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Atmospheric Chemistry Glossary

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Abatement - To lower, depreciate, or reduce. Often refers to emission reductions in air quality control. [Survey of Current Business; v74; 36-49; 1994.] [Journal of Environmental Economics and Management; v27; 38-48; 1994: DOI:10.1006/jeem.1994.1024]

Ablation - The weathering of a glacier by surface melting, or rock weathering by hydraulic erosion. [CATENA, v85, 194-204; 2011; DOI:http://dx.doi.org/10.1016/j.catena.2010.12.007] [Remote Sensing of Environment; v115, 1721-1732; 2011; DOI:10.1016/j.rse.2011.03.004]

Absorption Cross Section - A measurement of an atom or molecule's ability to absorb light at a specified wavelength, measured in square cm/particle. [Journal of Atmospheric Sciences; v50; 941-950; 1994.] [Atmospheric Environment; v45; 3007-3014; 2011; DOI:http://dx.doi.org/10.1016/j.atmosenv.2011.03.026]

Abstraction Reaction - a reaction that takes any atom away from another chemical species. Classical examples in atmospheric chemistry are the gas phase removal of hydrogen from methane by hydroxyl radical or the following solution phase reaction:

HSO3- + H2O2 ---> HSO4- + H2O

[Graedel, T.D. and Paul Crutzen. Atmospheric Change: an Earth system perspective; 1993; Freeman Press.] [Atmospheric Environment; v39; 7667-7688; 2005; DOI:10.1016/j.atmosenv.2005.03.019] [Atmospheric Environment; v32; 3393-3402;1998: DOI:10.1016/S1352-2310(98)80005-8] [Atmospheric Environment; v45; 1525-1531; 2011; DOI:10.1016/j.atmosenv.2010.12.045]

Accretion - The addition of air particles to hydrated drops (snow, rain, sleet, etc.) by coagulation as the drops fall through the sky. [Air Pollutants and Their Effects on the Terrestrial Ecosystem; v18 - Advances in Environmental Science and Technology Series; Hidy, ed.; pages 239, 240, 243; 1986; Wiley; New York.] [Journal of Geology; v102; 283-296; 1994.] [Engineering Applications of Artificial Intelligence; v25; 609-617;2012; DOI:10.1016/j.engappai.2011.11.004]

Accumulation Mode Particles - (Also known as secondary particles) These are particles that are formed in the atmosphere due to both the chemical and physical processes that take place with the interactions of primary gaseous emissions. The primary gaseous emissions are injected into the atmosphere by combustion processes such as from a car or from a coal burning plant. [Environmental Science Technology; v33; 3881-3886; 1999: DOI:10.1021/es981052f] [Energy Fuels; v16; 562; 2002.][Atmospheric Environment; v38; 2831-2840; 2004; DOI:10.1016/j.atmosenv.2004.02.039]

Acetaldehyde - C2H4O, a fairly simple aldehyde (second in the analogous series after formaldehyde) that is found in the atmosphere as a result of emissions from the manufacture of acetic acid, plastics, raw materials, and as a product in some polluted air oxidation reactions, for instance, acetaldehyde is found in urban air all over the world. [Food Control; v18; 988-995; 2007; DOI:10.1016/j.foodcont.2006.06.005][DOI:10.1016/S0925-5214(01)00093-X]

Acetic Acid - C2H4O2, a carbonyl compound that is emitted into the troposphere by both natural and anthropogenic processes. In the troposphere, acetic acid is present in the gas phase and is highly water soluble. Since acetic acid is highly water soluble, it is found in high concentration as acidic precipitation, such as in fog water and cloud droplets in urban areas. [Environmental Science Technology; v37; 446-453; 2003.] [Atmospheric Environment; v37; 117-128; 2003.]

