| Term | Definition |
|---|---|
| Air | The mixture of gases found in Earth’s atmosphere. Dry air is primarily nitrogen (N2 = 78%) and oxygen (O2 = 21%). |
| Altitude | The elevation above sea level. |
| Atmosphere | The gases that surround a planet or moon. On Earth, the air. |
| Climate | The average weather for a place over a long period of time (usually at least 30 years). |
| Clouds | A visible collection of water droplets in the atmosphere. Clouds usually form hundreds of meters above Earth’s surface but fog is a cloud formed near Earth’s surface. |
| Condensation | The process of change in state from gas to liquid, or the droplets of liquid formed from this process. |
| Energy | The ability to cause motion. Energy comes in many forms and is measured in joules |
| Evaporation | The process of change in state from a liquid to a gas. |
| Exosphere | The uppermost layer of the earth’s atmosphere. |
| Freezing | To change from a liquid to a solid state. |
| Front (Cold, Warm) | A boundary where a mass of air meets another air mass of a different temperature. |
| Gulf Stream | A strong ocean current that flows on the surface of the Atlantic Ocean from the Gulf of Mexico to northwestern Europe. |
| Humbity | The amount of water vapor in the air. |
| Hypothesis | A possible explanation of some phenomena, based on observations, and which suggests a means of being tested. |
| Landform | A feature of the earth’s surface such as a lake, stream, valley, canyon, hill, ridge, or mountain. |
| Latitude | The distance in degrees of a location north or south of the equator. |
| Melting | To change from a solid to liquid state. |
| Mesosphere | A layer of the earth’s atmosphere where temperature decreases with altitude; between the stratosphere and thermosphere. |
| Meteorologist | A scientist who studies the weather. |
| Ocean Current | Regular movements of large amounts of water in the ocean. |
| Precipitation | The movement of water, in solid or liquid form, from the atmosphere back to the surface of the earth. Rain, snow, sleet, and hail are examples. |
| Pressure (High, Low) | A force applied to a surface. It is measured in a force unit per area, such as psi (pounds per square inch) or millibars (100 newtons per square meter). |
| Prevailing Wind | The most common wind direction for a region. On the earth, the direction of the prevailing winds are related to the latitude of the region. |
| Stratosphere | The region of Earth’s atmosphere between the troposphere and mesosphere. |
| Thermosphere | The region of the atmosphere above the mesosphere in which temperature steadily increases with altitude. |
| Troposphere | The lowest layer of the earth’s atmosphere, where people live and most weather occurs. |
| Water Cycle | The movement of water from one state to another as it circulates through the earth’s crust, oceans, and atmosphere. |
| Water Vapor | Water in a gaseous state. |
| Weather | The condition of the atmosphere, including temperature, precipitation, and cloud cover, at a particular time and place. |
| Wind | The horizontal movement of air from areas of higher pressure toward areas of lower pressure. |
