[pct-l] adiabatic/katabatic air

[kevin at antelecom.net (Kevin Corcoran)]

>In a message dated 1/5/04 10:13:21 AM, Steven.Setzer@Colorado.EDU writes:
>
><< This summer I spent a few days in the Colorodo mountains climing 14ers.  I
>camped in the same area every night and did day hikes from camp.  Every
>night my buddy slept down by a creek and I camped about 100 yard away and
>maybe 50 feet higher.  In the morning, I'd wake up warm and dry.  As I
>walked downhill to wake my friend up, I'd feel the air get suddenly
>colder.  >>>

	then CMountainDave wrote:

>Oh how true this is! We were camped in the Olympics and the exact same thing
>occurred: all the cold air sank and stayed along the creek bed. It was cold
>and damp. You could see your breath and people were dressed warmly 
>with hats on.
>I climbed up a hill about 200 vertical feet to a clearing and it was sunny,
>warm and dry. I stripped down to shorts and took a sun bath for a couple of
>hours. When I went back to the main camp, everyone was still bundled up. They
>thought I was nuts when I told them how much warmer it was just a few hundred
>yards away uphill

	Getting a much later start than my companions, I caught up to 
them at Monache Mdws at near darkness.  I knew better than to join 
them bedded down in the meadow, but I joined them because it was dark 
and I was tired.  Laying on top of my groundcloth on the gentle slope 
between the meadow's center and the surrounding higher ground, I 
could feel the slow settling of the cooler air.  With my head upslope 
of my feet, all night long I had a tough time sleeping with this cold 
draft wanting to displace the warm air out of my bag.  I awoke in a 
frost-covered sleeping bag.
	(Gunnison CO is frequently listed as the nation's cold spot 
for this exact reason.  I'd imagine Gunnison gets pretty wide 
temperature swings between dawn and midday.)
	I like overnighting on the Mt Baden-Powell summit at least 
once each summer, and conversely I've found that at sunset it cools 
down rapidly, becoming quite cool.  Yet, I always awake around 1 to 
2am sweating, it's so warm out.  I imagine that at sunset the higher 
cooler air traps the lower hot desert air in an inversion, but as the 
night progresses the warm ground air, compressed from above, gets 
displaced and updrafts against the mountain slopes. Does anyone know 
if my assumption on this is correct?

Kevin Corcoran