Modeling Ultraviolet Radiation at the Earth's Surface. Part I: The Sensitivity of Ultraviolet Irradiances to Atmospheric Changes

Abstract

A discrete-ordinate radiative transfer model is employed for the prediction of surface UV irradiances. A wide-ranging sensitivity study is undertaken to show how changes to the model input parameters aged UV irradiances at the surface. The effects of surface albedo, surface pressure, aerosol, cloud, and ozone on the UV irradiances are examined as well as the effects of model resolution. The ozone vertical profile and the temperature of the ozone layer are found to strongly influence UVB (280?320 nm) surface irradiances; the irradiance at 305 nm can be changed by as much as 17% for a fixed amount of total column ozone. The surface albedo is found to have a maximum influence on wavelengths near 320 nm; an uncertainty in the surface albedo of 0.2 leads to an 8% error in the UVB prediction. Clouds and tropospheric aerosol decrease the UV, their influence depending little on wavelength. Stratospheric aerosol is shown to be able to enhance the midwinter UVB surface irradiances while decreasing the UVA (320?400 nm) surface irradiances.