La Niña ( // , Spanish pronunciation: [la ˈniɲa] ) is a coupled ocean-atmosphere phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation climate pattern. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño, and El Viejo (meaning "the old man"). During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3 to 5 °C (5.4 to 9 °F). An appearance of La Niña persists for at least five months. It has extensive effects on the weather across the globe, particularly in North America, even affecting the Atlantic and Pacific hurricane seasons, in which more tropical cyclones in the Atlantic basin due to low wind shear and warmer sea surface temperatures, while reducing tropical cyclogenesis in the Pacific Ocean during a La Niña.
La Niña is the positive and cold phase of the El Niño–Southern Oscillation, and is associated with cooler-than-average sea surface temperatures in the central and eastern tropical Pacific Ocean. 0.5 °C (0.90 °F) cooler for six consecutive months or longer.However, each country and island nation has a different threshold for what constitutes a La Niña event, which is tailored to their specific interests. For example, the Australian Bureau of Meteorology looks at the trade winds, SOI, weather models and sea surface temperatures in the Niño 3 and 3.4 regions before declaring that a La Niña event has started. However, the Japan Meteorological Agency declares that a La Niña event has started when the average five-month sea surface temperature deviation for the NINO.3 region is more than
A timeline of all La Niña episodes between 1900 and 2019.
There was a relatively strong La Niña episode during 1988–1989. La Niña also formed in late 1983, 39 miles per hour (63 km/h), eight of which became 74-mile-per-hour (119 km/h) or greater hurricanes.in 1995, and a protracted La Niña event that lasted from mid-1998 through early 2001. This was followed by a neutral period between 2001 and 2002. The La Niña which developed in mid-2007, and lasted until almost 2009, was a moderate one. The strength of La Niña made the 2008 Atlantic hurricane season one of the five most active since 1944; sixteen named storms had winds of at least
A new La Niña episode developed quite quickly in the eastern and central tropical Pacific in mid-2010,and lasted until early 2011. It intensified again in mid-2011 and lasted until early 2012. This La Niña, combined with record-high ocean temperatures in the north-eastern Indian Ocean, was a large factor in the 2010–11 Queensland floods, and the quartet of recent heavy snowstorms in North America starting with the December 2010 North American blizzard. The same La Niña event was 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 drought conditions in the South Central states including Texas, Oklahoma and Arkansas. Meanwhile, a series of major storms caused extensive flooding in California in December 2010, with seven consecutive days of non-stop rainfall, leading to one of the wettest Decembers in over 120 years of records. This is in contrast to the drier-than-normal conditions typically associated with La Niña in California, especially in the south.
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 eleventh-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. 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. Precipitation varied greatly across the globe. This La Niña contributed to severe drought in East Africa and to Australia's third-wettest year in its 112-year period of records.
La Niñas occurred in 1904, 1908, 1910, 1916, 1924, 1928, 1938, 1949–51,1954–56, 1964, 1970–72, 1973–76, 1983–85, 1988–89, 1995–96, 1998–2001, 2005–06, 2007–08, 2008–09, 2010–12, 2016, and 2017–18.
La Niña impacts the global climate and disrupts normal weather patterns, which as a result can lead to intense storms in some places and droughts in others.
Observations of La Niña events since 1950, show that impacts associated with La Niña events depend on what season it is.However, while certain events and impacts are expected to occur during events, it is not certain or guaranteed that they will occur.
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.
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 in China. 2 °C (36 °F). It also caused heavy rains over Malaysia, the Philippines, and Indonesia.In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by
La Niña causes mostly the opposite effects of El Niño, above-average precipitation across the northern Midwest, the northern Rockies, Northern California, and the Pacific Northwest's southern and eastern regions. Meanwhile, precipitation in the southwestern and southeastern states, as well as Southern California, is below average.This also allows for the development of many stronger-than-average hurricanes in the Atlantic and fewer in the Pacific.
