Weather terms starting with R

192 terms

R Rain
RA Rain
RADAP II RAdar DAta Processor II, attached to some WSR-57 and WSR-74 radar units. It automatically controls the tilt sequence and computes several radar-derived…
radar Acronym for RAdio Detection And Ranging; a radio device or system for locating an object by means of ultrahigh-frequency radio waves reflected from the…
Radar Beam The straight line that a radar pulse travels along. As the radar beam gets further away from the radar, it gets wider and wider.
Radar Coded Message This is an alphanumeric coded message which will be used in preparation of a national radar summary chart.
Radar Cross Section The area of a fictitious, perfect reflector of electromagnetic waves (e.g., metal sphere) that would reflect the same amount of energy back to the radar…
Radar Data Acquisition An acronym for Radar Data Acquisition. The RDA is the hardware component of the NEXRAD system that consists of the radar antenna, transmitter, receiver…
radar doppler The power spectrum and moments of the radar signal expressed as a function of Doppler frequency or Doppler velocity.
Radar Meteorology Branch of meteorology that uses radars for weather observations and forecasts.
Radar Mosaic A radar product that combines information from multiple radars to give a regional or national view of reflectivity or precipitation.
Radar Product Generator (RPG) The RPG is the computer in the NEXRAD system that receives polar-coordinate base radar data from the RDA and processes these data into end-user products.
Radar Range Distance from the radar antenna. The WSR-88D radar has a range for velocity products out to 124 nautical miles and reflectivity products out to 248…
Radar Reflectivity The sum of all backscattering cross-sections (e.g., precipitation particles) in a pulse resolution volume divided by that volume.
Radar Reflectivity Factor (z) z = the sum (over i) of (N_i * D_i^6), where N_i is the number of drops of diameter D_i in a pulse resolution volume.
Radial Velocity Component of motion toward or away from a given location. As "seen" by Doppler radar, it is the component of motion parallel to the radar beam.
radiance A measure of the intensity of the radiant energy flux emitted by a body in a given direction.
Radiation (RAY-dee-AY-shun) Energy released in the form of particle or electromagnetic waves.
Radiation Fog A fog that forms when outgoing longwave radiation cools the near-surface air below its dew point temperature.
Radiation Laws The four physical laws which fundamentally describe the behavior of blackbody radiation: Kirchhoff's law, Planck's law, Stefan-Boltzmann law and Wien's…
Radiational Cooling The cooling of the Earth's surface. At night, the Earth suffers a net heat loss to space due to terrestrial cooling.
Radiational Inversion Used interchangably with Nocturnal Inversion; a temperature inversion that develops during the night as a result of radiational cooling of the surface.
Radiative Forcing Radiative forcing is the change in the net vertical irradiance (expressed in Watts per square metre: Wm-2) at the tropopause due to an internal change or…
radiative heating rate The heating rate due to the divergence of long and shortwave radiative flux; this is a calculated quantity using the state of the atmospheric and…
Radio Emission Emissions of the sun in radio wavelengths from centimeters to dekameters, under both quiet and disturbed conditions. Type I.
Radio Event Flares with Centimetric Bursts and/or definite Ionospheric Event (SID)
radiocarbon (<sup>14</sup>C) a radioactive isotope of carbon. Since it decays with a half-life of 5570 years, its concentration in organic materials relative to the stable…
radiocarbon dating the process of providing an absolute age for a material by using measurements of the amount of radiocarbon it still contains.
Radiofacsimile Also known as HF FAX, radiofax or weatherfax, is a means of broadcasting graphic weather maps and other graphic images via HF radio.
Radiofax Abbreviation for radiofacsimile
Radioisotope Snow Gage A snow water equivalent gage based on the absorption of gamma radiation by snow; this gage can measure up to 55 inches water equivalent with a 2 to 5…
Radiosonde An instrument that is carried aloft by a balloon to send back information on atmospheric temperature, pressure and humidity by means of a small…
Radius of Maximum Winds The distance from the center of a tropical cyclone to the location of the cyclone's maximum winds.
RAFC Regional Area Forecast Center
RAFS Regional Analysis and Forecasting System
Rail A horizontal sash member.
Rain Precipitation that falls to earth in drops more than 0.5 mm in diameter.
Rain Foot Slang for a horizontal bulging near the surface in a precipitation shaft, forming a foot-shaped prominence. It is a visual indication of a wet microburst.
Rain Forest A forest which grows in a region of heavy annual precipitation. There are two major types, tropical and temperate.
rain gage A device, usually a cylindrical container, for measuring rainfall.
Rain Gauge An instrument for measuring the quantity of rain that has fallen.
Rain Induced Fog When warm rain falls through cooler air, water evaporates from the warm rain. It subsequently condenses in the cool air forming fog.
Rain Shadow An area of reduced precipitation on the lee side of a mountain barrier caused by warming of air and dissipation of cloudiness as air descends the barrier.
Rain Shield In a hurricane, a solid or nearly solid area of rain that typically becomes heavier as one approaches the eye.
Rain-free Base A dark, horizontal cloud base with no visible precipitation beneath it. It typically marks the location of the thunderstorm updraft.
Rainbow A flop that contains three different suits, thus no flush can be made on the turn.
