All outdoor enthusiasts will know that when you head up into the mountains, things can get pretty frosty – but why is it that things get colder the higher up you go?
Brace yourselves, we’re about to drop some science on you… (but don’t worry, it’s not too bad). The temperature drop that we see with increased altitude all comes down to atmospheric pressure. We know that gravity pulls objects towards earth (this is why things fall to the floor when we drop them), but it also pulls the very air we breathe towards the earth.
This downwards force of air is what we call atmospheric pressure. When we’re stood at the bottom of a mountain, there’s more air above us getting pulled towards earth than there is when we’re at the top of the mountain. This means that the atmospheric pressure at the bottom of the mountain is greater at the top. Flip this around, and we can say that the atmospheric pressure is lower at the top of the mountain than the bottom. So, a key thing to remember is that the higher up you go, the lower the atmospheric pressure.
But what does this have to do with temperature? Well, because there’s less pressure on air higher up the mountain, the molecules in the air can spread out and they lose their heat more easily. If we know that atmospheric pressure reduces with height and that the lower the atmospheric pressure the more heat is lost, then it makes sense that temperatures drop as elevation increases – simple
As a general rule of thumb, if it isn’t snowing or raining, the temperature decreases roughly 5.4°F with every 1,000 feet rise in altitude. In practice, this isn’t always the case, and it’s important to remember that it’s not just altitude that affects air temperature. There are actually many factors affecting climate – for instance, two mountains of the same height will have different temperatures if only one of them is in the sunshine.
In fact, snow and rain affect the temperature drop so much they have their own formula – subtract 3.3°F (instead of 5.4°F) for every 1,000 feet rise in altitude.
So, there you have it. We’ve gone through how and why temperatures drop with altitude and give you a way to roughly calculate how much the temperature will drop for a given rise in altitude. Obviously, no formula can perfectly predict the natural world, so take your calculations with a pinch of salt. The general principles we’ve discussed, however, are tried and tested. So, if there’s one thing we do know for certain, it’s that it’ll be colder on top of the mountain than at the bottom – so make sure you take that extra layer with you!