The synoptic condition for Tehuantepecer winds is associated with high-pressure system forming in Sierra Madre of Mexico in the wake of an advancing cold front, which causes winds to accelerate through the Isthmus of Tehuantepec. Tehuantepecers primarily occur during the cold season months for the region in the wake of cold fronts, between October and February, with a summer maximum in July caused by the westward extension of the Azores-Bermuda high pressure system. Wind magnitude is weaker during La Niña years than El Niño years, due to the less frequent cold frontal incursions during La Niña winters,with its effects can last from a few hours to six days. Between 1942 and 1957, La Niña had an impact that caused isotope changes in the plants of Baja California.
In Canada, La Niña will, in general, cause a cooler, snowier winter, such as the near-record-breaking amounts of snow recorded in La Niña winter of 2007/2008 in Eastern Canada.
During a time of La Niña, drought plagues the coastal regions of Peru and Chile.From December to February, northern Brazil is wetter than normal. La Niña causes higher than normal rainfall in the central Andes, which in turn causes catastrophic flooding on the Llanos de Mojos of Beni Department, Bolivia. Such flooding is documented from 1853, 1865, 1872, 1873, 1886, 1895, 1896, 1907, 1921, 1928, 1929 and 1931.
The traditional La Niña, also called Eastern Pacific (EP) La Niña,involves temperature anomalies in the Eastern Pacific. However, in the last two decades, nontraditional La Niña were observed, in which the usual place of the temperature anomaly (Niño 1 and 2) is not affected, but an anomaly arises in the central Pacific (Niño 3.4). The phenomenon is called Central Pacific (CP) La Niña, "dateline" La Niña (because the anomaly arises near the dateline), or La Niña "Modoki" (Modoki is Japanese for "similar, but different"). There are flavors of ENSO additional to EP and CP types and some scientists argue that ENSO exists as a continuum often with hybrid types.
The effects of the CP La Niña are different from those of the traditional EP La Niña—e.g., the recently discovered La Niña leads to a rainfall increase over northwestern Australia and northern Murray-Darling basin, rather than over the east as in a conventional La Niña.Also, La Niña Modoki increases the frequency of cyclonic storms over Bay of Bengal, but decreases the occurrence of severe storms in the Indian Ocean overall, with the Arabian Sea becoming severely non-conductive to tropical cyclone formation.
The recent discovery of ENSO Modoki has some scientists believing it to be linked to global warming.However, comprehensive satellite data go back only to 1979. Generally, there is no scientific consensus on how/if climate change may affect ENSO.
There is also a scientific debate on the very existence of this "new" ENSO. A number of studies dispute the reality of this statistical distinction or its increasing occurrence, or both, either arguing the reliable record is too short to detect such a distinction,finding no distinction or trend using other statistical approaches, or that other types should be distinguished, such as standard and extreme ENSO.
Recent years when La Niña Modoki events occurred include 1973–74, 1975–76, 1983–84, 1988–89, 1998–99, 2000–01, 2008–09, 2010–11 and 2016–17.
El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific, including the area off the Pacific coast of South America. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean. El Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. El Niño phases are known to occur close to four years, however, records demonstrate that the cycles have lasted between two and seven years. During the development of El Niño, rainfall develops between September–November. The cool phase of ENSO is La Niña, with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall.
The quasi-biennial oscillation (QBO), is a quasiperiodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere with a mean period of 28 to 29 months. The alternating wind regimes develop at the top of the lower stratosphere and propagate downwards at about 1 km (0.6 mi) per month until they are dissipated at the tropical tropopause. Downward motion of the easterlies is usually more irregular than that of the westerlies. The amplitude of the easterly phase is about twice as strong as that of the westerly phase. At the top of the vertical QBO domain, easterlies dominate, while at the bottom, westerlies are more likely to be found. At the 30mb level, with regards to monthly mean zonal winds, the strongest recorded easterly was 29.55 m/s in November 2005, while the strongest recorded westerly was only 15.62 m/s in June 1995.
