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65-402: 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 . On Earth , most weather phenomena occur in the lowest layer of the planet's atmosphere , the troposphere , just below the stratosphere . Weather refers to day-to-day temperature, precipitation , and other atmospheric conditions, whereas climate

130-421: 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 prediction skill. Weather is one of the fundamental processes that shape

195-457: A fuel. They need to have a relatively low water content for combustion efficiency . The more moisture that is allowed in the pellet, the more smoke that will be released when the pellet is burned. The need to measure water content of products has given rise to a new area of science, aquametry . There are many ways to measure moisture in products, such as different wave measurement (light and audio), electromagnetic fields , capacitive methods, and

260-401: 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 them. Tropical weather forecasting is different from that at higher latitudes. The sun shines more directly on the tropics than on higher latitudes (at least on average over a year), which makes

325-709: A moon of Saturn, and Triton , a moon of Neptune, have atmospheres mainly of nitrogen . When in the part of its orbit closest to the Sun, Pluto has an atmosphere of nitrogen and methane similar to Triton's, but these gases are frozen when it is farther from the Sun. Other bodies within the Solar System have extremely thin atmospheres not in equilibrium. These include the Moon ( sodium gas), Mercury (sodium gas), Europa (oxygen), Io ( sulfur ), and Enceladus ( water vapor ). The first exoplanet whose atmospheric composition

390-508: A planet from atmospheric escape and that for some magnetizations the presence of a magnetic field works to increase the escape rate. Other mechanisms that can cause atmosphere depletion are solar wind -induced sputtering, impact erosion, weathering , and sequestration—sometimes referred to as "freezing out"—into the regolith and polar caps . Atmospheres have dramatic effects on the surfaces of rocky bodies. Objects that have no atmosphere, or that have only an exosphere, have terrain that

455-520: 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 giant planets , 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

520-451: A variable amount of water vapor is also present, on average about 1% at sea level. The low temperatures and higher gravity of the Solar System's giant planets — Jupiter , Saturn , Uranus and Neptune —allow them more readily to retain gases with low molecular masses . These planets have hydrogen–helium atmospheres, with trace amounts of more complex compounds. Two satellites of the outer planets possess significant atmospheres. Titan ,

585-434: A vital part of the process of the product. There is a substantial amount of moisture in what seems to be dry matter . Ranging in products from cornflake cereals to washing powders , moisture can play an important role in the final quality of the product. There are two main aspects of concern in moisture control in products: allowing too much moisture or too little of it. For example, adding some water to cornflake cereal, which

650-464: A wide range of velocities, there will always be some fast enough to produce a slow leakage of gas into space. Lighter molecules move faster than heavier ones with the same thermal kinetic energy , and so gases of low molecular weight are lost more rapidly than those of high molecular weight. It is thought that Venus and Mars may have lost much of their water when, after being photodissociated into hydrogen and oxygen by solar ultraviolet radiation,

715-423: Is covered in craters . Without an atmosphere, the planet has no protection from meteoroids , and all of them collide with the surface as meteorites and create craters. For planets with a significant atmosphere, most meteoroids burn up as meteors before hitting a planet's surface. When meteoroids do impact, the effects are often erased by the action of wind. Wind erosion is a significant factor in shaping

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780-478: 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. 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

845-625: Is originally determined by the stellar nebula's chemistry and temperature, but can also by a product processes within the astronomical body outgasing a different atmosphere. The atmospheres of the planets Venus and Mars are principally composed of carbon dioxide and nitrogen , argon and oxygen . The composition of Earth's atmosphere is determined by the by-products of the life that it sustains. Dry air (mixture of gases) from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally

910-524: Is sold by weight, reduces costs and prevents it from tasting too dry, but adding too much water can affect the crunchiness of the cereal and the freshness because water content contributes to bacteria growth. Water content of some foods is also manipulated to reduce the number of calories . Moisture has different effects on different products, influencing the final quality of the product. Wood pellets , for instance, are made by taking remainders of wood and grinding them to make compact pellets, which are sold as

975-401: Is the lowest layer of the atmosphere. This extends from the planetary surface to the bottom of the stratosphere . The troposphere contains 75–80% of the mass of the atmosphere, and is the atmospheric layer wherein the weather occurs; the height of the troposphere varies between 17 km at the equator and 7.0 km at the poles. The stratosphere extends from the top of the troposphere to

1040-641: 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

1105-586: 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. On Earth, temperatures usually range ±40 °C (100 °F to −40 °F) annually. The range of climates and latitudes across

1170-525: 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 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

