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
Sea surface temperature (SST), or ocean surface temperature, is the ocean temperature close to the surface. The exact meaning of ''surface'' varies according to the measurement method used, but it is between and below the sea surface. Air mass ...
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 continen ...
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 horizontal ...
and cooler or warmer sea surface temperatures.
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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
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 continen ...
,
[ 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 ]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) 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
A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...
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 Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of ...
, the northern Rockies
The Northern Rocky Mountains, usually referred to as the Northern Rockies, are a subdivision of the Canadian Rockies comprising the northern half of the Canadian segment of the Rocky Mountains. While their northward limit is easily defined as th ...
, Northern California
Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...
, 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. Though ...
'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 Te ...
. 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
Beni (), sometimes El Beni, is a northeastern department of Bolivia, in the lowlands region of the country. It is the second-largest department in the country (after Santa Cruz), covering 213,564 square kilometers (82,458 sq mi), and it was cre ...
, 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 between ...
, 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 th ...
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 E ...
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.
See also
* 2000 Mozambique flood (attributed to La Niña)
* 2010 Pakistan floods (attributed to La Niña)
* 2010–2011 Queensland floods
A series of floods hit Queensland, Australia, beginning in November 2010. The floods forced the evacuation of thousands of people from towns and cities. At least 90 towns and over 200,000 people were affected. Damage initially was estimated at ...
(attributed to La Niña)
* 2010–2012 La Niña event
* 2010–2011 Southern Africa floods (attributed to La Niña)
* 2010–2013 Southern United States and Mexico drought (attributed to La Niña)
* 2011 East Africa drought (attributed to La Niña)
* 2020 Atlantic hurricane season
The 2020 Atlantic hurricane season featured a total of 31 tropical or subtropical cyclones, making it the most active Atlantic hurricane season on record. All but one cyclone became a named storm. Of the 30 named storms, 14 deve ...
(unprecedented severity fueled by La Niña)
* 2021 New South Wales floods (severity fueled by La Niña)
* March 2022 Suriname flooding (attributed to La Niña)
* Ocean dynamical thermostat
* Walker circulation
The Walker circulation, also known as the Walker cell, is a conceptual model of the air flow in the tropics in the lower atmosphere (troposphere). According to this model, parcels of air follow a closed circulation in the zonal and vertical dir ...
Footnotes
References
External links
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{{DEFAULTSORT:La Nina
Regional climate effects
Tropical meteorology
Physical oceanography
Weather hazards
Pacific Ocean
Spanish words and phrases