El Niño–Southern Oscillation (ENSO) is an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics. The warming phase of the sea temperature is known as El Niño and the cooling phase as La Niña. The Southern Oscillation is the accompanying atmospheric component, coupled with the sea temperature change: El Niño is accompanied by high air surface pressure in the tropical western Pacific and La Niña with low air surface pressure there. The two periods last several months each and typically occur every few years with varying intensity per period.
The Pacific Decadal Oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals corresponded with dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures from Alaska to California.
Climate variability is the term to describe variations in the mean state and other characteristics of climate "on all spatial and temporal scales beyond that of individual weather events." Some of the variability does not appear to be caused systematically and occurs at random times. Such variability is called random variability or noise. On the other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns.
The South Pacific Convergence Zone (SPCZ), a reverse-oriented monsoon trough, is a band of low-level convergence, cloudiness and precipitation extending from the Western Pacific Warm Pool at the maritime continent south-eastwards towards French Polynesia and as far as the Cook Islands. The SPCZ is a portion of the Intertropical Convergence Zone (ITCZ) which lies in a band extending east-west near the Equator but can be more extratropical in nature, especially east of the International Date Line. It is considered the largest and most important piece of the ITCZ, and has the least dependence upon heating from a nearby landmass during the summer than any other portion of the monsoon trough. The SPCZ can affect the precipitation on Polynesian islands in the southwest Pacific Ocean, so it is important to understand how the SPCZ behaves with large-scale, global climate phenomenon, such as the ITCZ, El Niño–Southern Oscillation, and the Interdecadal Pacific oscillation (IPO), a portion of the Pacific decadal oscillation.
The Madden–Julian oscillation (MJO) is the largest element of the intraseasonal variability in the tropical atmosphere. It was discovered in 1971 by Roland Madden and Paul Julian of the American National Center for Atmospheric Research (NCAR). It is a large-scale coupling between atmospheric circulation and tropical deep atmospheric convection. Unlike a standing pattern like the El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation is a traveling pattern that propagates eastward, at approximately 4 to 8 m/s, through the atmosphere above the warm parts of the Indian and Pacific oceans. This overall circulation pattern manifests itself most clearly as anomalous rainfall.
The Atlantic Multidecadal Oscillation (AMO), also known as Atlantic Multidecadal Variability (AMV), is a climate cycle that affects the sea surface temperature (SST) of the North Atlantic Ocean based on different modes on multidecadal timescales. While there is some support for this mode in models and in historical observations, controversy exists with regard to its amplitude, and in particular, the attribution of sea surface temperature change to natural or anthropogenic causes, especially in tropical Atlantic areas important for hurricane development. The Atlantic multidecadal oscillation is also connected with shifts in hurricane activity, rainfall patterns and intensity, and changes in fish populations.
The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.
Polar amplification is the phenomenon that any change in the net radiation balance tends to produce a larger change in temperature near the poles than the planetary average. On a planet with an atmosphere that can restrict emission of longwave radiation to space, surface temperatures will be warmer than a simple planetary equilibrium temperature calculation would predict. Where the atmosphere or an extensive ocean is able to transport heat polewards, the poles will be warmer and equatorial regions cooler than their local net radiation balances would predict.
The El Niño–Southern Oscillation affects the location of the jet stream, which alters rainfall patterns across the West, Midwest, the Southeast, and throughout the tropics. The shift in the jet stream also leads to shifts in the occurrence of severe weather, and the number of tropical cyclones expected within the tropics in the Atlantic and Pacific oceans affected by changes in the ocean temperature and the subtropical jet stream. The winter will have a negative phase according to the Arctic oscillation (AO).
Tropical instability waves, often abbreviated TIW, are a phenomenon in which the interface between areas of warm and cold sea surface temperatures near the equator form a regular pattern of westward-propagating waves. These waves are often present in the Atlantic Ocean, extending westward from the African coast, but are more easily recognizable in the Pacific, extending westward from South America. They have an average period of about 30 days and wavelength of about 1100 kilometers, and are largest in amplitude between June and November. They are also largest during La Niña conditions, and may disappear when strong El Niño conditions are present.
