RESISTANCES TO OZONE DEPOSITION TO A FLARK FEN IN THE NORTHERN AAPA MIRE ZONE

We present results df eddy covariance measurements of ozone deposition to a subarctic aapa mire. The measurements were performed in northern Finland in August-September 1995. The aim of the study is to quantify the ozone flux to this specific surface type and interpret the observ ations in terms of the resistance analogy model for dry deposition. Th e dry deposition velocity of ozone had a weak diurnal cycle, the hourl y means within this cycle ranging from 0.15 to 0.2 cm s(-1). The bulk surface resistance was on average about 400 s m(-1) during the daytime and 480 s m(-l) in the dark. The small day-to-night difference indica tes only a weak dependence on radiation. The independence of the subla yer Stanton number on flow, which is approximately valid for surfaces of permeable vegetation, was found to fail for the present surface, wh ich exhibits a pronounced hummock-hollow pattern. This adds to the unc ertainty in determining the surface resistance as a residual in the re sistance system. Comparisons of observations with two general-purpose parameterizations of the surface resistance indicate that these tend t o overestimate the light sensitivity of surface-related resistances. T he overall performance of these schemes much depends on the actual imp lementation with respect to land-use data and seasonal definitions.