Thursday, December 6, 2012

Anti El Nino,, La Niña ( /lɑːˈniːnjə/, Spanish pronunciation: [la ˈniɲa]) is a coupled ocean-atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño–Southern Oscillation climate pattern. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5 °C. Sony VAIO PCG-3B1M Battery In the United States, an episode of La Niña is defined as a period of at least 5 months of La Niña conditions.The name La Niña originates from Spanish, meaning "the girl," analogous to El Niño meaning "the boy." La Niña, sometimes informally called "anti-El Niño", is the opposite of El Niño, Sony VAIO PCG-3C1T Battery where the latter corresponds instead to a higher sea surface temperature by a deviation of at least 0.5 °C, and its effects are often the reverse of those of El Niño. El Niño is known for its potentially catastrophic impact on the weather along the Chilean, Peruvian, New Zealand, and Australian coasts, among others. Sony VAIO PCG-3D1M Battery It has extensive effects on the weather in North America, even affecting the Atlantic Hurricane Season. La Niña is often, though not always, preceded by an El Niño.The results of La Niña are mostly the opposite of those of El Niño; for example, El Niño would cause a dry period in the Midwestern U.S., while La Niña would typically cause a wet period in that area. Sony VAIO PCG-3G2M Battery La Niña often causes drought conditions in the western Pacific; flooding in northern South America; mild wet summers in northern North America, and drought in the southeastern United States. For India, an El Niño is often a cause for concern because of its adverse impact on the south-west monsoon; this happened in 2009. Sony VAIO PCG-5R1M Battery A La Niña, on the other hand, is often beneficial for the monsoon, especially in the latter half. The La Niña that appeared in the Pacific in 2010 probably helped 2010's south-west monsoon end on a favourable note. However, it also contributed to the deluge in Australia, Sony VAIO PCG-7141M Battery which resulted in one of that country's worst natural disasters with large parts ofQueensland either under water from floods of unusual proportions or being battered by tropical cyclones, including that of category 5 Tropical Cyclone Yasi. It wreaked similar havoc in south-eastern Brazil and flooding that have affected Sri Lanka. Sony VAIO PCG-7143M Battery There was a strong La Niña episode during 1988–1989. La Niña also formed in 1995, and in 1999–2000, followed by neutral periods between 2000 and 2002. The La Niña which developed in mid 2007 and lasted until almost 2009, was a moderate one. Sony VAIO PCG-7151M Battery NOAA confirmed that a moderate La Niña developed in their November El Niño/Southern Oscillation Diagnostic Discussion, and that it would likely continue into 2008. According to NOAA, "Expected La Niña impacts during November – January include a continuation of above-average precipitation over Indonesia and below-average precipitation over the central equatorial Pacific. Sony VAIO PCG-7154M Battery For the contiguous United States, potential impacts include above average precipitation in the Northern Rockies, Northern California, and in southern and eastern regions of the Pacific Northwest. Below-average precipitation is expected across the southern tier, particularly in the southwestern and southeastern states.[1] Sony VAIO PCG-7162M Battery However, an El Niño returned in May–June 2009 and lasted until April 2010. The effects of El Niño in 2009 were already being seen in the fall of 2009 as the remnants of Tropical Storm Ida strengthened into a powerful coastal storm.[2][3] A new La Niña episode developed quite quickly in the eastern and central tropical Pacific in mid-2010,[4] and lasted until early 2011.[1] Sony VAIO PCG-7181M Battery It intensified again in the mid-2011 and is predicted to last at least until early 2012[5] This La Niña, combined with record-high ocean temperatures in the north-eastern Indian Ocean, has been a large factor in the 2010–2011 Queensland floods,[6] and the quartet of recent heavy snowstorms in North America starting with the December 2010 North American blizzard. Sony VAIO PCG-41112M Battery The same La Niña event is also a likely cause of a series of tornadoes of above-average severity that struck the Midwestern and Southern United States in the spring of 2011, and is currently a major factor in the drought conditions persisting in the South Central states including Texas, Oklahoma and Arkansas. [7] Sony VAIO PCG-7153M Battery In 2011, on a global scale, La Niña events helped keep the average global temperature below recent trends. As a result, 2011 tied with 1997 for the 11th warmest year on record. It was the second coolest year of the 21st century to date, and tied with the