A simple new model for incoming solar radiation dependent only on screen-level relative humidity

Abstract

lobal incoming shortwave radiation (Rg) is the energy source for the majority of biogeochemical processes on Earth, as well as for photo-voltaic power production. Existing simple site-specific models to estimate Rg commonly use the daily range of air temperature as input variable. Here, we present a simple model for incoming short-wave radiation, requiring only screen-level relative humidity data (and site specific astronomical information). The model was developed and parameterized using high quality global radiation data covering a broad range of climate conditions. It was evaluated at independent sites which were not involved in the process of model development and parameterization. The mean 1:1 slope was 1.02 with an average r2 of 0.98. NRMSE averaged at 43%. Despite its simplicity, the new model clearly outperforms conventional approaches, and it comes close to more labor- and data-intensive alternative models.