Boundary layer structure and photochemical pollution in the Harz Mountains—An observational study

Results from a field campaign that has been performed in summer 1993 to study photochemical pollution in the Harz Mountains, Germany, are presented. During a five-day, fair-weather period, a steady increase of the daily maximum ozone concentration up to values around 100 ppb was observed in the Harz region. The results of ozone measurements at two surface stations (404 m a.s.l. and 1142 m a.s.l., respectively) are discussed with respect to both the transport and dispersion conditions during the period and the local structure of the atmospheric boundary layer. Remarkable similarities in the time series of the ozone mixing ratio at the two places have been found which indicate some kind of quasi-homogeneity even over complex terrain. The trace gas concentrations at the top of Mt. Brocken, the highest summit of the Harz Mountains, are shown to be strongly influenced by vertical transports due to convection (at daytime) and subsidence of inversion layers (at nighttime).