Abstract
The estimation of global solar radiation (GSR) is important for the studies on photovoltaics, building design, and agriculture. In this study, we developed a GIS-based method for estimating hourly GSR. Firstly, this method estimated clear-sky GSR using a solar radiation model, which is integrated within the open source environment of the GIS. Then, a GSR estimating equations were derived from a maximum likelihood estimation between GSR observed by Japan Meteorological Agency (JMA) and some parameters ; clear-sky GSR, cloudiness, relative humidity, and surface pressure. This analysis utilized the cloudiness, relative humidity and surface pressure of numeric prediction data, which was calculated by JMA using mesoscale model. It was found that the GSR estimating equations should be derived for each month using monthly data and setting thresholds of a solar elevation because the effects of the cloudiness, relative humidity, and surface pressure on the atmospheric attenuation vary with a solar elevation. The monthly root mean square errors ranged approximately from 0.20 to 0.53 MJ/m2.
