Mesoscale Eddy Verification in an Eddy-Permitting Ocean Models and Reanalysis Data

Ocean mesoscale eddies are ubiquitous features of the open ocean and strongly influence the ocean’s physics, chemistry, and biology. Mesoscale eddies play a critical role in the climate system and regulating the exchange of heat and carbon with the atmosphere. They also play a significant role in the redistribution of heat, salt, carbon, and nutrients around the ocean. Thus, proper modeling of eddies in both historical and future climates is crucial to accurately capturing the Earth system. Climate projections using global coupled models with eddy ocean components have recently started to become more widely used. Despite their critical role in understanding and forecasting climate characteristics, these so-called eddy-permitting models have not been rigorously explored to verify that resolved eddies are realistic, and thus any downstream scientific testing of hypotheses in biogeochemistry, ocean physics or other associated Earth systems impacted by eddies hinge on this critical assumption. This presentation compares the characteristics and behavior of observed eddies in ¼ degree satellite altimetry data with eddies detected in ¼ degree reanalysis data and ocean model output. 

When compared to eddies observed in satellite altimetry data, eddies in reanalysis data and ocean model output are missing almost 30% of the number of eddy trajectories. Further, many characteristics of eddies in reanalysis data and ocean model output differ from eddies observed in altimetry data. At a high level, eddies in reanalysis data and ocean model output generally live longer, are larger, and are weaker than observed eddies in satellite altimetry data. These comparisons are made both locally and in the global aggregate to assess the differences in both the global distribution of eddy characteristics as well as differences in the regional eddy behavior.