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

Measured air pollution concentrations in a city reflect the influence of di fferent kinds of sources as well as varying meteorological conditions. In t he city of Graz in southern Austria, frequent stagnant meteorological condi tions can cause elevated levels of air pollution although emission levels a re not exceptionally high. With the aid of a detailed emission inventory an d an array of sodars and tethersondes as well as lidar systems supplementin g the routine meteorological and air chemistry network during a field exper iment in January 1998, the daily variations of air pollution concentrations of selected components within the complex topography of the city of Graz a re 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. Co ncerning NOX the fast reaction from NO to NO2 is important due to the down- mixing of O-3 from the residual layer. The maximum in the afternoon is infl uenced by emission rates and pollution transport due to the mountain wind.