Asymmetries in the ENSO phase space

Abstract El Niño Southern Oscillation (ENSO) dynamics are best described by the recharge oscillator model, in which 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 . In idealized, stochastically forced damped oscillator, mean should be perfectly symmetrical circle with clockwise propagation over time. However, observed shows strong asymmetries. this study we illustrate how ENSO can used to discuss phase-dependency of dynamics. A normalized spherical coordinate system allows definition phase-depending growth rates transition speeds. Based on these implications asymmetries regards predictability ENSO; particular focus variations rate coupling along oscillation cycle. Using linear non-linear models will show noise driving at different phases cycles. The results that cycle positive transitions is present all but has its strength. Much result from presenting estimates based iso-thermal depth, not ideal as it Future work address estimated better, including aspects such vertical temperature gradients meridional or zonal range. We further illustrated explain most characteristics.