second warmest year of the 20th century. Sony VAIO PCG-71312M Battery A relatively strong phase of La Niña opened the year, dissipated in the spring before re-emerging in October and lasted through the end of the year. When compared to previous La Niña years, the 2011 global surface temperature was the warmest observed. The 2011 globally-averaged precipitation over land was the second wettest year on record, behind 2010. Sony VAIO PCG-7144M Battery Precipitation varied greatly across the globe. La Niña contributed to severe drought in East Africa and to Australia's third wettest year in its 112-year period of record.El Niño–Southern Oscillation ( /ɛlˈniːnjoʊ/, Spanish pronunciation: [el ˈniɲo], ENSO), or El Niño/La Niña–Southern Oscillation, is a quasiperiodic climate pattern, not a storm, that occurs across the tropical Pacific Ocean roughly every five years. Sony VAIO PCG-7191L Battery The Southern Oscillation refers to variations in the temperature of the surface of the tropical eastern Pacific Ocean (warming and cooling known as El Niño and La Niña respectively) and in air surface pressure in the tropical western Pacific. The two variations are coupled: the warm oceanic phase, Sony VAIO PCG-3C1M Battery El Niño, accompanies high air surface pressure in the western Pacific, while the cold phase, La Niña, accompanies low air surface pressure in the western Pacific.[2][3] Mechanisms that cause the oscillation remain under study.The extremes of this climate pattern's oscillations, El Niño and La Niña, cause extreme weather (such as floods and droughts) in many regions of the world. Sony VAIO PCG-3F1M Battery Developing countries dependent upon agriculture and fishing, particularly those bordering the Pacific Ocean, are the most affected. In popular usage, the El Niño–Southern Oscillation is often called just "El Niño". El Niño is Spanish for "the little boy" and refers to the Christ child, because periodic warming in the Pacific near South Americais usually noticed around Christmas. Sony VAIO PCG-3H1M Battery El Niño is defined by prolonged differences in the Pacific ocean Sea surface temperatures when compared with the average value. The accepted definition is a warming or cooling of at least 0.5 °C (0.9 °F) averaged over the east-central tropical Pacific Ocean. Typically, this anomaly happens at irregular intervals of 3–7 years and lasts nine months to two years. Sony VAIO PCG-3J1M Battery The average period length is 5 years. When this warming or cooling occurs for only seven to nine months, it is classified as El Niño/La Niña "conditions"; when it occurs for more than that period, it is classified as El Niño/La Niña "episodes".El Niño's warm rush of nutrient-poor water heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of theHumboldt Current. Sony VAIO PCG-8141M Battery When El Niño conditions last for many months, extensive ocean warming and the reduction in Easterly Trade winds limits upwelling of cold nutrient-rich deep water and its economic impact to local fishing for an international market can be serious. Although its causes are still being investigated, El Niño events begin when trade winds, part of the Walker circulation, falter for many months. Sony VAIO PCG-8161M Battery A series of Kelvin waves—relatively warm subsurface waves of water a few centimetres high and hundreds of kilometres wide—cross the Pacific along the equator and create a pool of warm water near South America, where ocean temperatures are normally cold due to upwelling. Sony VAIO PCG-3C2M Battery The weakening of the winds can also create twin cyclones, another sign of a future El Niño.The Pacific Ocean is a heat reservoir that drives global wind patterns, and the resulting change in its temperature alters weather on a global scale.[9] Rainfall shifts from the western Pacific toward the Americas, while Indonesia and India become drier. Sony VAIO PCG-5N2M Battery Jacob Bjerknes in 1969 contributed to an understanding of ENSO by suggesting that an anomalously warm spot in the eastern Pacific can weaken the east-west temperature difference, disrupting trade winds that push warm water to the west. The result is increasingly warm water toward the east. Sony VAIO PCG-5P1M Battery Several mechanisms have been proposed through which warmth builds up in equatorial Pacific surface waters, and is then dispersed to lower depths by an El Niño event.[12] The resulting cooler area then has to "recharge" warmth for several years before another event can take place. Sony VAIO PCG-5S1M Battery While not a direct cause of El Niño, the Madden-Julian Oscillation, or MJO, propagates rainfall anomalies eastward around the global tropics in a cycle of 30–60 days, and may influence the speed of development and intensity of El Niño and La Niña in several ways. Sony VAIO PCG-9Z1M Battery For example, westerly flows between MJO-induced areas of low pressure may cause cyclonic circulations north and south of the equator. When the circulations intensify, the westerly winds within the equatorial Pacific can further increase and shift eastward, playing a role in El Niño development.