Meteopedia — Weather glossary
Weather encyclopedia with 172 terms
Browse detailed definitions of atmospheric phenomena, cloud types, measurement instruments, regional winds, meteorological scales, climatology and more.
A
Ábrego
A warm, moist southwesterly wind on the Iberian Peninsula, associated with rainfall on the Atlantic slope.
VientoAcid rain
Precipitation with pH below 5.6 caused by dissolution of atmospheric pollutants such as sulphur dioxide and nitrogen oxides.
PrecipitaciónAdvection
Horizontal transport of heat, moisture, or other atmospheric properties by the wind, a key process in weather evolution.
GeneralAdvection fog
Fog that forms when warm, moist air moves over a colder surface.
Fenómenos atmosféricosAir mass
Extensive volume of air with uniform temperature and humidity characteristics acquired in its source region.
GeneralAlbedo
Fraction of solar radiation reflected by a surface, expressed from 0 (absorbs all) to 1 (reflects all).
ClimatologíaAltocumulus
Mid-level cloud in the form of white and grey patches, rolls or flakes, often in regular rows.
NubesAltostratus
Mid-level grey cloud that covers the sky like a veil, letting the sun show through diffusely.
NubesAMOC
Atlantic Meridional Overturning Circulation: a system of currents that transports warm water northward and cold water southward in the Atlantic Ocean.
ClimatologíaAnabatic wind
Wind that ascends mountain slopes heated by the sun during the day.
VientoAnemometer
Instrument that measures wind speed, typically using spinning cups or ultrasonic sensors.
InstrumentosAnticyclone
High-pressure system where descending air produces stable weather and clear skies.
Fenómenos atmosféricosArctic amplification
Phenomenon whereby the Arctic warms 2-4 times faster than the global average, with profound consequences for atmospheric circulation.
ClimatologíaArcus cloud
Accessory cloud in the form of a horizontal arch or roll appearing at the leading edge of intense storms.
NubesAridity index
Numerical indicator classifying climatic zones according to the ratio between precipitation and potential evapotranspiration.
ClimatologíaAsperitas
Cloud type officially recognised by the WMO in 2017, with a chaotic, wave-like underside resembling a rough sea viewed from below.
NubesAtmospheric corona
A luminous ring of colours appearing around the sun or moon, caused by diffraction of light by water droplets or ice crystals.
Óptica atmosféricaAtmospheric pressure
Force exerted by the weight of the air column on the Earth's surface, measured in hectopascals (hPa).
GeneralAtmospheric sounding
A vertical profile of the atmosphere obtained by radiosonde, showing temperature, humidity, and wind at different altitudes.
InstrumentosAurora borealis
Luminous phenomenon in the night sky caused by the interaction of solar particles with Earth's magnetosphere, visible at high latitudes.
Fenómenos atmosféricosAutomatic weather station
Facility that measures and transmits meteorological data autonomously, without human intervention, forming the core observation network.
InstrumentosB
Barometer
Instrument that measures atmospheric pressure, essential for weather forecasting.
InstrumentosBeaufort scale
Empirical scale from 0 to 12 that classifies wind intensity by its observable effects.
Escalas y medidasBelt of Venus
Pink band visible on the horizon opposite the sun during twilight, caused by backscattering of sunlight in the atmosphere.
Óptica atmosféricaBlack frost
A frost that destroys plant tissue without leaving visible ice deposits, caused by very dry air at sub-zero temperatures.
TemperaturaBlizzard
Snowstorm with strong winds that drastically reduces visibility and produces significant accumulations.
Fenómenos atmosféricosBora
Violent, cold, gusty katabatic wind descending from the Balkan interior plateaux toward the Adriatic Sea coast.
VientoBrocken spectre
Optical phenomenon in which the observer's shadow is projected onto fog or low clouds, surrounded by a rainbow-coloured halo.
Óptica atmosféricaC
Ceilometer
Instrument measuring cloud base height using laser pulses, essential at airports and weather stations.
InstrumentosChinook
Warm, dry wind descending the eastern slopes of the Rocky Mountains in North America, capable of raising temperatures by tens of degrees in hours.
VientoCierzo
Cold, dry northwesterly wind channelled through Spain's Ebro Valley.
