[BULK] - RE: [pct-l] Campo to Morena Day Hike (was 16+mi.drystretches)

[jeffmoorehead1 at cox.net (Jeff Moorehead)]

wow that was some explanation of katabatic-- although the previous post 
(Judson) did correctly point out that Antartica is characterized by nearly 
constant katabatic winds. i learned this as i tried to come up with an 
explanation that would never have been as lucid as yours... good thing i 
didn't try. we can still blame Oilcan for the cold winds??

I'll try 'adiabatic' though and then you can correct me. Adiabatic (as 
opposed to isothermal) refers to a disequilibrium in heat transfer 
charcterized by the thermodynamic equation PV=nRT where P=Pressure and 
T=temperature. The practical effects that we all experience is the warming 
of the air as we descend to lower elevations (higher baromaetric 
pressure).Conversely, air cools as we gain elevation, which makes for a 
normal temperature-elevation profile. So when katabatic conditions exist, 
the normal profile is 'inverted'. The 'adiabatic lapse rate' depends on the 
moisture contained in the air. The dry lapse rate is steeper than the wet. 
If you descend into the desert from the dry side (east side in CA) of 
mountains, the temperature increases at a rate faster than it was decreasing 
as you climbed the west side. That's why the deserts to the east of the 
Sierra are not only dry (the rainshadow effect) but so damn hot!
how can we pin this one on Oilcan?




----- Original Message ----- 
From: "Brett" <blisterfree@isp01.net>
To: "Judson Brown" <judson@jeffnet.org>; <pct-l@mailman.backcountry.net>
Sent: Monday, February 07, 2005 5:33 PM
Subject: Re: [BULK] - RE: [pct-l] Campo to Morena Day Hike (was 
16+mi.drystretches)


> >I think katabatic refers to strong, cold winds which occur in polar 
> >regions,
>> especially over ice caps. Antarctic explorers had to deal with them
>> constantly.
>
> Katabatic has nothing to do with acrobatic mountain lions. It's simply the 
> colder and thus heavier air that sinks into low lying areas, most commonly 
> in the evening and overnight hours when heat radiates away from the earth 
> at a faster rate than it is absorbed. It is not a geographically-specific 
> phenomenon, although it tends to occur most noticeably in mountainous 
> areas where the lower-lying drainages are natural conduits for the cold 
> air from the heights. Katabatic air acts like a mini-river that, in fact, 
> often "flows" just above the actual rivers. Or creeks. Climb away from the 
> creeks before selecting a campsite, even as little as 10 or 20 feet above 
> them, and avoid much of the katabatic cooling effect. Sleep warmer.
>
> Now who wants to explain "adiabatic"?
>
> - blisterfree
>
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