A Comparison of ARCGIS modelled and ground recorded solar radiation data and opportunities for utilisation in environmental models

Incoming solar radiation is modified as it travels through the atmosphere and is further modified by topography and surface features. Since radiation can be greatly affected by topography and surface features, a key component of the calculation algorithm requires the generation of an upward-looking hemispherical viewshed for every location in the digital elevation model (DEM). This is one of the reasons why GIS based solar radiation models are increasing in popularity. ARCGIS 9.3 has a solar radiation calculation tool based on the models developed by Fu and Rich (2000, 2002). Solar radiation is a critical driver of many processes on the earth’s surface. GIS-based solar radiation models allow us to take into account, on a fine scale, the complexity of the interactions between the incident solar radiation and the local topography. Such models provide rapid, cost-efficient and accurate estimations of radiation over large areas, while considering slope and aspect gradients, and shadowing effects. To test the performance of the ARCGIS based solar radiation model we obtained data for 4 different sites in Australia and compared this data with modelled radiation using DEMs from these same sites. This paper discusses the correlation between the modelled radiation and the actual recorded data and presents methods of developing regression equations that can be used to convert modelled radiation for use in other environmental models that utilize field recorded solar radiation data. Our analysis of daily meteorological records spanning eight years for a number of stations around Australia show that the correlations between recorded and ARCGIS modelled radiation are quite high (as high as 0.99 for some stations) and that, with sufficient screening, modelled data can safely be converted and used in environmental models that require actual field data.