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Science Lecture by Michael Box |
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Date: December 15, 2005
Time: 2:00pm
Location: NIA, Rm 137
Presentation: pdf
Application of Radiative Perturbation Theory to MISR Aerosol Retrievals
Michael A. Box, University of New South Wales, Sydney
The Multi-angle Imaging Spectroradiometer (MISR) on board NASA’a Terra satellite is capable of providing highly valuable data on atmospheric aerosols, as each pixel is viewed from up to 9 different directions. Such data can be used to determine not only the aerosol loading (optical thickness), but also, at least in principle, the aerosol type. Since the radiative transfer equation cannot be directly inverted to take us from observed radiances to the underlying atmospheric optical properties, retrieval methods are indirect. Two main approaches are available – look-up tables, and iterative methods. While iteration is potentially more powerful, it is also much more time-intensive.
Radiative perturbation theory has the potential to significantly increase the efficiency of iteration methods, as it can provide the elements of the Jacobian matrix (derivatives of the measurement values with respect to the atmospheric components) at no cost, a distinct improvement on finite difference methods. We have applied radiative perturbation theory to a MISR data set off the west coast of Africa in 2003. The atmospheric optical model was assumed to comprise a set of standard aerosol types, with pre-computed optical properties, which could be assigned to either of two atmospheric layers. The algorithm then returned the required optical thickness of each component. Results obtained are reasonably consistent with standard MISR retrievals.
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