La Niña (; ) is an oceanic and atmospheric phenomenon that is the colder counterpart of as part of the broader

El Niño–Southern Oscillation El Niño–Southern Oscillation (ENSO) is an irregular 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 te ...

(ENSO)

climate pattern Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more ...

. The name ''La Niña'' originates from Spanish for "the girl", by analogy to ''El Niño'', meaning "the boy". In the past, it was also called an ''anti-El Niño'' and ''El Viejo'', meaning "the old man." During a La Niña period, the sea surface temperature across the eastern equatorial part of the central

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

will be lower than normal by 3–5 °C (5.4–9 °F). An appearance of La Niña often persists for longer than five months. El Niño and La Niña can be indicators of weather changes across the globe.

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and

Pacific hurricanes A Pacific hurricane is a mature tropical cyclone that develops within the northeastern and central Pacific Ocean to the east of 180°W, north of the equator. For tropical cyclone warning purposes, the northern Pacific is divided into three regio ...

can have different characteristics due to lower or higher

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizont ...

and cooler or warmer sea surface temperatures.

Background

ImageSize = width:800 height:70 PlotArea = left:50 bottom:20 width:700 height:40 Period = from:1900 till:2022 DateFormat = yyyy TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:1900 PlotData = bar:laniña width:30 color:blue mark:(line,white) from:1903 till:1904 from:1906 till:1907 from:1909 till:1911 from:1916 till:1918 from:1924 till:1925 from:1928 till:1930 from:1938 till:1939 from:1942 till:1943 from:1949 till:1951 from:1954 till:1957 from:1964 till:1965 from:1967 till:1968 from:1970 till:1972 from:1973 till:1974 from:1974 till:1976 from:1983 till:1984 from:1984 till:1985 from:1988 till:1989 from:1995 till:1996 from:1998 till:2001 from:2005 till:2006 from:2007 till:2008 from:2008 till:2009 from:2010 till:2012 from:2016 till:2017 from:2017 till:2018 from:2020 till:2022 A timeline of all La Niña episodes between 1900 and 2022.

La Niña is a complex weather pattern that occurs every few years, as a result of variations in ocean temperatures in the equatorial band of the

, The phenomenon occurs as strong winds blow warm water at the ocean's surface away from South America, across the Pacific Ocean towards Indonesia. As this warm water moves west, cold water from the deep sea rises to the surface near South America; it is considered to be the cold phase of the broader

(ENSO) weather phenomenon, as well as the opposite of weather pattern. The movement of so much heat across a quarter of the planet, and particularly in the form of temperature at the ocean surface, can have a significant effect on weather across the entire planet. Tropical instability waves visible on sea surface temperature maps, showing a tongue of colder water, are often present during neutral or La Niña conditions. La Niña events have occurred for hundreds of years, and occurred on a regular basis during the early parts of both the 17th and 19th centuries. Since the start of the 20th century, La Niña events have occurred during the following years:

Impacts on the global climate

La Niña impacts the global climate and disrupts normal weather patterns, which can lead to intense storms in some places and droughts in others.

Regional impacts

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 these periods, it is not certain or guaranteed that they will occur.

Africa

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.

Asia

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. In March 2008, La Niña caused a drop in sea surface temperatures over Southeast Asia by . It also caused heavy rains over

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

, the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

, and

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

Australia

Across most of the continent, El Niño and La Niña have more impact on climate variability than any other factor. There is a strong correlation between the strength of La Niña and rainfall: the greater the sea surface temperature and

Southern Oscillation Southern may refer to: Businesses * China Southern Airlines, airline based in Guangzhou, China * Southern Airways, defunct US airline * Southern Air, air cargo transportation company based in Norwalk, Connecticut, US * Southern Airways Express, ...

difference from normal, the larger the rainfall change.

North America

La Niña causes mostly the opposite effects of El Niño: above-average

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

across the northern Midwest, the northern Rockies, Northern California, and the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Tho ...

'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 Tehuantepecer, or Tehuano wind, is a violent mountain-gap wind that travels through the Chivela Pass in southern Mexico, across the Isthmus of Tehuantepec. It is most common between October and February, with a summer minimum in July. It originat ...

winds is associated with

high-pressure system A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...

forming in

Sierra Madre Sierra Madre (Spanish, 'mother mountain range') may refer to: Places and mountains Mexico *Sierra Madre Occidental, a mountain range in northwestern Mexico and southern Arizona *Sierra Madre Oriental, a mountain range in northeastern Mexico *S ...

of Mexico in the wake of an advancing cold front, which causes winds to accelerate through the

Isthmus of Tehuantepec The Isthmus of Tehuantepec () is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean. Before the opening of the Panama Canal, it was a major overland transport route known simply as the T ...

. 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 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 the La Niña winter of 2007–2008 in eastern Canada. In the spring of 2022, La Niña caused above-average precipitation and below-average temperatures in the state of Oregon. April was one of the wettest months on record, and La Niña effects, while less severe, were expected to continue into the summer.

South America

During a time of La Niña, drought plagues the coastal regions of Peru and Chile. From December to February,

northern Brazil The North Region of Brazil ( pt, Região Norte do Brasil; ) is the largest region of Brazil, corresponding to 45.27% of the national territory. It is the second least inhabited of the country, and contributes with a minor percentage in the national ...

is wetter than normal. La Niña causes higher than normal rainfall in the central

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

, 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.

Diversity

The ‘traditional’ or conventional La Niña is called an ''Eastern Pacific'' (EP) La Niña; it involves temperature anomalies in the eastern Pacific. However, aside from differences in diagnostic criteria, non-traditional La Niñas were observed in the last two decades, in which the usual place of the temperature anomaly (Niño 1 and 2) is not affected, but rather 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 A dateline is a brief piece of text included in news articles that describes where and when the story was written or filed, though the date is often omitted. In the case of articles reprinted from wire services, the distributing organization i ...

), or La Niña "Modoki" ("Modoki" is Japanese for "alternate / meta / similar-but-different"). These "flavors" of ENSO are in addition to EP and CP types, leading some scientists argue that ENSO is a continuum of phenomena – often with hybrid types. The effects of the CP La Niña similarly contrast with the EP La Niña – it strongly tends to increase rainfall over northwestern Australia and northern

Murray–Darling basin The Murray–Darling basin is a large geographical area in the interior of southeastern Australia, encompassing the drainage basin of the tributaries of the Murray River, Australia's longest river, and the Darling River, a right tributary of ...

, 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 The Bay of Bengal is the northeastern part of the Indian Ocean, bounded on the west and northwest by India, on the north by Bangladesh, and on the east by Myanmar and the Andaman and Nicobar Islands of India. Its southern limit is a line betwee ...

, but decreases the occurrence of severe storms in the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

overall, with the

Arabian Sea The Arabian Sea ( ar, اَلْبَحرْ ٱلْعَرَبِيُّ, Al-Bahr al-ˁArabī) is a region of the northern Indian Ocean bounded on the north by Pakistan, Iran and the Gulf of Oman, on the west by the Gulf of Aden, Guardafui Channel ...

becoming severely non-conducive to tropical cyclone formation. Recent years when La Niña Modoki events occurred include 1973–1974, 1975–1976, 1983–1984, 1988–1989, 1998–1999, 2000–2001, 2008–2009, 2010–2011, and 2016–2017. 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 or if

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

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.

Footnotes

References

External links

* * * {{DEFAULTSORT:La Nina Regional climate effects Tropical meteorology Physical oceanography Weather hazards Pacific Ocean Spanish words and phrases