“Glossary of meteorology”的意思、由来-开放百科全书

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Glossary of meteorology

释义

A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
See also
References
External links

This glossary of meteorology is a list of terms and concepts relevant to meteorology and the atmospheric sciences, their sub-disciplines, and related fields.

{{compact ToC|side=yes|center=yes|nobreak=yes|seealso=yes|refs=yes}}{{weather}}{{Atmospheric sciences}}

A

{{glossary}}{{term|advection}}{{defn|The horizontal transport of some property of the {{gli|atmosphere}} or ocean, such as thermal energy, {{gli|humidity}}, or salinity. In the context of meteorology, the related term convection generally refers to vertical transport.}}{{term|actinoform}}{{defn|}}{{term|actinometer}}{{defn|}}{{term|adiabatic process}}{{defn|Any idealized hypothetical process by which energy is transferred between a thermodynamic system and its surroundings only as work, without a corresponding transfer of heat or mass. In the context of {{gli|meteorology}}, the assumption of adiabatic isolation is often used to explain the processes of {{gli|adiabatic heating}} and {{gli|adiabatic cooling}}, which involve changes in {{gli|temperature}} as a {{gli|air parcel|parcel of air}} is compressed or expanded by interaction with its surroundings.}}{{term|aerobiology}}{{defn|}}{{term|aerography}}{{defn|The production of weather charts.}}{{term|aeronomy}}{{defn|The branch of meteorology that studies the upper regions of the Earth's or other planetary atmospheres, specifically their atmospheric motions, chemical compositions and properties, and interactions with the other parts of the atmosphere and with space.}}{{term|aerosol}}{{defn|A suspension of fine solid particles or liquid droplets in air or another gas. Examples of natural aerosols include {{gli|mist}}, {{gli|cloud|clouds}}, {{gli|fog}}, and dust.}}{{term|ageostrophy}}{{defn|}}{{term|air mass}}{{defn|A volume of air defined by its {{gli|temperature}} and content of water vapor.}}{{term|air-mass thunderstorm}}{{defn|}}{{term|air parcel}}{{defn|In fluid dynamics, any amount of air that remains identifiable throughout its dynamic history while moving with an associated air flow.}}{{term|Alberta clipper}}{{defn|}}{{term|almanac}}{{defn|An annual publication of calendar events.}}{{term|altocumulus castellanus}}{{defn|}}{{term|altocumulus}}{{defn|}}{{term|altostratus}}{{defn|}}{{term|American Meteorological Society (AMS)}}{{defn|}}{{term|anabatic wind}}{{defn|}}{{term|anemometer}}{{defn|A scientific instrument used to measure {{gli|wind speed}}.}}{{term|annular tropical cyclone}}{{defn|}}{{term|anticyclone}}{{defn|}}{{term|anticyclonic rotation}}{{defn|}}{{term|anticyclonic tornado}}{{defn|}}{{term|anticyclogenesis}}{{defn|}}{{term|arcus cloud}}{{defn|}}{{term|Arctic cyclone}}{{defn|}}{{term|Atlantic hurricane}}{{defn|}}{{term|atmosphere}}{{defn|The various layers of gases surrounding the Earth and held in place by gravity. The Earth's atmosphere is the origin of the {{gli|weather}} phenomena studied in {{gli|meteorology}}. Atmospheric composition, {{gli|temperature|temperature}}, and {{gli|atmospheric pressure|pressure}} vary across a series of distinct sublayers including the {{gli|troposphere}} and {{gli|stratosphere}}.}}{{term|atmospheric circulation}}{{defn|}}{{term|atmospheric convection}}{{defn|}}{{term|atmospheric density}}{{defn|}}{{term|atmospheric pressure}}{{defn|}}{{term|atmospheric sciences}}{{ghat|Sometimes called aerology.}}{{defn|The collective of scientific disciplines that studies the Earth's atmosphere and its processes, including the effects other systems have on the atmosphere and those the atmosphere has on other systems. {{gli|meteorology|Meteorology}} and {{gli|climatology}} are sub-disciplines.}}{{term|atmospheric sounding}}{{defn|A measurement of the vertical distribution of physical properties through an {{gli|atmospheric}} column, usually including {{gli|atmospheric pressure|pressure}}, {{gli|temperature}}, {{gli|wind speed}} and {{gli|wind direction|direction}}, moisture content, {{gli|ozone layer|ozone}} concentration, and pollution, among others.}}{{term|atmospheric tide}}{{defn|}}{{term|autumn}}{{defn|}}{{term|avalanche}}{{defn|}}{{term|Aviation Area Forecast (FA or ARFOR)}}{{ghat|Also simply called an area forecast.}}{{defn|A former message product of the U.S. {{gli|National Weather Service}} issued to provide information to pilots and aviation routes about weather conditions across a large regional area within the United States. FAs were issued three times daily, valid for 18 hours and covered an area the size of several states. They were replaced by Graphic Area Forecasts (GFAs) in 2017.}}{{glossaryend}}

B

{{glossary}}{{term|backscatter}}{{defn|The diffuse reflection of waves, particles, or signals back to the same direction from which they originated. Backscattering is the principle underlying all {{gli|weather radar}} systems, which can distinguish radar returns backscattered from target {{gli|aerosol|aerosols}} such as raindrops and snowflakes because the strength of the returns depends largely on the size and reflectivity of the targets.}}{{term|ball lightning}}{{defn|}}{{term|barbs}}{{defn|}}{{term|barograph}}{{defn|A scientific instrument used to measure and record changes in {{gli|atmospheric pressure}} over time.}}{{term|baroclinity}}{{ghat|Also called baroclinicity.}}{{defn|}}{{term|barotropity}}{{ghat|Also called barotropicity.}}{{defn|}}{{term|barometer}}{{defn|A scientific instrument used to measure {{gli|atmospheric pressure}}.}}{{term|Beaufort scale}}{{defn|}}{{term|Bernoulli's principle}}{{defn|}}{{term|Bishop's ring}}{{defn|}}{{term|black ice}}{{defn|}}{{term|blizzard}}{{defn|A severe {{gli|snowstorm}} characterized by strong {{gli|sustained winds}} of at least {{cvt|35|mph|kph}} and typically lasting three hours or more. They can have an immense size, covering hundreds or thousands of square miles, and occur most often in temperate, polar, or mountainous regions during the {{gli|winter}}.}}{{term|blowing dust or sand}}{{defn|}}{{term|blowing snow}}{{defn|}}{{term|bounded weak echo region (BWER)}}{{defn|}}{{term|bow echo}}{{defn|A characteristic radar return from a {{gli|mesoscale convective system}} that is shaped like an archer's bow and usually associated with {{gli|squall line|squall lines}} or lines of convective {{gli|thunderstorm|thunderstorms}}. The distinct bow shape is a result of the focusing of a strong flow at the rear of the system. Especially strong bow echoes may develop into {{gli|derecho|derechos}}.}}{{term|breeze}}{{defn|}}{{term|brightband}}{{defn|}}{{term|Bulk Richardson Number (BRN)}}{{defn|A dimensionless ratio related to the consumption of {{gli|turbulence}} divided by the shear production of turbulence (the generation of kinetic energy caused by {{gli|wind shear}}). It is an approximation of the Gradient Richardson Number.}}{{term|buoyancy}}{{defn|}}{{term|bushfire}}{{defn|}}{{term|Buys Ballot's law}}{{defn|}}{{glossaryend}}

