Monday, 3 August 2015
Back Bay Ballroom (Sheraton Boston )
In previous literature works it was quantitatively shown that surface winds in Israel follow a fixed flow pattern due to a specific synoptic group, the Persian trough (PT), during the summer. However, for other synoptic groups flow patterns were not quantitatively verified. This work studies the surface wind steadiness under various synoptic groups, including the PT. The semi objective synoptic classification of Alpert et al (2004) which characterizes each synoptic class according to four meteorological fields at 1000 hPa at 12Z was used to define the synoptic classes during the studied period. The wind characterization was made by calculating surface wind averages, standard deviations (STD), steadiness and statistical significance using Israel meteorological service measurements from 12 stations. These statistical results indicated the hours at which steady surface wind occurs for each synoptic class. During the night, synoptic winds with an easterly component enhance the steadiness of local SE winds. During the day, synoptic winds with a westerly component enhance the steadiness of local NW to SW winds. The surface flow steadiness increases with strong synoptic forcing. Due to a significant synoptic forcing in the area, there are a substantial number of hours at which steady surface flow prevails. It was found that 14 synoptic states show steady flow during certain hours. Typical values for these events are: steadiness > 0.65, wind direction STD < 60°, wind speed STD 1-2 m/s and sector direction widths of 50°-150°, all of them within 70% statistical significance.
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