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Atmospheric Composition

Data from CALIPSO show that more than 50% of the clear sky, used to be identified as cloudless scenes by passive satellite sensors such MODIS, are actually covered by super-thin clouds. These subvisual clouds are mostly thin cirrus at high altitudes. Because cirrus clouds are generally composed of irregularly shaped ice crystals, polarized light passing through them can be significantly depolarized. Even a very thin layer of clouds composed of nonspherical particles can significantly extinguish the polarized radiance from the lower atmosphere, and thus can introduce significant uncertainties into the Glory data that uses total and polarized radiance to retrieve the physical properties of aerosols and low-level clouds. The objective of this proposal is to retrieve the physical properties of subvisual clouds to assist the Glory mission in reducing the uncertainty in the retrieved aerosols. To achieve this goal, we will merge the Glory data with the CALIPSO measurements and use Glory and CALIPSO measurements to detect scenes with subvisual clouds. The data from Glory’s Cloud Camera are used to identify the clear and cloudy scenes. Glory’s polarized radiances at 1.37 μm and the CALIPSO data will be used to retrieve the physical properties of the subvisual clouds. An adding-doubling radiative transfer model will be employed to simulate the total and polarized radiances at the top-of-atmosphere with various physical properties of subvisual clouds as inputs. The input physical properties of the clouds and the total and polarized radiances from the model outputs construct the multiangular lookup tables. The physical properties of the subvisual clouds are obtained by searching the lookup tables for multiangular best match of model-simulated polarized radiances with the measured data. The retrieved physical properties of subvisual clouds can help remove their radiation effect from Glory aerosol and even cloud phase products.

Project PI: Wenbo Sun/NASA Langley Research Center

NASA Langley Research Center Hampton, VA 236810001

Phone: (757)864-9986

Fax: (757) 864-7996

Email: w.sun@larc.nasa.gov

http://cas.hamptonu.edu/centerinfo/directory/documents/CASDirectory2008web.pdf

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Started: Sep 27, 2010

Last Activity: Jan 04, 2011

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