A Method for Estimating Global Solar Radiation from Daily Maximum and Minimum Temperatures: its Applicability to Japan

Abstract

Though hydrological models often require solar radiation as input data, solar radiation observations are not so common as temperature and precipitation observations. Therefore, there are many methods for estimating the solar radiation including methods for estimating solar radiation from daily maximum and minimum temperatures. We investigated applicability and accuracy of this method to Japan using Japan Meteorological Agency measurement data, and obtained the following three conclusions. (1) When determining model parameters A and C based observed solar radiation data for each site, model estimation showed nearly no bias with RMSE = 4.40 MJ m^-2 day^-1. (2) When A and C cannot be determined due to absence of observed solar radiation data, assuming A = 0.76, C and C = 2.2 is recommended in Japan. (3) The accuracy based on the method is comparable to that substituting solar radiation data at an observation point ca. 200 km far from the site, indicating the method is useful when solar radiation data within ca. 200 km from the site are available.