Improving MISR AOD Retrievals With Low-Light-Level Corrections for Veiling Light

Operational retrievals of aerosol optical depth (AOD) from Multi-angle Imaging SpectroRadiometer (MISR) data have been shown to have a high bias in pristine oceanic areas. One line of evidence involves comparison with Maritime Aerosol Network (MAN) observations, including the areas of low aerosol lo...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2018-03, Vol.56 (3), p.1251-1268
Main Authors: Witek, Marcin L., Diner, David J., Garay, Michael J., Xu, Feng, Bull, Michael A., Seidel, Felix C.
Format: Article
Language:English
Subjects:
Aerosols
Air pollution
Bias
Brightness
Cameras
Clouds
Coefficients
Corrections
Imaging techniques
Lenses
Light
Light scattering
Meteorological satellites
MODIS
Optical analysis
Optical components
Prototypes
remote sensing
Satellites
Sea ice
Spectroradiometers
Stray light
Wavelength
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Summary:Operational retrievals of aerosol optical depth (AOD) from Multi-angle Imaging SpectroRadiometer (MISR) data have been shown to have a high bias in pristine oceanic areas. One line of evidence involves comparison with Maritime Aerosol Network (MAN) observations, including the areas of low aerosol loading close to Antarctica. In this paper, a principal reason for the AOD overestimation is identified, which is stray light measured by the MISR cameras in dark regions of high-contrast scenes. A small fraction of the light from surrounding bright areas, such as clouds or sea ice, is redistributed to dark areas, artificially increasing their brightness. Internal reflections and light scattering from optical elements in MISR's pushbroom cameras contribute to this veiling light effect. A simple correction model is developed that relies on the average scene brightness and an empirically determined set of veiling light coefficients for each MISR camera and wavelength. Several independent methods are employed to determine these coefficients. Three sets of coefficients are further implemented and tested in prototype MISR 4.4-km AOD retrievals. The results show dramatic improvements in retrieved AODs compared against MAN observations and the currently operational V22 MISR retrievals. For the best performing set of coefficients, the bias is reduced by 51%, from 0.039 to 0.019, the RMSE is lowered by 19%, from 0.062 to 0.050, and 84% of retrievals fall within the uncertainty envelope compared with 66% of retrievals in V22. The best performing set will be implemented operationally in the next V23 MISR AOD product release.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2017.2727342