Modelling daily topographic solar radiation without site-specific hourly radiation data

This paper proposes a model to estimate absolute values of daily solar radi ation intercepted by topographic surface, without site-specific hourly radi ation data. Instead, daily amounts of global and diffuse radiation at the h orizontal surface under unobstructed sky are used. These amounts can be sim ply and accurately estimated (as monthly averages) in terms of latitude, el evation, and relevant but easily accessible climatic parameters. Hourly val ues of direct irradiance are substituted here by the hourly portions of the unknown daily total as a function of actual and daily maximum solar elevat ion. The presented approach simplifies ecological application of topographi c solar radiation models, especially for research of the spatial distributi on of vegetation and ecosystem types. (C) 1998 Elsevier Science B.V. All ri ghts reserved.