View Full Version : Temperature and Elevation concerns...
Touch of Grey
12-28-2006, 22:26
I seem to remember from somewhere in my past that there is a direct correlation between temperature and elevation. Something like three degrees drop/rise for ever 100 or 1000 feet change in elevation. Might be from my days of studying aviation where temperature and elevation are a big concern.
Does anyone else have information concerning this?
In watching some of the threads on WB I see some concerned with temperature and some mentioning elevation having a play in the temperature but do not recall anyone ever giving a figure.
I am trying to get an idea of possible temps based on maximum elevation and average temps for the trip north so I can make decisions on clothing and insulation in camp issues.
TOG:confused:
glad you're asking this question... curious about how much colder the trail is now than the temperatures forcast for franklin, NC.
Kerosene
12-28-2006, 22:37
It's 2-3 degrees Fahrenheit for every 1,000 feet of elevation change. Of course, that's only a generalization that can be skewed by a number of factors but for average temperatures it seems to be a pretty good indicator.
I still remember skiing in Vermont as a kid...it was 10 degrees below zero at the base and 10 above at the summit of Bolton Valley.
terrapin_too
12-28-2006, 22:37
This page (http://www.fao.org/sd/2002/EN0701a_en.htm) puts the figure at 0.6 ºC per 100 meters, but that sounds a bit high to me.
The change in temperature as a function of elevation is normally about 0.6 ºC per 100 m, but it may vary significantly as a function of moisture, temperature, etc. It is relatively low (0.5ºC per 100m) for wet air (i.e. air saturated with water, as in clouds) and 1º C for "dry" air (below 100%moisture).
stumpknocker
12-28-2006, 22:50
It's 2-3 degrees Fahrenheit for every 1,000 feet of elevation change. Of course, that's only a generalization that can be skewed by a number of factors but for average temperatures it seems to be a pretty good indicator.
I still remember skiing in Vermont as a kid...it was 10 degrees below zero at the base and 10 above at the summit of Bolton Valley.
Well said Kerosene. I try not to sleep in a valley or gap in the winter, but I don't sleep on a summit either...somewhere in between is usually more comfortable.
Rising air cools at the rate of 5.5 (F) degrees per thousand feet of elevation gain as long as the air is not saturated. If it's saturated, cooling is reduced to about 3 degrees (F) because of the moisture retaining some heat.
There's good information here already and I won't add to it other than to name the phenomenon discussed which is often referred to as the environmental lapse rate (ELR).
maxNcathy
12-29-2006, 08:51
Rising air cools at the rate of 5.5 (F) degrees per thousand feet of elevation gain as long as the air is not saturated. If it's saturated, cooling is reduced to about 3 degrees (F) because of the moisture retaining some heat.
I wondered why the temps dropped 16F degrees when we drove up in the mts 3000ft elevation gain near Santa Fe NM in November.
Thanks.
smokymtnsteve
01-08-2007, 02:08
when it gets really cold and still the top of a mtn can be warmer then the valley whar the cold air is trapped.
Pokey2006
01-08-2007, 04:22
I always thought that it was 10 degrees for every 1,000 feet of elevation, but maybe that was an over-exageration, just to be on the safe side. That was just always the rule of thumb I was taught to use.
n2o2diver
01-08-2007, 05:22
In aviation we use the adiabatic lapse rate of 2 degrees Celsius per 1000 ft of altitude or 3.5 Degrees Fahrenheit per 1000 ft. This works as a good rule of thumb. This is based on a standard day with no moisture and does not take into account any inversions.
Also remember cold air is more dense than warm air and will settle into low spots in valleys.
In meteorology it is much more complicated and you can get into moist or dry adiabatic lapse rates blah blah blah.....
Fiddleback
01-08-2007, 10:45
In aviation we use the adiabatic lapse rate of 2 degrees Celsius per 1000 ft of altitude or 3.5 Degrees Fahrenheit per 1000 ft. This works as a good rule of thumb. This is based on a standard day with no moisture and does not take into account any inversions.
Also remember cold air is more dense than warm air and will settle into low spots in valleys.
In meteorology it is much more complicated and you can get into moist or dry adiabatic lapse rates blah blah blah.....
'Tis true. The lapse rate is close to 3° per 1000' all other variables being the same. Trouble is, they never are...
FB
I do not think the lapse rate used by aviators works on a mountian, because the sun is heating the mountian. Therfore, I think the the lapse rate on a mountian would be less than the normal lapse rate used in aviation. The surface, (trees, rocks, etc) would have an affect on the temperature as well.
Touch of Grey
01-08-2007, 11:59
Well Thank You to all! I too realize that there are many more variables involved in the elevation versus temperature debt, inversions and such, and was looking to not only be sure of the general rule of thumb so I could more or less look at the NOAA Charts for GA and NC highs/lows and average temps and get an idea of what I should plan for.
Looking at those charts and seeing that average temps for northern GA are 60 degrees for the day and 30 - 40 at night, I now know that I need to think long sleeves most of the day and survivability temps of roughly 15 - 25 degrees at 3000 feet elevation. This seems to be the average elevation for much of GA.
It could obviously go one way or the other above or below this but again on average so long as I can be comfortable in my hammock or tent at these temps (15-25) I can be sure that I will not shiver thru every single night until temperatures overnight get higher. This of course would be just with mid-weight polypro sleeping gear and wool socks for the nights. Again obviously, I could put all of my clothes on and survive lower temps if I had to.
I know this helped me out and hopefully it has given others a pause for thought about the same types of issues for themselves. This helps me plan for maximum warm with minimum coverage and weight.
TOG:-?
maxNcathy
01-08-2007, 13:06
If the air is quite dry the temps drop 5.5F per 1000 feet of evation and if humid the temps drop 3F per 1000ft of increased elevation as rising moisture helps maintain heat....That's what I read recently........
terrapin_too
01-08-2007, 13:36
There's no such thing as "average" weather. Assume and plan for extremes. Not arctic, and not Saharan.... but major swings, often within 24 hours. Think long and hard about how you'll deal with rain. Mountains make their own weather.
Why would it be much of a concern anyway? If you are walking up or down the mountains you'd deal with whatever the slight change was as it gradually affected you, probably so gradual you would hardly notice it... The Appalachians are not that high anyway.
terrapin_too
01-08-2007, 14:26
The Appalachians are not that high anyway.
Not that high but they have some incredible weather -- and are large enough to make their own weather, particularly with regard to precipitation.
In the dead of summer when the valleys are sweltering in 90 degree heat, even a couple thousand feet of altitude makes a welcome change. :) Plus, if there's any wind at all, you'll feel it at altitude.
SalParadise
01-08-2007, 14:27
Why would it be much of a concern anyway? If you are walking up or down the mountains you'd deal with whatever the slight change was as it gradually affected you, probably so gradual you would hardly notice it... The Appalachians are not that high anyway.
no matter when you're walking, but I always kept it under consideration when choosing to hike another mile and camp at maybe 5,000 ft or to stay in the valley.