Satellite estimates of surface ultraviolet A (UVA) (315–400 nm) from the Global Ozone Monitoring Experiment (GOME)‐2 were compared to ground‐based measurements at four stations in South Africa for 2015. The comparison of daily exposure and daily maximum irradiance was completed for all‐sky and clear‐sky conditions. There is a strong linear correlation between the satellite and ground‐based data with a correlation coefficient (r) between 0.86 and 0.97 for all‐sky conditions. However, at three of the stations the satellite data are underestimated compared to ground‐based data with a mean bias error (MBE) between −8.7% and −20.6%. A seasonal analysis indicated that there is a link between the bias in ground‐based and GOME‐2 UVA and cloud fraction. Factors such as aerosols, surface albedo, altitude and data resolution may contribute to the underestimations found at the three sites. These results indicate that satellite estimates of surface UVA over South Africa do not exhibit the same behavior as other stations around the world and therefore require further validation.

中文翻译：

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南非 GOME-2 UVA 卫星数据与地基 UVA 测量的比较

卫星对全球臭氧监测实验 (GOME)-2 的表面紫外线 A (UVA) (315–400 nm) 估计值与 2015 年南非四个站的地面测量值进行了比较。 每日暴露量和每日最大值的比较在全天和晴天条件下完成了辐照度。卫星和地面数据之间存在很强的线性相关性，全天条件下的相关系数 (r) 介于 0.86 和 0.97 之间。然而，与地面数据相比，其中三个站的卫星数据被低估了，平均偏差误差 (MBE) 在 -8.7% 和 -20.6% 之间。季节性分析表明，地面和 GOME-2 UVA 的偏差与云比例之间存在联系。气溶胶、地表反照率、海拔和数据分辨率可能导致在三个地点发现的低估。这些结果表明，卫星对南非地面 UVA 的估计与世界其他站点的表现不同，因此需要进一步验证。