Meteorology and atmospheric science terminology · MLC-0110

Meteorology and atmospheric science terms: R (568)

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• RRain
• RARain
• RabalA method of upper-air observation that involves tracking a free-rising balloon by radar to determine wind...
• RADAP IIRAdar DAta Processor II, attached to some WSR-57 and WSR-74 radar units. It automatically controls the tilt...
• RadarA system that uses radio waves to detect the presence, distance, speed, and direction of objects such as...
• Radar algorithmA computational procedure or set of rules applied to raw radar data to extract specific meteorological...
• Radar altimeterAn electronic instrument that measures the altitude of an aircraft or spacecraft above the terrain by...
• Radar altitudeThe height of an aircraft or satellite above the terrain directly beneath it, as measured by a radio...
• Radar bandA specific range of frequencies within the electromagnetic spectrum allocated for use by radar systems. The...
• Radar beamA focused emission of electromagnetic energy transmitted by a radar antenna, designed to detect targets and...
• Radar calibrationThe process of adjusting a radar system to provide accurate and reliable measurements of atmospheric...
• Radar climatologyThe study of long-term patterns and statistics of meteorological phenomena using data collected by radar...
• Radar coded messageA standardized format for transmitting meteorological radar observations, providing concise information about...
• Radar constantA fixed value used in the radar equation that accounts for the physical characteristics of a specific radar...
• Radar cross sectionA measure of an object's ability to reflect radar signals back to the radar receiver. It quantifies the...
• Radar data acquisitionAn acronym for Radar Data Acquisition. The RDA is the hardware component of the NEXRAD system that consists...
• Radar displaysVisual representations of data collected by radar systems, showing atmospheric phenomena such as...
• Radar ductA layer of the atmosphere in which the vertical gradient of radio refractivity is steeper than about minus...
• Radar equationA mathematical relationship that quantifies the power received by a radar antenna from a target, based on the...
• Radar frequency bandA specific range of electromagnetic frequencies allocated for radar operations, each band having distinct...
• Radar hydrologyThe application of weather radar data to hydrological problems, primarily for estimating and forecasting...
• Radar interferometryA technique that uses two or more radar antennas, or repeated observations from a single antenna, to measure...
• Radar meteorological observationThe process of collecting data on atmospheric conditions and phenomena using radar systems. These...
• Radar meteorologyA specialized branch of meteorology that uses radar technology to study and forecast weather phenomena. It...
• Radar mileA unit of time equal to the interval a radar pulse takes to travel one nautical mile to a target and return...
• Radar mosaicA radar product that combines information from multiple radars to give a regional or national view of...
• Radar observationThe acquisition of data about atmospheric conditions and targets using radar systems. This process involves...
• Radar polarimetryA radar technique that transmits and receives electromagnetic waves with different polarizations to gain more...
• Radar Product GeneratorThe RPG is the computer in the NEXRAD system that receives polar-coordinate base radar data from the RDA and...
• Radar rangeDistance from the radar antenna. The WSR-88D radar has a range for velocity products out to 124 nautical...
• Radar reflectivityA measure of the amount of radar energy scattered back to the radar antenna by atmospheric targets, primarily...
• Radar reflectivity factorA quantitative measure of the radar signal returned from a volume of hydrometeors, representing the sum of...
• Radar reflectivity factor (Z), see Radar reflectivity factor
• Radar reportA summary of meteorological information derived from radar observations, typically issued by weather...
• Radar resolutionThe ability of a radar system to distinguish between two closely spaced targets in terms of range, azimuth...
• Radar returnThe portion of a transmitted radar pulse that is reflected or scattered back to the radar antenna by a...
• Radar scatterometerA type of radar system specifically designed to measure the backscattered power from a surface, which is then...
• Radar soundingThe use of radar to probe the vertical structure of the atmosphere, providing profiles of atmospheric...
• Radar storm detectionThe process of identifying and tracking atmospheric disturbances, such as thunderstorms and precipitation...
• Radar theodoliteA specialized radar system designed to track the position of a radiosonde or other meteorological target as...
• Radar weather observationThe process of using radar to detect and analyze atmospheric phenomena, primarily precipitation, within a...
• Radar wind soundingA method for determining upper-air wind speed and direction by tracking a radar target carried aloft by a...
• Radar wind systemThe complete ground-based equipment used to perform a radar wind sounding. It consists of a tracking radar to...
• RadarscopeA cathode-ray tube (CRT) or modern digital display that presents weather radar data in a visual format. The...
• Radial inflowThe movement of air or fluid towards the center of a rotating system, such as a thunderstorm or a tropical...
• Radial symmetryA characteristic of an object or system where its properties are uniform in all directions from a central...
• Radial velocityThe component of an object's velocity that is directed toward or away from a measurement point, such as a...
• Radial windThe component of wind velocity directed either toward or away from a central point or a radar antenna. It...
• RadianThe standard unit of angular measure, based on the radius of a circle. One radian is the angle created at the...
• RadianceThe measure of radiant flux passing through or emerging from a specific area within a given solid angle. It...
• RadiantThe apparent point or area in the sky from which meteor trails appear to originate during a meteor shower...
• Radiant densityThe amount of radiant energy contained within a given volume of space at a specific instant. It is a measure...
• Radiant energyEnergy that propagates through space or a material medium in the form of electromagnetic waves, such as...
• Radiant exitanceThe total radiant flux emitted from a surface per unit area. This quantity describes the power radiated by a...
• Radiant exposureThe total radiant energy incident on a surface per unit area over a specified period, representing the...
• Radiant fluxThe total amount of radiant energy emitted, transmitted, or received per unit time. It quantifies the rate of...
• Radiant flux densityThe radiant flux incident upon, emitted from, or passing through a surface per unit area. It describes the...
• Radiant intensityThe radiant flux emitted by a source per unit solid angle, describing the power of radiation directed into a...
• Radiant-energy thermometerAn instrument that measures temperature by detecting the intensity of infrared radiation emitted by an...
• RadiationThe flow of energy through space or a medium in the form of electromagnetic waves or moving particles. In...
• Radiation beltsRegions of energetic charged particles, primarily protons and electrons, trapped by the Earth's magnetic...
• Radiation chartA graphical tool, or nomogram, used for calculating the transfer of infrared radiation through the...
