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Thunderstorm near Garajau, Madeira
.Weather is a set of all the phenomena occurring in a given atmosphere at a given time.^ Vermont sets 'all-time record for one snowstorm' .

[1] Most weather phenomena occur in the troposphere,[2][3] just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate is the term for the average atmospheric conditions over longer periods of time.[4] When used without qualification, "weather" is understood to be the weather of Earth.
Weather occurs due to density (temperature and moisture) differences between one place and another. These differences can occur due to the sun angle at any particular spot, which varies by latitude from the tropics. The strong temperature contrast between polar and tropical air gives rise to 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 (100 °F to −40 °F) annually. Over thousands of years, changes in Earth's orbit affect the amount and distribution of solar energy received by the Earth and influence long-term climate
Surface temperature differences in turn cause pressure differences. Higher altitudes are cooler than lower altitudes due to differences in compressional heating. .Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location.^ Time and Weather Current location: Home page > World Clock > Time and Weather Weather around the World .
  • Weather around the World 17 January 2010 8:29 UTC www.timeanddate.com [Source type: Reference]

The atmosphere is a chaotic system, so 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 human history, and there is evidence that human activity such as agriculture and industry has inadvertently modified weather patterns.^ 'It appears from the details of the scandal that there is no relationship whatsoever between human activities and climate change' .

^ S. African UN Scientist on Climategate: 'Never in the history of science has there been such a flagrant disregard for the fundamental requirements of scientific endeavour' .

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.

Contents

Cause

On Earth, 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).[3] Weather does occur in the stratosphere and can affect weather lower down in the troposphere, but the exact mechanisms are poorly understood.[5]
Weather occurs primarily due to density (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 you lie, the lower the sun angle is, which causes those locations to be cooler due to the indirect sunlight.[6] The strong temperature contrast between polar and tropical air gives rise to the jet stream.[7] Weather systems in the mid-latitudes, such as extratropical cyclones, are caused by instabilities of the jet stream flow (see baroclinity).[8] Weather systems in the tropics, such as monsoons or organized thunderstorm systems, are caused by different processes.
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).^ Climate Scare Fading: 'More Americans believe in haunted houses than man-made global warming' - 37% vs. .

^ December 2009: Second Snowiest on Record in the Northern Hemisphere Tom Nelson Cap & trade 'corporate welfare' .

^ 'Obama seems to approach climate issues as nothing more than a 'check box' issue' .

[9] 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.^ Canadian Paper: 'Scandal shakes foundations of climate science...this has set the climate-change debate back 20 years' .

^ 'Hundreds gathered at State Capitol in Madison, Wi to oppose Gore and his alarmist Climate Change policies' .

^ 'Rapid warming in 1990s, culminating in hottest year on record in 1998, was erroneously used to suggest climate change was accelerating' .

(see Milankovitch cycles).[10]
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.[11] .Higher altitudes are cooler than lower altitudes, which is explained by the lapse rate.^ Peer-reviewed Study: 'Annual Greenland temps were higher in 1930 than today..rate of warming in the past was much greater than the current rate of warming' .

[12][13] .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 content.^ Skeptics 'reject man-made climate theory because it reminds them of their own mortality' .

^ More Dissenters: Greek Earth scientists declare: 'There is no reason whatsoever to worry about man-made climate change, because there is no evidence whatsoever that such a thing is happening' .

^ Scientists ask American Physical Society to rescind support for man-made global warming statement .

Surface temperature differences in turn cause pressure differences. A hot surface heats the air above it and the air expands, lowering the air pressure and its density.[14] The resulting horizontal pressure gradient accelerates the air from high to low pressure, creating wind, and Earth's rotation then causes curvature of the flow via the Coriolis effect.[15] 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, so small changes to one part of the system can grow to have large effects on the system as a whole.[16] .This makes it difficult to accurately predict weather more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, meteorology.^ 'On average each day in 1855 more than 50 tons of horse excrement was removed from only one street' .

.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 prediction skill.^ Skeptical UN IPCC Scientist: 'The use of fossil fuels has done more to benefit human kind than anything else since the invention of agriculture' .

^ Aussie Scientist: 'More evidence CO2 not culprit -- 'Climate sensitivity associated with CO2 is less than that used in present climate modelling, by a factor of about 3' .

