Normal air pressure at sea level is 1013.25 millibars (mb) or 14.7 pounds per square inch (psi).
Here's a more detailed breakdown:
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Standard Atmospheric Pressure: This value is often referred to as standard atmospheric pressure and is a baseline measurement used in various scientific and engineering applications.
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Units of Measurement:
- Millibars (mb): A metric unit commonly used in meteorology to measure atmospheric pressure.
- Pounds per Square Inch (psi): An imperial unit often used in engineering and everyday applications, like tire pressure gauges.
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Altitude Affects Pressure: It's important to note that air pressure decreases as altitude increases. The 1013.25 mb / 14.7 psi value is specific to sea level. Air pressure on a mountaintop, for example, will be significantly lower.
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Weather Variations: Actual air pressure at sea level fluctuates depending on weather conditions. High-pressure systems generally bring clear skies and stable weather, while low-pressure systems are often associated with clouds, precipitation, and stormy conditions. The pressure readings you see reported on the weather news are variations around the "normal" sea-level pressure.
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Why Sea Level? Sea level serves as the standard reference point because it's a relatively consistent and easily measurable surface across the globe. This allows for meaningful comparisons of atmospheric pressure readings from different locations.