• Radiation fogFog that forms when the ground cools rapidly by radiation on clear, calm nights, causing the air immediately...
• Radiation frostFrost that forms on surfaces when the air temperature near the ground falls below freezing due to radiative...
• Radiation inversionAn atmospheric temperature inversion that forms near the ground on clear, calm nights due to rapid radiative...
• Radiation lawsA set of physical principles that describe the behavior of electromagnetic radiation, particularly its...
• Radiation modelA computational representation of how electromagnetic radiation interacts with the atmosphere and Earth's...
• Radiation patternThe directional distribution of electromagnetic energy radiated from or received by a source, such as a radar...
• Radiation pressureThe force exerted per unit area on any surface exposed to electromagnetic radiation, resulting from the...
• Radiation shieldA device designed to protect a temperature sensor from direct solar radiation and terrestrial radiation...
• Radiation torqueA rotational force exerted on an object by electromagnetic radiation, resulting from the transfer of angular...
• Radiational coolingThe process by which the Earth's surface and the atmosphere lose heat to space through the emission of...
• Radiational inversionUsed interchangably with Nocturnal Inversion; a temperature inversion that develops during the night as a...
• Radiational tideA periodic variation in atmospheric pressure and wind caused by the daily cycle of solar heating and cooling...
• Radiative coolingThe process by which a surface or atmospheric layer loses heat by emitting longwave infrared radiation into...
• Radiative equilibriumA state in which the rate of absorption of radiant energy by a system is equal to its rate of emission of...
• Radiative flux densityThe rate at which radiant energy passes through a unit area perpendicular to the direction of propagation. It...
• Radiative flux divergenceThe net change in radiative flux within a given volume of the atmosphere, indicating whether that volume is...
• Radiative forcingThe change in the net downward radiative flux at the tropopause due to an external perturbation in the...
• Radiative heatingThe process by which a surface or atmospheric layer gains heat by absorbing electromagnetic radiation...
• Radiative transferThe physical process by which electromagnetic radiation propagates through a medium, involving absorption...
• Radiative-convective equilibriumA theoretical state of the atmosphere where the net radiative heating or cooling at each level is balanced by...
• Radiative-convective modelA simplified atmospheric model that calculates the vertical temperature profile of the atmosphere by...
• Radiatively active gasAn atmospheric gas that absorbs and emits radiation at specific wavelengths within the spectrum of thermal...
• RadiatorA body or surface that emits electromagnetic radiation, particularly in the infrared range, as a consequence...
• RadiatusA cloud variety in which the elements form parallel bands or streaks that, because of perspective, appear to...
• Radio acoustic sounding systemAn instrument system that measures atmospheric temperature profiles by simultaneously transmitting acoustic...
• Radio atmometerAn atmometer used to compare the intensity of radiant energy, devised by Livingston, in which a black porous...
• Radio beaconA stationary radio transmitter that emits a continuous or modulated radio signal for navigational purposes or...
• Radio blackoutA severe disruption or complete loss of high-frequency radio communication, primarily caused by intense solar...
• Radio climatologyThe study of the statistical variations of atmospheric properties that affect the propagation of radio waves...
• Radio direction finderAn instrument used to determine the direction from which a radio signal is originating, by measuring the...
• Radio direction findingA technique for determining the direction to a radio-frequency source by measuring the angle of arrival of...
• Radio ductA layer in the atmosphere where the vertical gradient of the radio refractive index is such that radio waves...
• Radio emissionEmissions of the sun in radio wavelengths from centimeters to dekameters, under both quiet and disturbed...
• Radio eventFlares with Centimetric Bursts and/or definite Ionospheric Event (SID)
• Radio frequencyThe portion of the electromagnetic spectrum with wavelengths from about 1 millimeter to 100 kilometers...
• Radio frequency bandA specific range of radio frequencies allocated for particular communication or sensing purposes, as defined...
• Radio holeA region in the atmosphere where radio wave propagation is significantly attenuated or blocked, resulting in...
• Radio horizonThe locus of points at which direct rays from a transmitter just graze the Earth's surface. Atmospheric...
• Radio meteorologyThe study of how radio waves propagate through the Earth's atmosphere and how atmospheric phenomena affect...
• Radio navigation aidA ground-based or airborne electronic system that transmits radio signals to assist aircraft or ships in...
• Radio soundingA method of remotely sensing atmospheric properties, such as temperature, humidity, and wind, by analyzing...
• Radio sourceAn object or phenomenon that emits electromagnetic radiation in the radio frequency portion of the spectrum...
• Radio waveA type of electromagnetic radiation with wavelengths longer than infrared light, typically ranging from about...
• Radio waves, see Radio wave
• Radio wind observationA method for determining wind speed and direction at different altitudes by tracking the movement of a...
• Radioactive carbonAn unstable isotope of carbon, primarily carbon-14, which undergoes radioactive decay. This isotope is...
• Radioactive datingA geochronological method used to determine the absolute age of rocks, fossils, and other materials by...
• Radioactive decayThe spontaneous process by which an unstable atomic nucleus transforms into a more stable nucleus by emitting...
• Radioactive falloutThe deposition of radioactive particles from the atmosphere onto the Earth's surface, resulting from nuclear...
• Radioactive gasA gaseous substance containing unstable isotopes that undergo radioactive decay, emitting radiation...
• Radioactive precipitationRain, snow, or other forms of precipitation that contain radioactive materials. This occurs when radioactive...
• Radioactive snow gaugeAn instrument that measures the water equivalent of a snowpack from the attenuation of gamma radiation...
• Radioactive-particle ionizationThe process by which electrically neutral atoms or molecules in the atmosphere gain or lose electrons due to...
• RadioactivityThe spontaneous emission of radiation from the nucleus of an unstable atom, resulting in its transformation...
• RadiofacsimileAlso known as HF FAX, radiofax or weatherfax, is a means of broadcasting graphic weather maps and other...
• RadiofaxAbbreviation for radiofacsimile
• Radioisotope snow gageA snow water equivalent gage based on the absorption of gamma radiation by snow; this gage can measure up to...
• RadiomaximographAn instrument that measures and records the maximum field strength of atmospherics (sferics) over a given...