1235-420: 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

1300-447: Is used to make nucleotides and amino acids ; plants , algae , and cyanobacteria use carbon dioxide for photosynthesis . The layered composition of the atmosphere minimises the harmful effects of sunlight , ultraviolet radiation, solar wind , and cosmic rays and thus protects the organisms from genetic damage. The current composition of the atmosphere of the Earth is the product of billions of years of biochemical modification of

1365-465: 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 tidal waves or eclipses. Although it is difficult to accurately predict weather more than

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1430-695: The Virgin Islands . As of 2019, tornadoes have had the greatest impact on humans with 42 fatalities while costing crop and property damage over 3 billion dollars. The 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

1495-646: 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 human-made objects) have differing physical characteristics such as reflectivity , roughness, or moisture content. Surface temperature differences in turn cause pressure differences. A hot surface warms

1560-765: The jet stream flow (see baroclinity ). 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 ). This effect causes seasons. Over thousands to hundreds of thousands of years, changes in Earth's orbital parameters affect

1625-477: The paleoatmosphere by living organisms. Atmospheres are clouds of gas bound to and engulfing an astronomical focal point of sufficiently dominating mass , adding to its mass, possibly escaping from it or collapsing into it. Because of the latter, such planetary nucleus can develop from interstellar molecular clouds or protoplanetary disks into rocky astronomical objects with varyingly thick atmospheres, gas giants or fusors . Composition and thickness

1690-477: The solar wind with the terrestrial atmosphere can produce spectacular aurorae , and can play havoc with electrically sensitive systems such as electricity grids and radio signals. Atmosphere The atmosphere of Earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. Most organisms use oxygen for respiration ; lightning and bacteria perform nitrogen fixation which produces ammonia that

1755-439: 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

1820-583: The Middle Ages. Finland suffered a severe famine in 1696–1697, during which about one-third of the Finnish population died. 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 century. Weather forecasts are made by collecting quantitative data about

1885-532: 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 airflow 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

1950-525: 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 is the result of higher surface temperature and radiational heating, which produces

2015-475: The appearance of life and its evolution . Moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Moisture is defined as water in the adsorbed or absorbed phase. Small amounts of water may be found, for example, in the air ( humidity ), in foods, and in some commercial products. Moisture also refers to the amount of water vapor present in the air. The soil also includes moisture. Control of moisture in products can be

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2080-438: The atmosphere can transport thermal energy from the higher temperature interior up to the surface. From the perspective of a planetary geologist , the atmosphere acts to shape a planetary surface. Wind picks up dust and other particles which, when they collide with the terrain, erode the relief and leave deposits ( eolian processes). Frost and precipitations , which depend on the atmospheric composition, also influence

2145-411: The base of the exosphere at 690 km and contains the ionosphere , where solar radiation ionizes the atmosphere. The density of the ionosphere is greater at short distances from the planetary surface in the daytime and decreases as the ionosphere rises at night-time, thereby allowing a greater range of radio frequencies to travel greater distances. The exosphere begins at 690 to 1,000 km from

2210-428: The bottom of the mesosphere , and contains the ozone layer , at an altitude between 15 km and 35 km. It is the atmospheric layer that absorbs most of the ultraviolet radiation that Earth receives from the Sun. The mesosphere ranges from 50 km to 85 km and is the layer wherein most meteors are incinerated before reaching the surface. The thermosphere extends from an altitude of 85 km to

2275-429: The current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve. 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

2340-674: 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

2405-426: The diminishing mass of the gas above the point of barometric measurement. The units of air pressure are based upon the standard atmosphere (atm), which is 101,325  Pa (equivalent to 760  Torr or 14.696  psi ). The height at which the atmospheric pressure declines by a factor of e (an irrational number equal to 2.71828) is called the scale height ( H ). For an atmosphere of uniform temperature,

2470-431: The distance from the Sun determines the energy available to heat atmospheric gas to the point where some fraction of its molecules' thermal motion exceed the planet's escape velocity , allowing those to escape a planet's gravitational grasp. Thus, distant and cold Titan , Triton , and Pluto are able to retain their atmospheres despite their relatively low gravities. Since a collection of gas molecules may be moving at

2535-404: The effect it has on humans in different situations, etc. Therefore, weather is something people often communicate about. The National Weather Service has an annual report for fatalities, injury, and total damage costs which include crop and property. They gather this data via National Weather Service offices located throughout the 50 states in the United States as well as Puerto Rico , Guam , and

2600-464: The forecast upon, which involves 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, the error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as of

2665-853: The greatest snowfall in a period of twelve months occurred in Mount Rainier , Washington, US. It was recorded as 31,102 mm (102.04 ft) of snow. 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