C

{{glossary}}{{term|Canadian Meteorological and Oceanographic Society (CMOS)}}{{defn|The national society of individuals and organizations dedicated to advancing atmospheric and oceanic sciences and related environmental disciplines in Canada, officially constituted in 1967.}}{{term|Canadian Meteorological Centre (CMC)}}{{defn|}}{{term|capping inversion}}{{defn|}}{{term|castellanus}}{{ghat|Also called castellatus.}}{{defn|A {{gli|cloud species}} that displays at least in its upper part {{gli|cumulus|cumuliform}} protuberances resembling the turrets of a castle, giving a crenellated aspect.}}{{term|ceiling}}{{defn|}}{{term|ceiling balloon}}{{defn|}}{{term|ceiling projector}}{{defn|}}{{term|ceilometer}}{{defn|}}{{term|Center for Analysis and Prediction of Storms (CAPS)}}{{defn|}}{{term|chinook wind}}{{defn|}}{{term|cirrocumulus}}{{defn|}}{{term|cirrostratus}}{{defn|}}{{term|cirrus}}{{defn|}}{{term|clear ice}}{{defn|A type of solid {{gli|precipitation}} which forms when relatively large drops of water are supercooled into a dense, transparent coating of {{gli|ice}} without air or other impurities. It is similar to {{gli|glaze}} and {{gli|hard rime}} and, when formed on the ground, is often called {{gli|black ice}}.}}{{term|clear-air turbulence}}{{defn|}}{{term|climate}}{{defn|The statistics of {{gli|weather}} in a given region over long periods of time, measured by assessing long-term patterns of variation in {{gli|temperature}}, {{gli|atmospheric pressure}}, {{gli|humidity}}, {{gli|wind}}, {{gli|precipitation}}, and other {{gli|meteorology|meteorological}} variables. The climate of a particular location is generated by the interactions of the {{gli|atmosphere}}, {{gli|hydrosphere}}, cryosphere, lithosphere, and biosphere and strongly influenced by latitude, altitude, and local topography. Climates are often classified according to the averages or typical ranges of different variables, most commonly temperature and precipitation.}}{{term|climatology}}{{ghat|Also called climate science.}}{{defn|A branch of the {{gli|atmospheric sciences}} that studies {{gli|climate}}, defined as {{gli|weather}} conditions averaged over an extended to indefinite period of time. Climatology incorporates aspects of oceanography, geology, biogeochemistry, and the related field of {{gli|meteorology}} to understand the long-term dynamics of climate-influencing phenomena and to produce climate models which can be used to estimate {{gli|paleoclimatology|past climates}} and predict future climates.}}{{term|cloud}}{{defn|An {{gli|aerosol}} consisting of a visible mass of minute liquid droplets, frozen crystals or other particles suspended in the {{gli|atmosphere}}. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of the saturation of an {{gli|air mass}} when it is cooled to its {{gli|dew point}} or when it gains sufficient moisture (usually in the form of {{gli|water vapor}}) from an adjacent source to raise the dew point to the ambient temperature. There are many different types of clouds, which are classified and named according to their shape and altitude.}}{{term|cloud atlas}}{{defn|}}{{term|cloud base}}{{defn|The lowest altitude of the visible portion of a {{gli|cloud}}.}}{{term|cloud drop effective radius}}{{defn|}}{{term|cloud iridescence}}{{ghat|Also called irisation.}}{{defn|}}{{term|cloud species}}{{defn|Any of a set of 14 Latin terms used to describe the shape and internal structure of {{gli|troposphere|tropospheric}} {{gli|cloud|clouds}}. Cloud species are subdivisions of {{gli|cloud type|cloud genera}} and are themselves further subdivided into {{gli|cloud variety|cloud varieties}}.}}{{term|cloud tag}}{{defn|}}{{term|cloud type}}{{ghat|Also called a cloud genus.}}{{defn|Any of a set of Latin names used to classify and identify {{gli|cloud|clouds}} occurring in the {{gli|troposphere}}, typically by characteristics such as their altitude, shape, and convective activity. A set of 10 or 12 traditional cloud types defined by the {{gli|World Meteorological Organization}} and further subdivided into {{gli|cloud species}} and {{gli|cloud variety|cloud varieties}} is widely used in meteorology. Other classification systems have proposed many additional types.}}{{term|cloudburst}}{{defn|}}{{term|coastal flooding}}{{defn|}}{{term|col}}{{ghat|Also called a saddle point or neutral point.}}{{defn|The point of intersection of a {{gli|trough}} and a {{gli|ridge}} in the pressure pattern of a {{gli|weather map}}. It generally takes the shape of a saddle in which the air pressure is slightly higher than that within the low-pressure regions but still lower than that within the {{gli|anticyclone|anticyclonic zones}}.}}{{term|cold front}}{{defn|}}{{term|cold wave}}{{ghat|Also called a cold spell or cold snap.}}{{defn|}}{{term|cold-core low}}{{defn|}}{{term|Colorado low}}{{defn|A type of {{gli|low-pressure area}} that forms in southeastern Colorado or northeastern New Mexico, in the United States, and then proceeds to move east across the Great Plains, often producing heavy {{gli|snow}} and {{gli|ice}} when occurring in the winter.}}{{term|convection}}{{defn|See {{gli|atmospheric convection}}.}}{{term|convective available potential energy (CAPE)}}{{defn|}}{{term|convective condensation level}}{{defn|}}{{term|convective inhibition (CIN)}}{{defn|}}{{term|convective instability}}{{defn|}}{{term|convective outlooks}}{{defn|}}{{term|convective storm detection}}{{defn|}}{{term|convergence}}{{defn|}}{{term|convergence zone}}{{defn|}}{{term|corona}}{{defn|}}{{term|crepuscular rays}}{{defn|}}{{term|crosswind}}{{defn|}}{{term|Crow instability}}{{ghat|Also called the vortex Crow instability.}}{{defn|An inviscid line-vortex instability most commonly observed in the skies behind large aircraft such as the Boeing 747. It occurs when the wingtip vortices interact with contrails from the engines, producing characteristic visual distortions in the shapes of the contrails.}}{{term|cumulonimbus}}{{defn|}}{{term|cumulus}}{{defn|}}{{term|cumulus congestus}}{{defn|}}{{term|cumulus humilis}}{{defn|}}{{term|cumulus mediocris}}{{defn|}}{{term|cyclone}}{{defn|Any large-scale {{gli|air mass}} characterized by inward spiraling {{gli|wind|winds}} which rotate around a strong center of low {{gli|atmospheric pressure}}. Cyclones can {{gli|cyclogenesis|form}} over land or water, can vary in size from {{gli|mesocyclone|mesocyclones}} such as {{gli|tornado|tornadoes}} to {{gli|synoptic scale meteorology|synoptic-scale}} phenomena such as {{gli|tropical cyclone|tropical cyclones}} and {{gli|polar vortex|polar vortices}}, and may transition between tropical, subtropical, and {{gli|extratropical cyclone|extratropical}} phases.}}{{term|cyclonic rotation}}{{defn|}}{{term|cyclogenesis}}{{defn|The development or strengthening of a {{gli|cyclonic rotation|cyclonic circulation}} in the atmosphere. Cyclogenesis may refer to a number of different processes that occur under a variety of conditions and at a variety of scales, all of which result in the formation of some sort of {{gli|cyclone}}; for instance, {{gli|tornado|tornadoes}} are a type of {{gli|mesocyclone}} whose development may be variously described as cyclogenesis or, more specifically, {{gli|tornadogenesis}}. Contrast {{gli|anticyclogenesis}}.}}{{glossaryend}}

D

{{glossary}}{{term|dark adaptor goggles}}{{ghat|Also called red adaptation goggles.}}{{defn|A type of specialized eyewear used by meteorologists and astronomers for adapting the eyes to the dark prior to an observation made at night, or for aiding with identification of {{gli|cloud|clouds}} during bright sunshine or when there is a glare from snow.}}{{term|dawn}}{{defn|}}{{term|daytime}}{{defn|The period of the day between sunrise and sunset, during which any given point on the Earth experiences natural illumination from especially direct sunlight, known as daylight.}}{{term|dBZ}}{{defn|}}{{term|debris cloud}}{{defn|}}{{term|deformation}}{{defn|The rate of change of shape of a fluid body such as an {{gli|air mass}}. This quantity is very important in the formation of {{gli|weather front|atmospheric fronts}}, in the explanation of {{gli|cloud}} shapes and in the diffusion of materials and properties through the atmosphere.}}{{term|dense fog}}{{defn|}}{{term|depression}}{{defn|See {{gli|low-pressure area}}.}}{{term|derecho}}{{defn|}}{{term|detention basin}}{{defn|}}{{term|detention dam}}{{defn|}}{{term|dew}}{{defn|}}{{term|dew point}}{{defn|(T_d)}}{{term|dew point depression}}{{defn|}}{{term|Diablo wind}}{{defn|}}{{term|diamond dust}}{{defn|}}{{term|divergence}}{{defn|}}{{term|diffluence}}{{defn|}}{{term|diffuse sky radiation}}{{defn|}}{{term|disdrometer}}{{defn|A scientific instrument used to measure the {{gli|raindrop size distribution|size distribution}} and velocity of falling {{gli|hydrometeor|hydrometeors}} such as {{gli|rain|raindrops}}.}}{{term|diurnal temperature variation}}{{defn|}}{{term|Dobson unit}}{{defn|}}{{term|doldrums}}{{defn|}}{{term|Doppler on Wheels (DOW)}}{{defn|}}{{term|Doppler weather radar}}{{defn|}}{{term|downburst}}{{defn|A surface-level {{gli|wind}} system that emanates from an elevated point source and blows radially in all directions upon making contact with the ground. Downbursts are created when areas of significantly {{gli|rain}}-cooled air descend rapidly, and can produce very strong damaging winds. They are often confused with {{gli|tornado|tornadoes}}, though a tornado causes air to move inward and upward whereas a downburst directs it downward and outward. {{gli|microburst|Microbursts}}, {{gli|macroburst|macrobursts}}, and {{gli|heat burst|heat bursts}} are all types of downburst.}}{{term|downdraft}}{{defn|}}{{term|drifting snow}}{{defn|}}{{term|drizzle}}{{defn|}}{{term|drought}}{{ghat|Also called a drouth.}}{{defn|Any prolonged period of below-average {{gli|precipitation}} in a given region that results in shortages in the local water supply, whether of atmospheric, surface water, or ground water. Droughts can last for months or even years, and may be declared after as few as 15 days; annual or seasonal decreases in precipitation, such as {{gli|dry season|dry seasons}} in the tropics, are sometimes called droughts, though a true drought is by definition abnormal or irregular. Drought conditions result from the confluence of a wide variety of climatic factors and may be exacerbated by {{gli|heat wave|hot temperatures}}; in turn, droughts may increase the likelihood of {{gli|wildfire|wildfires}}.}}{{term|dry lightning}}{{defn|{{gli|Lightning}} associated with a {{gli|dry thunderstorm}}.}}{{term|dry line}}{{defn|}}{{term|dry microburst}}{{defn|}}{{term|dry punch}}{{defn|}}{{term|dry season}}{{defn|}}{{term|dry thunderstorm}}{{ghat|Also called a heat storm.}}{{defn|A {{gli|thunderstorm}} that produces {{gli|thunder}} and {{gli|lightning}} but in which most or all of its {{gli|precipitation}} evaporates before reaching the ground. Dry thunderstorms occur necessarily in dry conditions, and their lightning strikes, sometimes referred to as dry lightning, are a major cause of {{gli|wildfire|wildfires}}.}}{{term|DSD}}{{defn|}}{{term|dual polarization weather radar}}{{defn|}}{{term|dusk}}{{defn|}}{{term|dust devil}}{{defn|}}{{term|dust storm}}{{defn|}}{{glossaryend}}

