Here’s a little math everyone who plays in the mountains should know. How do you answer the question “How cold will it be up there?” when you’re climbing a mountain?
It’s not a surprise that the temperature drops as you rise in altitude. In a “normal” air mass, below cloud base, the temperature drops very predictably. The rate it drops is called the Dry Adiabatic Lapse Rate (DALR). The DALR is 3°C for every 1,000 vertical feet you rise, or 9.8°C per 1,000 m.
We find the math of “3° per thousand” easier to do in our heads. You wouldn’t be far off to round it to 10° per 1,000 m either). Above cloud base you get the West Adiabatic Lapse Rate (which isn’t a fixed number, nor simple math).
Here’s some sample calculations for normal conditions. Understand the lapse rate changes if there is visible moisture in the air, such as fog/cloud, rain or snow:
- If it’s 20°C in the Burstall Pass parking lot, at Burstall Pass itself, 480 m/1,550’ above you, it will be 4.5° colder, or 15.5°.
- If it’s 24° in Calgary at the airport (at 1,084 m), Upper Kananaskis Lake (at 1,720 m) is 6° colder or 18°, because it’s about 2,000’ above Calgary.
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