Abstract
As part of the POLLUMET (Pollution and Meteorology in Switzerland) study, measurements of O3, NO2, and H2O2 were made at ground stations, by aircraft, and manned hydrogen balloons to characterize the photochemical processes prevailing during times of high ozone production. During summer smog episodes, elevated ozone concentrations were found over the whole area of the Swiss Plateau, which is a densely populated and industrialized region. However, NO2 concentrations were generally at a low level in the afternoon. An increase of hydrogen peroxide concentration in the mixing layer during photochemical episodes was observed. To understand better the photochemical processes which control ozone formation over the Swiss Plateau, calculations with the Harvard photochemical model and the Harwell photochemical trajectory model were conducted. A comparison of model results with measurements of the triad O3, NO2, and H2O2 indicates an ozone formation under low NOx conditions.
Highlights
The Swiss Plateau, located between the mountains of the Alps and the Jura, is a large, densely populated and industrialized valley (Figure 1)
IOP91 covered the buildup of a weak anticyclone and was confined to the region of Bern, the central part of the Swiss Plateau; it was aimed to gather a detailed cross section from the Jura Mountains to the Alps
To put things into perspective, we present the data from the rural station Schtipberg, northwest of the city of Bern, which we considerasrepresentativeof the regionalpollution over the Swiss Plateau
Summary
The Swiss Plateau, located between the mountains of the Alps and the Jura, is a large, densely populated and industrialized valley (Figure 1). Surface ozone levels exceed regularly the air quality standard (62 ppb, allowed to be exceeded once an hour within a year). In 1989 a coordinated research effort was started to investigate ozone formation over the Swiss Plateau. The program POLLUMET (pollution and meteorology) was centered around several intensive observation periods (IOPs) in the summer months. The objective of the IOPs was to identify the processesregulatingozone concentrations. In this studywe presentmeasurementsof 03, H202, NO2 concentrations, and meteorological parameters over the Swiss Plateau from the surface through the mixed layer to the troposphere above the boundary layer. The observationsare interpreted usingphotochemical modelsto determinethe regime for 03 production
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