| A | B |
|---|
| wind | the horizontal movement of air from an area of high pressure to an area of lower pressure |
| Coriolis effect | the change that Earth's rotation causes in the motion of objects and that explains how winds curve |
| land breeze | the flow of air from land to a body of water |
| sea breeze | the flow of cooler air from over an ocean or lake toward land |
| air pressure | the pressure caused by the weight of a column of air pushing down on an area |
| temperature | a measure of how hot or cold an object is compared to a reference point |
| 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 |
| saturation | air with a relative humidity of 100% |
| thermometer | an instrument used to measure temperature |
| barometer | an instrument used to measure changes in air pressure |
| anemometer | an instrument used to measure wind speed |
| psychrometer | an instrument used to measure relative humidity |
| evaporation | the process by which water molecules in liquid water escape into the air as water vapor |
| condensation | the process by which molecules of water vapor in the air become liquid water |
| precipitation | any form of water that falls from clouds and reaches Earth's surface |
| runoff | excess water that cannot be absorbed by the soil |
| rain | drops of water; most common type of precipitation |
| snow | when water vapor in a cloud is converted into ice crystals called snowflakes |
| sleet | when raindrops fall through a layer of air below zero degrees and freeze into solid particles of ice |
| hail | round pellets of ice larger than 5 millimeters in diameter |
| cloud | when warm moist air rises and cools and condenses into liquid water or ice crystals |
| air mass | a huge body of air that has similar temperature, humidity, and air pressure at any given height |
| high pressure | cold, dense air |
| low pressure | warm, less dense air |
| front | the boundary where air masses meet |
| warm front | when a warm air mass overtakes a slow-moving cold air mass |
| cold front | when a fast-moving cold air mass overtakes a warm air mass |
| hurricane | a tropical storm that has winds of about 119 kilometers per hour or higher |
| tornado | a rapidly whirling, funnel-shaped cloud that reaches down to touch 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 |
| weather map | a snapshot of conditions at a particular time over a large area |