• RadiometerAn instrument designed to measure the intensity of electromagnetic radiation, typically across a specific...
• RadiometryThe science and technology of measuring electromagnetic radiation, including its intensity, distribution, and...
• RadiosondeA balloon-borne instrument package that measures and transmits atmospheric parameters such as pressure...
• Radiosonde balloonA large, unmanned, high-altitude balloon used to carry a radiosonde instrument package into the upper...
• Radiosonde ground equipmentThe collection of instruments and systems located on the Earth's surface that receive, process, and record...
• Radiosonde observationThe process of launching a radiosonde and collecting the atmospheric data it transmits during its ascent...
• Radiosonde recorderA component of the radiosonde ground equipment responsible for receiving and storing the radio signals...
• Radiosonde stationA ground-based facility responsible for launching radiosondes and receiving the atmospheric data they...
• Radiosonde systemThe integrated collection of components used for upper-air atmospheric sounding, comprising the radiosonde...
• Radiosonde transmitterA small radio device integrated within the radiosonde instrument package that broadcasts the measured...
• Radius of maximum windsThe distance from the center of a tropical cyclone to the location of the cyclone's maximum winds. In...
• Radius of protectionThe horizontal distance from a lightning rod or other lightning protection system within which objects are...
• RADOBA coded report containing weather radar observations, an abbreviation for Radar Observation. The message...
• RadomeA protective, weatherproof enclosure for a radar antenna that is transparent to radio waves. It shields the...
• RadonA naturally occurring, colorless, odorless, and radioactive noble gas that is a product of the radioactive...
• RAFCRegional Area Forecast Center
• RafficheGusts that blow down from the mountains around the Mediterranean, including the violent gusts of the bora...
• RAFOS technologyA float tracking system for ocean currents in which neutrally buoyant floats drift at a chosen depth and...
• RAFSRegional Analysis and Forecasting System
• Rafted iceA form of sea ice deformation where one floe overrides another, creating a double layer of ice. This process...
• Ragged ceilingA cloud ceiling that is irregular and poorly defined, often characterized by fragmented or broken cloud bases...
• RaggiaturaA violent land squall that rushes down ravines and valleys from the high ground of Italy and reaches only a...
• RainA form of liquid precipitation consisting of water droplets that form from atmospheric water vapor and fall...
• Rain and snow mixedA type of precipitation consisting of both liquid rain droplets and solid snowflakes falling simultaneously...
• Rain attenuationThe reduction in the strength of an electromagnetic signal, particularly at microwave and millimeter-wave...
• Rain cloudA cloud from which precipitation in the form of rain is falling or is expected to fall. These clouds are...
• Rain crustA layer of ice formed on a snowpack surface when rain falls onto snow and subsequently freezes. This process...
• Rain dayA calendar day on which a measurable amount of precipitation, specifically rain, is recorded at a given...
• Rain factorThe ratio of mean annual precipitation in millimeters to mean annual temperature in degrees Celsius...
• Rain footSlang for a horizontal bulging near the surface in a precipitation shaft, forming a foot-shaped prominence...
• Rain forestA dense, evergreen forest ecosystem characterized by high annual rainfall and warm temperatures throughout...
• Rain forest climateA type of tropical climate characterized by consistently high temperatures, high humidity, and abundant...
• Rain gaugeAn instrument used to measure the amount of liquid precipitation over a specific period. It consists of a...
• Rain induced fogWhen warm rain falls through cooler air, water evaporates from the warm rain. It subsequently condenses in...
• Rain makingThe artificial inducement or increase of precipitation through cloud seeding or other atmospheric...
• Rain shadowA dry area on the leeward side of a mountain range, shielded from prevailing winds and moisture-laden air. As...
• Rain shieldIn a hurricane, a solid or nearly solid area of rain that typically becomes heavier as one approaches the...
• Rain showerA brief period of precipitation characterized by its sudden onset and cessation, and often by rapid changes...
• Rain simulatorA device designed to produce artificial rainfall under controlled conditions for experimental purposes. It...
• Rain stageThe stage of an idealized pseudoadiabatic ascent of moist air in which water vapor condenses at temperatures...
• Rain stimulation by artificial meansThe deliberate attempt to enhance or initiate precipitation from clouds through human intervention. This...
• Rain washoutThe process by which precipitation, particularly rain, removes aerosols, gases, and particulate matter from...
• RainbandAn elongated, narrow area of precipitation, either rain or snow, that is significantly longer than it is...
• RainbowAn optical and meteorological phenomenon that appears as a multicolored arc in the sky. It is caused by the...
• RaindropA discrete particle of liquid water that falls from the atmosphere, formed through the condensation and...
• Raindrop size distributionThe statistical representation of the number of raindrops within specific size ranges in a given volume of...
• Raindrop spectrographAn instrument designed to measure the size and velocity of individual raindrops as they fall through a...
• RainfallThe amount of liquid precipitation that falls on a given area over a specific period. It is typically...
• Rainfall distributionThe spatial and temporal pattern of precipitation across a geographical area over a specified period. This...
• Rainfall durationThe total length of time during which precipitation occurs at a specific location or within a defined area...
• Rainfall estimatesA series of NEXRAD products that employ a Z-R relationship to produce accumulations of surface rainfall from...
• Rainfall excessThe portion of total rainfall that does not infiltrate the ground, evaporate, or fill surface depressions...
• Rainfall frequencyA statistical measure of how often a rainfall event of a specific magnitude and duration is expected to occur...
• Rainfall intensity patternThe spatial and temporal variation of the rate at which rain falls over a specific geographic area. This...
• Rainfall intensity return periodThe average interval, in years, between occurrences of a rainfall event with an intensity equal to or greater...
• Rainfall lossThe portion of total precipitation that does not contribute to surface runoff or groundwater recharge...
• Rainfall rateThe amount of precipitation falling per unit of time, typically expressed in millimeters per hour or inches...
• Rainfall regimeThe characteristic pattern of rainfall over a geographical area, including its seasonal distribution, average...
• Rainfall stationA designated location equipped with instruments for measuring precipitation, primarily rainfall. These...
• Rain-free BaseA dark, horizontal cloud base with no visible precipitation beneath it. It typically marks the location of...
• Rain-gauge shieldA device placed around a rain gauge to minimize errors in precipitation measurement caused by wind. It alters...
