Metadata Report for BODC Series Reference Number 1359918


Metadata Summary

Data Description

Data Category Surface temp/sal
Instrument Type
NameCategories
SeaTech transmissometer  transmissometers
WETLabs WETStar fluorometer  fluorometers
Falmouth Scientific Instruments ocean temperature module  water temperature sensor
Falmouth Scientific Instruments ocean conductivity module  salinity sensor
Trimble 4000DS Global Positioning System receiver  Differential Global Positioning System receivers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Tony Bale
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Project(s) Atlantic Meridional Transect Phase2(AMT)
 

Data Identifiers

Originator's Identifier AMT16_PRODQXF_SURF
BODC Series Reference 1359918
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2005-05-20 12:00
End Time (yyyy-mm-dd hh:mm) 2005-06-28 13:00
Nominal Cycle Interval 30.0 seconds
 

Spatial Co-ordinates

Start Latitude 33.88830 S ( 33° 53.3' S )
End Latitude 48.52950 N ( 48° 31.8' N )
Start Longitude 18.45360 E ( 18° 27.2' E )
End Longitude 8.56200 W ( 8° 33.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 5.0 m
Maximum Sensor Depth 5.0 m
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor Depth Datum Approximate - Depth is only approximate
Sea Floor Depth Datum -
 

Parameters

BODC CODE Rank Units Short Title Title
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
FVLTWS01 1 Volts WsVolt Instrument output (voltage) by linear-response chlorophyll fluorometer
PSALSG01 1 Dimensionless P_sal_TSG_calib Practical salinity of the water body by thermosalinograph and computation using UNESCO 1983 algorithm and calibration against independent measurements
TEMPHG01 1 Degrees Celsius CalTSGHullTmp Temperature of the water body by thermosalinograph hull sensor and verification against independent measurements
TVLTDR01 1 Volts TrVoltRed25 Instrument output (voltage) by 25cm path length red light transmissometer
 

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

RRS Discovery AMT16 (D294) - Continuous Underway Hydrographic Data Quality Report

The quality of the fluorometer and transmissometer records was affected by the blockage in the flow loop containing these sensors for 14 days in the middle of the cruise (30th May to 13th June, 2005). These periods were flagged as suspect for both instruments during screening.

Although there were extracted chlorophyll data from samples taken from the non-toxic supply, the decision was taken not to apply calibrations to the highly variable fluorometer data at either end of the cruise track; instead the extracted chlorophyll dataset should be used for surface chlorophyll data along the cruise track.


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

WET Labs WETStar Fluorometers

WET Labs WETStar fluorometers are miniature flow-through fluorometers, designed to measure relative concentrations of chlorophyll, CDOM, uranine, rhodamineWT dye, or phycoerythrin pigment in a sample of water. The sample is pumped through a quartz tube, and excited by a light source tuned to the fluorescence characteristics of the object substance. A photodiode detector measures the portion of the excitation energy that is emitted as fluorescence.

Specifications

By model:

  Chlorophyll WETStar CDOM WETStar Uranine WETStar Rhodamine WETStar Phycoerythrin WETStar
Excitation wavelength 460 nm 370 nm 485 nm 470 nm 525 nm
Emission wavelength 695 nm 460 nm 530 nm 590 nm 575 nm
Sensitivity 0.03 µg l -1 0.100 ppb QSD 1 µg l -1 - -
Range 0.03-75 µg l -1 0-100 ppb; 0-250 ppb 0-4000 µg l -1 - -

All models:

Temperature range 0-30°C
Depth rating 600 m
Response time 0.17 s analogue; 0.125 s digital
Output 0-5 VDC analogue; 0-4095 counts digital

Further details can be found in the manufacturer's specification sheet , and in the instrument manual .

Trimble 4000DS Global Positioning System receiver

The Trimble 4000DS Differential Surveyor is similar to the 4000RS (a Maxwell-based receiver that is oriented toward precision positioning applications. It is intended for use as a DGPS base station, generating RTCM-104 corrections). The 4000Ds can apply RTCM-104 corrections to the satellite data it receives in order to generate accurate position fixes in real time.

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

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 .

