WHY MOUNTAINS ARE COLDER THAN PLAINS?
As it is well known that as we move towards hight, it becomes colder..... the high places should be hotter as they are a little close to sun !!!!
The distance to the sun has absolutely nothing to do with this. The fact is that the temperature sinks with altitude with an average of 0.65 C per 100 meter (3 F per 1,000 ft) The reason is: Air doesn't get warmed up by the sun's energy. At least, not at our under the stratosphere. What gets warmed up is the ground. That warms up a thin layer of air right above it and since warmer air is lighter, it rises.
But because the higher you get, the lesser the atmospheric pressure is, that rising air cools down by the so-called adiabatic effect. This is the same thermodynamic principle that cools down your fridge when a compressed coolant is released through a nozzle.
Therefore the higher you get, the colder it is. At the altitude an airliner flies, the outside temperature is around -50 C (-58 F).
But sometimes things are different. If there is no wind at all, during the night the cold air from the hills surrounding a valley will sink down because colder air being denser, is also heavier. In fact, it can create a wind called a katabatic wind. In the early morning, the air down in the valley will then be colder than up in the hills or mountains.
If you ever see fog down in a valley, you'll know that this is what happened. Because colder air probably mixed with moist air (lakes and rivers are usually down in valleys) is what is needed to form fog. And since the air above is warmer, it forms what is called an inversion: Cold air under warm one. And nothing moves ... until the sun, again, warms up the ground during the day.
But because the higher you get, the lesser the atmospheric pressure is, that rising air cools down by the so-called adiabatic effect. This is the same thermodynamic principle that cools down your fridge when a compressed coolant is released through a nozzle.
Therefore the higher you get, the colder it is. At the altitude an airliner flies, the outside temperature is around -50 C (-58 F).
But sometimes things are different. If there is no wind at all, during the night the cold air from the hills surrounding a valley will sink down because colder air being denser, is also heavier. In fact, it can create a wind called a katabatic wind. In the early morning, the air down in the valley will then be colder than up in the hills or mountains.
If you ever see fog down in a valley, you'll know that this is what happened. Because colder air probably mixed with moist air (lakes and rivers are usually down in valleys) is what is needed to form fog. And since the air above is warmer, it forms what is called an inversion: Cold air under warm one. And nothing moves ... until the sun, again, warms up the ground during the day.
