HumusDecayed organic matter. A dark fluffy swamp soil composed chiefly of decayed vegetation.
Hunter gatherersA term applied to people whose diet is based on hunting, fishing, and gathering, as opposed to domesticating animals or plants.
HuntingIncludes big- and small-game hunting, waterfowl hunting, and trapping.
Huntington's diseaseA degenerative brain disorder that usually appears in mid-life. Its symptoms, which include involuntary movement of the face and limbs, mood swings, and…
Hurler syndromeA heritable condition involving deficiency of an enzyme (alpha-L-iduronidase), leading to abnormal accumulations of materials inside cells, then resulting…
Hurricane(abbrev. HURCN) A tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, which the maximum 1-minute sustained surface wind…
Hurricane / TyphoonA tropical cyclone in which the maximum sustained surface wind (using the U.S. 1-minute average) is 64 kt (74 mph or 119 km/hr) or more.
Hurricane Force Wind WarningA warning for sustained winds, or frequent gusts, of 64 knots (74 mph) or greater, either predicted or occurring, and not directly associated with a…
Hurricane Local StatementA public release prepared by local National Weather Service offices in or near a threatened area giving specific details for its county/parish warning…
Hurricane SeasonThe part of the year having a relatively high incidence of tropical cyclones. In the Atlantic, Caribbean, and Gulf of Mexico, and central North Pacific…
Hurricane WarningA warning that sustained winds 64 kt (74 mph or 119 kph) or higher associated with a hurricane are expected in a specified coastal area in 24 hours or…
Hurricane WatchAn announcement of specific coastal areas that a hurricane or an incipient hurricane condition poses a possible threat, generally within 36 hours
HybridA class that is a mixture or combination of 2 or more classes. For example, a Druid can be viewed as a Warrior/Rogue/Priest hybrid.
Hybrid (wet-dry cooling) systemsA variation on a dry cooling system. In this hybrid system, small amounts of water are sprayed as a fine mist into the flow of ambient air being directed…
hybrid arrested translationA method used to identify what protein (s) are encoded by a particular cloned DNA sequence.
hybrid dysgenesisInfertility and an increased incidence of chromosome mutations thought to be caused by the activation of transposons.
Hybrid electric vehicleA vehicle that is powered by two or more energy sources, one of which is electricity.
hybrid released translationA method used to identify the gene product of a cloned gene. The cloned DNA is immobilized and hybridized with a mixed mRNA sample, so that only mRNA…
hybrid seed1. Seed produced by crossing genetically dissimilar parents. 2. In plant breeding, used colloquially for seed produced by specific crosses of selected…
hybrid selectionThe process of choosing individuals possessing desired characteristics from among a hybrid population.
hybrid systemA renewable energy system that includes two different types of technologies that produce the same type of energy; for e.g.
hybrid vigourThe extent to which a hybrid individual outperforms both its parents with respect to one or many traits.
HybridizationThe hydrogen bonding of complementary DNA and/or RNA sequences to form a duplex molecule. (See Northern hybridization, Southern hybridization.)
HybridomaA hybrid cell, composed of a B Iymphocyte fused to a tumor cell, which grows indefinitely in tissue culture and is selected for the secretion of a…
Hyder FlareIn solar-terrestrial terms, a filiment-associated two-ribbon flare, often occurring in spotless regions.
HydrauconeA draft tube in which the emerging water impinges on a plate.
HydraulicPowered by water. Having to do with water in motion.
Hydraulic efficiencyEfficiency of a pump or turbine to impart energy to or extract energy from water.
Hydraulic fillFill material that is transported and deposited using water.
Hydraulic Fill DamAn embankment dam constructed of materials, often dredged, which are conveyed and/or placed by suspension in flowing water.
Hydraulic FlowAtmospheric flow that is similar in character to the flow of water over an obstacle.
Hydraulic Grade LineA line whose plotted ordinate position represents the sum of pressure head plus elevation head for the various positions along a given fluid flow path…
Hydraulic gradientIn an aquifer, the rate of change of total head per unit of distance of flow at a given point and in a given direction.
Hydraulic Head(1) The height of the free surface of a body of water above a given point beneath the surface.