Rainfall The amount of precipitation of any type, primarily liquid. It is usually the amount that is measured by a rain gauge.
Rainfall Estimates A series of NEXRAD products that employ a Z-R relationship to produce accumulations of surface rainfall from observed reflectivity.
Range Geographic region in which a given plant or animal normally lives or grows.
Range Folding This occurs when the radar receives a signal return from a pulse other than the most recent pulse.
Range Gate The discrete point in range along a single radial of radar data at which the received signal is sampled.
Range Height Indicator The RHI is a radar display in which the radar scans vertically, with the antenna pointing at a specific azimuth or radial.
Range Normalization A receiver gain function in the radar which compensates for the effect of range (distance) on the received power for an equivalent reflectivity.
Range Resolution The ability of the radar to distinguish two targets along the same radial but at different ranges. it is approximately Â½ the pulse length.
Range Unfolding Process of removing range ambiguity in apparent range of a multitrip target on the radar.
Rangeland Land on which the native vegetation, climax, or natural potential consists predominately of grasses, grasslike plants, forbs, or shrubs.
Rankine Vortex Velocity profile for a symmetric circulation in which the inner core is in solid rotation and tangential winds outside the core vary inversely with radial…
RAOB Radiosonde Observation (Upper-Air Observation)
Rapid Deepening A decrease in the minimum sea-level pressure of a tropical cyclone of 1.75 mb/hr or 42 mb for 24 hours
Rapid Intensification An increase in the maximum sustained winds of a tropical cyclone of at least 30 kt in a 24-h period.
Rapidly Intensifying Indicator for a maritime cyclone whose central pressure is dropping, or is expected to drop, at a rate of 1 MB per hour for 24 hours.
Rawinsonde A radiosonde that is tracked to measure winds.
Rawinsonde Observation A radiosonde observation which includes wind data.
RAWS Remote Automated Weather Stations
Rayleigh Scattering Changes in directions of electromagnetic energy by particles whose diameters are 1/16 wavelength or less.
RCKY Rocky Mountains
RCMD Recommend
RCV Receive
RDG ridge
RDS Radius
Reach Any specified length of stream, channel, or other water conveyance. A portion of a stream or a river.
Real Time When an event is reported as it happens - such as a quick jump in a stock's price or the constantly changing numbers on a market index - you are getting…
Rear Flank Downdraft A region of dry air subsiding on the back side of, and wrapping around, a mesocyclone. It often is visible as a clear slot wrapping around the wall cloud.
Receiver The component of a central receiver solar thermal system where reflected solar energy is absorbed and converted to thermal energy.
Reconnaissance Code An aircraft weather reconnaissance code that has come to refer primarily to in-flight tropical weather observations, but actually signifies any detailed…
Record Event Report This non-routine narrative product is issued by the National Weather Service to report meteorological and hydrological events that equal or exceed…
Recreation Report This National Weather Service product is used to relay reports on conditions for resorts and recreational areas and/or events.
recurrence (ree-KER-ents) Cancer that has recurred (come back), usually after a period of time during which the cancer could not be detected.
Recycling The process of converting materials that are no longer useful as designed or intended into a new product.
Red Flag This a fire weather program which highlights the onset of critical weather conditions conducive to extensive wildfire occurrences.
Red Flag Warning A term used by fire-weather forecasters to call attention to limited weather conditions of particular importance that may result in extreme burning…
Red Watch or Red Box Slang for Tornado Watch.
REF Reference
Reference Mark A relatively permanent point of known elevation which is tied to a benchmark.
reflection The process whereby radiation (or other waves) incident upon a surface is directed back into the medium through which it traveled.
Reflectivity The measure of the efficiency of a radar target in intercepting and returning Electro Magnetic Energy.
reflectivity (dBZ) A measure of the returned power, which is sensitive to the size and number of hydrometeors (i.e., the particle size spectra).
Reflectivity Cross Section This WSR-88D radar product displays a vertical cross section of reflectivity on a grid with heights up to 70,000 feet on the vertical axis and distance up…
Reflectivity Factor The result of a mathematical equation (called the Weather Radar Equation) that converts the analog power (in Watts) received by the radar antenna into a…
Reforestation Planting of forests on lands that have previously contained forests but that have been converted to some other use.
Refraction The change in direction of a ray of light when it passes through one media to another with differing optical densities.
Refractive Index A measure of the amount of refraction. Numerically equal to the ratio of wave velocity in a vacuum to a wave speed in the medium, i.e.
Refractivity Expressed as N; N = (n-1)*106, where n is refractive index and N is a function of temperature, pressure and vapor pressure (in the atmosphere).
Regional Haze Haze that is mixed uniformly between the surface and the top of a convective boundary layer.
relative dating the process of determining the order in which certain events occurred or certain materials were formed.
Relative Humidity A measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature.
Relative Vorticity The sum of the rotation of an air parcel about the axis of the pressure system and the rotation of the parcel about its own axis.
Relative Wind The wind with reference to a moving point. Sometimes called APPARENT WIND. See also APPARENT WIND, TRUE WIND.
RELBL Reliable
Relocated A term used in an advisory to indicate that a vector drawn from the preceding advisory position to the latest known position is not necessarily a…