HR: 09:30h
AN: A11D-05    [Abstracts]
TI: The Discovery of Cloud Radiative Smoothing and its Consequences
AU: * Wiscombe, W J
EM: Warren.J.Wiscombe@nasa.gov
AF: NASA Goddard Space Flight Center, Code 613.2, Greenbelt, MD 20771
AU: Marshak, A
EM: Alexander.Marshak@nasa.gov
AF: NASA Goddard Space Flight Center, Code 613.2, Greenbelt, MD 20771
AU: Davis, A B
EM: adavis@lanl.gov
AF: Los Alamos National Lab, TA-3, NISC Bldg, Rm 2017, Los Alamos, NM 87545
AB: Scale-dependent radiative smoothing theory was one of the major contributions to 3D cloud radiation theory in the previous decade, whose confirmation was due entirely to satellite measurements of cloud radiance. Stephens (1988) was the first to formally and mathematically develop the idea of a scale hierarchy in 3D cloud radiative transfer. He concluded that "multiple scattering acts to filter out the smaller-scale contributions" to cloud radiances. Stephens insight was confirmed by Cahalan et al.'s 1991 discovery of the so-called "Landsat scale break". The break occurred at a spatial scale of about 250 m in the power spectrum of Landsat radiance for a stratocumulus cloud scene. For a while, there were competing physical and instrumental theories for the scale break, but eventually the powerful analyses of Marshak, Davis and collaborators in the mid-1990s established firmly that the break was radiative in nature. They greatly extended and rigorized the concept of "radiative smoothing" and derived a remarkably simple expression for the radiative smoothing scale. They also identified "radiative roughening", the antithesis of radiative smoothing, and the circumstances under which it occurs. Spinoffs from this suite of discoveries include a whole new family of multiple-scattering lidars which provide entirely new information about clouds.
DE: 0321 Cloud/radiation interaction
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005