A new simple method for estimating monthly and daily solar radiation. Performance and comparison with other methods at Lleida (NE Spain); a semiarid climate

A simple new method is proposed for estimating relative sunshine duration a nd solar irradiance on both a monthly and daily basis. The method requires the occurrence of precipitation. and maximum and minimum air temperatures a s input. Comparisons with two other published simple methods: Bristow and C ampbell (1984); and Hargreaves et al. (1985), and a modified version of the method proposed by McCaskill (1990), were conducted for a weather station at Lleida (NE Spain), which has a continental semiarid climate. The new met hod performed slightly better than the others mentioned above, mainly as a result of a reduction in errors when estimating cases of high solar radiati on.