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Diurnal mountain winds develop from terrain of
all scales |
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Circulations arise as a result of differential
heating between the ground in regions of complex terrain and free
atmosphere at the same elevation |
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During day, higher terrain is an elevated heat
source |
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During night, higher terrain is an elevated heat
sink |
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Slope winds- driven by horizontal temperature
contrasts between air over valley sidewalls and air over center of valley |
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Along-valley winds- driven by contrasts
along valley’s axis and nearby
plain |
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Cross-valley winds- driven by contrasts between
opposing sidewalls |
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Mountain-plain winds- driven by contrasts
between plateau and nearby plains |
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Katabatic wind: cold flow of air travelling
downward or down a slope |
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Anabatic wind: air current or wind rising up a
slope |
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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 |
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Speeds- 1-5 m/s with maximum a few meters above
the ground |
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Increase in speed as length of slope increases
(Antarctica 14-30 m/s) |
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Strongest downslope at sunset; strongest upslope
in midmorning |
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Depth of downslope ~5% of drop in elevation from
top |
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Upslope flows increase in depth as move upslope |
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Stronger the stability, shallower the slope
flows |
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Downslope flows converge into gullies; upslope
flows converge over higher ground between gullies |
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Enclosed terrain features develop slope flows
but weak along-valley circulations |
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Enhanced heating during the daytime and cooling
at night as a result of absence of along-valley advection of cool/warm air |
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Light winds |
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Record cold temperature in Utah: Peter Sinks
–57C |
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Clements (2001) conducted field program in
remote basin in northern Utah to study slope flows |
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Field program held 8-12 Sept. 1999 |
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Notes