Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 9 6 2009 10.5194/nhess-9-1845-2009 http://www.nat-hazards-earth-syst-sci.net/9/1845/2009/ http://www.nat-hazards-earth-syst-sci.net/9/1845/2009/nhess-9-1845-2009.html http://www.nat-hazards-earth-syst-sci.net/9/1845/2009/nhess-9-1845-2009.pdf 1845 1855 2009-11-11 The interaction of northern wind flow with the complex topography of Crete Island – Part 1: Observational study I. Koletsis koletsis@meteo.noa.gr K. Lagouvardos V. Kotroni A. Bartzokas University of Ioannina-Laboratory of Meteorology, Department of Physics, Ioannina, Greece National Observatory of Athens, Institute of Environmental Research, Athens, Greece The island of Crete with its mountain ranges is an excellent example of a major isolated topographic feature, which significantly modifies the regional airflow as well as the pressure and temperature fields. During summer, when northerly winds are blowing over the Aegean Sea (a large number of which are characterized as Etesians), the highly complex topography of Crete plays an important role in the modification of this northern wind flow. The main objective of this study is to determine the role of the topography of Crete Island during this wind flow on the strong downslope winds at the southern parts of the island as well as on the development of a gap flow between the two highest mountains of the island (Lefka Ori and Idi). For that purpose, observational data from four meteorological stations located along the aforementioned gap are used along with QuikSCAT satellite data. The observational analysis shows that the interaction of the northern wind flow with the mountains of Crete Island produces an upstream deceleration, a leftward deflection of the air as this approaches the mountains and an intensification of the winds at the southern coasts accompanied with a temperature increase. 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