Wind

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Wind

Wind, from the Tacuinum Sanitatis

A breeze lifts a veil Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space. Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them, the regions in which they occur, and their effect. The strongest observed winds on a planet in our solar system occur on Neptune and Saturn. In meteorology, winds are often referred to according to their strength, and the direction from which the wind is blowing. Short bursts of high speed wind are termed gusts. Strong winds of intermediate duration (around one minute) are termed squalls. Long-duration winds have various names associated with their average strength, such as breeze, gale, storm, hurricane, and typhoon. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet (Coriolis effect). Within the tropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can dominate local winds. In human civilization, wind has inspired mythology, influenced the events of history, expanded the range of transport and warfare, and provided a power source for mechanical work, electricity and recreation. Wind powers the voyages of sailing ships across Earth's oceans. Hot air balloons use the wind to take short trips, and powered flight uses it to increase lift and reduce fuel consumption. Areas of wind shear caused by various weather phenomena can lead to dangerous situations for aircraft. When winds become strong, trees and man-made structures are damaged or destroyed. Winds can shape landforms, via a variety of aeolian processes such as the formation of fertile soils, such as loess, and by erosion. Dust from large deserts can be moved great distances from its source region by the prevailing winds; winds that are accelerated by rough topography and associated with dust outbreaks have been assigned regional names in various parts of the world because of their significant effects on those regions. Wind affects the spread of wildfires. Winds disperse seeds from various plants, enabling the survival and dispersal of those plant species, as well as flying insect populations. When combined with cold temperatures, wind has a negative impact on livestock. Wind affects animals' food stores, as well as their hunting and defensive strategies.

Cause[edit]

See also: Atmospheric pressure

Surface analysis of Great Blizzard of 1888. Areas with greater isobaric packing indicate higher winds. Wind is caused by differences in atmospheric pressure. When a difference in atmospheric pressure exists, air moves from the higher to the lower pressure area, resulting in winds of various speeds. On a rotating planet, air will also be deflected by the Coriolis effect, except exactly on the equator. Globally, the two major driving factors of large-scale wind patterns (the atmospheric circulation) are the differential heating between the equator and the poles (difference in absorption of solar energy leading to buoyancy forces) and the rotation of the planet. Outside the tropics and aloft from frictional effects of the surface, the large-scale winds tend to approach geostrophic balance. Near the Earth's surface, friction causes the wind to be slower than it would be otherwise. Surface friction also causes winds to blow more inward into low pressure areas.[1] A new, controversial theory, suggests atmospheric gradients are caused by forest induced water condensation resulting in a positive feedback cycle of forests drawing moist air from the coastline.[2] Winds defined by an equilibrium of physical forces are used in the decomposition and analysis of wind profiles. They are useful for simplifying the atmospheric equations of motion and for making qualitative arguments about the horizontal and vertical distribution of winds. The geostrophic wind component is the result of the balance between Coriolis force and pressure gradient force. It flows parallel to isobars and approximates the flow above the atmospheric boundary layer in the midlatitudes.[3] The thermal wind is the difference in the geostrophic wind between two levels in the atmosphere. It exists only in an atmosphere with horizontal temperature gradients.[4] The ageostrophic wind component is the difference between actual and geostrophic wind, which is responsible for air "filling up" cyclones over time.[5] The gradient wind is similar to the geostrophic wind but also includes centrifugal force (or centripetal acceleration).[6] It is possible for wind to go in a downwards direction. This is known to cause serious injuries, in some cases death.[citation needed] Measurement[edit]

A windmill style of anemometer

An occluded mesocyclone tornado (Oklahoma, May 1999) Wind direction is usually expressed in terms of the direction from which it originates. For example, a northerly wind blows from the north to the south.[7] Weather vanes pivot to indicate the direction of the wind.[8] At airports, windsocks indicate wind direction, and can also be used to estimate wind speed by the angle of hang.[9] Wind speed is measured by anemometers, most commonly using rotating cups or propellers. When a high measurement frequency is needed (such as in research applications), wind can be measured by the propagation speed of ultrasound signals or by the effect of ventilation on the resistance of a heated wire.[10] Another type of anemometer uses pitot tubes that take advantage of the pressure differential between an inner tube and an outer tube that is exposed to the wind to determine the dynamic pressure, which is then used to compute the wind speed.[11] Sustained wind speeds are reported globally at a 10 meters (33 ft) height and are averaged over a 10 minute time frame. The United States reports winds over a 1 minute average for tropical cyclones,[12] and a 2 minute average within weather observations.[13] India typically reports winds over a 3 minute average.[14] Knowing the wind sampling average is important, as the value of a one-minute sustained wind is typically 14% greater than a ten-minute sustained wind.[15] A short burst of high speed wind is termed a wind gust, one technical definition of a wind gust is: the maxima that exceed the lowest wind speed measured during a ten-minute time interval by 10 knots (19 km/h). A squall is a doubling of the wind speed above a certain threshold, which lasts for a minute or more. To determine winds aloft, rawinsondes determine wind speed by GPS, radio navigation, or radar tracking of the probe.[16] Alternatively, movement of the parent weather balloon position can be tracked from the ground visually using theodolites.[17] Remote sensing techniques for wind include SODAR, Doppler LIDARs and RADARs, which can measure the Doppler shift of electromagnetic radiation scattered or reflected off suspended aerosols or molecules, and radiometers and radars can be used to measure the surface roughness of the ocean from space or airplanes. Ocean roughness can be used to estimate wind velocity close to the sea surface over oceans. Geostationary satellite imagery can be used to estimate the winds throughout the atmosphere based upon how far clouds move from one image to the next. Wind Engineering describes the study of the effects of the wind on the built environment, including buildings, bridges and other man-made objects.

