| A | B |
|---|
| Air | the invisible mixture of gases surrounding the Earth |
| Air pressure | the force with which air presses against surfaces |
| Atmosphere | the blanket of gases surrounding the Earth, including the air we breathe |
| Forecast | a statement about what the weather should be like during the next few days |
| isobar | a line on a weather map connecting places of equal air pressure |
| meterorologist | a scientist who studies the Earth's atmosphere to report and predict the weather |
| molecules | a small particle made of two or more atoms |
| vapor | water in the form of a gas |
| weather | the local condition of the atmosphere, such as hot, rainy, windy, or sunny |
| meteorology | the discipline dealing with the Earth's air, especially the movements and events that cause weather |
| cirrus | a thin, high, featherlik cloud forming very high in the atmosphere |
| convection | the upward movement of air caused by heat from the Earth; the air cools as it rises, the sinks back toward Earth |
| front | the boundary between two air masses |
| stratus | a flat, sheetlike rain cloud spreading over the sky |
| air mass | a large body of air in the atmosphere that has about the same humidity and temperature |
| dew point | the temperature at which water vapor turns to water droplets |
| evaporation | the process by which a liquid is changed into a vapor or gas |
| humidity | the amount of water vapor in the air |
| precipitation | moisture condensed from vapor by cooling, such as dew, rain, hail, and snow |
| cumulonimbus | a rain-producing cloud with an anvil-shaped top |
| cumulus | a fair-weather cloud rounded on the top and flat on the bottom |
| isotherm | a line on a weather map connecting places having the same temperature |
| lightning | discharge of electricity between clouds or betweeen clouds and the ground, seen as a flash of light |
| thunder | a loud noise caused by lightning expanding and contracting the air |
| barometer | an instrument which measures air pressure at a particular location |
| millibar | a unit by which air pressure is measured |
| aneroid barometer | a small modern barometer which measures changes in air pressure, causing a pointer to move along a scale |
