| A | B |
|---|
| atmosphere | The envelope of gases that surrounds any astronomical body; gases surrounding the earth. |
| homosphere | The zone of a uniform mixture of gases closest to the earth's surface; extends from ground level to an altitude of about 50 miles. |
| heterosphere | The zone of the earth's atmosphere above the homosphere consisting of distinct layers of different gases; 50 miles into interplanetary space. |
| troposphere | The lowest temperature layer of Earth's atmosphere extending from ground level to about 6.8 miles. |
| lapse rate | The steady drop of temperature with altitude in the troposphere. |
| stratosphere | The temperature layer in the earth's atmosphere above the troposphere and below the mesosphere, extending from about 6.8 miles to about 31 miles. |
| jet stream | One of several belts of high speed winds in the stratosphere that wind snake-like across upper and midlatitudes in the Northern and southern hemispheres. |
| mesosphere | The temperature layer in the earth's atmosphere above the stratosphere and below the thermosphere, extending from 31 miles to 50 miles, containing the coldest temperatures in the atmosphere. |
| thermosphere | The hottest temperature layer in the earth's atmosphere above the mesosphere, extending from 50 miles to about 190 miles. |
| exosphere | Region of the atmosphere above the thermosphere where the atmosphere thins into interplanetary space. |
| ozone layer | A layer of concentrated ozone in the stratosphere that shields the earth from harmful ultraviolet light. |
| ionosphere | Region of variable height in the earth's upper atmosphere where solar radiation breaks gas molecules into ions. |
| magnetosphere | Geomagnetic field that surrounds the earth, originating in the earth's interior and extending to 100,000 miles. |
| solar constant | The rate of the flow of radiant energy from the sun through space to reach Earth. |
| radiation | Emission of electromagnetic waves, as with sunlight or heat lamps. |
| conduction | Heat transfer by direct contact between two substances. |
| convection | Heat transfer by the upward movement of a warmer, less dense fluid as it is displaced by a cooler, more dense fluid. |
| greenhouse effect | Warming of the lower atmosphere as it traps and absorbs infrared energy emitted by the ground and water from absorbed sunlight. |
| greenhouse gas | Normal atmospheric gases such as water vapor, carbon dioxide, and methane that contribute to the greenhouse effect. |
