Radiative transfer in the summertime Arctic

This study used data from FIRE ACE and SHEBA with an explicit radiative transfer model to explore the effects of inhomogeneous cloud and surface properties on solar and longwave radiative transfer in the summertime Arctic. Three representative cases were selected from three flights in May and July 1998, with a detailed specification of cloud, surface, atmospheric, and aerosol properties. Results show that the surface inhomogeneity affects the fluxes at small scales but not in the domain average. The independent pixel approximation (IPA) and plane-parallel approximation (PPA) can produce accurate domain-average fluxes for low Arctic clouds, although the IPA can create large local errors. Measured and modeled fluxes are reasonably well matched, within the bounds of uncertainty in the model inputs, of which surface albedo has the largest impact. The fluxes are also sensitive to cloud liquid water path, cloud droplet effective radius, and aerosol amount.