Assessment of a three dimensional model for atmospheric radiative transfer over heterogeneous land cover

A three‐dimensional (3D) atmospheric radiative transfer model that explicitly represents surface albedo heterogeneity is tested against a one‐dimensional model and surface irradiance observations in a polar region where land cover heterogeneity is high. For observations located near high latitude coastlines, the contrast between the highly absorbing ocean and reflective snow surface creates spatial heterogeneity, or a 3D effect, around the observation site. The resulting effect on radiation at the sensor should be taken into account when using a solar radiative transfer model to interpret measurements. This assessment shows that better closure is obtained with a three‐dimensional model (≤5%) versus a plane‐parallel model (≤7%). The importance of the surface 3D effect increases with aerosol or cloud optical depth and with surface albedo contrast. The model used here can be implemented at any surface site given the surrounding land cover properties.