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An Initial Analysis of the Pixel-Level Uncertainties in Global MODIS Cloud Optical Thickness and Effective Particle Size RetrievalsModerate Resolution Imaging Spectroradiometer (MODIS) retrievals of cloud optical thickness and effective particle radius employ well-known solar reflectance techniques using pre-calculated reflectance look-up tables. We evaluate the quantitative uncertainty in simultaneous retrievals of cloud optical thickness and particle size for this type of algorithm. The technique uses sensitivity calculations derived from the reflectance look-up tables, coupled with estimates for the effect of various error terms on the uncertainty in inferring the actual cloud-top reflectance. The error terms include the effects of instrument calibration, surface spectral albedo, and atmospheric corrections on both water and ice cloud retrievals. Because particle shapes in ice clouds are highly variable, the effect of particle shape is analyzed separately with a more approximate method. Results will deal exclusively with pixel-level uncertainties associated with plane-parallel clouds; real-world radiative departures from a plane-parallel model are an additional consideration. While we demonstrate the uncertainty technique with operational 1 km MODIS retrievals from the Terra and Aqua satellite platforms, the technique is applicable to any reflectance-based satellite- or air-borne sensor retrieval using similar spectral channels.
Document ID
20040171143
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Platnick, S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
King, Michael D.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wind, B.
(L-3 Communication Government Services, Inc. Vienna, VA, United States)
Gray, M. A.
(L-3 Communication Government Services, Inc. Vienna, VA, United States)
Hubanks, P. A.
(L-3 Communication Government Services, Inc. Vienna, VA, United States)
Date Acquired
August 22, 2013
Publication Date
January 1, 2004
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: Remote Sensing of Atmosphere, Ocean, Environment and Space
Location: Honolulu, HI
Country: United States
Start Date: November 8, 2004
End Date: November 11, 2004
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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