| A | B |
|---|
| water cycle | the movement of water through the Earth’s systems |
| evaporation | the process by which molecules of liquid water escape into the air and become water vapor |
| condensation | when water vapor becomes liquid water |
| humidity | a measure of the amount of water vapor in the air |
| relative humidity | the percentage of water vapor that is in the air compared to the maximum amount of water vapor the air can hold |
| psychrometer | this measures relative humidity |
| dew point | the temperature at which condensation begins |
| cirrus clouds | wispy, feathery clouds |
| cumulus clouds | clouds that look like cotton |
| stratus clouds | clouds that form in flat layers |
| nimbostratus clouds | stratus clouds that thicken and produce drizzle, rain, or snow |
| precipitation | any form of water that falls from clouds and reaches Earth’s surface |
| rain gauge | an open-ended tube that collects rain |
| flood | an overflowing of water in a normally dry area |
| drought | a long period of scarce rainfall or dry weather |
| air mass | a huge body of air in the lower atmosphere that has a similar temperature, humidity, and air pressure at any given height |
| tropical | warm air mass that forms in the tropics and has low air pressure |
| polar | a cold, air mass that forms 50 degrees north latitude and south of 50 degrees south latitude |
| maritime | air masses that form over oceans |
| continental | air masses that form over land |
| jet streams | bands of high-speed winds about 10 kilometers above the Earth’s surface |
| front | the boundary where the air masses meet |
| occluded | when a warm air mass is cut off from the ground |
| storm | a violent disturbance in the atmosphere |
| thunderstorm | a small storm with heavy precipitation, thunder, and lightning |
| lightning | a sudden spark, or electrical discharge, as these charges jump between parts of a cloud |
| hurricane | a tropical cyclone with winds of 119 km/h or higher |
| storm surge | a dome of water that sweeps across the coast where the hurricane lands |
| tornado | a rapidly whirling, funnel-shaped cloud that reaches down from a thunderstorm to touch the Earth’s surface |
| evacuate | to move away from an area temporarily |
