What’s El Niño and La Niña? 厄爾尼諾? 拉尼娜? 聖嬰?

生字 learn from these videos:

Extreme natural events

Bush fire 山火

Heat waves

Drought 乾旱

Floods

Cyclones

coral bleaching (珊瑚白化)

Reference:El Niño Southern Oscillation (ENSO)

Swing (shifts/ changes) between phases

1. El Nino
2. Neutral
3. La Nina

Notes: can divided into more phases, but in general, there are three “status”.

Knowledge from this clip:

Effect of La Nina event

Eastern pacific ocean, trade wind blowing from east to west, push warm surface water to western pacficic ocean. Then, the water in western Pacific ocean is relatively warmer than eastern Pcific ocean. Above the sea, on the surface, warm air rises and then cause an atmospheric circulation patterns (known as “Walker circulation“).

• La Nina event tends to bring above-average rainfall to eastern Australia;

Effect of El Nino event 

When the trade wind weakening (the “Walker circulation” breaks down”), or even reversing, then the warm water will piles up at the middle of the Pacific ocean.

• Eastern Australia, there is a greater chance of droughts and bush fires
• Cost of South America or somewhere nearby (e.g Phenoix, Arizona) has relatively more above-average rainfall, floods, and even hurricanes

Cycle of La Nian / El Nino events and the pattern

• Each La Nian / El Nino events lasts about 6-12 months and it takes on average 4 years to cycle from one to another and back again

Knowledge from this clip:

• El Nino event occurs when the sufrace temperature at equatorial Pacific Ocean rises 0.5 degree Celsius in three consecutive months, plus (and) the rainfall patterns and atmospheric conditions have significant changes.

Also reference:El Niño Explained: Understanding the Forces Shaping 2023-24 Winter Weather  | Smithsonian Ocean (si.edu)

How can scientists predict El Niño events?  
El Niño and La Niña are classified by precise measurements of the water temperatures in the east-central equatorial Pacific Ocean. El Niño events occur when there is a temperature increase of at least 0.5 degrees Celsius across five overlapping three-month periods. These temperature measurements are taken by National Oceanic and Atmospheric Administration (NOAA) buoys equipped with thermometers, which are in about 70 locations. El Niño events can also be anticipated via National Aeronautics and Space Administration (NASA) satellite measurements that detect sea surface height (the ocean height rises as temperatures warm up, since warmer water expands to fill more volume). Scientists then use the Oceanic Niño Index to measure deviations from normal sea surface temperature. The higher the temperature changes, the “stronger” the El Niño, according to the Oceanic Niño Index. Informally, a 0.5–0.9 degree Celsius change equates to a weak El Niño, a 1.0–1.4  degree Celsius change moderate, above 1.5 degrees Celsius for a strong El Niño, and over 2.0 degrees Celsius for a “historically strong” effect.

Knowledge from this clip:

• Upwelling is a process in which deep, cold water rises toward the surface.

Also reference: What is upwelling? (noaa.gov)

Other reference:

More –

Check the current ENSO outlook – wheter it is La Niña or El Nino:

ENSO Outlook – an alert system for the El Niño–Southern Oscillation (bom.gov.au)