^ It was fine enough next day, and the Macphails, condemned to spend a fortnight of idleness at Pago-Pago, set about making the best of things.

[17] Chaos theory says that the slightest variation in the motion of the ground can grow with time. This idea is sometimes called the butterfly effect, from the idea that the motions caused by the flapping wings of a butterfly eventually could produce marked changes in the state of the atmosphere. .Because of this sensitivity to small changes, it will never be possible to make perfect forecasts, although there still is much potential for improvement.^ Aussie Paper's Candid Admission: 'There is not, now, much value in arguing about the science of climate change.

The sun and oceans can also affect the weather of land. If the sun heats up ocean waters for a period of time, water can evaporate. Once evaporated into the air, the moisture can spread throughout nearby land, thus making it cooler.

Shaping the planet Earth

Weather is one of the fundamental processes that shape the Earth. The process of weathering breaks down rocks and soils into smaller fragments and then into their constituent substances.[18] These are then free to take part in chemical reactions that can affect the surface further (such as acid rain) or are reformed into other rocks and soils. In this way, weather plays a major role in erosion of the surface.[19]

Effect on humans

Effects on populations

New Orleans, Louisiana, after being struck by Hurricane Katrina. Katrina was a 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.^ 'Scientists were asked to 'beef up' conclusions about climate change and extreme weather events because environmental officials in one country were planning a 'big public splash' .

^ 'It has now gotten to the point that almost any major weather event is blamed by someone on global climate change' .

^ Climate of Change: Gore speech draws more than 200 protesters in Florida -- 'Boos and chants could be heard' during talk .

.One such event is the saving of Japan from invasion by the Mongol fleet of Kublai Khan by the Kamikaze winds in 1281.[20] French claims to Florida came to an end in 1565 when a hurricane destroyed the French fleet, allowing Spain to conquer Fort Caroline.^ Hurricane season ends, one of calmest since 1990's .

[21] 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 States.[22]

Effects on individuals

Though weather affects people in drastic ways, it can also affect the human race in simpler ways. The human body is negatively affected by extremes in temperature, humidity, and wind.[23]

Forecasting

Forecast of surface pressures five days into the future for the north Pacific, North America, and north Atlantic ocean.
.Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location.^ Time and Weather Current location: Home page > World Clock > Time and Weather Weather around the World .
  • Weather around the World 17 January 2010 8:29 UTC www.timeanddate.com [Source type: Reference]

Human beings have attempted to predict the weather informally for millennia, and formally since at least the nineteenth century.[24][25] 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 will evolve.[26]
.Once an all-human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition,[27][28] forecast models are now used to determine future conditions.^ Skeptical Climatologist: 'Who Are The Deniers Now?...'All evidence rejects hypothesis that human CO2 is causing warming' .

^ 'Climate bill establishes emergency conditions requiring the president to step in and use all of his authority over relevant agencies to stop global warming' .

Human input is still required to pick the best possible forecast model to base the forecast upon, which involves 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.[29][30][31]
There are a variety of end users to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property.[32] Forecasts based on temperature and precipitation are important to agriculture,[33][34][35][36] and therefore to commodity traders within stock markets. Temperature forecasts are used by utility companies to estimate demand over coming days.[37][38][39] On an everyday basis, 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 and survive them.

Modification

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.^ When they awoke, though the sky was still grey and the clouds hung low, it was not raining, and they went for a walk on the high road which the Americans had built along the bay.

[40] 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 Beijing in an effort to keep rain away from the opening ceremony of the games on Aug 8, 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 millimeters.[41]
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:[40]
.
.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 health.^ 'Ministers have failed in their campaign to persuade the public that the greenhouse effect is a serious threat requiring urgent action' .

[43].