Falmouth Scientific Inc. Ocean Sensor Modules

FSI's individual sensor modules include an Ocean Conductivity Module (OCM), Ocean Temperature Module (OTM) and Ocean Pressure Module (OPM). All three use a low power micro-controller to collect, scale and transmit real-time data via RS-232 or RS-485.

Parameter OCM Conductivity OTM Temperature OPM Pressure
Range 0 - 7.0 S/m(0 - 70 mS/cm) -2 to 32 °C User Specified:0-200 dBar0-1000 dBar0-2000 dBar0-3000 dBar0-7000 dBar
Accuracy -0.0003* S/m(-0.003 mS/cm) -0.003 °C* -0.03% full scale*
Stability /month -0.00005 S/m(-0.0005 mS/cm) -0.0005 °C -0.002% full scale
Resolution 0.00001 S/m(-0.0001 mS/cm) 0.0001 °C 0.0004% full scale
Response at 1 m/s flow 50 msec 150 msec 25 msec
Sensor Type Inductive cell Platinum thermometer Strain gauge

* Higher accuracy available

For further details, see the manufacturer's specification sheet .

RRS Discovery AMT16 (D294) - Continuous Underway Hydrographic Instrumentation Document

Manufacturer Model Main Function Serial Number Comments
Trimble 4000DS Position (Latitude and Longitude) - -
WETLABS W3S Fluorometer 247 -
FSI OTM Temperature 1360 -
FSI OCM Salinity 1376 -
Seatech - Transmissometer - -

RRS Discovery AMT16 (D294) - Continuous Underway Hydrographic Processing Document

Originator's Data Processing

SurfMet, the UKORS surface water and meteorological suite of instrumentation was run for the duration of the cruise. The SurfMet system was controlled via a LabView program running on a desktop PC and logged the data at 30 second intervals to the ship's central data logging (ABC) System in the RVS format file 'surftmp'. The system was inadvertently stopped from logging mid-cruise resulting in a loss of around 4 hours of data. The temperature and conductivity data were used to calculate the surface salinity and were logged in the RVS file 'protsg'.

The transmissometer and fluorometer flow loop was stopped occasionally to clean the transmissometer lenses and take air and blank readings. After one cleaning event this loop appears to have stalled, even though the flow meter indicated flow. Hence there is bad data logged by the transmissometer and fluorometer between Julian Days 150 and 164 (30th May to 13th June, 2005).

BODC Data Processing

Reformatting

Data from the full-resolution RVS files were transferred to BODC's NetCDF format (QXF) under the BODC Underway Data System (BUDS). This transfer involved reducing the data to 30 second intervals using averaging. Directional data were reduced by averaging using a unit circle.

Screening

Each data channel was inspected on a graphics workstation and any spikes or periods of dubious data were flagged. The power of the workstation software was used to carry out comparative screening checks between channels by overlaying data channels. A map of the cruise track was simultaneously displayed in order to take account of the oceanographic context.

Data processing, correction and calibration

The data were loaded from the RVS files 'protsg' and 'surftmp'.

The raw voltage channels for the fluorometer and transmissometer were transferred and converted from mV to V (conversion factor = x0.001). Data were flagged for periods where the non-toxic supply was turned off and for spikes associated with cleaning operations.

Salinity

Salinity data from the thermosalinograph have been compared with calibrated surface CTD data to a depth of 7 db and samples collected from the underway system and analysed with a bench salinometer. The analysis showed that there was a drift in the salinity measurement with time during the cruise. This was corrected using a linear offset against time.

The root mean square (RMS) error for the calibration dataset (n = 102) was calculated between the bench salinometer data and both the uncalibrated TSG and calibrated salinity.

  Uncalibrated salinity Calibrated Salinity
Max Offset 0.031 0.028
Min Offset -0.219 -0.048
RMS 0.159 0.009

The decrease in the RMS error indicates the calibration improves the match between the CTD and sample salinities and the TSG sensor. Once the calibration was applied the average offset was-9.3x10 -5 , with SD 0.009.

