Atmospheric Pressure

Also known as barometric pressure, atmospheric pressure refers to the force exerted by the weight of the atmosphere on the Earth’s surface. It is measured in units such as millibars, inches of mercury, or pascals. Atmospheric pressure varies with altitude and weather conditions. At sea level under standard conditions, the average atmospheric pressure is approximately 1013.25 millibars, or about 14.7 pounds per square inch. Changes in atmospheric pressure can affect weather patterns and are used in forecasting. For instance, low pressure systems are often associated with stormy weather, while high pressure systems often bring clear, calm conditions. Instruments called barometers are used to measure atmospheric pressure.