Air Pressure and Weather Earth Science Mr. Bimber

Air pressure = force / area Barometer: air pressure meter. Barometer: air pressure meter. Isobar map: shows air pressure Isobar map: shows air pressure Sea Level air pressure: Sea Level air pressure: 14.7 PSI (pounds/square inch), found on tires in the US PSI (pounds/square inch), found on tires in the US. 1,013. mB (millibars), 1,013. mB (millibars), found on some weather maps 760 mm Hg (millimeters mercury), 760 mm Hg (millimeters mercury), found on older weather maps.

Temperature and pressure affect each other: If one changes… If one changes… …the other will, too. …the other will, too.

When air is compressed… …it gets hotter. …it gets hotter. Air compressors and bicycle tire pumps get hot when theyre used. In diesel engines, the fuel-air mix gets compressed in the cylinder until its hot enough to catch fire.

When air expands… it gets cooler. it gets cooler. CO2­ cartridges and fire extinguishers get cold when theyre used. CO2­ cartridges and fire extinguishers get cold when theyre used. In air conditioners and refrigerators: a gas expands in pipes inside the cold space. The same gas is compressed in pipes outside, where it gets hot. In air conditioners and refrigerators: a gas expands in pipes inside the cold space. The same gas is compressed in pipes outside, where it gets hot.

Humid air is less dense… so it floats upward. Dry air weighs more, so it sinks down.

Air temperature, pressure, and humidity together… form air masses with good or bad weather. form air masses with good or bad weather. High pressure air has: High pressure air has: Clear skies Gentle winds Good weather Low pressure air has: Low pressure air has: Clouds Strong winds Bad weather

Image Credits All images from: All images from: Commons.wikimedia.org Commons.wikimedia.org