OPLDatabaseFile 0P:`.Ar 3 pROM::BJ.WDR%P@Term Definition  absorption coefficientA measure of the amount of radiant energy, incident normal to a planar surface, that is absorbed per unit distance or unit mass of substance.accessory cloudA cloud which is dependent on a larger cloud system for development and continuance. Roll clouds, shelf clouds, and wall clouds are examples of accessory clouds.  acid rainSynonymous with acidic deposition. Both are somewhat inaccurate versions of the phrase "deposition of acidifying substances from the atmosphere." Acidity is measured as the concentration of hydrogen ion (H+), in logarithmic pH units. Solutions having pH < 7.0 are acidic, but "acid rain" is usually considered to have pH < 5.65 because of the natural influence of carbonic acid in precipitation. acid shockShort-term event of great acidity that occurs in freshwater systems receiving intense pulses of acidic water when the snowpack melts. acidificationIncrease over time in the content of acidity in a system, accompanied by decreases in the acid-neutralizing capacity due to alkalinity and decreases in calcium and magnesium content.oactive species_Trace constituent in the stratosphere that is directly involved in catalytic ozone destruction.adiabatic processA thermodynamic change of state of a system such that no heat or mass is transferred across the boundaries of the system. In an adiabatic process, expansion always results in cooling, and compression in warming.6 advectionThe predominately horizontal large-scale movement of air that causes changes in temperature or other physical properties. In oceanography, advection is the horizontal or vertical flow of sea water as a current. Transport of a property by fluid motion; in +meteorology, referring to horizontal flow.aerosolParticulate material, other than water or ice, in the atmosphere ranging in size from approximately 10E-3 to larger than 10E2 micrometers in radius. Aerosols are important in the atmosphere as nuclei for the condensation of water droplets and ice crystals, as participants in various chemical cycles, and as absorbers and scatterers of solar radiation, thereby influencing the radiation budget of the earth-atmosphere system, which in turn influences the climate on the surface of the Earth. agglomerationIn meteorology, the process by which precipitation particles grow larger by collision or contact with cloud or other precipitation particles. air pollutionOne or more contaminants in concentrations or durations that are injurious to human, animal, plant, and property or that impair the enjoyment of life or property.airborne particulatesTotal suspended matter found in the atmosphere as solid pieces or liquid droplets. Airborne particulates include windblown dust, emissions from industrial processes, smoke from the burning of wood and coal, and the exhaust of motor vehicles.airmassA widespread body of the atmosphere that gains certain meteorological or polluted characteristics while set in one location. The characteristics can change as it moves.]albedoUThe fraction of the total solar radiation incident on a body that is reflected by it. albedo effectIncreased reflectivity of the ground surface following removal of the vegetation (desertification) thereby changing the heat balance of the surface-atmosphere system and, although unproven, assumed by some meteorologists to result in less uplift and less rain.haltithermal periodA period of high temperatures, particularly the one from 8000 to 4000 BP (before the present era), which was apparently warmer in summers, as compared with the present, and with the precipitation zones shifted poleward. More rainfall occurred in most of Tthe subtropical United States and Scandinavia. Also called the hypsithermal period.Lannual flood series7Maximum instantaneous discharge in each year of record.Antarctic Circumpolar CurrentThe largest circulation feature in the ocean in terms of both its sustained transport and its length. Whereas both the North Atlantic and North Pacific have distinct subpolar gyres, the southern hemisphere systems are masked by the circumglobal flow of the Antarctic Circumpolar Current, which is more similar to unbounded atmospheric flows. Also know as the West Wind Drift in reference to its general orientation down the prevailing winds. The availability of a more or less continuous circumglobal channezl at approximately 55-60 S allows the current to connect the three major ocean basins -- Atlantic, Pacific, and Indian.Antarctic ConvergenceSharp oceanographic boundary between latitudes 50 S and 60 S in the southern ocean, separating colder and less saline waters around the Antarctic continent from warmer and denser waters to the north. anthropogenicLiterally, "giving rise to humanity," but more commonly used to signify "human-induced." Usually used in the context of emissions that are produced as the result of human activities. anticycloneAn atmospheric high-pressure closed circulation with clockwise rotation in the Northern Hemisphere, counterclockwise in the Southern Hemisphere, and undefined at the Equator.