Climate change From Wikipedia, the free encyclopedia

For current and future climatological effects of human influences, see global warming. For the study of past climate change, see paleoclimatology. For temperatures on the longest time scales, see geologic temperature record. Page semi-protected Atmospheric sciences ShipTracks MODIS 2005may11.jpg Atmospheric physics Atmospheric dynamics (category) Atmospheric chemistry (category) Meteorology Weather (category) · (portal) Tropical cyclone (category) Climatology Climate (category) Climate change (category) Global warming (category) · (portal) vte Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions, or in the distribution of weather around the average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as "global warming".[1] Scientists actively work to understand past and future climate by using observations and theoretical models. A climate record — extending deep into the Earth's past — has been assembled, and continues to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. General circulation models, based on the physical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.

Ocean From Wikipedia, the free encyclopedia For other uses, see Ocean (disambiguation).

Surface of the Atlantic ocean meeting the Earth's planetary boundary layer and troposphere.

Waves on an ocean coast. File:The Ocean - a driving force for Weather and Climate.ogv

This animation uses Earth science data from a variety of sensors on NASA Earth observing satellites to measure physical oceanography parameters such as ocean currents, ocean winds, sea surface height and sea surface temperature. View of the Earth where all five oceans visible Earth's oceans Arctic Pacific Atlantic Indian Southern (proposed) World Ocean vte An ocean (from Ancient Greek Ὠκεανός (Okeanos); the World Ocean of classical antiquity*1+) is a body of saline water that composes much of a planet's hydrosphere.[2] On Earth, an ocean is one or all of the

major divisions of the planet's World Ocean – which are, in descending order of area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans.[3][4] The word sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the World Ocean) that land partly or fully encloses.[5] Earth is the only planet that is known to have an ocean (or any large amounts of open liquid water). Saline water covers approximately 72% of the planet's surface (~3.6x108 km2) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of the Earth's surface.[6] The ocean contains 97% of the Earth's water, and oceanographers have stated that only 5% of the World Ocean has been explored.[6] The total volume is approximately 1.3 billion cubic kilometres (310 million cu mi)[7] with an average depth of 3,682 metres (12,080 ft).[8] The ocean principally comprises Earth's hydrosphere and therefore is integral to all known life, forms part of the carbon cycle, and influences climate and weather patterns. It is the habitat of 230,000 known species, although much of the ocean's depths remain unexplored, and over two million marine species are estimated to exist.[9] The origin of Earth's oceans remains unknown; oceans are believed to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds. The only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their geologic histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, and a runaway greenhouse effect may have boiled away the global ocean of Venus. Compounds such as salts and ammonia dissolved in water lower its freezing point, so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many dwarf planets and natural satellites; notably, the ocean of Europa is believed to have over twice the water volume of Earth. The Solar System's gas giant planets are also believed to possess liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of liquid water within a circumstellar habitable zone. Ocean planets are a hypothetical type of planet with a surface completely covered with liquid.[10][11] Contents [hide] 1 Earth's global ocean 1.1 Divisions 1.2 Physical properties 1.3 Zones and depths 1.4 Exploration 1.5 Climate

1.6 Biology 1.7 Economic value 2 Extraterrestrial oceans 2.1 Planets 2.2 Natural satellites 2.3 Dwarf planets and trans-Neptunian objects 2.4 Extrasolar 3 See also 4 References 5 Further reading 6 External links Earth's global ocean[edit]

Divisions[edit] Further information: Borders of the oceans Rotating series of maps showing alternate divisions of the oceans

