Metadata Report for BODC Series Reference Number 338744

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

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

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.

Specifications

* Conductivity specifications are given in terms of equivalent salinity

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

RV Corystes Cruise 11/92 CTD Data Documentation

CTD: S/N 45056

(1) A total of 68 valid profiles were collected during the cruise. Reversing thermometers were used on only the first 20 (stns 10- 38). Samples for analysis were collected from the near-surface and near-bed. Not all the calibration data collected were used to calibrate the CTD:

1. Thermometer differences > 0.04 were discounted (4 deleted).

2. Salinity and CTD differences > 0.03 were discounted (3 deleted).

3. The first station (10) was at anchor off Killingholme, River

Humber. One set of thermometers failed and one set of duplicate salinities was in very poor agreement. This station was discarded for calibration purposes.

(2) The pressure sensor was corrected using the laboratory calibration of August 1992 at T = 16.2 °C.

P(cor) = P(ctd) - 1.4

(3) The temperature sensor was corrected using the laboratory calibration of August 1992.

T(cor) = T(ctd) + dT

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

where
a = -1.18042e-05
b = 3.74e-04
c = 1.0502e-02

This amounts to 13 mK for the range of temperatures encountered 16 °C to 11 °C.

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 of the Laboratory calibration are acceptable i.e. those within 43 mK and - 17 mK. All of the 37 values were found to inside this range.

The mean of the 37 differences was 20 mK.

(4) Fig. 2 shows how the uncorrected CTD salinity estimates compared with salinity measurements from the salinometer. (Note that CTD measurements of pressure, temperature and conductivity have not been corrected; the CTD salinity is derived from uncorrected observations). The salinity sensor was calibrated using the equation:

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

where
a = -0.920897052e-4
b = -0.227664036e-5
c = 0.100148999e+1

The rms difference between salinometer and CTD salinity was 0.011 for 117 observations.

Fig. 3 shows the ratio of the conductivities of CTD cf water samples before correction of CTD conductivity ratio.

Fig. 4 shows the differences between water sample salinity and CTD salinity after all the sensors have been calibrated.

Fig. 5 shows the difference between water sample (salinometer) and CTD salinity before and after the calibration of the conductivity sensor has been applied. Note that for the upper histogram the CTD salinity has been derived from corrected CTD pressure and temperature but uncorrected conductivity ratio. This figure therefore indicates how effective the conductivity calibration has been. If it is assumed that the CTD salinity is accurate to 0.01 and the salinometer is accurate to 0.006, then differences less than or equal to 0.016 are acceptable. Only 14 of 117 are outside this range after the sensor calibrations have been applied.

(5) There were two transmissometers used during this cruise, the 5 cm and 25 cm. The readings were converted using the following calibrations:

Stns 10-92 (5 cm)
Susp.Loas = -53.5 x LOGe %Transmission + 209.5

Stns 93-194 (25 cm)
Susp.Load = -3.77 x LOGe %Transmission + 16.41

(6) Fig. 6 gives the general distribution of the stations on this cruise:

10 Killingholme, River Humber
11-2, 54 River Humber to The Wash
32-52 The Wash
56-112 North Sea
118-194 Coastal waters between River Tees and north of Aberdeen

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:

• Irregularities such as unfeasible values
• Inconsistencies between related information, for example:
  • Times for instrument deployment and for start/end of data series
  • Length of record and the number of data cycles/cycle interval
  • Parameters expected and the parameters actually present in the data cycles
• Originator's comments on meter/mooring performance and data quality

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:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

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:

• Maximum and minimum values of parameters (spikes excluded).
• The occurrence of meteorological events.

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:

• To measure the fluxes of nutrient elements (N, P, Si) through selected major estuaries on a quantitative annual basis in order to determine the net input to the sea resulting from gross river inputs.
• To quantify the processes controlling the fluxes of nutrients through estuaries.

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:

Data Activity or Cruise Information

Cruise

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: