Purpose of Review
The El Niño-Southern Oscillation (ENSO) phenomenon exhibits considerable diversity in the amplitude, pattern, and temporal evolution. The processes causing ENSO diversity are reviewed with focus on the role of atmospheric feedback.
Recent Findings
Due to the zonal and meridional asymmetry in tropical Pacific climate, atmospheric response to sea surface temperature (SST) anomalies is highly nonlinear. This leads to diversity in the amplitude and pattern of El Niño, as well as asymmetry in the pattern and duration of El Niño and La Niña. Atmospheric convection changes associated with tropical Pacific decadal variability may modulate ENSO diversity. Furthermore, variability in the Indian and Atlantic Oceans provides additional sources of ENSO diversity through pan-tropical adjustments of atmospheric convection.
Summary
The complexity of atmospheric feedback plays an important role in ENSO diversity, but is poorly represented in the Bjerknes feedback. Incorporating convective threshold in defining SST anomalies may help explain various features of ENSO diversity in a unified framework.