Diurnal courses of ozone in an inner urban park

Abstract

The aim of the investigation was the analysis of diurnal courses of O3 concentrations in a large inner urban green area. For that purpose, 10 field experiments with durations of up to 54 hours were carried out in the Grugapark (70 ha) in the city of Essen (Ruhr, Germany) between May 1995 und August 1996 during calm clear weather conditions in summer. 50 % of the diurnal courses showed two O3 maxima. In the daytime the O3 concentrations were higher than at reference stations at the outskirts on the leeside of Essen and in the highlands (Eifel) in 30 % of the cases. The observed nocturnal O3 maxima occurred during stable atmospheric conditions in the second half of the night. Distinct increases in air temperature of up to 3 K near the surface were found at the same time. This is an indication of vertical O3 transport from the urban residual layer to the ground level, which may be induced by increased turbulence after the development of a nocturnal low-level jet. The horizontal transport of O3-rich air masses from the cooler rural area by a country breeze can be excluded in this connection.

Keywords

• grugapark
• essen
• germany
• o₃
• atmospheric conditions
• ozontagesgänge
• urbane grünfläche