E

{{glossary}}{{term|eddy}}{{defn|}}{{term|Ekman layer}}{{defn|The layer in a fluid in which there is a force balance between the pressure-gradient force, the Coriolis force, and turbulent drag. Ekman layers occur in both the {{gli|atmosphere}} and the ocean.}}{{term|Ekman number}}{{defn|}}{{term|Ekman spiral}}{{defn|}}{{term|Ekman transport}}{{defn|}}{{term|energy-helicity index (EHI)}}{{defn|}}{{term|El Niño}}{{defn|}}{{term|El Niño–Southern Oscillation}}{{defn|}}{{term|emagram}}{{defn|One of four thermodynamic diagrams used to display temperature {{gli|lapse rate}} and {{gli|moisture content}} profiles in the atmosphere. Emagrams have axes of {{gli|temperature}} (T) and {{gli|atmospheric pressure|pressure}} (p). Temperature and {{gli|dew point}} data from {{gli|radiosonde|radiosondes}} are plotted on these diagrams to allow calculations of convective stability or {{gli|convective available potential energy}}.}}{{term|Enhanced Fujita scale (EF scale)}}{{defn|}}{{term|entrainment}}{{defn|}}{{term|Environment and Climate Change Canada}}{{defn|}}{{term|Environmental Modeling Center (EMC)}}{{defn|}}{{term|Environmental Research Laboratories (ERL)}}{{defn|}}{{term|Environmental Science Services Administration (ESSA)}}{{defn|The predecessor agency (1965–1970) to the {{gli|National Oceanic and Atmospheric Administration}} (1970–present).}}{{term|equivalent temperature ()}}{{defn|}}{{term|equivalent potential temperature ()}}{{defn|}}{{term|Eulerian equations}}{{defn|}}{{term|European windstorm}}{{defn|}}{{term|explosive cyclogenesis}}{{defn|}}{{term|extratropical cyclone}}{{defn|}}{{term|extreme weather}}{{defn|Any {{gli|weather}} that is unexpected, unusual, unpredictable, unseasonal, or especially {{gli|severe weather|severe}} (i.e. weather at the extremes of an historical distribution).}}{{term|eye}}{{defn|}}{{glossaryend}}

F

{{glossary}}{{term|fall wind}}{{defn|See {{gli|katabatic wind}}.}}{{term|Fata Morgana}}{{defn|}}{{term|fetch}}{{ghat|Also called fetch length.}}{{defn|The length of water over which a given {{gli|wind}} blows. Fetch length and {{gli|wind speed}} together determine the size of the waves that form on the surface of a body of water; the longer the fetch and the stronger the wind, the more wind energy is imparted to the water surface and the larger the resulting {{gli|sea state}}.}}{{term|field mill}}{{defn|}}{{term|fire whirl}}{{defn|}}{{term|firestorm}}{{defn|}}{{term|flash flood}}{{defn|Any {{gli|flood}} which very rapidly inundates low-lying areas such as washes, rivers, dry lakes, and basins, especially one which recedes again in less than six hours. Flash flooding can be caused by heavy {{gli|rain}} associated with {{gli|severe weather}}, large amounts of meltwater from melting ice or snow, or the sudden collapse of a natural ice or debris dam.}}{{term|flash freezing}}{{defn|}}{{term|flood}}{{defn|An overflow of water which submerges land that is usually dry. Flooding may occur when water bodies such as rivers, lakes, or oceans escape their boundaries by overtopping or puncturing levees, or it may occur when {{gli|precipitation}} accumulates on saturated ground more rapidly than it can either infiltrate or run off.}}{{term|flumen}}{{ghat|Also called a beaver's tail.}}{{defn|}}{{term|fog}}{{defn|A visible {{gli|aerosol}} of minute water droplets or ice crystals that is suspended in the air at or near the Earth's surface. Fog is often considered a type of low-lying {{gli|cloud}} and is heavily influenced by local topography, nearby bodies of water, and {{gli|wind}} conditions.}}{{term|fogbow}}{{defn|}}{{term|föhn wind}}{{ghat|Also spelled foehn wind.}}{{defn|A type of warm, dry, downslope wind that occurs in the {{gli|lee}} of a mountain range.}}{{term|forward-flank downdraft (FFD)}}{{ghat|Also called a front-flank downdraft.}}{{defn|}}{{term|fractus (Fr)}}{{ghat|Often used interchangeably with {{gli|scud}}.}}{{defn|}}{{term|frazil ice}}{{defn|}}{{term|freezing drizzle}}{{defn|}}{{term|freezing fog}}{{defn|}}{{term|freshet}}{{defn|}}{{term|freezing rain}}{{defn|}}{{term|front}}{{defn|A boundary separating two {{gli|air mass|masses of air}} of different {{gli|atmospheric density|densities}} and usually also of different {{gli|temperature|temperatures}} and {{gli|humidity|humidities}}. Weather fronts are the principal cause of meteorological phenomena outside the {{gli|tropics}}, often bringing with them {{gli|cloud|clouds}}, {{gli|precipitation}}, and changes in {{gli|wind}} speed and direction as they move. Types of fronts include {{gli|cold front|cold fronts}}, {{gli|warm front|warm fronts}}, and {{gli|occluded front|occluded fronts}}.}}{{term|frontogenesis}}{{defn|}}{{term|frontolysis}}{{defn|}}{{term|frost}}{{defn|}}{{term|Fujita scale (F scale)}}{{defn|}}{{term|funnel cloud}}{{defn|}}{{glossaryend}}

G

{{glossary}}{{term|gale}}{{defn|A strong surface {{gli|wind}}, typically used as a descriptor in nautical contexts. Gales are variously defined based on their {{gli|wind speed|speed}}; in the modern {{gli|Beaufort scale}}, {{gli|sustained wind|sustained winds}} of {{cvt|28|–|33|knot|kph mph}}, Beaufort number 7, are designated as near gales and those of {{cvt|34|–|47|knot|kph mph}}, spanning Beaufort numbers 8 and 9, as gales.}}{{term|gale warning}}{{defn|}}{{term|gap wind}}{{defn|}}{{term|geopotential height}}{{defn|}}{{term|geostrophic wind}}{{defn|The theoretical {{gli|wind}} that would result from an exact balance between the Coriolis force and the {{gli|pressure gradient}} force (known as geostrophic balance). The true wind almost always differs from the geostrophic wind due to the influence of other forces such as friction from the ground.}}{{term|glaze}}{{defn|}}{{term|GPS meteorology}}{{defn|}}{{term|graupel}}{{ghat|Also called soft hail and snow pellets.}}{{defn|A type of {{gli|precipitation}} that forms when supercooled water droplets are collected and freeze on falling {{gli|snowflake|snowflakes}}, forming balls of {{gli|rime}} {{cvt|2|–|5|mm|in|abbr=on}} in diameter. Graupel is distinct from {{gli|hail}}, small hail, and {{gli|ice pellets}}.}}{{term|Great Salt Lake effect}}{{defn|A {{gli|lake-effect snow}} in lee of the Great Salt Lake}}{{term|grease ice}}{{defn|}}{{term|green flash}}{{defn|}}{{term|Greenwich Mean Time (GMT)}}{{defn|}}{{term|ground blizzard}}{{defn|}}{{term|ground truth}}{{defn|Information, such as local weather conditions, provided by direct observation (i.e. empirical evidence) as opposed to information provided by inference.}}{{term|gust}}{{defn|}}{{term|gust front}}{{defn|}}{{term|gustnado}}{{defn|}}{{glossaryend}}