+ Arctic hazeA persistent winter diffuse layer in the Arctic atmosphere whose origin may be related to long-range transport of midlatitude continental man-made pollutants. Industrial air pollution transported to the Arctic from mid- and high-latitude sources; primarily composed of sulfur compounds, visible as a yellow-brown layer over most of the Arctic mainly during the months of February, March, and April. The haze, first observed in 1957, is a result of pollution from Europe and Asia that migrates north in the late winter and spring. It grew yearly until 1982, then began a decline that probably stems from Russia's increased reliance on natural gas instead of coal and oil, as well as tighter pollution controls in western Europe. As of 1993, the haze had declined to about half its 1982 value.aridClimate or region where the precipitation is barely sufficient to support vegetation. Aridity (also hyperaridity and semiaridity) may be defined by means of climatic diagrams or by various aridity indices (formulae involving precipitation, evapotranspiration, and temperature). Sometimes characterized as receiving either 80-150 mm or 200-350 mm annual precipitation, depending on the climatic regime.? assimilation1Process of CO2 fixation by photosynthetic tissue.atmosphere (the)The envelope of air surrounding the Earth and bound to it by the Earth's gravitational attraction. Studies of the chemical properties, dynamic motions, and physical processes of this system constitute the field of meteorology.atmosphere (unit) standard unit of pressure representing the pressure exerted by a 29.92-in. column of mercury at sea level at 45 latitude and equal to 1000 g/cm2.atmospheric turbulenceA state of the flow of air in which apparently random fluctuations occur in the air's instantaneous velocities, often producing major deformations of the flow.atmospheric windowxThe spectral regions between 8.5 and 11.0 microns where the atmosphere is essentially transparent to longwave radiation.available soild moistureThat portion of the total water held in the soil that can be extracted for use by the plant, i.e., with a water potential usually above -1.5 mPe.D backing windsWinds which shift in a counterclockwise direction with time at a given location (e.g. from southerly to southeasterly), or change direction in a counterclockwise sense with height (e.g. westerly at the surface but becoming more southerly aloft). The opposite of veering winds. In storm spotting, a backing wind usually refers to the turning of a south or southwest surface wind with time to a more east or southeasterly direction. Backing of the surface wind can increase the potential for tornado development5 by increasing the directional shear at low levels. baroclinic wavesAtmospheric waves with wavelengths of about 1000 km which draw their energy from the energy accumulated due to the north-south global temperature differences.w baroclinityjHorizontally varying density along an isobaric surface, mostly due to the horizontal temperature gradient.O Benard cellBConvection cells that occur in unstable fluids, initially at rest.?Bergeron processProcess by which ice crystals grow at the expense of supercooled water droplets, coexisting in a cloud with temperatures below 0 C. Because vapor pressure over water is greater than over ice at a common temperature, if supercooled water is sufficiently a-vailable, ice grows at the expense of water.Rbimodal distributionction in the South Atlantic, South Pacific, and Indian Ocean. Hadley cellA direct thermally-driven and zonally symmetric large-scale atmospheric circulation first proposed by George Hadley in 1735 as an explanation for the trade winds. It carries momentum, sensible heat, and potential heat from the tropics to the midlatitudes (30). The poleward transport aloft is complemented by subsidence in the subtropical high-pressure ridge and a surface return flow. The variability of this cell and the Walker cell is hypothesized to be a major factor in short-term climatic change.hailRoundish ice mass consisting of concentric layers of ice formed on a mineral nucleus; hard, may be lumpy; diameters of 5 cm or more, though most of the hail measured at the earth's surface is less than 0.5 cm in diamter.Y half-lifeNTime after which half of the radioactive atoms initially present have decayed.vhalopA colored ring, appearing 22 or 46 around the sun or moon, caused by refraction of light through