Metadata Report for BODC Series Reference Number 1097093

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

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

*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°.

AMT18 Above water radiance measurement processing procedures

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 and radiance parameters at different wavelengths. The archived file was given the BODC's accession number BGL090250. Additional metadata was provided, and these included date, time, latitude and longitude obtained through the ship's GPS stream. Temperature, salinity and chlorophyll-a data were banked separately.

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;

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.

AMT18 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 measure 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 foremast of RRS James Clark Ross. 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 10h00 and 19h00 GMT, 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 10 Hz data, in order to remove as much residual white cap and glint as possible.

Processing was carried out post-cruise by applying filters at the 10 Hz data in order to remove the residual white cap and glint. The threshold for this procedure was to allow the lowest 5% of the data.

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

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:

• give early warning of any fundamental change in Atlantic ecosystem functionng
• improve forecasts of the future ocean state and associated socio-economic impacts
• provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.

The specific objectives are:

• To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
• To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
• To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases

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

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: