Metadata Report for BODC Series Reference Number 1044363


Metadata Summary

Data Description

Data Category PAR radiance and irradiance
Instrument Type
NameCategories
Satlantic Micro Surface Acquisition System (MicroSAS) radiometer  radiometers
Instrument Mounting research vessel
Originating Country United States
Originator Dr Barney Balch
Originating Organization Bigelow Laboratory for Ocean Sciences
Processing Status banked
Project(s) Atlantic Meridional Transect Phase2(AMT)
 

Data Identifiers

Originator's Identifier AMT17.XLS
BODC Series Reference 1044363
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2005-10-16 19:47
End Time (yyyy-mm-dd hh:mm) 2005-11-26 04:34
Nominal Cycle Interval 440.0 seconds
 

Spatial Co-ordinates

Start Latitude 51.72740 N ( 51° 43.6' N )
End Latitude 35.53330 S ( 35° 32.0' S )
Start Longitude 6.83060 W ( 6° 49.8' W )
End Longitude 18.61050 E ( 18° 36.6' E )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth -17.5 m
Maximum Sensor Depth -7.0 m
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution Scattered at fixed depths - The sensors are scattered with respect to depth but each remains effectively at the same depth 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
LAMBIN01 0 Nanometres Wavelength Wavelength of electromagnetic radiation measurement
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)
ACYCAA01 1 Dimensionless Record_No Sequence number
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
IARAZM01 1 Degrees RelAz Instrument angle relative to solar plane {azimuth}
CSLRCCR1 2 Watts per square metre per nanometre Es_lambda Downwelling vector irradiance as energy (unspecified single wavelength) in the atmosphere by cosine-collector radiometer
NRWLRCR1 2 Watts per square metre per nanometre per steradian Nlw_2D Normalised water-leaving radiance (unspecified single wavelength) from the water body by cosine-collector radiometer
RWLRCCR1 2 Watts per square metre per nanometre per steradian Lw_2D Water-leaving radiance (unspecified single wavelength) from the water body by cosine-collector radiometer
SKYIRR01 2 Watts per square metre per nanometre per steradian Lsky_lambda Sky radiance as energy (unspecified single wavelength) in the atmosphere by cosine-collector radiometer
TTWTIR01 2 Watts per square metre per nanometre per steradian Lsfc_lambda Total water radiance (unspecified single wavelength) from the water body by radiometer
 

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

Data Quality Report

As no spurious data were identified during screening, using the in-house visualisation software, no additional BODC quality control flags were applied to the data. However, the quality of the data is reduced at low solar elevations, before approximately 10:00 hours and after 14:00 hours local time. No data were obtained during the night, only during daylight hours.


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

Instrumentation

Optics data were collected with a Satlantic SeaWiFS Aircraft Simulator ( MicroSAS ) .

Satlantic Surface Acquisition Systems (MicroSAS and HyperSAS)

The Satlantic Surface Acquisition System (SAS) is designed for above-water measurements of ocean colour using multispectral (MicroSAS) or hyperspectral (HyperSAS) digital optical sensors. Both the MicroSAS and the HyperSAS normally consist of two radiance and one irradiance sensor. One radiance sensor is pointed at the ocean and measures the sea surface signal, while the other is pointed at the sky and provides information for surface glint correction of the data acquired with the first sensor. The irradiance sensor is used to monitor the downwelling light field, which is required for computing remote sensing reflectance.

The MicroSAS uses the Satlantic OCR-500 series digital optical sensors. It has a sampling frequency of 20 Hz and provides spectral sampling of seven channels between 300 and 865nm for each of water radiance, sky radiance and irradiance. The HyperSAS uses the Satlantic OCR-3000 (MiniSpec) series digital optical sensors. It provides an increased spectral sampling of 136 channels between 350 and 800 nm at a lower and variable sampling rate.

SAS data may be used to derive concentrations of sea-water constituents, estimate estimate phytoplankton abundance and marine productivity, monitor organic pollution, calibrate and validate satellite ocean colour products. The system can be mounted on vessels or marine structures such as towers or platforms, and can also be used for aerial surveys.

Optional extras for the SAS include GPS units and a tilt and heading sensor to provide orientation, geo-referencing and accurate time information, and a radiation pyrometer for land or sea surface temperature measurements.

Specifications

  MicroSAS HyperSAS
Irradiance field of view Cosine response (spectrally corrected)

3 % from 0 - 60°

10 % from 60 - 85°

Cosine response

± 3 % from 0 - 60°

10 % from 60 - 85°

Radiance field of view *3.3° 3° (FOV extension aperture)
Wavelength range 300 - 865 nm 350 - 800 nm
Number of channels

7 water radiance

7 irradiance

7 sky radiance

136
Spectral bandwidth 10 or 20 nm 3.3 nm
Sampling frequency 20 Hz variable

*Special adapters can also be mounted to the MicroSAS radiometer to narrow the field of view to a half angle of 1.5° to 0.75°.