• Rain-intensity gaugeAn instrument designed to measure the rate at which precipitation falls over a given time period. Unlike a...
• Rain-outThe process by which atmospheric aerosols and gases are incorporated into cloud droplets or ice crystals...
• RainstormA period of heavy or prolonged rainfall, often accompanied by strong winds, thunder, and lightning. These...
• Rainy climateA climate classification characterized by abundant precipitation throughout the year, sufficient to support...
• Rainy seasonA period of the year when a region receives the majority of its annual precipitation. This season is often...
• Ramp structureA sawtooth pattern seen in time series of temperature or other scalars in turbulent flow near the surface, in...
• RamsondeA snow penetrometer, also spelled rammsonde, made of a graduated rod with a cone at the tip that is driven...
• RandomDescribing an event or process where the outcome is not predictable with certainty, and each possible outcome...
• Random errorAn unpredictable deviation in a measurement that varies from one observation to the next, arising from...
• Random forecastA forecast that predicts future atmospheric conditions based on purely random chance, without any scientific...
• Random numbersA sequence of numbers in which each number is statistically independent of the others and each has an equal...
• Random processA collection of random variables indexed by time or space, representing a phenomenon whose future state...
• Random sampleA subset of data points or observations selected from a larger atmospheric dataset in such a way that every...
• Random seaA complex ocean surface condition characterized by waves of varying heights, periods, and directions...
• Random variableA variable whose possible values are numerical outcomes of a random phenomenon. In atmospheric science, this...
• Random walk modelA mathematical model describing a path consisting of a sequence of random steps. In atmospheric science, it...
• RandomizationThe process of introducing randomness into an experiment or data collection to minimize bias and allow for...
• Randomized seeding trialAn experimental method designed to statistically assess the effectiveness of cloud seeding for precipitation...
• RandomnessThe quality or state of lacking any predictable pattern or order. In atmospheric science, randomness is...
• RangeThe difference between the maximum and minimum values observed in a set of data, indicating the spread or...
• Range aliasingAn ambiguity in radar measurements where echoes from distant targets are incorrectly interpreted as...
• Range attenuationThe reduction in the power of a radar signal as it propagates through the atmosphere, primarily due to the...
• Range errorAn inaccuracy in the measurement of distance to an object, often encountered in radar or lidar systems. In...
• Range foldingThis occurs when the radar receives a signal return from a pulse other than the most recent pulse. In this...
• Range gateA specific time interval used in radar systems to isolate and process echoes from a particular distance from...
• Range markerA visual indicator, typically a concentric circle or a numerical label, displayed on a radar screen to denote...
• Range normalizationThe process of adjusting radar reflectivity data to account for the decrease in signal strength with...
• Range resolutionThe ability of a radar system to distinguish between two targets located at slightly different distances...
• Range unfoldingProcess of removing range ambiguity in apparent range of a multitrip target on the radar.
• Range-height indicatorA type of weather radar display, abbreviated as RHI, that shows a vertical cross-section of the atmosphere...
• Rankine temperature scaleAn absolute thermodynamic temperature scale that uses degrees Fahrenheit for its unit increments, with its...
• Rankine vortexA theoretical model of a vortex that combines a solid-body rotation in its core with a potential vortex in...
• RAOBRadiosonde Observation (Upper-Air Observation)
• Raoult's lawA principle describing the partial vapor pressure of a solvent above a solution, which is directly...
• Rapid deepeningA decrease in the minimum sea-level pressure of a tropical cyclone of 1.75 mb/hr or 42 mb for 24 hours
• Rapid distortion theoryA theoretical framework used to analyze the evolution of turbulence under the influence of rapid mean flow...
• Rapid interval imagingThe acquisition of geostationary satellite images at intervals much shorter than the routine schedule, from a...
• Rapid interval scanA mode of operation for meteorological satellites or radar systems where data is collected over a specific...
• Rapid Onset FloodingIn the context of the National Water Model (NWM), rapid onset flooding refers to stream reaches that are...
• Rapidly intensifyingAny maritime cyclone whose central pressure is dropping, or is expected to drop, at a rate of 1 MB per hour...
• RAREPA coded message containing a summary of radar observations, typically issued hourly by weather radar...
• Rate coefficientA proportionality constant that quantifies the speed of a chemical reaction in the atmosphere. It relates the...
• Rate constantsThe proportionality factors in rate laws that connect the rate of a chemical reaction to the concentrations...
• Rate of accretionThe speed at which a larger hydrometeor, such as a hailstone or graupel particle, grows by collecting smaller...
• Rate-of-climb indicatorAn aircraft instrument that displays the vertical speed of the aircraft, indicating whether it is ascending...
• Rating curveA graphical relationship between the stage (water level) of a river or stream and its corresponding discharge...
• Rating flumeA specially constructed channel section designed to measure the flow rate of water in open channels. It...
• Rational methodA simplified hydrological model used to estimate peak runoff rates from small urban or agricultural...
• RawA colloquial description of weather that feels uncomfortably cold, usually because the air is both cold and...
• Raw momentA statistical measure that describes the shape and characteristics of a probability distribution without...
• Raw waterUntreated water found in natural sources such as rivers, lakes, groundwater, or precipitation, before any...
• RawinA method of upper-air observation that determines wind speed and direction by tracking a free-rising balloon...
• Rawin targetA device attached to a free-rising balloon that allows its position to be tracked by ground-based radar or...
• RawinsondeA radiosonde that is tracked by ground-based radar or radio direction-finding equipment to determine...
• Rawinsonde observationA meteorological measurement obtained by launching a radiosonde (a balloon-borne instrument package) that...
• RAWSRemote Automated Weather Stations
• RayA conceptual line representing the path along which electromagnetic radiation, such as light or radio waves...
• Ray tracingA computational technique used to model the path of light or sound rays through a medium, accounting for...
• Rayleigh atmosphereA theoretical model of the Earth's atmosphere composed solely of molecules that scatter radiation according...
• Rayleigh numberA dimensionless number that quantifies the ratio of buoyancy forces to viscous and thermal diffusive forces...
• Rayleigh optical depthA measure of the optical thickness of an atmosphere due to Rayleigh scattering by air molecules. It...
