| A | B |
|---|
| air mass | A huge body of air that has similar temperature, humidity, and air pressure at any given height |
| anticyclone | A high-pressure center of dry air |
| cirrus | Wispy, feathery clouds made of ice crystals that form at high levels |
| condensation | The change of state from a gas to a liquid |
| continental (air mass) | A dry air mass that forms over land |
| cumulus | Fluffy, white clouds, usually with flat bottoms, that look like rounded piles of cotton. |
| cyclone | A swirling center of low air pressure |
| dew point | The temperature at which condensation begins |
| drought | A long period of low precipitation |
| evacuate | Moving away temporarily from an area about to be affected by severe weather |
| evaporation | The process by which molecules at the surface of a liquid absorb enough energy to change to a gas |
| flood | An overflowing of water in a normally dry area |
| front | The boundary where unlike air masses meet but do not mix |
| humidity | The amount of water vapor in a given volume of air |
| hurricane | A tropical storm that has winds of about 119 km/h or higher |
| isobar | A line on a weather map that joins places that have the same air pressure |
| isotherm | A line on a weather map that joins places that have the same temperature |
| jet stream | Bands of high-speed winds about 10 km above Earth’s surface |
| lightning | A sudden spark, or energy discharge, caused when electrical charges jump between parts of a cloud, between nearby clouds, or between a cloud and the ground. |
| maritime | A humid air mass that forms over oceans |
| meteorologist | Scientists who study the causes of weather and try to predict it |
| occluded | Cut off, as in a front where a warm air mass is caught between two cooler air masses |
| polar (air mass) | A cold air mass that forms north of 50 degrees north latitude or of 50 degrees south latitude |
| precipitation | Any form of water that falls from clouds and reaches Earth’s surface as rain, snow, sleet, or hail |
| psychrometer | An instrument used to measure relative humidity |
| rain gauge | An instrument used to measure precipitation |
| relative humidity | The percentage of water vapor in the air compared to the maximum amount of water vapor that air can contain at a particular temperature. |
| storm | A violent disturbance in the atmosphere |
| storm surge | A “dome” of water that sweeps across the coast where a hurricane lands |
| stratus | Clouds that form in flat layers and often cover much of the sky |
| thunderstorm | A small storm often accompanied by heavy precipitation and frequent thunder and lightning |
| tornado | A rapidly whirling, funnel-shaped cloud that reaches down to touch Earth’s surface |
| tropical (air mass) | A warm air mass that forms in the tropics and has low air pressure |
| water cycle | The continual movement of water among Earth’s atmosphere, oceans, and land surface through evaporation, condensation, and precipitation |
