Effect of atmospheric forcing resolution on the model fidelity of sea level variability in the North Pacific

This study examines the sensitivity of sea level variability in an ocean general circulation model to horizontal resolution of atmospheric surface forcing, focusing on the North Pacific. Two numerical simulations at 0.1o resolution were conducted using the Parallel Ocean Program (POP) model: atmospheric forcing for the first experiment has 0.6o resolution, while the second has 2o resolution. Skewness, kurtosis, and the spectral slope of sea surface height anomalies from the simulations are each compared with values from along-track altimeter data. The model-data comparison suggests that improving the resolution of atmospheric forcing can greatly improve the representation of sea level variability in the model at mid-latitudes away from the energetic western boundary current and its extension region, where the model is eddy-resolving and forcing contributes significantly to eddy generation. However, increasing the forcing resolution does not improve the fidelity of extreme sea level variability at high-latitudes, where the model is eddy-permitting only, and in the Kuroshio Extension system, where eddies are largely generated from instability processes and not from atmospheric forcing. We found that both ocean model resolution and nonlinearity influence the model response to the forcing resolution.