Acetone - C3H6O, a carbonyl compound that is found in the atmosphere as a reactive gas. Acetone is considered to be a volatile organic compound (VOC), which is emitted into the atmosphere by industrial processes. Acetone has been linked to the formation of ozone in the troposphere due to the fact that it is a source of free radicals. [Geophysical Research Letters; v27; 2000; 22412244; DOI:10.1029/1999GL011288] [Environmental Science Technology; v35; 613-619; 2001; DOI:10.1021/es0012568][Atmospheric Environment; v65; 2013; 80-88; DOI:10.1016/j.atmosenv.2012.10.027]

Acid Deposition - a broad term that includes any forms of acids that accumulate in the atmosphere, for instance, acid rain, fog, haze. The term can be used to explain the long term effects of these events on the environment as well as the main causes of acid rain, fog or haze. The term functions as a category into which any aspect of anthropogenic acid in the environment can be placed. [Water Pollution Control Federation; v61; 188-189; 1989; JSTOR.] [Atmospheric Environment; v31; 1997; 4159-4168; DOI:10.1016/S1352-2310(97)00253-7]

Acidification - in the gas phase this process happens when compounds like nitrogen oxides and sulphur oxides are converted in a chemical reaction in the gas phase or in clouds into acidic substances. These acids are rained-out or dry deposited. Significant amounts of the compounds containing nitrogen and sulfur are a direct result of anthropogenic activity. An example reaction that takes place in soil occurs from the oxidation of reduced sulfur (for instance, pyrite) exposed during, for instance, strip mining of lignite. This can be represented as:

2FeS2 + 6H2O + 7O2 = 4SO42- + 8H+ + 2Fe(OH)2

[Bioresource Technology; v98; 2194-2200; 2007.] [Bulletin of the American Meteorological Society; 81; 1603-1609; 2000.] [Estuarine, Coastal and Shelf Science; v86; 2010; 157-164; DOI:10.1016/j.ecss.2009.11.022]

Acid-Pulse (Dry Deposition) - deposit of powder-like substance over the ground surface; especially effecting plant leaves; that when contacted by water has a very low pH. [Colin Baird. Environmental Chemistry; 1999; Freeman Press.] [Environmental Pollution; v139; 440-450; 2006; DOI:10.1016/j.envpol.2005.06.012] [Science of The Total Environment; v151; 241-247; 1994; DOI:10.1016/0048-9697(94)90473-1][Atmospheric Environment; 36; 2002; 537-560; DOI:10.1016/S1352-2310(01)00447-2]

Acid Rain - Acidified particulate matter in the atmosphere that is deposited by precipitation onto a surface, often eroding the surface away. This precipitation generally has a pH less than 5 and sometimes much lower depending on the concentration of acidic components. Oxides of sulfur and nitrogen contribute significantly to acid rain. [Nature; v367; 321; 1994; DOI:10.1038/367321a0] [Construction and Building Materials; v24; 2010; 1975-1983; DOI:10.1016/j.conbuildmat.2010.04.002] [Report of the Acid Rain Peer Review Panel July 1984.]

Acrolein (CH2CHCHO) - The simplest double-bonded aldehyde, produced in urban smog, contributing greatly to eye and lung irritation. It is a constituent of internal combustion engine exhaust, cigarette smoke, and biomass burning, and from the incomplete combustion of plastics and fuels. [Environmental Science Technology; v44; 7031–7036; 2010; DOI:10.1021/es101831r] [Environmental Science Technology; v36; 2227-2235; 2002; DOI:10.1021/es011394c]

Activation Energy - The energy barrier that must be overcome during a collision of two potential reactants in order for a reaction to occur. [Dyes and Pigments; v74; 458-463; 2007.][Bioresource Technology; v100; 209; 948-952; DOI:10.1016/j.biortech.2008.07.032] [Atmospheric Environment; v55; 2012; 98-106; DOI:10.1016/j.atmosenv.2012.02.019]

