Dependence of the OH concentration on solar UV

OH and the major parameters determining its concentration were measured during a field campaign in August 1994 at Mankmoos, a rural, relatively unpolluted site in northeastern Germany. The measured OH concentrations were previously shown to depend mainly on the intensity of solar UV and on the mixing ratio of NO 2 . In this paper we develop a simple parameterization of the dependence on solar UV and on NO 2 . The photolysis of O 3 to O 1 D , of NO 2 to NO, and of HCHO to HCO and H, all contribute significantly to the total dependence of OH on solar UV. We demonstrate that the photolysis frequency of O 3 , J O 1 D , is a suitable measure for that dependence which is slightly less than linear. The highly nonlinear dependence of OH on NO x is approximated by a Padé function. The parameterization provides a tool for a future quantitative intercomparison of the measured and modeled dependences of OH on UV and NO 2 . It also allows the removal of the variation in the measured OH induced by the dependences on the variables, UV and NO 2 , and thus enables a search for dependences on other, less influential parameters.