• Rayleigh phase functionA mathematical function that describes the angular distribution of scattered radiation for Rayleigh...
• Rayleigh scatteringThe elastic scattering of electromagnetic radiation by particles that are significantly smaller than the...
• Rayleigh waveA type of surface acoustic wave that propagates along the free surface of an elastic solid, such as the...
• Rayleigh-Bénard convectionA type of natural convection that occurs in a fluid layer heated from below and cooled from above, leading to...
• Rayleigh's formulaAn equation that describes the intensity of light scattered by particles much smaller than the wavelength of...
• Rayleigh's scattering lawA physical principle stating that the intensity of light scattered by particles is inversely related to the...
• RCKYRocky Mountains
• RCMDRecommend
• RCVReceive
• RDGridge
• RDSRadius
• ReachA specific section or segment of a river, stream, or other body of water, often characterized by relatively...
• Reaction kineticsThe study of the rates of chemical reactions that occur in the atmosphere and the factors that influence...
• Reaction orderThe exponent to which the concentration of a reactant is raised in the rate law for a chemical reaction...
• Reaction rateThe speed at which a chemical reaction proceeds, typically expressed as the change in concentration of a...
• Real timeDescribing data or information that is available almost instantaneously after its collection, allowing for...
• Real-time processingThe immediate analysis and interpretation of meteorological data as it is received, without substantial...
• Real-time transmissionThe process of sending meteorological data from a sensor or observation platform to a processing center with...
• ReanalysisA systematic reprocessing of past observations with a single fixed, modern forecast model and data...
• Rear flank downdraftA region of dry air subsiding on the back side of, and wrapping around, a mesocyclone. It often is visible as...
• Rear of a depressionThe portion of an extratropical cyclone, or low-pressure system, located to the west of its center in the...
• Rear-inflow jetA stream of relatively dry, cold air that descends from the mid-levels of the atmosphere into the rear flank...
• Reaumur temperature scaleA temperature scale where the freezing point of water is set at 0 degrees and the boiling point is at 80...
• ReboyoA storm from the southwest that persists for about a day during the rainy season along the coast of Brazil...
• Received powerThe amount of electromagnetic energy detected by a receiver, such as a radar antenna or radiometer, after it...
• ReceiverAn electronic device designed to detect, amplify, and process electromagnetic signals. In meteorology...
• Receiver gainA measure of the amplification applied to a signal received by an instrument, such as a weather radar or...
• Receiver (noise) temperatureA measure of the noise power generated by a receiver, expressed as an equivalent temperature in Kelvin. This...
• RecessionThe period of decreasing discharge in a stream or river following a peak flow event, as water drains from the...
• Recession curveA graphical representation showing the decrease in streamflow over time after a precipitation event has ended...
• RechargeThe process by which water infiltrates the ground and moves downward to replenish groundwater aquifers. This...
• Recharge areaA region of the land surface where precipitation and surface water infiltrate the ground and percolate...
• Recharge capacityThe maximum rate at which a land area can absorb precipitation and replenish underlying groundwater aquifers...
• RecirculationThe process where air or water that has been previously discharged or processed is drawn back into a system...
• RecombinationThe process in the atmosphere where positive ions and negative electrons or ions neutralize each other to...
• Recombination coefficientThe rate constant in the loss law for charged particles, where the rate at which electron density is lost...
• Recombination energyThe energy released when a positive ion and a free electron combine to form a neutral atom or molecule. This...
• ReconnaissanceThe systematic exploration or observation of an area to gather information, particularly regarding...
• Reconnaissance codeAn aircraft weather reconnaissance code that has come to refer primarily to in-flight tropical weather...
• Record event reportThis non-routine narrative product is issued by the National Weather Service to report meteorological and...
• Record observationThe most complete type of aviation weather observation, taken at regular, equal intervals, usually hourly on...
• Recording albedometerAn instrument designed to continuously measure and record the albedo of a surface, which is the ratio of...
• Recording instrumentA device that automatically registers and stores measurements of atmospheric variables over a period of time...
• Recording potentiometerAn electrical instrument that continuously measures and records an unknown electromotive force or potential...
• Recording rain gaugeAn instrument that continuously measures and records the amount and intensity of precipitation over time...
• Recovery testA hydrological test conducted on a well or aquifer system to observe the rate at which the water level...
• Recovery timeThe time a fired transmit-receive tube in a radar needs to deionize after the transmitter pulse, until it...
• Recreation reportThis National Weather Service product is used to relay reports on conditions for resorts and recreational...
• RecurrenceUsed especially in reference to the recurrence of physical parameters every 27 days (the rotation period of...
• Recurrence formulaA mathematical expression that defines a sequence where each term is determined by one or more preceding...
• RecurvatureThe process by which a tropical cyclone, which initially moves westward, changes its track to a...
• Recurving tropical cycloneA tropical cyclone that has transitioned from a westward track in the tropics to a poleward and then eastward...
• Recycled waterWater that has been treated and purified after its initial use, making it suitable for beneficial purposes...
• Red flagThis a fire weather program which highlights the onset of critical weather conditions conducive to extensive...
• Red flag warningA term used by fire-weather forecasters to call attention to limited weather conditions of particular...
• Red flashA rare, brief flash of red light seen at the lower edge of the rising or setting Sun, where refraction leaves...
• Red noiseA type of noise or random process where the power spectral density decreases with increasing frequency...
• Red Sea WaterA warm, highly saline water mass formed in the Red Sea by strong evaporation and little freshwater input. It...
• Red snowSnow that appears reddish or pink due to the presence of pigmented microorganisms, primarily a species of...
• Red tideA common name for harmful algal blooms, which are discolorations of surface waters caused by a rapid increase...
• Red watch or red boxSlang for Tornado Watch.
• Reduced gravityAn approximation used in fluid dynamics for stratified fluids, where the full gravitational acceleration is...
• Reduced gridA computational grid for global numerical models where the number of grid points along lines of latitude...
• Reduced pressureThe atmospheric pressure at a given station, adjusted to a standard reference level, typically mean sea...
• ReductionThe process of adjusting meteorological observations to a common reference point or standard condition for...
• Reduction of pressure to a standard levelThe mathematical adjustment of observed atmospheric pressure readings from a station's actual elevation to a...
