RawinsondeA radiosonde that is tracked to measure winds.
RecyclingThe process of converting materials that are no longer useful as designed or intended into a new product.
reflectionThe process whereby radiation (or other waves) incident upon a surface is directed back into the medium through which it traveled.
reflectivity (dBZ)(dBZ)A measure of the returned power, which is sensitive to the size and number of hydrometeors (i.e., the particle size spectra).
ReforestationPlanting of forests on lands that have previously contained forests but that have been converted to some other use.
RefractionThe change in direction of a ray of light when it passes through one media to another with differing optical densities.
relative datingthe process of determining the order in which certain events occurred or certain materials were formed.
Relative HumidityA measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature.
Renewable EnergyEnergy derived from resources that are regenerative or for all practical purposes can not be depleted.
Residence TimeThe average time spent in a reservoir by an individual atom or molecule. With respect to greenhouse gases, residence time usually refers to how long a…
Residual fuel oilHeavy fuel oil produced from the residue in the fractional distillation process rather than from the distilled fractions. No.
Residual Layerthe elevated portion of a convective boundary layer that remains after a stable boundary layer develops at the ground (usually in late afternoon or early…
resonanceThe state of a system in which an abnormally large vibration is produced in response to an external stimulus, occurring when the frequency of the stimulus…
RespirationThe process whereby living organisms convert organic matter to CO2, releasing energy and consuming O2.
RidgeA line or wall of broken ice forced up by pressure. May be fresh or weathered.
RimeRime A white or milky and opaque granular deposit of ice formed by the rapid freezing of super-cooled water drops as they impinge upon an exposed object.
Rossby WavesA series of troughs and ridges on quasi-horizontal surfaces in the major belt of upper tropospheric westerlies.
SaturationSaturation The condition in which the partial pressure of any fluid constituent (water in the atmospheric air) is equal to its maximum possible partial…
Saturation Vapor PressureThe vapor pressure of a system, at a given temperature, wherein the vapor of a substance is in equilibrium with a plane surface of that substance's pure…
SavannaA flat grassland of tropical and subtropical regions usually having distinct periods of dry and wet weather.
ScaleRatio of map distance to Earth distance. Thus, in a 1:24,000 scale map, one centimeter, inch, or foot equals 24,000 centimeters, inches, or feet on the…
ScatteringThe process in which a beam of light is diffused or deflected by collisions with particles suspended in the atmosphere.
Science BoardAn ACRF group made up of the ARM Science Team Executive Committee working group science chairs and climate research community appointees, that ensures…
Science Team Executive Committee (STEC)(STEC)The committee that provides recommendations, prioritization, coordination of activities, and program vision to the U.S.
Sea Level PressureThe sea level pressure is the atmospheric pressure at sea level at a given location.
Sea smokeSea smoke (arctic sea smoke) Evaporation fog or steam fog which is formed when water vapor is added to air which is much colder than the vapor's source…
Sea surface temperatureSea surface temperature Temperature of the water film at the sea surface.
Secondary oil recoveryInjection of water into an oil well after primary oil recovery to force out some of the remaining thicker crude oil.
SectorA sector is a segment of the economy that shares distinctive characteristics, such as telecommunications or energy.
SedimentAny finely divided organic and/or mineral matter deposited by air or water in nonturbulent areas.
Semipermanent anticycloneSemipermanent anticyclone (high) High pressure area largely predominate during a major portion of the year where an anticyclone appears on the mean…
Sensible HeatThe heat absorbed or released when a substance undergoes a change in temperature.
Sensible Heat FluxThe flux of heat from the earth's surface to the atmosphere that is not associated with phase changes of water; a component of the surface energy budget.
Septic tankUnderground tank for treatment of wastewater from a home in rural and suburban areas.
Severe ThunderstormA thunderstorm that produces a tornado, winds of at least 58 mph (50 knots), and/or hail at least ¾" in diameter.
Sewage treatment (primary)Mechanical treatment of sewage in which large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank.
Shale oilSlow-flowing, dark brown, heavy oil obtained when kerogen in oil shale is vaporized at high temperatures and then condensed.
SHIELDShield (screen) A screen to shield a rain-gauge from the influence of the wind, or to shield a thermometer against insolation.
Short Ton2000 pounds. A ton, as commonly used in the U.S. and Canada.
shortwave irradianceThe rate at which radiant energy, at wavelengths between 0.4 and 4 µm, is being transferred across an area of a surface (real or imaginary) in a…
shortwave net radiationThe difference between upwelling and downwelling broadband shortwave radiation.
shortwave radianceA measure of the intrinsic radiant energy flux intensity, at wavelengths between 0.
Shortwave RadiationIn solar-terrestrial terms, shortwave radiation is a term used to describe the radiant energy emitted by the sun in the visible and near-ultraviolet…
shortwave spectral irradianceThe rate at which radiant energy, at specrally-resolved wavelengths between 0.4 and 4 µm, is being emitted upwards and downwards into a radiation field…
Shortwave TroughAlso called Shortwave; A disturbance in the mid or upper part of the atmosphere which induces upward motion ahead of it.
