Seasonal Gap Theory for ENSO Phase Locking

Abstract The life cycle of El Niño-Southern Oscillation (ENSO) typically follows a seasonal march, onset in spring, developing during summer, maturing boreal winter, and decaying over the following spring. This feature is referred to as ENSO phase locking. Recent studies have noted that modulation growth rate essential for this process. study investigates fundamental effect seasonally varying on locking using modified seasonally-dependent recharge oscillator model. There are two regimes associated with strength rate: (1) weak regime which only single peak occurs; (2) strong types events occur either or double peak. Notably, there gap regime, cannot because large-scale ocean-atmosphere coupled processes. We also retrieve simple analytical solution variance ENSO, revealing governed by time-integral rate. Based formulation, we propose energy index (SEI) allows explaining gap, provides an intuitive explanation locking, potentially applicable global climate model diagnostics.