Simulations of wintertime inversions in northern European cities by use of NWP-models. Erik Berge1, Ari Karppinen2, Jaakko Kukkonen2, Morten Ø. Køltzow1 and Leiv Håvard Slørdal3. 1The Norwegian Meteorological Institute, 2Finnish Meteorological Institute, 3The Norwegian Institute for Air Research