ice crystals.halonsCompounds containing only carbon, bromine, and one or more other halogens (chlorine, fluorine). Completely halogenated hydrocarbons with at least one bromine atom, usually having long lifetimes and mostly used as fire retardants.fheat flux (thermal flux)LThe amount of heat that is transferred across a unit area in a unit of time.heat island effectlA "dome" of elevated temperatures over an urban area caused by the heat absorbed by structures and pavement.K heat sink@That portion of a thermodynamic system that absorbs unused heat.VhertzOThe unit of frequency equal to one cycle per second or 2 pi radians per second.heterogeneous chemistryChemical transformations involving reactants (including catalytic agents) in different phases. For example, ClNO3 + HCl(solid) ---> Cl2 + HNO3(solid) or ClNO3 + H20(solid) ---> HOCl + HNO3(solid).HFHigh frequency (~3-30 MHz)gHolocene]The most recent epoch of the Quaternary period, covering approximately the last 10,000 years.) hook echoA radar reflectivity pattern characterized by a hook-shaped extension of a thunderstorm echo, usually in the right-rear part of the storm (relative to its direction of motion). A hook often is associated with a mesocyclone, and indicates favorable conditions for tornado development.  hurricaneA violent tropical cyclone storm of the western Atlantic. A tropical storm with pronounced rotary circulation, constant wind speed of 74 miles per hour (64 knots) or more.rhydrologic budget_A quantitative accounting of all water volumes and their changes with time for a basin or area.hydrologic cycleThe process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions.@ hydrometeor3Any form of precipitation (snow, rain, hail, etc.).U hydromiteJAn ice cylinder, like a cave stalagmite, formed by falling drops of water. hydrosphereThe aqueous envelope of the Earth, including the oceans, freshwater lakes, rivers, saline lakes and inland seas, soil moisture and vadose water, groundwaters, and atmospheric vapor.hydrostatic equationIn the vector equation of motion, the form assumed by the vertical component when all Coriolis, earth-curvature, frictional, and vertical-acceleration terms are considered negligible compared with those involving the vertical pressure force and the force of gravity. The error in applying the hydrostatic equation to the atmosphere for cyclonic-scale motions is less than 0.01%. In extreme situations, the strong vertical accelerations in thunderstorms and mountain waves can be 1% of gravity.E hygroscopic8Absorbing or attracting moisture, as with salt crystals.ice ageA glacial epoch or time of extensive glacial activity. Also, as Ice Age, which refers to the latest glacial epoch, the Pleistocene Epoch. Periods characterized by very low temperature worldwide and advancing glaciers.ice and snow albedoThe reflectivity of ice and snow-covered surfaces. The albedo of freshly fallen snow may be as much as 90%, while older snow may have values of 75% or less. The larger the areal extent of snow and ice cover, the higher the albedo value. The surface albedo will also increase as a function of the depth of snow cover up to 13 cm and be unaffected by increased snow cover after reaching that depth.$(ice and snow albedo temperature feedbackInteractions that can be described as a theoretical concept of a feedback mechanism in which the interacting elements are the areal extent of polar ice and snow cover, the albedo of the polar region (dependent on areal extent of ice and snow), absorption of solar radiation (dependent on the albedo), temperature (dependent on the absorption of solar radiation), and the area of ice and snow cover (dependent on temperature). Less snowfall would mean more absorption of solar radiation, therefore a surface warming would occur. Climate modeling studies indicate an amplification effect (i.e., positive feedback) of the ice and snow albedo feedback on increased surface air temperatures caused by increases in the atmospheric concentrations of carbon dioxide.ice coreDeep drill into the earth's permanent glaciers revealing the history of the atmospheric gas and dust content, enabling deduction of former atmospheric temperatures. ice coverDuring the present time, the extent, especially the thickness, of glacier ice on a land surface. Also the same as ice concentration, which is the ratio of an area of sea ice to the total are of sea surface within some large geographic area. ice islandsTabular icebergs that have broken off the ice shelves of northern Ellesmere Island; can be up to 60 m thick and 30 km wide, drift with the pack ice, and have been known to last for as much as three decades. ice sheetA glacier of considerable thickness and more than 50,000 sq. km in area. It forms a continuous cover of