It is known by everyone that at sea level there is a warmer temperature than at the top of a mountain. However, many people would not know how to explain why this phenomenon takes place. In this post, I will explain the two main reasons why it is colder in the mountain.
You possibly know the relation between temperature and pressure: when the air (or any other gas) is pressurised, the latter warms, while if the pressure is reduced, it becomes colder. The atmospheric pressure indicates the quantity of air there is above us. For example, if the pressure is 1000 millibars, this means that there are approximately 10 tonnes of air above every square metre of land.
The pressure that I have mentioned (1000 millibars) is approximately the one there is at sea level. As we go up, the pressure diminishes because of two principal factors. One of them is the smaller gravitational pull that exerts the Earth on the air molecules. The other factor is that the warm air that rises from the altitudes tends to expand, for which it becomes less dense, and therefore colder.
So, we see that air pressure plays a very important role in the temperature of a place.
Retention of heat
Another factor that makes a mountain to be colder is the retention of heat, which is in part related to the point we have previously seen.
At sea level, where there is the most air, the sunlight that reaches the ground is trapped under about 100 kilometres of air and clouds that intercept the heat and radiate part of it back to the surface. However, at a higher altitude, this effect is considerably reduced. Above a certain height, the atmosphere loses heat more quickly than it can be heated, for which it becomes even colder.