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Spectral Invariant Behavior of Zenith Radiance Around Cloud Edges Observed by ARM SWSThe ARM Shortwave Spectrometer (SWS) measures zenith radiance at 418 wavelengths between 350 and 2170 nm. Because of its 1-sec sampling resolution, the SWS provides a unique capability to study the transition zone between cloudy and clear sky areas. A spectral invariant behavior is found between ratios of zenith radiance spectra during the transition from cloudy to cloud-free. This behavior suggests that the spectral signature of the transition zone is a linear mixture between the two extremes (definitely cloudy and definitely clear). The weighting function of the linear mixture is a wavelength-independent characteristic of the transition zone. It is shown that the transition zone spectrum is fully determined by this function and zenith radiance spectra of clear and cloudy regions. An important result of these discoveries is that high temporal resolution radiance measurements in the clear-to-cloud transition zone can be well approximated by lower temporal resolution measurements plus linear interpolation.
Document ID
20100034937
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Marshak, A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Knyazikhin, Y.
(Boston Univ. Boston, MA, United States)
Chiu, J. C.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Wiscombe, W. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
August 19, 2009
Publication Information
Publication: Geophysical Research Letters
Volume: 36
Issue: 16
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Other

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