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Metadata Report for BODC Series Reference Number 946333


Metadata Summary

Data Description

Data Category Surface temp/sal
Instrument Type
NameCategories
SeaTech transmissometer  transmissometers
Chelsea Technologies Group Aquatracka fluorometer  fluorometers
Global Positioning Satellite System  NAVSTAR Global Positioning System receivers
Alpkem RFA/2 colorimetric autoanalyser  colorimeters; autoanalysers
OceanData TSG103 thermosalinograph  thermosalinographs; water temperature sensor; salinity sensor
Endeco model 1125 dissolved oxygen system  dissolved gas sensors
University of Liverpool cathodic stripping voltammetry metal analyser  metal analysers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Reg Uncles
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) LOIS River-Atmosphere-Coast Study (RACS)
 

Data Identifiers

Originator's Identifier CH119A_SURF
BODC Series Reference 946333
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1995-06-01 09:00
End Time (yyyy-mm-dd hh:mm) 1995-06-12 11:25
Nominal Cycle Interval 30.0 seconds
 

Spatial Co-ordinates

Southernmost Latitude 52.69530 N ( 52° 41.7' N )
Northernmost Latitude 55.91510 N ( 55° 54.9' N )
Westernmost Longitude 1.93340 W ( 1° 56.0' W )
Easternmost Longitude 2.21390 E ( 2° 12.8' E )
Positional Uncertainty 0.05 to 0.1 n.miles
Minimum Sensor or Sampling Depth 4.0 m
Maximum Sensor or Sampling Depth 4.0 m
Minimum Sensor or Sampling Height -
Maximum Sensor or Sampling Height -
Sea Floor Depth -
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor or Sampling Depth Datum Approximate - Depth is only approximate
Sea Floor Depth Datum -
 

Parameters

BODC CODERankUnitsTitle
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
ALATGP011DegreesLatitude north relative to WGS84 by unspecified GPS system
ALONGP011DegreesLongitude east relative to WGS84 by unspecified GPS system
ATTNMR011per metreAttenuation (red light wavelength) per unit length of the water body by 20 or 25cm path length transmissometer
COXXCVDX1Nanomoles per litreConcentration of cobalt {Co CAS 7440-48-4} per unit volume of the water body [dissolved plus reactive particulate phase] by UV digestion and cathodic stripping voltammetry
CPHLUW011Milligrams per cubic metreConcentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by Aquatracka fluorometer immersed in non-toxic supply and calibration against sample data
CUXXCVDX1Nanomoles per litreConcentration of copper {Cu CAS 7440-50-8} per unit volume of the water body [dissolved plus reactive particulate phase] by UV digestion and cathodic stripping voltammetry
DOXYPE011Micromoles per litreConcentration of oxygen {O2 CAS 7782-44-7} per unit volume of the water body [dissolved plus reactive particulate phase] by in-situ pulsed electrode
NTRIAAD21Micromoles per litreConcentration of nitrite {NO2- CAS 14797-65-0} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
NTRZAAD21Micromoles per litreConcentration of nitrate+nitrite {NO3+NO2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
PHOSAAD21Micromoles per litreConcentration of phosphate {PO43- CAS 14265-44-2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
PSALSG011DimensionlessPractical salinity of the water body by thermosalinograph and computation using UNESCO 1983 algorithm and calibration against independent measurements
SLCAAAD21Micromoles per litreConcentration of silicate {SiO44- CAS 17181-37-2} per unit volume of the water body [dissolved plus reactive particulate <0.4/0.45um phase] by filtration and colorimetric autoanalysis
TEMPSG011Degrees CelsiusTemperature of the water body by thermosalinograph and verification against independent measurements
TSEDTR011Milligrams per litreConcentration of suspended particulate material {SPM} per unit volume of the water body [particulate >unknown phase] by in-situ optical attenuance measurement and calibration against sample data

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

Transmissometer

  • Significant quantities of data are missing from an anchor station worked inside the mouth of the Humber on 08/06/1995 due to the transmissometer being saturated by the high suspended particulate matter concentrations encountered.

