Trends in Surface Ultraviolet Radiation

Because of the strong absorption of ultraviolet (UV) radiation starting at 320 nm by 03, one of the major impacts of decreased stratospheric ozone is expected to be increased UV at the earth s surface, with associated effects such as increases in skin cancer and cataracts and damage to plants and other ecosystem components. It has therefore been of great interest to determine whether such a relationship can be detected and, if so, what the magnitude of the effect is. The latter is commonly expressed as an amplification factor (AF) or radiation amplification factor (RAF), defined as the fractional change in radiation (R) per fractional change in total column ozone (03)  

The ultraviolet region is commonly divided into the UV-A region from 315 to 400 nm and the UV-B region from 280 to 315 nm. It is the UV-B region that is of greatest concern in terms of the impacts of UV radiation, and because of the strong absorption of light by 

FIGURE 13.15 Normalized action spectra taking response = 1.0 at 300 nm (adapted from Madronich, 1992). 

Toumi et al. (1994) also suggested there is a feedback between reduced stratospheric ozone and particles in that the increased UV due to ozone depletion may increase sulfate particle formation by increasing the concentrations of tropospheric OH. 

In short, changes in aerosol concentrations over industrialized regions can complicate the interpretation of UV trends (e.g., see Justus and Murphey, 1994). The same is true of clouds, which play a major role in the 

---