All About Air Pressure


We don’t realize it, because we are used to it, but we actually live in the bottom of a large ocean of air. The air may not seem very heavy, but there is actually a huge weight of air above us, and it is pressing down on us all the time. So when the atmosphere pushes down on the Earth, it creates air pressure.

There are two types of pressure, high pressure and low pressure.


When air molecules exerts a lot of pressure on the Earth’s surface, this brings high pressure. As the air is moving down, this reduces the formation of clouds, and this leads to light winds and settled weather conditions.

For example, water pressure increases as you go deeper in the water, because there is more water pressing down on us.


Low pressure forms when warmer, lighter air rises and cools, and the water in it forms clouds and possibly precipitation. Low pressure systems are usually linked to wind and rain.

Rain, hail, sleet, and snow are examples of precipitation. They all have a few things in common. They all comes from clouds, not to mention, they are all forms of water that fall from the sky.


Air molecules are the molecules that make up air, which include the particles of nitrogen and oxygen.

The air that we breath in, and live in, is primarily made up of nitrogen (78.09%) and oxygen (20.95%). The other 1%, is made up of carbon dioxide, argon, and other trace gases. There is always water vapor present in the air, but this varies by up to 2%.

Earth is surrounded by a thin layer of air called the atmosphere. In this layer, it has a pushing force, called air pressure.

Air moving around the planet makes wind.

Air pressure effects the weather patterns across the globe, from the way the air pushes down on our planet.

Air pressure is at its greatest at ground level, because this is where there are most air molecules. If you climb to the top of a big mountain, you will find it more difficult to breath, because there are fewer air molecules, and the air pressure is much less. Mountain climbers often use a breathing apparatus to give them more oxygen.

The higher we go, the less air there is in the atmosphere.

Scientists measure air pressure with a machine called a barometer. With this, they can forecast short term changes in the weather.

Evangelista Torricelli invented the first barometer in 1644.

Weather forecasters measure pressure in millibars (mb).

The average air pressure on Earth’s surface is about 1013 millibars.

On a weather map “H” means high pressure, while “L” means low pressure.

On a weather map, lines called isobars show pressure.

Zones with high pressure are called anticyclones, while zones with low pressure are called cyclones or depressions.

If you have an area of low pressure and it is surrounded by an area of very high pressure, storms could easily form. Firstly, the low pressure makes the air rise, creating strong winds, and if there is a lot of water in the atmosphere, dark clouds could form, resulting in heavy rainfall to accompany the strong winds.

Submarines have to be specially adapted/designed to cope with the high pressure they encounter when they are deep underwater.