H

{{glossary}}{{term|haboob}}{{defn|}}{{term|hail}}{{defn|A type of solid {{gli|precipitation}} that consists of balls or irregular lumps of {{gli|ice}} usually {{cvt|5|–|150|mm|in|abbr=on}} in diameter, each of which is called a hailstone. Hail formation requires environments with strong, upward motion of air and low altitudes at which water freezes, which makes it possible within most {{gli|thunderstorm|thunderstorms}}. It is distinct from {{gli|graupel}} and {{gli|sleet}} or {{gli|ice pellets}}.}}{{term|hailstorm}}{{defn|}}{{term|Haines Index}}{{ghat|Also called the Lower Atmosphere Severity Index.}}{{defn|A weather index that measures the potential for dry, unstable air to contribute to the development of large or erratic {{gli|wildfire|wildland fires}}. The index derives from data on the stability and {{gli|moisture|moisture content}} of the lower atmosphere and is calculated over three ranges of {{gli|atmospheric pressure}}.}}{{term|halo}}{{defn|}}{{term|hard rime}}{{defn|}}{{term|Harmattan}}{{defn|}}{{term|haze}}{{defn|}}{{term|hazardous seas warning}}{{defn|}}{{term|hazardous seas watch}}{{defn|}}{{term|heat burst}}{{defn|}}{{term|heat index (HI)}}{{ghat|Also called the apparent temperature, felt air temperature, or humiture.}}{{defn|A meteorological index that posits the apparent temperature perceived by the average human being who is exposed to a given combination of air {{gli|temperature}} and {{gli|relative humidity}} in a shaded area. For example, when the air temperature is {{cvt|32|C|F}} with 70% relative humidity, the heat index is {{cvt|41|C|F}}.}}{{term|heat lightning}}{{defn|}}{{term|heat wave}}{{defn|}}{{term|heavy snow warning}}{{defn|A type of weather warning formerly issued by the U.S. {{gli|National Weather Service}} to alert areas in which a high rate of {{gli|snow|snowfall}} (generally {{cvt|6|in|cm}} or more in 12 hours) was occurring or was {{gli|weather forecasting|forecast}}. The warning was replaced by the {{gli|Winter Storm Warning}} for Heavy Snow beginning with the 2008–09 winter storm season.}}{{term|helicity}}{{defn|}}{{term|high-pressure area}}{{defn|}}{{term|hodograph}}{{ghat|Also called a velocity diagram.}}{{defn|A vectorial visual representation of the movement of a body or a fluid, with the position of any data plotted on it proportional to the velocity of the moving particle. In the context of meteorology, hodographs are used to plot {{gli|wind|winds}} from {{gli|atmospheric sounding|atmospheric soundings}}: for a given vector, {{gli|wind direction}} is indicated by the angle from the center axis and {{gli|wind speed}} by the distance from the center.}}{{term|hook echo}}{{defn|}}{{term|horseshoe vortex}}{{defn|}}{{term|humidity}}{{defn|A measure of the amount of {{gli|water vapor}} present in a {{gli|air parcel|parcel}} of air. By quantifying the saturation of the air with moisture, humidity indicates the likelihood of {{gli|precipitation}}, {{gli|dew}}, or {{gli|fog}} occurring. The amount of water vapor needed to achieve full saturation increases as the air {{gli|temperature}} increases. Three primary measurements of humidity are widely employed in meteorology: {{gli|absolute humidity|absolute}}, {{gli|relative humidity|relative}}, and {{gli|specific humidity|specific}}.}}{{term|humidex}}{{defn|}}{{term|humilis}}{{defn|}}{{term|hurricane}}{{defn|The local name for a {{gli|tropical cyclone}} that occurs in the Atlantic Ocean or northeastern Pacific Ocean.}}{{term|hurricane hunters}}{{defn|}}{{term|huayco}}{{defn|}}{{term|hydrometeor}}{{defn|Any particulate of liquid or solid water within the {{gli|atmosphere}}, encompassing all types of {{gli|precipitation}}, formations due to condensation such as {{gli|cloud|clouds}} and {{gli|haze}}, and particles blown from the Earth's surface by wind such as {{gli|blowing snow}} and {{gli|sea spray}}.}}{{term|hydrometeorology}}{{defn|}}{{term|hydrosphere}}{{defn|The combined mass of all {{gli|ice|solid}}, liquid, and gaseous forms of water found on, beneath, or above the surface of the Earth, including all oceans, lakes, streams, groundwater, atmospheric {{gli|water vapor}}, snow, ice caps, and glaciers.}}{{term|hydrostatic equilibrium}}{{defn|}}{{term|hygrometer}}{{defn|A scientific instrument used to measure {{gli|humidity}}.}}{{term|hypsometer}}{{defn|}}{{term|hygroscopy}}{{defn|}}{{glossaryend}}

I

{{glossary}}{{term|ice}}{{defn|Water frozen into a solid state. Ice is abundant on Earth's surface and in the atmosphere and plays a major role in Earth's water cycle and {{gli|climate}}. Its natural occurrence in weather phenomena takes many forms, including {{gli|snowflake|snowflakes}}, {{gli|hail}}, {{gli|frost}}, {{gli|icicle|icicles}} and {{gli|ice spike|ice spikes}}.}}{{term|iceberg}}{{defn|}}{{term|ice accretion indicator}}{{defn|}}{{term|ice crystals}}{{defn|}}{{term|ice fog}}{{defn|}}{{term|ice pellets}}{{defn|}}{{term|ice spike}}{{defn|}}{{term|ice storm}}{{defn|}}{{term|icicle}}{{defn|A long, slender spike of {{gli|ice}} formed when water dripping or falling from an object freezes.}}{{term|ideal gas law}}{{defn|}}{{term|in situ}}{{defn|}}{{term|incus}}{{defn|}}{{term|Indian summer}}{{defn|}}{{term|inflow}}{{defn|}}{{term|instrument flight rules (IFR)}}{{defn|}}{{term|International Standard Atmosphere}}{{defn|}}{{term|irisation}}{{defn|See {{gli|cloud iridescence}}.}}{{glossaryend}}

J

{{glossary}}{{term|jet stream}}{{defn|A narrow, fast-flowing, meandering air current primarily occurring in the upper part of the {{gli|troposphere}}, at altitudes above {{cvt|9|km|ft}}, and usually flowing from west to east. The Northern and Southern Hemispheres each have a polar jet and a subtropical jet; {{gli|low-level jet|low-level jets}} and other types of jet streams can form under certain conditions.}}{{glossaryend}}

K

{{glossary}}{{term|K-index}}{{defn|}}{{term|

}}{{defn|}}{{term|katabatic wind}}{{ghat|Also called a drainage wind or fall wind, or spelled catabatic wind.}}{{defn|A {{gli|wind}} that carries high-density air from a higher elevation down a slope under the force of gravity, usually at speeds of the order of {{cvt|10|knot|kph}} or less but occasionally at much higher speeds.}}{{term|Kelvin temperature scale}}{{defn|}}{{term|Kelvin–Helmholtz instability}}{{defn|}}{{term|khamsin}}{{defn|}}{{term|kinematics}}{{defn|A branch of classical mechanics that describes the motion of points, bodies, and systems of bodies without considering the forces that caused the motion.}}{{term|Köppen climate classification}}{{defn|}}{{glossaryend}}

L

{{glossary}}{{term|

}}{{defn|}}{{term|Lagrangian equations}}{{defn|}}{{term|La Niña}}{{defn|}}{{term|lake-effect snow}}{{defn|A weather phenomenon produced when a cold {{gli|air mass}} moves across long expanses of warmer lake water, which causes the lowest layers of air to pick up warm {{gli|water vapor}} from the lake, rise through the upper layers, freeze and then precipitate on the lake's {{gli|leeward}} shores. In combination with {{gli|orographic lift}}, the effect produces narrow but very intense bands of {{gli|precipitation}}, especially {{gli|snow}}, which can deposit at very high rates and result in very large amounts of snowfall over a region. The same effect can also occur over bodies of salt water, when it is termed ocean-effect or bay-effect snow.}}{{term|land breeze}}{{defn|}}{{term|landfall}}{{defn|}}{{term|landslide}}{{defn|}}{{term|landspout}}{{defn|A type of {{gli|tornado}} emerging from a parent cloud that does not contain a pre-existing mid-level {{gli|mesocyclone}} or other rotation. Landspouts share a development process and resemblance with {{gli|waterspout|waterspouts}}. They are generally smaller and weaker than {{gli|supercell}} tornadoes and are rarely detected by {{gli|Doppler weather radar}}.}}{{term|lapse rate}}{{defn|}}{{term|lee trough}}{{defn|}}{{term|lee wave}}{{defn|}}{{term|Lemon technique}}{{defn|A method used by meteorologists which focuses on {{gli|updraft|updrafts}} and uses {{gli|Doppler weather radar|weather radar}} to determine the relative strength of {{gli|thunderstorm}} cells in a vertically {{gli|wind shear|sheared}} environment.}}{{term|lenticular cloud}}{{defn|}}{{term|level of free convection (LFC)}}{{defn|}}{{term|Lidar}}{{ghat|Also rendered as LIDAR, LiDAR, or LADAR.}}{{defn|A surveying method that measures the distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor; differences in laser return times and wavelengths can then be used to create digital three-dimensional representations of the target. The name is now used as an acronym of light detection and ranging.}}{{term|lifted condensation level (LCL)}}{{defn|}}{{term|lifted index (LI)}}{{defn|}}{{term|light pillar}}{{defn|}}{{term|lightning}}{{defn|}}{{term|lightning activity level}}{{defn|}}{{term|lightning detection}}{{defn|}}{{term|lightning strike}}{{defn|}}{{term|line echo wave pattern (LEWP)}}{{defn|}}{{term|low-level jet}}{{defn|}}{{term|low-level windshear alert system}}{{defn|}}{{term|low-pressure area (L)}}{{defn|}}{{term|low-topped supercell (LT)}}{{defn|}}{{term|lysimeter}}{{defn|}}{{glossaryend}}

