Meteorology and atmospheric science terminology · MLC-0110

Meteorology and atmospheric science terms: U (125)

U burstIn solar-terrestrial terms, a fast radio burst spectrum of a flare. It has a U-shaped appear- ance in an...
UARSThe Upper Atmosphere Research Satellite, a NASA observatory launched in 1991 to study the Earth's upper...
UbacThe slope of a mountain or valley that faces away from the general path of the sun, resulting in...
UCP(Unit Control Position): The WSR-88D radar operator uses this to control the entire radar system. One of the...
UGC(Universal Geographic Code) - (e.g. ANZ300 for Western Long Island Sound) are used in many National Weather...
UHFA radio band from 300 megahertz to 3 gigahertz, corresponding to wavelengths from one meter down to ten...
UKMETA medium-range (3 to 7 day) numerical weather prediction model operated by the United Kingdom METeorological...
ULJUpper Level Jet
Ulloa's ringA rare optical phenomenon observed from an aircraft or high mountain, appearing as a bright, white, circular...
Ultimate infiltration capacityThe maximum rate at which water can infiltrate into a soil when the soil is saturated and the surface is...
Ultra high frequencyA segment of the electromagnetic spectrum characterized by radio waves with frequencies between 300 megahertz...
Ultrafine particlesAtmospheric aerosol particles with a diameter less than 100 nanometers, often originating from combustion...
UltrasonicDescribing sound waves with frequencies above the upper limit of human hearing, typically above 20 kilohertz...
UltravioletElectromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, typically...
Ultraviolet indexThis index provides important information to help you plan your outdoor activities in ways that prevent...
Ultraviolet radiationElectromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, abbreviated as...
UmbraIn solar-terrestrial terms, the dark core or cores (umbrae) in a sunspot with penumbra, or a sunspot lacking...
Umkehr effectThe reversal in the trend of the intensity ratio of zenith-sky light at two ultraviolet wavelengths as the...
UncertaintyA quantification of the doubt about the value of a measurement or a forecast, representing the range of...
UncinusA species of cirrus cloud characterized by its comma-like shape, with a hook or a tuft at the end. These...
Unconfined aquiferA water-bearing formation with no impermeable layer above it, so its upper surface, the water table, lies at...
Undamped oscillationA periodic motion or fluctuation in which the amplitude remains constant over time, without any loss of...
UndercastA layer of cloud viewed from above, as from an aircraft or a mountain summit, covering most or all of the sky...
UndercurrentA current that flows beneath a more superficial layer of water or air, moving in a different direction or at...
UnderflowThe lateral motion of water through the upper layers until it enters a stream channel. This usually takes...
UndermeltingThe process by which ice, typically at the base of an ice shelf or glacier, melts due to contact with...
UndersunAn optical effect seen by an observer above a cloud deck when looking toward the sun, as sunlight is...
UndertowA relatively small-scale surf-zone current moving away from the beach. Rip currents form as waves disperse...
Undisturbed motionThe theoretical, large-scale flow of the atmosphere in the absence of smaller-scale perturbations like...
Undular boreA type of atmospheric gravity wave characterized by a series of waves or oscillations that propagate along a...
UndulatusA cloud variety characterized by a wave-like, undulating pattern arranged in layers or patches. This...
Unfiltered modelA type of numerical weather prediction model that directly integrates the full set of primitive equations of...
UnfreezingThe phase transition of a substance from a solid to a liquid state, also known as melting or fusion. In...
Unidirectional vertical wind shearA condition where the wind direction remains constant with height, but its speed changes significantly...
Unifilar electrometerA type of electrometer that uses a single, fine conducting fiber or wire suspended in an electric field to...
Uniform flowA fluid flow in which the velocity vector is constant in magnitude and direction at every point within the...
Uniform layerA stratum within the atmosphere or ocean where certain properties, such as temperature, humidity, or...
UnimodalA distribution having only one localized maximum, i.e., only one peak.
Unimodal spectrumA frequency distribution or spectrum that exhibits a single peak or mode, indicating a dominant size or...
Unit control positionThe WSR-88D radar operator uses this to control the entire radar system. One of the main things that the...
Unit hydrographA conceptual model in hydrology representing the direct runoff response of a watershed to one unit of...
