Atmospheric Pressure

Atmospheric pressure is the force exerted by the weight of the air above a given point on the Earth's surface. It is caused by the gravitational pull of the Earth on the air molecules in the atmosphere. Atmospheric pressure decreases with increasing altitude because there is less air above pushing down on the surface.

Factors Affecting Atmospheric Pressure

• Altitude: As altitude increases, atmospheric pressure decreases. At higher altitudes, there are fewer air molecules above, resulting in lower pressure.
• Temperature: Higher temperatures lead to lower pressure, while lower temperatures lead to higher pressure. This is because warmer air is less dense and exerts less pressure.
• Weather Systems: High and low pressure systems are associated with different weather patterns. High pressure areas generally bring fair weather, while low pressure areas are associated with cloudiness and precipitation.

Measuring Atmospheric Pressure

Atmospheric pressure is commonly measured using a barometer. The two main types of barometers are mercury barometers and aneroid barometers. Mercury barometers use the height of a column of mercury to measure pressure, while aneroid barometers use the deformation of a metal chamber.

Units of Measurement

The standard unit of pressure in the SI system is the pascal (Pa), but atmospheric pressure is often measured in millibars (mb) or inches of mercury (inHg) in weather reports. Standard atmospheric pressure at sea level is approximately 1013.25 millibars or 29.92 inches of mercury.

Study Guide

Here are some key points to remember when studying atmospheric pressure:

1. Define atmospheric pressure and explain its causes.
2. Describe how altitude and temperature affect atmospheric pressure.
3. Explain the relationship between atmospheric pressure and weather patterns.
4. Identify the instruments used to measure atmospheric pressure.
5. Convert between units of atmospheric pressure (e.g., pascals, millibars, inches of mercury).

Understanding atmospheric pressure is crucial for comprehending weather patterns, air pressure systems, and their impact on the environment. Good luck with your studies!