Field Data and Model Calculations for the Hydroxyl Radical

Abstract Locally measured tropospheric OH concentrations are compared with model calculations to study the influence of chemical precursors and sunlight. The chemical scheme was taken from the gas phase reaction mechanism of the Regional Acid Deposition Model, which includes an explicit inorganic and a comprehensive organic chemistry. The experimental investigations probed planetary boundary layer air in two sets of campaigns. In Deuselbach (1983) and Schauinsland (1984) rural conditions were encountered with NOx concentrations on the average of 2.2 ppb and 0.9 ppb, respectively. This dataset was already compared with model results based upon an older and less detailed chemical reaction scheme (Perner et al.). Since then, the experimental data were reanalyzed leading to modified measured OH concentrations and also to modified precursor concentrations. For a consistent comparison with the more recent campaigns in Julich (1987 and 1988) the calculations have been redone. The modeled and experimental OH conc...