Extremes on Earth

Early morning sunshine over Bratislava, Slovakia.
The same area, just three hours later, after light snowfall.
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 (−129 °F), at Vostok Station, Antarctica on 21 July 1983. The hottest air temperature ever recorded was 57.7 °C (135.9 °F) at Al 'Aziziyah, Libya, on September 13 1922.[44] The highest recorded average annual temperature was 34.4 °C (93.9 °F) at Dallol, Ethiopia.[45] The coldest recorded average annual temperature was −55.1 °C (−67 °F) at Vostok Station, Antarctica.[46] 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 °F).[47]

Extraterrestrial within the Solar System

Jupiter's Great Red Spot
Studying how the weather works on other planets has been seen as helpful in understanding how it works on Earth.[48] 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.[49] Earth's atmosphere includes six latitudinal circulation zones, three in each hemisphere.[50] In contrast, Jupiter's banded appearance shows many such zones,[51] Titan has a single jet stream near the 50th parallel north latitude,[52] and Venus has a single jet near the equator.[53]
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.[54] 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 kilometres per hour (1,300 mph)) have been measured on the planet Neptune.[55] 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 1/900th of that received by Earth, yet the intensity of weather phenomena on Neptune is far greater than on Earth.^ Man with knife in chest calls 911, orders coffee in diner; 'complained only about the cold weather' .

[56] .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).^ University 'owes the world a more straightforward explanation than it has so far bothered to give' .

^ The Program Code - Perhaps Far More Damning than the Emails .

[57]

Space weather

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. 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.[58] 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,[59] and can play havoc with electrically sensitive systems such as electricity grids and radio signals.[60]

