| Weather is a set of all the phenomena occurring in a given atmosphere at a given time. When used without qualification, "weather" is understood to be the weather of Earth.
Weather occurs due to density (temperature and moisture) differences
influence long-term climate
Surface temperature
technology to predict the state of the atmosphere for a future time and a given location. 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.
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.
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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 and ice storms. Almost all familiar weather phenomena occur in the troposphere (the lower part of the atmosphere).
Weather occurs primarily due to density (temperature and moisture)
is, which causes those locations to be cooler due to the indirect sunlight. 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).
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. 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.
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. 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. 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,
improvement.
The sun and oceans
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.
fragments and then into their constituent substances.
Effect on humans
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
destroyed the French fleet, allowing Spain to conquer Fort Caroline.
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.
Forecasting
Weather forecasting is the application of science and technology to predict the state of the atmosphere
least the nineteenth century.
Once an all-human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition, forecast models
most likely outcome.
There are a variety of end users to weather forecasts. Weather
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. A recent example of weather control was China's preparation for the 2008 Summer Olympic Games.
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.
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:
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..
Extremes on Earth
On Earth, temperatures usually range ±40 °C (100 °F to −40 °F)
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.
Extraterrestrial within the Solar System
Studying how the weather works on other planets has been seen as helpful in understanding how it works on Earth.
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.
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. This has created a puzzle for planetary scientists.
than on Earth.
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,
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.
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