Siberian HighSiberian High An area of high pressure which forms over Siberia in winter, and which is particularly apparent on mean charts of sea-level pressure.
single-column modeling (SCM)(SCM)An approach to the development and testing of cloud formation and parameterizations.
SinkAny process, activity, or mechanism which removes a greenhouse gas, an aerosol, or a precursor of a greenhouse gas or aerosol from the atmosphere.
sky brightness temperatureA descriptive measure of radiation in terms of the temperature of a hypothetical black body emitting an identical amount of radiation at the same…
SleetPrecipitation that consists of clear pellets of ice; sleet is formed when raindrops fall through a layer of cold air and freeze.
Sling PsychrometerAn instrument used to measure the water vapor content of the atmosphere in which wet and dry bulb thermometers are mounted on a frame connected to a…
SludgeThe mixture of organic and inorganic substances separated from sewage.
SmogA visible haze caused by particulate matter and ground-level ozone.
SnowPrecipitation that consists of frozen flakes formed when water vapor accumulates on ice crystals, going directly to the ice phase.
Snow blinkSnow blink (snow sky) A bright white glare on the underside of clouds, produced by the reflection of light from snow-covered surface.
Snow coverSnow cover 1) In general, a layer of snow on the ground surface. 2) The areal extent of snow-covered ground, usually expressed as per cent of total area…
SnowflakeAn agglomeration of snow crystals falling as a unit.
SoilSediments or other unconsolidated accumulations of solid particles produced by the physical and chemical disintegration of rocks, and which may or may not…
Soil CarbonA major component of the terrestrial biosphere pool in the carbon cycle. The amount of carbon in the soil is a function of the historical vegetative cover…
soil temperatureThe temperature measured near the surface of the soil.
Solar energyElectromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy…
Solar RadiationA general term for the visible and near visible (ultraviolet and near-infrared) electromagnetic radiation that is emitted by the sun.
solar variabilitychanges in the amount of radiation emitted by the sun due to the sun's internal dynamics.
SolsticeThe two times of the year when the sun is apparently farthest north and south of the earth's equator; usually occurring on or around June 21 (summer…
soundingA set of data measuring the vertical structure of an atmospheric parameter (temperature, humidity, pressure, winds, etc.) at a given time.
SourceAny place or object from which air pollutants are released. Sources that are fixed in space are stationary sources and sources that move are mobile…
Southern Great Plains (SGP) site(SGP)The first of the ARM research sites, the SGP site is located in south Kansas and north Oklahoma.
Special naphthaAll finished products within the naphtha boiling range that are used as paint thinners, cleaners, or solvents.
Specific HeatThe amount of heat required to raise a unit mass of a substance through one degree, expressed as a ratio of the amount of heat required to raise an equal…
Specific HumidityThe weight of water vapor, per unit weight of dry air.
spectral widthA measure of the spread of the Doppler spectrum and consequently is sensitive to the spread in the particle size spectra.
speleothema mineral deposit formed in caves. Two types of speleothems are stalagmites and stalactites.
Squall LineA line of active thunderstorms, either continuous or with breaks, including contiguous precipitation areas resulting from the existence of the…
stabilityTendency of systems, especially ecosystems, to persist, relatively unchanged, through time; also, persistence of a component of a system.
Stable air massStable air mass Air mass having static stability in its lower layers; it is free from convection, has a low degree of turbulence and may have stratiform…
stable isotopedifferent species of an element that have the same atomic number, but different atomic mass, that are not affected by radioactive decay.
stable statea steady condition in which the recently observed behavior is expected to continue unchanged in the future.
Standard AtmosphereA hypothetical vertical distribution of atmospheric temperature, pressure, and density that, by international agreement, is taken to be representative of…
Station PressureThe absolute air pressure at a given reporting station. The air pressure is directly proportional to the combined weight of all air in the atmosphere…
stationary pressureA front between warm and cold air masses that is moving very slowly or not at all.
Steering flowSteering flow A basic fluid flow which exerts a strong influence upon the direction of movement of disturbances embedded in it.
Still gasAny form or mixture of gases produced in refineries by distillation, cracking, reforming, and other processes.
StratiformHaving extensive horizontal development, as opposed to the more vertical development characteristic of convection.
StratocumulusLow-level clouds, existing in a relatively flat layer but having individual elements. Elements often are arranged in rows, bands, or waves.
StratopauseThe boundary between the stratosphere and mesosphere.
StratosphereThe region of the atmosphere extending from the top of the troposphere to the base of the mesosphere, an important area for monitoring stratospheric ozone.
Stratospheric OzoneIn the stratosphere, ozone has beneficial properties where it forms an ozone shield that prevents dangerous radiation from reaching the Earth's surface.
StratusA low, generally gray cloud layer with a fairly uniform base. Stratus may appear in the form of ragged patches, but otherwise does not exhibit individual…
StreamflowDischarge that occurs in a natural channel.
Strip miningCutting deep trenches to remove minerals such as coal and phosphate found near the earth's surface in flat or rolling terrain. See surface mining.
Subbituminous coalA dull, black coal of rank intermediate between lignite and bituminous coal. See coal.