M

{{glossary}}{{term|MAFOR}}{{defn|A North American system used in the transmission of marine {{gli|weather forecasting|weather forecasts}} to compress large amounts of information about meteorological and marine conditions, including visibility, expected future wind speed and direction, the "state of sea", and the period of validity of the forecast, into shorter code for convenience during radio broadcasting. MAFOR is an abbreviation of MArine FORecast.}}{{term|marine cloud brightening}}{{defn|}}{{term|marine stratocumulus}}{{defn|}}{{term|mass flow}}{{defn|The movement of a fluid, such as an {{gli|air mass}}, down a {{gli|pressure gradient|pressure}} or {{gli|temperature gradient}}.}}{{term|mesocyclone}}{{defn|}}{{term|mesohigh}}{{defn|}}{{term|mesolow}}{{defn|}}{{term|mesonet}}{{defn|}}{{term|mesoscale convective complex (MCC)}}{{defn|}}{{term|mesoscale convective discussion (MCD)}}{{defn|}}{{term|mesoscale convective system (MCS)}}{{defn|}}{{term|mesoscale convective vortex (MCV)}}{{defn|}}{{term|mesoscale meteorology}}{{defn|}}{{term|mesosphere}}{{defn|}}{{term|mesovortices}}{{defn|}}{{term|METAR}}{{defn|}}{{term|Météo-France}}{{defn|}}{{term|meteorology}}{{defn|A branch of the {{gli|atmospheric sciences}} which seeks to understand and explain observable {{gli|weather}} events, with a major focus on {{gli|weather forecasting|weather prediction}}. Meteorology uses variables familiar in {{gli|atmospheric chemistry}} and {{gli|atmospheric physics}} to describe and quantify meteorological phenomena, including {{gli|temperature}}, {{gli|atmospheric pressure|pressure}}, {{gli|water vapor}}, {{gli|mass flow}} and how these properties interact and change over time.}}{{term|microburst}}{{defn|}}{{term|micronet}}{{defn|A weather observation network even denser than a {{gli|mesonet}}, such as the Oklahoma City Micronet.}}{{term|microscale meteorology}}{{defn|}}{{term|mini-supercell}}{{defn|A distinct kind of {{gli|supercell}} that is smaller than a typical supercell.}}{{term|mini-tornado}}{{defn|A fallacious term often used in news media to refer to damaging winds accompanying a {{gli|thunderstorm}}, indifferently caused by {{gli|tornado|tornadoes}} or {{gli|microburst}}, on a small area.}}{{term|misocyclone}}{{ghat|Also called a landspout.}}{{defn|}}{{term|misoscale meteorology}}{{defn|}}{{term|mixing ratio}}{{defn|}}{{term|Modified Fujita Scale}}{{defn|An update to the original {{gli|Fujita scale}} from 1971 proposed by Ted Fujita in 1992.}}{{term|moisture convergence}}{{defn|An area where moisture concentrates due to the air flow near the surface.}}{{term|mountain breeze}}{{defn|}}{{term|mountain-gap wind}}{{defn|}}{{term|multicellular thunderstorm}}{{defn|}}{{term|multiple-vortex tornado}}{{defn|}}{{term|moisture}}{{ghat|Also called moisture content or water content.}}{{defn|The presence of liquid, especially water, within a body or substance, often in trace amounts. Moisture in the air in the form of {{gli|water vapor}} underlies the concept of {{gli|humidity}}.}}{{term|monsoon}}{{defn|}}{{term|Morning Glory cloud}}{{defn|}}{{term|mudflow}}{{defn|}}{{term|mudslide}}{{defn|}}{{glossaryend}}

N

{{glossary}}{{term|National Center for Atmospheric Research (NCAR)}}{{defn|}}{{term|National Centers for Environmental Prediction (NCEP)}}{{defn|}}{{term|National Hurricane Center (NHC)}}{{defn|}}{{term|National Oceanic and Atmospheric Administration (NOAA)}}{{defn|}}{{term|National Severe Storms Forecast Center (NSSFC)}}{{defn|A predecessor forecasting center to the {{gli|Storm Prediction Center}} that was located in Kansas City, Missouri.}}{{term|National Severe Storms Laboratory (NSSL)}}{{defn|A {{gli|National Oceanic and Atmospheric Administration|NOAA}} lab in Norman, Oklahoma tasked with researching {{gli|severe weather}}.}}{{term|National Tornado Database}}{{defn|The official NOAA record of all known {{gli|tornado|tornadoes}} within the United States from 1950 to present.}}{{term|National Weather Center (NWC)}}{{defn|}}{{term|National Weather Service (NWS)}}{{defn|}}{{term|National Weather Service Training Center (NWSTC)}}{{defn|}}{{term|needle ice}}{{defn|}}{{term|negative tilt}}{{defn|}}{{term|nephelometer}}{{defn|}}{{term|nephoscope}}{{defn|A scientific instrument used to measure the altitude, direction, and velocity of atmospheric {{gli|cloud|clouds}}.}}{{term|NEXRAD}}{{defn|}}{{term|nimbostratus}}{{defn|}}{{term|noctilucent cloud}}{{defn|}}{{term|nor'easter}}{{ghat|Also called a northeaster.}}{{defn|A macro-scale {{gli|extratropical cyclone}}, especially one which impacts the middle and north Atlantic coasts of North America. The name derives from the direction of the winds that most strongly affect the eastern seaboard between the months of October and March. Such storms are often accompanied by very heavy rain or snow, which can cause severe coastal flooding, and {{gli|Beaufort scale|hurricane-force}} winds.}}{{term|nor'west arch}}{{ghat|Associated with nor'wester.}}{{defn|a variety of föhn cloud found in the South Island of New Zealand when north-westerly winds push cooling moist air over the spine of the Southern Alps mountain range.}}{{term|Novaya Zemlya effect}}{{defn|}}{{term|nowcasting}}{{defn|}}{{term|numerical weather prediction}}{{defn|}}{{glossaryend}}

O

{{glossary}}{{term|occluded front}}{{defn|}}{{term|okta}}{{ghat|Also spelled octa.}}{{defn|A unit of measurement used to describe the amount of {{gli|cloud cover}} at a given location in terms of how many eighths of the {{gli|sky}} are covered in clouds, ranging from 0 oktas (completely clear) to 8 (completely {{gli|overcast}}) or sometimes 9 oktas (indicating that the sky is obstructed from view).}}{{term|omega equation}}{{defn|}}{{term|opacity}}{{defn|}}{{term|orographic cloud}}{{defn|}}{{term|orographic precipitation}}{{defn|}}{{term|overcast}}{{defn|The condition of {{gli|cloud clover}} wherein {{gli|cloud|clouds}} obscure at least 95% of the sky. The type of cloud cover that qualifies as overcast is distinguished from obscuring surface-level phenomena such as {{gli|fog}}.}}{{term|overshooting top}}{{defn|}}{{term|OU-PRIME}}{{defn|}}{{term|outflow}}{{defn|}}{{term|outflow boundary}}{{defn|}}{{term|outflow jet}}{{defn|}}{{term|ozone depletion}}{{defn|}}{{term|ozone layer}}{{defn|}}{{glossaryend}}

P

{{glossary}}{{term|paleoclimatology}}{{defn|}}{{term|pan evaporation}}{{defn|}}{{term|pancake ice}}{{defn|A form of {{gli|ice}} that consists of round, flat pieces of ice with elevated rims, diameters ranging from {{cvt|30|cm|in}} to {{cvt|3|m|ft}}, and thicknesses of up to {{cvt|10|cm|in}}.}}{{term|pannus}}{{ghat|Also called scud; often used interchangeably with {{gli|fractus cloud|fractus}}.}}{{defn|}}{{term|pampero}}{{defn|}}{{term|parhelia}}{{defn|See {{gli|sun dog}}.}}{{term|partial pressure}}{{defn|}}{{term|Particularly Dangerous Situation}}{{defn|}}{{term|pascal (Pa)}}{{defn|The SI derived unit of pressure, defined as one newton per square metre. In meteorology, measurements of {{gli|atmospheric pressure}} are often given in kilopascals (kPa).}}{{term|Pascal's law}}{{defn|}}{{term|Pearson scale}}{{ghat|Also called the Fujita-Pearson scale or F-P-P scale.}}{{defn|A {{gli|tornado}} rating scale developed by Allen Pearson differentiating path length (P) and path width (P) to accompany NOAA {{gli|Fujita scale}} (F) ratings.}}{{term|permafrost}}{{defn|}}{{term|photometeor}}{{defn|Any bright object or other optical phenomenon appearing in the Earth's atmosphere when sunlight or moonlight creates a reflection, refraction, diffraction, or interference under particular circumstances. Common examples of photometeors include {{gli|halo|halos}}, {{gli|rainbow|rainbows}}, {{gli|corona|coronas}}, {{gli|crepuscular rays}}, and {{gli|sun dog|sun dogs}}.}}{{term|Phi_DP (