VientoCircumzenithal arc
A brightly coloured arc appearing in the sky above the sun, formed by refraction through ice crystals.
Óptica atmosféricaCirrocumulus
High cloud formed by small regular white tufts, giving a "mackerel sky" appearance.
NubesCirrus
High cloud (6,000–12,000 m), thin and fibrous, composed entirely of ice crystals.
NubesClear-air turbulence
Atmospheric turbulence occurring in clear skies with no visual cues, the principal invisible hazard for aviation.
Fenómenos atmosféricosClimate change
Significant, lasting change in global climate patterns, currently driven by greenhouse gas emissions.
ClimatologíaCold front
Frontal boundary where cold air pushes under and lifts warm air, producing storms and a sharp temperature drop.
Fenómenos atmosféricosCondensation
The process by which water vapour changes to liquid state upon cooling below its saturation point.
PrecipitaciónContrail
An artificial line-shaped cloud created by aircraft exhaust gases at high altitude.
NubesConvective precipitation
Precipitation generated by rapid ascent of warm, moist air in convective currents, typically intense, localised, and short-lived.
PrecipitaciónCumuliform cloud
A type of vertically developing cloud with a puffy appearance and flat base, formed by convective updrafts.
NubesCumulonimbus
Towering cloud of enormous vertical development, associated with thunderstorms, lightning, hail, and heavy rain.
NubesCumulonimbus incus
Mature stage of the cumulonimbus with the characteristic anvil top, indicative of severe storms with hail, lightning, and strong winds.
NubesCumulus
Vertically developing cloud with a flat base and cauliflower-shaped top, typical of fair weather or storm development.
NubesD
DANA
Cut-off low: a cold air mass at upper levels detached from the jet stream, capable of triggering torrential rain.
Fenómenos atmosféricosDepression
Low-pressure system associated with unstable weather, clouds, and precipitation.
Fenómenos atmosféricosDerecho
Line of storms that produces a swath of destructive straight-line winds over hundreds of kilometres.
Ciclones y tormentas severasDew
Water droplets that form on cold surfaces when the temperature drops to the dew point.
PrecipitaciónDew point
Temperature at which air must cool for water vapour to condense into droplets (100 % relative humidity).
TemperaturaDiurnal temperature range
Difference between maximum and minimum temperature over a given period (day, month, or year).
TemperaturaDownburst
A concentrated downdraft that produces destructive winds upon impacting the ground, with a damage area exceeding 4 km.
Ciclones y tormentas severasDrizzle
Uniform precipitation of very fine droplets (< 0.5 mm diameter) that fall slowly.
PrecipitaciónDrop in cold air
Popular Spanish term for torrential rain events in the Mediterranean, associated with upper-level cold air over warm seas.
Fenómenos atmosféricosDrought
A prolonged period of below-normal precipitation causing water scarcity and affecting ecosystems, agriculture, and populations.
ClimatologíaDry haze
Suspension of mineral dust particles in the atmosphere reducing visibility without significant moisture, distinct from mist or fog.
Fenómenos atmosféricosDry line
A boundary between a dry air mass and a moist air mass at the surface, frequently associated with severe thunderstorm formation.
Fenómenos atmosféricosE
El Niño
Warm phase of the ENSO cycle: anomalous warming of the equatorial Pacific that disrupts global climate.
ClimatologíaEnhanced Fujita scale
Scale from EF0 to EF5 that classifies tornado intensity based on observed damage.
Escalas y medidasEnsemble forecast
A forecasting technique that runs multiple weather model simulations with slightly different initial conditions to estimate uncertainty.
InstrumentosEquinox
Moment of the year when day and night are approximately equal in duration, marking the start of spring or autumn.
Astronomía meteorológicaEvaporation
The process by which liquid water transforms into water vapour by absorbing heat energy.
PrecipitaciónEvapotranspiration
The total amount of water transferred to the atmosphere by soil evaporation and plant transpiration combined.
PrecipitaciónF
Fog
Cloud at ground level that reduces visibility to less than 1,000 metres.
Fenómenos atmosféricosFogbow
An arc similar to a rainbow but white in colour, formed by refraction and reflection of light in very small fog droplets.
