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Weather refers to the state of the Earth'satmosphere at a specific place and time, typically described in terms of temperature, humidity,cloud cover, andstability. OnEarth, most weather phenomena occur in the lowest layer of the planet'satmosphere, thetroposphere, just below thestratosphere. Weather refers to day-to-day temperature,precipitation, and other atmospheric conditions, whereasclimate 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 of Earth.
Weather is driven byair pressure,temperature, andmoisture differences between one place and another. These differences can occur due to theSun's angle at any particular spot, which varies withlatitude. The strong temperature contrast between polar and tropical air gives rise to the largest scaleatmospheric circulations: theHadley cell, theFerrel cell, thepolar cell, and thejet stream. Weather systems in themiddle latitudes, such asextratropical cyclones, are caused by instabilities of the jet streamflow. Because Earth'saxis is tilted relative to itsorbital plane (called theecliptic),sunlight is incident atdifferent angles at different times of the year. On Earth's surface, temperatures usually range ±40 °C (−40 °F to 104 °F) annually. Over thousands of years, changes in Earth'sorbit can affect the amount and distribution ofsolar energy received by Earth, thus influencing long-term climate and globalclimate 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 theatmosphere for a future time and a given location. Earth's weather system is achaotic 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 tocontrol the weather have occurred throughout history, and there is evidence thathuman 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 theSolar System, Jupiter'sGreat Red Spot, is ananticyclonic storm known to have existed for at least 300 years. However, the weather is not limited to planetary bodies. Astar'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 theSun is known as thesolar wind. (Full article...)
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Flakes ofsnow highly magnified by a low-temperaturescanning electron microscope (SEM). The colors are called "pseudo colors"; they are computer generated and are a standard technique used with SEM images.
Recently selected pictures:Sun dog,Pyrocumulus clouds,Cloud-to-cloud lightning,More...
...that theFlying river is the name given to the transport ofwater vapor from theAmazon rainforest to southernBrazil?
...thathurricane shutters are required for all homes inFlorida unless impact-resistant glass is used?
...that theJoint Institute for Marine and Atmospheric Research is a combined weather and ocean research institute with the cooperation of theOffice of Oceanic and Atmospheric Research and theUniversity of Hawaiʻi?
...that theSS Central America was sunk by ahurricane while carrying more than 30,000 pounds (13,600 kg) of gold, contributing to thePanic of 1857?
...that ahurricane force wind warning is issued by theUnited StatesNational Weather Service for storms that are nottropical cyclones but are expected to produce hurricane-force winds (65 knots (75 mph; 120 km/h) or higher)?
...that theAutomated Tropical Cyclone Forecasting System is a software package fortropical cycloneforecasting developed in 1988 that is still used today bymeteorologists in various branches of theUS Government?
1996:Hurricane Marco, the longest-livedtropical cyclone ever recorded in theAtlantic Ocean in November, reached its peak intensity while meandering over theCaribbean Sea.
1992: Athree-day tornado outbreak began in theSouthern United States, eventually producing sixF4tornadoes, two tornadoes with paths of more than 100 miles (161 km), and 26 deaths.
2020:Cyclone Gati, the strongesttropical cyclone on record to strikeSomalia, madelandfall nearHafun, killing 9 people.
1960: TheTIROS-2weather satellite was launched fromCape Canaveral,Florida.
1982:Hurricane Iwa, one of the strongesttropical cyclones in history todirectly affect Hawaii, passed just northwest ofKauai.
2007:Typhoon Mitag made landfall in northernLuzon,Philippines, causing major flooding that killed 67 people.
1898: A powerfulstorm system killed over 400 people and sank 150 ships over the next two days along the coast ofNew England.
Wladimir Petrovich Köppen (/ˈkɜːpən/KUR-pən;German:[ˈkœpn̩];Russian:Влади́мир Петро́вич Кёппен,romanized: Vladímir Petróvich Kyoppen,IPA:[vlɐˈdʲimʲɪrpʲɪˈtrovʲɪtɕˈkʲɵp(ː)ʲɪn]; 25 September 1846 – 22 June 1940) was aRussian–Germangeographer,meteorologist,climatologist andbotanist. After studies inSt. Petersburg, he spent the bulk of his life and professional career inGermany andAustria. TheKöppen climate classification system, named after a proposal he first made in 1884, with some modifications, is still widely used. Köppen made significant contributions to several branches of science, and coined the nameaerology for the science of the upper atmosphere. (Full article...)
Previously selected biographies:John Park Finley,Edward Norton Lorenz,More...
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The scope ofWikiProject Weather is to have a single location for all weather-related articles on Wikipedia.
WikiProject Meteorology is a collaborative effort by dozens of Wikipedians to improve the quality ofmeteorology- andweather-related articles. If you would like to help, visit theproject talk page, and see what needs doing.
WikiProject Severe weather is a similar project specific to articles aboutsevere weather. Their talk page is locatedhere.
WikiProject Tropical cyclones is a daughter project of WikiProject meteorology. The dozens of semi-active members and several full-time members focus on improving Wikipedia's coverage oftropical cyclones.
WikiProject Non-tropical storms is a collaborative project to improve articles related to winter storms, wind storms, and extratropical cyclones.
Wikipedia is a fully collaborative effort by volunteers. So if you see something you think you can improve,be bold and get to editing! We appreciate any help you can provide!
The followingWikimedia Foundation sister projects provide more on this subject:
