Investigation Of Air Flow Characteristics In Istanbul Using Omega Model

The city of Istanbul is situated in a relatively complex location with respect to topography, water bodies and landscape. This study aims to reveal what roles these features play in the shaping of the local circulation characteristics in Istanbul. To answer this question, we carried out sensitivity and real case numerical experiments using a fully non-hydrostatic, three-dimensional numerical model (OMEGA) with unstructured grid. In the sensitivity simulations, we considered a uniform background flow direction (prevailing wind direction) but with different wind speeds in separate simulations. Real case simulations were performed for two dates (08 July 2007 and 09 December 2006) which provide the proper atmospheric conditions for the formation of the sea-land breeze and heat island circulation.

Results show that channeling occurs because of the valley lookalike Bosphorus Strait, which is more or less aligned with the prevailing wind direction. The urbanization strengthens the sea-land breeze by increasing the sea land temperature difference. The bridge-like land between two water bodies, the Black Sea and the Sea of Marmara, develops two sea breezes blowing towards each other. They form a convergence line around the middle of this land. The real case simulations showed that fully developed sea breeze exists at 1200 LST in winter case while it is observed at 1000 LST in summer case. Re-current circulations are also observed in both simulations. However, it occurs at higher altitude in the atmosphere in summer case than the winter case. The convergence occurs at 1500 LST in winter case and 1300 LST in summer case. The land breeze occurs at 1900 LST in winter whereas it is at 2200 LST for summer simulation.