Óptica atmosféricaFöhn effect
Warming and drying of air as it descends the leeward slope of a mountain after having precipitated on the windward side.
Fenómenos atmosféricosFreezing rain
Rain that freezes on contact with surfaces below 0 °C, forming a transparent ice layer.
PrecipitaciónFrost
Drop in air or surface temperature below 0 °C, with possible ice formation.
TemperaturaG
Galerna
A sudden, violent northwesterly squall occurring over the Bay of Biscay, with abrupt temperature drops and hurricane-force winds.
VientoGlory
Optical phenomenon producing concentric coloured rings around the observer's shadow projected onto clouds or fog.
Óptica atmosféricaGraupel
Precipitation in the form of soft, opaque pellets of rimed snow, intermediate between snow and hail, 2-5 mm in diameter.
PrecipitaciónGreen flash
A brief flash of green light appearing at the upper rim of the solar disc during sunrise or sunset.
Óptica atmosféricaGreenhouse effect
Natural process by which certain atmospheric gases trap part of the heat radiated by Earth's surface.
ClimatologíaGust front
The surface boundary between the cold outflow air from a thunderstorm downdraft and the surrounding warm air.
Fenómenos atmosféricosH
Hail
Solid precipitation in the form of ice balls or irregular lumps that fall from intense convective clouds.
PrecipitaciónHailstorm
An episode of hail precipitation, usually associated with severe thunderstorms with strong updrafts.
Fenómenos atmosféricosHaze
Suspension of dust, sand or organic particles in the atmosphere that reduces visibility and gives the sky a yellowish tone.
Fenómenos atmosféricosHeat index
A measure of apparent temperature combining air temperature and relative humidity to indicate how the human body perceives heat.
TemperaturaHeatstroke
Medical emergency caused by failure of the body's thermoregulation when core temperature exceeds 40 °C, potentially fatal.
TemperaturaHeatwave
Extended period of abnormally high temperatures for the season and region.
TemperaturaHurricane
Tropical cyclone with sustained winds of 119 km/h or more, formed over warm tropical oceans.
Ciclones y tormentas severasHygrometer
Instrument that measures air humidity (relative or absolute).
InstrumentosI
Intertropical Convergence Zone
An equatorial low-pressure belt where the northern and southern trade winds converge, generating intense convection and rainfall.
ClimatologíaIsobar
Line on a weather map connecting points of equal atmospheric pressure.
GeneralIsohyet
Line on a map connecting points of equal accumulated precipitation.
GeneralIsotherm
Line on a map connecting points of equal temperature.
GeneralK
Katabatic wind
Cold wind that flows downhill driven by gravity, common in mountain areas and polar regions.
VientoKelvin
SI unit of temperature. 0 K is absolute zero (−273.15 °C).
Escalas y medidasKöppen classification
A worldwide climate classification system based on monthly temperature and precipitation, created by Wladimir Köppen.
ClimatologíaL
La Niña
Cold phase of the ENSO cycle: anomalous cooling of the equatorial Pacific that disrupts global climate.
ClimatologíaLake-effect snow
Phenomenon whereby cold air masses crossing large warm lakes or seas generate intense bands of snow or showers on the downwind shore.
Fenómenos atmosféricosLenticular cloud
Stationary lens-shaped cloud that forms downwind of mountains due to orographic waves.
NubesLevante
Easterly wind in the western Mediterranean, moist and associated with coastal rainfall.
VientoLightning
Electrical discharge between a cloud and the ground, between clouds, or within a cloud, reaching temperatures of 30,000 °C.
Fenómenos atmosféricosM
Madden-Julian Oscillation
Pattern of tropical convection that propagates eastward every 30-60 days, modulating rainfall and storm activity on a global scale.
ClimatologíaMammatus
Rounded protuberances hanging from a cloud base, associated with severe storms.
NubesMedicane
Quasi-tropical cyclone that forms over the Mediterranean Sea.
Ciclones y tormentas severasMesoscale convective system
An organised complex of thunderstorms spanning 100 km or more, lasting several hours and capable of producing torrential rainfall.
Ciclones y tormentas severasMesosphere
The atmospheric layer between 50 and 85 km altitude, the coldest layer of Earth's atmosphere.