Active Chlorine - Active chlorine can be a single chlorine atom that is a radical ("Cl dot") and therefore highly reactive. It can also be a molecule containing chlorine that is reactive (ClO). Active chlorine's most notable role in atmospheric chemistry is in catalytic destruction of ozone in the stratosphere and the accumulation of active chlorine at the earth's polar stratosphere during the polar night that leads to major ozone hole formation during the spring. [Chemical Physics;
v358; 230-234; 2009; DOI:10.1016/j.chemphys.2009.02.005][Advances in Space Research; v43; 28-40; 2009; DOI:0.1016/j.asr.2008.06.006]

Adiabatic Lapse Rate - The rate of decrease of temperature with increasing altitude in the atmosphere. If heat is neither gained nor lost from the air parcel under consideration, then the lapse rate is said to be adiabatic and the energy to expand the volume of the parcel or rising air comes from the kinetic energy of the gas molecules in that parcel. The expansion of the parcel causes these molecules net kinetic velocity to decrease and this is equivalent to cooling the air. In dry air the dry adiabatic lapse rate is about 9.8 C/km (the sign is traditionally positive although the temperature is decreasing with altitude).See Foehn. In moist air the release of latent heat by condensation of the contained moisture makes the lapse rate lower, ~ 4 C/km. Surface temperature inversions are created when the lapse rate goes negative, that is, when the temperature profile of low lying tropospheric air increases with altitude. Air at the earth's surface is trapped there because the air above it is less warmer and less dense. This can be disastrous for the air quality in urban areas when anthropogenic pollutants are not mixed away from the surface and, instead, build up. [Graedel, T.D. and Paul Crutzen. Atmospheric Change: an Earth system perspective; 1993; Freeman Press.] [Monthly Weather Review; v135; 985-1005; 2007; DOI:10.1175/MWR3427.1] [Journal of Atmospheric Sciences; v64; 314-337; 2007; DOI:10.1175/JAS3849.1] [Deep Sea Research Part I: Oceanographic Research Papers; v50; 2003; 1523-1535; DOI:10.1016/j.dsr.2003.09.007]

Advection - To transport or carry. In air quality, the rate at which particulate matter is transported. [Journal of the Atmospheric Sciences; v51; 3109-3121; 1994.] [Deep-Sea Research ; v41; 243-261; 1994.] [Journal of Computational and Applied Mathematics; v111; 201-216; 1999; DOI: 10.1016/S0377-0427(99)00143-0]

Aerobic - Oxygen-dependent or requiring oxygen. [Journal of Experimental Biology; v194; 69-81; 1994.] [Journal of Bacteriology; v176; 5565-5570; 1994.] [Bioresource Technology; v99; 3279-3290; 2008; DOI:10.1016/j.biortech.2007.03.067]

Aerobic Respiration - Organisms utilize oxygen to break down components, derive energy, and generate needed biomolecules. Carbohydrates are cycled into water and carbon dioxide. The term aerobic refers to respiration in an organism in which oxygen is the final electron acceptor in the electron transport chain. Organisms that go through aerobic respiration require the presence of oxygen in order to produce ATP, the energy currency of the cell. Without ATP production the organism cannot survive. [Applied and Environmental Microbiology; v59; 2918-2926; 1993.] [Proceedings of the National Academy of Sciences of the United States America; v89; 10842-10846; 1992.]

Aerosol Particles - One of the components of an atmospheric air parcel, comprised of minute solids particles part of which is almost certainly water. [The Character and Origins of Smog Aerosols; v9 - Advances in Environmental Science and Technology Series; Hidey, ed.; page 234; 1980; Wiley; New York.] [Environmental Particles; v1 - Environmental Analytical and Physical Chemistry Series; J. Buffle and H. Van Leeuwen, Eds.; CRC Press; Boca Raton, FL.; pages 7, 30, 33; 1992.]

