Summary
Atmospheric pressure is the force per unit area exerted by the weight of the air column above a surface.
Core concept
Understand the system
Atmospheric pressure is the force per unit area exerted by the weight of the air column above a surface.
Why / how it happens
Causes and context
Atmospheric pressure is the force per unit area exerted by the weight of the air column above a surface. The governing relationship is: Heating expands air and lowers density and pressure; cooling increases density, while altitude reduces the overlying air column.
Mechanism / process
Heating expands air and lowers density and pressure; cooling increases density, while altitude reduces the overlying air column.
Key facts
- Standard sea-level pressure is 1013.25 hPa.
- Pressure generally decreases with altitude.
- Isobars join places of equal pressure on weather maps.
Important terminology
- isobar
- barometer
- high pressure
- low pressure
- pressure gradient
Established figures
- Standard sea-level pressure is 1013.25 hPa.
Named examples / case studies
- A deep low-pressure system can organize converging air, cloud and rainfall.
Causes / components
- Key components: isobar, barometer, high pressure.
- Heating expands air and lowers density and pressure; cooling increases density, while altitude reduces the overlying air column.
Effects / significance
- Pressure generally decreases with altitude.
- Isobars join places of equal pressure on weather maps.
- Application: A deep low-pressure system can organize converging air, cloud and rainfall.
Geography connection
A deep low-pressure system can organize converging air, cloud and rainfall. This illustrates how atmospheric pressure varies by location, scale or environmental context.
Bangladesh connection
Seasonal pressure contrasts between the Asian landmass and the Bay of Bengal help organize Bangladesh's monsoon circulation.
BCS preliminary facts
- Standard sea-level pressure is 1013.25 hPa.
- Pressure generally decreases with altitude.
- Isobars join places of equal pressure on weather maps.
BCS written analysis
Build an analytical answer
- Atmospheric pressure is the force per unit area exerted by the weight of the air column above a surface.
- Heating expands air and lowers density and pressure; cooling increases density, while altitude reduces the overlying air column. Use a deep low-pressure system can organize converging air, cloud and rainfall. as a named application in a comparative answer.
Common misconceptions
- High pressure does not always mean hot weather.
- Pressure gradient force acts from high toward low pressure, subject to other forces.
BCS PRACTICE ENGINE
Test Your Knowledge
Select the best answer, then check your response.
Atmospheric Pressure: which statement correctly applies isobar to this topic?
Quick revision
- Atmospheric Pressure
- Standard sea-level pressure is 1013.25 hPa.
- Pressure generally decreases with altitude.
- isobar / barometer
- Definition → process → spatial example