Comparison of GOME-2 UVA Satellite Data to Ground-Based Spectroradiometer Measurements at a Subtropical Site

The ultraviolet A (UVA) (315-400 nm) daily exposures and maximum daily irradiances from the Global Ozone Monitoring Experiment (GOME)-2 satellite have been compared over three years to the corresponding data from a groundbased spectroradiometer for a subtropical Southern Hemisphere site. This is one of the first such comparisons for the GOME-2 UVA waveband in the Southern Hemisphere. For the UVA daily exposures and the maximum daily irradiances, the comparisons were undertaken for all sky conditions and for cloud-free conditions. Under cloud-free conditions the R
²
of the fit regression line for the comparisons was 0.93 for the exposures and the irradiances. The influence of cloud reduced the R
²
values to 0.86 and 0.70 for the daily exposures and maximum irradiances, respectively. The relative root-mean-square error (rRMSE), mean absolute bias error (MABE), and mean bias error (MBE) for the maximum daily UVA irradiances on the cloud-free days were 0.08, 6.59 ± 7.32%, and -1.04 ± 9.83%, respectively. Similarly, for the daily UVA exposures on the cloud-free days, the rRMSE, MABE, and MBE were 0.10, 5.19 ± 6.42%, and -0.79 ± 8.24%, respectively. For the all-sky conditions, the corresponding values were 0.20, 15.23 ± 14.90%, and -0.79 ± 8.24% for the maximum daily irradiances and 0.19, 14.17 ± 14.56%, and -4.63 ± 20.60% for the daily exposures. In all studies of the influence of UVA on human health, this can complement ground-based measurements that provide the higher temporal and spatial resolution available only at a limited number of surface monitoring sites.