Metadata Report for BODC Series Reference Number 1762248


Metadata Summary

Data Description

Data Category Surface temp/sal
Instrument Type
NameCategories
WETLabs WETStar fluorometer  fluorometers
WETLabs C-Star transmissometer  transmissometers
Sea-Bird SBE 45 MicroTSG thermosalinograph  thermosalinographs; water temperature sensor; salinity sensor
Sea-Bird SBE 38 thermometer  water temperature sensor
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Mr Martin Bridger
Originating Organization National Marine Facilities Sea Systems
Processing Status banked
Project(s) Oceans 2025 Theme 10 SO1:AMT
 

Data Identifiers

Originator's Identifier D371_PRODQXF_SURF
BODC Series Reference 1762248
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2011-09-29 08:19
End Time (yyyy-mm-dd hh:mm) 2011-11-11 17:59
Nominal Cycle Interval 60.0 seconds
 

Spatial Co-ordinates

Southernmost Latitude 52.05483 S ( 52° 3.3' S )
Northernmost Latitude 51.50700 N ( 51° 30.4' N )
Westernmost Longitude 67.10200 W ( 67° 6.1' W )
Easternmost Longitude 2.70400 W ( 2° 42.2' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth 6.0 m
Maximum Sensor Depth 6.0 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
ATTNDR01 1 per metre Attn_Red_25cm Attenuation (red light wavelength) per unit length of the water body by 25cm path length red light transmissometer
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
FVLTWS01 1 Volts WsVolt Instrument output (voltage) by linear-response chlorophyll fluorometer
POPTDR01 1 Percent Trans_Red_25cm Transmittance (red light wavelength) per 25cm of the water body by 25cm path length red light transmissometer
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
TMESSG01 1 Degrees Celsius TSG_Meas_Temp Temperature of conductivity measurement by thermosalinograph
 

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

Attenuance and transmittance

There whole of the transmittance and attenuance channels have been flagged. This is due to highly noisy data in both channels. Users should use caution when interpreting the transmissometer data.

AMT RRS Discovery Cruise D371 AMT21 Surface Hydrography Data Quality Document

The underway log sheets were used as a guide to the times when the non-toxic flow was switched off, dropped low or was adjusted during the cruise. Where there was noise in the channel at these times the data were flagged suspect. If there was no noise or spiking the data remain unflagged.

The sample calibrations applied to the TSG salinity, hull sensor temperature and fluorometer channels appear reasonable and did not produce suspect data in the calibrated channels. The calibrated fluorometer data exhibit large amounts of variability towards the end of the cruise in the southern Atlantic Ocean. The calibration in this area is not as closely matched to the sample data for this reason and users should keep this in mind when using the sample calibrated fluorometer data.

Attenuance and transmittance

There are some periods of noise within the transmissometer data, which may be the result of bubbles accumulating at the lens. There are other periods when there are steps in the data. Users should therefore apply caution when interpreting the transmissometer 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

SeaBird Digital Oceanographic Thermometer SBE38

The SBE38 is an ultra-stable thermistor that can be integrated as a remote temperature sensor with an SBE21 Thermosalinograph or an SBE 45 Micro TSG, or as a secondary temperature sensor with an SBE 16 plus, 16plus-IM, 16plus V2, 16plus-IM V2 or 19plus V2 SEACAT CTD.

Temperature is determined by applying an AC excitation to reference resistances and an ultra-stable aged thermistor. The reference resistor is a hermetically sealed VISHAY. AC excitation and ratiometric comparison using a common processing channel removes measurement errors due to parasitic thermocouples, offset voltages, leakage currents and gain errors.

The SBE38 can operate in polled sampling, where it takes one sample and transmits the data, or in continuous sampling.

Specifications

Depth rating up to 10500 m
Temperature range -5 to 35°C
Initial accuracy ± 0.001°C
Resolution 0.00025°C
Stability 0.001°C in 6 months
Response time 500 ms
Self-heating error < 200 µK

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

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 .

WETLabs C-Star transmissometer

This instrument is designed to measure beam transmittance by submersion or with an optional flow tube for pumped applications. It can be used in profiles, moorings or as part of an underway system.

Two models are available, a 25 cm pathlength, which can be built in aluminum or co-polymer, and a 10 cm pathlength with a plastic housing. Both have an analog output, but a digital model is also available.

This instrument has been updated to provide a high resolution RS232 data output, while maintaining the same design and characteristics.

