South Africa has been measuring the ground-based solar UV index for more than two
decades at six sites to raise awareness about the impacts of the solar UV index on human health.
This paper is an exploratory study based on comparison with satellite UV index measurements
from the OMI/AURA experiment. Relative UV index differences between ground-based and
satellite-derived data ranged from 0 to 45% depending on the site and year. Most of time,
these differences appear in winter. Some ground-based stations’ data had closer agreement with
satellite-derived data. While the ground-based instruments are not intended for long-term trend
analysis, they provide UV index information for public awareness instead, with some weak signs
suggesting such long-term trends may exist in the ground-based data. The annual cycle, altitude,
and latitude effects clearly appear in the UV index data measured in South Africa. This variability
must be taken into account for the development of an excess solar UV exposure prevention strategy.