Recombination frequencyThe frequency at which crossing over occurs between two chromosomal loci--the probability that two loci will become unlinked during meiosis.
recombinational hot spotA chromosomal region where recombination appears to occur more frequently than expected.
Reconnaissance CodeAn aircraft weather reconnaissance code that has come to refer primarily to in-flight tropical weather observations, but actually signifies any detailed…
reconstructed cellA viable transformed cell resulting from genetic engineering.
Record Event ReportThis non-routine narrative product is issued by the National Weather Service to report meteorological and hydrological events that equal or exceed…
Record of Decision (ROD)The Record of Decision (ROD) is a public document that explains which cleanup alternatives will be used to clean up a Superfund site.
Recovery boilerA pulp mill boiler in which lignin and spent cooking liquor (black liquor) is burned to generate steam.
RecreationRecreational opportunities at more than 1,900 federal recreation sites managed by the Bureau of Reclamation and other federal agencies can be found at the…
Recreation AreaAn area that allows for recreational fishing, diving, boating, kayaking, and other recreational activities.
Recreation ReportThis National Weather Service product is used to relay reports on conditions for resorts and recreational areas and/or events.
Recreational benefitValue of recreational activity to the recreationist, usually measured in dollars above the cost of participating in the recreational activity (travel…
RecruitmentRecruitment is the process to attract the attention of individual(s) who may apply for employment.
Rectangular weirA contracted or suppressed weir with a horizontal crest, rectangular in shape, having vertical sides. See weir.
RectifierAn electrical device for converting alternating current to direct current. The chamber in a cooling device where water is separated from the working fluid…
RecuperatorA heat exchanger in which heat is recovered from the products of combustion.
recurrence(ree-KER-ents) Cancer that has recurred (come back), usually after a period of time during which the cancer could not be detected.
Recurrence IntervalThe average period in years between storm events equal to or larger than a given amount.
Recurrent CostsCosts that are repetitive and occur when an organization produces similar goods or services on a continuing basis.
RecyclingThe process of converting materials that are no longer useful as designed or intended into a new product.
Red Blood CellsCells that carry oxygen throughout the body (also called erythrocytes).
Red FlagThis a fire weather program which highlights the onset of critical weather conditions conducive to extensive wildfire occurrences.
Red Flag WarningA term used by fire-weather forecasters to call attention to limited weather conditions of particular importance that may result in extreme burning…
ReddAn individual nest or depression in the gravel excavated by trout other members of the trout and salmon family for depositing eggs.
RedshiftA change in the frequency or wavelength of light. This can arise from motion of the source (Doppler shift), expansion of space, or strong gravitational…
reduction divisionThe first division of meiosis in which the chromosome number is reduced from the somatic to the gametic number.
Reference MarkA relatively permanent point of known elevation which is tied to a benchmark.
Reference priceThe settlement price of a derivatives contract, based on a particular location and commodity; An estimated electricity offer price based on operating and…
RefillMaterial which had previously been excavated as a result of construction activities and again placed to the lines as shown on the drawings.
ReflectanceThe amount (percent) of light that is reflected by a surface relative to the amount that strikes it.
reflectionThe process whereby radiation (or other waves) incident upon a surface is directed back into the medium through which it traveled.
Reflective CoatingsMaterials with various qualities that are applied to glass windows before installation.
Reflective GlassA window glass that has been coated with a reflective film and is useful in controlling solar heat gain during the summer.
Reflective Window FilmsA material applied to window panes that controls heat gain and loss, reduces glare, minimizes fabric fading, and provides privacy.
ReflectivityThe 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 SectionThis 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 FactorThe result of a mathematical equation (called the Weather Radar Equation) that converts the analog power (in Watts) received by the radar antenna into a…
ReflectorA component of a solar energy facility that reflects incident sunlight to a desired location or component within the facility, allowing it to be converted…
Reflector LampsA type of incandescent lamp with an interior coating of aluminum that reflects light to the front of the bulb.
ReforestationPlanting of forests on lands that have previously contained forests but that have been converted to some other use.
Reformulated gasoline (RFG)Gasoline that has altered composition or characteristics to reduce emissions of pollutants from vehicles in accordance with the Clean Air Act.
RefractionThe change in direction of a ray of light when it passes through one media to another with differing optical densities.
Refractive IndexA 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.
RefractivityExpressed 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).
Refractory LiningA lining, usually of ceramic, capable of resisting and maintaining high temperatures.
RefrigerantThe compound (working fluid) used in air conditioners, heat pumps, and refrigerators to transfer heat into or out of an interior space.