ice and snow over a land surface. An ice sheet is not confined by the underlying topography but spreads outward in all direction. During the Pleistocene Epoch, ice sheets covered large parts of North America and northern Europe but they are now confined to polar regions (e.g., Greenland and Antarctica). Also called continental glacier.I ice shelfA sheet of very thick ice with a level or gently undulating surface. It is attached to the land on one side, but most of it is floating. On the seaward side, it is bounded by a steep cliff (ice front) two to 50 m or more above sea level. Ice shelves have formed along polar coasts (e.g., Antarctica and Greenland); they are very wide, with some extending several hundreds of kilometers toward the sea from the coastline. They increase in size from annual snow accumulation and seaward extension of land glacie>rs. They decrease in size from warming, melting, and calving.~ ice streamrLarge, fast glaciers embedded in slow-moving ice. Flow velocities are a few hundred meters to kilometers per year.icebergA floating ice mass up to 100 km long and 200-300 M thick that has broken off (calved) from ice shelves, glaciers, or coastal ice cliffs into the ocean.incoherent scatter radarSensitive radar operating on a frequency well above the critical frequency that detects radio signals scattered from refractive index irregularities in the ionospheric and/or neutral atmosphere.incoming solar radiationElectromagnetic radiation emitted by the sun that is incident on the earth's upper atmosphere. Most of the incoming solar radiation is in the spectral region 0.3-5 microns. The earth's atmosphere is largely transparent to the incoming solar radiation and permits most of it to reach the surface (the rest is reflected back to space by clouds and the surface). At the surface, the incoming solar radiation is absorbed and heats the surface.Vindex of variability@Standard deviation of the annual flood series in the log domain.[infrared emissionHLight in the infrared region of the spectrum emitted by a heated sample.pinfrared radiationElectromagnetic radiation lying in the wavelength interval from 0.7 microns to 1000 microns. Its lower limit is bounded by visible radiation, and its upper limit is bounded by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at infrared wavelengths. Infrared radiation is generated almost entirely by large-scale intramolecular processes. The tri-atomic gases, such as water vapor, carbon dioxide, and ozone absorb infrared radiation and play important roles in the propagati\on of infrared radiation in the atmosphere. Abbreviated IR; also called longwave radiation.|infrared spectroscopyeInteraction of infrared radiation with a sample, usually to excite vibrational modes of the material.U insolationThe solar radiation incident on a unit horizontal surface at the top of the atmosphere; sometimes referred to as solar irradiance. The latitudinal variation of insolation supplies the energy for the general circulation of the atmosphere. Insolation dependIs on the angle of incidence of the solar beam and on the solar constant. instabilityA layering of the atmosphere that tends toward vertical overturning. Property of a system such that certain distrubances or perturbations introduced into the steady state will increase in magnitude; tendency of an atmosphere to overturn, enhanced by some disturbance or perturbation; specifically when a parcel of air, being lifted, encounters ambient air cooler than itself and thereafter rises of its own accord.Internal energy in the form of heat released when a change of state occurs from gas to liquid or liquid to solid. Heat is required to bring about a change of state from solid to liquid or liquid to gas. inversionAn anomaly in the normal positive lapse rate; usually refers to a thermal inversion, in which temperature increases rather than decreases with height.5ion0An atom or molecule that has an electric charge.d ionosphereXIonized gas (plasma) that surrounds the earth from approximately 90 to 600 km in height. irradiancezThe total radiant flux received on a unit area of a given real or imaginary surface. Also called the radiant flux density.isobarLine of constant barometric pressure, usually on a map at a given height. (An isobaric surface is a three-dimensional surface of constant pressure.)RisopynicHA line on a chart that connects all points of equal or constant density. isostatic adjustmentThe process whereby lateral transport at the Earth's surface from erosion or deposition is compensated for by movements in a subcrustal layer to maintain equilibrium among units of varying masses and densities. Also called isostatic compensation.isostatic sea level changeChange in relative sea level associated with a local radial