)}}{{defn|}}{{term|pileus}}{{defn|}}{{term|pilot balloon}}{{defn|}}{{term|pilot report (PIREP)}}{{defn|}}{{term|polar low}}{{defn|}}{{term|polar mesospheric clouds}}{{defn|}}{{term|polar stratospheric cloud}}{{defn|}}{{term|polar vortex}}{{defn|Either of the two very large, persistent, rotating, upper-level {{gli|low-pressure area|low-pressure areas}} suspended in the Earth's atmosphere near the geographic poles. The polar vortices predictably strengthen during their local winter and weaken during their local summer as the temperature contrast between the poles and the Equator changes. When either vortex is weak, high-pressure zones of lower latitudes may push poleward, driving the vortex, {{gli|jet stream}}, and masses of cold, dry polar air into the mid-latitudes, which can cause sudden, dramatic drops in temperature known as {{gli|cold wave|cold waves}}.}}{{term|potential temperature ()}}{{defn|}}{{term|potential vorticity}}{{defn|}}{{term|power flash}}{{defn|A sudden bright light caused when an overhead power line is severed or especially when a transformer explodes. {{gli|Severe weather}} is one of the most common causes.}}{{term|precipitable water}}{{defn|}}{{term|pressure gradient}}{{defn|}}{{term|pressure gradient force (PGF)}}{{defn|}}{{term|pressure system}}{{defn|}}{{term|precipitation}}{{defn|Any product of the condensation of atmospheric {{gli|water vapor}} that falls by gravity, the main forms of which include {{gli|rain}}, {{gli|sleet}}, {{gli|snow}}, {{gli|hail}}, and {{gli|graupel}}. Precipitation occurs when a portion of the atmosphere becomes locally saturated with {{gli|water vapor}} such that the water condenses into liquid or solid droplets and thus "precipitates" out of the atmosphere.}}{{term|precipitation types}}{{defn|}}{{term|prevailing winds}}{{defn|}}{{term|psychrometer}}{{defn|}}{{term|psychrometrics}}{{defn|}}{{term|Pulse-Doppler radar}}{{defn|}}{{term|pulse storm}}{{defn|}}{{term|pyranometer}}{{defn|A type of {{gli|actinometer}} used to measure {{gli|solar irradiance}} on a planar surface and solar flux density in the hemisphere above.}}{{term|pyrgeometer}}{{defn|}}{{term|pyrheliometer}}{{defn|}}{{glossaryend}}

Q

{{glossary}}{{term|Q-vector}}{{defn|}}{{term|quantitative precipitation estimation (QPE)}}{{defn|A method of estimating the approximate amount of {{gli|precipitation}} that has fallen at a location or across a region.}}{{term|quantitative precipitation forecast (QPF)}}{{defn|The expected amount of melted {{gli|precipitation}} accumulated over a specified time period within a specified area.}}{{term|quasi-geostrophic equations}}{{defn|}}{{term|quasi-linear convective system (QLCS)}}{{defn|}}{{term|quasistatic approximation}}{{defn|}}{{glossaryend}}

R

{{glossary}}{{term|radiation fog}}{{defn|}}{{term|radiosonde}}{{defn|A battery-powered scientific instrument released into the {{gli|atmosphere}}, usually by a {{gli|weather balloon}}, which measures various {{gli|atmospheric sounding|atmospheric parameters}} and transmits them by radio telemetry to a ground receiver. Radiosondes are essential sources of meteorological data, and hundreds are launched all over the world everyday.}}{{term|radius of maximum wind (RMW)}}{{defn|}}{{term|rain}}{{defn|A type of {{gli|precipitation}} that occurs when liquid water in the form of droplets condenses from atmospheric {{gli|water vapor}}, becoming heavy enough to fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth.}}{{term|rainbow}}{{defn|}}{{term|raindrop size distribution}}{{defn|}}{{term|rain and snow mixed}}{{defn|}}{{term|rain gauge}}{{defn|}}{{term|rain of animals}}{{defn|}}{{term|rain shadow}}{{defn|}}{{term|rain showers}}{{ghat|Often simply called showers.}}{{defn|Short, intense periods of {{gli|rain|rainfall}}, especially when occurring in widely scattered locations.}}{{term|Rankine vortex}}{{defn|}}{{term|rapid intensification}}{{defn|}}{{term|rear flank downdraft (RFD)}}{{defn|}}{{term|relative humidity}}{{defn|}}{{term|remote sensing}}{{defn|The acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation. In meteorology, satellite- or aircraft-based sensor technologies are widely used to detect and classify objects on the surface or within the atmosphere or oceans based on propagated electromagnetic signals.}}{{term|Rho_hv (

)}}{{defn|}}{{term|ridge}}{{defn|}}{{term|rime}}{{defn|A coating of {{gli|ice}} on the surface of an object. See {{gli|hard rime}} and {{gli|soft rime}}.}}{{term|rogue wave}}{{defn|}}{{term|roll cloud}}{{defn|}}{{term|Rossby number}}{{defn|}}{{term|Rossby wave}}{{defn|}}{{term|rotation}}{{defn|See {{gli|cyclonic rotation}}.}}{{glossaryend}}

S

{{glossary}}{{term|sandstorm}}{{defn|See {{gli|dust storm}}.}}{{term|sastrugi}}{{ghat|(sing.) sastruga; also spelled zastrugi}}{{defn|Sharp, irregular grooves or ridges formed on a {{gli|snow}} surface by wind erosion, saltation of snow particles, and deposition, usually parallel to the prevailing winds. They are often found in the polar regions and in large, open areas such as frozen lakes in cold temperate regions.}}{{term|satellite tornado}}{{defn|}}{{term|scud}}{{defn|See {{gli|pannus}}.}}{{term|sea breeze}}{{defn|}}{{term|sea spray}}{{defn|}}{{term|sea state}}{{defn|}}{{term|season}}{{defn|Any division of the year marked by changes in {{gli|weather}}, ecology and the duration of daylight. Seasons result from the Earth's orbit around the Sun and its axial tilt relative to the ecliptic plane. In temperate and polar regions, four calendar-based seasons – {{gli|spring}}, {{gli|summer}}, {{gli|autumn}} and {{gli|winter}} – are generally marked by significant changes in the intensity of sunlight that reaches the Earth's surface; these changes become less dramatic as one approaches the Equator, and so many tropical regions have only two or three seasons, such as a {{gli|wet season}} and a {{gli|dry season}}. In certain parts of the world, the term is also used to capture the timing of important ecological events, such as {{gli|hurricane season|hurricane seasons}}, flood seasons and {{gli|wildfire}} seasons.}}{{term|severe thunderstorm}}{{defn|}}{{term|severe weather}}{{defn|Any dangerous meteorological phenomena with the potential to cause damage on the ground surface, serious social disruption, or loss of human life. There are many types of severe weather, including strong {{gli|wind|winds}}, excessive {{gli|precipitation}}, {{gli|thunderstorm|thunderstorms}}, {{gli|tornado|tornadoes}}, {{gli|tropical cyclone|tropical cyclones}}, {{gli|blizzard|blizzards}}, and {{gli|wildfire|wildfires}}. Some severe weather may be more or less typical of a given region during a given {{gli|season}}; other phenomena may be {{gli|extreme weather|atypical or unpredictable}}.}}{{term|shelf cloud}}{{defn|}}{{term|shortwave trough}}{{defn|}}{{term|SIGMET}}{{defn|}}{{term|simoom}}{{defn|}}{{term|single cell thunderstorm}}{{defn|}}{{term|sirocco}}{{defn|}}{{term|skew-T log-P diagram}}{{defn|}}{{term|Skywarn}}{{ghat|Sometimes stylized as SKYWARN.}}{{defn|The storm-spotting program of the U.S. {{gli|National Weather Service}}. Skywarn organizations have also been formed in Europe and Canada.}}{{term|skipping tornado}}{{defn|}}{{term|sleet}}{{defn|}}{{term|slush}}{{defn|}}{{term|snow}}{{defn|A type of solid {{gli|precipitation}} in the form of {{gli|ice}} crystals which precipitate from the atmosphere and subsequently undergo changes on the Earth's surface. Snow occurs when {{gli|snowflake|snowflakes}} nucleate around particles in the atmosphere by attracting supercooled water droplets, which freeze in hexagonal-shaped crystals; upon reaching the ground it may then accumulate into snowpack or {{gli|snowdrift|snowdrifts}} and, over time, metamorphose by sintering, sublimation, and freeze-thaw mechanisms. Unless the local climate is cold enough to maintain persistent snow cover on the ground, snow typically melts seasonally.}}{{term|snow gauge}}{{defn|}}{{term|snow grains}}{{defn|}}{{term|snow roller}}{{defn|}}{{term|snowbelt}}{{defn|}}{{term|snowdrift}}{{defn|}}{{term|snowflake}}{{defn|}}{{term|snowsquall}}{{defn|}}{{term|snowstorm}}{{ghat|Often used interchangeably with {{gli|winter storm}}.}}{{defn|A type of {{gli|winter storm}} accompanied particularly by heavy precipitation in the form of {{gli|snow}}. Very large snowstorms with strong winds and meeting certain other criteria are called {{gli|blizzard|blizzards}}.}}{{term|SODAR}}{{defn|}}{{term|solar irradiance}}{{defn|}}{{term|solarimeter}}{{defn|}}{{term|sounding}}{{defn|See {{gli|atmospheric sounding}}.}}{{term|sounding rocket}}{{defn|}}{{term|specific humidity}}{{defn|}}{{term|spindrift}}{{ghat|Also called spoondrift.}}{{defn|{{gli|sea spray|Sea spray}} blown from cresting waves during a {{gli|gale}}. This spray "drifts" in the direction of the gale and is distinct enough that it is sometimes used to judge {{gli|wind speed}} at sea.}}{{term|spring}}{{defn|}}{{term|sprite}}{{defn|}}{{term|squall line}}{{defn|}}{{term|St. Elmo's fire}}{{defn|}}{{term|standard atmosphere}}{{defn|}}{{term|station model}}{{defn|}}{{term|stationary front}}{{defn|}}{{term|steam devil}}{{defn|}}{{term|Stevenson screen}}{{defn|}}{{term|storm}}{{defn|Any disturbed state of an environment or {{gli|atmosphere}} especially affecting the ground surface and strongly implying {{gli|severe weather}}. Storms are characterized by significant disruptions to normal atmospheric conditions, which can result in strong {{gli|wind}}, heavy {{gli|precipitation}}, {{gli|thunder}} and {{gli|lightning}} (as with a {{gli|thunderstorm}}), among other phenomena. They are created when a center of {{gli|low-pressure area|low pressure}} develops within a system of {{gli|high-pressure area|high pressure}} surrounding it.}}{{term|storm cell}}{{defn|An {{gli|air mass}} which contains up and down {{gli|vertical draft|drafts}} in convective loops and which moves and reacts as a single entity. It functions as the smallest unit of a {{gli|storm}}-producing weather system.}}{{term|storm chasing}}{{defn|}}{{term|Storm Data and Unusual Weather Phenomena (SD)}}{{ghat|Also simply abbreviated to Storm Data.}}{{defn|A National Climatic Data Center (NCDC) publication beginning in 1959 which details quality-controlled tornado and other severe weather summaries as the official NOAA record of such events.}}{{term|storm shelter}}{{defn|}}{{term|storm spotting}}{{defn|}}{{term|storm surge}}{{defn|}}{{term|Storm Prediction Center (SPC)}}{{defn|}}{{term|Storm Track}}{{defn|}}{{term|straight-line wind}}{{ghat|Also called a plough wind, thundergust, or hurricane of the prairie.}}{{defn|Any very strong and potentially damaging {{gli|wind}} that lacks the rotational damage pattern associated with the winds of a {{gli|tornado}} and hence is said to blow in a "straight line". Straight-line winds commonly accompany the {{gli|outflow boundary|gust front}} of a {{gli|thunderstorm}} or originate with a {{gli|downburst}} and may {{gli|wind gust|gust}} as high as {{cvt|130|mph|kph}}.}}{{term|stratocumulus}}{{defn|}}{{term|stratosphere}}{{defn|}}{{term|stratus}}{{defn|}}{{term|summer}}{{defn|}}{{term|Stüve diagram}}{{defn|}}{{term|sun dog}}{{defn|}}{{term|sunshine recorder}}{{defn|}}{{term|sunshower}}{{defn|A meteorological phenomenon in which {{gli|rain}} falls while the sun is shining.}}{{term|supercell}}{{defn|}}{{term|subtropical cyclone}}{{defn|}}{{term|surface weather analysis}}{{defn|}}{{term|surface weather observation}}{{defn|}}{{term|sustained wind}}{{defn|}}{{term|synoptic scale meteorology}}{{defn|}}{{glossaryend}}

