Weather is the state of the atmosphere, describing for example the
degree to which it is hot or cold, wet or dry, calm or stormy, clear
or cloudy. Most weather phenomena occur in the lowest level of the
atmosphere, the troposphere, just below the stratosphere.
Weather refers to day-to-day temperature and precipitation activity,
whereas climate is the term for the averaging of atmospheric
conditions over longer periods of time. When used without
qualification, "weather" is generally understood to mean the weather
Weather is driven by air pressure, temperature and moisture
differences between one place and another. These differences can occur
due to the sun's angle at any particular spot, which varies with
latitude. The strong temperature contrast between polar and tropical
air gives rise to the largest scale atmospheric circulations: the
Hadley Cell, the Ferrel Cell, the Polar Cell, and the jet stream.
Weather systems in the mid-latitudes, such as extratropical cyclones,
are caused by instabilities of the jet stream flow. Because the
Earth's axis is tilted relative to its orbital plane, sunlight is
incident at different angles at different times of the year. On
Earth's surface, temperatures usually range ±40 °C
(−40 °F to 100 °F) annually. Over thousands of years,
changes in Earth's orbit can affect the amount and distribution of
solar energy received by the Earth, thus influencing long-term climate
and global climate change.
Surface temperature differences in turn cause pressure differences.
Higher altitudes are cooler than lower altitudes, as most atmospheric
heating is due to contact with the Earth's surface while radiative
losses to space are mostly constant.
Weather forecasting is the
application of science and technology to predict the state of the
atmosphere for a future time and a given location. The Earth's weather
system is a chaotic system; as a result, small changes to one part of
the system can grow to have large effects on the system as a whole.
Human attempts to control the weather have occurred throughout
history, and there is evidence that human activities such as
agriculture and industry have modified weather patterns.
Studying how the weather works on other planets has been helpful in
understanding how weather works on Earth. A famous landmark in the
Solar System, Jupiter's Great Red Spot, is an anticyclonic storm known
to have existed for at least 300 years. However, weather is not
limited to planetary bodies. A star's corona is constantly being lost
to space, creating what is essentially a very thin atmosphere
throughout the Solar System. The movement of mass ejected from the Sun
is known as the solar wind.
2 Shaping the planet Earth
3 Effect on humans
3.1 Effects on populations
6 Microscale meteorology
7 Extremes on Earth
8 Extraterrestrial within the Solar System
10 How To Measure The Weather
11 See also
13 External links
Cumulus mediocris cloud surrounded by stratocumulus
On Earth, the common weather phenomena include wind, cloud, rain,
snow, fog and dust storms. Less common events include natural
disasters such as tornadoes, hurricanes, typhoons and ice storms.
Almost all familiar weather phenomena occur in the troposphere (the
lower part of the atmosphere).
Weather does occur in the
stratosphere and can affect weather lower down in the troposphere, but
the exact mechanisms are poorly understood.
Weather occurs primarily due to air pressure, temperature and moisture
differences between one place to another. These differences can occur
due to the sun angle at any particular spot, which varies by latitude
from the tropics. In other words, the farther from the tropics one
lies, the lower the sun angle is, which causes those locations to be
cooler due the spread of the sunlight over a greater surface. The
strong temperature contrast between polar and tropical air gives rise
to the large scale atmospheric circulation cells and the jet
Weather systems in the mid-latitudes, such as extratropical
cyclones, are caused by instabilities of the jet stream flow (see
Weather systems in the tropics, such as monsoons or
organized thunderstorm systems, are caused by different processes.
2015 – Warmest Global Year on Record (since 1880) – Colors
indicate temperature anomalies (NASA/NOAA; 20 January 2016).
Because the Earth's axis is tilted relative to its orbital plane,
sunlight is incident at different angles at different times of the
year. In June the Northern Hemisphere is tilted towards the sun, so at
any given Northern Hemisphere latitude sunlight falls more directly on
that spot than in December (see Effect of sun angle on climate).
This effect causes seasons. Over thousands to hundreds of thousands of
years, changes in Earth's orbital parameters affect the amount and
distribution of solar energy received by the
Earth and influence
long-term climate. (See Milankovitch cycles).
