The weight exerted by air on the earth’s surface is called atmospheric pressure. The variations in the density of air bring about variations in weight of air and thereby variations in atmospheric pressure. Temperature, altitude and humidity are inversely proportional to atmospheric pressure.
Temperature and atmospheric pressure : Air expands when gets heated up. The expanded air is less dense and hence it ascends. This leads to lowering of atmospheric pressure. The ascending air spreads to the sides and cools. It becomes dense and decends. This results in sinking of cold air. As a result, atmospheric pressure increases. Thus as temperature increases, pressure decreases and as temperature decreases, pressure increases. Thus temperature and atmospheric pressure are inversely proportional.
Altitude and atmospheric pressure: The atmospheric pressure decreases with altitude. The pressure decreases at the rate of 1 millibar per an altitude of 10 metres. The ratification of air with altitude is the reason for the decrease in atmospheric pressure.
Humidity and atmospheric pressure: The quantity of water present in atmospheric air is called humidity. Water vapour is lighter than air and hence it ascends. If the quantity of water vapour is more in a unit volume of air, then naturally the atmospheric pressure will be less. Thus humidity and atmospheric pressure are also inversely proportional.
