Linking ENSO to Synoptic Weather Systems in Eastern Australia

El Niño‐Southern Oscillation (ENSO) is the main driver of interannual east Australian rainfall variability, but its link with rain‐producing synoptic weather systems is unclear. By tracking low pressure systems in ERA5 over 1979 to 2021, we find that springtime cyclones are linked to variations in t...

Full description

Saved in:
Bibliographic Details
Published in:Geophysical research letters 2023-08, Vol.50 (15), p.n/a
Main Authors: Gillett, Z. E., Taschetto, A. S., Holgate, C. M., Santoso, A.
Format: Article
Language:English
Subjects:
Air flow
Atmospheric circulation
Atmospheric precipitations
Circulation
Cyclones
Cyclonic circulation
Dipoles
Drought
El Nino
El Nino events
El Nino phenomena
El Nino-Southern Oscillation event
La Nina
La Nina events
Low pressure
Low pressure systems
Moisture
Moisture effects
Planetary waves
Precipitation
Pressure
Rain
Rainfall
Rainfall variability
Rossby waves
Southern Hemisphere
Southern Oscillation
Spring
Spring (season)
Teleconnection patterns
Teleconnections
Tracking
Tropical circulation
Variability
Weather
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:El Niño‐Southern Oscillation (ENSO) is the main driver of interannual east Australian rainfall variability, but its link with rain‐producing synoptic weather systems is unclear. By tracking low pressure systems in ERA5 over 1979 to 2021, we find that springtime cyclones are linked to variations in the large‐scale atmospheric circulation during ENSO events. On spring days with a cyclone during La Niña, a pressure dipole occurs with a strong anticyclonic anomaly southeast of Australia and a cyclonic anomaly over eastern Australia. The northeasterly circulation directs tropical moisture toward eastern Australia, and coupled with induced ascent, promotes rainfall in this region. Both dynamical and thermodynamical changes are important for the rainfall response. An almost opposite circulation response occurs on cyclone days during El Niño events: high‐pressure over the Australian continent reduces rainfall in eastern Australia. These synoptic setups resemble the seasonal‐mean Rossby wave teleconnections, indicating a link between weather systems and ENSO. Plain Language Summary El Niño‐Southern Oscillation (ENSO) is the main driver of year‐to‐year rainfall variability in eastern Australia. La Niña is generally associated with increased rain and flooding, while El Niño is associated with a reduced likelihood of rain and sometimes drought. However, ENSO is a large‐scale phenomenon that persists on timescales longer than the day‐to‐day weather systems that are responsible for producing rain in this region. In this study, we examine differences in the characteristics of low‐pressure systems or cyclones on daily timescales between El Niño and La Niña events in Southern Hemisphere spring. We find that during La Niña, on days when a cyclone is present over eastern Australia, a high‐pressure system also occurs to the southeast of Australia in the Tasman Sea. This setup is conducive to rainfall in the region as it promotes moisture transport from the tropical Pacific Ocean and upward air flow, both of which are essential ingredients for rain. In contrast, during El Niño, there is an almost opposite circulation response; notably high‐pressure over the Australian continent reduces rainfall in eastern Australia. These patterns on daily timescales resemble the seasonal‐mean teleconnection patterns, thus indicating a link between weather systems and ENSO. Key Points Rain‐producing weather systems in eastern Australia are linked to the El Niño‐Southern Oscillation (ENSO) via
ISSN:0094-8276
1944-8007
DOI:10.1029/2023GL104814