Abstract
To achieve high-quality surface solar radiation (SSR) data for climate monitoring and analysis, the two satellite-derived monthly SSR datasets of CM SAF CLARA-A2 and SARAH-E have been validated against a homogenized ground-based dataset covering 59 stations across China for 1993–2015 and 1999–2015, respectively. The satellite products overestimate surface solar irradiance by 10.0 W m−2 in CLARA-A2 and 7.5 W m−2 in SARAH-E on average. A strong urbanization effect has been noted behind the large positive bias in China. The bias decreased after 2004, possibly linked to a weakened attenuating effect of aerosols on radiation in China. Both satellite datasets can reproduce the monthly anomalies of SSR, indicated by a significant correlation around 0.8. Due to the neglection of temporal aerosol variability in the satellite algorithms, the discrepancy between the satellite-estimated and ground-observed SSR trends slightly increases in 1999–2015 as compared to 1993–2015. The seasonal performance of the satellite products shows a better accuracy during warm than cold seasons. With respect to the spatial performance, the effects from anthropogenic aerosols, dust aerosols and high elevation and snow-covered surfaces should be well considered in the satellite SSR retrievals to further improve the performance in the eastern, northwestern and southwestern parts of China, respectively.
Highlights
High-quality surface solar radiation (SSR) data is highly demanded to meet the growing needs for solar energy applications [1], the accurate estimation of the radiation budget [2,3], hydrological processes [4,5] and carbon cycle [6,7]
A better performance regarding accuracy is shown in the geostationary satellite-based SARAH-E with higher spatial and temporal resolution as compared to CLARA-A2
Averaged over all 59 stations used in this study, the comparison shows an overestimation of 10.0 W m−2 by CLARA
Summary
High-quality surface solar radiation (SSR) data is highly demanded to meet the growing needs for solar energy applications [1], the accurate estimation of the radiation budget [2,3], hydrological processes [4,5] and carbon cycle [6,7]. Uncertainties, still exist in the observed global dimming and brightening phenomena, due to the limitations in the surface-based measurements [9]. Besides possible instrumental and operational issues, ground observations are sparse and not evenly distributed, especially over oceans, remote or sparsely populated areas and mountainous regions with complex terrain [10,11]. An inhomogeneity issue in the ground-observed SSR trend has been noted in China, especially during the 1990–1993 period and in the Tibet region with high elevations [12]. Around three quarters of the stations are located in urban areas, indicating a non-negligible urbanization effect on the derived trends in China [13]. To compensate for the limited spatial representation of ground observations, one effective alternative has been offered by satellite products due to their unique geographical coverage and high spatial resolution [14,15,16]
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