Windspeed
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In
meteorology Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agricultur ...
, wind speed, or
wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...
flow speed In continuum mechanics the flow velocity in fluid dynamics, also macroscopic velocity in statistical mechanics, or drift velocity in electromagnetism, is a vector field used to mathematically describe the motion of a continuum. The length of the ...
, is a fundamental
atmospheric An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...
quantity caused by air moving from
high High may refer to: Science and technology * Height * High (atmospheric), a high-pressure area * High (computability), a quality of a Turing degree, in computability theory * High (tectonics), in geology an area where relative tectonic uplift t ...
to
low pressure In meteorology, a low-pressure area (LPA), low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. It is the opposite of a high-pressure area. Low-pressure areas are commonly associated with inclem ...
, usually due to changes in temperature. Wind speed is now commonly measured with an
anemometer In meteorology, an anemometer () is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti ...
. Wind speed affects
weather forecasting Weather forecasting or weather prediction is the application of science and technology forecasting, to predict the conditions of the Earth's atmosphere, atmosphere for a given location and time. People have attempted to predict the weather info ...
,
aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' include fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air aircraft such as h ...
and
maritime Maritime may refer to: Geography * Maritime Alps, a mountain range in the southwestern part of the Alps * Maritime Region, a region in Togo * Maritime Southeast Asia * The Maritimes, the Canadian provinces of Nova Scotia, New Brunswick, and Princ ...
operations,
construction Construction are processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life. It typically starts with planning, financing, and design that continues until the a ...
projects, growth and
metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
rates of many plant species, and has countless other implications.
Wind direction Wind direction is generally reported by the direction from which the wind originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south; the exceptions are onshore winds (blowing onto the shore from the water) and ...
is usually almost parallel to isobars (and not perpendicular, as one might expect), due to
Earth's rotation Earth's rotation or Earth's spin is the rotation of planet Earth around its own Rotation around a fixed axis, axis, as well as changes in the orientation (geometry), orientation of the rotation axis in space. Earth rotates eastward, in progra ...
.


Units

The
meter per second The metre per second is the unit of both speed (a scalar quantity) and velocity (a vector quantity, which has direction and magnitude) in the International System of Units (SI), equal to the speed of a body covering a distance of one metre in ...
(m/s) is the
SI unit The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of units of measurement, system of measurement. It is the only system ...
for velocity and the unit recommended by the
World Meteorological Organization The World Meteorological Organization (WMO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology an ...
for reporting wind speeds, and used amongst others in weather forecasts in the
Nordic countries The Nordic countries (also known as the Nordics or ''Norden''; ) are a geographical and cultural region in Northern Europe, as well as the Arctic Ocean, Arctic and Atlantic Ocean, North Atlantic oceans. It includes the sovereign states of Denm ...
. Since 2010 the
International Civil Aviation Organization The International Civil Aviation Organization (ICAO ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international sch ...
(ICAO) also recommends meters per second for reporting wind speed when approaching
runway In aviation, a runway is an elongated, rectangular surface designed for the landing and takeoff of an aircraft. Runways may be a human-made surface (often asphalt concrete, asphalt, concrete, or a mixture of both) or a natural surface (sod, ...
s, replacing their former recommendation of using
kilometers per hour The kilometre per hour ( SI symbol: km/h; non-SI abbreviations: kph, kmph, km/hr) is a unit of speed, expressing the number of kilometres travelled in one hour. History Although the metre was formally defined in 1799, the term "kilometres per ho ...
(km/h). For historical reasons, other units such as
miles per hour Miles per hour (mph, m.p.h., MPH, or mi/h) is a British imperial and United States customary unit of speed expressing the number of miles travelled in one hour. It is used in the United Kingdom, the United States, and a number of smaller count ...
(mph),
knots A knot is a fastening in rope or interwoven lines. Knot or knots may also refer to: Other common meanings * Knot (unit), of speed * Knot (wood), a timber imperfection Arts, entertainment, and media Films * ''Knots'' (film), a 2004 film * ''Kn ...
(kn), and
feet per second The foot per second (plural feet per second) is a unit of both speed (scalar) and velocity (vector quantity, which includes direction). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s). The corre ...
(ft/s) are also sometimes used to measure wind speeds. Historically, wind speeds have also been classified using the
Beaufort scale The Beaufort scale ( ) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. It was devised in 1805 by Francis Beaufort a hydrographer in the Royal Navy. It ...
, which is based on visual observations of specifically defined wind effects at sea or on land.


