temp/elev change rule of thumb?
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Nov 15, 2009 at 1:10 pm #1241701Charles MaguireMember
Is there a rule of thumb for temperature changes per change in elevation?
Ex. If base camp is at 3000 ft and 40*, what is temperature drop as your elevation inceases by 1000 feet?
ThanksNov 15, 2009 at 1:27 pm #1545454Lori PBPL Member
@lori999Locale: Central Valley
I've seen it described as anywhere from 3.5 – 5 degress F per 1,000 feet… but temps also depend on weather, and to a degree terrain. On a night hike to Half Dome, I experienced low 30F temps going through the river valley and a dramatic upswing in temp on the way UP to Half Dome, just by heading away from the damp, lower Little Yosemite Valley. Also, on a different trip in the same location, Yosemite Valley proper was having night temps of about 50F and Little Yosemite only a couple thousand feet higher was at 33F the second night we were there… much to the dismay of someone who brought the wrong sleeping bag.Nov 15, 2009 at 1:50 pm #1545457Gary DunckelBPL Member
I agree with Lori–3.57*F per 1000' elevation gain, with the wild card being local intervening conditions. An example of this might be if you were hiking up the east side of a mountain range when a chinook wind was developing on the west side and blowing warm, dry air over the pass. Of course, this would also eventually warm up your base camp, but the 3.5*F/1000' would probably still apply.Nov 15, 2009 at 3:59 pm #1545476Charles MaguireMember
ChuckNov 15, 2009 at 4:14 pm #1545479* *Member
The environmental lapse rate is 3.56 degrees/1000, the dry adiabatic lapse rate is 5.4 degrees/1000, and the saturated adiabatic lapse rate is 2.7 degrees/1000. Aviators use approximately 3 degrees per 1000. All units are in Fahrenheit and feet. The key here is which lapse rate is best for your purposes, and I don't have that answer.
Just a quick tip to convert Celsius to Fahrenheit for temps above freezing: Double and add 30. Example: 15*2+30=60. Fifteen Celsius is 59 Fahrenheit-only one degree off.Nov 19, 2009 at 11:45 am #1546474Ed CollyerMember
@ecollyerLocale: East Bay Area
In my opinion, the Rule of Thumb is exactly as stated above: 3.5*F/1000 ft for moist air and about 5.5*F/1000 ft for dry air. However there are factors that come into play such as whether your in a valley (cold but lower in elev.) or a ridge (windy). These factors will contribute to overall comfort.Nov 19, 2009 at 11:51 am #1546476John BrochuMember
@johnnybgood4Locale: New Hampshire
This morning on Mount Washington it was 27 degrees at 1600 feet, a53 degrees at 4,000 feet – then colder again at the summit. So you never can tell for sure!
(They have thermometers at various points along the auto road and you can check them in real time on the web.)
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