We analyze the plane-parallel bias of the shortwave cloud radiative forcing (SWCRF) of liquid and ice clouds
at 1 degree scales using global MODIS (Terra and Aqua) cloud optical property retrievals for four months of 2005
representative of the meteorological seasons. The (negative) bias is estimated as the difference of the SWCRF calculated
using the Plane-Parallel Homogeneous (PPH) method and the Independent Column Approximation (ICA). These
calculations require MODIS-derived means (for PPH calculations) and distributions (for ICA calculations) of cloud
optical thickness and effective radius as well as ancillary surface albedo and atmospheric information, that are inserted
into a broadband solar radiative transfer code. The absolute value of global SWCRF bias of liquid clouds at the top of the
atmosphere is ~6 Wm-2 for MODIS overpass times while the SWCRF bias for ice clouds is smaller in absolute terms by
~0.7 Wm-2, but with stronger spatial variability. Marine clouds of both phases are characterized by larger (more negative)
SWCRF biases than continental clouds. For clouds of both phases the SWCRF bias is collectively about 4 Wm-2 for
diurnal averages.