displacement of the surface of the solid earth as, for example, may occur elastically in the near field of an earthquake source or viscously in response to glacial loading or unloading.:isotach1Line or surface on which velocities are constant.VisothermLA line on a chart that connects all points of equal or constant temperature.' jet streamA fast-moving ribbon of air that occurs near the top of the troposphere; width is 25-100 km, thickness 1-3 km, and velocity 99-300 km per hour. Strong zonal current of air, usually near the 500-mbar constant pressure surface in each hemisphere, that encircles the earth. Referred to as the jet stream because of its high concentration and great speed, often up to 500 km/h. Current of strongest wind (order 50 m/s) surmounting a region of strong tropospheric baroclinity and with pronounced decreases of wind toward its lateral flanks. Joule heating}Heating in the ionosphere below ~140 km height due to the interaction of ionospheric currents and the ambient electric field.katabatic windssWinds produced when gravity pulls cold, dense air from, fort example, the Antarctic plateau downslope to the coast.8L shellSurface of the geomagnetic field given by the longitudinal drift of an L line along which trapped charged particles bounce between northern and southern hemisphere. The L value is a length, in units of earth radius, which reduces to the equatorial radius /of a field line in the case of a dipole field.zLa NiaqConditions that are complementary to El Nio -- cold surface waters off Peru and intense trades over the Pacific.; laminar flow-Smooth, nonturbulent flow of a gas or liquid. lapse rateThe rapidity with which temperature decreases with altitude. The normal lapse rate is defined to be 3.6 F per 1000 ft, and the wet adiabatic lapse rate varies between 2 and 5 F per 1000 ft.~ latent heatqEnergy transferred from the earth's surface to the atmosphere through the evaporation and condensation processes.latent heat fluxEnergy associated with the exchange of water vapor between ocean and atmosphere; amount (or rate) of surface evaporation per unit area per unit time expressed in energy units.Le Chatlier's principlesWhen an external force is applied to an equilibrium system, the system adjusts to minimize the effect of the force.lidarLight detection and ranging, a family of laser-based remote-sensing techniques which involve sending a powerful laser beam into the atmosphere and collecting and analyzing the backscattered signal. lightningtElectrical discharge in thunderstorms caused by the separation of electric charge of positive and negative polarity.ilimbcThe edge of a celestial body as it appears to an observer; the edge of the sun's disk, for example.g lithosphereThe component of the Earth's surface comprising the rock, soil, and sediments. It is a relatively passive component of the climate system, and its physical characteristics are treated as fixed elements in the determination of climate. Semirigid upper platelike layer of the earth. Its thickness is near zero at oceanic ridge axes, but it increases with age to about 100 km. Oceanic lithosphere consists of a crustal layer ~5 km thick of basaltic composition underlain by mantle rocks. Continental lithosphere consists of a layer of crustal rock 30-60 km thick of low density and variable composition underlain by mantle rocks. Layer of greater strength than the underlying asthenosphere for deformationat geological rates. It includes the crust and part of the uppermost mantle and is of the order of 100 km in thickness beneath the continents. Earth's cool outer rigid layer, including the crust, separated from the earth's deeper layers by a relatively weak zone, the asthenosphere. The lithosphere is of negligibleZ thickness at some ocean ridges and may be as thick as 200 km or more beneath continents.]Little Ice AgeA cold period that lasted from about A.D. 1550 to about A.D. 1850 in Europe, North America, and Asia. This period was marked by rapid expansion of mountain glaciers, especially in the Alps, Norway, Ireland, and Alaska. There were three maxima, beginning aMbout 1650, about 1770, and 1850, each separated by slight warming intervals.jlong-range transportTTransport of pollutants within a moving air mass for a distance greater than 100 km./longwave radiationThe radiation emitted in the spectral wavelength greater than 4 microns corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as "terrestrial radiation" or "infrared radiation," although somewhat imprecisely. Compare shortwave radiation. magnetosphereEntire plasma envelope that surrounds the earth as constrained by the earth's dipole magnetic field and the interaction of this envelope with the solar wind, and with the interplanetary magnetic field.mammatus