Unit normal distributionA specific type of normal probability distribution with a mean of zero and a standard deviation of one. This...
Unit stormA hypothetical rainfall event of a specified duration and uniform intensity, used as input for a unit...
United States Coast PilotA series of nautical publications produced by the National Oceanic and Atmospheric Administration (NOAA) that...
United States Drought MonitorA multi-agency product that defines and highlights the severity of drought across the ConUS and OConUS based...
Universal functionsA set of dimensionless mathematical expressions used in Monin-Obukhov similarity theory to describe the...
Universal Geographic Code(UGC) - UGC's, (e.g. ANZ300 for Western Long Island Sound) are used in many National Weather Service text...
Universal rain gaugeA recording precipitation gauge of the weighing type, in which rain or snow falls through a funnel into a...
Universal timeA time standard based on the Earth's rotation, serving as a reference for civil timekeeping worldwide. It is...
Unlimited ceilingAn atmospheric condition where the lowest cloud layer is either absent or is at an altitude greater than a...
Unprotected thermometerA thermometer that is directly exposed to the ambient environment without any shielding or housing, making it...
Unrestricted visibilityA meteorological condition where the horizontal visibility is 10 statute miles (16 kilometers) or greater...
Unsaturated flowThe movement of water through a porous medium, such as soil, in which the pores contain both water and air...
Unsaturated hydraulic conductivityThe ability of a porous medium, such as soil, to transmit water when its pores are not completely filled with...
Unsaturated zoneThe region of the subsurface between the land surface and the water table, where the pore spaces in the soil...
UNSBLUnseasonable
UnsettledIn meteorological use: A colloquial term used to describe a condition in the atmosphere conducive to...
Unsharp maskingAn image processing technique applied to meteorological satellite or radar data to accentuate fine details...
Unstable airAn atmospheric condition where a parcel of air, if displaced vertically, continues to move in the direction...
Unstable air massA large body of air characterized by a tendency for vertical motion and convective activity. This occurs when...
Unstable equilibriumA state of balance in which a system, if slightly disturbed from its position, tends to move further away...
Unstable waveA wave in a fluid system, such as the atmosphere or ocean, that grows in amplitude over time. This growth...
UNSTBLUnstable
Unsteady flowFluid motion where the velocity, pressure, or other flow properties at a given point change with time. In...
UpdraftA small-scale current of rising air. If the air is sufficiently moist, then the moisture condenses to become...
Upglide cloudA cloud formation that results from the slow, steady ascent of moist air over a frontal surface or...
Upgradient fluxThe movement of a substance from a region of lower concentration to a region of higher concentration, against...
Upper airThe portion of the atmosphere above the Earth's surface, typically referring to altitudes above the planetary...
Upper atmosphereThe region of Earth's atmosphere above the troposphere, encompassing the stratosphere, mesosphere...
Upper Atmosphere Research SatelliteA NASA satellite launched in 1991 to study the Earth's upper atmosphere, focusing on its chemistry, dynamics...
Upper frontA frontal boundary between two air masses that is present in the middle and upper troposphere but does not...
Upper levelIn weather observing, the term applies to the portion of the atmosphere that is above the lower troposphere...
Upper level disturbanceA disturbance in the upper atmospheric flow pattern which is usually associated with clouds and...
Upper level systemA general term for any large-scale or mesoscale disturbance capable of producing upward motion (lift) in the...
Upper wind chartA meteorological chart that displays wind direction and speed at specific pressure levels or altitudes in the...
Upper-air climatologyThe study of long-term average conditions and patterns of atmospheric variables at altitudes above the...
Upper-air disturbanceA perturbation in the flow patterns of the upper atmosphere, often characterized by a trough or ridge in the...
Upper-air observationA measurement of atmospheric conditions at altitudes above the Earth's surface, providing data on pressure...
Upper-air soundingA vertical profile of atmospheric properties, including temperature, humidity, pressure, and wind, obtained...
Upper-air stationA facility equipped to make and transmit upper-air observations of atmospheric conditions. These stations...
Upper-air Weather ChartWeather maps that are produced for the portion of the atmosphere above the lower troposphere, generally at...