Factors affecting wind speed

Wind speed is affected by a number of factors and situations, operating on varying scales (from micro to macro scales). These include the
pressure gradient In hydrodynamics and hydrostatics, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular locat ...
,
Rossby wave Rossby waves, also known as planetary waves, are a type of inertial wave naturally occurring in rotating fluids. They were first identified by Sweden-born American meteorologist Carl-Gustaf Arvid Rossby in the Earth's atmosphere in 1939. They ...
s,
jet stream Jet streams are fast flowing, narrow thermal wind, air currents in the Earth's Atmosphere of Earth, atmosphere. The main jet streams are located near the altitude of the tropopause and are westerly winds, flowing west to east around the gl ...
s, and local weather conditions. There are also links to be found between wind speed and
wind direction Wind direction is generally reported by the direction from which the wind originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south; the exceptions are onshore winds (blowing onto the shore from the water) and ...
, notably with the pressure gradient and terrain conditions. The Pressure gradient describes the difference in air pressure between two points in the atmosphere or on the surface of the Earth. It is vital to wind speed, because the greater the difference in pressure, the faster the wind flows (from the high to low pressure) to balance out the variation. The pressure gradient, when combined with the
Coriolis effect In physics, the Coriolis force is a pseudo force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the moti ...
and
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...
, also influences
wind direction Wind direction is generally reported by the direction from which the wind originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south; the exceptions are onshore winds (blowing onto the shore from the water) and ...
. Rossby waves are strong winds in the upper
troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
. These operate on a global scale and move from west to east (hence being known as
westerlies The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes (about ...
). The Rossby waves are themselves a different wind speed from that experienced in the lower
troposphere The troposphere is the lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...
. Local weather conditions play a key role in influencing wind speed, as the formation of
hurricanes A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...
,
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in Atmosphere of Earth, atmospheric circulation and precipitation associated with annu ...
s, and
cyclones In meteorology, a cyclone () is a large air mass that rotates around a strong center of low atmospheric pressure, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an ant ...
as freak weather conditions can drastically affect the flow velocity of the wind.


Highest speed


Non-tornadic

The fastest wind speed not related to
tornado A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...
es ever recorded was during the passage of Tropical
Cyclone Olivia Severe Tropical Cyclone Olivia was a powerful cyclone, the 13th named storm of the 1995–96 Australian region cyclone season, which formed on 3 April 1996 to the north of Australia's Northern Territory. The storm moved generally to the southwes ...
on 10 April 1996: an
automatic weather station An automatic weather station (AWS) is an automated version of the traditional weather station, either to save human labor or to enable measurements from remote areas. An AWS will typically consist of a weather-proof enclosure containing the data ...
on
Barrow Island Barrow Island or may Barrow Island''s'' refer to: * Barrow Island, an island located in Western Australia * N. and S. Barrow Islands, a pair of islands located in Queensland, Australia * Barrow Island, a former island in Barrow-in-Furness, Englan ...
,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
, registered a maximum
wind gust A wind gust or just gust is a brief, sudden increase in the wind speed. It usually lasts for less than 20seconds, briefer than a ''squall'', which lasts minutes. A gust is followed by a lull (or slackening) in the wind speed. Generally, winds are ...
of The wind gust was evaluated by the WMO Evaluation Panel, who found that the anemometer was mechanically sound and that the gust was within statistical probability and ratified the measurement in 2010. The anemometer was mounted 10 m above ground level (and thus 64 m above sea level). During the cyclone, several extreme gusts of greater than were recorded, with a maximum 5-minute mean speed of ; the extreme gust factor was on the order of 2.27–2.75 times the mean wind speed. The pattern and scales of the gusts suggest that a
mesovortex A mesovortex is a small-scale rotational feature found in a Thunderstorm, convective storm, such as a quasi-linear convective system (QLCS, i.e. squall line), a supercell, or the eyewall of a tropical cyclone. Mesovortices range in diameter from te ...
was embedded in the already-strong
eyewall The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weath ...
of the cyclone. Currently, the second-highest surface wind speed ever officially recorded is at the
Mount Washington (New Hampshire) Mount Washington is an ultra-prominent peak, ultra-prominent mountain in the state of New Hampshire. It is the highest peak in the Northeastern United States at and the most Topographic prominence, topographically prominent mountain east of the ...
Observatory above sea level in the US on 12 April 1934, using a hot-wire anemometer. The anemometer, specifically designed for use on Mount Washington, was later tested by the US National Weather Bureau and confirmed to be accurate.


