Fluxes of ozone and nitrogen dioxide measured by Eddt correlation over a harvested wheat field

Flux measurements of O3 and NO2 were made at Scherzheim in the so-called nested area of the TRACT experiment. The nested area consisted mainly of agricultural terrain with patches of forest. The flux measurements at Scherzheim were made by applying the eddy-correlation technique over a field which had been harvested and then covered with re-grown wheat. The total resistance to deposition was calculated and subdivided into aerodynamic, laminar boundary-layer and surface resistance. The results were related to diffent fetch conditions. A clear diurnal variation was found for fluxes as well as deposition velocities and resistances which indicated stomatal activity as a regulating factor. The fluxes were highest during the early afternoon with maximum fluxes of −0.6 μg O3 m−2 s−1 and −0.2 μg NO2 m−2 s−1. The average daily maximum deposition velocity of O3 was 0.5cm s−1 and of NO2 0.35 cm s−1. Surface resistances (rc) to O3 uptake were up to 600 s m−1 during nighttime and 200 s m−1 during daytime. rc’s to NO2 were even higher; 800–1000 s m−1 during the night and 200–400 s m−1 during the day.