Upper-level anticycloneA high-pressure system located in the middle or upper troposphere, characterized by clockwise circulation in...
Upper-level chartA meteorological map that displays atmospheric conditions at a specific pressure level above the Earth's...
Upper-level cycloneA low-pressure system in the middle or upper troposphere that is not directly associated with a surface...
Upper-level ridgeAn elongated area of relatively high atmospheric pressure in the middle or upper troposphere, characterized...
Upper-level troughAn elongated area of relatively low geopotential height in the upper atmosphere, indicating a dip in the...
UPRUpper
Upslope flowSame as Orographic Lifting; air that flows toward higher terrain, and hence is forced to rise. The added lift...
Upslope fogA type of fog that forms when moist, stable air is forced to rise along a topographic slope, such as a...
Upslope windA wind that blows up a topographic slope, often driven by differential heating or the forced ascent of air...
UPSLPUpslope
UpstreamThe direction opposite to the flow of a fluid, such as the wind in the atmosphere. An object or location is...
Upstream slopeThe part of the dam which is in contact with the reservoir water. On earthen dams, this slope must be...
UPSTRMUpstream
Up-valley WindA diurnal thermally driven flow directed up a valley's axis, usually occurring during daytime; part of the...
Upvalley windA localized wind that blows up a valley during the daytime, driven by differential heating between the valley...
UpwellingThe process by which cold, nutrient-rich water from the deep ocean rises to the surface, replacing warmer...
UpwindThe direction against the prevailing wind, or the direction from which the wind is blowing. If a weather...
Upwind effectThe influence exerted by conditions or features located in the direction from which the wind is blowing on a...
Urban and small stream flood advisoryThis advisory alerts the public to flooding which is generally only an inconvenience (not life-threatening)...
Urban and small stream floodingFlooding of small streams, streets, and low-lying areas, such as railroad underpasses and urban storm drains...
Urban boundary layerThe lowest part of the atmosphere directly influenced by an urban area, characterized by altered thermal...
Urban canopyThe layer of the urban atmosphere extending from the ground up to the average height of buildings and other...
Urban canopy layerThe lowest part of the urban atmosphere, extending from the ground to roughly the average height of buildings...
Urban canyonsThe street-level spaces between tall buildings in urban areas, forming a confined atmospheric volume. These...
Urban climateThe localized climate of an urban area, which is significantly modified from the surrounding rural climate...
Urban climatologyThe scientific study of the climate within urban areas and how it differs from the climate of surrounding...
Urban effectsModifications to local weather and climate caused by the presence of urban areas. These effects include the...
Urban flash flood guidanceA specific type of flash flood guidance which estimates the average amount of rain needed over an urban area...
Urban floodingFlooding of streets, underpasses, low lying areas, or storm drains. This type of flooding is mainly an...
Urban heat islandA phenomenon where urban areas experience significantly higher temperatures than their surrounding rural...
Urban hydrologyThe study of water movement and storage within urban environments, considering the impacts of impervious...
Urban runoffPrecipitation that flows over impervious urban surfaces, such as roads, rooftops, and parking lots, instead...
Urban-rural circulationA localized atmospheric circulation pattern driven by temperature differences between urban areas and...
U.S. Geological Survey(Abbrev. USGS)- The Federal Agency chartered in 1879 by congress to classify public lands, and to examine the...
UTCBy international agreement, the local time at the prime meridian, which passes through Greenwich, England...
UVElectromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, typically...
UV and IR hygrometersInstruments that measure atmospheric humidity by analyzing the absorption of ultraviolet (UV) or infrared...
UV indexUltraviolet Index- This index provides important information to help you plan your outdoor activities in ways...
UV-AA band of ultraviolet radiation with wavelengths ranging from approximately 315 to 400 nanometers. This is...
UV-BUltraviolet B radiation, a segment of the electromagnetic spectrum with wavelengths ranging from 280 to 315...
UV-CA band of ultraviolet radiation with the shortest wavelengths, typically ranging from approximately 100 to...
UVMUpward Vertical Motion (also known as Upward Vertical Velocity)
UVVUpward Vertical Velocity (rising air)
UWNDSUpper Winds

125 of 10,702 terms in Meteorology and atmospheric science terminology (MLC-0110). Request the full dataset.