Tornadic

Wind speeds within certain atmospheric phenomena (such as
tornado A tornado is a violently rotating column of air that is in contact with the surface of Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, although the ...
es) may greatly exceed these values but have never been accurately measured. Directly measuring these tornadic winds is rarely done, as the violent wind would destroy the instruments. A method of estimating speed is to use
Doppler on Wheels Doppler on Wheels (DOW) is a fleet of quickly deployable truck-mounted weather radars managed by FARM (Flexible Array of Radars and Mesonets), an American research company affiliated with the University of Alabama Huntsville. The group, which ...
or mobile
Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...
s to measure the wind speeds remotely. Using this method, a mobile radar (
RaXPol The Rapid X-band Polarimetric Radar, commonly abbreviated as RaXPol, is a mobile research radar designed and operated by the University of Oklahoma, led by Howard Bluestein. RaXPol often collaborates with adjacent mobile radar projects, such as ...
) owned and operated by the
University of Oklahoma The University of Oklahoma (OU) is a Public university, public research university in Norman, Oklahoma, United States. Founded in 1890, it had existed in Oklahoma Territory near Indian Territory for 17 years before the two territories became the ...
recorded winds up to inside the
2013 El Reno tornado The 2013 El Reno tornado was an extremely large, powerful, and erratic tornado that occurred over rural areas of Central Oklahoma during the early evening hours of Friday, May 31, 2013. This rain-wrapped, multiple-vortex tornado was the wide ...
, marking the fastest winds ever observed by radar in history. In 1999, a mobile radar measured winds up to during the
1999 Bridge Creek–Moore tornado The 1999 Bridge Creek–Moore tornado was a large, long-lived, and exceptionally powerful Fujita scale, F5 tornado in which the Tornado records, highest tornado wind speed ever measured with a doppler radar was recorded at by a Doppler on Wh ...
in
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
on 3 May, although another figure of has also been quoted for the same tornado. Yet another number used by the Center for Severe Weather Research for that measurement is . However, speeds measured by
Doppler weather radar A weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pu ...
are not considered official records.


On other planets

Wind speeds can be much higher on
exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...
s. Scientists at the University of Warwick in 2015 determined that
HD 189733b HD 189733 b is an exoplanet in the constellation of Vulpecula approximately away from the Solar System. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. ...
has winds of . In a press release, the University announced that the methods used from measuring HD 189733b's wind speeds could be used to measure wind speeds on Earth-like exoplanets.


Measurement

An anemometer is one of the tools used to measure wind speed. A device consisting of a vertical pillar and three or four concave cups, the anemometer captures the horizontal movement of air particles (wind speed). Unlike traditional cup-and-vane anemometers, ultrasonic wind sensors have no moving parts and are therefore used to measure wind speed in applications that require maintenance-free performance, such as atop wind turbines. As the name suggests, ultrasonic wind sensors measure the wind speed using high-frequency sound. An ultrasonic anemometer has two or three pairs of sound transmitters and receivers. Each transmitter constantly beams high-frequency sound to its receiver. Electronic circuits inside measure the time it takes for the sound to make its journey from each transmitter to the corresponding receiver. Depending on how the wind blows, some of the sound beams will be affected more than the others, slowing it down or speeding it up very slightly. The circuits measure the difference in speeds of the beams and use that to calculate how fast the wind is blowing. Acoustic resonance wind sensors are a variant of the ultrasonic sensor. Instead of using time of flight measurement, acoustic resonance sensors use resonating acoustic waves within a small purpose-built cavity. Built into the cavity is an array of
ultrasonic transducers Ultrasound is sound with frequencies greater than 20 kilohertz. This frequency is the approximate upper audible limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, includi ...
, which are used to create the separate standing-wave patterns at ultrasonic frequencies. As wind passes through the cavity, a change in the wave's property occurs (phase shift). By measuring the amount of phase shift in the received signals by each transducer, and then by mathematically processing the data, the sensor is able to provide an accurate horizontal measurement of wind speed and direction. Another tool used to measure wind velocity includes a GPS combined with
pitot tube A pitot tube ( ; also pitot probe) measures fluid flow velocity. It was invented by French engineer Henri Pitot during his work with aqueducts and published in 1732, and modified to its modern form in 1858 by Henry Darcy. It is widely use ...
. A fluid flow velocity tool, the
Pitot tube A pitot tube ( ; also pitot probe) measures fluid flow velocity. It was invented by French engineer Henri Pitot during his work with aqueducts and published in 1732, and modified to its modern form in 1858 by Henry Darcy. It is widely use ...
is primarily used to determine the air velocity of an aircraft.


