| A | B |
|---|
| Precipitation | The process by which water returns to the earth's surface in the form of rain, snow, etc. |
| Evaporation | The process in which liquid water changes into a gas or water vapor |
| Condensation | The process by which water vapor changes back to a liquid |
| Relative Humidity | The amount of moisture in the air compared to the amount it can hold at a given temperature |
| Rain Gauge | The straight sided container with a flat bottom that is used to measure rainfall |
| Air Mass | A large body of air with uniform properties throughout |
| Front | A boundary that is formed when two air masses with different properties meet |
| Thunder | What occurs when there is a violent expansion of the air that has been heated by lightning |
| Jet Stream | A strong, narrow band of wind with very fast-moving air that moves across the United States from west to east |
| Air Pressure | A measure of the force of the air pressing down on the earth |
| Cumulus Clouds | Fluffy, white clouds resembling balls of cotton that are usually associated with fair weather |
| Cirrus Clouds | Feathery, fibrous clouds made of ice crystals that are usually associated with fair weather |
| Stratus Clouds | Thick, layered gray clouds that usually cover the sky in an even blanket and are usually associated with rain and snow |
| Fog | What forms when condensed water from rivers, lakes, moist plants, or soil floats in the air near the ground |
| Smog | A form of air pollution appearing as a thick, brownish haze that is formed when carbon monoxide and other gases react in sunlight |
| Thunderstorm | A severe rainstorm that occurs when a cold front meets a warm front and cumulonimbus clouds form in the air |
| Tornado | A destructive funnel cloud moving over a narrow path of land |
| Lightning | A sudden discharge or spark of electricity between two clouds or between a cloud and the ground |
| Hurricane | Large tropical storms with high winds and heavy rain that can cause great damage as they move over land |
| Blizzard | A severe winter snowstorm that can cause near zero visibility with extremely low temperatures and high winds |
| Thermometer | A thick glass tube with a mercury or alcohol-filled bulb at one end that is used to measure the temperature |
| Barometer | The instrument used to measure air pressure |
| Anemometer | An instrument that includes three or four spinning, cone-shaped cups and is used to measure the speed of the wind |
| Weather Vane | An instrument that can be used to determine the wind's direction |
| Weather Map | A "picture" of weather conditions that a weather reporter uses as part of his or her forecast |
| Meteorologist | A scientist who studies the weather in order to predict what the weather will be |
| National Weather Service | An official government agency that issues advisories when severe weather has been observed or could occur |
| Climate | The average of all weather conditions of an area over a long period of time |
| Greenhouse Effect | The heating of the earth's atmosphere caused by a buildup of carbon dioxide when humans burn excessive amounts of fossil fuels |
| Groundhog | The animal which, according to myth, can forecast the weather by whether or not it sees its shadow on February 2 |
