Air close to the surface ar flows down and also away in a high pressure system (left) and air operation up and also together in ~ a short pressure device (right).Credit: NESTA


Standing ~ above the ground and looking up, you are looking with the atmosphere. It might not look favor anything is there, especially if there are no clouds in the sky. But what girlfriend don’t watch is air – many it. We live in ~ the bottom of the atmosphere, and the load of all 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 every square customs (psi) of push at earth surface. High in the atmosphere, air press decreases. V fewer air molecule above, over there is much less pressure indigenous the load of the wait above.

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Pressure varies from day come day at the Earth’s surface ar - the bottom the the atmosphere. This is, in part, because the planet is no equally heated by the Sun. Areas where the air is warmed frequently have lower pressure due to the fact that the warm air rises. These locations are called low press systems. Areas where the air push is high, are dubbed high push systems.

A low press system has lower push at its center than the areas around it. Winds blow in the direction of the short pressure, and also the waiting rises in the environment where castle meet. As the waiting rises, the water vapor within it condenses, developing clouds and also often precipitation. Since of earth spin and also the Coriolis Effect, winds of a low pressure mechanism swirl counterclockwise phibìc of the equator and clockwise southern of the equator. This is referred to as cyclonic flow. ~ above weather maps, a low pressure mechanism is labeled with red L.

A high push system has higher pressure at its facility than the areas around it. Winds punch away from high pressure. Swirling in opposing direction indigenous a low push system, the winds that a high pressure system rotate clockwise phibìc of the equator and counterclockwise southern of the equator. This is referred to as anticyclonic flow. Air from greater in the environment sinks down to to fill the space left together air is blown outward. Top top a weather map, girlfriend may an alert a blue H, denoting the ar of a high push system.

How carry out we know what the press is? just how do us know just how it changes over time? Today, electronic sensors in weather stations measure air pressure. This sensors are able to make constant measurements of press over time. In the past, barometers to be used and measured exactly how much air propelled on a fluid, such as mercury. Historically, measurements of air push were described as “inches that mercury.” Today, meteorologists use millibars (mb) to describe air pressure.

Air push depends ~ above temperature and density.

When girlfriend inflate a balloon, the wait molecules within the balloon get packed an ext closely with each other than waiting molecules outside the balloon. This means the density of air is high inside the balloon. As soon as the thickness of waiting is high, the air press is high. The press of the wait pushes on the balloon native the inside, bring about it to inflate. If you warmth the balloon, the air press gets even higher.

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

Atmospheric scientists use math equations to explain how pressure, temperature, density, and volume are concerned each other. They call 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 also cold fronts and storms, such together thunderstorms. Because that example, if air press increases, the temperature must increase. If air pressure decreases, the temperature decreases. It likewise explains why wait gets colder at greater altitudes, where pressure is lower.