H15-143: Evaluation of the HIRLAM and HARMONIE numerical weather prediction models during an air pollution episode

We analyse the severe air quality episode in the Istanbul Metropolitan Area during 18-20 November 2009 using the HIRLAM and HARMONIE numerical weather prediction models and the HYSPLIT trajectory model. The HYSPLIT trajectory model result shows that the sources of this episode were local. The weather situation leading to this episode is analysed using meteorological observations. During the episode, a high pressure system over northwest Turkey, including Istanbul, led to the formation of an exceptionally strong ground-based temperature inversion which, combined with the low temperature and the heating, led to increased pollution levels.