La Niña

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La Niña is a coupled ocean atmosphere phenomenon that is counterpart to El Niño. The name means "little girl" in Spanish. La Niñas are often, though not always, preceded by an El Niño phenomenon. Weather patterns in the United States are usually different than during El Niño years. During La Niñas events, the Atlantic hurricane season produces more intense storms such as hurricanes than normal.

Background

El Niño and La Niña are part of the ENSO cycle that has been observed for centuries but understood in scientific terms only in the past hundred years. These terms represent opposite phases of sea surface temperature anomalies in the Pacific Ocean, each with distinct effects on global climate patterns, profoundly influencing weather, agriculture, and economies worldwide.

The Emergence of La Niña

La Niña, meaning “the girl,” refers to the counterpart of El Niño. While El Niño brings warmer-than-average sea surface temperatures, La Niña involves cooler-than-average temperatures in the central and eastern Pacific Ocean. This typically strengthens the trade winds, pushing cold water westward and intensifying weather patterns opposite to those associated with El Niño.

The concept of La Niña emerged more clearly in the 1980s, as scientists developed a deeper understanding of the full cycle, now known as the El Niño-Southern Oscillation (ENSO). ENSO includes both phases: the warm El Niño and the cool La Niña, as well as neutral phases in between.

Origins of El Niño

El Niño was first observed by Peruvian fishermen as early as the 1600s. They noticed that, every few years, the usually cold and nutrient-rich waters off the coast of South America would warm considerably, which diminished fish populations and disrupted marine life. These warm water events became particularly associated with the time around Christmas, thus earning the name El Niño.

It wasn't until the late 19th century that the phenomenon was studied more scientifically. British climatologist Sir Gilbert Walker, in the 1920s, was tasked with understanding the erratic monsoon patterns affecting British India. He noticed a connection between air pressure anomalies across the Pacific Ocean and these weather patterns, coining the term Southern Oscillation to describe the phenomenon, but it wasn’t directly linked to El Niño at the time.

By the 1960s and 1970s, researchers had developed a clearer understanding of how El Niño was part of a larger climate system. They discovered that during an El Niño event, trade winds weaken, allowing warm water to spread eastward across the Pacific Ocean, which alters global weather patterns, leading to increased rainfall in some areas and drought in others.

Global Impacts

Both phenomena have global implications. El Niño is associated with wetter conditions in the southern United States, South America, and eastern Africa, while La Niña tends to bring more drought-like conditions in those same areas but causes more rain in places like Southeast Asia and northern Australia. Both events can disrupt agricultural production, cause devastating floods or droughts, and lead to shifts in global temperatures.

Recent history

A strong La Niña hit in 1988-1989. A weaker one took place during 1995. An extended strong La Niña spell took place from 1998 to 2000, followed by neutral periods between 2000 and 2002. A more recent La Niña happened in 2007-2008, followed by neutral conditions in 2008-2009.