Air near the surface flows down and also away in a high pressure system (left) and also air operation up and together at a low pressure mechanism (right).Credit: NESTA


Standing top top the ground and also looking up, you are looking v the atmosphere. It can not look prefer anything is there, especially if there room no clouds in the sky. However what girlfriend don’t watch is air – numerous it. We live at the bottom that the atmosphere, and also the weight of all the air above us is called air pressure. Over every square customs on the surface ar of the earth is 14.7 pounds the air. That means air exerts 14.7 pounds per square inch (psi) of push at earth’s surface. High in the atmosphere, air push decreases. Through fewer air molecules above, there is much less pressure native the weight of the air above.

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Pressure varies from day to day at the Earth’s surface - the bottom that the atmosphere. This is, in part, due to the fact that the earth is not equally heated by the Sun. Locations where the air is warmed regularly have lower pressure due to the fact that the warmth air rises. These areas are dubbed low pressure systems. Locations where the air pressure is high, are called high press systems.

A low pressure system has actually lower press at its center than the areas approximately it. Winds blow in the direction of the low pressure, and also the waiting rises in the atmosphere where lock meet. As the waiting rises, the water vapor within it condenses, creating clouds and also often precipitation. Because of earth’s spin and also the Coriolis Effect, winds the a low pressure system swirl counterclockwise phibìc of the equator and also clockwise south of the equator. This is referred to as cyclonic flow. On weather maps, a short pressure device is labeled v red L.

A high pressure system has higher pressure in ~ its facility than the areas approximately it. Winds punch away indigenous high pressure. Swirling in opposing direction indigenous a low pressure system, the winds of a high pressure system rotate clockwise north of the equator and counterclockwise south of the equator. This is referred to as anticyclonic flow. Air from greater in the setting sinks down to to fill the an are left as air is blown outward. ~ above a weather map, friend may notification a blue H, denoting the ar of a high push system.

How carry out we know what the push is? how do we know just how it alters over time? Today, digital sensors in weather stations measure up air pressure. These sensors are able to make constant measurements of press over time. In the past, barometers to be used and measured just how much air thrust on a fluid, such as mercury. Historically, dimensions of air pressure were explained as “inches the mercury.” Today, meteorologists use millibars (mb) to define air pressure.

Air pressure depends on temperature and also density.

When you inflate a balloon, the air molecules within the balloon acquire packed an ext closely together than air molecules external the balloon. This method the density of waiting is high within the balloon. When the density of air is high, the air pressure is high. The press of the waiting pushes top top the balloon indigenous the inside, causing it to inflate. If you heat the balloon, the air pressure gets also higher.

Air pressure depends ~ above the temperature the the air and also the thickness of the air molecules.

Atmospheric scientists use mathematics equations to describe how pressure, temperature, density, and also volume are related to each other. They call these equations the Ideal Gas Law. In these equations, temperature is measure up in Kelvin.

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This equation helps us explain how weather works, such as what happens in the environment to produce warm and also cold fronts and storms, such as thunderstorms. Because that example, if air press increases, the temperature need to increase. If air press decreases, the temperature decreases. It also explains why air gets colder at greater altitudes, where press is lower.