# Atmospheric Pressure

## What is Atmospheric Pressure?

Atmospheric pressure (also known as barometric, or simply, air pressure) is the pressure within the atmosphere of a planet. The atmosphere is made of tiny particles (atoms and molecules) that have mass and are subject to the effects of gravity and therefore have measurable weight. In most cases, atmospheric pressure can be very closely approximated by hydrostatic pressure which is due to the weight of the air above the measurement point.

## Why is Atmospheric Pressure important?

Illustration of the relationship between Air temperature and Air pressure

Atmospheric pressure is important in many natural sciences from Meteorology to Chemistry. It shares noteable, observable relationships with temperature and altitude in addition to its effects on the proximity of atmospheric particles to one another (thus impacting the interactions between particles). For example, atmospheric pressure can alter the physical state of water by forcing gaseous (water vapor) water molecules together (increasing pressure), results in condensation to liquid water. This can be observed at a larger scale in the formation of clouds.

Atmospheric pressure shares relationships with other important environmental factors such as altitude, humidity and temperature. It is necessary to note these relationships as these factors cannot be worked with or used in isolation unless a specific value is assumed beforehand (i.e standard room temperature or sea level altitude/atmospheric pressure).

## How is Atmospheric Pressure measured?

Pressure is usually measured using a barometer. Pressure measures force per unit of area. The SI unit for pressure is Pascals (1 Pa = 1 N/m2). Other units include pound-force per square inch (psi), millimeters or inches of mercury (mmHg or inHg) or expressed terms of standard atmospheric pressure (atm) where 1 atm = 1013.25 mbar = 101.325 kPa = 29.921 inHg = 760.00 mmHg.

Atmospheric pressure is measured by the advanced weather sensor on the SW01 ☒CHIP.