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Gully Winds (Downslope Winds)
Comparison of observations with mesomodel.
Airflow (first panel*) over Mount Lofty Ranges in Gully wind situation overnight 3/4 February 1988 as determined by isentropic analysis based on observations from aircraft, balloon and ground.
Central Figure shows Mesomodel flow with an ICAO atmosphere of 15m/s easterly flow. Black areas along leeslope and in a vertical oval shape at about 3km above the leeslope shows regions with low Richardson Number (Ri<0.25) indicative of turbulence.
Third Figure is a 3D view of model flow for the same conditions. Clearly seen is the area prone to the strongest winds.
Noteworthy are: ¨ strongest winds (in red) occur on leeside slopes ¨ these strongest winds are associated with a jump-like feature, ¨ a reverse flow eddy forms over the lee plains, and ¨ severe turbulence occurs above the jump (marked in black) at about 3,000m altitude.
All of these features have been observed around the lee slopes of the Mount Lofty Ranges.
(* Observations from Warwick Grace 1995 Downslope Winds Met Study 41, Bureau of Meteorology)
More information regarding the details of the mesomodel is posted here. |
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A comparison of wind flow resulting from different initial ambient conditions is available here. |