P4.5
Physical decoupling of near-infrared (3.9um) solar and thermal radiation components through satellite observations of total solar eclipses
Steven D. Miller, NRL, Monterey, CA
Solar and terrestrial emissions are regarded largely as being decoupled from one another, save for a narrow spectral region in the vicinity of the 3.9 micrometers window where the two components are of comparable magnitude. Satellite radiometers with channels in this part of the spectrum detect solar reflection and thermal emission the earth/atmosphere system for daytime scenes. This poses a problem to cloud optical property retrievals whose forward functions are predicated exclusively on either one source or the other. These models require the removal of the unwanted component via empirical relationships, iterative methods, or physically-based approximations applied to the data. In any circumstance no direct measure of the associated error is available. Here, total solar eclipses are proposed as a physical mechanism for the decoupling of the two radiative components. Decoupling is achieved by time-differencing scenes before and during passage of the umbral shadow. A case study taken from the February 26, 1998 total solar eclipse passage near Central America is presented, including an analysis of a quasi-stable marine stratus layer that existed within the path of totality. Considerations for the physical decoupling operation are discussed and comparisons of derived results with previous approximations are presented.
Poster Session 4, Radiances, Clouds, and Retrievals
Wednesday, 17 October 2001, 9:15 AM-11:00 AM
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