RefrigerationThe process of the absorption of heat from one location and its transfer to another for rejection or recuperation.
Refrigeration CapacityA measure of the effective cooling capacity of a refrigerator, expressed in Btu per hour or in tons, where one (1) ton of capacity is equal to the heat…
Refrigeration CycleThe complete cycle of stages (evaporation and condensation) of refrigeration or of the refrigerant.
Refuge compatibility requirementsRequirements under the Refuge Administration Act that all uses of a national wildlife refuge must be compatible with the purpose for which the refuge was…
refugium(pl.: refugia) An area set aside to provide protection/escape from ecological consequences occurring elsewhere.
Refuse-Derived Fuel (RDF)A solid fuel produced by shredding municipal solid waste (MSW). Noncombustible materials such as glass and metals are generally removed prior to making…
regenerationIn biology, regrowth of damaged or destroyed tissue or body part.
Regeneration harvestA timber harvest method that removes selected trees in the existing stand to a density that allows for the establishment of a new even-aged stand below.
Regeneration with reservesSimilar to a regeneration harvest, except that a number of green trees are left standing to meet other resource needs such as wildlife habitat.
Regenerative BrakingA feature of hybrid and plug-in electric vehicles that captures energy normally lost during braking by using the electric motor as a generator and storing…
Regenerative CoolingA type of cooling system that uses a charging and discharging cycle with a thermal or latent heat storage subsystem.
Regenerative HeatingThe process of using heat that is rejected in one part of a cycle for another function or in another part of the cycle.
Regenerative medicineMedical interventions that aim to repair damaged organs, most often by using stem cells to replace cells and tissues damaged by aging and by disease.
Region of Influence (ROI)Area occupied by affected resources and the distances at which impacts associated with license renewal may occur.
Region or RegionalAn area inclusive of and determined by participating national system sites and systems that is based on common management interests, similar or linked…
Regional HazeHaze that is mixed uniformly between the surface and the top of a convective boundary layer.
Regional officeFive Reclamation offices in the 17 Western States that supervise area, field, and project offices in their respective geographic locations.
Regional Response Team (RRT)Regional planning and coordination of preparedness and response actions are accomplished through the RRT.
Regional Transmission Group (RTG)A voluntary organization of transmission owners, transmission users, and other entities interested in coordinating transmission planning, expansion…
Regional Transmission Organization (RTO)A voluntary organization of electric transmission owners, transmission users and other entities approved by the Commission to efficiently coordinate…
Regular-track proposalsProposals on public land with pending applications considered as potential future projects, but not necessarily foreseeable projects, since not all…
Regulating dam (reregulating dam)A dam impounding a reservoir from which water is released to regulate the flow downstream. See afterbay dam.
Regulating Gate (Regulating Valve)A gate or valve that operates under full pressure and flow conditions to throttle and vary the rate of discharge.
regulatorSubstance regulating growth and development of cells, organs, etc.
Regulatory FloodwaySome maps show an area where construction regulations require special provisions to account for this extra hazard. This is a regulatory floodway.
Regulatory geneA gene whose protein controls the activity of other genes or metabolic pathways.
Reid vapor pressure (RVP)A standard measurement of a liquid´s vapor pressure at 100 degrees Fahrenheit. An indication of the propensity of the liquid to evaporate.
ReimbursableCosts of constructing, operating, or maintaining a Reclamation project that are repaid to the Federal Government by some other individual, entity, or…
ReinjectionThe feeding of unburned char and fly ash obtained from mechanical collectors into the furnace for further combustion.
rejuvenation1. Reversion from adult to juvenile stage. 2. The process of regular reproduction of seed stocks or collections in gene banks, in order to ensure…
RelampingThe replacement of a non-functional or ineffective lamp with a new, more efficient lamp.
relative biological effectiveness (RBE)An adjustment factor used to adjust an absorbed dose to account for its relative potential to do damage in biological tissue.
Relative BrightnessHow bright one object is compared to another. If they have the same intrinsic brightness then the relative brightness tells us the ratio of distances to…
relative datingthe process of determining the order in which certain events occurred or certain materials were formed.
Relative densityUsed in construction control for cohesionless soils where the in-place density is compared to the minimum and maximum density of the soil from laboratory…
Relative HumidityA measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature.
Relative VorticityThe 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 WindThe wind with reference to a moving point. Sometimes called APPARENT WIND. See also APPARENT WIND, TRUE WIND.
RelativityGalileo first developed the principle of relativity, being the postulate that the laws of physics should take the same form for all observers in uniform…