Metadata Report for BODC Series Reference Number 1097112


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 AMT19-MERGED-SAS-FLOW-AC9.MAT
BODC Series Reference 1097112
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2009-10-12 12:10
End Time (yyyy-mm-dd hh:mm) 2009-11-28 10:33
Nominal Cycle Interval 10.0 seconds
 

Spatial Co-ordinates

Start Latitude 50.15650 N ( 50° 9.4' N )
End Latitude 46.56770 S ( 46° 34.1' S )
Start Longitude 5.05820 W ( 5° 3.5' W )
End Longitude 55.74470 W ( 55° 44.7' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth -16.4 m
Maximum Sensor Depth -11.0 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°.

AMT19 Above water radiance measurement from MicroSAS Data Processing

BODC Data Processing Procedures

A file was submitted to BODC containing data from MicroSAS radiometer merged with underway data. the following parameters were supplied: temperature, salinity, chlorophyll-a, backscattering coefficient, absorption and attenuation coefficients' and radiance parameters at different wavelengths. The archived file was given the BODC's accession number BGL100197, which includes two different dataset IDs (one for the radiometer parameters and the other for the underway data). Additional metadata was provided, and these included date, time, latitude and longitude obtained through the ship's GPS stream.

Unit conversions were necessary for the optic parameters, as the units for the downwelling irradiance were provided in µW cm -2 nm and were converted to W m -2 nm, and units for other radiance parameters were provided in µW cm -2 nm sr and were converted to W m -2 nm sr. Azimuth and wavelength were provided in the same units as in the BODC Parameter Dictionary, no conversion was applied to these data.

A parameter mapping table is provided below;

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

Parameters' marked with (*) are described on the following link: Standardized Field Names and Units for SeaBASS files

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.

AMT19 Above water radiance measurement from MicroSAS

Originator's Protocol for Data Acquisition and Analysis

A Satlantic SeaWiFS Aircraft Simulator (MicroSAS) was installed on RRS James Cook in order to obtain data for total upwelling radiance, downwelling irradiance, sky radiance and total downwelling irradiance. These data were used to check the PIC algorithm performance, free of atmospheric error.

The wavelengths measured with the MicroSAS were the same as the ones used in the 2-band and 3-band PIC algorithms. The system consisted of a down-looking ocean radiance sensor and an up-looking sky-viewing radiance sensor, both mounted on the platform. All sensors were regularly rinsed with Mili-Q water in order to remove any salt deposits or dust.

The water-viewing radiance detector was set to view the ocean surface at 40° from nadir and the sky-viewing radiance sensor was set to view the sky 40° from zenith (used in the correction for Fresnel reflectance) as recommended by Mueller et al. (2003b). Special attention was given during the installation of the downwelling irradiance sensor, in order to minimize any shading from the ship's superstructure.

The water radiance sensor was able to view over an azimuth range of ~180° across the ship's heading. Its direction was constantly adjusted by a computer-based system that calculated the sun's azimuth angle relative to the ship's heading and elevation.

Data were collected between 10:00 and 19:00 hours UT, approximately, and calibration protocols were performed according to Mueller (Mueller et al. 2003a; Mueller et al. 2003b; Mueller et al. 2003c).

Post-cruise processing was performed on the 16 Hz data, which was filtered to remove residual white cap and glint. The lowest 5% of the data was accepted as a threshold for this procedure.

References Cited

Mueller J.L., Austin R.W., Morel A., Fargion G.S., McClain C.R. 2003a. Ocean optics protocols for satellite ocean color sensor validation, Revision 4, Volume I: Introduction, background, and conventions. Greenbelt, MD: Goddard Space Flight Center. 50 p.

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. 2003b. 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. 78 p.

Mueller J.L., Pietras C., Hooker S.B., Austin R.W., Miller M., Knobelspiesse K.D., Frouin R., Holben B., Voss K. 2003c. Ocean optics protocols for satellite ocean color sensor validation, Revision 4, Volume II: Instrument specifications, characterisation and calibration. Greenbelt, MD: Goddard Space Flight Center.


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 JC039 (AMT19, JC040)
Departure Date 2009-10-13
Arrival Date 2009-12-01
Principal Scientist(s)Andrew Rees (Plymouth Marine Laboratory)
Ship RRS James Cook

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