Mesoscale Circulations over the Athens Metropolitan Area during the 2004 Summer Olympic Games

During the Athens Olympics in the summer of 2004, NCAR operated a real-time mesoscale data-assimilation and forecast system that provided weather analyses and forecasts on a variety of scales, from the area of the eastern Mediterranean down to the urban scale of Athens. The meteorological situation was challenging because the irregular coastline and associated land-sea breezes are significantly affected by complex local topography and land-use characteristics. In addition, the model needed to properly simulate the interactions between locally forced circulations and the prevailing synoptic-scale northerly Etesian flows. The model system employed were similar to the system developed by NCAR/RAL for Army test-range support building upon the MM5 model. The grid increment of the inner-most grid was 1.1 km, which is capable of representing the bulk thermal and dynamic effects of the Athens urban area.

This presentation will address a series of sensitivity experiments that explore the added value of the various underlying boundary conditions to the quality of the model forecast of the surface temperatures and winds. In particular, we will focus on the sensitivity of the model forecast to the urban-related parameterizations and to the parameters used in the urban land-surface model. The results of several case studies during the period of the summer games in which the local circulation in the inner-most domain was dominated by different types of synoptic patterns will be discussed.