Glossary of Terms

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  • 30-year historical normal — A statistically adjusted 30-year average officially published by the National Oceanic and Atmospheric Administration every 10 years; also called a "climate normal."


  • Agribusiness — Farming engaged in as a large-scale business operation embracing the production, processing, and distribution of agricultural products and the manufacture of farm machinery, equipment, and supplies.
  • Albedo — The fraction of incoming radiation that is reflected.


  • Barometer — An instrument for determining the weight or pressure of the atmosphere.
  • Barometric pressure — Atmospheric pressure as indicated by a barometer.


  • Climate — The accumulation of daily and seasonal weather events over a long period of time.
    Click here for information about the climate of North Carolina.
  • Convection — Heat transfer in which mass is exchanged. A net movement of mass may occur, but more commonly parcels with different energy amounts change places, so that energy is exchanged without a net movement in mass.
  • Coriolis force — An apparant force which acts solely from the earth's rotation to deflect parcels or objects. It is a function of latitude and speed of object.


  • Degree days — A unit used in estimating fuel requirements for heating a building.
  • Disaster mitigation — Process of lessening the impacts of disasters.
  • Drought — A period of abnormally dry weather sufficiently long enough to cause serious effects on agriculture and other activities in the affected area.
    Click here for information about drought in North Carolina.


  • El Niño — An extensive ocean warming that begins along the coast of Peru and Ecuador. Major El Niño events occur once every 3 to 7 years as a current of nutrient-poor tropical water moves southward along the west coast of South America.
    Click here for information about El Niño.
  • Energy balance — A condition in which the energy budget is balanced; the system neither gains nor loses energy.
  • Energy budget — Measure of energy entering and leaving a system, such as Earth's climate system.


  • Gage height — The height of water in a river or stream above a reference point. In other words, gage height measures the elevation of a water surface (in feet) at a given location.
  • Global teleconnections — Links between changes in weather environmental conditions between distant geographical locations.
  • Groundwater — Water that seeps into the ground and saturates soil or rock. Groundwater is measured based upon the depth (in feet) at which water is first found below the earth's surface.
  • Growing degree days — A form of the degree-day used as a guide for crop planting and for estimating crop maturity dates.


  • Heat flux — The amount of heat transferred in the atmosphere per unit of time through a unit of area.
  • Horticulture — The science or art of cultivating fruits, vegetables, flowers, or ornamental plants.
  • Hurricane — A severe tropical cyclone having winds in excess of 64 knots (74 mph).
    Click here for information about hurricanes in North Carolina.


  • La Niña — A condition where the central and eastern tropical Pacific Ocean turns cooler than normal.
    Click here for information about La Niña.
  • Lapse rate — Rate of decline of temperature with height in the atmosphere.
  • Latent heat — The heat energy required to change a substance from one state to another. It is an important source of atmospheric energy, especially for storms, such as thunderstorms and hurricanes.


  • Mesoscale circulations — Horizontal atmospheric circulation on the order of 10 to 1000 km.


  • Numerical model — A model expressed in mathematical formulas and solved approximately on a computer.


  • Percentile — The rank of a particular value, in a dataset, on a percentage scale from 1 to 99, where the 1st percentile represents the lowest value (minimum), and the 99th percentile represents the highest value (maximum).
  • Photosynthetically active radiation — Specific spectrum of so radiation used by plants in the photosynthesis process.


  • Season — Expressed in terms of the declination angle of the sun, which is the latitude of the point on the surface of the Earth directly under the sun at noon.
  • Solar Radiation — Total radiation from the sun.
  • Storm surge — An abnormal rise of several meters in the ocean level. It is produced by the combination of high water and high winds.
  • Streamflow — A measure of the volume of water that flows past a given point in a river or steam, recorded in cubic-feet per second. Another name for streamflow is discharge. Peak streamflow refers to the highest instantaneous streamflow measurement for a given year.


  • Temperature inversion — A region of negative lapse rate where the temperature increases with altitude.
  • Thermohaline circulation — In the ocean, when temperature and salinity act together. It is a vertical circulation induced by surface cooling, which causes convective overturning.
  • Topography — The natural and manmade features and relief of Earth's surface.
  • Tornado — An intense, rotating column of air that protrudes from a cumulonimbus cloud in the shape of a funnel or a rope whose circulation is present on the ground.
    Click here for information about tornadoes in North Carolina.
  • Tropical cyclone — A violent storm originating over tropical or subtropical waters, characterized by violent rainstorms and high-velocity cyclonic winds.
  • Tropical depression (TD) — A mass of thunderstorms and clouds generally with a cyclonic wind circulation between 20 and 34 knots (23-49mph).
  • Tropical storm (TS) — Organized thunderstorms with a cyclonic wind circulation between 35 and 64 knots (40-74 mph).
  • Troposphere — The atmospheric layer from Earth's surface to the tropopause; that is, the lowest 10-20km of the atmosphere where most weather occurs.


  • Undulation — A wavelike form, outline, or appearance.