Aerosol Scavengers - Cloud droplets which attract an aerosol into snow, rain or some other water precipitate by coagulation and accretion. [Environmental Particles; v1 - Environmental Analytical and Physical Chemistry Series; Buffle and van Leeuwen, ed.; pages 7, 30-33, 54, 154; 1992; Lewis; Boca Raton, FL.] [Character and Origins of Smog Aerosols; v9 - Advances in Environmental Science and Technology Series; Hidy, ed.; John Wiley; New York; 1, 37, 148, 407, 425; 1980. ]

Afforestation - The process or act of changing land into forest by planting trees, seeding, etc. on land formerly used for something other than forestry. This can obviously be contrasted with deforestation. [American Forestry; v100; 23-25; 1994.] [New Scientist; v143; 30-35; 1994.] [Ecological Indicators; v32; 42-50; 2013; DOI:10.1016/j.ecolind.2013.03.009]

Agglomeration - A process by which atmospheric particles collide and stick to each other forming a new, often larger, particle. Many of the particles emitted from automobile tailpipes are agglomerations of smaller particles formed in the combustion process. [Atmospheric Environment; v42; 8113-8138; 2008; DOI:10.1016/j.atmosenv.2008.07.050][Atmospheric Environment; v42; 8113-8138; 2008; DOI:10.1016/j.atmosenv.2008.07.050]

Air Parcel - a volume of air, the component makeup and concentrations of which remain relatively static, that tends to travel around the earth changing geographic location and position above earth as an intact unit. Air parcels can be tracked [Graedel, T.D. and Paul Crutzen. Atmospheric Change: an Earth system perspective; 1993; Freeman Press.] [Journal of Climate; v19; 6267–6277; 2006.] [Journal of the Atmospheric Sciences; v63; 952–967; 2006.]

Air Pollution - The contamination of the atmosphere by any toxic or radioactive gases and particulate matter as a result of human activity. [Environmental Science and Technology; v28; 1633-1649; 1994.] [New Scientist; v143; 8; 1994.]

Air Quality Act of 1967 - The first national act in the United States to regulate emissions into the atmosphere; the act was closely related to a previous act created in 1963. The bill was created in response to growing urban areas that were having obvious pollution problems. [Laws and Contemporary Problems v33; 239-274; 1968.]

Air Quality Assessment - A prescribed level of atmospheric pollution allowed for a certain compound during a specific time in a specific geographical area. Standards are set by some regulating body, office or agency. [Environmental Science and Technology; v28; 378A-387A; 1994.] [Journal of Environmental Science; v57; 28; 1994.]

Air Quality Index (AQI) - An accounting or measurement of specified toxic levels of pollutants in the air. Based on the EPA air quality act, it gives the indicator (number) of different gas phase concentration levels to determine if it is hazardous to be outside or not, that is to breathe the air is a specific region. See alert levels. [School Library Journal; v53; 24; 2007.] [Journal of Environmental Management; v80; 230-236; 2006.] [Resource and Energy Economics; v28; 215-228; 2006.]

Aitken Particles - Small, condensed atmospheric matter, sometimes also known as nucleation mode particles, that are smaller than 0.1 µm in diameter. These particles are the most abundant in the atmosphere when classifying atmospheric particles by size. [Atmospheric Environment; v42; 6275-6283; 2008; DOI:10.1016/j.atmosenv.2008.01.063]

Albedo - Refers to reflection power or the portion of solar radiation that reaches a body (earth) surface and is immediately reflected back into the atmosphere. The uncertainty in the reflective power of clouds unfortunately increases the complexity of determining clouds' effects on modeling global warming. [New Scientist; v141; 16; 1994.] [Sky Telescope; v85; 84; 1993.]

