Simulation of Radiative Properties of Ice-Crystal Broken Clouds
Tatiana B. Zhuravleva, Institute of Atmospheric Optics SB RAS,
Akademicheskii av., 1, 634055, Tomsk, Russia, Email: ztb@iao.ru
The real clouds are highly variable in space; therefore, the radiative transfer modeling
of radiative effects of the atmosphere - underlying surface system must account for
cloud field structure on much smaller scales than the resolution of the atmospheric
general circulation models. In the last few years, much research effort has been
devoted to the study of liquid-water clouds. Here, we concentrate on horizontal
inhomogeneity effects associated with ice-crystal clouds.
The random nature of real broken clouds gives no way to describe uniquely the cloudradiation interaction; therefore, we employ the statistical approach to radiative transfer
modeling in the cloudy atmosphere. Mathematical model of the cloud field is
constructed based on the Poisson point fluxes on straight lines. The mean fluxes and
brightness fields of solar radiation in statistically homogenous broken clouds are
calculated by the method of closed equations, based on the Monte Carlo solution of
the system of equations for mean intensity (Titov, 1990).
The single-scattering properties (scattering phase function, single-scattering albedo
and extinction coefficient) of ice cloud microstructure model with ice particles shaped
as the solid hexagonal plates and columns, are used described by A. Petrushin (1998).
Mean albedo, transmittance and brightness fields at a nonabsorbing visible
wavelength (0.63 m) and in the ice particle absorption band (2.6 m) are calculated
for wide range of the optical and geometrical parameters of ice clouds. The influence
of the effects caused by the stochastic cloud geometry is estimated by comparison
with horizontally-homogeneous model results.
The work is partially supported by INTAS contract “LIDAR multiple scattering from
clouds including spherical and non-spherical particles” and the Russian Fund for
Basic Research (through the grant 00-05-65456.
Petrushin A.G., 1998: // Problems in atmospheric physics. Gidrometeoizdat. St.
Petersburg. P. 118-149.
Titov G.A., 1990: J. Atmos. Sci., 47, 14-38.