A global view of one-dimensional solar radiative transfer through oceanic water clouds

Abstract

Solar radiative transfer through a cloudy atmosphere is commonly computed assuming clouds to be one-dimensional, i.e., plane-parallel. Here we provide a global perspective on how often and with what degree oceanic water clouds may be considered plane-parallel by fusing multi-view-angle and multi-spectral satellite data. We show that the view-angular distribution of the retrieved reflectance, spherical albedo and cloud optical thickness measured at 1 km resolution are indistinguishable from plane-parallel clouds 24%, 25% and 79% of the time, respectively, at the 95% confidence level of our measurement method. These plane-parallel clouds occur most frequently within regions dominated by stratiform clouds under solar zenith angles <60. For all other regions or sun-angles, the frequency in which clouds are indistinguishable from plane-parallel drops sharply to as low as a few percent. Our results provide a basis for interpreting space-time variability within many satellite-retrieved variables and reveal a need for continued efforts to handle three-dimensional radiative transfer in environmental modeling and monitoring systems. © 2010 by the American Geophysical Union.