Start End Calibration Type Offset Value N R 2 (%) BODC ICALRF
21/05/2005 03:45:00 04/06/2005 03:32:00 Linear offset with time

Start = -0.1689

End = -0.1996

30 61.13 6381
04/06/2005 03:32:01 20/06/2005 00:15:00 Linear offset with time

Start = -0.1996

End = -0.1363

51 91.31 6382
20/06/2005 00:15:01 28/06/2005 13:00:00 Linear offset with time

Start = -0.1093

End = +0.0405

24 86.30 6383
Temperature

Hull mounted temperature sensor data was checked against the CTD temperature measurements averaged over the upper 7 db of the water column. Only CTD data points and underway records with a standard deviation lower than 0.01 °C were considered. The offset was calculated from CTD temp - hull sensor temp, which was then plotted against both time and CTD temperature. There was a significant regression with the offset against both time and CTD temp. Since the regression against time explained a greater proportion of the variance a linear offset was determined against cruise time and values determined for the start and end of the cruise. The BODC calibration system then generated the offset to be added for each time interval in between.

The root mean square (RMS) error for the calibration dataset (n = 46) was calculated between the CTD sensor temperature and both the uncalibrated and calibrated hull sensor temperature.

  Uncalibrated salinity Calibrated Salinity
Max Offset -0.018 0.021
Min Offset -0.098 -0.049
RMS 0.048 0.014

The decrease in the RMS error indicates the calibration improves the match between the CTD temperature and the hull temperature sensor. Once the calibration was applied the average offset was-2.2x10 -5 °C, with SD 0.014 oC.

Start End Calibration Type Offset Value N R 2 (%) BODC ICALRF
21/05/2005 03:45:00 28/06/2005 13:00:00 Linear offset with time

Start = -0.0176

End = -0.0718

46 51.88 6405
Chlorophyll

Calibration of the fluorometer channel was attempted by comparing the raw fluorometer output voltage with chlorophyll concentration values extracted from samples collected from the ship's non-toxic water supply (n = 138). However the loss of 14 days fluorometer data reduced the calibration samples (n = 86) and reduced coverage during the middle of the cruise. Therefore the fluorometer data have not been calibrated and BODC recommends the use of the underway sampled extracted chlorophyll dataset, which provides good coverage along the cruise track.

Transmissometer

There was no record available of the transmissometer serial number and so no calibration sheet can be supplied for this instrument. Despite air and dark readings being taken during the cruise a calibration cannot be reliably applied and the data therefore remain as a voltage.


Project Information

The Atlantic Meridional Transect - Phase 2 (2002-2006)

Who was involved in the project?

The Atlantic Meridional Transect Phase 2 was designed by and implemented by a number of UK research centres and universities. The programme was hosted by Plymouth Marine Laboratory in collaboration with the National Oceanography Centre, Southampton. The universities involved were:

What was the project about?

AMT began in 1995, with scientific aims to assess mesoscale to basin scale phytoplankton processes, the functional interpretation of bio-optical signatures and the seasonal, regional and latitudinal variations in mesozooplankton dynamics. In 2002, when the programme restarted, the scientific aims were broadened to address a suite of cross-disciplinary questions concerning ocean plankton ecology and biogeochemistry and the links to atmospheric processes.

The objectives included the determination of:

The data were collected with the aim of being distributed for use in the development of models to describe the interactions between the global climate system and ocean biogeochemistry.

When was the project active?

The second phase of funding allowed the project to continue for the period 2002 to 2006 and consisted of six research cruises. The first phase of the AMT programme ran from 1995 to 2000.

Brief summary of the project fieldwork/data

The fieldwork on the first three cruises was carried out along transects from the UK to the Falkland Islands in September and from the Falkland Islands to the UK in April. The last three cruises followed a cruise track between the UK and South Africa, only deviating from the traditional transect in the southern hemisphere. During this phase the research cruises sampled further into the centre of the North and South Atlantic Ocean and also along the north-west coast of Africa where upwelled nutrient rich water is known to provide a significant source of climatically important gases.

Who funded the project?

Natural Environment Research Council (NERC)


Data Activity or Cruise Information

Cruise

Cruise Name D294 (AMT16)
Departure Date 2005-05-20
Arrival Date 2005-06-29
Principal Scientist(s)Tony Bale (Plymouth Marine Laboratory)
Ship RRS Discovery

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