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Barometric Pressure, Measuring Atmospheric Pressure & Barometers

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  • 0:02 Barometric Pressure
  • 2:34 Measuring Barometric Pressure
  • 5:12 Lesson Summary
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Lesson Transcript
Instructor: Amy Lange

Amy has taught university-level earth science courses and has a PhD in Geology.

This lesson examines the causes of varying barometric pressure and how we measure them. After this lesson, you should better understand where barometric pressure values come from and why we care.

Barometric Pressure

Barometric Pressure, more commonly called atmospheric pressure, is the pressure exerted by the surrounding air in the atmosphere. It gets the name barometric pressure because it is measured with a barometer. Barometric pressure is commonly measured at all weather stations. Why is this such an important feature of understanding our climate and weather? As it turns out, minor variations in atmospheric pressure are tied to changing weather conditions. In this lesson, we're going to examine the science behind barometric pressure.

First, we need to understand what barometric pressure is and why it changes. In another lesson in this series, we learn that altitude and barometric pressure are closely interrelated. Atmospheric pressure decreases exponentially with higher altitude due to decreasing gravity with elevation and less overlying air pressing down.

To incorporate all of the changes that occur with changes in altitude, the barometric pressure equation models the changes in air pressure with altitude. The barometric pressure equation is as follows:

barometric pressure equation

Where P sub h is the pressure at elevation, P sub 0 is the pressure at sea level, m is the mass of one air molecule, g is gravity, h is the height at elevation, k is the Boltzmann constant, and T is temperature. What this equation shows you is that pressure decreases exponentially with altitude.

As we see in this equation, barometric pressure is dependent on altitude, pressure at sea level, gravity, and temperature. However, I mentioned at the beginning of this lesson that barometric pressure can also tell us about changes in weather. You've likely seen local weather reports talking about high pressure and low pressure systems. Low pressure systems are associated with storms because air rises at areas of low pressure and condenses to form clouds. So, these low and high pressure systems form and move around the globe with changing weather and climatic patterns. By measuring slight changes in barometric pressure at a weather station, we can then predict if a stormy low pressure system is approaching due to dropping atmospheric pressure. If the pressure begins to rise again and stays stable, we know that we're in a high pressure system, which is associated with clearer weather and stagnant air.

Measuring Barometric Pressure

So now that we know a little bit about barometric pressure, let's cover how it is measured. Barometers are instruments that measure atmospheric pressure. There are three common types of barometers: mercury, aneroid, and digital.

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