Atmospheric Pressure
Atmospheric pressure is the force per unit area exerted by the weight of the overlying column of air in the atmosphere on any surface below it. At sea level, the standard atmospheric pressure is 101,325 Pa (or 1013.25 hPa / 1 atm), and it decreases with altitude as the mass of air above decreases. Atmospheric pressure differences drive wind and weather systems: low-pressure zones are associated with storms and clouds, while high-pressure zones bring clear, calm conditions.
Key Formula
P = ρ × g × h
LaTeX: P = \rho g h
| Symbol | Meaning | Unit |
|---|---|---|
| P | Atmospheric Pressure | Pa |
| ρ | Density of air | kg/m³ |
| g | Gravitational acceleration | m/s² |
| h | Height of air column | m |
Worked Example
Problem
Estimate the pressure exerted by a 1000 m column of air with average density 1.2 kg/m³ (g = 9.8 m/s²).
Solution
Step 1: Identify values: ρ = 1.2 kg/m³, g = 9.8 m/s², h = 1000 m. Step 2: Apply P = ρ × g × h. Step 3: P = 1.2 × 9.8 × 1000 = 11,760 Pa ≈ 11.76 kPa. Note: The full atmosphere is ~8400 m equivalent, giving ~100 kPa total.
Answer
Pressure from 1000 m air column ≈ 11,760 Pa (11.76 kPa)
Atmospheric Pressure at Different Altitudes
| Altitude (m) | Pressure (hPa) | Pressure (atm) | Location Example |
|---|---|---|---|
| 0 | 1013.25 | 1.000 | Sea level |
| 1000 | 898.8 | 0.887 | Low hill station |
| 2000 | 794.9 | 0.785 | Shimla, India |
| 5500 | 505.0 | 0.499 | Rohtang Pass |
| 8849 | 314.0 | 0.310 | Mt. Everest Summit |
Interactive Tools
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Related Terms
Wind
Wind is the horizontal movement of air from regions of high atmospheric pressure to regions of low atmospheric pressure, caused by differential heating of the Earth's surface. The speed and direction of wind are determined by the pressure gradient force, the Coriolis effect (due to Earth's rotation), and friction with the surface. Wind is a major driver of weather patterns, ocean currents, and climate, and is harnessed as a renewable energy source through wind turbines.
Cyclone
A cyclone is a large-scale atmospheric system with low central pressure, around which winds spiral inward — counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere due to the Coriolis Effect. Tropical cyclones (known as hurricanes in the Atlantic and typhoons in the Pacific) are intense, warm-core systems that derive energy from warm ocean water, while extratropical cyclones are cold-core systems associated with mid-latitude weather fronts. Cyclones bring heavy rainfall, strong winds, and storm surges, and are among the most destructive natural weather phenomena.
Humidity
Humidity is the measure of water vapor present in the air, expressed either as absolute humidity (mass of water per unit volume of air) or relative humidity (percentage of water vapor relative to the maximum possible at that temperature). Warmer air can hold more water vapor, so the same amount of moisture feels "drier" on a hot day than a cool day, which is why relative humidity is the most commonly reported measure. High humidity reduces the body's ability to cool itself through sweating, making heat feel more intense and posing health risks during heatwaves.
From Greek "atmos" (ατμός, vapor or steam) + "sphaira" (σφαῖρα, sphere), and Latin "pressura" from "premere" (to press). The concept was developed by Torricelli in 1643 when he invented the mercury barometer.