Specifications

Pathlength 10 or 25 cm
Wavelength 370, 470, 530 or 660 nm
Bandwidth

~ 20 nm for wavelengths of 470, 530 and 660 nm

~ 10 to 12 nm for a wavelength of 370 nm

Temperature error 0.02 % full scale °C -1
Temperature range 0 to 30°C
Rated depth

600 m (plastic housing)

6000 m (aluminum housing)

Further details are available in the manufacturer's specification sheet or user guide .

AMT RRS Discovery Cruise D371 AMT21 Surface Hydrography Instrument Description Document

Sensor Serial number Last calibration date
Sea-Bird SBE38 0491 2011-06-27
Sea-Bird SBE45 229 2011-04-13
Wetlabs C-Star CST-1131PR 2011-03-24
Wetlabs WetStar WS3S-248 2010-12-15

SeaBird MicroTSG Thermosalinograph SBE 45

The SBE45 MicroTSG is an externally powered instrument designed for shipboard measurement of temperature and conductivity of pumped near-surface water samples. The instrument can also compute salinity and sound velocity internally.

The MicroTSG comprises a platinum-electrode glass conductivity cell and a stable, pressure-protected thermistor temperature sensor. It also contains an RS-232 port for appending the output of a remote temperature sensor, allowing for direct measurement of sea surface temperature.

The instrument can operate in Polled, Autonomous and Serial Line Sync sampling modes:

Specifications

  Conductivity Temperature Salinity
Range 0 to 7 Sm -1 -5 to 35°C  
Initial accuracy 0.0003 Sm -1 0.002°C 0.005 (typical)
Resolution 0.00001 Sm -1 0.0001°C 0.0002 (typical)
Typical stability (per month) 0.0003 Sm -1 0.0002°C 0.003 (typical)

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

AMT RRS Discovery Cruise D371 AMT21 Surface Hydrography Processing Procedures Document

Originator's Data Processing

During the cruise there was a dual logging system in place on the RRS Discovery. Data from the various instruments are logged to the RVS Level-C system and also as NetCDF (binary) through the Ifremer Techsas data logging system. The following instruments were logged during the cruise:
1) Wetlabs C-star 25 cm pathlength transmissometer (logged to RVS format in surfmet)
2) Wetlabs WetStar fluorometer (logged to RVS format in surfmet)
3) Seabird SBE38 Temperature sensor (logged to RVS format in seabird)
4) Seabird SBE45 MicroTSG (logged to RVS format in seabird)

Filename Data type Start Calendar Day Start Time Finish Calendar Day Finish Time Interval
seabirdX RVS Level-C raw 2011-09-30 08:02:38 2011-10-02 09:00:06 1 sec
seabird RVS Level-C raw 2011-10-01 09:34:09 2011-11-09 10:26:53 1 sec
surfmetX RVS Level-C raw 2011-09-28 08:06:49 2011-10-02 09:00:00 1 sec
surfmet RVS Level-C raw 2011-10-01 09:34:08 2011-11-11 18:03:53 1 sec

BODC Data Processing

The last ~20 days TECHSAS files (except for the TSG data) were not saved to the post-cruise archive. TECHSAS files from 23 Oct 2011 to 13 Nov 2011 were missing. The RVS level-C files were confirmed complete by the originator. Since the TECHSAS file record for the cruise was incomplete the RVS Level-C files were chosen for transfer to the BODC underway file.

The surfmetX/surfmet and seabirdX/seabird data were transferred. A description of the channels present in the files, units, whether they were transferred, BODC parameter code and units, and if a unit conversion was applied during the transfer are detailed in the table below:

surfmet Channels Description Units BODC Parameter Code Units Conversion Factor
temp_h TSG housing temperature - not for transfer - loaded from seabird file with salinity - -
temp_m Remote temperature at non-toxic inlet - not for transfer - loaded from seabird file with salinity - -
cond TSG conductivity - not for transfer - loaded from seabird file with salinity - -
fluo Raw fluorometer voltage V FVLTWS01 V *1
trans Raw transmissometer voltage V TVLTDR01 V *1
seabird Channels Description Units BODC Parameter Code Units Conversion Factor
temp_h TSG housing temperature Degrees Celsius TMESSG01 Degrees Celsius *1
cond TSG conductivity S m -1 CNDCSG01 S m -1 *1
salin Salinity PSU PSALSU01 dimensionless *1
sndspeed Velocity of sound in water m s -1 SVELSG01 m s -1 *1
temp_r Remote temperature at non-toxic inlet Degrees Celsius TEMPHU01 Degrees Celsius *1

* temp_h, cond, temp_m not loaded from surfmet as where present these data are identical to the seabird file data but maybe delayed in time in the surfmet file (details on page 5 of the D371 Computing and Ship Systems Report)

Calibrations

Transmissometer - conversion from voltage using manufacturer's calibrations

The manufacturer's calibrations from the sheets supplied by NMF-SS have been applied through the BODC Calibration database.

