Metadata Report for BODC Series Reference Number 1359887


Metadata Summary

Data Description

Data Category Surface temp/sal
Instrument Type
NameCategories
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 Andy Rees
Originating Organization Plymouth Marine Laboratory
Processing Status banked
Project(s) Atlantic Meridional Transect Phase2(AMT)
 

Data Identifiers

Originator's Identifier AMT15_PRODQXF2_SURF
BODC Series Reference 1359887
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2004-09-17 13:08
End Time (yyyy-mm-dd hh:mm) 2004-10-27 17:51
Nominal Cycle Interval 60.0 seconds
 

Spatial Co-ordinates

Start Latitude 50.74630 N ( 50° 44.8' N )
End Latitude 35.35340 S ( 35° 21.2' S )
Start Longitude 1.40260 W ( 1° 24.2' W )
End Longitude 16.46460 E ( 16° 27.9' E )
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
CPHLUT01 1 Milligrams per cubic metre chl-a_water_NTTFfluor_sampcal Concentration of chlorophyll-a {chl-a CAS 479-61-8} per unit volume of the water body [particulate >unknown phase] by through-flow fluorometer plumbed into non-toxic supply and calibration against sample data
FVLTZZ01 1 Volts FlVolt Instrument output (voltage) by in-situ 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
TEMPSG01 1 Degrees Celsius CalTSGTmp Temperature of the water body by thermosalinograph and verification against independent measurements
 

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 AMT15 (D284) - Continuous Underway Hydrographic Data Quality Report

Data Quality Report

There are no known quality issues with the data.


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.

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 AMT15 (D284) - Continuous Underway Hydrographic Instrumentation Document

Instrumentation

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

RRS Discovery AMT15 (D284) - Continuous Underway Hydrographic Processing Document

Originator's Data Processing

RRS Discovery is fitted with a central data logging system known as the ABC system. All available data streams from the ABC were collected. Most data streams have a one second sample interval with the exception of surfmet (30s) and ea500d1 (ping interval). ASCII listings were produced for all ABC system data streams.

The data archive was distributed to the PSO and BODC on DVD with compression of some datasets, notably processed CTD data and all the ABC data. A backup copy of the DVD was left onboard the ship, also one backup was taken back to UKORS. Approximately eight Gigabytes of data were acquired including processed data.

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 60 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

Salinity

Salinity data from the thermosalinograph have been compared with calibrated surface CTD data to a depth of 20 m. This is usually done to a depth of 5 m, however, the CTD data down to ~15 m depth show a lot of variability. Different averaging depths (5 m, 10 m, 15 m and 20 m) were investigated and compared to the underway data. There was no significant difference in the long-wavelength salinity trend when averaging over the different depths compared to the underway data. Averaging to 20 m of CTD salinity data provided the best calibration and was therefore used. The underway data were averaged over the period of CTD deployments and standard deviations were used to check the quality of the data. The 79 samples showed the following relationship, which has been used to produce a calibrated salinity channel (PSALSG01).

PSALSG01 = 0.95856 * PSALSU01 + 1.39300 (BODC calibration 4175)

Temperature

TSG temperature was checked against the CTD temperature measurements averaged over the upper 5 m, 10 m, 15 m and 20 m of the water column. It was found that the best calibration was obtained with CTD measurements averaged over 10 m. Only CTD data points and underway records with a standard deviation lower than 0.01 deg.C over the duration of the cast were considered. A regression analysis was run on the data and, based on a total of 93 paired samples, the following calibration was derived.

TEMPSG01 = 1.00335 * TEMPSU01 - 0.14838 (BODC calibration 4177)

Chlorophyll

The fluorometer channel was calibrated by comparing the uncalibrated fluorometer output with chlorophyll concentration values extracted from samples collected from the ship's non-toxic water supply (N=88). Four different groups were identified, corresponding to the European Shelf, Northern Gyre, Equatorial Upwelling and the Southern Gyre and these were calibrated separately.

Group 1 (18/09/2004 to 27/09/2004, BODC calibration 4194):

CPHLUT01 = 0.996 * FVLTZZ01 - 0.065, R2=0.69

Group 2 (27/09/2004 to 02/10/2004, BODC calibration 4195):

CPHLUT01 = 4.035 * FVLTZZ01 - 0.456, R2=0.81

Group 3 (02/10/2004 to 23/10/2004, BODC calibration 4196):

CPHLUT01 = 0.485 * FVLTZZ01 - 0.041, R2=0.66

Group 4 (23/10/2004 to 27/10/2004, BODC calibration 4197):

CPHLUT01 = 0.849 * FVLTZZ01 - 0.077, R2=0.72

Residuals (extracted chlorophyll from the non-toxic minus calibrated fluorometer) follow a normal distribution and range between -0.10 and 0.20 mg chl m -3 for chlorophyll concentrations ranging from 0.02 to 0.51 mg Chla m -3 . The largest variations occur over upwelling regions on the European shelf, North West Africa and near South Africa when extracted chlorophyll highs are not mirrored to the same extent in the fluorometer readings. Using four separate regressions provides a better fit to the extracted chlorophyll than using a single regression for the whole cruise. In fact, the sum of the squares of the residuals is 6 times lower when using 4 calibrations than when using a single calibration. However, this procedure has resulted in a small jump in CPHLUT01 on the 23/10/2004 where chlorophyll concentrations change rapidly and data from that date should be used cautiously.


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 D284 (AMT15)
Departure Date 2004-09-17
Arrival Date 2004-10-29
Principal Scientist(s)Andrew Rees (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