Overestimated Eddy Kinetic Energy in the Eddy‐Rich Regions Simulated by Eddy‐Resolving Global Ocean–Sea Ice Models
The performance of eddy-resolving global ocean–sea ice models in simulating mesoscale eddies is evaluated using six eddy-resolving experiments forced by different atmospheric reanalysis products. Interestingly, eddy-resolving ocean general circulation models (OGCMs) tend to simulate more (less) energetic eddy-rich (eddy-poor) regions with a smaller (larger) spatial extent than satellite observation, which finally shows that larger (smaller) mesoscale energy intensity (EI) is simulated in the eddy-rich (eddy-poor) regions. Quantitatively, there is an approximately 27%–60% overestimation of EI in the eddy-rich regions, which are mainly located in the Kuroshio–Oyashio Extension, the Gulf Stream, and the Antarctic Circumpolar Currents regions, although the global mean EI is underestimated by 25%–45%. Apparently, the eddy kinetic energy in the eddy-poor region is underestimated. Further analyses based on coherent mesoscale eddy properties show that the overestimation in the eddy-rich regions is mainly attributed to mesoscale eddies’ intensity and is more prominent when mesoscale eddies are in their growth stage.
This study aims to investigate the performance of the eddy-resolving OGCMs in simulating the mesoscale eddies against the satellite altimetry data set using both EKE and mesoscale eddy properties (number, lifetime, amplitude, and radius). The results indicate that models overestimate the EKE in eddy-rich regions mainly due to the contributions of coherent mesoscale eddies’ intensity rather than frequency and this overestimation is more prominent when mesoscale eddies are in their growth stage. Our results give an in-depth understanding of how well eddy-resolving OGCMs can perform in simulating the observed mesoscale eddies on the regional scale.
Here, we investigate the performance of eddy-resolving OGCMs in simulating the density of mesoscale eddies using EKE under the Eulerian framework from four eddy-resolving experiments following the OMIP-2 protocol and two additional experiments of IAP-LICOM forced by different atmospheric reanalysis products and eddy properties under the Lagrangian framework from two experiments of IAP-LICOM. Results show that although the eddy-resolving OGCMs can capture the spatial characteristics of mean global mesoscale variability, the global surface EI is underestimated by approximately 25%–45%, except for the FSU-HYCOM_JRA_uv. That is similar to the previous studies, such as Chassignet et al. (2020). We further divide the global ocean into eddy-rich and eddy-poor regions according to the global spatial STD in each mean EKE distribution. We find that the eddy-resolving OGCMs tend to simulate more (less) energetic eddies in eddy-rich (eddy-poor) regions with a smaller (larger) spatial coverage based on the metric EKE. In general, the eddy-resolving OGCMs simulate an approximately 27%–60% larger EI than the observed ones in the eddy-rich regions. Coincidently, the spatial coverage of the eddy-rich regions takes only 11%–15% of the global ocean in five out of six model simulations which is 5%–10% less than the observation (the exception is FSU-HYCOM_JRA). After the coherent eddies are identified, the eddy properties show that the overestimation of EKE in the eddy-rich regions is more contributed by the mesoscale eddy intensity than eddy frequency and is more prominent when mesoscale eddies are in their growth stage.