BODC ICALRF 6723 POPTDR01 = 100 * (TVLTDR01 -0.059) / (4.661 - 0.059) = 21.7297 * TVLTDR01 - 1.2821

BODC ICALRF 6724 ATTNDR01 = -(1/0.25) * ln (POPTDR01 * 0.01)

Temperature

The hull temperature sensor data were calibrated against the CTD temperature sensors during the cruise. The data from the hull sensor at the CTD start time were compared with the temperature from the CTD at 7 decibars. The temperature offsets (CTD - Hull) were plotted against date/time and CTD sensor temperature and outliers identified. The relationships in the offset between sensors were then compared to the date/time and the CTD sensor temperature in separate linear regressions. There was no significant relationship with CTD sensor temperature (R 2 =-0.01; n = 60; F = 0.376; p = 0.542). There was a significant regression of offset with date/time (R 2 = 0.08; n = 60; F = 5.82; p = 0.019).

Applying the significant regression equation the offset was generated at the date/time when the non-toxic underway system was switched on (30/09/2011 08:00 offset = 0.0036) and when switched off at the end of the cruise (09/11/2011 14:00 offset = -0.0077). The offset was applied for the period in between by linear interpolation of these offsets through the BODC BUDS calibration routine (BODC ICALRF 6726).

Salinity

The SBE45 salinity data were calibrated against bench salinometer data from samples collected from the underway system during the cruise. The data from the SBE45 TSG at the discrete sampling times were compared with the bench salinometer measurements. The salinity offsets (bench - TSG) were plotted against date/time and bench salinity and outliers identified. The relationships in the offset between TSG and bench salinometer were then compared to the date/time and the bench salinity in separate linear regressions. There was a significant relationship of offset with date/time (R 2 = 0.43; n = 168; F = 127.3; p < 0.001) and also bench salinity (R 2 = 0.18; n = 168; F = 38.0; p < 0.001).

Applying the significant equation from the date/time regression with the higher R 2 , the offset was generated at the date/time when the non-toxic underway system was switched on (30/09/2011 08:00 offset = -0.0151) and when switched off at the end of the cruise (09/11/2011 14:00 offset = 0.0017). The offset was applied for the period in between by linear interpolation of these offsets through the BODC BUDS calibration routine (BODC ICALRF 6729).

Fluorescence

The fluorometer voltage data were calibrated against extracted chlorophyll-a data from samples collected from the underway system during the cruise. Samples of seawater collected and extracted chlorophyll-a measurements made following Welschmeyer (1994). Each sample of 250 ml was filtered through a 47 mm 0.2 µm polycarbonate filter. The filters were then placed in a vial with 10 ml 90% acetone and left in a freezer for 24 hours. The samples were then analysed on a pre-calibrated Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted. The bench fluorometer calibration was checked against dilutions of pure chlorophyll stock during the cruise and no modifications to the calibration were necessary. The raw voltage data from the fluorometer at the discrete sampling times were compared with the extracted chlorophyll-a measurements. The offsets (extracted chl-a - voltage) were plotted against date/time and extracted chlorophyll-a and outliers identified. Based on a preliminary calibration against extracted chl-a, which over stated the chlorophyll concentrations at the start of the cruise; it was decided to split the dataset for calibration. The calibration was split at the fluorometer cleaning event at 03/10/2011 13:04 in to two sections (1 and 2). The linear regression between the offset and extracted chlorophyll-a for each section were calculated. There was a significant relationship for both section 1 (R 2 = 0.16; n = 174; F = 33.5; p < 0.001) and section 2 (R 2 = 0.92; n = 174; F = 1880.7; p < 0.001).

Applying the equation from the extracted chlorophyll-a regression for each section, the calibrated fluorescence channel data were generated through the BODC BUDS calibration routine.

Section 1: 30/09/2011 08:00 to 03/10/2011 13:04 BODC ICALRF 6727 CPHLUT01 = 1.5771 * FVLTWS01 - 0.1038

Section 2: 03/10/2011 13:04 to 09/11/2011 14:00 BODC ICALRF 6728 CPHLUT01 = 3.3824 * FVLTWS01 - 0.1286

References

Welschmeyer N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnology and Oceanography, 39:1985-1992.


Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)

The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.

The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:

The specific objectives are:

The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).

More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/


Data Activity or Cruise Information

Cruise

Cruise Name D371 (AMT21)
Departure Date 2011-09-29
Arrival Date 2011-11-13
Principal Scientist(s)Glen A Tarran (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