CH119a Hydrography Data Quality Report

Transmissometer

  • The data from 23:00 on 08/06/1995 until 07:00 on 10/06/1995 have been heavily flagged due to large numbers of spikes produced by bubbles in the water supply during rough weather.
  • Data were flagged for the following reasons:
    Instrument saturation (all light cut out by the suspended load) Routine maintenance (cleaning) Spikes caused by bubbles forming in the instrument housing, usually during rough weather. These were particularly noticeable on 13/12/1993, 15/12/1993 and 20-21/12/1993.

Dissolved Oxygen

  • Gap in data from 10:39 08/06/1995 to 13:35 08/06/1995

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

Alpkem RFA-2, RFA-300 and Astoria colorimetric autoanalysers

The Alpkem rapid flow analysers (RFA) and Astoria analyser are continuous flow analysers consisting of a sampler, peristaltic pump, analytical cartridge, heating bath, colorimeter, data station, and printer. The sample and reagant are pushed into the reaction cartridge by the pump, where air-segmentation bubbles are introduced to facilitate mixing. The solution is then analysed colorimetrically, with the absorbance of a specific wavelength of light being indicative of the concentration of the solution. These autoanalysers may be used to measure nutrient concentrations in seawater.

The Alpkem rapid flow analysers were manufactured by OI Analytical, with the RFA-300 being a precursor to the smaller RFA-2 (also known as the RFA II or RFA/2). Astoria Pacific Inc. bought the RFA line, upgraded the instrument and renamed it the Astoria analyser.

The Astoria analyser incorporates a six-channel digital detector, which allows analysis of four to six parameters from a single sample. The components of the system are the 311 XYZ Sampler, 322 Auxiliary Pump (for sampler wash), 302D Micropump (peristaltic pump), 303A Cartridge Base, with room for up to six chemistries, and 305D Digital Detector. The six channels of the 305D allow for extra channels that can be used for reference signals, and optional detectors (fluorometer, UV, and Flame) can be plugged into the system as well.

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

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

Global Positioning Satellite System

A location system of unspecified make or model that determines location on the Earth's surface using the Global Positioning Satellite Network. Angular co-ordinates are given relative to WGS84 CRS. Other parameters such as platform velocity may be derived from this.

SeaTech Transmissometer

Introduction

The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.

Specifications

  • Water path length: 5 cm (for use in turbid waters) to 1 m (for use in clear ocean waters).
  • Beam diameter: 15 mm
  • Transmitted beam collimation: <3 milliradians
  • Receiver acceptance angle (in water): <18 milliradians
  • Light source wavelength: usually (but not exclusively) 660 nm (red light)

Notes

The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.

A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.

Further details can be found in the manufacturer's Manual.

CH119_a Sea surface hydrography instrument details

CH119_a Sea surface hydrography instrument details

Underway hydrography was recorded by a suite of instruments in the ship's flow-through system. Instrument details are given in the table below.

Instrument type Make and model Serial Number Manufacturer's details available?
GPS unspecified - -
Thermosalinograph TSG103 - No
Fluorometer Chelsea Instruments Aquatracka - No
Transmissometer SeaTech 661nm, 25cm path - No
Dissolved oxygen probe Endeco type 1125 - No
Dissolved metal analyser University of Liverpool Cathodic Stripping Voltameter - No

CH119_a Sea surface Hydrography Series

Dissolved Oxygen

Dissolved oxygen was measured using two independent systems: an Endeco type 1125 pulsed dissolved oxygen controller multiplexed to two Endeco type 1128 dissolved oxygen probes and a self-logging YSI dissolved oxygen probe. However, the YSI probe flooded and provided no data for this cruise. The data from both probes of the Endeco system were compared with a set of calibration data obtained by semi-automated Winkler titration. Both sets of data were computed assuming zero salinity. Both probes performed well but Probe 2 exhibited lower drift and the data from this have been used.

The calibration obtained was:

Corrected oxygen (µM) = Raw oxygen * 2.0513 - 59.638

This was based on a set of 32 samples and the regression had an R2 value of 96.1%.

Nutrients

The nutrients were measured using an AlpKem auto-analyser connected to the pumped seawater supply by a continuous filter block (Morris et al, 1978). The chemistries used were:

Nitrate: Reduced to nitrite by a Cu/Cd coil, then reacted with sulphanilamide in acidic conditions to form a diazo compound that coupled with N-1-naphylethylenediamide dihydrochloride to form a reddish-purple azo dye.
Nitrite: As for nitrate without the reduction step.
Phosphate: Reduction of a phosphomolybdate complex in acid solution to 'molybdenum blue' by ascorbic acid with sensitivity enhanced by the catalytic action of antimony potassium tartrate.
Silicate: The method used for silicate was based on the reduction of a silicomolybdate in acidic solution to 'molybdenum blue' by ascorbic acid. Oxalic acid was introduced into the sample stream before the addition of ascorbic acid to eliminate interference from phosphates.

