El Nino and La Nina

Summary

The El Niño Southern Oscillation (ENSO) is a major climate driver, influencing weather patterns globally. Comprising three phases—neutral, El Niño, and La Niña—ENSO impacts weather in regions like Australia, with El Niño linked to droughts and bushfires, and La Niña to heavy rainfall and tropical cyclones. These cycles, lasting 6 to 12 months, are driven by trade winds pushing warm waters across the Pacific Ocean, affecting atmospheric circulation. Understanding ENSO helps manage risks like extreme weather events. Notable occurrences include the devastating 1997-98 El Niño and the 2010-2011 La Niña, each having significant global effects.

Takeaways

• 😀 ENSO (El Niño-Southern Oscillation) is a major climate driver, affecting weather patterns globally from America to Antarctica and Australia.
• 😀 El Niño is known as 'the little boy' in Spanish, while La Niña is 'the little girl', with the in-between phase being neutral.
• 😀 The transition between El Niño, La Niña, and neutral phases forms the ENSO, which significantly influences weather events like droughts, floods, and cyclones.
• 😀 El Niño and La Niña events typically last 6 to 12 months and cycle approximately every four years, although no two events are identical.
• 😀 A La Niña event brings above-average rainfall to eastern Australia, while an El Niño event increases the risk of droughts and bushfires.
• 😀 The movement of warm surface waters across the Pacific Ocean creates predictable atmospheric and oceanic circulation patterns.
• 😀 Trade winds in the Pacific push warm waters from east to west, leading to upwelling of cold, nutrient-rich waters in the eastern Pacific, which supports marine ecosystems.
• 😀 La Niña is the more intense phase of ENSO, where stronger trade winds create more warm water accumulation in the western Pacific, driving tropical cyclones and floods in eastern Australia.
• 😀 During El Niño, the trade winds weaken, causing warm waters to shift back east, reducing rainfall in northern and eastern Australia and suppressing tropical cyclone formation.
• 😀 El Niño events can have devastating global impacts, such as droughts, heatwaves, and floods, with the 1997-98 event being one of the strongest and most destructive in recorded history.

Q & A

What is the El Nino Southern Oscillation (ENSO)?

The El Nino Southern Oscillation (ENSO) is a climate pattern that involves the cyclical phases of El Nino, La Nina, and neutral conditions. It plays a major role in influencing weather patterns worldwide, from the Americas to Australia, and is a key driver of climate variability.

How does ENSO affect Australia's climate?

ENSO significantly impacts Australia's climate by causing extreme weather events. El Nino is associated with droughts, heat waves, and bushfires, while La Nina typically brings above-average rainfall and increases the risk of floods and tropical cyclones.

What are the main phases of ENSO?

The three main phases of ENSO are El Nino, La Nina, and neutral. El Nino tends to bring warmer, drier conditions, while La Nina is characterized by cooler, wetter conditions. The neutral phase is the transitional state between these two.

How long does each ENSO event typically last?

Each ENSO event, whether it is El Nino or La Nina, typically lasts between 6 to 12 months, and the cycle between El Nino and La Nina usually takes about four years to complete.

What causes the changes between El Nino and La Nina?

The changes between El Nino and La Nina are caused by variations in the strength of trade winds. When these winds weaken or reverse, it allows warm water to move eastward across the Pacific Ocean, leading to the development of El Nino. Stronger trade winds, in contrast, lead to La Nina.

What are the atmospheric circulation patterns involved in ENSO?

The atmospheric circulation patterns associated with ENSO include the Walker Circulation, which is driven by the movement of warm air rising in the western Pacific. This circulation influences both ocean and atmospheric patterns across the globe, contributing to weather extremes during El Nino and La Nina events.

How does the warm water buildup in the western Pacific affect the climate?

The buildup of warm water in the western Pacific, driven by trade winds, causes increased evaporation and precipitation. This leads to more intense rainfall, floods, and tropical cyclones, particularly in the eastern parts of Australia during La Nina.

What are the effects of El Nino on tropical cyclones?

During an El Nino event, the risk of tropical cyclones is generally reduced in the Australian region as the concentration of tropical activity shifts eastward, off the coast of South America. The suppression of upwelling of cold waters further exacerbates this reduction.

What were the global impacts of the 1997-98 El Nino event?

The 1997-98 El Nino event had widespread global impacts, causing extreme weather conditions, such as droughts, bushfires, and heat waves in some regions, while other areas experienced floods and hurricanes. This event caused significant damage to ecosystems and economies worldwide.

How does La Nina benefit marine species like the western rock lobster?

During La Nina, the Lewin current, a flow of warm waters along the Western Australian coast, is stronger and helps marine species like the western rock lobster. The current aids in the movement of lobster larvae, leading to greater numbers settling on the ocean floor, benefiting fisheries.