Various ways to divide the World Ocean Though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean.[11][12] This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.[13] The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria. See the table below for more information; note that the table is in descending order in terms of size.[11][14] Rank 1 Ocean Notes Pacific Ocean Separates Asia and Oceania from the Americas[14]

2 3

Atlantic Ocean Separates the Americas from Eurasia and Africa Indian Ocean Washes upon southern Asia and separates Africa and Australia[14][15][16]

4 Southern Ocean Sometimes considered an extension of the Pacific, Atlantic and Indian Oceans,[11][17] which encircles Antarctica 5 Arctic Ocean Sometimes considered a sea of the Atlantic, which covers much of the Arctic and washes upon northern North America and Eurasia The Pacific and Atlantic may be further subdivided by the equator into northern and southern portions. A smaller region of the ocean can be called other names, such as sea, gulf, bay, and strait. Physical properties[edit] Further information: Seawater The total mass of the hydrosphere is about 1,400,000,000,000,000,000 metric tons (1.5×1018 short tons) or 1.4×1021 kg, which is about 0.023 percent of the Earth's total mass. Less than 3 percent is freshwater; the rest is saltwater, mostly in the ocean. The area of the World Ocean is 361 million square kilometres (139 million square miles),[18] and its volume is approximately 1.3 billion cubic kilometres (310 million cu mi).[7] This can be thought of as a cube of water with an edge length of 1,111 kilometres (690 mi). Its average depth is 3,790 metres (12,430 ft), and its maximum depth is 10,923 metres (6.787 mi).[18] Nearly half of the world's marine waters are over 3,000 metres (9,800 ft) deep.[12] The vast expanses of deep ocean (anything below 200 metres (660 ft)) cover about 66% of the Earth's surface.[19] This does not include seas not connected to the World Ocean, such as the Caspian Sea. The bluish color of water is a composite of several contributing agents. Prominent contributors include dissolved organic matter and chlorophyll.[20] Sailors and other mariners have reported that the ocean often emits a visible glow, or luminescence, which extends for miles at night. In 2005, scientists announced that for the first time, they had obtained photographic evidence of this glow.[21] It is most likely caused by bioluminescence.[22][23][24] Zones and depths[edit] Drawing showing divisions according to depth and distance from shore

The major oceanic divisions Oceanographers divide the ocean into different zones by physical and biological conditions. The pelagic zone includes all open ocean and comprises further regions of depth and light abundance. The photic zone falls two-hundred meters below the oceanic surface and is where photosynthesis can occur and therefore the most biodiverse. Plants require photosynthesis: deeper life relies on material sinking from above (see marine snow) or another energy source. Hydrothermal vents are the primary source in what

is known as the aphotic zone (depths exceeding 200 m). The pelagic part of the photic zone is known as the epipelagic. The pelagic part of the aphotic zone comprises regions that descend in vertical order according to temperature. The mesopelagic is the uppermost region. Its lowermost boundary is at a thermocline of 12 °C (54 °F), which, in the tropics generally lies at 700–1,000 metres (2,300–3,300 ft). Next is the bathypelagic lying between 10 and 4 °C (50 and 39 °F), typically between 700–1,000 metres (2,300– 3,300 ft) and 2,000–4,000 metres (6,600–13,000 ft) Lying along the top of the abyssal plain is the abyssopelagic, whose lower boundary lies at about 6,000 metres (20,000 ft). The last zone includes the deep oceanic trench, and is known as the hadalpelagic. This lies between 6,000–11,000 metres (20,000– 36,000 ft) and is the deepest oceanic zone. The benthic zones are aphotic and correspond to the three deepest zones of the deep-sea. The bathyal zone covers the continental slope down to about 4,000 metres (13,000 ft). The abyssal zone covers the abyssal plains between 4,000 and 6,000 m. Lastly, the hadal zone corresponds to the hadalpelagic zone, which is found in oceanic trenches. The pelagic zone comprises two subregions: the neritic zone and the oceanic zone. The neritic encompasses the water mass directly above the continental shelves whereas the oceanic zone includes all the completely open water. Whereas the littoral zone covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the intertidal zone because it is the area where tide level affects the conditions of the region. Exploration[edit] Main article: Ocean exploration False color photo

Map of large underwater features (1995, NOAA) Ocean travel by boat dates back to prehistoric times, but only in modern times has extensive underwater travel become possible. The deepest point in the ocean is the Mariana Trench, located in the Pacific Ocean near the Northern Mariana Islands. Its maximum depth has been estimated to be 10,971 metres (35,994 ft) (plus or minus 11 meters; see the Mariana Trench article for discussion of the various estimates of the maximum depth.) The British naval vessel, Challenger II surveyed the trench in 1951 and named the deepest part of the trench, the "Challenger Deep". In 1960, the Trieste successfully reached the bottom of the trench, manned by a crew of two men. Much of the ocean bottom remains unexplored and unmapped. A global image of many underwater features larger than 10 kilometres (6.2 mi) was created in 1995 based on gravitational distortions of the nearby sea surface