The uneven solar heating (the formation of zones of temperature and
moisture gradients, or frontogenesis) can also be due to the weather
itself in the form of cloudiness and precipitation. Higher
altitudes are typically cooler than lower altitudes, which the result
of higher surface temperature and radiational heating, which produces
the adiabatic lapse rate. In some situations, the temperature
actually increases with height. This phenomenon is known as an
inversion and can cause mountaintops to be warmer than the valleys
below. Inversions can lead to the formation of fog and often act as a
cap that suppresses thunderstorm development. On local scales,
temperature differences can occur because different surfaces (such as
oceans, forests, ice sheets, or man-made objects) have differing
physical characteristics such as reflectivity, roughness, or moisture
Surface temperature differences in turn cause pressure differences. A
hot surface warms the air above it causing it to expand and lower the
density and the resulting surface air pressure. The resulting
horizontal pressure gradient moves the air from higher to lower
pressure regions, creating a wind, and the
Earth's rotation then
causes deflection of this air flow due to the Coriolis effect. The
simple systems thus formed can then display emergent behaviour to
produce more complex systems and thus other weather phenomena. Large
scale examples include the
Hadley cell while a smaller scale example
would be coastal breezes.
The atmosphere is a chaotic system. As a result, small changes to one
part of the system can accumulate and magnify to cause large effects
on the system as a whole. This atmospheric instability makes
weather forecasting less predictable than tides or eclipses.
Although it is difficult to accurately predict weather more than a few
days in advance, weather forecasters are continually working to extend
this limit through meteorological research and refining current
methodologies in weather prediction. However, it is theoretically
impossible to make useful day-to-day predictions more than about two
weeks ahead, imposing an upper limit to potential for improved
Shaping the planet Earth
Main article: Weathering
Weather is one of the fundamental processes that shape the Earth. The
process of weathering breaks down the rocks and soils into smaller
fragments and then into their constituent substances. During rains
precipitation, the water droplets absorb and dissolve carbon dioxide
from the surrounding air. This causes the rainwater to be slightly
acidic, which aids the erosive properties of water. The released
sediment and chemicals are then free to take part in chemical
reactions that can affect the surface further (such as acid rain), and
sodium and chloride ions (salt) deposited in the seas/oceans. The
sediment may reform in time and by geological forces into other rocks
and soils. In this way, weather plays a major role in erosion of the
Effect on humans
Further information: Biometeorology
Weather, seen from an anthropological perspective, is something all
humans in the world constantly experience through their senses, at
least while being outside. There are socially and scientifically
constructed understandings of what weather is, what makes it change,
the effect it has on humans in different situations, etc.
Therefore, weather is something people often communicate about.
Effects on populations
New Orleans, Louisiana, after being struck by Hurricane Katrina.
Katrina was a
Category 3 hurricane
Category 3 hurricane when it struck although it had been
a category 5 hurricane in the Gulf of Mexico.
Weather has played a large and sometimes direct part in human history.
Aside from climatic changes that have caused the gradual drift of
populations (for example the desertification of the Middle East, and
the formation of land bridges during glacial periods), extreme weather
events have caused smaller scale population movements and intruded
directly in historical events. One such event is the saving of Japan
from invasion by the Mongol fleet of
Kublai Khan by the Kamikaze winds
in 1281. French claims to Florida came to an end in 1565 when a
hurricane destroyed the French fleet, allowing Spain to conquer Fort
Caroline. More recently,
Hurricane Katrina redistributed over one
million people from the central
Gulf coast elsewhere across the United
States, becoming the largest diaspora in the history of the United
Ice Age caused crop failures and famines in Europe. The
1690s saw the worst famine in France since the Middle Ages. Finland
suffered a severe famine in 1696–1697, during which about one-third
of the Finnish population died.