• Reduction of temperature to mean sea levelThe process of adjusting observed air temperatures from a station's elevation to an equivalent temperature at...
• Reech numberA dimensionless number equal to gravitational acceleration times a characteristic length, divided by the...
• REFReference
• Reference crop evaporationThe rate of evapotranspiration from a hypothetical reference crop, such as short green grass or alfalfa...
• Reference markA relatively permanent point of known elevation which is tied to a benchmark.
• ReflectanceThe ratio of the radiant flux reflected by a surface to the radiant flux incident upon it. This dimensionless...
• ReflectionThe phenomenon where a wave, such as light or sound, encounters a boundary between two different media and...
• Reflection coefficientA dimensionless quantity that describes the amplitude or power ratio of a reflected wave to an incident wave...
• Reflection rainbowA type of rainbow formed by sunlight that has been reflected off a body of water before entering raindrops...
• ReflectivityA measure of the fraction of incident electromagnetic radiation that is reflected by a surface or object. In...
• Reflectivity cross sectionThis WSR-88D radar product displays a vertical cross section of reflectivity on a grid with heights up to...
• Reflectivity factorA measure used in radar meteorology that quantifies the backscattering cross-section of a collection of...
• ReflectorAn object in the atmosphere that scatters electromagnetic energy back to a remote sensing instrument, such as...
• RefractionThe change in direction of a wave, such as light or sound, as it propagates from one medium into another with...
• Refraction coefficientA dimensionless number that expresses how much a light ray travelling near the ground is bent by the...
• Refraction diagramA graphical representation used to illustrate the bending of waves as they pass from one medium to another or...
• Refraction of water wavesThe phenomenon where water waves change direction as they propagate into areas of different water depth. As...
• Refractive indexA dimensionless quantity that describes how fast light travels through a medium compared to its speed in a...
• RefractivityA measure of how much electromagnetic waves, such as radio waves or light, are bent or refracted as they pass...
• RefractometerAn optical instrument that measures the refractive index of a substance, which is the ratio of the speed of...
• RegelationThe phenomenon where ice melts under pressure and then refreezes when the pressure is removed. This process...
• Regeneration of a depressionThe process by which a weakening or dissipating atmospheric low-pressure system intensifies again. This...
• RegimeA characteristic and persistent pattern of atmospheric circulation or weather conditions over a particular...
• Region of influenceA set of gauged stations chosen separately for each target site in regional frequency analysis, because they...
• Regional air pollutionThe contamination of the atmosphere by pollutants that are transported over distances of tens to hundreds of...
• Regional analysisThe process of interpreting meteorological data from a specific geographic area to understand the current...
• Regional basic synoptic networkA collection of surface and upper-air observing stations established by the World Meteorological Organization...
• Regional broadcastA radio broadcast of selected meteorological information from one WMO Region and from limited adjacent areas...
• Regional climate modelA numerical model that simulates climate processes over a limited geographical domain with higher spatial...
• Regional forecastA weather prediction issued for a specific geographical area that is larger than a local forecast but smaller...
• Regional hazeHaze that is mixed uniformly between the surface and the top of a convective boundary layer.
• Regional Meteorological CenterA facility designated by the World Meteorological Organization (WMO) to provide meteorological analyses...
• Regional Meteorological Telecommunications NetworkA component of the World Meteorological Organization's Global Telecommunication System responsible for the...
• RegressionA statistical method used to model the relationship between a dependent variable and one or more independent...
• Regression analysisThe statistical process of estimating the relationships among variables, particularly to determine how a...
• Regression coefficientA numerical value that quantifies the change in the dependent variable for a one-unit change in an...
• Regression lineA straight line drawn through a scatter plot of data points that best represents the linear relationship...
• Regular broadcastA scheduled transmission of meteorological information, such as forecasts and observations, at predetermined...
• Relative angular momentumThe angular momentum of a fluid parcel about the Earth's axis computed from its motion relative to the...
• Relative coordinate systemA frame of reference that is in motion, typically rotating, with respect to an absolute or inertial...
• Relative currentA current computed by the dynamic method from the slope of isobaric surfaces, taken relative to a chosen...
• Relative evaporationThe ratio of the actual rate of evaporation from a surface to the potential rate of evaporation under ideal...
• Relative frequencyThe proportion of times a specific event or outcome occurs within a given set of observations or experiments...
• Relative humidityThe ratio of the amount of water vapor actually present in the air to the maximum amount of water vapor the...
• Relative humidity with respect to iceThe ratio of the actual water vapor pressure in the air to the saturation vapor pressure over a flat ice...
• Relative ionospheric opacity meterAn instrument, often abbreviated as RIOMETER, that measures the absorption of cosmic radio noise by the...
• Relative momentumThe momentum of an object or fluid parcel as observed from a moving or rotating frame of reference. It...
• Relative permeabilityThe ratio of the effective permeability of a porous medium, such as soil, to a specific fluid when other...
• Relative permittivityA dimensionless quantity that describes the ability of a material to store electrical energy in an electric...
• Relative reductionA measure of the decrease in a quantity expressed as a fraction or percentage of a baseline or reference...
• Relative sea levelThe elevation of the sea surface with respect to a fixed point on the adjacent land. This measurement...
• Relative sunspot numberA measure of solar activity, calculated by summing the number of individual sunspots and ten times the number...
• Relative velocityThe velocity of an object or fluid parcel as observed from a moving frame of reference, such as the Earth's...
• Relative vorticityThe component of the vorticity vector perpendicular to the Earth's surface, calculated with respect to a...
• Relative windThe wind with reference to a moving point. Sometimes called APPARENT WIND. See also APPARENT WIND, TRUE WIND.
• Relaxation methodAn iterative numerical technique used to solve systems of equations, particularly those arising from finite...
• Relaxation timeThe characteristic time scale over which a system returns to equilibrium after being perturbed. In...
• Relaxed eddy accumulationA micrometeorological technique used to measure the turbulent flux of trace gases or particles between the...
• RELBLReliable
• RelocatedA term used in an advisory to indicate that a vector drawn from the preceding advisory position to the latest...
• Remote observing system automationA type of automated data transmitter used by NWS Cooperative Program observers.
• Remote sensingThe science of obtaining information about Earth's surface and atmosphere from a distance, typically using...
