| A | B |
|---|
| air | the mixture of gases that make up the Earth's atmosphere |
| atmosphere | a layer of gases that surrounds a planet |
| aerosols | microscopic solid particles or liquid droplets small enough to remain suspended in the atmosphere |
| air temperature | a measure of the average kinetic energy of air molecules |
| atmospheric pressure | the force applied by air on a unit area of a surface |
| aurora | a translucent curtain or streak of varicolored light that appears across the night sky when charged particles from the sun interact with the ions in the ionosphere |
| barometer | an instrument that measures atmospheric pressure |
| blackbody | an object that absorbs all radiation incident upon it and re-radiates energy according to the three laws of blackbody radiation |
| cirrus cloud | a wispy, elongate cloud that develops very high in the troposphere |
| cloud | a visible mass of condensed water vapor, consisting of tiny water droplets, ice crystals, or both, floating in the atmosphere |
| cloud cover | a measure of the percentage of the sky covered by cloud |
| collision coalescence | the process by which different-sized cloud droplets come into contact and merge with one another |
| cumulus cloud | a vertically growing cloud with cauliflower-like lobes |
| dew point | the temperature at which air will become saturated if it is cooled at constant pressure |
| Doppler radar | a radar system that detects precipitation and wind by transmitting microwave energy and measuring shifts in the frequency of the returned energy |
| electromagnetic radiation | energy that travels in the form of electric and magnetic fields and can pass through the vacuum of space |
| electromagnetic spectrum | the full range of possible frequencies or wavelengths of electromagnetic frequencies or wavelengths of electromagnetic radiation |
| environmental lapse rate | the rate at which environmental temperature changes with height in the atmosphere |
| fog | a cloud that forms at ground level |
| frequency | the number of waves that pass a point in a given time interval |
| freezing rain | supercooled water droplets that freeze on contact with the ground, trees, and wires |
| front | the boundary between air masses that differ in temperature and humidity |
| graupel | a small, soft ball of ice that results when an ice crystal collects supercooled water droplets that freeze on its surface |
| great oxygenation event | the dramatic increase in atmospheric oxygen, when Earth's surface rocks and water could no longer absorb or dissolve all the oxygen produced by photosynthetic organisms |
| greenhouse effect | the trapping of heat in the Earth's atmosphere by carbon dioxide and other greenhouse gases |
| greenhouse gas | atmospheric gases that absorb and re-emit infrared radiation |
| haze | murky humid air that exists when the air contains a relatively high concentration of aerosols |
| heterosphere | the upper portion of the atmosphere, in which gases separate into distinct layers on the basis of composition |
| homosphere | the lower part of the atmosphere, in which the gases have been stirred into a homogeneous mixture by air circulation |
| ionosphere | the region of the upper atmosphere that has a high concentration of ions |
| latent heat | the energy required for, or released by, a transition between two states of a substance |
| light scattering | the absorption of light, and its immediate re-emission in random directions, by molecules and particles in the atmosphere or ocean |
| mesosphere | the cooler layer of the atmosphere overlying the stratosphere |
| meteorologist | a person who studies and forecasts weather and its consequences |
| mirage | an optical illusion caused by specific atmospheric conditions that cause light rays to bend |
| ozone hole | an area of diminished ozone concentration in the stratosphere over the Antarctic polar region |
| phase change | the change of state of a substance |
| precipitation | atmospheric water that condenses to a liquid or solid state and falls from the sky |
| radiation | energy that travels away from its source through a medium or a vacuum |
| radiation window | a range of radiation wavelengths that can pass between the Earth and space without being absorbed by the atmosphere |
| rainbow | an arc in the sky displaying all colors of visible light, formed by the refraction and reflection of light through water droplets in the atmosphere |
| raindrop | a small, near-spherical ball of liquid water that is heavy enough to fall through the atmosphere |
| relative humidity | the ratio of the amount of water vapor in the atmosphere to the atmosphere's capacity for holding water vapor at a given temperature |
| saturation vapor pressure | the vapor pressure at which air is saturated at a given temperature |
| sleet | precipitation consisting of frozen raindrops |
| snowflake | a composite of hexagonal ice crystals that forms in the atmosphere |
| stratosphere | the layer of the Earth's atmosphere, in which the temperature increases with elevation, that lies directly above the troposphere |
| stratus cloud | a sheet-like, widespread cloud |
| thermometer | an instrument used to measure temperature |
| thermosphere | the hot outermost layer of the atmosphere containing very few gas molecules |
| troposphere | the layer of the Earth's atmosphere that extends from the Earth's surface to the tropopause and contains all the Earth's weather |
| vapor pressure | the part of the total atmospheric pressure exerted by water vapor molecules |
| visibility | the maximum distance from which a person with normal vision can distinguish objects when looking through the atmosphere |
| water vapor | water in its gaseous form |
| wavelength | the horizontal difference between two adjacent wave troughs or to adjacent wave crests |
| weather | local-scale atmospheric conditions as defined by temperature, atmospheric pressure, relative humidity, wind speed, and precipitation |
| wind | the horizontal movement of air |
| wind direction | the direction from which the wind blows |
| wind speed | the speed at which air moves horizontally across Earth's surface |