Water is a chemical compound with the chemical formula H 2O. A water molecule contains one oxygen and two hydrogen atoms that are connected by covalent bonds. Water is a liquid at standard ambient temperature and pressure, but it often co-exists on Earth with its solid state, ice, and gaseous state, steam (water vapor). Water covers 71% of the Earth's surface,[1] and is vital for all known forms of life.[2] On Earth, 96.5% of the planet's water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.[3][4] Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.[3] Water on Earth moves continually through the water cycle of evaporation and transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land. Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation.[5] There is a clear correlation between access to safe water and GDP per capita.[6] However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability.[7] A report, issued in November 2009, suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.[8] Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of the fresh water used by humans goes to agriculture.[9] Contents [hide] 1 Chemical and physical properties 2 Taste and odor 3 Distribution in nature 3.1 In the universe 3.2 Water and habitable zone 4 On Earth

4.1 Water cycle 4.2 Fresh water storage 4.3 Sea water 4.4 Tides 5 Effects on life 5.1 Aquatic life forms 6 Effects on human civilization 6.1 Health and pollution 6.2 Human uses 6.2.1 Agriculture 6.2.2 As a scientific standard 6.2.3 For drinking 6.2.4 Washing 6.2.5 Transportation 6.2.6 Chemical uses 6.2.7 Heat exchange 6.2.8 Fire extinction 6.2.9 Recreation 6.2.10 Water industry 6.2.11 Industrial applications 6.2.12 Food processing 7 Law, politics, and crisis 8 In culture 8.1 Religion 8.2 Philosophy

8.3 Literature 9 See also 9.1 Other topics 10 References 11 Further reading 12 External links Chemical and physical properties

Main articles: Properties of water, Water (data page), and Water model

Model of hydrogen bonds (1) between molecules of water

Impact from a water drop causes an upward "rebound" jet surrounded by circular capillary waves.

Snowflakes by Wilson Bentley, 1902

Dew drops adhering to a spider web

Capillary action of water compared to mercury Water is the chemical substance with chemical formula H

2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water appears in nature in all three common states of matter (solid, liquid, and gas) and may take many different forms on Earth: water vapor and clouds in the sky, seawater in the oceans, icebergs in the polar oceans, glaciers in the mountains, fresh and salt water lakes, rivers , and aquifers in the ground. The major chemical and physical properties of water are: Water is a liquid at standard temperature and pressure. It is tasteless and odorless. The intrinsic colour of water and ice is a very slight blue hue, although both appear colorless in small quantities. Water vapour is essentially invisible as a gas.[10] Water is transparent in the visible electromagnetic spectrum. Thus aquatic plants can live in water because sunlight can reach them. Infrared light is strongly absorbed by the hydrogen-oxygen or OH bonds. Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, it carries a slight negative charge, whereas the hydrogen atoms are slightly positive. As a result, water is a polar molecule with an electrical dipole moment. Water also can form an unusually large number of intermolecular hydrogen bonds (four) for a molecule of its size. These factors lead to strong attractive forces between molecules of water, giving rise to water's high surface tension[11] and capillary forces. The capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. This property is relied upon by all vascular plants, such as trees.[12] Water is a good polar solvent and is often referred to as the universal solvent. Substances that dissolve in water, e.g., salts, sugars, acids, alkalis, and some gases – especially oxygen, carbon dioxide (carbonation) are known as hydrophilic (water-loving) substances, while those that are immiscible with water (e.g., fats and oils), are known as hydrophobic (water-fearing) substances. All of the components in cells (proteins, DNA and polysaccharides) are dissolved in water, deriving their structure and activity from their interactions with the water. Pure water has a low electrical conductivity, but this increases with the dissolution of a small amount of ionic material such as sodium chloride. The boiling point of water (and all other liquids) is dependent on the barometric pressure. For example, on the top of Mt. Everest water boils at 68 °C (154 °F), compared to 100 °C (212 °F) at sea level at a similar latitude. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid. At 4181.3 J/(kg·K), water has a high specific heat capacity, as well as a high heat of vaporization (40.65 kJ·mol−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature.

The density of liquid water is 1,000 kg/m3 (62.43 lb/cu ft) at 4 °C. Ice has a density of 917 kg/m3 (57.25 lb/cu ft).

