| A | B |
|---|
| weather | the short-term state of the atmosphere, including temperature, humidity, precipitation, wind, and visibility |
| humidity | the amount of water vapor in the air |
| relative humidity | the ratio of the amount of water vapor in the air to the maximum amount of water vapor the air can hold at a set temperature |
| condensation | the change of state from a gas to a liquid |
| cloud | a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs |
| precipitation | any form of water that falls to the Earth’s surface from the clouds—rain, snow, sleet, hail |
| air mass | a large body of air where temperature and moisture content are constant throughout |
| front | the boundary between air masses of different densities and usually different temperatures |
| cyclone | an area in the atmosphere that has lower pressure than the surrounding areas and has winds that spiral toward the center |
| anticyclone | the rotation of air around a high-pressure center in the direction opposite to Earth’s rotation |
| thunderstorms | a usually brief, heavy storm that consists of rain, strong winds, lightning, and thunder |
| lightning | an electric discharge that takes place between two oppositely charged surfaces, such as between a cloud and the ground, between two clouds, or between two parts of the same cloud |
| thunder | the sound caused by the rapid expansion of air along an electrical strike |
| tornado | a destructive, rotating column of air that has very high wind speeds, is visible as a funnel-shaped cloud, and touches the ground |
| hurricane | a severe storm that develops over tropical oceans and whose strong winds of more than 120 km/h spiral in toward the intensely low-pressure storm center called the “eye” |
| thermometer | an instrument that measures and indicates temperature |
| barometer | an instrument that measures atmospheric pressure |
| anemometer | an instrument that measures wind speed |
| psychrometer | an instrument that measures relative humidity |
| wind vane | an instrument used to find the direction the wind is blowing |