Alert Levels - Also referred to as air quality index (AQI). This is a measure of different levels of concentration of air pollutants in the air. This index by another name was originally established in 1976. With each pollutant level, there is a warning depending on the concentration and its effects to the public. Alert levels can be found for any of five pollutants and the levels have color and number indicators that warn the public. The pollutants upon which the air quality index is based are ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The AQI levels are:

(>301) Maroon = Hazardous
(201-300) Purple = Very Unhealthy
(151-200) Red = Unhealthy
(101-150) Orange = Unhealthy for Sensitive Groups
(51-100) Yellow = Moderate
(0-50) Green = Good

[Journal of Health Economics; v23; 1209-1236; 2004; DOI:10.1016/j.jhealeco.2004.05.002]

Alternative Energy Source - Any energy source that can be harnessed without the use of burning fossil fuels. Such alternative sources are almost always a renewable energy source such as hydroelectric power, wind power, and solar power. [Renewable and Sustainable Energy Reviews; v11; 1571-1583; 2007.] [Renewable and Sustainable Energy Reviews; v11; 1312-1320; 2007.]

Amine-Based Carbon Dioxide Capture - Solutions containing primary, secondary, or tertiary amines can be used to dissolve and concentrate carbon dioxide from post-combustion CO2-rich gas streams from industrial combustion processes. CO2 is subsequently stripped from the amine solution in a concentrated stream for sequestration and the amine solution is recycled. Another version of this process simply uses ammonia. This process can be modified by using membrane tubes carrying the flowing capture solution. [International Journal of Greenhouse Gas Control; v14; 282-290; 2013; DOI:10.1016/j.ijggc.2013.01.028] [International Journal of Greenhouse Gas Control; v2; 9-20; 2008; DOI:10.1016/S1750-5836(07)00094-1]

Ammonia - The molecular formula for ammonia is NH3. Ammonia is one of the most important inorganic nitrogen compounds in atmospheric water droplets. It reacts with strong acids and is one of the only known basic, gas phase atmospheric components. Atmospheric ammonia can also enhance the nucleation rate and the production of new particles in the atmosphere. These new particles can be activated to become condensation nuclei and then, through various processes, grow to a particle size of 0.05 micrometer or larger which can then be effective as cloud condensation nuclei. This process can, therefore, affect the global radiation budget. The major sources of ammonia are decaying natural organic matter, livestock wastes, fertilizers, and industrial activity. [Atmospheric Change: an Earth system perspective; T.E. Graedel, Paul J. Crutzen; page 157; 1993; W.H. Freeman and Company; New York.] [Comptes Rendus Physique; v7; 1027-1045; 2006; DOI:10.1016/j.crhy.2006.10.018] [Icarus; v187; 510-519; 2007; DOI:10.1016/j.icarus.2006.10.022]

t-Amyl Methyl Ether (TAME) - Chemical formula of C2H5C(CH3)2OCH3 and an atomic weight of 102.18 amu. It is listed as a volatile organic compound that can form explosive vapor or air mixtures under certain conditions. TAME is being researched to replace MTBE as a cleaner fuel additive, to reduce the harmful effects to ground water system from leaking MTBE storage facilities as well as the exhaust. TAME is one of the by-products of purifying crude oil to petrol and it can cause moderate skin irritation as well as dizziness if inhaled. [Journal Chemical Engineering Data; v45; 319-323; 2000; DOI:10.1021/je990191p]

Anaerobic Respiration - Living or acting in the absence of oxygen. Cellular respiration in the absence of oxygen. [Microbiology; v140; 2153-2158; 1994.] [Journal of Bacteriology; v176; 5086-5092; 1994.]

Anoxic - The lack of oxygen such as the inadequate oxygenation of the blood (anoxia). In aquatic environmental chemistry it refers to water that has become oxygen poor due to the bacterial decay of organic matter. [Nature; v369; 729-731; 1994.] [Lancet; v344; 643-645; 1994.]

