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Application of Polarization to the MODIS Aerosol Retrieval Over LandReflectance measurements in the visible and infrared wavelengths, from the Moderate Resolution Imaging Spectroradiometer (MODIS), are used to derive aerosol optical thicknesses (AOT) and aerosol properties over land surfaces. The measured spectral reflectance is compared with lookup tables, containing theoretical reflectance calculated by radiative transfer (RT) code. Specifically, this RT code calculates top of the atmosphere (TOA) intensities based on a scalar treatment of radiation, neglecting the effects of polarization. In the red and near infrared (NIR) wavelengths the use of the scalar RT code is of sufficient accuracy to model TOA reflectance. However, in the blue, molecular and aerosol scattering dominate the TOA signal. Here, polarization effects can be large, and should be included in the lookup table derivation. Using a RT code that allows for both vector and scalar calculations, we examine the reflectance differences at the TOA, with and without polarization. We find that the differences in blue channel TOA reflectance (vector - scalar) may reach values of 0.01 or greater, depending on the sun/surface/sensor scattering geometry. Reflectance errors of this magnitude translate to AOT differences of 0.1, which is a very large error, especially when the actual AOT is low. As a result of this study, the next version of aerosol retrieval from MODIS over land will include polarization.
Document ID
20040081254
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Levy, Robert C. (Science Systems and Applications, Inc. United States)
Remer, Lorraine R. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Kaufman, Yoram J. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2004
Subject Category
Earth Resources And Remote Sensing
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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