Forecast of surface pressures five days into the future for the north
Pacific, North America, and north Atlantic
Ocean as on 9 June 2008
Weather forecasting is the application of science and technology to
predict the state of the atmosphere for a future time and a given
location. Human beings have attempted to predict the weather
informally for millennia, and formally since at least the nineteenth
Weather forecasts are made by collecting quantitative
data about the current state of the atmosphere and using scientific
understanding of atmospheric processes to project how the atmosphere
Once an all-human endeavor based mainly upon changes in barometric
pressure, current weather conditions, and sky condition,
forecast models are now used to determine future conditions. On the
other hand, human input is still required to pick the best possible
forecast model to base the forecast upon, which involve many
disciplines such as pattern recognition skills, teleconnections,
knowledge of model performance, and knowledge of model biases.
The chaotic nature of the atmosphere, the massive computational power
required to solve the equations that describe the atmosphere, error
involved in measuring the initial conditions, and an incomplete
understanding of atmospheric processes mean that forecasts become less
accurate as the difference in current time and the time for which the
forecast is being made (the range of the forecast) increases. The use
of ensembles and model consensus helps to narrow the error and pick
the most likely outcome.
There are a variety of end users to weather forecasts. Weather
warnings are important forecasts because they are used to protect life
and property. Forecasts based on temperature and precipitation
are important to agriculture, and therefore to
commodity traders within stock markets. Temperature forecasts are used
by utility companies to estimate demand over coming days.
In some areas, people use weather forecasts to determine what to wear
on a given day. Since outdoor activities are severely curtailed by
heavy rain, snow and the wind chill, forecasts can be used to plan
activities around these events, and to plan ahead to survive through
The aspiration to control the weather is evident throughout human
history: from ancient rituals intended to bring rain for crops to the
U.S. Military Operation Popeye, an attempt to disrupt supply lines by
lengthening the North Vietnamese monsoon. The most successful attempts
at influencing weather involve cloud seeding; they include the fog-
and low stratus dispersion techniques employed by major airports,
techniques used to increase winter precipitation over mountains, and
techniques to suppress hail. A recent example of weather control
was China's preparation for the 2008
Summer Olympic Games. China shot
1,104 rain dispersal rockets from 21 sites in the city of
an effort to keep rain away from the opening ceremony of the games on
8 August 2008. Guo Hu, head of the
Beijing Municipal Meteorological
Bureau (BMB), confirmed the success of the operation with 100
millimeters falling in
Baoding City of Hebei Province, to the
southwest and Beijing's
Fangshan District recording a rainfall of 25
Whereas there is inconclusive evidence for these techniques' efficacy,
there is extensive evidence that human activity such as agriculture
and industry results in inadvertent weather modification:
Acid rain, caused by industrial emission of sulfur dioxide and
nitrogen oxides into the atmosphere, adversely affects freshwater
lakes, vegetation, and structures.
Anthropogenic pollutants reduce air quality and visibility.
Climate change caused by human activities that emit greenhouse gases
into the air is expected to affect the frequency of extreme weather
events such as drought, extreme temperatures, flooding, high winds,
and severe storms.
Heat, generated by large metropolitan areas have been shown to
minutely affect nearby weather, even at distances as far as 1,600
kilometres (990 mi).
The effects of inadvertent weather modification may pose serious
threats to many aspects of civilization, including ecosystems, natural
resources, food and fiber production, economic development, and human
Microscale meteorology is the study of short-lived atmospheric
phenomena smaller than mesoscale, about 1 km or less. These two
branches of meteorology are sometimes grouped together as "mesoscale
and microscale meteorology" (MMM) and together study all phenomena
smaller than synoptic scale; that is they study features generally too
small to be depicted on a weather map. These include small and
generally fleeting cloud "puffs" and other small cloud features.
Extremes on Earth
Early morning sunshine over Bratislava, Slovakia. February 2008.
The same area, just three hours later, after light snowfall
Main articles: Extremes on
Earth and List of weather records
On Earth, temperatures usually range ±40 °C (100 °F to
−40 °F) annually. The range of climates and latitudes across
the planet can offer extremes of temperature outside this range. The
coldest air temperature ever recorded on
Earth is −89.2 °C
(−128.6 °F), at Vostok Station,
Antarctica on 21 July 1983.