AMT17 bio-optics data from MicroSAS (Above water radiance measurements)

Originator's Protocol for Data Acquisition and Analysis

Sky radiance, downwelling irradiance and water-leaving radiance measurements were obtained continuously using an Satlantic SeaWiFS Aircraft Simulator (MicroSAS). The optics instruments system consists of a down-looking radiance sensor and a sky-viewing radiance sensor mounted on the bow of the RRS Discovery, from where the optics casts were deployed in order to check the PIC algorithm performance, free of atmospheric error. Wavelengths used in this system were the same as in 2-band and 3-band calcite algorithms (491, 510, 556, 670, 781, 866, 443 nm). The radiance detector was set to view the water at 40° from nadir (Mueller et al., 2003) and its direction was adjusted constantly, using a computer-based system, to view the water 120° from the sun's azimuth. The water radiance sensor was able to view over an azimuth range of approximately 180° across the ships heading with no contamination from the ships wake. The system used the ships gyro-compass to determine the ships heading. Pitch and roll sensors filtered out any measurements made from sub-optimal viewing geometries due to ship motion. A downwelling irradiance sensor was mounted far from any potentially shading structures, on the tallest mast of the RRS Discovery.

All sensors were regularly rinsed with Mili-Q water in order to remove any salt deposits or dust. Data collected before 10h00 and after 14h00 (local time) were poorer in quality due to the decreased solar elevation. The data, collected at 16Hz, were filtered in order to remove as much residual white cap as possible. A plaque calibration was performed every several days to check for instrument drift.

References Cited

Mueller J.L., Morel A., Frouin R., Davis C., Arnone R., Carder K., Lee Z.P., Steward R.G., Hooker S.B., Mobley C.D., McLean S., Holben B., Miller M., Pietras C., Knobelspiesse K.D., Fargion G.S., Porter J., Voss K. 2003. Ocean optics protocols for satellite ocean color sensor validation, Revision 4, Volume III: Radiometric measurements and data analysis protocols. Greenbelt, MD: Goddard Space Flight Center, p.78.

BODC Data Processing Procedures

Reformatting

A data file (AMT17-merged-SAS-flow-VSF.out) was submitted to BODC containing MicroSAS radiance parameters at seven different wavelengths. The file also contained temperature, salinity and chlorophyll-a data from sea surface water from the ship's non-toxic supply and these were banked separately. The file was archived under BODC's accession number BGL060512. Additional metadata was provided, and these included date, time, latitude and longitude obtained through the ship's GPS stream.

The data were converted from the comma delimited SeaBass format into BODC internal format using BODC transfer function 451.

Unit conversions were necessary for the optic parameters. The units for the downwelling irradiance were provided in µW cm -2 nm and were converted to W m -2 nm. The units for the other radiance parameters were provided in µW cm -2 nm sr and were converted to W m -2 nm sr.

A parameter mapping table is provided below:

Originator's Parameter Units Description BODC Parameter Code Units Comments
Latitude degrees Latitude north (WGS84) by unspecified GPS system Global Positioning System (receiver type unspecified) ALATGP01 degrees n/a
Longitude degrees Longitude east (WGS84) by unspecified GPS system Global Positioning System (receiver type unspecified) ALONGP01 degrees n/a
Total water radiance µW cm -2 nm sr Total water radiance (unspecified single wavelength) from the water body by cosine-collector radiometer TTWTIR01 W m -2 nm sr Unit conversion applied (x 0.01)
Water leaving radiance µW cm -2 nm sr Water-leaving radiance (unspecified single wavelength) from the water body by cosine-collector radiometer RWLRCCR1 W m -2 nm sr Unit conversion applied (x 0.01)
Sky radiance µW cm -2 nm sr Sky radiance (unspecified single wavelength) in the atmosphere by cosine-collector radiometer SKYIRR01 W m -2 nm sr Unit conversion applied (x 0.01)
Normalised water leaving radiance µW cm -2 nm sr Normalised water leaving radiance (unspecified single wavelength) from the water body by cosine-collector radiometer NRWLRCR1 W m -2 nm sr Unit conversion applied (x 0.01)
Downwelling surface irradiance µW cm -2 nm Downwelling vector irradiance as energy (unspecified single wavelength) in the atmosphere by cosine-collector radiometer CSLRCCR1 W m -2 nm Unit conversion applied (x 0.01)
Relative azimuth degrees Instrument angle relative to solar plane (azimuth) IARAZM01 degrees n/a
Wavelength nm Wavelength of electromagnetic radiation measurement LAMBIN01 nm n/a

Screening

Reformatted MicroSAS data were transferred onto a graphics work station for visualisation using the in-house editor Edserplo. No valid data values were deleted. Flagging was achieved by modification of the associated BODC quality control flag for suspect or null values.

Banking

The profiles were banked to the National Oceanographic Database (NODB) following BODC procedures.


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 D299 (AMT17)
Departure Date 2005-10-15
Arrival Date 2005-11-28
Principal Scientist(s)Patrick M Holligan (University of Southampton School of Ocean and Earth Science)
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