Estimation of solar radiation in Australia from rainfall and temperature observations

This study evaluated the accuracy of several models for estimating daily so lar radiation (Q) across Australia. Data from 39 sites were taken from MetA ccess. The sites were grouped into four climatic zones. Coefficients of nin e models, including two newly developed formulae, were fitted for the 39 si tes. Correlation coefficients (R-2) between estimated Q and measured Q and root mean squared error (RMSE) associated with the estimates were calculate d. It was concluded that models which expressed rainfall as a binary quanti ty (1 for rainfall > 0; 0 for rainfall = 0) performed better than those usi ng amount of rainfall (precipitation in mm). The best performed models, one using temperature data only, one using rainfall data only and one using ra infall and temperature were further evaluated. A newly developed model that included temperatures (minimum and maximum) and rain-day information prove d the best method. Using the coefficients for estimates of Q at the same si tes, averaged R-2 was 0.68, 0.74 and 0.79 and RMSE was 3.24, 3.05 and 2.89 MJ m(-2), for the model using rainfall only, temperature only and both rain fall and temperature, respectively. When Q was estimated using the coeffici ents from other sites, estimation of Q within eastern and southern zones we re more reliable than in northern and central zones. In general, the model using both temperature and rainfall was the best mode l for either estimated Q for the site where coefficients of the model were developed at the site or imported from other sites. However, in some tropic al coastal sites of Australia, such as Broome and Darwin, estimates of Q ba sed on rainfall only can be more reliable when the coefficients were import ed from other sites. It was concluded that radiation within a similar clima tic region could be well estimated with no local recording, regardless of d istance between sites. (C) 2001 Elsevier Science B.V. All rights reserved.