Antarctic Ozone Hole - Recent data suggest that due to the release into the atmosphere of CFCs by human activities, the ozone hole can as large as North America during a given astral spring. The CFCs are broken apart by UV light--to form free radicals of chlorine--after they have diffused into the upper stratosphere from the troposphere. This long term movement from the troposphere to the stratosphere is possible for these chlorine containing chemicals because of there long atmospheric lifetimes; however, this type of movement is not important for more reactive species such as tropospheric ozone because of their reactivity and therefore short atmospheric lifetime. In the Antarctic stratosphere, the reaction that converts reservoir species of chlorine into an active form--which destroys ozone--takes place on the surface of particles in polar stratospheric clouds as the temperature drops below about 200K. This is possible because of the unique isolation of the south polar vortex during the austral winter. The surfaces of these (nitric acid/water) clouds act as catalysts for reactions that release molecular chlorine which quickly photolyzes to chlorine's (radical) active state. It is this radical which destroys ozone. [Journal of Atmospheric Science; v51; 2846-2866; 1994.] [New Scientist; v139; 18; 1993.] [Geotimes; v38; 7; 1993.] [Science News; v144; 232-235; 1993.]

Antarctic Vortex - the combination of a drastic temperature and corresponding pressure drop along with the rotation of the Earth on its axis produces a spinning/rotating volume of air. The rotational speed of the winds commonly reaches as high as 180 mph. The motion of these winds form an impenetrable barrier such that the trapped air inside is unmixed, as it is separated from the air outside, and remains quite cold (temperatures drop below ?80 Celsius) until October. Inside the whirling volume of freezing air, the cold temperatures facilitate the condensation of gases into particles that eventually form polar stratospheric clouds. [Colin Baird. Environmental Chemistry; 1999; Freeman Press.] [Journal of the Atmospheric Sciences; v62; 581–588; 2005.] [Monthly Weather Review; v133; 1261–1278; 2005.]

Anthropogenic - Refers to something originating from humans and the impact of human activities on nature. [Science News; v146; 260; 1994.] [Environmental Science and Technology; v28; 422A-424A; 1994.]

Anthropogenic Forcing - Influence exerted on a habitat or chemical environment by humans. This obliquely refers to the idea of managed environment as opposed to a wild or non-disturbed environment. The variability of assumptions about radiative forcing can cause significant changes in the results from computer models that require an estimate of those values. [Science; v265; 1831-1838; 1994.] [Audubon; v96; 14; 1994.]

Anticyclonic Flow - The air flow produced about a high pressure center by the combination of two forces: the pressure gradient accelerating the air away from the center and the Coriolis force acting inward. Anticyclonic flows are clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. [Journal of the Atmospheric Sciences; v62; 3193-3212; 2005.]

Argon - Ar, an element that is a member of the 8A group (Noble Gases) of the periodic table. Argon is represented by the atomic symbol Ar, has an atomic number of 18, and an atomic weight of 39.948. It is colorless, odorless, and a very inert gas. It comprises about 1% of the Earth's atmosphere. [Chemical & Engineering News; v73; 8; 1995.] [Chemistry The Central Science; Brown, Theodore; Lemay, H. Eugene; Bursten, Bruce; 846; 1994; Prentice Hall; Englewood Cliffs, New Jersey.]

Aromatic Hydrocarbons - Hydrocarbon compounds in which the carbon atoms are connected by a ring structure that is planar and joined by sigma and pie bonds between the carbon atoms. An example of an aromatic compound is benzene, C6H6. [American Industrial Hygiene Association Journal; v58; 661-66; 1997.] [Chemistry The Central Science; Brown, Theodore; Lemay, H. Eugene; Bursten, Bruce; 970-72; 1994; Prentice Hall; Englewood Cliffs, New Jersey.]

Asbestos - A naturally occurring fibrous mineral found in certain types of rock formations. The primary use of asbestos was as a fireproofing material, applied to structural steel members in multistory commercial buildings to attain proper fire protection. With its resistance to heat, asbestos was able to keep the building structure from bending and warping if exposed to fire. After widespread use of asbestos, over a 15 to 25 year time span, a pattern of illness gradually began to occur in asbestos workers. Three diseases linked to asbestos exposure are asbestosis, a fibrous scarring of the lungs, lung cancer, and mesothelioma, a cancer of the lining of the chest or abdominal cavity. [Indoor Air Quality; Hays, S. M., Gobbell, R. V., Ganick, N. R.; McGraw-Hill, New York, 1995.]

