Influences of atmospheric reanalysis on the accuracy of clear-sky irradiance estimates: Comparing MERRA-2 and CAMS

This contribution compares the influences of atmospheric reanalysis, in particular, Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) produced by NASA's Global Modeling Assimilation Office global reanalysis composition Copernicus Atmosphere Monitoring Service (CAMS), on accuracy clear-sky irradiance estimates. In terms output, comparison shows there exist great differences aerosol optical depth (AOD) Ångström exponent (AE) between two models. Based 58 sunphotometer stations, it is found that daily MERRA-2 AOD negatively biased with prominent underestimation western China. CAMS has considerable improvements eastern China against MERRA-2, which may be associated high-quality assimilation MODIS gas emissions, a timely consistent fashion. Both reanalyses tend to underestimate fine-dominated aerosols (AE > 1.6) while overestimating coarse-dominated ones < 0.8). irradiance, high-performance physical model called Reference Evaluation Solar Transmittance, bands (REST2) used as basis evaluation. The performance REST2-modeled horizontal (GHI) based products subsequently examined using data from 10 ground-based radiometry sites. It concluded clearness index GHI ( k tc ) computed show comparative over most parts China, though are exceptions. For instance, CAMS-based outperforms slopes closer unity, intercepts root mean square errors 0, can attributed AOD. accumulated ΔGHI (i.e., − changes linearly ΔAOD ), implying better quality advantages estimation. Therefore, recommended solar resource assessment applications albeit higher temporal resolution (1 h) coverage (from 1980 present). • Aerosol evaluated via data. Daily biased, performs much long-term