ADR label for transporting goods dangerously reactive with water The maximum density of water occurs at 3.98 °C (39.16 °F).[13] Most known pure substances become more dense as they cool, however water has the anomalous property of becoming less dense when it is cooled to its solid form, ice. During cooling water becomes more dense until reaching 3.98 °C. Below this temperature, the open structure of ice is gradually formed in the low temperature water; the random orientations of the water molecules in the liquid are maintained by the thermal motion, and below 3.98 °C there is not enough thermal energy to maintain this randomness. As water is cooled there are two competing effects: 1) decreasing volume, and 2) increase overall volume of the liquid as the molecules begin to orient into the organized structure of ice. Between 3.98 °C and 0 °C, the second effect will cancel the first effect so the net effect is an increase of volume with decreasing temperature.[14] Water expands to occupy a 9% greater volume as ice, which accounts for the fact that ice floats on liquid water, as in icebergs. Water is miscible with many liquids, such as ethanol, in all proportions, forming a single homogeneous liquid. On the other hand, water and most oils are immiscible, usually forming layers with the least dense liquid as the top layer, and the most dense layer at the bottom. Water forms an azeotrope with many other solvents. Water can be split by electrolysis into hydrogen and oxygen. As an oxide of hydrogen, water is formed when hydrogen or hydrogen-containing compounds burn or react with oxygen or oxygen-containing compounds. Water is not a fuel, it is an end-product of the combustion of hydrogen. The energy required to split water into hydrogen and oxygen by electrolysis or any other means is greater than the energy that can be collected when the hydrogen and oxygen recombine.[15] Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesium displace hydrogen from water, forming hydroxides. Being a flammable gas, the hydrogen given off is dangerous and the reaction of water with the more electropositive of these elements may be violently explosive. Property Remarks Importance to the Environment

Physical State Only substance occurring naturally in all three phases as solid, liquid, and gas on Earth's surface Transfer of heat between ocean and atmosphere by phase change

Dissolving Ability Dissolves more substances in greater quantities than any other common liquid Important in chemical, physical, and biological processes Density: mass per unit volume Density is determined by (1) temperature, (2) salinity, and (3) pressure, in that order of importance. The temperature of maximum density for pure water is 4°C. For seawater, the freezing point decreases with increasing salinity Controls oceanic vertical circulation, aids in heat distribution, and allows seasonal stratification Surface Tension Highest of all common liquids cell physiology Conduction of Heat cellular level Controls drop formation in rain and clouds; Important in

Highest of all common liquids

Important on the small scale, especially on

Heat Capacity Highest of all common solids and liquids Prevents extreme range in Earth's temperatures (i.e., great heat moderator) Latent Heat of Fusion Highest of all common liquids and most solids Thermostatic heat-regulating effect due to the release of heat on freezing and absorption on melting Latent Heat of Vaporization Highest of all common substances Immense importance: a major factor in the transfer of heat in and between ocean and atmosphere, driving weather and climate Refractive Index Increases with increasing salinity and decreases with increasing temperature Objects appear closer than in air Transparency Relatively great for visible light; absorptioin high for infrared and ultraviolet Important for photosynthesis Sound Transmission Good compared with other fluids Allows for sonar and precision depth recorders to rapidly determine water depth, and to detect subsurface features and animals; sounds can be heard great distances underwater Compressibility Only slight Boiling and Melting Points Taste and odor Density changes only slightly with pressure/depth Unusually high Allows water to exist as a liquid on most of Earth

Pure H2O is tasteless and odorless. Water can dissolve many different substances, giving it varying tastes and odors. Humans, and other animals, have developed senses that enable them to evaluate the potability of water by avoiding water that is too salty or putrid.

The taste of spring water and mineral water, often advertised in marketing of consumer products, derives from the minerals dissolved in it. The advertised purity of spring and mineral water refers to absence of toxins, pollutants, and microbes, not to the absence of naturally occurring minerals. Distribution in nature

In the universe Much of the universe's water is produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas.[16] On 22 July 2011 a report described the discovery of a gigantic cloud of water vapor containing "140 trillion times more water than all of Earth's oceans combined" around a quasar located 12 billion light years from Earth. According to the researchers, the "discovery shows that water has been prevalent in the universe for nearly its entire existence".[17][18] Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems such as ours. Water vapor is present in Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere[19] Atmosphere of Venus: 0.002% Earth's atmosphere: ~0.40% over full atmosphere, typically 1–4% at surface Atmosphere of Mars: 0.03% Atmosphere of Jupiter: 0.0004% Atmosphere of Saturn – in ices only Enceladus (moon of Saturn): 91% exoplanets (HD 189733 b[20] and HD 209458 b[21] are examples). Liquid water is present on Earth: 71% of surface. Enceladus: under the surface.