Design of structures

Wind speed is a common factor in the design of structures and buildings around the world. It is often the governing factor in the required lateral strength of a structure's design. In the United States, the wind speed used in design is often referred to as a "3-second gust", which is the highest sustained gust over a 3-second period having a probability of being exceeded per year of 1 in 50 (ASCE 7-05, updated to ASCE 7-16). This design wind speed is accepted by most building codes in the United States and often governs the lateral design of buildings and structures. In Canada, reference wind pressures are used in design and are based on the "mean hourly" wind speed having a probability of being exceeded per year of 1 in 50. The reference wind pressure is calculated using the equation , where is the air density and is the wind speed. Historically, wind speeds have been reported with a variety of averaging times (such as fastest mile, 3-second gust, 1-minute, and mean hourly) which designers may have to take into account. To convert wind speeds from one averaging time to another, the Durst Curve was developed, which defines the relation between probable maximum wind speed averaged over some number of seconds to the mean wind speed over one hour.ASCE 7-05 commentary Figure C6-4, ASCE 7-10 C26.5-1


See also

*
American Society of Civil Engineers The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...
(promulgator of ASCE 7-05, current version is ASCE 7-16) *
Beaufort scale The Beaufort scale ( ) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale. It was devised in 1805 by Francis Beaufort a hydrographer in the Royal Navy. It ...
*
Fujita scale The Fujita scale (F-Scale; ), or Fujita–Pearson scale (FPP scale), is a scale for rating tornado intensity, based primarily on the damage tornadoes inflict on human-built structures and vegetation. The official Fujita scale category is determ ...
and
Enhanced Fujita Scale The Enhanced Fujita scale (abbreviated EF-Scale) is a scale that rates tornado intensity based on the severity of the damage a tornado causes. It is used in the United States and France, among other countries. The EF scale is also unofficially ...
*
International Building Code The International Code Council (ICC), also known as the Code Council, is an American nonprofit standards organization sponsored by the building trades, which was founded in 1994 through the merger of three regional model code organizations in th ...
(promulgator of NBC 2005) * ICAO recommendations – International System of Units *
Knot (unit) The knot () is a unit of speed equal to one nautical mile per hour, exactly (approximately or ). The ISO standard symbol for the knot is kn. The same symbol is preferred by the Institute of Electrical and Electronics Engineers ( IEEE), whil ...
*
Prevailing wind In meteorology, prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point on t ...
* Saffir–Simpson Hurricane Scale *
TORRO scale The TORRO tornado intensity scale (or T-Scale) is a scale measuring tornado intensity between T0 and T11. It was proposed by Terence Meaden of the Tornado and Storm Research Organisation (TORRO), a meteorological organisation in the United Kingdo ...
*
Wind direction Wind direction is generally reported by the direction from which the wind originates. For example, a ''north'' or ''northerly'' wind blows from the north to the south; the exceptions are onshore winds (blowing onto the shore from the water) and ...


References


External links

* {{DEFAULTSORT:Wind Speed Wind Airspeed Meteorological quantities Wind power Weather extremes of Earth es:Viento#Características físicas de los vientos