"NASA produces daily satellite-based data for ambient UV-R. The UV index captures the
strength of radiation at a particular location, and it is available in the form of geographic grids
and daily rasters with pixel size of 1◦ latitude by 1◦ longitude." (Anderson et al. (2016), p. 1339)
Used by Anderson et al. (2016), who show that the average of 1990 and 2000 values at the country level correlates with per capita income in 2004 conditional on latitude and many other controls.