Abstract
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.
Highlights
One of the major meteorological characteristics that occur over the Aegean Sea during summer months is the onset of strong winds from northern directions, named Etesians
The model results showed a good agreement with the observations, they did not capture the localized maximum wind speeds at the maritime area downstream of the main gap. Since such strong wind events are quite frequent over the maritime area at the gap exit of Crete Island, which is an important waterway for commercial and recreational use and a cause of rapid spread of forest fires at adjacent mountainous areas inside the gap, it is important to improve the understanding of the three dimensional structure and the mechanisms associated with this gap flow
During the summer months when a northerly wind regime is established over the Aegean, strong northerly winds are observed at the abovementioned gap exit
Summary
One of the major meteorological characteristics that occur over the Aegean Sea during summer months is the onset of strong winds from northern directions, named Etesians. This paper is the second in a series examining the interaction of the northern wind flow over the Aegean Sea with the complex topography of Crete Island, and particular the significance of the major gap flow. The model results showed a good agreement with the observations, they did not capture the localized maximum wind speeds at the maritime area downstream of the main gap Since such strong wind events are quite frequent over the maritime area at the gap exit of Crete Island, which is an important waterway for commercial and recreational use and a cause of rapid spread of forest fires at adjacent mountainous areas inside the gap, it is important to improve the understanding of the three dimensional structure and the mechanisms associated with this gap flow. The final section is devoted to the concluding remarks of this work
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