Meteorology and atmospheric science terminology · MLC-0110

Meteorology and atmospheric science terms: R (579)

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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 in the atmosphere where atmospheric refractivity decreases with height at a rate greater than the...
• 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 distance used in radar applications, representing the distance light travels in one microsecond in...
• 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 species characterized by broad, parallel bands or streaks that appear to converge toward a point on...
• Radio acoustic sounding systemAn instrument system that measures atmospheric temperature profiles by simultaneously transmitting acoustic...
• Radio atmometerAn instrument designed to measure the rate of evaporation from a continuously wetted surface, integrating the...
• 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 radio waves from a transmitter are tangential to the Earth's surface. Due...
• 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 snowpack by detecting 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
• RafficheA sudden, brief increase in wind speed, often associated with convective activity or the passage of a frontal...
• RAFOS technologyA system for tracking ocean currents using neutrally buoyant floats that emit low-frequency sound signals...
• 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 phenomenon observed in the sky where crepuscular rays appear to converge at a point opposite the sun, due...
• 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 factorA numerical value used in some empirical formulas to relate rainfall intensity to soil erosion. The factor...
• 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 phase in the development of precipitation within a mixed-phase cloud where ice crystals grow at the...
• 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 structureThe gently sloping boundary surface of a front, particularly a warm front, where warmer, less dense air...
• RamsondeA ruggedized instrument package, similar to a dropsonde, designed to be released from an aircraft into severe...
• 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 distortionA misrepresentation of the true distance to a target in radar displays, often caused by incorrect calibration...
• 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 a sequence of images at very short time intervals, often on the order of seconds or less...
• 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...
• Rare optical phenomenonAn infrequent atmospheric optical event resulting from the interaction of light with atmospheric particles...
• 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...
• RawDescribing observational data that has been collected directly from an instrument but has not yet undergone...
• 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 process of reprocessing historical meteorological observations using a fixed, modern numerical...
• 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 violent, squally thunderstorm wind occurring over the Gulf of Davao in the Philippines. This localized wind...
• 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 coefficientA quantitative measure of the rate at which positive ions and electrons or negative ions recombine in a gas...
• 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 observationA meteorological measurement that surpasses all previously recorded values for a specific location and time...
• 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 duration required for a meteorological sensor or system to return to its initial state or a specified...
• 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 optical phenomenon observed at sunrise or sunset, appearing as a brief, reddish flash of light above...
• Red noiseA type of noise or random process where the power spectral density decreases with increasing frequency...
• Red Sea WaterA distinct water mass characterized by high salinity and temperature, formed in the Red Sea due to intense...
• 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 used in fluid dynamics that represents the ratio of inertial forces to gravitational...
• 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 quantity that describes the extent to which electromagnetic waves, particularly light, are...
• 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 influenceThe geographical area where atmospheric conditions directly impact a specific forecast point or phenomenon...
• 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 broadcastThe dissemination of meteorological information, such as forecasts, warnings, and observations, to a specific...
• 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...
• RegisterA device or mechanism used to record or display specific meteorological data or events over time. This can...
• 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 parcel of fluid or an air mass with respect to a rotating coordinate system, such...
• Relative coordinate systemA frame of reference that is in motion, typically rotating, with respect to an absolute or inertial...
• Relative currentThe movement of a fluid, such as air or water, as observed from a frame of reference that is itself in...
• 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 of a troughThe process by which an atmospheric trough, an elongated area of relatively low atmospheric pressure, weakens...
• 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 transitioning new scientific discoveries, observational technologies, and modeling...
• 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, cold, and gusty wind that blows from the mountains of the Caucasus range across the Caspian Sea...
• 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 portion of the atmospheric boundary layer that remains after the convective mixing of the daytime...
• 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 concept explaining how a system responds with amplified oscillations when subjected to an external forcing...
• Resonance troughAn elongated area of relatively low atmospheric pressure that forms and persists due to resonance between...
• Resonance waves over hillsAtmospheric waves that are generated and amplified as stable airflow passes over mountainous terrain...
• Resonance waves over thermalsAtmospheric gravity waves that form when stable air flows over a thermal plume, creating oscillations in the...
• ResonatorA system or device that exhibits resonance, meaning it oscillates with greater amplitude at some frequencies...
• ResponderAn individual or organization that provides assistance or takes action in response to an event, such as a...
• Response analysisThe study of how a system reacts to external forcing or internal perturbations. In meteorology, this involves...
• 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 method in numerical weather and climate models where the parameters used to represent sub-grid-scale...
• 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 flowThe movement of air or water that completes a circulation pattern, often occurring at a different level or...
• 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 airA type of air mass that originates over polar ocean regions, then travels southward over warmer waters, and...
• 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 cellAn atmospheric circulation pattern that moves in the opposite direction to the typical or expected flow for a...
• Reverse flow thermometer housingA specialized enclosure designed to protect a temperature sensor from direct solar radiation and...
• Reverse-oriented monsoon troughA monsoon trough that is displaced from its typical position or exhibits an unusual orientation, often...
• 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 specialized mercury-in-glass thermometer designed to record temperature at a specific depth in the ocean or...
• 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 effectThe influence of the Reynolds number on the behavior of a fluid, particularly the transition from laminar to...
• 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...
• Rime rodA cylindrical instrument used to measure the accretion of rime ice in cold environments. It consists of a...
• Rinehart projectionA method for displaying weather radar data that corrects for Earth's curvature and atmospheric refraction of...
• 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...

579 of 10,816 terms in Meteorology and atmospheric science terminology (MLC-0110). Request the full dataset.