ENSO teleconnections in eddy-rich climate models

The representation of El Niño-Southern Oscillation (ENSO) atmospheric teleconnections is investigated in a new set of multi-decadal simulations that combine an eddy-resolving ocean with a high-resolution atmosphere, both at an unprecedented horizontal resolution of ~10 km. The experiments were produced using three different models run under a coordinated protocol within the European Eddy-RIch Earth System Models (EERIE) project. The impact of high resolution on ENSO teleconnections is unsettled, and no assessment has been carried out so far using climate simulations at the 10-km scale employed here.

Model fidelity is evaluated using a set of diagnostics designed to capture key components of ENSO teleconnections, including the tropical atmospheric response, Rossby wave generation, extratropical tropospheric and stratospheric circulation anomalies, and associated surface signals. These diagnostics are further applied to atmosphere-only experiments at low (~30 km) and high (~10 km) resolution, which are used to assess the impact of atmospheric resolution alone.

The coupled EERIE simulations show heterogeneous results relative to previous models with coarser grids (maximum 25 km). While the overall performance is positive, it depends on the season, region, and model configuration. Consistent with this, the atmosphere-only experiments suggest only modest gains from enhanced atmospheric resolution. The results are placed in the context of uncertainty in the ENSO response associated with internal variability and sampling, which may hinder potential benefits.