See also

References

  1. ^ Merriam-Webster Dictionary. Weather. Retrieved on 2008-06-27.
  2. ^ Glossary of Meteorology. Hydrosphere. Retrieved on 2008-06-27.
  3. ^ a b Glossary of Meteorology. Troposphere. Retrieved on 2008-06-27.
  4. ^ "Climate". Glossary of Meteorology. American Meteorological Society. http://amsglossary.allenpress.com/glossary/search?id=climate1. Retrieved 2008-05-14. 
  5. ^ O'Carroll, Cynthia M. (2001-10-18). "Weather Forecasters May Look Sky-high For Answers". Goddard Space Flight Center (NASA). http://www.gsfc.nasa.gov/topstory/20011018windsurface.html. 
  6. ^ NASA. World Book at NASA: Weather. Retrieved on 2008-06-27.
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  8. ^ Carlyle H. Wash, Stacey H. Heikkinen, Chi-Sann Liou, and Wendell A. Nuss. A Rapid Cyclogenesis Event during GALE IOP 9. Retrieved on 2008-06-28.
  9. ^ Windows to the Universe. Earth's Tilt Is the Reason for the Seasons! Retrieved on 2008-06-28.
  10. ^ Milankovitch, Milutin. Canon of Insolation and the Ice Age Problem. Zavod za Udz̆benike i Nastavna Sredstva: Belgrade, 1941. Isbn=8617066199.
  11. ^ Ron W. Przybylinski. The Concept of Frontogenesis and its Application to Winter Weather Forecasting. Retrieved on 2008-06-28.
  12. ^ Mark Zachary Jacobson (2005). Fundamentals of Atmospheric Modeling (2nd ed.). Cambridge University Press. ISBN 0-521-83970-X. OCLC 243560910. 
  13. ^ C. Donald Ahrens (2006). Meteorology Today (8th ed.). Brooks/Cole Publishing. ISBN 0-495-01162-2. OCLC 224863929. 
  14. ^ Michel Moncuquet. Relation between density and temperature. Retrieved on 2008-06-28.
  15. ^ Encyclopedia of Earth. Wind. Retrieved on 2008-06-28.
  16. ^ Spencer Weart. The Discovery of Global Warming. Retrieved on 2008-06-28.
  17. ^ [1]
  18. ^ NASA. NASA Mission Finds New Clues to Guide Search for Life on Mars. Retrieved on 2008-06-28.
  19. ^ West Gulf River Forecast Center. Glossary of Hydrologic Terms - E. Retrieved on 2008-06-28.
  20. ^ James P. Delgado. Relics of the Kamikaze. Retrieved on 2008-06-28.
  21. ^ Mike Strong. Fort Caroline National Memorial. Retrieved on 2008-06-28.
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  27. ^ Weather Doctor. Applying The Barometer To Weather Watching. Retrieved on 2008-05-25.
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  29. ^ Klaus Weickmann, Jeff Whitaker, Andres Roubicek and Catherine Smith. The Use of Ensemble Forecasts to Produce Improved Medium Range (3-15 days) Weather Forecasts. Retrieved on 2007-02-16.
  30. ^ Todd Kimberlain. Tropical cyclone motion and intensity talk (June 2007). Retrieved on 2007-07-21.
  31. ^ Richard J. Pasch, Mike Fiorino, and Chris Landsea. TPC/NHC’S REVIEW OF THE NCEP PRODUCTION SUITE FOR 2006. Retrieved on 2008-05-05.
  32. ^ National Weather Service. National Weather Service Mission Statement. Retrieved on 2008-05-25.
  33. ^ Blair Fannin. Dry weather conditions continue for Texas. Retrieved on 2008-05-26.
  34. ^ Dr. Terry Mader. Drought Corn Silage. Retrieved on 2008-05-26.
  35. ^ Kathryn C. Taylor. Peach Orchard Establishment and Young Tree Care. Retrieved on 2008-05-26.
  36. ^ Associated Press. After Freeze, Counting Losses to Orange Crop. Retrieved on 2008-05-26.
  37. ^ The New York Times. FUTURES/OPTIONS; Cold Weather Brings Surge In Prices of Heating Fuels. Retrieved on 2008-05-25.
  38. ^ BBC. Heatwave causes electricity surge. Retrieved on 2008-05-25.
  39. ^ Toronto Catholic Schools. The Seven Key Messages of the Energy Drill Program. Retrieved on 2008-05-25.
  40. ^ a b American Meteorological Society
  41. ^ Huanet, Xin (2008-08-09). "Beijing disperses rain to dry Olympic night". Chinaview. http://news.xinhuanet.com/english/2008-08/09/content_9079637.htm. Retrieved 2008-08-24. 
  42. ^ Intergovernmental Panel on Climate Change
  43. ^ Intergovernmental Panel on Climate Change
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  46. ^ Glenn Elert. Coldest Temperature On Earth. Retrieved on 2008-06-28.
  47. ^ Canadian Climate Normals 1971-2000 - Eureka
  48. ^ Britt, Robert Roy (2001-03-06). "The Worst Weather in the Solar System". Space.com. http://www.space.com/scienceastronomy/solarsystem/solar_system_weather_010306-1.html. 
  49. ^ M. Fulchignoni, F. Ferri, F. Angrilli, A. Bar-Nun, M.A. Barucci, G. Bianchini, W. Borucki, M. Coradini, A. Coustenis, P. Falkner, E. Flamini, R. Grard, M. Hamelin, A.M. Harri, G.W. Leppelmeier, J.J. Lopez-Moreno, J.A.M. McDonnell, C.P. McKay, F.H. Neubauer, A. Pedersen, G. Picardi, V. Pirronello, R. Rodrigo, K. Schwingenschuh, A. Seiff, H. Svedhem, V. Vanzani and J. Zarnecki (2002). "The Characterisation of Titan's Atmospheric Physical Properties by the Huygens Atmospheric Structure Instrument (Hasi)". Space Science Review 104: 395–431. doi:10.1023/A:1023688607077. 
  50. ^ Jet Propulsion Laboratory. [http://sealevel.jpl.nasa.gov/overview/climate-climatic.html OVERVIEW - Climate: The Spherical Shape of the Earth: Climatic Zones.] Retrieved on 2008-06-28.
  51. ^ Anne Minard. Jupiter's "Jet Stream" Heated by Surface, Not Sun. Retrieved on 2008-06-28.
  52. ^ ESA: Cassini-Huygens. The jet stream of Titan. Retrieved on 2008-06-28.
  53. ^ Georgia State University. The Environment of Venus. Retrieved on 2008-06-28.
  54. ^ Ellen Cohen. "Jupiter's Great Red Spot". Hayden Planetarium. http://haydenplanetarium.org/resources/ava/page/index.php?file=P0413jupispot. Retrieved 2007-11-16. 
  55. ^ Suomi, V. E.; Limaye, S. S.; Johnson, D. R. (1991). "High Winds of Neptune: A possible mechanism". Science (AAAS (USA)) 251 (4996): 929–932. doi:10.1126/science.251.4996.929. PMID 17847386. 
  56. ^ Sromovsky, Lawrence A. (1998-10-14). "Hubble Provides a Moving Look at Neptune's Stormy Disposition". HubbleSite. http://hubblesite.org/newscenter/newsdesk/archive/releases/1998/34/text/. 
  57. ^ Knutson, Heather A.; David Charbonneau, Lori E. Allen, Jonathan J. Fortney, Eric Agol, Nicolas B. Cowan, Adam P. Showman, Al, Curtis S. Cooper & S. Thomas Megeath (10 May 2007). "A map of the day–night contrast of the extrasolar planet HD 189733b". Nature 447: 183–186. doi:10.1038/nature05782. http://www.nature.com/nature/journal/v447/n7141/abs/nature05782.html. 
  58. ^ Bill Christensen. Shock to the (Solar) System: Coronal Mass Ejection Tracked to Saturn. Retrieved on 2008-06-28.
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External links