Europa: 100 km deep subsurface ocean. Mars Water ice is present on Earth – mainly as ice sheets. Mars Moon Titan Europa Enceladus Saturn's rings[22] Pluto and Charon[22] Comets and related (Kuiper belt and Oort cloud objects). Recent evidence points to the existence of water ice at the poles of Mercury.[23] Water ice may also be present on Ceres and Tethys. Water and other volatiles probably comprise much of the internal structures of Uranus and Neptune and the water in the deeper layers may be in the form of ionic water in which the molecules break down into a soup of hydrogen and oxygen ions, and deeper down as superionic water in which the oxygen crystallises but the hydrogen ions float around freely within the oxygen lattice.[24] Some of the Moon's minerals contain water molecules. For instance, in 2008 a laboratory device which ejects and identifies particles found small amounts of the compound in the inside of volcanic rock brought from Moon to Earth by the Apollo 15 crew in 1971.[25] NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.[26] Water and habitable zone Further information: Water distribution on Earth The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or farther from the Sun (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.[27][28]

Earth's gravity allows it to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would allow temperature extremes, thus preventing the accumulation of water except in polar ice caps (as on Mars). The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis. The state of water on a planet depends on ambient pressure, which is determined by the planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity, as it was observed on exoplanets Gliese 436 b[29] and GJ 1214 b.[30] There are various theories about origin of water on Earth. On Earth

Main articles: Hydrology and Water distribution on Earth

Water covers 71% of the Earth's surface; the oceans contain 96.5% of the Earth's water. The Antarctic ice sheet, which contains 61% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo. Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology. The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1,338,000,000 km3 (321,000,000 mi3).[3] Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers. Water is important in many geological processes. Groundwater is present in most rocks, and the pressure of this groundwater affects patterns of faulting. Water in the mantle is responsible for the melt

that produces volcanoes at subduction zones. On the surface of the Earth, water is important in both chemical and physical weathering processes. Water and, to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history. Water cycle Main article: Water cycle

Water cycle The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes: evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air. precipitation, from water vapor condensing from the air and falling to earth or ocean. runoff from the land usually reaching the sea. Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate as runoff into the sea, about 47 Tt per year. Over land, evaporation and transpiration contribute another 72 Tt per year. Precipitation, at a rate of 119 Tt per year over land, has several forms: most commonly rain, snow, and hail, with some contribution from fog and dew.[31] Dew is small drops of water that are condensed when a high density of water vapor meets a cool surface. Dew usually form in the morning when the temperature is the lowest, just before sunrise and when the temperature of the earth's surface starts to increase.[32] Condensed water in the air may also refract sunlight to produce rainbows. Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh water storage Bay of Fundy High Tide.jpgBay of Fundy Low Tide.jpg The Bay of Fundy at high tide (left) and low tide (right) Main article: Water resources Some runoff water is trapped for periods of time, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply. Sea water Main article: Seawater Sea water contains about 3.5% salt on average, plus smaller amounts of other substances. The physical properties of sea water differ from fresh water in some important respects. It freezes at a lower temperature (about −1.9 °C) and its density increases with decreasing temperature to the freezing point, instead of reaching maximum density at a temperature above freezing. The salinity of water in major seas varies from about 0.7% in the Baltic Sea to 4.0% in the Red Sea. Tides Main article: Tide Tides are the cyclic rising and falling of local sea levels caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

The seabed (also known as the seafloor, sea floor, or ocean floor) is the bottom of the ocean.

Ocean structure[edit]

See also: Seafloor spreading Drawing showing divisions according to depth and distance from shore

The major oceanic divisions Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources. The structure of the oceans, starting with the continents, begins usually with a continental shelf, continues to the continental slope – which is a steep descent into the ocean, until reaching the abyssal plain – a topographic plain, the beginning of the seabed, and its main area. The border between the continental slope and the abyssal plain usually has a more gradual descent, and is called the continental rise, which is caused by sediment cascading down the continental slope. The mid-ocean ridge, as its name implies, is a mountainous rise through the middle of all the oceans, between the continents. Typically a rift runs along the edge of this ridge. Along tectonic plate edges there are typically oceanic trenches – deep valleys, created by the mantle circulation movement from the mid-ocean mountain ridge to the oceanic trench. Hotspot volcanic island ridges are created by volcanic activity, erupting periodically, as the tectonic plates pass over a hotspot. In areas with volcanic activity and in the oceanic trenches, there are hydrothermal vents – releasing high pressure and extremely hot water and chemicals into the typically freezing water around it. Deep ocean water is divided into layers or zones, each with typical features of salinity, pressure, temperature and marine life, according to their depth. Lying along the top of the abyssal plain is the abyssal zone, whose lower boundary lies at about 6,000 m (20,000 ft). The hadal zone – which includes the oceanic trenches, lies between 6,000–11,000 metres (20,000–36,000 ft) and is the deepest oceanic zone. Benthos[edit]

