The Austrian city of Graz at the south-eastern edge of the Alps frequently
experiences wintertime stagnations during anticyclonic flow conditions, lea
ding to high local concentrations of primary pollutants. This paper investi
gates the dominant three-dimensional local flow structures in the Graz regi
on during a representative January stagnation period in 1998 using data obt
ained from a field experiment that supplemented the routine meteorological
network with an array of sodars and tethersondes and a meteorological tower
. Important modifications to the temperature and wind fields over Graz and
its surroundings are attributed to both topographical and urban effects. Th
e main modifications to the along-valley wind system in the Mur valley that
runs through Graz from north to south are caused by nearsurface temperatur
e field differences between a warmer north and a cooler south part of the c
ity and the regular development of a nighttime down-valley low-level jet an
d its upward lifting when crossing the city centre.