T

{{glossary}}{{term|tail cloud}}{{ghat|Also called a cauda.}}{{defn|A ragged band of {{gli|cloud}} and/or {{gli|fractus}} extending from a {{gli|wall cloud}} toward the precipitation core.}}{{term|temperature}}{{defn|A physical quantity expressing the thermal motion of a substance, such as a mass of air in the {{gli|atmosphere}}, and proportional to the average kinetic energy of the random microscopic motions of the substance's constituent particles. Temperature is measured with a {{gli|thermometer}} calibrated in one or more temperature scales: the Kelvin scale is the standard used in scientific contexts, but the Celsius and Fahrenheit scales are more commonly used in everyday contexts and for {{gli|weather forecasting}}.}}{{term|temperature gradient}}{{defn|}}{{term|temperature inversion}}{{defn|}}{{term|tephigram}}{{defn|}}{{term|terminal aerodrome forecast (TAF)}}{{defn|}}{{term|Terminal Doppler Weather Radar (TDWR)}}{{defn|}}{{term|thermal}}{{ghat|Also called a thermal column.}}{{defn|A column of rising air in the lower altitudes of the Earth's atmosphere. It is a form of atmospheric {{gli|updraft}} created by the uneven heating of the Earth's surface by solar radiation, and an example of {{gli|atmospheric convection}}.}}{{term|thermal wind}}{{defn|}}{{term|thermo-hygrograph}}{{defn|}}{{term|thermodynamics}}{{defn|}}{{term|thermodynamic diagrams}}{{defn|}}{{term|thermometer}}{{defn|An instrument used to measure {{gli|temperature}} or a {{gli|temperature gradient}}.}}{{term|thermosphere}}{{defn|}}{{term|thunder}}{{defn|}}{{term|thundershower}}{{defn|A relatively weak {{gli|thunderstorm}}.}}{{term|thundersnow}}{{defn|}}{{term|thunderstorm}}{{ghat|Also called an electrical storm or lightning storm.}}{{defn|A {{gli|storm}} characterized by the presence of {{gli|lightning}} and its acoustic effect on the Earth's atmosphere, known as {{gli|thunder}}. Thunderstorms result from the rapid upward movement of warm, moist air, often along a {{gli|front}}. They can develop in any geographic location but are most common in the mid-latitudes. They are usually accompanied by strong {{gli|wind|winds}} and heavy {{gli|rain}}; especially strong or {{gli|severe thunderstorm|severe thunderstorms}} can produce some of the most dangerous weather phenomena, including large {{gli|hail}}, {{gli|downburst|downbursts}}, and {{gli|tornado|tornadoes}}.}}{{term|thunderstorm asthma}}{{defn|}}{{term|tilted updraft}}{{defn|}}{{term|tornado}}{{ghat|Also called a twister, whirlwind, or cyclone.}}{{defn|A rapidly rotating column of air that is in contact with both a parent {{gli|cloud}} and the surface of the Earth. Tornadoes come in many shapes and sizes, and they are often visible in the form of a {{gli|funnel cloud|condensed funnel}} originating from the base of a {{gli|cumulonimbus}} cloud, usually during a {{gli|thunderstorm}}, with a cloud of rotating dust and debris beneath it. The most extreme tornadoes can achieve wind speeds of more than {{cvt|300|mph|kph}}, span more than {{cvt|2|mi|km}} in diameter, and stay on the ground for dozens of miles (more than 100 km) before dissipating.}}{{term|Tornado Alley}}{{defn|}}{{term|tornado climatology}}{{defn|}}{{term|tornado debris signature (TDS)}}{{defn|}}{{term|tornado emergency}}{{defn|}}{{term|tornado family}}{{defn|}}{{term|tornadogenesis}}{{defn|}}{{term|tornado outbreak}}{{defn|}}{{term|tornado outbreak sequence}}{{defn|}}{{term|tornado preparedness}}{{defn|}}{{term|tornado vortex signature (TVS)}}{{defn|}}{{term|tornado warning}}{{defn|}}{{term|tornado watch}}{{defn|}}{{term|Tornado and Storm Research Organisation (TORRO)}}{{defn|}}{{term|TORRO scale}}{{defn|}}{{term|Totable Tornado Observatory (TOTO)}}{{defn|}}{{term|training}}{{defn|}}{{term|tropical cyclone}}{{ghat|Variously called a {{gli|hurricane}}, {{gli|typhoon}}, {{gli|tropical storm}}, cyclonic storm, or simply cyclone.}}{{defn|A very large, {{gli|cyclone|rapidly rotating}} {{gli|storm}} system characterized by a {{gli|low-pressure area|low-pressure}} {{gli|eye|center}} surrounded by a closed low-level {{gli|atmospheric circulation}}, strong {{gli|wind|winds}}, and continuous spiral bands of {{gli|thunderstorm|thunderstorms}} that produce heavy {{gli|rain}}. Tropical cyclones {{gli|tropical cyclogenesis|develop}} almost exclusively over and derive their strength from warm {{gli|tropics|tropical}} seas. The strongest systems can last for more than a week, span more than {{cvt|1000|mi|km}} in diameter, and cause significant damage to coastal regions with powerful winds, {{gli|storm surge|storm surges}}, and concentrated precipitation that leads to {{gli|flood|flooding}}. Depending on its location and strength, a tropical cyclone may be referred to by different names and categorized within a variety of classes.}}{{term|tropical cyclone scales}}{{defn|}}{{term|tropical cyclogenesis}}{{defn|}}{{term|tropical depression}}{{defn|}}{{term|tropical disturbance}}{{defn|}}{{term|tropical storm}}{{defn|}}{{term|tropical wave}}{{defn|}}{{term|tropics}}{{defn|}}{{term|tropopause}}{{defn|}}{{term|troposphere}}{{defn|The lowest layer of the Earth's {{gli|atmosphere}}, within which nearly all {{gli|weather}} phenomena occur. The troposphere contains approximately 75% of the atmosphere's total mass and 99% of its {{gli|water vapor}} and {{gli|aerosol|aerosols}}. The average height of the troposphere above the Earth's surface varies between {{cvt|6|and|18|km|mi}} depending on latitude.}}{{term|trough}}{{defn|}}{{term|trowal}}{{defn|}}{{term|tsunami}}{{defn|}}{{term|turbulence}}{{defn|}}{{term|twilight}}{{defn|no=1|The indirect illumination of the lower atmosphere caused by the scattering of sunlight when the Sun itself is not directly visible because it is below the horizon.}}{{defn|no=2|The time period during which such illumination occurs, either between astronomical {{gli|dawn}} and sunrise or between sunset and astronomical {{gli|dusk}}.}}{{term|TWISTEX}}{{defn|An acronym for Tactical Weather-Instrumented Sampling in/near Tornadoes EXperiment.}}{{term|typhoon}}{{defn|The local name for a {{gli|tropical cyclone}} that occurs in the northwestern Pacific Ocean, between 180° and 100°E in the Northern Hemisphere.}}{{glossaryend}}

