# Atmospheric Pressure Definition and Explanation

## What is Atmospheric Pressure?

Atmospheric pressure, also known as barometric pressure, is the force exerted by the weight of the Earth’s atmosphere on a given surface area. It’s essentially the pressure created by the layers of air molecules above any point on Earth’s surface. This pressure decreases with altitude as there are fewer air molecules above higher elevations.

## How Atmospheric Pressure is Measured

Atmospheric pressure is typically measured using a barometer and is expressed in several units:

– Pascals (Pa) – the SI unit
– Millibars (mb) – commonly used in meteorology
– Inches of mercury (inHg) – traditional measurement
– Atmospheres (atm) – standard reference pressure

At sea level, standard atmospheric pressure is defined as:
101,325 Pa (101.325 kPa)
1013.25 mb
29.92 inHg
1 atm

## Factors Affecting Atmospheric Pressure

Several factors influence atmospheric pressure:

### Altitude
Pressure decreases with increasing altitude because there’s less atmosphere above to exert force.

### Temperature
Warm air is less dense than cold air, leading to lower pressure in warm conditions.

### Humidity
Moist air is slightly less dense than dry air at the same temperature, resulting in slightly lower pressure.

### Weather Systems
High and low pressure systems create regional variations in atmospheric pressure.

## Importance of Atmospheric Pressure

Atmospheric pressure plays crucial roles in:

– Weather patterns and forecasting
– Aviation operations
– Human physiology (especially at high altitudes)
– Industrial processes
– Scientific research

## Variations in Atmospheric Pressure

Normal atmospheric pressure at sea level ranges between 980-1040 mb. Extreme values include:
– Highest recorded: 1083.8 mb (Agata, Siberia, 1968)
– Lowest recorded (non-tornadic): 870 mb (Typhoon Tip, 1979)

Understanding atmospheric pressure helps meteorologists predict weather changes and assists in various scientific and industrial applications. Its measurement and monitoring remain fundamental to numerous fields of study and practical applications in our daily lives.