[Parameters: Topic='OCEANS', Term='OCEAN OPTICS', Variable_Level_1='IRRADIANCE']
Visible light radiometer data for the Broke-West SurveyEntry ID: BROKE-West_light
Abstract: Spectra of downwelling irradiance and upwelling, water-leaving radiance were measured continuously, as fast as light-levels would allow, during stations and whilst the ship was underway. Data processing will yield reflectance spectra along the cruise track.
One irradiance sensor was mounted on the monkey isle looking directly upwards. Two identical radiance sensors were ... mounted in the bows, looking through the forward hawser hole. These sensors were mounted onto an aluminium pole using clamps, and the pole was lashed with 3 webbing ties to deck fixtures. The look-angle of the radiance sensors was measured using a simple plumb-line. Data from all 3 sensors was directed through the ship's internal serial network to a single laptop, running the manufacturer's software, which was set to gather one spectrum from each sensor in turn in rapid burst mode, i.e. as fast as ambient light-levels would allow a meaningful measurement. The sensors were cleaned daily using warm water and a lint-free tissue.
The data were processed automatically by the manufacturer's software to give calibrated radiance and irradiance spectra, from 320 to 900nm. Both raw and calibrated data were recorded.
Not yet complete:
The entire dataset must be merged with the navigation record to eliminate data collected when direct sunlight was shaded by the ship's superstructure, when rain or snow was falling, and when light levels were below the instrument detection level or the sun's elevation less than 5 degrees above the horizon. The two radiance sensor records will be screened to reject spectra recorded from a sensor looking toward the sun's reflection off the water. Remaining pairs of water-leaving radiance and downwelling irradiance will then be corrected for look-geometry and surface effects, and combined to give remote-sensing reflectance (equal to water-leaving radiance divided by downwelling irradiance, mimicking the measurements made by satellite-borne sensors).
Currently, the dataset comprises time-stamped files, each file containing a single spectrum of upwelling radiance or downwelling irradiance, in geophysical units.
This data set description is a member of a collection. The collection is described in
Start Date: 2006-01-17Stop Date: 2006-02-28
ISO Topic Category
Quality Data quality appear good with data loss when heavier seas rotated the sensor mounting pole. In these cases, the data will be removed from the issued dataset.
Visible radiometers measured in daylight at a temporal resolution of the order of milli-seconds, corresponding to spatial resolution on the order of metres or less.
Access Constraints These data are not yet publicly available, pending processing and quality control. These data are currently stored on a series of DVDs.
Use Constraints This data set conforms to the PICCCBY Attribution License
The principal investigator must be consulted before using these data.
Data Set Progress
Distribution Media: DVD
Role: TECHNICAL CONTACT
Role: DIF AUTHOR
Fax: +49 471 4831 1797
Email: j.schwarz at niwa.co.nz
National Institute for Water and Atmosphere Research 295-301 Evans Bay Parade
City: Greta Point
Province or State: Wellington
Postal Code: 6021
Country: New Zealand
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2006-03-27
Last DIF Revision Date: 2014-09-11