The hottest air temperature ever recorded was 57.7 °C
(135.9 °F) at 'Aziziya, Libya, on 13 September 1922, but
that reading is queried. The highest recorded average annual
temperature was 34.4 °C (93.9 °F) at Dallol, Ethiopia.
The coldest recorded average annual temperature was −55.1 °C
(−67.2 °F) at Vostok Station, Antarctica.
The coldest average annual temperature in a permanently inhabited
location is at Eureka, Nunavut, in Canada, where the annual average
temperature is −19.7 °C (−3.5 °F).
Extraterrestrial within the Solar System
Great Red Spot
Great Red Spot in February 1979, photographed by the
NASA space probe.
Studying how the weather works on other planets has been seen as
helpful in understanding how it works on Earth.
Weather on other
planets follows many of the same physical principles as weather on
Earth, but occurs on different scales and in atmospheres having
different chemical composition. The
Cassini–Huygens mission to Titan
discovered clouds formed from methane or ethane which deposit rain
composed of liquid methane and other organic compounds. Earth's
atmosphere includes six latitudinal circulation zones, three in each
hemisphere. In contrast, Jupiter's banded appearance shows many
such zones, Titan has a single jet stream near the 50th parallel
north latitude, and
Venus has a single jet near the equator.
One of the most famous landmarks in the Solar System, Jupiter's Great
Red Spot, is an anticyclonic storm known to have existed for at least
300 years. On other gas giants, the lack of a surface allows the
wind to reach enormous speeds: gusts of up to 600 metres per
second (about 2,100 km/h or 1,300 mph) have been measured on
the planet Neptune. This has created a puzzle for planetary
scientists. The weather is ultimately created by solar energy and the
amount of energy received by
Neptune is only about 1⁄900 of that
received by Earth, yet the intensity of weather phenomena on Neptune
is far greater than on Earth. The strongest planetary winds
discovered so far are on the extrasolar planet HD 189733 b, which is
thought to have easterly winds moving at more than 9,600 kilometres
per hour (6,000 mph).
Weather is not limited to planetary bodies. Like all stars, the sun's
corona is constantly being lost to space, creating what is essentially
a very thin atmosphere throughout the Solar System. The movement of
mass ejected from the
Sun is known as the solar wind. Inconsistencies
in this wind and larger events on the surface of the star, such as
coronal mass ejections, form a system that has features analogous to
conventional weather systems (such as pressure and wind) and is
generally known as space weather. Coronal mass ejections have been
tracked as far out in the solar system as Saturn. The activity of
this system can affect planetary atmospheres and occasionally
surfaces. The interaction of the solar wind with the terrestrial
atmosphere can produce spectacular aurorae, and can play havoc
with electrically sensitive systems such as electricity grids and
How To Measure The Weather
Symbols you will need to measure the weather
This picture on the left will teach you how to read a weather chart.
This is the language people speak in when talking about weather.
A basic quiz to see how well you can read the weather.
Outline of meteorology
^ Merriam-Webster Dictionary. Weather. Retrieved on 27 June 2008.
^ Glossary of Meteorology. Hydrosphere. Archived 15 March 2012 at the
Wayback Machine. Retrieved on 27 June 2008.
^ a b Glossary of Meteorology. Troposphere. Archived 28 September 2012
at the Wayback Machine. Retrieved on 27 June 2008.
^ "Climate". Glossary of Meteorology. American Meteorological Society.
Retrieved 14 May 2008.
^ O'Carroll, Cynthia M. (18 October 2001). "
Weather Forecasters May
Look Sky-high For Answers".
Goddard Space Flight Center
Goddard Space Flight Center (NASA).
Archived from the original on 12 July 2009.
^ NASA. World Book at NASA: Weather. Archived copy at
March 2013). Retrieved on 27 June 2008.
^ John P. Stimac. 
Air pressure and wind. Retrieved on 8 May 2008.
^ Carlyle H. Wash, Stacey H. Heikkinen, Chi-Sann Liou, and Wendell A.
Nuss. A Rapid Cyclogenesis Event during GALE IOP 9. Retrieved on 28
^ Brown, Dwayne; Cabbage, Michael; McCarthy, Leslie; Norton, Karen (20
January 2016). "NASA,
NOAA Analyses Reveal Record-Shattering Global
Warm Temperatures in 2015". NASA. Retrieved 21 January 2016.