cloudsRounded, smooth, sack-like protrusions hanging from the underside of a cloud (usually a thunderstorm anvil). Mammatus clouds often accompany severe thunderstorms, but do not produce severe weather; they may accompany non-severe storms as well. Maunder minimumThe period from 1654 to 1714 when it was believed that there were no sunspots. It is now thought that there were some sunspots during that time but fewer than those counted after 1800.mean sea levelThe average height of the sea surface, based upon hourly observation of the tide height on the open coast or in adjacent water that have free access to the sea. In the United States, it is defined as the average height of the sea surface for all stages of the tide over a nineteen year period. Mean sea level, commonly abbreviated MSL and referred to simply as "sea level," serves as the reference surface for all altitudes in upper atmospheric studies.Mediterranean cllmateA climate characterized by dry summers and wet winters, often found along coasts lying about 40 from the equator. Much of California and much of the Mediterranean region of Europe have this kind of climate.BMilankovitch theoryAn astronomical theory formulated by the Yugoslav mathematician Milutin Milankovitch that associates climate change with fluctuations in the seasonal and geographic distribution of insolation determined by periodic variation of the Earth's eccentricity an-d obliquity and the longitude of perihelion.emist_Liquid particles 40 to 500 microns in diameter that are formed by condensation of vapor in air.mixed-phase regionZone in the atmosphere that contains water substance in all three of its phases (vapot, liquid, and solid) and whose temperature is gerneally between -40C and 0 C.MMEDMass Median Equivalent aerodynamic Diameter; where the equivalent aerodynamic diameter of a particle is the diameter of a sphere of density 1 g cm-3 that has the same falling velocity.modelingAn investigative technique that uses a mathematical or physical representation of a system or theory that accounts for all or some of its known properties. Models are often used to test the effects of changes of system components on the overall performance of the system.dmonsoonA name for seasonal winds, first applied to the winds over the Arabian Sea that blow for six months from the northeast and for six months from the southwest. The term has been extended to similar winds in other parts of the world (i.e., the prevailing west to northwest winds of summer in Europe have been called the "European monsoon"). The primary cause for these seasonal winds is the much greater annual variation of temperature over large land areas compared with neighboring ocean surfaces, causing an excess of pressure over the continents in winter and a deficit in summer, but other factors, such as topography of the land, also have an effect. The monsoons are strongest in the southern and eastern sides of Asia, but also occur along the coasts of tropical regions wherever the planetary circulation is not strong enough to inhibit them. Term originally coined by Arab mariners in reference to the seasonally shifting winds in the Indian Ocean. It has now come to denote climatic systems anywhere in which[ rainfall is markedly seasonal and in which the moisture comes mainly in the warm season. monsoonal circulationAtmospheric circulation induced by differential land-ocean heating. In summer, the flow is from the ocean to land; in winter it is from land to ocean, but with modification by the effects of the earth's rotation.qnegative feedback^An interaction that reduces or dampens the response of the system in which it is incorporated., net radiationAbsorbed minus emitted radiation. On a global average the earth's surface and atmosphere, respectively, absorb 170 W/m2 and 60 W/m2 solar radiation and emit 70 and 160 W/m2 as infrared radiation. Thus the net radiative gain of 100 W/m2 by the earth equals the loss by the atmosphere.NEXRADNext Generation Doppler Radar, the network of approximately 144 10-cm.-wavelength radars that form a component of the National Weather Service's radar storm identification network.normal modes of vibrationrNatural resonances on the coupled periodic displacements of atoms in a material about their equilibrium positions. nucleationThe beginning of the process of droplet or ice-crystal formation; homogenous nucleation occurs when there is no foreign particle to act as a nucleus. obliquityMeasures the tilt of the earth's axis of rotation with respect to the plane of the earth-sun orbit; provides the mid and high latitudes with seasons.occluded frontrA complex front that forms when a cold front overtakes a warm front and cuts off warm-sector air from the surface. ocean mixingProcesses that involve rates of advection, upwelling/downwelling, and eddy diffusion and that determine how rapidly excess atmospheric carbon dioxide can be taken up by the oceans.