BOM Has Made It Official: La Niña Is Here For A Third Year
The Bureau of Meteorology has made it official: yep, La Niña is underway for the third year in a row.
This means we can expect above-average rainfall during spring and summer in the northern and eastern parts of Australia.
— Peter Hannam (@p_hannam) September 13, 2022
“What is intriguing is that this triple La Niña event happened without a preceding El Niño strong event… So it’s quite unusual to see this triple event appearing now,” Dr. Andréa S. Taschetto from the Climate Change Research Centre at University of New South Wales told Junkee.
Just in case you’ve forgotten what El Niño and La Niña events are, they are basically the opposite of each other.
“So El Niños and La Niñas are part of the El Niño Southern Oscillation phenomenon — a natural phenomenon — and now a climate system. So they appear every three to seven years in the tropical Pacific. When El Niño happens, it tends to discharge ocean heat away from the equatorial Pacific. And when La Niña comes, it tends to restore this ocean heat to the equatorial Pacific. So we can think of it as a natural cycle,” Dr Andréa Taschetto said.
Sometimes what happens is that a stronger El Niño occurs and the ocean heat is kind [of] too much, Dr Andréa explained. And so a La Niña or two La Niñas are needed to restore and reduce this ocean heat. But Australia hasn’t had an El Niño event for 6 or 7 years, which makes the triple weather event all the more rare.
In fact there’s only been two or three, depending on what record you go by, (I’d suggest brackets here instead commas, but commas is still technically fine! Just looks a bit confusing) triple La Niñas that have occurred since the 1950s. It occurred in 1973 to 1976 and then again in 1998 to 2001.
“It has impacts not only over Australia, but it impacts South America, North America [and] East Africa. So it’s quite interesting that this phenomenon that occurs in the tropical Pacific has this massive disruption in the atmospheric circulation that causes impact everywhere,” Dr Taschetto pointed out.
While people are quick to point the finger at La Niña for wreaking all the havoc, it’s not actually just Niña that is affecting Australia’s climate at the moment.
A trio of climate drivers will increase the likelihood of above average rain over the eastern half of Australia this spring. pic.twitter.com/HxWQ2oEP3F
— Ben Domensino (@Ben_Domensino) September 2, 2022
There are two other natural climate forces that are at play here, which are the Indian Ocean Dipole and the Southern Annular Mode. The Indian Ocean Dipole is made up of sea surface temperatures in the Indian Oceans and it’s going through a “negative” event. Meanwhile the Southern Annular Mode, which is characterised by the positioning of winds and weather systems to Australia’s south, is in a “positive” phase.
“So it’s the impact of three main climate drivers at the moment is what we are seeing. And that’s just what is increasing the chances of rain for the Eastern side and Southeast parts of Australia.”
It is too early to say where exactly in Australia is likely to experience flooding this spring or summer, but for communities like Lismore this news most likely brings on big feelings of anxiety.
“There’s been heavy rainfall and floods in that area. So, stream flows are high, soil moisture is high and saturated in some areas. And we know that La Niña increases the chance of rainfall for those areas….so the risks of floods are real.”