Hydraulic heightHeight to which the water rises behind the dam, and is the difference between the lowest point in the original streambed at the axis or the centerline…
Hydraulic JumpA steady disturbance in the lee of a mountain, where the airflow passing over the mountain suddenly changes from a region of low depth and high velocity…
Hydraulic Mean DepthThe right cross-sectional area of a stream of water divided by the length of that part of its periphery in contact with its containing conduit; the ratio…
Hydraulic PermeabilityThe flow of water through a unit cross-sectional area of soil normal to the direction of flow when the hydraulic gradient is unity.
Hydraulic RadiusThe right cross-sectional area of a stream of water divided by the length of that part of its periphery in contact with its containing conduit; the ratio…
HydraulicsHaving to do with the mechanical properties of water in motion and the application of these properties in engineering.
HydricCharacterized by, or thriving in, an abundance of moisture.
HydrocarbonAny chemical compound containing hydrogen, oxygen, and carbon.
HydrocarbonsSubstances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.
Hydrochlorofluorocarbons (HCFCs)Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric…
hydrocrackingA process in which hydrogen is added to organic molecules at high pressures and moderate temperatures; usually used as an adjunct to catalytic cracking.
Hydroelectric plantElectric powerplant using falling water as its motive force. A power plant that produces electricity from the power of rushing water turning…
Hydroelectric Power PlantA power plant that produces electricity by the force of water falling through a hydro turbine that spins a generator.
Hydroelectric unit (hydrounit)An electric generator and turbine combination which is driven by water flow, thereby converting mechanical energy to electric energy.
Hydrofluorocarbon (HFC)Man-made chemicals, many of which have been developed as alternatives to ozone-depleting substances (ODSs) for industrial, commercial, and consumer…
Hydrofluorocarbons (HFCs)Compounds containing only hydrogen, fluorine, and carbon atoms. They were introduced as alternatives to ozone depleting substances in serving many…
HydrogenA chemical element that can be used as a fuel since it has a very high energy content.
Hydrogen bondA relatively weak bond formed between a hydrogen atom (which is covalently bound to a nitrogen or oxygen atom) and a nitrogen or oxygen with an unshared…
hydrogen-uptake positive(Abbreviation: Hup+). A term describing a micro-organism that is capable of assimilating (or taking up) hydrogen gas.
Hydrogenated Amorphous SiliconAmorphous silicon with a small amount of incorporated hydrogen. The hydrogen neutralizes dangling bonds in the amorphous silicon, allowing charge carriers…
hydrogenationTreatment of substances with hydrogen and suitable catalysts at high temperature and pressure to saturate double bonds.
Hydrogeologic conditionsConditions stemming from the interaction of ground water and the surrounding soil and rock.
Hydrogeologic cycleThe natural process of recycling water from the atmosphere down to (and through) the earth and back to the atmosphere again.
HydrogeologistA person who studies and works with ground water.
HydrogeologyThe geology of ground water, with particular emphasis on the chemistry and movement of water.
HydrographA graphical representation of the stage or discharge as a function of time at a particular point on a watercourse; a time-discharge curve of the unsteady…
Hydrograph SeparationThe process where the storm hydrograph is separated into baseflow components and surface runoff components.
Hydrographic SurveyAn instrumental survey to measure and determine characteristics of streams and other bodies of water within an area, including such things as location…
HydrographyScientific study of physical aspects of all waters on the Earth's surface. Water features in 7.
Hydrologic BudgetAn accounting of the inflow to, outflow from, and storage in, a hydrologic unit, such as a drainage basin, aquifer, soil zone, lake, reservoir, or…
Hydrologic CycleCycle of water movement from atmosphere to Earth by precipitation and its return to the atmosphere by interception, evaporation, runoff, infiltration…
Hydrologic EquationThe water inventory equation (Inflow = Outflow + Change in Storage) which expresses the basic principle that during a given time interval the total inflow…
Hydrologic ModelA conceptual or physically-based procedure for numerically simulating a process or processes which occur in a watershed.
Hydrologic Service AreaHSA. A geographical area assigned to Weather Service Forecast Office's/Weather Forecast Office's that embraces one or more rivers.
Hydrologic Service Area (HSA)A geographical area assigned to Weather Service Forecast Office's/Weather Forecast Office's that embraces one or more rivers.
Hydrologic ServicesA general term referring to the operations, products, verbal communications, and related forms of support provided by the NWS for the Nation's streams…
Hydrologic UnitA geographical area representing part or all of a surface drainage basin or distinct hydrologic feature such as a reservoir, lake, etc.
Hydrologic unit codeAn eight-digit number used to identify a geographic area representing part or all of a surface drainage basin or distinct hydrologic feature.