^ Windows to the Universe. Earth's Tilt Is the Reason for the Seasons!
Retrieved on 28 June 2008.
^ Milankovitch, Milutin. Canon of Insolation and the
Ice Age Problem.
Zavod za Udz̆benike i Nastavna Sredstva: Belgrade, 1941.
^ Ron W. Przybylinski. The Concept of
Frontogenesis and its
Weather Forecasting. Retrieved on 28 June 2008.
^ Mark Zachary Jacobson (2005). Fundamentals of Atmospheric Modeling
(2nd ed.). Cambridge University Press. ISBN 0-521-83970-X.
^ C. Donald Ahrens (2006).
Meteorology Today (8th ed.). Brooks/Cole
Publishing. ISBN 0-495-01162-2. OCLC 224863929.
^ Michel Moncuquet. Relation between density and temperature.
Retrieved on 28 June 2008.
^ Encyclopedia of Earth. Wind. Retrieved on 28 June 2008.
^ Spencer Weart. The Discovery of Global Warming. Retrieved on 28 June
^ Lorenz, Edward (July 1969). "How Much Better Can
Become?" (PDF). web.mit.edu/. Massachusetts Institute of Technology.
Retrieved July 21, 2017.
^ "The Discovery of Global Warming: Chaos in the Atmosphere".
history.aip.org. January 2017. Retrieved July 21, 2017.
NASA Mission Finds New Clues to Guide Search for
Life on Mars.
Retrieved on 28 June 2008.
^ West Gulf River Forecast Center. Glossary of Hydrologic Terms: E
Retrieved on 28 June 2008.
^ Crate, Susan A; Nuttall, Mark, eds. (2009). Anthropology and Climate
Change: From Encounters to Actions (PDF). Walnut Creek, CA: Left Coast
Press. pp. 70–86, i.e. the chapter '
Climate and weather
discourse in anthropology: from determinism to uncertain futures' by
Nicholas Peterson & Kenneth Broad.
^ James P. Delgado. Relics of the Kamikaze. Retrieved on 28 June 2008.
^ Mike Strong.
Fort Caroline National Memorial. Archived 17 November
2012 at the Wayback Machine. Retrieved on 28 June 2008.
^ Anthony E. Ladd, John Marszalek, and Duane A. Gill. The Other
Diaspora: New Orleans Student Evacuation Impacts and Responses
Surrounding Hurricane Katrina. Archived 24 June 2008 at the Wayback
Machine. Retrieved on 29 March 2008.
Famine in Scotland: The 'Ill Years' of the 1690s". Karen J. Cullen
(2010). Edinburgh University Press. p.21. ISBN 0-7486-3887-3
^ Eric D. Craft. An Economic History of
Weather Forecasting. Archived
3 May 2007 at the Wayback Machine. Retrieved on 15 April 2007.
Weather Forecasting Through the Ages. Retrieved on 25 May
Weather Doctor. Applying The Barometer To
Retrieved on 25 May 2008.
^ Mark Moore. Field Forecasting: A Short Summary. Archived 25 March
2009 at the Wayback Machine. Retrieved on 25 May 2008.
^ Klaus Weickmann, Jeff Whitaker, Andres Roubicek and Catherine Smith.
The Use of Ensemble Forecasts to Produce Improved Medium Range (3–15
Weather Forecasts. Retrieved on 16 February 2007.
^ Todd Kimberlain.
Tropical cyclone motion and intensity talk (June
2007). Retrieved on 21 July 2007.
^ Richard J. Pasch, Mike Fiorino, and Chris Landsea. TPC/NHC’S
REVIEW OF THE NCEP PRODUCTION SUITE FOR 2006.[permanent dead link]
Retrieved on 5 May 2008.
National Weather Service
National Weather Service Mission
Statement. Archived 24 November 2013 at the Wayback Machine. Retrieved
on 25 May 2008.
