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Optical-Microphysical Cirrus ModelA model is presented that permits the simulation of the optical properties of cirrus clouds as measured with depolarization Raman lidars. It comprises a one-dimensional cirrus model with explicit microphysics and an optical module that transforms the microphysical model output to cloud and particle optical properties. The optical model takes into account scattering by randomly oriented or horizontally aligned planar and columnar monocrystals and polycrystals. Key cloud properties such as the fraction of plate-like particles and the number of basic crystals per polycrystal are parameterized in terms of the ambient temperature, the nucleation temperature, or the mass of the particles. The optical-microphysical model is used to simulate the lidar measurement of a synoptically forced cirrostratus in a first case study. It turns out that a cirrus cloud consisting of only monocrystals in random orientation is too simple a model scenario to explain the observations. However, good agreement between simulation and observation is reached when the formation of polycrystals or the horizontal alignment of monocrystals is permitted. Moreover, the model results show that plate fraction and morphological complexity are best parameterized in terms of particle mass, or ambient temperature which indicates that the ambient conditions affect cirrus optical properties more than those during particle formation. Furthermore, the modeled profiles of particle shape and size are in excellent agreement with in situ and laboratory studies, i.e., (partly oriented) polycrystalline particles with mainly planar basic crystals in the cloud bottom layer, and monocrystals above, with the fraction of columns increasing and the shape and size of the particles changing from large thin plates and long columns to small, more isometric crystals from cloud center to top. The findings of this case study corroborate the microphysical interpretation of cirrus measurements with lidar as suggested previously.
Document ID
20090034979
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Reichardt, J.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Reichardt, S.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Lin, R.-F.
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Hess, M.
(Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Wessling, Germany)
McGee, T. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Starr, D. O.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
November 1, 2008
Publication Information
Publication: Journal of Geophysical Research - Atmospheres
Publisher: American Geophysical Union
Volume: 113
ISSN: 0148-0227
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Other

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