Air close to the surface ar flows down and away in a high pressure device (left) and air flows up and together in ~ a low pressure mechanism (right).Credit: NESTA
Standing on the ground and looking up, you space looking with the atmosphere. It could not look favor anything is there, particularly if there space no clouds in the sky. But what friend don’t watch is waiting – many it. We live in ~ the bottom of the atmosphere, and the weight of all the air over us is dubbed air pressure. Over every square customs on the surface of the earth is 14.7 pounds that air. That way air exerts 14.7 pounds every square customs (psi) of press at earth’s surface. High in the atmosphere, air press decreases. V fewer air molecule above, there is less pressure native the load of the air above.
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Pressure different from day to day at the Earth’s surface - the bottom of the atmosphere. This is, in part, because the planet is no equally boil by the Sun. Areas where the air is warmed regularly have lower pressure because the warm air rises. These locations are called low pressure systems. Places where the air press is high, are referred to as high pressure systems.
A low pressure system has lower push at its center than the areas approximately it. Winds blow towards the short pressure, and also the waiting rises in the atmosphere where they meet. As the air rises, the water vapor in ~ it condenses, developing clouds and also often precipitation. Since of earth’s spin and the Coriolis Effect, winds of a low pressure system swirl counterclockwise phibìc of the equator and also clockwise south of the equator. This is called cyclonic flow. Top top weather maps, a low pressure mechanism is labeled through red L.
A high push system has greater pressure at its center than the areas approximately it. Winds blow away indigenous high pressure. Swirling in opposing direction from a low pressure system, the winds that a high pressure system rotate clockwise north of the equator and also counterclockwise south of the equator. This is referred to as anticyclonic flow. Waiting from higher in the environment sinks down to fill the space left as air is blown outward. ~ above a weather map, girlfriend may an alert a blue H, denoting the place of a high pressure system.
How carry out we know what the push is? just how do us know exactly how it transforms over time? Today, digital sensors in weather stations measure up air pressure. This sensors space able to make continuous measurements of push over time. In the past, barometers to be used and measured just how much air driven on a fluid, such together mercury. Historically, measurements of air press were explained as “inches of mercury.” Today, meteorologists usage millibars (mb) to describe air pressure.
Air pressure depends on temperature and density.
When girlfriend inflate a balloon, the waiting molecules inside the balloon gain packed an ext closely together than air molecules exterior the balloon. This way the thickness of wait is high inside the balloon. Once the density of waiting is high, the air press is high. The pressure of the air pushes top top the balloon indigenous the inside, resulting in it come inflate. If you warmth the balloon, the air press gets even higher.
Air push depends ~ above the temperature that the air and also the density of the air molecules.
Atmospheric scientists use mathematics equations to define how pressure, temperature, density, and also volume are related to each other. They speak to these equations the Ideal Gas Law. In this equations, temperature is measure up in Kelvin.
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This equation help us explain how weather works, such together what wake up in the atmosphere to create warm and cold fronts and also storms, such as thunderstorms. For example, if air push increases, the temperature need to increase. If air press decreases, the temperature decreases. It also explains why air gets colder at greater altitudes, where push is lower.