Air Pressure: A Key Weather Variable — Passage and Quiz

Air pressure is the force exerted by the weight of air molecules in the Earth’s atmosphere. It is a key weather variable because it influences wind patterns, cloud formation, and storm development.

Air pressure is caused by the gravitational pull of the Earth, which holds air molecules close to the surface. The more air molecules there are in a given area, the higher the air pressure. Air pressure decreases with altitude because there are fewer air molecules at higher elevations.

Air pressure is measured using a barometer. Traditional barometers use a column of mercury or aneroid cells that expand or contract with changes in pressure. Modern digital barometers use electronic sensors for more precise measurements.

The most common units for air pressure are millibars (mb) and inches of mercury (inHg). Millibars are used in scientific contexts, while inches of mercury are often used in weather reports. Standard air pressure at sea level is 1013.25 mb or 29.92 inHg.

Changes in air pressure are linked to weather conditions. High pressure usually brings clear skies and calm weather, while low pressure is associated with clouds, rain, and storms.

Fun fact: The lowest air pressure ever recorded was 870 mb during Typhoon Tip in the Pacific Ocean in 1979.