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


Standing top top the ground and looking up, you room looking with the atmosphere. It can not look like anything is there, particularly if there are no clouds in the sky. Yet what girlfriend don’t see is waiting – lots of it. We live in ~ the bottom the the atmosphere, and the weight of every the air above us is referred to as air pressure. Over every square customs on the surface of the earth is 14.7 pounds that air. That means air exerts 14.7 pounds per square customs (psi) of push at earth surface. High in the atmosphere, air push decreases. Through fewer air molecules above, there is much less pressure from the weight of the wait above.

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Pressure varies from day come day in ~ the Earth’s surface ar - the bottom of the atmosphere. This is, in part, because the planet is no equally boil by the Sun. Areas where the waiting is warmed often have lower pressure since the warm air rises. These locations are referred to as low push systems. Areas where the air push is high, are dubbed high push systems.

A low pressure system has actually lower push at its facility than the areas about it. Winds blow in the direction of the low pressure, and also the wait rises in the environment where they meet. As the waiting rises, the water vapor in ~ it condenses, forming clouds and often precipitation. Since of earth’s spin and also the Coriolis Effect, winds the a short pressure device swirl counterclockwise phibìc of the equator and clockwise southern of the equator. This is referred to as cyclonic flow. Top top weather maps, a short pressure system is labeled with red L.

A high press system has higher pressure at its center than the areas around it. Winds blow away native high pressure. Swirling in opposing direction indigenous a low pressure system, the winds the a high pressure mechanism rotate clockwise north of the equator and also counterclockwise southern of the equator. This is referred to as anticyclonic flow. Air from greater in the setting sinks down to to fill the space left as air is swollen outward. Top top a weather map, you may notification a blue H, denoting the place of a high press system.

How do we recognize what the pressure is? exactly how do we know how it alters over time? Today, digital sensors in weather stations measure up air pressure. These sensors are able to make continuous measurements of press over time. In the past, barometers to be used and also measured how much air moved on a fluid, such as mercury. Historically, measurements of air press were defined as “inches the mercury.” Today, meteorologists usage millibars (mb) to describe air pressure.

Air pressure depends on temperature and also density.

When you inflate a balloon, the waiting molecules within the balloon gain packed more closely with each other than wait molecules external the balloon. This way the density of wait is high inside the balloon. As soon as the density of wait is high, the air press is high. The push of the wait pushes top top the balloon native the inside, leading to it come inflate. If you warmth the balloon, the air press gets even higher.

Air pressure depends on the temperature of the air and also the thickness of the wait molecules.

Atmospheric researchers use mathematics equations to describe how pressure, temperature, density, and volume are related to each other. They speak to these equations the Ideal Gas Law. In this equations, temperature is measured in Kelvin.

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This equation helps us explain how weather works, such together what wake up in the environment to produce warm and also cold fronts and storms, such together thunderstorms. For example, if air press increases, the temperature need to increase. If air pressure decreases, the temperature decreases. It likewise explains why waiting gets cooler at higher altitudes, where push is lower.