^ National Meteorological Service of Slovenia
^ Blair Fannin. Dry weather conditions continue for Texas. Archived 3
July 2009 at the Wayback Machine. Retrieved on 26 May 2008.
^ Dr. Terry Mader. Drought Corn Silage. Archived 5 October 2011 at the
Wayback Machine. Retrieved on 26 May 2008.
^ Kathryn C. Taylor. Peach Orchard Establishment and Young Tree Care.
Archived 24 December 2008 at the Wayback Machine. Retrieved on 26 May
^ Associated Press. After Freeze, Counting Losses to Orange Crop.
Retrieved on 26 May 2008.
^ The New York Times. FUTURES/OPTIONS; Cold
Weather Brings Surge In
Prices of Heating Fuels. Retrieved on 25 May 2008.
^ BBC. Heatwave causes electricity surge. Retrieved on 25 May 2008.
^ Toronto Catholic Schools. The Seven Key Messages of the
Program. Archived 17 February 2012 at the Wayback Machine. Retrieved
on 25 May 2008.
^ a b
American Meteorological Society
American Meteorological Society Archived 12 June 2010 at the
^ Huanet, Xin (9 August 2008). "
Beijing disperses rain to dry Olympic
night". Chinaview. Retrieved 24 August 2008.
^ Intergovernmental Panel on
^ Zhang, Guang (28 January 2012). "Cities Affect Temperatures for
Thousands of Miles". ScienceDaily.
^ Intergovernmental Panel on
^ Rogers, R. (1989). A Short Course in
Cloud Physics. Oxford:
Butterworth-Heinemann. pp. 61–62.
^ Global Measured Extremes of Temperature and Precipitation. National
Climatic Data Center. Retrieved on 21 June 2007.
^ Glenn Elert. Hottest Temperature on Earth. Retrieved on 28 June
^ Glenn Elert. Coldest Temperature On Earth. Retrieved on 28 June
Climate Normals 1971–2000 – Eureka
^ Britt, Robert Roy (6 March 2001). "The Worst
Weather in the Solar
System". Space.com. Archived from the original on 2 May 2001.
^ M. Fulchignoni; F. Ferri; F. Angrilli; A. Bar-Nun; M.A. Barucci; G.
Bianchini; et al. (2002). "The Characterisation of Titan's Atmospheric
Physical Properties by the Huygens Atmospheric Structure Instrument
Space Science Reviews. 104: 395–431.
^ Jet Propulsion Laboratory. OVERVIEW – Climate: The Spherical Shape
of the Earth: Climatic Zones. Archived 26 July 2009 at the Wayback
Machine. Retrieved on 28 June 2008.
^ Anne Minard. Jupiter's "Jet Stream" Heated by Surface, Not Sun.
Retrieved on 28 June 2008.
^ ESA: Cassini–Huygens. The jet stream of Titan. Retrieved on 28
^ Georgia State University. The Environment of Venus. Retrieved on 28
^ Ellen Cohen. "Jupiter's Great Red Spot". Hayden Planetarium.
Archived from the original on 8 August 2007. Retrieved 16 November
^ Suomi, V. E.; Limaye, S. S.; Johnson, D. R. (1991). "High Winds of
Neptune: A possible mechanism". Science. AAAS (USA). 251 (4996):
doi:10.1126/science.251.4996.929. PMID 17847386.
^ Sromovsky, Lawrence A. (14 October 1998). "Hubble Provides a Moving
Look at Neptune's Stormy Disposition". HubbleSite.
^ Knutson, Heather A.; David Charbonneau; Lori E. Allen; Jonathan J.
Fortney; Eric Agol; Nicolas B. Cowan; et al. (10 May 2007). "A map of
the day–night contrast of the extrasolar planet HD 189733b". Nature.
447 (7141): 183–186. arXiv:0705.0993 .
^ Bill Christensen. Shock to the (Solar) System: Coronal Mass Ejection
Tracked to Saturn. Retrieved on 28 June 2008.
^ AlaskaReport. What Causes the Aurora Borealis? Retrieved on 28 June
^ Rodney Viereck.
Space Weather: What is it? How Will it Affect
You?[permanent dead link] Retrieved on 28 June 2008.
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