Exploring the urban boundary layer by sodar and tethersonde

The Austrian city of Graz at the south-eastern edge of the Alps frequently experiences wintertime stagnations during anticyclonic flow conditions, leading to high local concentrations of primary pollutants. This paper compares instrument performance during a representative January stagnation period in 1998 in the Graz region using data obtained from a field experiment that supplemented the routine meteorological network with an array of sodars and tethersondes and a meteorological tower. Although sodars are known to give reliable estimates of the horizontal wind in most cases, direct comparisons to other instruments for verification are still not very frequent. Therefore, the performance of the sodars to detect important modifications to the wind field over Graz will be discussed and compared to that of the tethersondes and the tower.