Impact of clouds and aerosols on photolysis frequencies in Tropical and Polar atmospheres

Clouds and aerosols can have a significant impact of solar UV actinic flux. This study examines two extremes in aerosol impacts, the relatively pristine Antarctic troposphere and the polluted Mexico City boundary layer. The insitu photolysis frequency measurements using the NCAR Scanning Actinic Flux Spectroradiometer (SAFS) was compared to the Total Ultraviolet and Visible (TUV) radiative transfer model. The model inputs included the total ozone column (from satellites and ozone sonde measurements) and aerosol optical depths (from sun photometers and satellites). These photolysis frequency measurement to model intercomparisons also examine the uncertainies in both the SAFS measurement and TUV model, as well as the sensitivity of the TUV model to the aerosol inputs, and surface albedo changes in Antarctica.