Bibliogr. s. 19-21

Kraków, Poland, is a city with poor air quality, located in the large Wisła (Vistula) valley, and affected by afoehn wind from the Tatra Mountains. We analyzed 14 long episodes of the foehn from the periods Sep 2017- Apr 2018 and Sep 2018 - Apr 2019. Data used included measurements of (i.e. particulate matter withan aerodynamic diameter up to 10mm) concentrations) concentrations, air temperature and relative humidity,wind speed and direction from ground stations and mast measurements up to 100 m a.g.l., along with modelanalysis results. A non-operational configuration of the AROME CMC (the Application of Research toOperations at Mesoscale canonical model configuration) 1 km x 1 km was applied. A conceptual modelconcerning the impact of a foehn on urban air pollution was developed. The occurrence of a particular effectof a foehn on the spatial-temporal pattern depends on its mode of transfer through the city: a. a foehnflows above the valley where a strong cold air pool and a return flow can be found; b. a foehn enters thevalley from the eastern, wider part or from the valley top and destroys the cold air pool; c. gravity wavesgenerated by a foehn are strong enough to enter the western narrower part of the valley and cause largespatial differences in turbulence parameters within the city. The first transfer mode worsens air pollutiondispersion conditions throughout the city and leads to large increases in levels (from below 50 to 150-200 ), the second mode improves dispersion and leads to large decreases in levels (from 150-200 to below 50 ) throughout the city, and the third generates large spatial differences in levels (50-70 ) within the city. There is no single effect of a foehn on air pollution dispersion conditions.