[15] Sony VAIO PCG-7171M Battery Madden-Julian activity can also produce eastward-propagating oceanicKelvin waves, which may in turn be influenced by a developing El Niño, leading to a positive feedback loop. The Southern Oscillation is the atmospheric component of El Niño. Sony VAIO PCG-7186M Battery This component is an oscillation in surface air pressure between the tropical eastern and the western Pacific Ocean waters. The strength of the Southern Oscillation is measured by the Southern Oscillation Index (SOI). The SOI is computed from fluctuations in the surface air pressure difference between Tahiti and Darwin, Australia.[17] Sony VAIO PCG-81112M Battery El Niño episodes are associated with negative values of the SOI, meaning that the pressure difference between Tahiti and Darwin is relatively small. Low atmospheric pressure tends to occur over warm water and high pressure occurs over cold water, in part because of deep convection over the warm water. Sony VAIO PCG-31311M Battery El Niño episodes are defined as sustained warming of the central and eastern tropical Pacific Ocean. This results in a decrease in the strength of the Pacific trade winds, and a reduction in rainfall over eastern and northern Australia. During non-El Niño conditions, the Walker circulation is seen at the surface as easterly trade winds that move water and air warmed by the sun toward the west. Sony VAIO PCG-8152M Battery This also creates ocean upwelling off the coasts of Peru and Ecuador and brings nutrient-rich cold water to the surface, increasing fishing stocks. The western side of the equatorial Pacific is characterized by warm, wet low pressure weather as the collected moisture is dumped in the form of typhoons andthunderstorms. Sony VAIO PCG-31111M Battery The ocean is some 60 centimetres (24 in) higher in the western Pacific as the result of this motion.Because El Niño's warm pool feeds thunderstorms above, it creates increased rainfall across the east-central and eastern Pacific Ocean including several portions of the South American west coast. Sony VAIO PCG-61111M Battery The effects of El Niño in South America are direct and stronger than in North America. An El Niño is associated with warm and very wet weather months in April–October along the coasts of northern Peru and Ecuador, causing major flooding whenever the event is strong or extreme. Sony VAIO PCG-51112M Battery The effects during the months of February, March and April may become critical. Along the west coast ofSouth America, El Niño reduces the upwelling of cold, nutrient-rich water that sustains large fish populations, which in turn sustain abundant sea birds, whose droppings support the fertilizer industry. This leads to fish kills offshore Peru. Sony VAIO PCG-51211M Battery The local fishing industry along the affected coastline can suffer during long-lasting El Niño events. The world's largest fishery collapsed due to overfishing during the 1972 El Niño Peruvian anchoveta reduction. During the 1982–83 event, jack mackerel and anchoveta populations were reduced, Sony VAIO PCG-51212M Battery scallops increased in warmer water, but hake followed cooler water down the continental slope, while shrimp and sardines moved southward, so some catches decreased while others increased. Horse mackerel have increased in the region during warm events. Shifting locations and types of fish due to changing conditions provide challenges for fishing industries. Sony VAIO PCG-41111M Battery Peruvian sardines have moved during El Niño events to Chilean areas. Other conditions provide further complications, such as the government of Chile in 1991 creating restrictions on the fishing areas for self-employed fishermen and industrial fleets.The ENSO variability may contribute to the great success of small fast-growing species along the Peruvian coast, as periods of low population removes predators in the area. Sony VAIO PCG-41111V Battery Similar effects benefit migratory birds that travel each spring from predator-rich tropical areas to distant winter-stressed nesting areas. Southern Brazil and northern Argentina also experience wetter than normal conditions but mainly during the spring and early summer. Sony VAIO PCG-61412V Battery Central Chile receives a mild winter with large rainfall, and the Peruvian-Bolivian Altiplano is sometimes exposed to unusual winter snowfall events. Drier and hotter weather occurs in parts