Analysis of the daily variations of wintertime air pollution concentrations in the city of Graz, Austria

Abstract

Measured air pollution concentrations in a city reflect the influence of different kinds of sources as well as varying meteorological conditions. In the city of Graz in southern Austria, frequent stagnant meteorological conditions can cause elevated levels of air pollution although emission levels are not exceptionally high. With the aid of a detailed emission inventory and an array of sodars and tethersondes as well as lidar systems supplementing the routine meteorological and air chemistry network during a field experiment in January 1998, the daily variations of air pollution concentrations of selected components within the complex topography of the city of Graz are explained. Main results show the almost linear dependence of the morning maximum concentrations on the predicted emission rates. Throughout the day the rising of the well mixed layer reduces concentrations considerably. Concerning NO(x) the fast reaction from NO to NO2 is important due to the down-mixing of O3 from the residual layer. The maximum in the afternoon is influenced by emission rates and pollution transport due to the mountain wind.