HR: 0800h
AN: A51A-0738    [Abstracts]
TI: Radiative Effects of Stratus Cloud Subgrid Scale Variability Observed by MODIS
AU: * Jensen, M P
EM: mjensen@bnl.gov
AF: Brookhaven National Laboratory, ESSD/ESD Bldg 490D, Upton, NY 11973
AU: Vogelmann, A M
EM: vogelmann@bnl.gov
AF: Brookhaven National Laboratory, ESSD/ESD Bldg 490D, Upton, NY 11973
AU: Collins, W
EM: wcollinds@ucar.edu
AF: NCAR, NCAR, Boulder, CO 80305
AB: Marine boundary layer are important to the planetary energy balance because they cover large regions of the oceans and possess an albedo that is considerably larger than underlying ocean surface. General circulation models (GCM) typically ignore the horizontal variability of cloud liquid water path within these clouds, and previous studies differ on the importance that this variability has on the solar albedo and, therefore, its possible impact on the simulated climate. We use MODIS cloud retrievals for five prominent stratus regions to resolve this issue. The parameters for this study are obtained from a companion study that analyzes 4 years of MODIS cloud properties (see presentation by Vogelmann et al.). For each scene with the area of a GCM gridbox, the probability density function of the MODIS pixel-scale optical depths is fit using a gamma distribution. Radiative transfer calculations using DISORT are used to determine the differences in cloud albedo when the variability is treated versus when it is ignored. We find that, when the cloud regions are carefully screened, the effects of the albedo differences are generally small and ignoring the variability in models does not present a large radiative effect.
DE: 3359 Radiative processes
DE: 3307 Boundary layer processes
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting