Improved MODIS aerosol retrieval using modified VIS/SWIR surface albedo ratios over urban scenes
Item
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Title
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Improved MODIS aerosol retrieval using modified VIS/SWIR surface albedo ratios over urban scenes
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Identifier
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d_2009_2013:cb98c7b9a9f9:10003
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identifier
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10062
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Creator
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Oo, Min Min,
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Contributor
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Barry M. Gross
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Date
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2009
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Language
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English
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Publisher
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City University of New York.
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Subject
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Atmospheric sciences | Environmental engineering | Electrical engineering | Remote sensing | Aerosol optical depth | Aerosol retrieval | Land surface reflectance | Satellite remote sensing
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Abstract
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Determination of Aerosol Optical Depth (AOD) by satellite remote sensing measurements over land is complicated by the fact that the Top of Atmosphere (TOA) reflectance is a combination of the desired atmospheric path reflectance as well as the ground reflectance. Unfortunately, inaccurate surface modeling results in inaccurate AOD retrieval as well as reducing spatial resolution. In this thesis, the primarily focus is on the use of simultaneous MODIS and AERONET sky radiometer data to refine the surface albedo models regionally and improve on the current AOD operational retrieval. In particular, it is shown that the correlation coefficient assumption used in the MODIS Collection (5) model between the VIS and SWIR channels used for surface reflection parameterization in urban areas such as New York and Mexico City is severely underestimated. This is demonstrated both directly using high spatial imagery data from Hyperion and indirectly by constraining MODIS TOA reflection data with AERONET Sky radiometer AOD retrievals. Especially, the combining of the satellite and radiometer measurements allows to generate a regional VIS/SWIR surface reflectance correlation coefficient map at spatial resolutions up to 1.5km is shown. Application of the regional VIS/SWIR surface reflectance ratio model is shown to completely remove the bias and reduce uncertainty at the operational resolution of 10km as well as at higher resolutions to 1.5km resolution. Finally, spatial AOD retrievals using the surface albedo model are developed within the MODIS operational software showing the reduction in artificial AOD hotspots. Moreover, validation of MODIS derived AOD over vegetated area, located at Billerica-Massachusetts in this experiment, is discussed. We found that there is also slight error in MODIS surface reflectance assumption over the vegetated area. We suggest a new MVI-VIS/SWIR surface model for both urban and vegetated area and show improvement in AOD retrieval. In addition, the angular dependence of the surface albedo is explored. In particular, it is found that the correlation coefficients are insensitive to scattering angle as expected MODIS and errors in using a Lambertian assumption are shown to be less than the errors associated in the albedo variability.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Engineering
