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


Standing ~ above the ground and also looking up, you room looking v the atmosphere. It might not look choose anything is there, particularly if there space no clouds in the sky. But what you don’t watch is waiting – several it. Us live in ~ the bottom that the atmosphere, and also the load of every the air above us is referred to as air pressure. Over every square customs on the surface of the planet is 14.7 pounds the air. That means air exerts 14.7 pounds per square inch (psi) of pressure at earth’s surface. High in the atmosphere, air press decreases. V fewer air molecule above, there is less pressure indigenous the weight of the waiting above.

You are watching: A swirling center of low air pressure is called

Pressure different from day come day at the Earth’s surface - the bottom of the atmosphere. This is, in part, since the earth is not equally boil by the Sun. Locations where the wait is warmed frequently have reduced pressure because the warmth air rises. These areas are referred to as low press systems. Areas where the air press is high, are referred to as high push systems.

A low pressure system has actually lower push at its facility than the areas approximately it. Winds blow in the direction of the short pressure, and the waiting rises in the atmosphere where lock meet. As the waiting rises, the water vapor within it condenses, forming clouds and also often precipitation. Since of earth’s spin and the Coriolis Effect, winds the a short pressure system swirl counterclockwise north of the equator and also clockwise south of the equator. This is referred to as cyclonic flow. ~ above weather maps, a low pressure system is labeled through red L.

A high push system has greater pressure in ~ its facility than the areas roughly it. Winds punch away native high pressure. Swirling in the opposite direction native a low push system, the winds the a high pressure device rotate clockwise north of the equator and counterclockwise southern of the equator. This is referred to as anticyclonic flow. Air from greater in the environment sinks under to to fill the an are left as air is swollen outward. On a weather map, you may notice a blue H, denoting the location of a high pressure system.

How execute we recognize what the pressure is? exactly how do we know how it changes over time? Today, digital sensors in weather stations measure air pressure. This sensors space able come make consistent measurements of push over time. In the past, barometers to be used and measured exactly how much air driven on a fluid, such as mercury. Historically, measurements of air pressure were described as “inches that mercury.” Today, meteorologists usage millibars (mb) to explain air pressure.

Air pressure depends on temperature and also density.

When friend inflate a balloon, the wait molecules inside the balloon obtain packed much more closely with each other than air molecules exterior the balloon. This method the density of air is high within the balloon. Once the thickness of waiting is high, the air pressure is high. The pressure of the wait pushes ~ above the balloon from the inside, leading to it to inflate. If you warmth the balloon, the air press gets also higher.

Air press depends top top the temperature of the air and the thickness of the waiting molecules.

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

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This equation help us explain how weather works, such as what happens in the environment to create warm and cold fronts and storms, such as thunderstorms. For example, if air pressure increases, the temperature should increase. If air pressure decreases, the temperature decreases. It likewise explains why air gets cooler at higher altitudes, where press is lower.