My GF and I went for a hike the other evening up the Grouse Grind, which is a trail (or more precisely, a staircase comprising a total of 2,830 stairs) that extends 2.9 kilometres almost straight up the face of Grouse Mountain in Vancouver, BC.
The day was nice enough – about 12 degrees C – and we hiked comfortably in shorts and T-shirts, but by the time we got to the top, the temperature had dropped significantly (causing a fairly severe Reynaud’s Syndrome reaction – but that’s another story). Obviously, this got me to thinking just how much we should have expected the temperature to drop.
It turns out that this is quite a complex atmospheric property, but you can, on average, reasonably expect temperatures to drop 6.5 degrees C for every 1000 metres in elevation gain, an effect called atmospheric lapse rate. The decline bottoms out at -56.5 degrees C above 11 km (however since this is about 2 km higher than the peak of Mount Everest, I’ll just disregard it for now).
Back to hike. The Grind, as well call it, has an elevation gain of 853 metres, which would mean I could have anticipated a temperature drop of about 5.5 degrees C. However, this doesn’t tell the whole story. The base of the mountain, where the hike begins, is another 274 metres above sea level, and since Vancouver sits for the most part level with the sea, the base of the hike also needs to be taken into account. 274 metres accounts for another 1.8 degrees, for a total drop of 7.3 degrees. And that puts the mountaintop estimated temperature at about 4.7 degrees (12 -7.3).
Not exactly Mount Everest conditions, but certainly colder than we were prepared for!
For future hikes, the key ratio is 6.5 degrees C for every 1000 m.