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2730-672: The history of the United States. The Little Ice Age caused crop failures and famines in Europe. During the period known as the Grindelwald Fluctuation (1560–1630), volcanic forcing events seem to have led to more extreme weather events. These included droughts, storms and unseasonal blizzards, as well as causing the Swiss Grindelwald Glacier to expand. The 1690s saw the worst famine in France since

2795-442: The hydrogen escaped. Earth's magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen. The net effect, taking the most important escape processes into account, is that an intrinsic magnetic field does not protect

2860-461: The largest scale atmospheric circulations : the Hadley cell , the Ferrel cell , the polar cell , and the jet stream . Weather systems in the middle latitudes , such as extratropical cyclones , are caused by instabilities of the jet streamflow. Because Earth's axis is tilted relative to its orbital plane (called the ecliptic ), sunlight is incident at different angles at different times of

2925-406: The past. The circulation of the atmosphere occurs due to thermal differences when convection becomes a more efficient transporter of heat than thermal radiation . On planets where the primary heat source is solar radiation, excess heat in the tropics is transported to higher latitudes. When a planet generates a significant amount of heat internally, such as is the case for Jupiter , convection in

2990-414: 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. As of 2007, the strongest planetary winds discovered are on the extrasolar planet HD 189733 b , which

3055-500: 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

3120-416: The relief. Climate changes can influence a planet's geological history. Conversely, studying the surface of the Earth leads to an understanding of the atmosphere and climate of other planets. For a meteorologist , the composition of the Earth's atmosphere is a factor affecting the climate and its variations. For a biologist or paleontologist , the Earth's atmospheric composition is closely dependent on

3185-468: The scale height is proportional to the atmospheric temperature and is inversely proportional to the product of the mean molecular mass of dry air, and the local acceleration of gravity at the point of barometric measurement. Surface gravity differs significantly among the planets. For example, the large gravitational force of the giant planet Jupiter retains light gases such as hydrogen and helium that escape from objects with lower gravity. Secondly,

3250-534: 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. Microscale meteorology

3315-535: 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 surface. 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,

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3380-399: 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

3445-413: The surface, and extends to roughly 10,000 km, where it interacts with the magnetosphere of Earth. Atmospheric pressure is the force (per unit-area) perpendicular to a unit-area of planetary surface, as determined by the weight of the vertical column of atmospheric gases. In said atmospheric model, the atmospheric pressure , the weight of the mass of the gas, decreases at high altitude because of

3510-417: The terrain of rocky planets with atmospheres, and over time can erase the effects of both craters and volcanoes . In addition, since liquids cannot exist without pressure, an atmosphere allows liquid to be present at the surface, resulting in lakes , rivers and oceans . Earth and Titan are known to have liquids at their surface and terrain on the planet suggests that Mars had liquid on its surface in

3575-410: The tropics can occur more spontaneously compared to those at higher latitudes, where they are more tightly controlled by larger-scale forces in the atmosphere. Because of these differences, clouds and rain are more difficult to forecast in the tropics than at higher latitudes. On the other hand, the temperature is easily forecast in the tropics, because it does not change much. The aspiration to control

3640-419: The tropics warm (Stevens 2011). And, the vertical direction (up, as one stands on the Earth's surface) is perpendicular to the Earth's axis of rotation at the equator, while the axis of rotation and the vertical are the same at the pole; this causes the Earth's rotation to influence the atmospheric circulation more strongly at high latitudes than low latitudes. Because of these two factors, clouds and rainstorms in

3705-451: 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 to 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 stream . Weather systems in the mid-latitudes, such as extratropical cyclones , are caused by instabilities of

3770-409: 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 from one place to another. These differences can occur due to the sun angle at any particular spot, which varies by latitude in

3835-420: 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,

3900-602: 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

3965-514: The 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 . 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

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4030-447: The year. On Earth's surface, temperatures usually range ±40 °C (−40 °F to 104 °F) annually. Over thousands of years, changes in Earth's orbit can affect the amount and distribution of solar energy received by 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

4095-561: 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 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

4160-461: Was determined is HD 209458b , a gas giant with a close orbit around a star in the constellation Pegasus . Its atmosphere is heated to temperatures over 1,000 K, and is steadily escaping into space. Hydrogen, oxygen, carbon and sulfur have been detected in the planet's inflated atmosphere. The atmosphere of Earth is composed of layers with different properties, such as specific gaseous composition, temperature, and pressure. The troposphere

4225-517: 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). The windiest place ever recorded is in Antarctica, Commonwealth Bay (George V Coast). Here the gales reach 199 mph (320  km/h ). Furthermore,

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