*ocean-atmosphere interactionsInteractions that are invoked to explain why certain phenomena, such as the Southern Oscillation, are attributable to changes in the ocean from a meteorological perspective and are attributable to changes in atmospheric conditions from an oceanographic pe rspective.opacityThe degree of obscuration of light; for example, a glass window has almost 0% opacity, whereas a concrete wall has 100% opacity. optical depthIn calculating the transfer of radiant energy, the mass of an absorbing or emitting material lying in a vertical column of unit cross-sectional area and extending between two specified levels. Also, the degree to which a cloud prevents light from passing through it; the optical thickness then depends on the physical constitution (crystals, drops, and/or droplets), the form, the concentration, and the vertical extent of the cloud.eorder of magnitudeQTen times; thus, an increase of two orders of magnitude is 10 x 10, or 100 times.} orographicqPertaining to mountain ranges; thus, a mountain or hill that causes air to rise over it is an orographic barrier.outgoing infrared radiationElectromagnetic radiation emitted by the earth's surface sue to heating by incoming solar radiation. Most of the outgoing infrared radiation is in the spectral region 4-80 microns. The earth's atmosphere is not transparent to this outgoing radiation as greenhouse gases absorb and reemit these wavelengths. The downward-directed component of the reemitted infrared radiation results in an additional heating of the earth's surface and raises the surface temperature from 235 K (-49 F), which is the "effectivye" temperature of the earth, to 288 K (59 F). This additional heating is called the greenhouse temperature enhancement.kozoneA molecule made up of three atoms of oxygen. In the stratosphere, it occurs naturally and it provides a protective layer shielding the Earth from ultraviolet radiation and subsequent harmful health effects on humans and the environment. In the troposphere, it is a chemical oxidant and major component of photochemical smog. Ozone has a characteristic, pungent odor familiar to most persons because ozone is formed when electrical apparatus produces sparks in air. Ozone is irritating to mucous membranes and toxic to human beings and lower animals. The U.S. Occupational Safety and Health Administration standards for industrial workers exposed to ozone on a daily basis limit ozone concentrations to 0.1 ppm on the average, with a maximum of 0.3 ppm for short exposures. Near the Earth's surface the concentration is usually 0.02-0.03 ppm in country air, and less in cities except when there is smog (when concentrations may reach 0.5 ppm or more for brief periods). Maximum concentration -- 5 x 10E12 per cm3, modre than 1000 times the normal peak level at the surface -- occurs at an altitude of 19 mi (30 km). ozone holexExtraordinary springtime ozone destruction. A phenomenon occurring primarily over Antarctica and first reported in 1985.i ozone layer\Layer in the stratosphere with high concentrations of ozone. Generally between 20 and 30 km.pack iceIce produced when the ocean freezes. This ice is broken into floes of various sizes and is compressed into pressure ridges by winds and ocean currents. Floes are separated from one another by open water leads and larger open water bodies called polynyas.'parhelic circleA halo around the sun.L parhelionAA bright spot on the 22 and 46 haloes, horizontal with the sun.|particulate matterhVery small pieces of solid or liquid matter, such as particles of soot, dust, aerosols, fumes, or mists. perihelionTime of the closest earth-sun approach (presently occurs in early January). Aphelion is the time of the farthest earth-sun approach (presently occurs in early July).MpHIInverse measure of the hydrogen ion concentration. pH of pure water is 7.yphotochemical smogeAir pollution caused by chemical reactions among various substances and pollutants in the atmosphere.^photodissociationKSplitting of a molecule into component parts due to absorption of a photon.] photoelectronNElectron ejected from an atom or molecule through the photoionization process.photoexcitationExcitation of an electron into an energy level above the ground state configuration by absorption of a photon by an atom or molecule.