Accurate estimations of clear-sky direct normal irradiance (DNIcs) and diffuse horizontal irradiance (DIFcs) are crucial in solar resources assessment. This study examines 95 and 88 popular clear-sky irradiance models for their worldwide estimation capability of DNIcs and DIFcs, respectively. Atmospheric inputs are from MERRA-2 reanalysis and irradiance observations for validation are extracted from 100 ground stations across five major Köppen-Geiger climate zones. They consist of 24 million 1-min measurements of DINcs and 18.7 million 1-min measurements of DIFcs after quality control and clear-sky detection, during the 5-year period 2015–2019. Using principal component analysis, the performance of each clear-sky irradiance model is ranked separately among the five climate zones, as well as given a global rank. For the Equatorial, Arid, Temperate, Cold and Polar climates, it is found that Heliosat1-I, ESRA-I, REST2v9.1, REST2v9.1 and CLS, respectively, are the best DNIcs models, while Modified Iqbal-C, Heliosat1-R, Calinoiu, Modified Iqbal-C and PSI-REST are the best DIFcs models. On a global worldwide basis, the three top-ranking models are REST2v9.1, REST2v5 and MMAC-V2 for DNIcs, and Modified Iqbal-C, PSI-REST and MRMv5 for DIFcs. The results and rankings presented are strictly relative to MERRA-2 input data, and should not be extrapolated to results from alternate sources of atmospheric data. This detailed validation exercise revealed inconsistent performance of many models across different climates, possibly due to insufficient training and/or over-fitting of empirical relationships. Codes of all clear-sky irradiance models in the public domain are available online on the Github repository JamieMBright/clear-sky-models.

晴空直接法向辐照度（DNIcs）和水平漫射辐照度（DIFcs）的准确估算对于太阳能资源评估至关重要。这项研究分别检查了95种和88种流行的晴空辐照度模型在全球范围内对DNIcs和DIFcs的估计能力。大气输入来自MERRA-2再分析，辐照度观测值是从五个主要柯本气候区的100个地面站提取的，以进行验证。在2015-2019的5年期间，经过质量控制和晴朗天空检测，包括2400万次1分钟的DINcs测量和1870万次1分钟的DIFcs测量。使用主成分分析，每种晴空辐照度模型的性能在五个气候区之间分别进行排名，并获得全球排名。对于赤道，干旱，温带最好的DNIcs模型是Heliosat1-I，ESRA-I，REST2v9.1，REST2v9.1和CLS，而改良的Iqbal-C，Heliosat1-R，Calinoiu，改良的Iqbal-C和PSI-REST是最佳的DIFc。楷模。在全球范围内，三个顶级模型分别是用于DNIcs的REST2v9.1，REST2v5和MMAC-V2以及修改后的Iqbal-C，PSI-REST和MRMv5用于DIFc。给出的结果和等级严格来说是相对于MERRA-2输入数据而言的，不应推断为来自其他大气数据来源的结果。这项详细的验证工作表明，在不同气候下，许多模型的性能不一致，这可能是由于训练不足和/或经验关系过拟合造成的。公共领域中所有晴空辐照度模型的代码都可以在Github存储库JamieMBright / clear-sky-models上在线获得。