of the Amazon River Basin, Colombia, and Central America. Winters, during the El Niño effect, are warmer and drier than average in the Northwest, Sony VAIO PCG-71112M Battery Northmidwest, and Northmideast United States, and therefore those regions experience reduced snowfalls. Meanwhile, significantly wetter winters are present in northwest Mexico and the southwest United States including central and southern California, Sony VAIO PCG-81111V Battery while both cooler and wetter than average winters in northeast Mexico and the southeast United States (including the Tidewater region of Virginia) occur during the El Niño phase of the oscillation.Some believed that the ice-storm in January 1998, which devastated parts of Southern Ontario and Southern Quebec, was caused or accentuated by El Niño's warming effects. Sony VAIO PCG-81111V Battery El Niño warmed Vancouver for the 2010 Winter Olympics, such that the area experienced a subtropical-like winter during the games.[27] El Niño is credited with suppressing hurricanes and made the 2009 hurricane season the least active in twelve years. Sony VAIO PCG-81212M Battery Most tropical cyclones form on the side of the subtropical ridge closer to the equator, then move poleward past the ridge axis before recurving into the main belt of the Westerlies.[29] When the subtropical ridge position shifts due to El Niño, so will the preferred tropical cyclone tracks. Sony VAIO PCG-81212V Battery Areas west of Japan and Korea tend to experience much fewer September–November tropical cyclone impacts during El Niño and neutral years. During El Niño years, the break in the subtropical ridge tends to lie near 130°E, which would favor the Japanese archipelago.[30] Sony VAIO PCG-51111M Battery During El Niño years, Guam's chance of a tropical cyclone impact is one-third of the long term average.[31] The tropical Atlantic ocean experiences depressed activity due to increased vertical wind shear across the region during El Niño years.[32] On the flip side however, the tropical Pacific Ocean east of the dateline has above normal activity during El Niño years due to well above average water temperatures and decreased windshear. Sony VAIO VPCS13X9E/B battery Most of the recorded East Pacific Category 5 hurricanes occur during El Niño years in clusters. In Africa, East Africa - including Kenya, Tanzania, and the White Nile basin - experiences, in the long rains from March to May, wetter-than-normal conditions. There are also drier than normal conditions from December to February in south-central Africa, Sony VAIO VPCS12V9E/B battery mainly in Zambia, Zimbabwe, Mozambique, and Botswana. Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia, increasing bush fires, worsening haze, and decreasing air quality dramatically. Sony VAIO VPCS12V9E/B battery Drier-than-normal conditions are also in general observed in Queensland, inland Victoria, inland New South Wales, and eastern Tasmaniafrom June to August.Many ENSO linkages exist in the high southern latitudes around Antarctica.[34] Specifically, El Niño conditions result in high pressure anomalies over theAmundsen and Bellingshausen seas, Sony VAIO VPCF13M8E/B battery causing reduced sea ice and increased poleward heat fluxes in these sectors as well as the Ross Sea. The Weddell Sea, conversely, tends to become colder with more sea ice during El Niño. The exact opposite heating and atmospheric pressure anomalies occur during La Niña.[35] This pattern of variability is known as the Antarctic Dipole mode, although the Antarctic response to ENSO forcing is not ubiquitous.[35] Sony VAIO VPCF13Z0E/B battery El Niño's effects on Europe are not entirely clear, but it is not nearly as affected as at least large parts of other continents. There is some evidence that an El Niño may cause a wetter, cloudier winter in Northern Europe and a milder, drier winter in the Mediterranean Sea region. Sony VAIO VPCM13M1E/L battery The El Niño winter of 2006/2007 was unusually mild in Europe, and the Alps recorded very little snow coverage that season.[36] In most recent times, Singapore experienced the driest February in 2010 since records begins in 1869. Sony VAIO VPCM13M1E/W battery With only 6.3 millimetres of rain fell in the month and temperatures hitting as high as 35 degrees Celsius on 26 February. The years 1968 and 2005 had the next driest Februaries, when 8.4 mm of rain fell. La Niña is the name for the cold phase of ENSO, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen. Sony VAIO VPCF22M1E battery The name La Niña originates from Spanish, meaning "the girl", analogous to El Niño meaning "the boy". It has also in the past been called anti-El Niño, and El Viejo (meaning "the old man").La Niña results in wetter-than-normal conditions in Southern Africa from December to February, and drier-than-normal conditions over equatorial East Africa over the same period.Sony VAIO VPCF11M1E/H battery During La Niña years, the formation of tropical cyclones, along with the subtropical ridge position, shifts westward across the western Pacific ocean, which increases the landfall threat to China.