The Online Library of Knowledge

Weather and climate

Weather A-Z

Air   The mixture of gases, mostly nitrogen and oxygen, that surrounds the Earth.

Air mass   A large body of air of a similar temperature and moisture content. Air masses are separated by fronts

Air pressure   The weight of air pressing down on the Earth. Air pressure is low where air masses are rising. The rising air will cool and condense, forming rain clouds. Pressure is higher where air masses are sinking. High air pressure is usually accompanied by dry weather.
