EGU22-3263
https://doi.org/10.5194/egusphere-egu22-3263
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Asymmetries in the ENSO phase space

Dietmar Dommenget and Maryam Al Ansari
Dietmar Dommenget and Maryam Al Ansari
  • Monash University, School of Earth, Atmosphere and Environment, Atmospheric Science, Clayton, Australia (dietmar.dommenget@monash.edu)

El Niño Southern Oscillation (ENSO) dynamics are best described by the recharge oscillator model, in which the eastern tropical Pacific sea surface temperatures (T) and subsurface heat content (thermocline depth; h) have an out-of-phase relationship. This defines a 2-dimensional phase space diagram between T and h. In an idealized damped oscillator, the phase space diagram should be a perfectly symmetrical circle with a clockwise propagation over time. However, the observed phase space shows strong asymmetries in this diagram. In this study we will illustrate how the ENSO phase space can be used to discuss the phase-dependency of ENSO dynamics. The normalized spherical coordinate system allows to define a phase-depending ENSO growth rates and phase transition speeds. Based on these we discuss the implications of the observed asymmetries are for the dynamics and predictability of ENSO, with a particular focus on the variations in the growth rate and coupling of ENSO along the oscillation cycle.  Using linear and non-linear recharge oscillator models we will show how noise and internal dynamics are driving ENSO at different phases of the ENSO cycles. We will illustrate that a non-linear growth rate of T can explain most of the observed non-linear phase space characteristics.

How to cite: Dommenget, D. and Al Ansari, M.: Asymmetries in the ENSO phase space, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3263, https://doi.org/10.5194/egusphere-egu22-3263, 2022.

Displays

Display file