Evaluation of three model estimations of solar radiation at 24 UK stations

Meteorological station records often consist only of precipitation and air temperature data. There is therefore a need for appropriate methods to estimate solar radiation data to enable complete data set creation, by combining observed and estimated data. It is important to know the quality and characteristics of the estimates made in order to understand what impacts the data may have on the use to which they are put. This paper describes a detailed evaluation of the performance and characteristic behaviour of two air temperature based models and one sunshine duration conversion method of estimating solar radiation, for 24 meteorological stations in Britain. Comparisons were made using a fuzzy-logic based multiple-indices assessment system (Irad) and tests of the temporal distribution of mean errors over a year. The conversion from sunshine duration to solar radiation produces the best overall estimates, but shows systematic seasonal errors. The two air temperature based methods can be reliable alternatives when only air temperature data are available. Fundamentally, the study demonstrates the value and importance of using a range of assessment methods to evaluate model estimates.