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Ocean Color Inferred from Radiometers on Low-Flying Aircraft

View Article: PubMed Central - PubMed

ABSTRACT

The color of sunlight reflected from the ocean to orbiting visible radiometers has provided a great deal of information about the global ocean, after suitable corrections are made for atmospheric effects. Similar ocean-color measurements can be made from a low-flying aircraft to get higher spatial resolution and to obtain measurements under clouds. A different set of corrections is required in this case, and we describe algorithms to correct for clouds and sea-surface effects. An example is presented and errors in the corrections discussed.

No MeSH data available.


Relative error in estimate of surface irradiance δE/E produced by measuring irradiance at 150 m. Curves represent MODTRAN maritime models for tropical (black) and sub-arctic winter (red) atmospheres.
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f5-sensors-08-00860: Relative error in estimate of surface irradiance δE/E produced by measuring irradiance at 150 m. Curves represent MODTRAN maritime models for tropical (black) and sub-arctic winter (red) atmospheres.

Mentions: One obvious source of error arises from the assumption that the downwelling irradiance measured at the aircraft altitude is a good approximation to the downwelling irradiance at the surface. An example of the relative error can be estimated using MODTRAN to calculate the solar irradiance at the aircraft altitude and at the surface for a specific set of conditions. Fig. 5 presents results for the relative error as a function of wavelength for a solar zenith angle of 30°, an aircraft altitude of 150 m, clear skies, and the atmospheric models labeled as tropical and sub-arctic winter. Values for the mid-latitude summer, mid-latitude winter, and sub-arctic summer models lie between these extremes. The relative error is generally below 2%, except in the region of a water vapor absorption band around 720-730 nm and an O2 absorption at 760 nm. The water vapor absorption band is the only region where the five MODTRAN models differ significantly. The filters typically used for ocean-color measurements, of course, avoid these regions of the spectrum.


Ocean Color Inferred from Radiometers on Low-Flying Aircraft
Relative error in estimate of surface irradiance δE/E produced by measuring irradiance at 150 m. Curves represent MODTRAN maritime models for tropical (black) and sub-arctic winter (red) atmospheres.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3927510&req=5

f5-sensors-08-00860: Relative error in estimate of surface irradiance δE/E produced by measuring irradiance at 150 m. Curves represent MODTRAN maritime models for tropical (black) and sub-arctic winter (red) atmospheres.
Mentions: One obvious source of error arises from the assumption that the downwelling irradiance measured at the aircraft altitude is a good approximation to the downwelling irradiance at the surface. An example of the relative error can be estimated using MODTRAN to calculate the solar irradiance at the aircraft altitude and at the surface for a specific set of conditions. Fig. 5 presents results for the relative error as a function of wavelength for a solar zenith angle of 30°, an aircraft altitude of 150 m, clear skies, and the atmospheric models labeled as tropical and sub-arctic winter. Values for the mid-latitude summer, mid-latitude winter, and sub-arctic summer models lie between these extremes. The relative error is generally below 2%, except in the region of a water vapor absorption band around 720-730 nm and an O2 absorption at 760 nm. The water vapor absorption band is the only region where the five MODTRAN models differ significantly. The filters typically used for ocean-color measurements, of course, avoid these regions of the spectrum.

View Article: PubMed Central - PubMed

ABSTRACT

The color of sunlight reflected from the ocean to orbiting visible radiometers has provided a great deal of information about the global ocean, after suitable corrections are made for atmospheric effects. Similar ocean-color measurements can be made from a low-flying aircraft to get higher spatial resolution and to obtain measurements under clouds. A different set of corrections is required in this case, and we describe algorithms to correct for clouds and sea-surface effects. An example is presented and errors in the corrections discussed.

No MeSH data available.