - 1993-12-21 None
RV Cirolana CIR1/95 1995-01-06 - 1995-01-31 None

Data Activity or Cruise Information


Cruise Name COR1/92
Departure Date 1992-01-03
Arrival Date 1992-01-20
Principal Scientist(s)Paul A Gurbutt (Ministry of Agriculture, Fisheries and Food Lowestoft Fisheries Laboratory)
Ship RV Corystes

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
Q value below limit of quantification