Atmospheric Pressure

Definition

Atmospheric pressure is the force exerted by the weight of the Earth's atmosphere on the surface below. It is a crucial factor in understanding the behavior and characteristics of planetary atmospheres, including those of Earth and Venus.

5 Must Know Facts For Your Next Test

1. Atmospheric pressure decreases with increasing altitude, as there is less air mass above the surface exerting force.
2. High atmospheric pressure is associated with fair weather, while low pressure often leads to the formation of storms and other inclement weather.
3. The average atmospheric pressure at sea level on Earth is approximately 1,013 millibars (mb) or 101.3 kilopascals (kPa).
4. Venus has an extremely dense atmosphere with a surface pressure over 90 times greater than Earth's, due to the planet's high concentrations of carbon dioxide and other greenhouse gases.
5. Atmospheric pressure plays a crucial role in the formation and behavior of clouds, as it affects the temperature at which water vapor condenses into liquid water droplets.

Review Questions

• Explain how atmospheric pressure varies with altitude on Earth and the impact this has on weather patterns.
  • Atmospheric pressure decreases with increasing altitude, as there is less air mass exerting force on the surface below. This decrease in pressure leads to changes in temperature, humidity, and the ability of the atmosphere to hold water vapor. As a result, high-pressure systems are often associated with fair, stable weather, while low-pressure systems can lead to the formation of clouds, wind, and precipitation. The variation in atmospheric pressure with altitude is a key driver of weather phenomena, such as the formation of fronts, updrafts, and downbursts.
• Compare and contrast the atmospheric pressure on Earth and Venus, and explain how this difference contributes to the greenhouse effect on Venus.
  • The atmospheric pressure on Venus is over 90 times greater than on Earth, due to the planet's dense atmosphere composed primarily of carbon dioxide. This high pressure, combined with the greenhouse effect caused by the CO2 and other gases, results in an extremely hot surface temperature on Venus, reaching up to 450°C (around 850°F). In contrast, Earth's atmosphere has a much lower pressure and a more balanced composition, allowing for the development of a habitable climate. The greenhouse effect on Venus is greatly amplified by the planet's dense atmosphere, trapping heat and preventing it from escaping into space, leading to the planet's inhospitable surface conditions.
• Discuss the role of atmospheric pressure in the formation and behavior of clouds, and explain how this relates to the water cycle and weather patterns on Earth.
  • Atmospheric pressure plays a crucial role in the formation and behavior of clouds. As air rises, it expands and cools, causing water vapor to condense into liquid water droplets or ice crystals, which form clouds. The temperature at which this condensation occurs is directly related to the atmospheric pressure. Higher pressure environments, such as near the Earth's surface, require a lower temperature for condensation to occur, while lower pressure environments, such as at higher altitudes, have a higher condensation temperature. This relationship between pressure and cloud formation is a key driver of the water cycle and weather patterns on Earth. Variations in atmospheric pressure, caused by factors like temperature differences and air mass movements, lead to the formation of different cloud types and precipitation patterns, which in turn influence local and regional weather conditions.

Related terms

Barometer: An instrument used to measure atmospheric pressure, typically in units of millibars (mb) or hectopascals (hPa).

Troposphere: The lowest layer of the Earth's atmosphere, where weather phenomena such as clouds, wind, and precipitation occur.

Greenhouse Effect: The process by which certain gases in a planet's atmosphere trap heat from the sun, leading to an increase in the planet's surface temperature.