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Contents

Introdution

What is weather? I'm sure your mum always complains about weather in Britain! But weather is more than an excuse to moan. Weather affects our health, culture and evoloution. I'm sure you've heard about thunderstorms, rain, sun etc, but how do they form? This page tells you all you must know about weather.

Atmosphere

The atmosphere is anything between 'the ground' and 'space'. The atmosphere is the driving force of the weather, and is vital for the well-being of all life on Earth. But why?

Layers

The atmosphere is sectioned into different layers. Each layer does different things.

Troposphere

The first layer. It extends to 6km, slightly higher than Everest. This layer holds the Oxygen we need to breathe and this is the place weather forms. Without weather, we would have no rain, how could we live without rain?

Stratosphere

The second layer. Extends from 6-30 miles above us. The Stratosphere is important because The Ozone layer lies in this zone. The Ozone layer protects us from the harmfull rays the sun produces.

Mesosphere

Not just the layer with a catchy name! This layer extends from 30-50 miles. It doesn't really have any specific importance, but without it, our atmosphere would be a lot thinner, meaning less protection from dangers in space.

Thermosphere

This is the last layer of the atmosphere. It extends from 50-310 miles and is the first line of protection against hazards such as meteorites ('space rocks'). There is lots of friction here, which makes it hot enough to burn up most dangers. Temperatures in some areas may be 1000 °c, or even hotter! Past the Thermosphere is 'space'.

The engine behind weather

What is the engine behind weather? There are three important engines: the sun, convection, and pressure.

The Sun

The sun is the main reason why some places are hotter than eachother. Death Valley, Nevada, experienced the hottest recorded temperature on Earth, at a scorching 57°c- that's nearly as hot as your hot tap. The world's coldest recorded temperature was at Vostock station, Antartica, which recorded a temperature of -89- colder than your average day on Mars. Death Valley is near the equator, and Vostock is in Antartica- so the sun must be a big contributer to heat. Earth, although tilted, has a sort of bulge, the equator being at the centre of this 'bulge'. The Artic diameter is much less than the equator's. So in fact, the equator is closer to the sun than Earth. Another common factor that changes temperature is altitude (how high you are)

Convection

Warm air is much less dense (the particles are much more spread out) than cold air. In other words, warm air is lighter than cold air. Because warm air is light, it rises, and because cold air is heavy, it falls. The warm air rises to a certain height and becomes cold again (it gets colder the higher into the atmosphere you go); it may condense (turn into liquid) and become rain. Once the cold air warms up by being close to the surface, it starts rising, completing the cycle. Convection is a great engine of weather.

Air Pressure

Air pressure greatly affects what kind of weather we experience. There are two types of air pressure: high pressure and low pressure.

Low Pressure

This is the type of weather that usually means stormy weather. Warm air is much less dense than cold air, so it rises. As it rises, the air cools, condensing to form clouds. Water vapour condenses in the clouds to form rain.

High Pressure

Although high pressure usually means calm, settled weather, high pressure is usually cooler than low pressure. Cold air is much denser than warm air, so it sinks. You end up with settled, but cool, weather- shame you can't get the best of both!

Types of weather

There are many types of weather that we experience in our daily lives: you sunbathe when it is hot and sunny; and you put your coat on when it rains and becomes cold, we all have a pretty good general idea of weather- but you may not know how they form. We are going to look at the effect of features on local weather.

Wind

We all experience wind. Wind is basicly the movement of air- but how are some winds different to others?

Sea Breezes

The sea takes longer to heat up than land. This makes the air over the land warmer. The warmer land air rises over the sea, and the air above gets replaced by the cooler sea air, creating sea breezes. Land breezes are the reverse, and happen because the sea also takes longer to cool.

