Vector‐Geometry Approach to Account for Local Topographic Effects on Surface Solar Radiation

The spatial distribution of surface solar radiation is affected by local topography, the effects particularly significant in mountainous areas. On a continuous topographic surface, its mathematical analysis is feasible by calculating the aspect and inclination angles. However, with the digitized topography data used in practice, the calculation involves numerical errors. This study proposes an approach based on vector geometry to simulate solar irradiance for eight triangular facets constructed within each digitized cell. This facet‐based method offers a more refined representation of terrain characteristics compared to conventional gradient‐based techniques. The proposed method is evaluated using a synthetic topography defined by the Gaussian function and the simulated irradiance patterns well agree with analytical solutions. In further evaluation with real mountainous terrains, the results derived at quadruple resolution from low resolution topography data successfully reproduce features in the high resolution topography.