[photoionizationJRemoval of an electron from an atom or molecule by absorption of a photon.K photolysis?Breakdown of chemical compounds through the action of sunlight.photosynthesisThe manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll and sunlight as the energy source. Oxygen and water vapor are released in the process. Photosynthesis is dependent on favorable temperature and moisture conditions as well as on the atmospheric carbon dioxide concentration. Increased levels of carbon dioxide can increase net photosynthesis in many plants.j phytoplankton[That portion of the plankton community comprised of tiny plants (e.g., algae, and diatoms).WpileusOA cloud formed in saturated air above a convective tower and separated from it.planetary albedoThe fraction (approximately 30%) of incident solar radiation that is reflected by the earth-atmosphere system and returned to space, mostly by backscatter from clouds in the atmosphere.8planetary boundary layerThe transition region between the turbulent surface layer and the normally nonturbulent free atmosphere. This region is about 1 km in thickness and is characterized by a well-developed mixing generated by frictional drag as the air masses move over the Earth's surface. This layer contains approximately 10% of the mass of the atmosphere. Also called the atmospheric boundary layer or frictional layer; in air pollution literature, it is also called the mixing height -- pollutants released near the surface are quickly mixed up to the top of the PBL. Abbreviated PBL. The PBL height varies over a wide range (several tens of meters to several kilometers), particularly over land surfaces, and exhibits strong diurnal variations. The PBL height over land reaches its maximum value of the order of 1 km (range 0.2-5 km) in the late afternoon and its minimum value of the order of 100 m (range 20-500 m) before midnight. The lowest 10% of the PBL is called the surface layer (abbrev. SL), and is the portion most directly influenced by the surface.oplanetary waves^Atmospheric waves with wavelengths the order of the radius of the earth (~6000 km) and larger.fplankton\Passively floating or weakly motile aquatic plants (phytoplankton) and animals (zooplankton)Cplasma;Medium composed of free electrons, ions, and neutral atoms.6polar stratospheric cloudsClouds formed in the stratosphere of high latitudes during the winter months. Until 1986 the PSCs were thought to consist mainly of water ice, the individual particles growing by accretion of the H2O on nuclei of hydrated H2SO4. However, the measured opacities of the PSCs were smaller than one would expect on the hypothesis that the PSCs were composed mainly of H2O. This fact and the solid state thermodynamic properties of the PSCs led to the recent (1986) suggestion that HNO3 might be the dominant constituent of PSCs, with significant quantities of HCl (~10E-2 mole fraction). The presence of HNO3 and HCl in the solid phase are important in promoting the heterogeneous reactions. A consequence of this is the reduction of the gas phase concentrations of odd nitrogen, HCl and H2O.7polarized light&Light that vibrates only in one plane.hpositive feedbackUAn interaction that amplifies the response of the system in which it is incorporated.potential temperatureTemperature that an air parcel at a given height would have at the surface if it were displaced from that height to the surface by a adiabatic process. In a compressible fluid, the temperature that would by attained by a fluid parcel upon adiabatic expansion or compression (i.e., without the addition or removal of heat) from actual to a reference pressure (these reference pressures are 1000 hPa in the atmosphere and the surface in the ocean).= precessionMotion of the earth's axis of rotation about a perpendicular to the earth-sun orbital plane, in response to the earth rotation and the combined gravitational forces of the sun, moon, and planets. Affects the relationship of the winter and summer seasons t1o the earth-sun distance during an annual orbit.) precipitationAny or all forms of liquid or solid water particles that fall from the atmosphere and reach the Earth's surface. It includes drizzle, rain, snow, snow pellets, snow grains, ice crystals, ice pellets, and hail. The ratio of precipitation to evaporation is the most important factor in the distribution of vegetation zones. Precipitation is also defined as a measure of the quantity, expressed in centimeters or milliliters of liquid water depth, of the water substance that has fallen at a given location in a specified amount of time.pressure gradientThe rate of decrease in atmospheric pressure per unit of horizontal distance; used to indicate relative pressures on the earth's surface, and measured in the direction of most rapid decrease.profilerMultibeam fixed-antenna Doppler radar that points nearly vertically and measures the wind up to at least 15 km height. Operates from 900 to 50 MHz.epropagating modesRWavelike motions that transport energy away from the excitation or source region.K quantum yield