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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 6
Nat. Hazards Earth Syst. Sci., 10, 1115–1127, 2010
https://doi.org/10.5194/nhess-10-1115-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: 11th Plinius Conference on Mediterranean Storms

Nat. Hazards Earth Syst. Sci., 10, 1115–1127, 2010
https://doi.org/10.5194/nhess-10-1115-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  07 Jun 2010

07 Jun 2010

The interaction of northern wind flow with the complex topography of Crete Island – Part 2: Numerical study

I. Koletsis1,2, K. Lagouvardos1, V. Kotroni1, and A. Bartzokas2 I. Koletsis et al.
  • 1National Observatory of Athens, Institute of Environmental Research, 15236 Palaia Penteli, Athens, Greece
  • 2University of Ioannina, Department of Physics, Laboratory of Meteorology, 45110 Ioannina, Greece

Abstract. During the summer months, when northerly winds are blowing over the Aegean Sea the island of Crete modifies significantly the regional airflow as well as the pressure and temperature fields due to its complex topography. One of the major topographical elements of Crete Island is the major gap which is located between the two highest mountains Lefka Ori and Idi. On 24–25 August 2007 strong northerly winds, with gusts up to 25 m s−1, occurred at the exit of the major gap. In order to investigate the dynamics as well as the role of this elevated and sloping gap on the airflow modification, the event was simulated down to 1 km horizontal resolution using the non-hydrostatic model MM5. The model simulations show that the localized intensification of the flow downstream of the major gap is related to the channeling of the flow through the gap. The strongest winds are observed at the gap exit region, implying that the main cause of the strong winds is the pressure different between the gap entrance and exit, when the relatively cooler maritime air approached the island and dammed up the high mountains. Finally, sensitivity experiments with modified topography further supported the important role of the topography of the elevated gap, which reveals that the strong winds have aspects of both gap and downslope contributions over the gap exit.

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