GeneralMeteorological lidar
Instrument using laser pulses to measure vertical profiles of aerosols, clouds, water vapour, and wind in the atmosphere.
InstrumentosMicroburst
Intense, localised downdraft that produces destructive winds upon hitting the ground.
Ciclones y tormentas severasMilankovitch cycles
Periodic variations in Earth's orbit and axial tilt that regulate glacial and interglacial cycles over tens of thousands of years.
ClimatologíaMirage
An optical illusion caused by the refraction of light through layers of air with different temperature and density.
Óptica atmosféricaMistral
Cold, dry, and violent wind channelled down the Rhone valley toward the western Mediterranean, typical of southern France.
VientoMonsoon
Seasonal wind system that reverses direction between summer and winter, creating wet and dry seasons.
Fenómenos atmosféricosMud rain
Precipitation carrying suspended Saharan dust that leaves a reddish or orange deposit on surfaces as it evaporates.
Fenómenos atmosféricosN
Nimbostratus
Dark grey cloud of great horizontal extent that produces continuous rain or snow.
NubesNoctilucent cloud
Extremely high clouds (80-85 km) formed by ice crystals in the mesosphere, visible only during twilight.
NubesNorth Atlantic Oscillation
A climate pattern describing the variation in atmospheric pressure difference between Iceland and the Azores.
ClimatologíaO
Occluded front
Front formed when a cold front catches up with a warm front, combining characteristics of both.
Fenómenos atmosféricosOrographic precipitation
Rain or snow caused when moist air is forced to rise over a mountain.
PrecipitaciónOzone layer
Stratospheric zone (15–35 km) with high ozone concentration that filters harmful solar UV radiation.
GeneralP
Pileus
A smooth cap-shaped accessory cloud that forms briefly above the top of a growing cumulus or cumulonimbus.
NubesPlanetary boundary layer
Lowest layer of the atmosphere (0-2 km) directly influenced by Earth's surface, key for pollutant dispersion and local weather.
GeneralPoniente
A westerly wind blowing in the Mediterranean and various regions of Spain, generally warm and dry.
VientoPowder snow
Light, dry snow with low density and high air content, ideal for winter sports, formed at very low temperatures.
PrecipitaciónR
Radiation fog
Fog formed by radiative cooling of the ground during clear, calm nights.
Fenómenos atmosféricosRadiosonde
Instrument lifted by a balloon that measures temperature, humidity, and pressure as it ascends to 30 km.
InstrumentosRain
Precipitation in the form of liquid water drops with diameter exceeding 0.5 mm falling from clouds.
PrecipitaciónRain gauge
Instrument that collects and measures the amount of precipitation fallen on a surface.
InstrumentosRainbow
Multicoloured arc produced by refraction, reflection, and dispersion of sunlight in water droplets.
Óptica atmosféricaRelative humidity
Percentage of water vapour in the air relative to the maximum it could hold at that temperature.
GeneralReturn period
Average time interval between occurrences of extreme events of equal or greater magnitude, used in engineering and planning.
ClimatologíaRime ice
Ice deposit formed by the freezing of supercooled fog or cloud droplets upon contact with solid surfaces.
PrecipitaciónS
Saffir-Simpson scale
Scale from 1 to 5 that classifies hurricane intensity by sustained wind speed.
Escalas y medidasSandstorm
Phenomenon in which strong winds lift large quantities of sand and dust from the ground, reducing visibility below 1 km.
Fenómenos atmosféricosSea breeze
Local wind that blows from sea to land during the day, caused by differential heating of both surfaces.
VientoSirocco
Hot wind originating in the Sahara that crosses the Mediterranean, picking up moisture and carrying African dust toward southern Europe.
VientoSleet
Mixed precipitation of rain and partially melted snow, or translucent ice pellets.
PrecipitaciónSnow
Solid precipitation in the form of hexagonal ice crystals that cluster into snowflakes.
PrecipitaciónSolano
A warm, dry east or southeasterly wind blowing in central and southern Spain, associated with heat waves.
VientoSolar halo
Luminous ring around the sun produced by refraction of light in ice crystals of high clouds.
Óptica atmosféricaSolar radiation
Electromagnetic energy emitted by the sun reaching the Earth, the engine of the entire climate system.
