Extinction of UV-visible radiation in wet midlatitude (maritime) snow: Implications for increased NOx emission

The snowpacks were found to have greater UV penetration depths than polar (tundra) snowpacks and consequently may release more NO2 gas to the atmosphere during the photolytic destruction of nitrate anions in the snowpack for a given spherical irradiance. Fluxes of NO2 to the troposphere as a result of NO3- photolysis were calculated for different measured e-folding depths using tropospheric ultraviolet-visible (TUV)-modeled actinic flux data assuming all the NO2 can leave the snowpack and the photolysis of nitrate is the rate-limiting step.

These calculated fluxes ranged from 3.3 to 7.6 kg km(-2) yr(-1) (assuming 150 days of snow cover a year), significantly more than polar snowpacks by a factor of 4-10. The fieldwork measured liquid equivalent e-folding depths of 3.74-14.66 cm (e-folding depths of 7.25-32.4 cm(-1)) at four sites in the Cairngorm mountain range, Scotland (57 degrees 07 ' N, 3 degrees 40 ' W), during the winter of 2003. The wavelength range studied was 300-450 nm.