• REPRepresent/Representative
• Replace and RouteA methodology that ingests the official streamflow forecasts issued by the NWS RFCs at AHPS gauge locations...
• ReportA weather report is a statement of the actual weather conditions observed at a specific time at a specific...
• Representative basinA small, well-defined drainage basin selected for intensive hydrological and meteorological monitoring to...
• Representative meteorological observationA measurement of an atmospheric variable that accurately reflects the conditions of the surrounding...
• RepresentativenessThe degree to which a meteorological measurement or observation accurately reflects the conditions of a...
• Research to OperationsA formal process for moving new scientific results, observing technologies and modeling methods from research...
• ReservoirA natural or artificial storage area for water, such as a lake, pond, or underground aquifer. In the context...
• Reservoir compoundsAtmospheric chemical species that temporarily store reactive atoms or radicals, releasing them later to...
• ReshabarA strong, very turbulent, dry northeasterly wind of the bora type that blows down the mountain ranges of...
• Residence timeThe average length of time that a substance, such as a pollutant or a water molecule, remains within a...
• ResidualThe difference between an observed or measured value and the value predicted by a model or statistical...
• Residual depression storageThe volume of water that remains trapped in surface depressions and irregularities after surface runoff has...
• Residual layerThe layer of air left above the stable nocturnal boundary layer after daytime convection ceases, typically...
• Residual mass curveA graphical representation of the cumulative departure of a time series from its long-term mean, used in...
• Residual moistureAtmospheric moisture which lingers over an area after the main weather system has departed.
• Residual varianceThe portion of the total variance in a dependent variable that is not explained by the independent variables...
• ResistanceThe opposition offered by a medium or object to the flow of energy, mass, or momentum. In meteorology, this...
• Resistance thermometerA temperature-measuring device that operates on the principle that the electrical resistance of certain...
• ResistivityA fundamental electrical property of a material that quantifies how strongly it resists the flow of electric...
• ResonanceA phenomenon where a system responds with maximum amplitude when subjected to an external forcing at or near...
• Resonance fluorescenceThe process where an atom or molecule absorbs a photon of a specific wavelength and then re-emits a photon of...
• Resonance theoryA theory of atmospheric tides proposing that the unexpectedly large semidiurnal solar tide in surface...
• Resonance troughA large-scale pressure trough that forms at a suitable wavelength from a dominant trough, as part of the...
• Resonance waves over hillsAtmospheric waves that are generated and amplified as stable airflow passes over mountainous terrain...
• ResonatorA system or device that exhibits resonance, meaning it oscillates with greater amplitude at some frequencies...
• ResponderThe part of a transponder that automatically transmits a reply when it is interrogated, and the transmitter...
• Response functionA mathematical expression that describes the output or reaction of a system to an external input or forcing...
• Response timeIn hydrologic terms, the amount of time in which it will take a watershed to react to a given rainfall event
• Responsive parameterizationA way of setting turbulent mixing in a boundary-layer model so that the mixing responds to the state of the...
• Rest massThe intrinsic mass of a particle or object as measured in a frame of reference where it is stationary. In...
• RestoringTo return an atmospheric or oceanic system to a state of equilibrium after a perturbation. This process...
• ResultantA single vector that represents the combined effect of two or more individual vectors acting on a point or...
• Resultant windThe vector sum of all individual wind vectors observed or calculated over a specific period or at a...
• Retarded flowA fluid motion characterized by a decrease in velocity over time or along a streamline. In the atmosphere...
• Retarding basinA man-made or natural depression designed to temporarily store excess stormwater runoff and release it slowly...
• Retention curveA graph that describes the relationship between the water content of a soil and the corresponding soil water...
• Retention storageThe portion of precipitation that is held on or in the land surface and does not contribute to streamflow or...
• Retrograde depressionA low-pressure system that moves in a direction opposite to the prevailing steering flow in the upper...
• Retrograde waveA wave that propagates in a direction opposite to the mean flow of the medium in which it exists. In the...
• RetrogressionThe westward movement or displacement of an atmospheric feature, such as a trough or ridge, against the...
• RetroreflectionThe reflection of radiation, particularly light, from a surface in which the reflected rays travel back along...
• RetroreflectorA device or surface designed to reflect incident radiation directly back towards its source, maintaining the...
• Return flowIrrigation water that is not consumed by evapotranspiration and flows back to its source or to another...
• Return periodThe average interval of time between occurrences of an event of a specified magnitude or greater. In...
• Return strokeThe highly luminous and energetic discharge of electricity that propagates rapidly upward from the ground to...
• Returning polar maritime airPolar maritime air that first moves south over the Atlantic and then recurves north and east, so that it...
• Reversal of the monsoonThe seasonal change in the direction of the prevailing winds associated with the monsoon system. This shift...
• Reversal temperatureThe specific temperature at which a spectral line for a given substance transitions from being an absorption...
• Reverse cellA circulation in a vertical plane that is thermally indirect, meaning cooler air rises relative to warmer...
• Reverse flow thermometer housingA housing for an aircraft air-temperature sensor in which the incoming air is turned through about 180...
• Reverse-oriented monsoon troughA monsoon trough in the western North Pacific whose axis is aligned from northeast to southwest, the reverse...
• Reversible moist-adiabatic processA thermodynamic process in the atmosphere where a saturated air parcel expands or compresses without...
• Reversible processA thermodynamic process that can be reversed by an infinitesimal change in external conditions, returning...
• Reversing currentA tidal current that flows alternately in approximately opposite directions, with a period of slack water at...
• Reversing thermometerA mercury-in-glass thermometer used in oceanography to record water temperature at a chosen depth, mounted on...
• Revolving stormA cyclonic weather system characterized by a closed, low-pressure center with winds rotating around it. This...
• Rex BlockA blocking pattern where there is an upper level high located directly north of a closed low.
• Reynolds averagingA mathematical technique used in fluid dynamics to decompose a flow variable into a time-averaged mean...
• Reynolds effectA process of cloud droplet growth in which water evaporates from droplets that are warmer than their...
• Reynolds numberA dimensionless quantity in fluid mechanics that predicts the flow patterns of different fluid flow...
• Reynolds stressesThe components of the total stress tensor that arise from the turbulent fluctuations of fluid velocity in a...
