Winds

Diurnal Mountain Winds

Diurnal mountain winds develop from terrain of all scales

Circulations arise as a result of differential heating between the ground in regions of complex terrain and free atmosphere at the same elevation

During day, higher terrain is an elevated heat source

During night, higher terrain is an elevated heat sink

Sacramento Valley

Grand Canyon

Kali Gandaki Valley

Mountain wind systems

Slope winds- driven by horizontal temperature contrasts between air over valley sidewalls and air over center of valley

Along-valley winds- driven by contrasts along valley’s axis and nearby plain

Cross-valley winds- driven by contrasts between opposing sidewalls

Mountain-plain winds- driven by contrasts between plateau and nearby plains

Mountain Wind Systems

Terminology

Katabatic wind: cold flow of air travelling downward or down a slope

Anabatic wind: air current or wind rising up a slope

Slope Winds

Slope flows

Closed circulation driven by horizontal temperature contrasts between the air over the slope and the air at the same level over the center of the valley

Speeds- 1-5 m/s with maximum a few meters above the ground

Increase in speed as length of slope increases (Antarctica 14-30 m/s)

Strongest downslope at sunset; strongest upslope in midmorning

Depth of downslope ~5% of drop in elevation from top

Upslope flows increase in depth as move upslope

Stronger the stability, shallower the slope flows

Downslope flows converge into gullies; upslope flows converge over higher ground between gullies

Slope flows

Basin Circulations

Enclosed terrain features develop slope flows but weak along-valley circulations

Enhanced heating during the daytime and cooling at night as a result of absence of along-valley advection of cool/warm air

Light winds

Night flows

Thermal belt

Slope Flows in Peter Sink Basin

Record cold temperature in Utah: Peter Sinks –57C

Clements (2001) conducted field program in remote basin in northern Utah to study slope flows

Field program held 8-12 Sept. 1999

Peter Sinks

North Peter Sink

Peter Sinks Terrain

Perimeter

Instrumentation Layout

Net Radiation and Sonic Anemometer

Slide 24

Surface Energy Budget- Peter Sinks

Surface Temperature Variation

Tethersonde Operations

Vertical
Structure
in basin

Temperature Mast on Slope

Temperature Variation on Slope

Vertical Structure on Slope

Potential Temperature Profiles Along Slope

Morning Transition

Katabatic flow

Simulation of Katabatic Wind

Antarctica Katabatic Winds

Slide 38


	Diurnal mountain winds develop from terrain of all scales
	Circulations arise as a result of differential heating between the ground in regions of complex terrain and free atmosphere at the same elevation
		During day, higher terrain is an elevated heat source
		During night, higher terrain is an elevated heat sink


	Slope winds- driven by horizontal temperature contrasts between air over valley sidewalls and air over center of valley
	Along-valley winds- driven by contrasts along valley’s axis and nearby plain
	Cross-valley winds- driven by contrasts between opposing sidewalls
	Mountain-plain winds- driven by contrasts between plateau and nearby plains


	Katabatic wind: cold flow of air travelling downward or down a slope
	Anabatic wind: air current or wind rising up a slope


	Closed circulation driven by horizontal temperature contrasts between the air over the slope and the air at the same level over the center of the valley
	Speeds- 1-5 m/s with maximum a few meters above the ground
	Increase in speed as length of slope increases (Antarctica 14-30 m/s)
	Strongest downslope at sunset; strongest upslope in midmorning
	Depth of downslope ~5% of drop in elevation from top
	Upslope flows increase in depth as move upslope
	Stronger the stability, shallower the slope flows
	Downslope flows converge into gullies; upslope flows converge over higher ground between gullies


	Enclosed terrain features develop slope flows but weak along-valley circulations
	Enhanced heating during the daytime and cooling at night as a result of absence of along-valley advection of cool/warm air
	Light winds


	Record cold temperature in Utah: Peter Sinks –57C
	Clements (2001) conducted field program in remote basin in northern Utah to study slope flows
	Field program held 8-12 Sept. 1999