The colorimeter outputs were logged by a Level A connected to the chart recorder inputs. The system was calibrated by running nutrient-depleted seawater washes to determine baseline and sets of four standards. Standards were generally run at least once per day.

The following processing procedures were adopted by BODC to convert the raw voltage streams into nutrient concentrations.

The data were then segmented into internally consistent subsets (i.e. taking account of any instrumental change such as gain or baseline alterations documented by the analyst), with constant or linearly drifting baselines. For each segment, the baseline as a function of time was fitted to a linear regression, which was applied to standardise the segment to a baseline of zero.

The standard voltages were used to construct calibration curves to convert raw voltages into nutrient concentrations. Note that nutrient concentrations in the low-nutrient seawater matrix were determined manually from the autoanalyser chart rolls and added to the spike values for calibration curve generation.

The calibration equations were applied on a segment by segment basis to the data stream. All baseline and calibration equations were checked manually before they were used. Once concentrations had been calculated, checked and checked again, the custom baseline and standard flags were changed to suspect flags.

The data were subsequently quality controlled by inspection on a graphics workstation with particular attention paid to the concentrations obtained for the standards. Any data identified as suspect were flagged. These checks included comparative screening between the nutrient channels.

The nutrient time channels were adjusted to correct for the delay incurred whilst the sample passed through the complex plumbing of the autoanalyser. No salt corrections (corrections for difference in optical density between sample and standards) were applied, as the standards were prepared in nutrient-depleted seawater.

The time corrections were determined by first synchronising nitrate with salinity using data from sharp gradients going into plumes where nitrate might be considered a conservative fresh-water tracer. The other nutrients were then synchronised to nitrate using data when standards were running.

The corrections applied were:

Nutrient Time Shift
NO3 -6mins
NO2 -3mins
PO4 -5mins
Si -5mins 30secs

Due to the chemistry used for the nitrate analysis, interference from nitrite is inevitable. The nitrate channel has been processed throughout as nitrate+nitrite and no attempt has been made to correct for nitrite. On this cruise the MilliQ water was found to have significant nitrite and phosphate contamination. In areas of low nutrient concentration, the MIlliQ baseline was visibly higher than the ambient signal. The nitrite and phosphate concentrations in the MilliQ were manually determined from the chart recorder output as 0.022 µM and 0.04 µM respectively. These values have been added to the ambient nitrite and phosphate data as a correction.

Trace metals

Dissolved trace metals were measured continuously on a clean surface water supply by cathodic stripping voltammetry (van den Berg and Achterberg, 1994) after UV digestion to break down any organometallic complexes.

Chlorophyll

Chlorophyll was measured by a Chelsea Instruments Aquatracka immersed in a light-tight pond. The fluorometer was calibrated by regressing the natural log of extracted chlorophyll concentration against corresponding fluorometer voltage. The following relationship was hence derived and used to compute the chlorophyll concentrations:

Chlorophyll (mg m-3) = exp (0.924*fluorometer voltage - 0.636) (n=34, R2=66.0%)

The calibration data set was obtained by fluorometric assay of acetone extracts from 0.2 micron Nuclepore filters.

Sea surface temperature and salinity

Temperature and salinity were measured using an autoranging TSG103 thermosalinograph. The temperature sensor was a thermistor in the non-toxic supply inlet manifold. Conductivity was measured by a unit in the ship's wet laboratory, which included a second thermistor to provide temperature for the computation of salinity.

The raw ADC counts were calibrated to give conductivity and two temperature channels based upon laboratory calculations by RVS. Salinity was computed from the housing temperature and conductivity using the UNESCO 1978 Practical Salinity Scale (Fofonoff and Millard, 1983).

The thermosalinograph was calibrated against surface values taken from the calibrated CTD. In the case of salinity, bottle samples analyzed by a Guildline Autosal bench salinometer also contributed to the calibration data set.

