1. 165871 Dispersion conditions in complex terrain - a case study of the January 2010 air pollution episode in Norway Viel Ødegaard Norwegian Meteorological Institute Aftenposten

2. Viel Ødegaard, Norwegian Meteorological Institute met.no

8. Temperature at different elevations

9. Viel Ødegaard, Norwegian Meteorological Institute met.no Near surface temperature gradient observations

10. Viel Ødegaard, Norwegian Meteorological Institute met.no 10 m wind, observed

11. Viel Ødegaard, Norwegian Meteorological Institute met.no Operational air quality forecasting UK Met Office Unified Model –1 km horizontal resolution –38 vertical levels, lowest level wind 10 m, T and q 20 m –Non-hydrostatic –9 surface tiles, urban: rough concrete approach –Convection and orographic roughness parameterizations turned off –Experimental runs with 0.33 km horizontal resolution dispersion model and emission data base (AirQUIS) Offline – hourly data on 10 model levels: u,v,T,q – Tsurf, clouds, precipitation, fluxes, BL height daily forecasts for day 2 during winter months

12. Viel Ødegaard, Norwegian Meteorological Institute met.no Surface energy balance

13. Viel Ødegaard, Norwegian Meteorological Institute met.no

16. Model temperature profiles (UM 1km)

17. Viel Ødegaard, Norwegian Meteorological Institute met.no Oslo Bergen Comparing temperature in the free atmosphere with 2m temperature at same elevation

18. Viel Ødegaard, Norwegian Meteorological Institute met.no Model near surface inversion

19. Viel Ødegaard, Norwegian Meteorological Institute met.no 2d trajectories lowest level

20. Viel Ødegaard, Norwegian Meteorological Institute met.no 2d trajectories lowest level

21. Viel Ødegaard, Norwegian Meteorological Institute met.no 2d trajectories lowest level

22. Viel Ødegaard, Norwegian Meteorological Institute met.no 10 m wind

23. Viel Ødegaard, Norwegian Meteorological Institute met.no Lowest level wind speed blue: > 2 m/s red: < 2 m/s 1 km resolution 0.33 km resolution

24. Viel Ødegaard, Norwegian Meteorological Institute met.no Summary Observing –Large scale persistent ridge/high pressure –Strong near surface inversion confined to level below 8 (10) m –Large temperature increase from low to high elevated stations –Low wind speed –Significant local variations in wind speed and direction with the same large scale forcing Successfully modeling –Inversion evolution –Drainage flow –Recirculation –Local wind variations provided high enough resolution

25. Viel Ødegaard, Norwegian Meteorological Institute met.no Thank you for your attention Acknowledgement to Leiv Håvard Slørdal at the Norwegian Institute for Air Research