In the absence of inversions, going up mountains will bring you into lower temperatures as you get higher.
What is the rule of thumb for how the temperature decreases with altitude?
asked Mar 20, 2018 at 5:09
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An interesting corollary to this question is the rule-of-thumb that relates the climate to the altitude. Roughly-speaking, 1000m altitude is equivalent to shifting 1000km northwards. So the top of Mont Blanc, which is in France and is 4484m high, has an arctic climate you'd expect to find at sea level 4500km further north (well into the Arctic Ocean).– Oscar BravoMar 20, 2018 at 12:27
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3For what it's worth, this is known as the lapse rate. The International Standard Atmosphere uses -6.5 C/km as the standard lapse rate for the troposphere (surface up to 11 km.) But, of course, as you've noted in the answer, this will vary based on local conditions, especially humidity.– reirabMar 20, 2018 at 14:40
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1 Answer
The answer is that it depends on the moisture held in the air
- moist air changes at a rate of 3° Fahrenheit per 1000 ft of vertical / 0.6° Celsius per 100m.
- dry air changes at a rate of 5.4° Fahrenheit per 1000 ft of vertical / 1° Celsius per 100m.
As moist air rises, it cools with height at a rate of 3°F per 1,000 feet (not nearly as fast as the dry-air rate of 5.4°F per 1,000 feet). Eventually clouds develop, and precipitation wrings moisture from the air. At the summit, the air is now both warmer and drier than air of the same altitude that has not climbed the mountain. But as the air passes over the summit and flows down the other side of the mountain, it compresses and warms at 5.4°F per 1,000 feet (now following the dry-air rate), creating a much warmer, dryer wind.
Discover Nature in the Weather: Things to Know and Things to Do
In Freedom of the Hills , they use an estimate of 3.5° Farenheit /2 ° Celsius per thousand feet to estimate the freezing level.
The idea is that if you know your elevation, the elevation you are going to and the temperature where you are, then you can use those pieces of information to estimate the temperature at the elevation you are headed to.
For instance, if base camp is at 11,000 ft and the peak is at 13,000 ft, then it will be approximately 7° Farenheit / 4° Celsius colder at the peak. This could be useful for calculating whether the snow will be frozen on the way up.
answered Mar 20, 2018 at 5:09
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1Okay, that's better than the 1 degree C per 100 meters I was going to post. Not quite as quick for estimating though, but when mountaineering a good number for how cold it will be is nice to have.– MonsterMar 20, 2018 at 6:24
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1@Monster I edited the SI values to correspond to the commonly used ratios (per 100m).– imsodinMar 20, 2018 at 8:09
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@Monster as long as you are below clouds, 1°C/100m is correct. Once it gets foggy, it is back to .6°C or .7°C /100m. If the top of a mountain is covered with clouds, and i am not equipped to have information on temperatures up there, chances are that i am not equipped to hike up a mountain with 5m vision. (equipped as in equipped with knowledge, experience or actual equipment) Mar 20, 2018 at 14:31