Severe drought in Australia over the past two years (ABC Chart)
For the first time since February 2018, the Australian Meteorological Agency has shifted the La Nina pointer to the "observation" level (Watch), further heralding Australia's potential to escape the dry climate. "To Australia, the La Nina phenomenon basically means an increase in rainfall, especially in central, eastern and northern Australia ," said Andrew Watkins (Andrew Watkins), director of long-term forecasting at the Met Office. "
The "watch" level means that La Nina is about 50% more likely to form this year, about twice the normal rate. "The La Nina phenomenon is a cooling phenomenon in the central and eastern tropical Pacific that, when coupled to the atmosphere, has an impact on the global climate, including on Australia ," said Dr Watkins. "In addition to increased rainfall, the La Nina phenomenon will increase the likelihood of flooding and tornadoes in Australia. "Looking at history, we'll find that about half of the La Nina events are accompanied by varying degrees of flooding ," Dr. Watkins said. "
Met Office first dials Lanina pointer to "observation" level (ABC chart) since February 2018
According to a new study co-authored by University of Melbourne climatologist Andrew King (Andrew King), La Nina is crucial to ending Australia's arid climate.
"La Nina is much more humid than El Niño or neutral ,". King said. "
At the time of the El Niño outbreak, the Pacific Ocean near Australia had lower temperatures, which reduced the likelihood of rainfall.
Dr king reviewed climate data for more than a century and found that australia's arid climate is closely related to the lack of two major rainfall climate drivers: the laina phenomenon and the negative growth of the indian ocean dipole (IOD), a phenomenon similar to the lanina in the indian ocean.
"Compared to El Niño or El Niño/Southern Oscillation (ENSO) neutral seasons, the La Niña season is more likely to have rainfall that ends the dry climate ," Kim said. The appearance of La Nina phenomenon will produce more water and bring more rainfall. It is the lack of conditions related to the La Nina phenomenon that makes the drought situation in Australia intensified. "
The last truly wet winter in australia will be track back until 2016, the fourth rainy winter in the history of theray basin (Murray–Darling basin), dr. kim said. That winter, the Indian Ocean dipole showed strong negative growth.
since then, except for the weak lanina event in the summer of 2017-18, there has been no obvious negative growth of indian ocean dipole or lanina phenomenon. At the same time, rainfall fell below average for 12 consecutive quarters in the Mordadaling Basin, the longest period since 1900. the basin experienced three consecutive dry winters in 2017,2018, and 2019, the longest since 1900.
"This fall, the humidity in the Mordadaling basin was slightly above normal levels and ended the record of successive dry seasons ," Dr. King said. According to Met Office data, the above-average humidity in the region during the first five months of 2020 has somewhat alleviated short-term water shortages in much of eastern Australia.
The more in-depth Dr King's study of Australia's weather records over the past 100 years, the more he found that many of the major droughts in Australia's history, including the severe droughts that erupted during the millennium and the Second World War, coincided with the long-term lack of La Nina and negative growth of Indian dipoles.
So climatologists are now welcoming the possible return of La Nina, which Dr Kim said :" While there is no guarantee that there will be La Nina, it's certainly good news, which should mean that large parts of eastern Australia will probably be wetter than normal, which have been dry before. "