Main article: Benthos Benthos is the community of organisms which live on, in, or near the seabed, the area known as the benthic zone.[1] This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. The benthic zone is the ecological region on, in and immediately above the seabed, including the sediment surface and some sub-surface layers. Benthos generally live in close relationship with the substrate bottom, and many such organisms are permanently attached to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer, is an integral part of the benthic zone, and greatly

influences the biological activity which takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud. Seabed features[edit]

Oceanic ridge with deep sea vent

Layers of the pelagic zone Each area of the seabed has typical features such as common soil composition, typical topography, salinity of water layers above it, marine life, magnetic direction of rocks, and sedimenting. Seabed topography is flat where sedimenting is heavy and covers the tectonic features. Sedimenting comes from various sources: Land erosion sediments, brought mainly by rivers, New "young rock" – New magma of basalt composition, from the mid-ocean ridge. Underwater volcanic ash spreading, especially from hydrothermal vents. Microorganism activity. Sea currents eroding the seabed itself, Marine life: corals, fish, algae, crabs, marine plants and other biological created sediment. Where sedimenting is avoided, such as in the Atlantic ocean especially in the northern and eastern Atlantic, the original tectonic activity can be clearly seen as straight line "cracks" or "vents" thousands of kilometers long. Recently there has been the discovery of abundant marine life in the deep sea, especially around hydrothermal vents. Large deep sea communities of marine life have been discovered around black and white smokers – hydrothermal vents emitting typical chemicals toxic to humans and most of the vertebrates. This marine life receives its energy from both the extreme temperature difference (typically a drop of 150 degrees) and from chemosynthesis by bacteria. Brine pools are another seabed feature, usually connected to cold seeps.

Patterns of Ocean Circulation By Alecia M. Spooner from Environmental Science For Dummies Environmental scientists study ocean circulation because, along with patterns of air movement in the atmosphere, the movement of water through the oceans helps determine weather and climate conditions for different regions of the world. The three main patterns of ocean circulation are gyres, upwelling, and thermohaline circulation.

Patterns of ocean circulation: Gyres As the prevailing winds in earth’s atmosphere blow across the surface of the oceans, the winds push water in the direction that they’re blowing. As a result, the surface water of the oceans moves in concert with the air above it.

This dual movement creates large circular patterns, or gyres, in each of the planet’s oceans. The ocean gyres move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Ocean gyre circulation moves cold surface water from the poles to the equator, where the water is warmed before the gyres send it back toward the poles. The water’s temperature influences the temperature of the air: Cold currents bring cooler air to the coastline as they move toward the equator, and they bring warmer air to the continents they pass on their way back toward the poles.

Patterns of ocean circulation: Upwelling Sometimes the movement of surface currents along a coastline leads to a circulation process called upwelling. As a result of the Coriolis effect, upwelling commonly occurs on the west coast of continents, where the surface waters moving toward the equator are replaced by deeper cold water that moves up to the surface.

The deep water brings with it nutrients from the bottom of the ocean. These nutrients support the growth of primary producers, which support the entire food web in the ocean.

Regions of the world where deep ocean upwelling occurs are often very productive with high numbers of many different types of organisms living in them.

Patterns of ocean circulation: Thermohaline circulation The largest circulation of water on the planet is a direct result of changes in temperature and salinity. Salinity is the measure of dissolved salt in water. The pattern of ocean currents related to salinity and temperature is called the thermohaline circulation (thermo = heat; haline = salt). This figure gives you a general idea of what this pattern looks like.

[Credit: Illustration by Wiley, Composition Services Graphics] Credit: Illustration by Wiley, Composition Services Graphics Sometimes called the thermohaline conveyor belt, this circulation pattern moves cold water around the globe in deep water currents and warmer water in surface currents. A single molecule of water being transported by thermohaline circulation may take a thousand years to move completely throughout the Earth’s oceans.

The conveyor is driven by changes in the density of water as a result of changes in both temperature and salinity. Here’s how this circulation pattern works:

Warm water in a shallow current near the surface moves toward the North Pole near Iceland. As this water reaches the colder polar region, some of it freezes or evaporates, leaving behind the salt that was dissolved in it. The resulting water is colder and has more salt per volume than it did before (and thus is more dense).

The cold, dense, salty water sinks deeper into the ocean and moves to the south, as far as Antarctica. After it makes its way near Antarctica, the cold, deep current splits, one branch moving up toward India into the Indian Ocean and the other continuing along Antarctica into the Pacific Ocean.

