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Surface Emissivity Maps for Use in Satellite Retrievals of Longwave RadiationAccurate accounting of surface emissivity is essential for the retrievals of surface temperature from remote sensing measurements, and for the computations of longwave (LW) radiation budget of the Earth?s surface. Past studies of the above topics assumed that emissivity for all surface types, and across the entire LW spectrum is equal to unity. There is strong evidence, however, that emissivity of many surface materials is significantly lower than unity, and varies considerably across the LW spectrum. We have developed global maps of surface emissivity for the broadband LW region, the thermal infrared window region (8-12 micron), and 12 narrow LW spectral bands. The 17 surface types defined by the International Geosphere Biosphere Programme (IGBP) were adopted as such, and an additional (18th) surface type was introduced to represent tundra-like surfaces. Laboratory measurements of spectral reflectances of 10 different surface materials were converted to corresponding emissivities. The 10 surface materials were then associated with 18 surface types. Emissivities for the 18 surface types were first computed for each of the 12 narrow spectral bands. Emissivities for the broadband and the window region were then constituted from the spectral band values by weighting them with Planck function energy distribution.
Document ID
19990100634
Document Type
Technical Publication (TP)
Authors
Wilber, Anne C.
(Analytical Services and Materials, Inc. Hampton, VA United States)
Kratz, David P.
(NASA Langley Research Center Hampton,VA United States)
Gupta, Shashi K.
(Analytical Services and Materials, Inc. Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1999
Subject Category
Meteorology And Climatology
Report/Patent Number
NAS 1.60:209362
L-17861
NASA/TP-1999-209362
Funding Number(s)
PROJECT: RTOP 291-01-60
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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