Abstract: Daily solar radiation is a very important parameter in earth science, agriculture science, and other fields. However, compared with the conventional meteorological observatory, there were few observatories of the global radiation. Therefore, the estimation of solar radiation had become a focus. Five representative models, such as Angstrom-Prescott model, Ogelman model, Bahel model, the comprehensive model of sunshine duration and diurnal temperature range, and Liu’s model (named model I to V), were used to estimate solar radiation in this paper, under the analysis and comparison previous solar radiation estimation models. Daily observation solar radiation data (from 2001 to 2010) of six representative stations in Northern China Plain were used to compare the effect of five models, according to the whole analysis period (about 10 years), different seasons, and weather conditions. The results showed that: (1) in each representative station, simulated values of five models had an extremely significant positive correlation between the measured values (P≤0.01), the correlation coefficient (R) were above 0.93, the mean absolute percentage error (MAPE) were within 9.68%-17.56%, and the normalized root mean square error (NRMSE) were within 12.47%-23.12%. The simulation results mostly were "good", individual as an "acceptable". Five models and the corresponding coefficient showed high accuracy in estimating the solar radiation in Northern China. (2) During the whole analysis period, the average value of MAPE (AMAPE) of five models were 14.28%, 14.93%, 12.78%, 12.27%, and 13.01%, respectively, corresponding to the average value of NRMSE(ANRMSE) were 18.80%, 19.71%, 17.09%, 16.27%, and 17.24%, respectively, indicating all of the simulation results were "good". Model IV was the best, following by model III and V. (3) In spring, AMAPE of five models were 11.97%, 12.19%, 11.17%, 10.86%, and 11.24%, respectively, corresponding to ANRMSE were 15.46%, 15.75%, 14.27%, 13.95%, and 14.27%, respectively. In summer, AMAPE of five models were 14.46%, 15.47%, 13.32%, 12.45%, and 13.36%, corresponding to ANRMSE were 18.89%, 20.21%, 17.21%, 16.22%, and 17.05%, respectively. In autumn, AMAPE of five models were 14.81%, 15.65%, 12.67%, 12.19%, and 12.20%, corresponding to ANRMSE were 18.94%, 20.00%, 16.66%, 15.94%, and 15.95%, respectively. In winter, AMAPE of five models were 18.08%, 18.56%, 15.19%, 14.99%, and 14.11%, corresponding to ANRMSE were 22.52%, 23.28%, 19.42%, 19.06%, and 18.31%, respectively. In general, most simulation results were "good", individual was "acceptable", in the four seasons. Model IV showed best in spring, summer, and autumn, while model V showed best in winter, following by model IV. (4) Under the condition that sunshine duration existed, AMAPE of five models were 11.23%, 12.03%, 9.52%, 9.32%, and 9.94%, respectively, corresponding to ANRMSE were 14.92%, 15.92%, 12.75%, 12.44%, and 13.13%, respectively. All of the simulation results were "good", model IV showed best. In contrast, without sunshine duration, AMAPE of five models were 49.25%, 47.92%, 49.71%, 46.03%, and 45.51%, respectively, corresponding to ANRMSE were 61.92%, 62.09%, 61.89%, 58.02%, and 55.70%, respectively. All of the simulation results were "bad". In summary, five models could be used to estimate the daily solar radiation in Northern China Plain, and model IV (the comprehensive model of sunshine duration and diurnal temperature range) showed the highest accuracy.

Key words: Solar radiation estimation, Angstrom-Prescott model, Bahel model, Northern China Plain