A constant offset of 0.168 was found for temperature. The salinity calibration was subdivided into segments as follows to correct for variable linear drift.

The linear drift model used was:

Corrected salinity = Raw salinity + A*cycle number + B

The values of the coefficients A and B were as follows:

01/06/1995 09:00:00 to 02/06/1995 01:08:00 A = 0.000088 B = 0.226

02/06/1995 01:08:30 to 03/06/1995 09:00:00 A = 0.0 B = 0.378

03/06/1995 09:00:30 to 12/06/1995 11:25:00 A = 0.0 B = 0.041

The dramatic change in salinity calibration was the result of routine maintenance on the thermosalinograph. These calibrations have been applied to the data.

Optical Attenuance and Sediment Load

Optical attenuance was measured using a SeaTech red light (661nm) transmissometer with a 25cm optical path length mounted in a light-tight box on the starboard deck continuously flushed by the non-toxic supply.

Transmissometer air readings made during the cruise were used to correct the transmissometer voltage to the manufacturer's specified voltage by ratio. The air reading used was 4.751 V and the manufacturer's voltage for the instrument was 4.789 V.

Attenuance = -4.0 * loge (voltage/5.0)

The transmissometer was calibrated in terms of sediment load using gravimetric data obtained by filtering water through tared GF/C filters. The following calibration was obtained by pooling the data obtained by the LOIS Core Team from PML on the three legs of Challenger 119:

SPM (mg/l) = (Attenuance - 0.3595) / 0.4468 (n=266, R2=91.8%)

However, on the third leg of the cruise (CH119C) a scientist from University of Wales, Bangor also measured sediment load by gravimetry at the same depths as the LOIS team using a newly implemented protocol. This involved the use of small (2.5 litre) CTD rosette bottles. The total contents of these was used as the UWB SPM sample whereas the PML sample was collected as a sub-sample from a 10 litre bottle risking sediment loss through settling. Comparing the two data sets showed the UWB data to be systematically significantly higher than the PML data. If these data were used to calibrate the underway transmissometer, the resulting calibration equation (for leg C) was:

SPM (mg/l) = (Attenuance - 0.192) / 0.3 (n=90, R2=86.2%)

The feature to note here is the slope of the UWB calibration is approximately 1.5 times that of the PML calibration. The PML calibration has been applied to the data for the sake of consistency throughout the project. However, it should be borne in mind that the result may represent an underestimate of the actual suspended load.

References

Fofonoff, N.P. and Millard Jr., R.C. (1983). Algorithms for computation of fundamental properties of seawater. UNESCO Technical Papers in Marine Science 44.

Morris, A.W., Howland, R.J.M., and Bale, A.J. (1978). A filtration unit for use with continuous autoanalytical systems applied to highly turbid waters. Est. Coast. Mar. Sci. 6, 105-109.

van den Berg, C.M.G. and Achterberg, E.P. (1994). Automated in-line sampling of trace elements with voltammetric detection. TrAC. 13, 348-352.

CH119_a Sea surface Hydrography, Meteorology and Navigation Series

Instrumentation

Seawater was continuously pumped from the hull of the ship (at a depth of about 4m). This is known as the ship's non-toxic supply. The thermosalinograph was fed through a small (100-litre) header tank. A large plastic tank on the starboard deck was fed directly from the non-toxic manifold and contained the transmissometer and fluorometer. Baffles in the tank ensured that a continuous flow was maintained over the instruments. A selflogging YSI dissolved oxygen probe was also placed in this tank. However, this instrument flooded due to a defective 'O' ring seal and therefore failed to return any useful data.

The nutrient autoanalyser was fed from plastic tubing connected to taps on the non-toxic supply. The electrochemical metal analysers were fed from an all-plastic supply fed from an intake on the port echo sounder fish at approximately 2m depth and driven by a perisaltic pump.

The Endeco dissolved oxygen system electrodes were placed in a Perspex cell (approx. 1 litre volume) supplied from the general non-toxic supply via a constant head device at 2 litres/minute.

Calibration samples were either taken from the non-toxic tap on the wet laboratory sink or the thermosalinograph outlet.

Data Acquisition

For most parameters, data logging and initial processing was handled by the RVS ABC system. The Level A sampling microcomputer digitised an input voltage, applied a time stamp and transferred the data via the Level B disk buffer onto the Level C where the data records were assembled into files. Note that the autoanalyser was included in this arrangement by logging voltages supplied to the instrument chart recorder.

