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.

Modelling and visualisation performed using OMatrix and Tecplot

A comparison of wind flow resulting from different initial ambient conditions is available here.