• RF signalAn electromagnetic wave oscillating at a radio frequency, used to transmit information through space. In...
• RFCRiver Forecast Center. Centers that serve groups of Weather Service Forecast offices and Weather Forecast...
• RGDRagged
• RGNRegion
• RHRelative Humidity - a dimensionless ratio, expressed in percent, of the amount of atmospheric moisture...
• RHIRange-Height Indicator
• Rhumb-line courseA navigational path that follows a constant compass bearing, crossing all meridians of longitude at the same...
• Ribbon lightningA type of lightning discharge that appears as multiple parallel streaks or a broad, luminous band in the sky...
• RibutA localized, violent squall or thunderstorm that occurs in the vicinity of Sumatra and the Malay Peninsula...
• Richardson numberA dimensionless parameter in fluid dynamics that expresses the ratio of buoyancy forces to shear forces in a...
• RidgeAn elongated area of relatively high atmospheric pressure, the opposite of a trough, characterized by...
• Ridge iceIn hydrologic terms, ice piled haphazardly one piece over another in the form of ridges or walls.
• Ridge lineThe axis of maximum atmospheric pressure within an elongated high-pressure area or ridge. On a weather map...
• Right ascensionAn astronomical coordinate that specifies the angular distance of a celestial body eastward along the...
• Right entrance regionUsed interchangably with Right Rear Quadrant; the area upstream from and to the right of an upper-level jet...
• Right moverA thunderstorm that moves appreciably to the right relative to the main steering winds and to other nearby...
• Right rear quadrant(Abbrev. RRQ) - Used interchangably with Right Entrance Region; the area upstream from and to the right of an...
• Right-hand rotationA convention used to describe the direction of rotation, where if the thumb of the right hand points in the...
• Right-handed rectangular coordinatesA three-dimensional coordinate system where the x, y, and z axes are mutually perpendicular, and their...
• RimeAn opaque, white, granular deposit of ice formed by the rapid freezing of supercooled water droplets on a...
• Rime fogA type of fog that forms when supercooled water droplets freeze upon contact with surfaces, creating rime...
• Rime iceAn opaque, granular ice deposit that forms when supercooled water droplets freeze rapidly upon impact with a...
• Ringelmann chartA series of charts used to visually estimate the density or opacity of smoke emitted from industrial stacks...
• RIOGDRio Grande
• Riometer(Relative Ionospheric Opacity meter). A specially designed radio receiver for continuous monitoring of cosmic...
• RipA strong, narrow channel of water moving swiftly away from the shore, often as a result of wave and wind...
• Rip currentA strong, narrow, and fast-moving channel of water that flows away from the shore and out to sea...
• Riparian zoneIn hydrologic terms, a stream and all the vegetation on its banks.
• Ripening of snowThe process by which a snowpack undergoes changes in its physical properties, primarily due to repeated...
• RippleA small, undulating wave on the surface of a fluid, such as water or sand, caused by wind or other...
• Ripple waveA small, capillary wave on the surface of water, primarily controlled by surface tension rather than gravity...
• Rise timeThe time interval over which a signal or a system's response increases from a specified lower percentage to a...
• Rising limbThe initial segment of a hydrograph that shows an increase in streamflow or river discharge following a...
• Rising tideThe phase of the tide during which the water level in a coastal area or estuary is increasing, moving from...
• RiverA natural flowing watercourse, usually freshwater, that flows towards an ocean, sea, lake, or another river...
• River basinThe entire geographical area drained by a river and its tributaries, encompassing all the land from which...
• River flood statementThis product is used by the local National Weather Service Forecast Office (NWFO) to update and expand the...
• River flood warningThis is product is issued by the local National Weather Service Forecast Office (NWFO) when forecast points...
• River floodingThe rise of a river to an elevation such that the river overflows its natural banks causing or threatening...
• River forecastA prediction of future river conditions, including water levels, flow rates, and potential for flooding, for...
• River forecast centerCenters that serve groups of Weather Service Forecast offices and Weather Forecast offices, in providing...
• River gageA device for measuring the river stage.
• River gage datumThe arbitrary zero datum elevation which all stage measurements are made from.
• River gaugeAn instrument or system used to measure and record the water level, or stage, of a river or stream at a...
• River ice statementA public product issued by the RFC containing narrative and numeric information on river ice conditions.
• River observing stationAn established location along a river designated for observing and measuring properties of the river.
• River recreation statementA statement released by the NWS to inform river users of current and forecast river and lake conditions...
• River stageThe height of the water surface in a river or stream relative to a fixed reference point, known as a datum...
• River statementA NWS product issued to communicate notable hydrologic conditions which do not involve flooding, i.e., within...
• River surface temperatureThe temperature of the water at or near the surface of a river. This measurement influences local atmospheric...
• River systemA network of interconnected rivers and their tributaries that drain a specific geographical area, known as a...
• RLSRelease
• RLTVRelative
• RMNRemain
• RMTNRegional Meteorological Telecommunications Network
• RMVremove
• RNFLRainfall
• Road weatherThe atmospheric conditions that directly impact transportation infrastructure and vehicle operations...
• Roaring fortiesA geographical zone in the Southern Hemisphere, located between 40 and 50 degrees south latitude...
• ROBA radiosonde observation providing a vertical profile of atmospheric conditions such as temperature...
• Robin Hood's windA British name for raw, penetrating weather in which the damp air is saturated and close to freezing. Despite...
• Robin sphereA rigid, metalized, inflatable balloon used to measure high-altitude wind speed and direction. Deployed from...
• Robitzsch actinographA type of bimetallic strip pyranometer used to measure global solar radiation, which is the total solar...
• RocketA missile, spacecraft, or other vehicle propelled by a rocket engine, often used in meteorology to carry...
• Rocket lightningA rare form of lightning whose luminous channel seems to advance through the air at only about the speed of a...
• RocketsondeAn instrument package launched by a small rocket to measure atmospheric conditions at very high altitudes...
• Rocket-triggered lightningLightning initiated artificially by launching a small rocket that trails a grounded wire into the electric...
• Rockfill damIn hydrologic terms, an embankment dam of earth or rock in which the material is placed in layers and...

568 of 10,702 terms in Meteorology and atmospheric science terminology (MLC-0110). Request the full dataset.