Valley and Mountain Winds

The sun heats up the air over Valley Slopes, making the warm air rise, and have a lower pressure than the air at the same level over the valley, creating the breeze. Mountain winds are simply the reverse of Valley Winds.

Precipation

There are a number of types of precipation. Although sometimes we moan about it, it's a very important part of life of about every life form. The types:

Rain

This forms from layered clouds. Clouds, caused by condensation of air, hold small ice droplets, caused by condensed water vapour. When the ice droplets fall through the cloud to a layer above 0°c, the droplets melt into drizzle or rain.

Drizzle

Simply rain, but with smaller water droplets.

Hail

In thunderclouds, ice droplets falling may be caught in strong updrafts, they collide with many other ice droplets, growing larger and larger. Some hailstones may be bigger than golfballs and may damage cars.

Snow

If it is really cold, the ice droplets may not melt as they fall through the clouds, so they land as snow. The temperature effects what the snow is like: the shape and hardness.

Sleet

Sleet are small drops of snow like drizzle is small drops of rain. This is when rain falls through cold cloud (below 0°c), sleet is kind of between rain and snow.

Frost

Frost is the cold white sheets on grass, and gives a beautiful crispy texture. There are two types of frost:
Hoar Frost
This is the most common type of frost and forms in two ways:
1. Dew freezes on grass and other surfaces
2. Water vapour freezes before turning into Dew.
Rime Frost
Less common. This is when liquid water below freezing point (0°c) in fog touch a surface below freezing point and finally freezes into ice.

Thunderstorms

There is something about a Thunderstorm that fascinates; perhaps the boom of a thundercloud, or maybe the danger of a lightning strike.

Which comes first

A good way of remembering the speed of light and sound is to remember the famous phrase: 'which came first: the thunder or the lightning?'
How far away...
Light travels at an astonishing 186,282 miles per second! So we see lightning almost as it happens. But sound travels much slower (but it's still very fast). To estimate how far away lightning is, count the number of seconds between seeing the lightning and hearing the thunder. Divide by 5 to discover the distance by miles (or by 3 for km).

How they are formed

The stages of a thunderstorm.
1. A Cumulus cloud grows. Updrafts develop, preventing precipation from falling.
2. Downdrafts develop, precipation forms. Wind, thunder, and lightning occur.
3. Downdrafts cut off updrafts. Cloud begins to collapse. Precipation stops. Other clouds may form over the shrinking cloud.

Fog

Fog is formed when the air becomes saturated. Water vapour comes in contact with the ground, condensing to form fog.
NOTE: Mist is light fog

Types of fog

There are a number of types of fog. These include Advection fog. This is when warm ocean air is blown accross a colder landmass, the vapour falls onto the land. (see convection) Dew is the moisture that can be seen on grass or other surfaces on those cold mornings. Like fog, it forms within contact with the ground, direct contact in this case.

Rainbows

Rainbows are present when the sun is out and it is raining at the same time. The science of a rainbow is quite complicated: put simply, sunlight rebounds of the raindrops, extracting all the sunlight's colours, forming the famous bow.

Quiz

2005-09-22-10PM CDT Hurricane Rita 3 day path.gif

1. What part of the map do the storm warnings seem to be centred?
2. In which direction is the Hurricane moving in?
3. Using the scale, how far does the storm seem to be moving in a day;
4. What does this mean about the speed?

Answers

1. The coast/ beach
2. North
3. 250 miles
4. Roughly 10mph

References

Weather, Reader's Digest

External Links

Main Articles


Simple English

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Thunderstorms are a kind of weather.

Weather is what is happening in the sky above us. Weather includes (but is not limited to) wind, lightning, storms, hurricanes, tornados, rain, hail, and snow. Energy from the sun affects the weather. Climate tells us what kinds of weather usually happen in an area at different times of the year. Changes in weather can affect our mood. We wear different clothes and take part in different activities under different weather conditions. We choose different foods in different seasons.

Weather stations around the world measure different parts of weather. Ways to measure are wind speed, wind direction, temperature , barometric pressure, and humidity. People try to use these measurements to determine what the weather will be like in the future. These people are called meteorologists.

Bad weather can cause loss of life and property. It can also affect our daily life. Some examples of bad weather:

Other websites

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Citable sentences

Up to date as of December 29, 2010

Here are sentences from other pages on Climate, which are similar to those in the above article.








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