Assimilation Cycle - A natural process by which a water body uses microbes, which convert nonliving substances into protoplasm or cells, to purify itself from pollutants. [Environmental Science and Technology; v26; 1864-1875; 1992.] [Environmental Science and Technology; v27; 1719-1728; 1993.] [Nature; v362; 592-593; 1993.]

Atmosphere - The sum total of all the gases surrounding the Earth, extending several hundred kilometers above the surface in a mechanical mixture of various gases in fluid-like motion. The permanent constituents are molecular nitrogen; 78.1%, molecular oxygen; 20.9%, argon; 0.934%, and approximately 0.037% carbon dioxide (but this is increasing...). Various other components exist in trace amounts. Not to be under emphasized, these trace components are where the interesting atmospheric chemistry occurs. The atmosphere can also be artificially divided into layers. Example: the troposphere (the layer closest to the earth) and the stratosphere (the layer above the troposphere). [Elements of Meteorology; Miller, Albert and Thompson, Jack; pp. 6-9; 1970; Charles E Merrill; Ohio.] [Climate Systems Modeling; Salby, Murry; Ed. Kevin E. Trenberth; 53-115; 1992; Cambridge University Press; London.]

Atmospheric Chemistry - The scientific study of the relationships and interactions of the substances in the gases around the earth. Examples would be determination of the concentrations, sources, and sinks of ozone in the troposphere and stratosphere and the greenhouse gases that surround earth. This includes all reactions of and sources and sinks on the surface of the earth of particles released in the air. [Journal of Physical Chemistry A; v110; 7777-7786; 2006] [Atmospheric Environment; v41; 2319-2334; 2007.] [Science of The Total Environment; v360; 5-25; 2006.]

Atmospheric Convection - Process in which heat energy is transported through a medium, usually a gas or liquid. An example, in the atmosphere occurs when warm air with a lower density experiences an upward force until it cools and its density matches the surrounding air, generally termed convection cells. [A Field Guide to the Atmosphere; Day, John and Schaefer, Vincent; 65-74; 1981; Houghton Mifflin; Boston.] [Dictionary of Astronomy, Space and Atmospheric Phenomena; Tuer, David; 56; 1979; Van Nostrand Reinholds; NY.]

Atmospheric Window - This is a gap in the atmosphere's spectral absorption. It is created because not enough molecules in the atmosphere are absorb in the wavelengths 8-12 micrometers. Absorption is caused by the molecules in the air, therefore adding more gases to the atmosphere the window can become reduced and cause more of these wavelengths to stay in earths atmosphere causing global warming. [AMBIO; v27; 187-197; 1998.] [Sensors and Actuators B: Chemical
v125; 214-223; 2007; DOI:10.1016/j.snb.2007.02.018]

Austral Spring - Related to Antarctic ozone depletion, this denotes the season of spring in the southern hemisphere when the greatest amount of ozone is lost, generally beginning in September. Astral relates to the hemisphere that the observer is currently in and the season that relates to the observer, while austral refers to the south. [Glossary of Astronomy and Astrophysics; Hopkins, Jeanne; 51; 1976; University of Chicago; Chicago.] [Encyclopedia of Astronomy; Satterthwaite, Gilbert; 29; 1971; St. Martins Press; NY.] [Advances in Space Research; v6; 89-98; 1986.]

Autumnal Equinox - Point at which on the celestial sphere that the equator and the Ecliptic intersect. Generally the autumnal equinox occurs on or about September 23 in the northern hemisphere; this also signifies spring in the southern hemisphere. [Encyclopedia of Astronomy; Satterthwaite, Gilbert; 29; 1971; St. Martins Press; NY.] [Glossary of Astronomy and Astrophysics; Hopkins, Jeanne; 51; 1976; University of Chicago; Chicago.] [Journal of Atmospheric and Solar-Terrestrial Physics; v66; 463-479; 2004.] 

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