LAUSR

Abstract The I3RC Community Monte Carlo model of three-dimensional (3D) radiative transfer (I3RC-CM) was improved by allowing the specification of surfaces with variable albedo. A series of simulations were performed using the improved I3RC-CM in order to investigate the role of surface albedo heterogeneity in shortwave radiation transfer under 3D clouds. For the same regionally-averaged surface albedo of 0.25, the top-of-atmosphere (TOA) reflectivity was found to vary by approximately 10−3 orders of magnitude under different surface albedo patterns. The inhomogeneous surface albedo was discovered to have a greater impact on TOA reflectivity at the non-absorbing wavelengths than that at the absorbing wavelengths, and its effect on cloud absorption was revealed to be stronger at a wavelength of 1.64 μm than at 2.13 μm.