[30] In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by an amount of 2 °C. Sony VAIO VPCF13M0E/B battery It also caused heavy rains over Malaysia, Philippines, andIndonesia. During a time of La Niña, drought plagues the coastal regions of Peru and Chile.[41] From December to February, northern Brazil is wetter than normal. La Niña causes mostly the opposite effects of El Niño. Sony VAIO VPCYB2M1E battery La Niña causes above-average precipitation across the North Midwest, the Northern Rockies, Northern California, and the Pacific Northwest's southern and eastern regions. Meanwhile there is below-average precipitation in the southwestern and southeastern states.[42] Sony VAIO VPCYB3V1E battery La Niñas occurred in 1904, 1908, 1910, 1916, 1924, 1928, 1938, 1950, 1955, 1964, 1970, 1973, 1975, 1988, 1995, 1998, 2010 and 2011.[43] In Canada, La Niña will in general cause a cooler, snowier winter, such as the near-record-breaking amounts of snow recorded in the La Niña winter of 2007/2008 in Eastern Canada. Sony VAIO VPCY11M1E battery The 2010-2011 La Niña was one of the strongest ever observed. The effect on Eastern Australia was devastating. Transitional phases at the onset or departure of El Niño or La Niña can also be important factors on global weather by affecting teleconnections. Sony VAIO VPCS12L9E/B battery Significant episodes are known as Trans-Niño and measured by the Trans-Niño index (TNI)[47]. Examples of affected short-time climate in North America include precipitation in the Northwestern US[48]and intense tornado activity in the contiguous US. There was a strong La Niña episode during 1988–1989. Sony VAIO VPCF11S1E/B battery La Niña also formed in 1995 and from 1998–2000, and a minor one from 2000–2001. In recent times, an occurrence of El Niño started in September 2006[50] and lasted until early 2007.[51] From June 2007 on, data indicated a moderate La Niña event, which strengthened in early 2008 and weakened before the start of 2009; Sony VAIO VPCYB3V1E/R Battery the 2007–2008 La Niña event was the strongest since the 1988–1989 event. The strength of the La Niña made the 2008 Atlantic hurricane season one of the most active since 1944; there were 16 named storms of at least 39 mph (63 km/h), eight of which became 74 mph (119 km/h) or greater hurricanes.[28] Sony VAIO VPCF23P1E Battery According to NOAA, El Niño conditions were in place in the equatorial Pacific Ocean starting June 2009, peaking in January–February. Positive SST anomalies (El Niño) lasted until May 2010. SST anomalies then transitioned into the negative (La Niña) and have now transitioned back to ENSO-neutral during April 2012. Sony VAIO VPCF23N1E Battery In early July, NOAA stated that El Niño conditions have a 50+% chance of developing during the Northern Hemisphere Summer. As the 2012 Northern Hemisphere Summer started to draw to a close, NOAA stated that El Niño conditions are likely to develop in August or September. Sony VAIO VPCY21S1E/L Battery A study of climate records has shown that El Niño events in the equatorial Pacific are generally associated with a warm tropical North Atlantic in the following spring and summer.[52] About half of El Niño events persist sufficiently into the spring months for the Western Hemisphere Warm Pool (WHWP) to become unusually large in summer. Sony VAIO VPCY21S1E/G battery Occasionally, El Niño's effect on the Atlantic Walker circulation over South America strengthens the easterly trade winds in the western equatorial Atlantic region. As a result, an unusual cooling may occur in the eastern equatorial Atlantic in spring and summer following El Niño peaks in winter.[54] Sony VAIO VPCF24M1E battery Cases of El Niño-type events in both oceans simultaneously have been linked to severe famines related to the extended failure of monsoon rains. During the last several decades the number of El Niño events increased, and the number of La Niña events decreased,[56] Sony VAIO VPCS111FM/S Battery although we may need to observe ENSO for much longer to detect robust changes [57] The question is whether this is a random fluctuation or a normal instance of variation for that phenomenon or the result of global climate changes toward global warming. The studies of historical data show that the recent El Niño variation is most likely linked to global warming. Sony VAIO VPCS115EC Battery

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