O3 and NO2 fluxes over snow measured by eddy correlation

The fluxes of nitrogen dioxide and ozone, as well as supporting meteorological data, have been measured at a snow covered grassland field site in northern Colorado by eddy correlation. The fluxes of both species are small. The median surface resistance to ozone deposition is greatest during the morning and least during the afternoon. The nitrogen dioxide flux is generally downward overnight and during the morning and upward during the afternoon. Surface NO emissions are thought to strongly influence the observed NO2 flux. The median surface resistance to oxidant (Ox = O3 + NO2) deposition shows no pronounced diurnal variation, but is greater for aged snow (22.8 ± 8.95 cm−1) than for fresh snow (8.1 ± 4.9 s cm−1). Quoted error limits are one standard error of the estimate.