On the Effects of the Temporal and Spatial Sampling of Radiation Fields on the ECMWF Forecasts and Analyses

Abstract The author’s explore the implications of the temporal and spatial sampling of the radiation fields and tendencies upon the fields produced by the ECMWF system in operational-type forecasts, four-month seasonal integrations, and analyses. The model is shown to be much more sensitive to economies in the temporal than in the spatial description of the cloud–radiation interactions. In 10-day forecasts, the anomaly correlation of geopotential shows little sensitivity to a more complete representation of the cloud–radiation interactions, but temperature errors display a stronger dependence on the temporal representation. The difference increases with height, particularly in the tropical areas where interactions among convection, clouds, and radiation dominate. In pointwise comparisons over five days, the approximate temporal representation introduces only small differences in total cloudiness, surface temperature, surface radiation, and precipitation. In four-month seasonal simulations, the small error...