U

{{glossary}}{{term|unstable airmass}}{{defn|}}{{term|updraft}}{{ghat|Also called a vertical draft.}}{{defn|}}{{term|upper-air chart}}{{defn|}}{{term|upper-air sounding}}{{defn|}}{{term|upper-air trough}}{{defn|}}{{term|upper-level low}}{{defn|}}{{term|upper-level outflow}}{{defn|}}{{term|upslope fog}}{{defn|}}{{term|urban heat island}}{{defn|}}{{term|US Standard Atmosphere}}{{defn|}}{{term|University Corporation for Atmospheric Research (UCAR)}}{{defn|}}{{term|UTC}}{{defn|}}{{glossaryend}}

V

{{glossary}}{{term|valley breeze}}{{defn|}}{{term|valley exit jet}}{{defn|}}{{term|vertical draft}}{{defn|See {{gli|updraft}}.}}{{term|vertically integrated liquid (VIL)}}{{defn|}}{{term|vertical wind shear}}{{defn|}}{{term|virga}}{{defn|}}{{term|virtual temperature}}{{defn|}}{{term|visibility}}{{defn|}}{{term|visual flight rules (VFR)}}{{defn|A set of regulations under which a pilot operates an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going, as opposed to {{gli|instrument flight rules}}, under which operation of the aircraft primarily occurs through referencing the onboard instruments rather than through visual reference to the ground and environs.}}{{term|Von Kármán constant}}{{defn|}}{{term|Von Kármán vortex street}}{{defn|}}{{term|Von Kármán wind turbulence model}}{{defn|}}{{term|vortex}}{{ghat|(pl.) vortices or vortexes}}{{defn|A region within a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices are a major component of {{gli|turbulence}} and may be observed in many types of meteorological phenomena, including the winds surrounding a {{gli|tropical cyclone}}, {{gli|tornado}} or {{gli|dust devil}}.}}{{term|vorticity}}{{defn|}}{{glossaryend}}

W

{{glossary}}{{term|wall cloud}}{{ghat|Also called murus or a pedestal cloud.}}{{defn|A large, localized, persistent, and often abrupt lowering of {{gli|cloud}} that develops beneath the surrounding base of a {{gli|cumulonimbus}} cloud and from which {{gli|tornado|tornadoes}} sometimes form.}}{{term|warm front}}{{defn|}}{{term|Warning Decision Training Branch (WDTB)}}{{defn|}}{{term|water vapor}}{{defn|Water in its gaseous state. Water vapor is ubiquitous in the atmosphere, being continuously generated by evaporation and removed by condensation, and plays a major role in numerous meteorological processes.}}{{term|waterspout}}{{defn|}}{{term|weak echo region (WER)}}{{defn|}}{{term|weather}}{{defn|The state of the {{gli|atmosphere}} at a given time and location. Weather is driven by a diverse set of naturally occurring phenomena, especially {{gli|atmospheric pressure|air pressure}}, {{gli|temperature}}, and {{gli|moisture}} differences between one place and another, most of which occur in the {{gli|troposphere}}.}}{{term|weather balloon}}{{defn|}}{{term|weather bomb}}{{defn|}}{{term|weather forecasting}}{{defn|The application of science and technology to predict the conditions of the {{gli|atmosphere}} at a given time and location. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere at a given place and then using {{gli|meteorology}} to project how the atmosphere will change. Forecasting is important to a wide variety of human activities, including business, agriculture, transportation, recreation and general health and safety, because it can be used to protect life and property.}}{{term|weather front}}{{defn|See {{gli|front}}.}}{{term|weather map}}{{defn|A map which displays various meteorological features across a particular area for a particular point or range of time. Weather maps often use symbols such as {{gli|station model|station models}} to conveniently present complicated meteorological data. They are used for both research and {{gli|weather forecasting}} purposes.}}{{term|weather modification}}{{defn|}}{{term|Weather Prediction Center (WPC)}}{{defn|}}{{term|Weather Surveillance Radar (WSR)}}{{defn|no=1|In the United States, WSR-1, WSR-57, WSR-74, and {{gli|NEXRAD|WSR-88D}}.}}{{defn|no=2|In Canada, the Canadian weather radar network (WKR and CWMN).}}{{term|weather reconnaissance}}{{defn|}}{{term|weather satellite}}{{defn|}}{{term|weather spotting}}{{defn|The act of observing {{gli|weather}}, often on the ground, for the purpose of reporting to a larger group or organization, such as the U.S. {{gli|National Weather Service}}.}}{{term|weather station}}{{defn|}}{{term|weather vane}}{{defn|}}{{term|Weatherwise}}{{defn|A photographically adorned general interest weather magazine that frequently publishes articles on {{gli|tornado|tornadoes}} and other {{gli|severe weather}}.}}{{term|wet-bulb temperature}}{{defn|}}{{term|wet-bulb globe temperature}}{{defn|}}{{term|wet season}}{{defn|}}{{term|whirlwind}}{{defn|}}{{term|wildfire}}{{defn|}}{{term|willy-willy}}{{defn|See {{gli|dust devil}}.}}{{term|wind}}{{defn|The bulk movement of air within the Earth's {{gli|atmosphere}}. Wind occurs on a wide range of scales, from very strong {{gli|thunderstorm}} flows lasting tens of minutes to milder local {{gli|breeze|breezes}} lasting a few hours to global {{gli|atmospheric circulation|atmospheric circulations}} caused by the differential heating of the Equator and the poles and the Earth's rotation. Winds are often referred to by their strength and {{gli|wind direction|direction}}; the many types of wind are classified according to their spatial scale, their {{gli|wind speed|speed}}, the types of forces that cause them, the regions in which they occur, and their effects.}}{{term|wind chill}}{{defn|}}{{term|wind direction}}{{defn|The direction from which a {{gli|wind}} originates; e.g. a northerly wind blows from the north to the south. Wind direction is usually reported using cardinal directions or in azimuth degrees measured clockwise from due north. Instruments such as {{gli|windsock|windsocks}}, {{gli|weather vane|weather vanes}}, and {{gli|anemometer|anemometers}} are commonly used to indicate wind direction.}}{{term|wind gradient}}{{defn|}}{{term|wind gust}}{{defn|}}{{term|wind profiler}}{{defn|}}{{term|wind shear}}{{ghat|Sometimes used interchangeably with {{gli|wind gradient}}.}}{{defn|Any difference in {{gli|wind speed}} and/or {{gli|wind direction|direction}} over a relatively short distance in the {{gli|atmosphere}}. Atmospheric wind shear is normally described as either {{gli|vertical wind shear|vertical}} or {{gli|horizontal wind shear|horizontal}}.}}{{term|wind speed}}{{defn|}}{{term|windstorm}}{{defn|}}{{term|windsock}}{{defn|}}{{term|winter}}{{defn|}}{{term|winter storm}}{{ghat|Often used interchangeably with {{gli|snowstorm}}.}}{{defn|no=1|Any {{gli|storm}} which occurs during the local {{gli|winter}}.}}{{defn|no=2|Any meteorological event in which varieties of {{gli|precipitation}} which can only occur at low temperatures are formed, such as {{gli|snow}}, {{gli|sleet}}, or {{gli|freezing rain}}. Such events are not necessarily restricted to the winter season but may occur in late {{gli|autumn}} or early {{gli|spring}}, or very rarely in the {{gli|summer}}, as well.}}{{term|winter waterspout}}{{ghat|Also called a snowspout.}}{{defn|}}{{term|World Meteorological Organization (WMO)}}{{defn|}}{{glossaryend}}

X

Y

Z

{{glossary}}{{term|Z-R relation}}{{defn|}}{{term|Zdr}}{{defn|}}{{term|zastrugi}}{{defn|See {{gli|sastrugi}}.}}{{term|zephyr}}{{defn|}}{{term|zonal flow}}{{defn|}}{{term|Zonda wind}}{{defn|}}{{term|zud}}{{ghat|Also spelled dzud.}}{{defn|}}{{glossaryend}}

References

External links

{{cite web|url=http://glossary.ametsoc.org/wiki/Main_Page|title=AMS Glossary|publisher=American Meteorological Society}}

1 : Glossaries of meteorology

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