This study evaluates the accuracy of three widely used solar radiation datasets(NASA
Solargis
and Meteonorm)for solar resource assessment in China. The evaluation is conducted by comparing their monthly global horizontal irradiance (GHI) estimates against high-quality ground-based measurements from 99 meteorological stations across China. A comprehensive index-based evaluation framework was established to identify the optimal datasets for each region and derive corresponding error correction coefficients. The results show that the spatial distributions of GHI from Solargis and Meteonorm align more closely with observations than those from NASA. The most significant discrepancies are observed in Northwest China
Xizang and Sichuan Province. Error analysis indicates that Meteonorm achieves the highest correlation coefficient () ( ≥ 0.98 at 75% of the stations) and the smallest error accounting for all error metrics
including root mean square error
mean absolute error
and mean relative error. Solargis demonstrates moderate accuracy
while NASA exhibits the largest error. A significant correlation is identified between latitude and mean relative error. Solargis tends to overestimate GHI at lower-latitude and underestimate at higher latitudes
whereas Meteonorm displays the opposite trend. Based on the results of error analysis
this study constructs a comprehensive index evaluation method
screens out the optimal data types of 99 stations
and spatially interpolates them to the national scale. The findings suggest that Meteonorm is preferred in 55% of China’s regions
followed by Solargis in 27% and NASA in 18%. The mean relative error of the optimized dataset is confined to a range of -4.5% to 5.9%. To improve the accuracy of solar energy assessments
the following calibration is recommended: GHI values should be increased by 1%-5% in northern regions
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