Astronomía meteorológicaSolstice
Moment of the year when the sun reaches its highest or lowest position in the sky, marking the start of summer or winter.
Astronomía meteorológicaSquall line
An organised line of severe thunderstorms that moves as a front, producing destructive winds along a narrow band.
Ciclones y tormentas severasStationary front
Frontal boundary between two air masses that barely moves, causing persistent rain in the same area.
Fenómenos atmosféricosStratocumulus
Low cloud formed by rounded masses or rolls grouped in layers, partially grey and partially white.
NubesStratosphere
The layer of the atmosphere between approximately 12 and 50 km altitude, where the ozone layer is located.
GeneralStratus
Low, grey, uniform layer cloud that often covers the entire sky, producing drizzle.
NubesSublimation
The direct phase change from ice or snow to water vapour without passing through the liquid phase.
PrecipitaciónSundog
A bright spot of light appearing on either side of the sun, caused by refraction through atmospheric ice crystals.
Óptica atmosféricaSupercell
Thunderstorm with persistent rotation (mesocyclone), the most severe of all storms.
Ciclones y tormentas severasSynoptic chart
A weather map showing simultaneous atmospheric conditions over a wide region at a specific time.
InstrumentosT
Teleconnection
Statistical correlation between climate anomalies in geographically distant regions, linked through atmospheric circulation patterns.
ClimatologíaTemperature inversion
Anomalous situation where air temperature increases with altitude, trapping pollution and fog.
TemperaturaTerral
A nocturnal wind blowing from land toward the sea, particularly notable on the Mediterranean coast of Andalusia.
VientoThermohaline circulation
The global system of deep ocean currents driven by differences in water temperature and salinity.
ClimatologíaThermometer
Instrument that measures air temperature, typically in degrees Celsius (°C) or Fahrenheit (°F).
InstrumentosThunderstorm
Weather phenomenon with lightning and thunder, produced by cumulonimbus clouds with strong convection.
Fenómenos atmosféricosTornado
Violently rotating column of air extending from a thunderstorm cloud to the ground.
Ciclones y tormentas severasTORRO scale
Scale from T0 to T11 that classifies tornado intensity in Europe, complementary to the Fujita scale.
Escalas y medidasTrade winds
Persistent winds blowing from the northeast (Northern Hemisphere) or southeast (Southern Hemisphere) toward the equator.
VientoTramontana
A strong, cold north or northeasterly wind blowing in Catalonia, the Balearic Islands, and southern France.
VientoTropical night
Night in which the minimum temperature does not fall below 20 °C, preventing restorative rest and increasing mortality during heat waves.
TemperaturaTropopause
The boundary between the troposphere and stratosphere, where temperature stops decreasing with altitude.
GeneralTroposphere
Lowest layer of the atmosphere (0–12 km) where all weather phenomena occur.
GeneralU
V
W
Wall cloud
A low, often rotating cloud formation descending from the base of a cumulonimbus, frequently associated with severe thunderstorms and tornadoes.
NubesWarm front
Frontal boundary where warm air glides over retreating cold air, producing stratiform clouds and prolonged rain.
Fenómenos atmosféricosWater cycle
Continuous circulation of water between the atmosphere, land surface, and oceans through evaporation, condensation, and precipitation.
GeneralWaterspout
Rotating column of air forming over the sea, similar to an aquatic tornado.
Ciclones y tormentas severasWeather model
A computer program that simulates the atmosphere using physical equations to predict future weather.
InstrumentosWeather radar
Instrument that emits microwave pulses to detect, locate, and measure precipitation in real time.
InstrumentosWeather satellite
Artificial satellite that observes the atmosphere and Earth's surface for weather forecasting and monitoring.
InstrumentosWet-bulb temperature
Lowest temperature achievable by water evaporation in the air, a key indicator of the human survival limit under heat.
TemperaturaWind chill
Temperature perceived by the body, which differs from the actual temperature due to wind or humidity.
TemperaturaWind shear
Abrupt change in wind speed or direction over a short distance, horizontal or vertical.
VientoWMO
World Meteorological Organization: UN agency coordinating meteorology, climatology and hydrology internationally.
General