Each branch of the cold, deep current is eventually warmed in the Indian Ocean or the northern part of the Pacific Ocean. Although the water still contains the same amount of salt, it’s a little less dense because it’s warmer than the cold water surrounding it; as a result, it moves upward, becoming a surface current.

The warm, shallow, less dense surface current moves to the west, across the Pacific Ocean, and into the Indian Ocean, where it rejoins the Indian Ocean branch. Both branches then continue into the Atlantic Ocean and head back toward the North Pole.

Water cycle From Wikipedia, the free encyclopedia

The water cycle File:Earth's Water Cycle.ogv

Earth's water cycle The water cycle, also known as the hydrologic cycle or the H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor). The water cycle involves the exchange of energy, which leads to temperature changes. For instance, when water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence climate. The evaporative phase of the cycle purifies water which then replenishes the land with freshwater. The flow of liquid water and ice transports minerals across the globe. It is also involved in reshaping the geological features of the Earth, through processes including erosion and sedimentation. The water cycle is also essential for the maintenance of most life and ecosystems on the planet. Contents [hide]

1 Description 1.1 Processes 2 Residence times 3 Changes over time 4 Effects on climate 5 Effects on biogeochemical cycling 6 Slow loss over geologic time 7 History of hydrologic cycle theory 7.1 Floating land mass 7.2 Precipitation and percolation 7.3 Precipitation alone 8 See also 9 References 10 Further reading 11 External links File:The Water Cycle.ogv As the Earth's surface water evaporates, winds move water in the air from the sea to the land, increasing the amount of fresh water on land. File:The Water Cycle Watering the Land.ogv Water vapor is converted to clouds that bring fresh water to land in the form of rain or snow. File:The Water Cycle - Following the Water.ogv Precipitation falls on the ground, but what happens to that water depends greatly on the geography of the land at any particular place.

Description[edit]

The Sun, which drives the water cycle, heats water in oceans and seas. Water evaporates as water vapour into the air. Ice and snow can sublimate directly into water vapour. Evapotranspiration is water transpired from plants and evaporated from the soil. Rising air currents take the vapour up into the atmosphere where cooler temperatures cause it to condense into clouds. Air currents move water vapour around the globe, cloud particles collide, grow, and fall out of the upper atmospheric layers as precipitation. Some precipitation falls as snow or hail, sleet, and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff and water emerging from the ground (groundwater) may be stored as freshwater in lakes. Not all runoff flows into rivers, much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers, which can store freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge. Some groundwater finds openings in the land surface and comes out as freshwater springs. In river valleys and flood-plains there is often continuous water exchange between surface water and ground water in the hyporheic zone . Over time, the water returns to the ocean, to continue the water cycle. Processes[edit]

Many different processes lead to movements and phase changes in water Precipitation Condensed water vapor that falls to the Earth's surface . Most precipitation occurs as rain, but also includes snow, hail, fog drip, graupel, and sleet.[1] Approximately 505,000 km3 (121,000 cu mi) of water falls as precipitation each year, 398,000 km3 (95,000 cu mi) of it over the oceans.[2] The rain on land contains 107,000 km3 (26,000 cu mi) of water per year and a snowing only 1,000 km3 (240 cu mi).[3] Canopy interception The precipitation that is intercepted by plant foliage, eventually evaporates back to the atmosphere rather than falling to the ground. Snowmelt The runoff produced by melting snow. Runoff The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

Infiltration The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.[4] Subsurface flow The flow of water underground, in the vadose zone and aquifers. Subsurface water may return to the surface (e.g. as a spring or by being pumped) or eventually seep into the oceans. Water returns to the land surface at lower elevation than where it infiltrated, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years. Evaporation The transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere.[5] The source of energy for evaporation is primarily solar radiation. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration. Total annual evapotranspiration amounts to approximately 505,000 km3 (121,000 cu mi) of water, 434,000 km3 (104,000 cu mi) of which evaporates from the oceans.[2] Sublimation The state change directly from solid water (snow or ice) to water vapor.[6] Deposition This refers to changing of water vapor directly to ice. Advection The movement of water — in solid, liquid, or vapor states — through the atmosphere. Without advection, water that evaporated over the oceans could not precipitate over land.[7] Condensation The transformation of water vapor to liquid water droplets in the air, creating clouds and fog.[8] Transpiration The release of water vapor from plants and soil into the air. Water vapor is a gas that cannot be seen. Percolation Water flows horizontally through the soil and rocks under the influence of gravity Plate tectonics

Water enters the mantle via subduction of oceanic crust. Water returns to the surface in via volcanism.

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