# Difference Between Barometric Pressure and Atmospheric Pressure

## Main Difference – Barometric Pressure vs. Atmospheric Pressure

When talking about pressure, atmospheric pressure and barometric pressure are two terms which are used often. They essentially refer to the same thing, but depending on the usage they may have two distinct connotations. The main difference between barometric pressure and atmospheric pressure is that atmospheric pressure describes the pressure exerted by the atmosphere, whereas barometric pressure refers to a pressure measured by a barometer

## What is Atmospheric Pressure

Above us, there is a large amount of air in the atmosphere. The weight of this air is constantly pushing down on us, exerting a pressure. The pressure exerted by the atmosphere is called the atmospheric pressure. The SI unit for measuring pressure is the pascal (Pa).  A pressure of one pascal is quite small. Typically, the pressures we experience on a daily basis are in the orders of kilopascals (a thousand pascals). For example, a human punch exerts a pressure between 150-550 kilopascals (kPa) [1]. “Atmospheric pressure” is a unit that has been defined to measure pressures in comparison to typical pressures exerted by the atmosphere. 1 atmosphere (1 atm) is about 100 000 Pa. Of course, at higher altitudes, atmospheric pressures are lower (there is less air pushing down on you). The pressure of 1 atmosphere refers to pressure exerted by the atmosphere at sea level.

A weather map showing atmospheric pressures (most likely in millibar)

## What is Barometric Pressure

Barometric pressure refers to the pressure measured by a barometer. A barometer is a device used to measure atmospheric pressure. There are many different types of barometers, such as mercury barometers (which have a column of mercury that rises when the atmospheric pressure increases) and aneroid barometers (which have a piece of metal which changes its dimensions when pressure changes). The mechanism for measuring pressure may be different for the different types of barometers, however they all measure atmospheric pressure.

There is a myriad of units which are used to measure pressure. A barometer may express pressure in terms of any of these units. For instance, a mercury barometer may represent the pressure in units of millimeters of mercury (mmHg). Bar is another unit that is used frequently. 1 bar of pressure is roughly equivalent to 1 atm.

An aneroid barometer used to measure atmospheric pressure. Here, pressure is given in units of inches of mercury and millibars

## Difference Between Barometric Pressure and Atmospheric Pressure

Atmospheric Pressure refers to the pressure exerted by the atmosphere.

Barometric Pressure is a term used to describe the pressure measured by a barometer.

References

1. World Public Library. (n.d.). ORDERS OF MAGNITUDE (PRESSURE). Retrieved August 19, 2015, from World Public Library – eBooks | Read eBooks online | Free eBooks: http://www.worldlibrary.org/articles/orders_of_magnitude_(pressure)

Image Courtesy

“ Surface map of the Midwestern United States on November 11, 1998. The area of Low pressure caused Minnesota’s former record for lowest measured atmospheric pressure on November 11, 1998. This record was broken on October 26, 2010” by WxGopher at en.wikipedia (Own work) [CC BY-SA 3.0], via Wikimedia Commons

“modern aneroid barometer”, author unknown (Own work) [Public Domain], via Wikimedia Commons