The Arctic dipole anomaly is a pressure pattern characterized by high pressure on the arctic regions of North America and low pressure on those of Eurasia. This pattern sometimes replaces the Arctic oscillation and the North Atlantic oscillation. It was observed for the first time in the first decade of 2000s and is perhaps linked to recent climate change. The Arctic dipole lets more southern winds into the Arctic Ocean resulting in more ice melting. The summer 2007 event played an important role in the record low sea ice extent which was recorded in September. The Arctic dipole has also been linked to changes in arctic circulation patterns that cause drier winters in Northern Europe, but much wetter winters in Southern Europe and colder winters in East Asia, Europe and the eastern half of North America.
The Atlantic Equatorial Mode or Atlantic Niño is a quasiperiodic interannual climate pattern of the equatorial Atlantic Ocean. It is the dominant mode of year-to-year variability that results in alternating warming and cooling episodes of sea surface temperatures accompanied by changes in atmospheric circulation. The term Atlantic Niño comes from its close similarity with the El Niño-Southern Oscillation (ENSO) that dominates the tropical Pacific basin. The Atlantic Niño is not the same as the Atlantic Meridional (Interhemispheric) Mode that consists of a north-south dipole and operates more on decadal timescales. The equatorial warming and cooling events associated with the Atlantic Niño are known to be strongly related to atmospheric climate anomalies, especially in African countries bordering the Gulf of Guinea. Therefore, understanding of the Atlantic Niño has important implications for climate prediction in those regions. Although the Atlantic Niño is an intrinsic mode to the equatorial Atlantic, there may be a tenuous causal relationship between ENSO and the Atlantic Niño in some circumstances.
The 2010–12 La Niña event was one of the strongest on record. It caused Australia to experience its wettest September on record in 2010, and its second-wettest year on record in 2010. It also led to an unusual intensification of the Leeuwin Current, the 2010 Pakistan floods, the 2010–11 Queensland floods, and the 2011 East Africa drought. It also helped keep the average global temperature below recent trends, leading to 2011 tying with 1997 for the 14th-warmest year on record. This La Niña event also led to above-average tropical cyclone activity in the North Atlantic Ocean during the 2010, 2011, and 2012 hurricane seasons.
The 2014–16 El Niño was a warming of the eastern equatorial Pacific Ocean that resulted in unusually warm waters developing between the coast of South America and the International Date Line. These unusually warm waters influenced the world's weather in a number of ways, which in turn significantly affected various parts of the world. These included drought conditions in Venezuela, Australia and a number of Pacific islands while significant flooding was also recorded. During the event, more tropical cyclones than normal occurred within the Pacific Ocean, while fewer than normal occurred in the Atlantic Ocean.
A westerly wind burst is a phenomenon commonly associated with El Niño events, whereby the typical east-to-west trade winds across the equatorial Pacific shift to west-to-east. A westerly wind burst is defined by Harrison and Vecchi (1997) as sustained winds of 25 km/h (16 mph) over a period of 5–20 days. However, no concrete definition has been determined, with Tziperman and Yu (2007) defining them as having winds of 14 km/h (8.7 mph) and lasting "at least a few days". On average, three of these events take place each year, but are significantly more common during El Niño years. They have been linked to various mesoscale phenomena, including tropical cyclones, mid-latitude cold surges, and the Madden–Julian oscillation. Their connection with Kelvin waves also indicate a connection with the onset of El Niño events, with every major occurrence since the 1950s featuring a westerly wind burst upon their onset.
Pacific Centennial Oscillation is a climate oscillation predicted by some climate models.
Cyclonic Niño is a climatological phenomenon that has been observed in climate models where tropical cyclone activity is increased. Increased tropical cyclone activity mixes ocean waters, introducing cooling in the upper layer of the ocean that quickly dissipates and warming in deeper layers that lasts considerably more, resulting in a net warming of the ocean.
Caroline C. Ummenhofer is a physical oceanographer at the Woods Hole Oceanographic Institution where she studies extreme weather events with a particular focus on the Indian Ocean. Ummenhofer makes an effort to connect her discoveries about predicting extreme weather events and precipitation to helping the nations affected.