HR: 0800h
AN: A41B-0443    [Abstracts]
TI: The behaviour of cloud and clear sky brightness in the vicinity of the cloud edge
AU: Bass, L
AF: L.P.Bass, 1Keldysh Institute of Applied Mathematics, Russian Academy of Science Miusskaya Sq. 4,125047 Moscow, Russia, Moscow, 125047, Russian Federation
AU: Nikolaeva, O
AF: L.P.Bass, 1Keldysh Institute of Applied Mathematics, Russian Academy of Science Miusskaya Sq. 4,125047 Moscow, Russia, Moscow, 125047, Russian Federation
AU: Kuznetsov, V
EM: bass@kiam.ru
AF: V.S.Kuznetsov, 2Research Scientific Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia, Moscow, 123182, Russian Federation
AU: * Kokhanovsky, A
AF: A.A.Kokhanovsky, Institute of Remote Sensing, Bremen University, Otto Hahn Allee 1 28334 Bremen, Germany, Bremen, 28334, Germany
AB: L.P. Bass1, O.V. Nikolaeva1, V.S.Kuznetsov2, A. A. Kokhanovsky3,4 1Keldysh Institute of Applied Mathematics, Russian Academy of Science Miusskaya Sq. 4,125047 Moscow, Russia 2Research Scientific Center "Kurchatov Institute", Kurchatov Sq. 1, 123182 Moscow, Russia 3Institute of Remote Sensing, Bremen University, Otto Hahn Allee 1 28334 Bremen, Germany 4Institute of Physics, National Academy of Sciences of Belarus, Nezaleznasti Pr. 70 220072 Minsk, Belarus In the solution of remote sensing problems in the framework of the Independent Pixel Approximation (IPA) the horizontal transport of radiation is not taken into account. Therefore, the large errors in the retrieved optical parameters of a medium under study can occur in retrievals for regions, where 3-D radiative transfer effects are of importance (Wen et al, 2007, Titov, 1998). In the present work we analyze the brightness at the edge of a cubic cloud. The energy balance equations within the clear sky-cloud boundary layer are studied. The boundary layer is the domain that includes the vertical boundary of the adjacent pixels with different optical properties. Balance equation connects the radiation fluxes entering into the boundary layer and outgoing from it, and also the amount of energy absorbed in the layer. It is demonstrated that horizontal transport of radiation generates several observable phenomena such as "shadowing" and "brightening" (depending on the Sun position with respect to the cloud and also the area studied). All calculations are performed with the code Raduga-5.1 (Nikolaeva et al., 2005) developed for the computer with the parallel architecture for 1-D, 2-D, 3-D radiative transfer. The code is based on the numerical solution of the integro – differential radiative transfer equation (RTE) with correspondent boundary conditions and prescribed properties of a light scattering medium. Grids with respect to spatial and angular variables are introduced and RTE reduced to the system of the grid equations. The derived system of equations is solved using standard finite difference techniques. The comparison with Monte-Carlo (see www.libradtran.org) calculations demonstrated a high accuracy of the method. The differences between these two completely different types of 3-D RTE solution are within 1%. References Nikolaeva, O. V., L.P.Bass, T.A.Germogenova, A.A.Kokhanovsky, V.S.Kuznetsov, B. Mayer, 2005: The influence of neighbouring clouds on the clear sky reflectance studied with the 3–D transport code RADUGA, J. Quant. Spectr. Rad. Transfer, 94,405-424. Titov, G. A., 1998: Radiative horizontal transport and absorption in stratocumulus clouds, J. Atmos. Sci., 55, 2549- 2560. Wen, G., A. Marshak, R.F. Cahalan, L.A. Remer, and R.G. Kleidman, 2007: 3-D aerosol-cloud radiative interaction observed in collocated MODIS and ASTER images of cumulus cloud fields. J. Geophys. Res., 112, D13204, doi: 10.1029/2006JD008267.
DE: 0321 Cloud/radiation interaction
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting