Tropical forcing of Australian extreme low minimum temperatures in September 2019

Abstract

We explore the causes and predictability of extreme low minimum temperatures (T ) that occurred across northern and eastern Australia in September 2019. Historically, reduced T is related to the occurrence of a positive Indian Ocean Dipole (IOD) and central Pacific El Niño. Positive IOD events tend to locate an anomalous anticyclone over the Great Australian Bight, therefore inducing cold advection across eastern Australia. Positive IOD and central Pacific El Niño also reduce cloud cover over northern and eastern Australia, thus enhancing radiative cooling at night-time. During September 2019, the IOD and central Pacific El Niño were strongly positive, and so the observed T anomalies are w..