Temporal trends in surface irradiance at ultraviolet wavelengths

To clarify recent, conflicting results about temporal trends in surface ultraviolet (UV) irradiance, a study was undertaken of UVB (280–320 nm) and UVA (320–400 nm) at Atlanta, Georgia, from 1980–1984. Results indicate that, while Robertson‐Berger (UVB) “RB” meter readings decreased about 10% over the period, Eppley “TUVR” (UVA) readings increased about the same amount. These trends appear to be due not to changes in ozone or cloud cover, but to real effects on the RB data from changes in aerosol concentrations, and to calibration drift of the TUVR sensor. Implications of these results for long‐term monitoring of UV radiation are discussed.