Exceptions to this rule were the electrochemical metal analysers and Endeco dissolved oxygen system, which were logged by dedicated PCs. Sampling rates varied from 10 seconds to 10 minutes. Careful attention was paid to the synchronisation of the PC and logger clocks to the master clock used by the ABC system.

The Level C included a suite of calibration software, which was used to apply initial calibrations to convert raw ADC counts into engineering units. At the end of the cruise the Level C disk base was transferred to BODC for further processing. PC logged data were supplied to BODC on floppy disk for merging with the data from the ship's system.


Project Information

LOIS River-Atmosphere-Coast Study (LOIS - RACS)

Introduction

The Land-Ocean Interaction Study (LOIS) was a NERC research programme designed to study processes in the coastal zone. The Rivers, Atmosphere and Coasts Study (RACS) was a major component of LOIS that looked at land-sea interactions in the coastal zone and the major exchanges (physical, chemical and biological) between rivers and estuaries and the atmosphere. The study focused on the east coast of the UK from the Wash to the Tweed.

RACS included several sub-components

  • BIOTA - A study of salt marshes of the Humber and Wash
  • RACS (A) - An atmospheric chemistry study looking at air mass changes from the Wash into East Anglia
  • RACS (C) - A study of the estuaries, coasts and coastal waters between Great Yarmouth and Berwick upon Tweed.
    1. The coastal oceangraphic survey
    2. The Humber estuarine study
    3. The Tweed estuarine study
    4. The Holderness experiment
  • RACS (R) - A study of rivers that drain into the North Sea

RACS (A) was coordinated by the University of East Anglia and RACS (C) by the Plymouth Marine Laboratory.

RACS (A)

The bulk of the RACS (A) data set was collected during two field campaigns in the winter (October/November) of 1994 and the summer (May/June) of 1995. During these campaigns data were collected continuously from the University of East Anglia Atmospheric Observatory at Weybourne on the north Norfolk coast. An instrumented vessel was stationed offshore to provide a second sampling site to allow changes in a given air mass to be monitored. The Imperial College Jetstream research aircraft made one flight during each campaign to provide a link between the two surface stations. The Jetstream made four additional flights in 1996 and 1997.

RACS (C)

The coastal oceanographic survey

The coastal oceanographic data set was collected during a series of 17 RRS Challenger cruise legs. Most cruises covered two survey grids. One from Great Yarmouth to the Humber designed around the distribution of the sandbanks and a second simple zig-zag grid from the Humber to Berwick on Tweed. A large number of anchor stations, usually over one or two tidal cycles, were worked in the area of the Humber mouth or the Holderness coast.

The Humber estuarine study

The Humber estuarine data set was collected during a series of 33 campaigns on the Environment Agency vessels Sea Vigil and Water Guardian in the Humber, Trent and Ouse river systems at approximately monthly intervals between June 1993 and December 1996. Each campaign consisted of two or three one-day cruises. The tracks covered the estuary from the tidal limits of both Trent and Ouse to Spurn Point. Instrumental and sample data are available from a series of fixed stations that were sampled during every campaign.

The Tweed estuarine study

The Tweed estuarine data set was collected during a series of 13 campaigns using RV Tamaris in association with a rigid inflatable vessel at approximately monthly intervals between July 1996 and July 1997. Each campaign covered the tidal reaches of the River Tweed.

The Holderness experiment

The Holderness Experiment was designed to monitor the process of sediment transport along the Holderness coastline. It consisted of three moored instrument deployments during the winters of 1993-1994, 1994-1995 and 1995-1996. Mooring platforms were deployed at eight stations along two lines off the Holderness coast. A northerly and a southerly line of four stations each were used (N1 - N4 and S1 to S4) with the lowest numbers being inshore. Both lines were approximately perpendicular to the coast, although the S4 station lay to the south of the S line, off Spurn Head.


Data Activity or Cruise Information

Cruise

Cruise Name CH119A
Departure Date 1995-06-01
Arrival Date 1995-06-12
Principal Scientist(s)Reg Uncles (Plymouth Marine Laboratory), Roy K Lowry (British Oceanographic Data Centre Bidston)
Ship RRS Challenger

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
B nominal value
Q value below limit of quantification