| 11 Feb 2026
ENSO teleconnections in eddy-rich climate models
Abstract. We examine how ENSO atmospheric teleconnections are represented in a novel suite of coupled simulations with eddy-resolving ocean and high-resolution atmosphere, at an unprecedented grid spacing of ∼10 km in both components. The single-member, multi-decadal experiments have been performed under a coordinated protocol within the European Eddy-RIch Earth System Models (EERIE) project using three different models.
To assess the performance of the EERIE models, we design tailored metrics to encapsulate and quantify different aspects of the ENSO teleconnections: direct tropical response, Rossby wave sources, extra-tropical tropospheric and stratospheric anomalies, and surface impacts. The metrics are based on linear regressions on the Niño3.4 index of several atmospheric fields in early- and late winter. Additionally, we apply the same diagnostics to a set of complementary atmosphere-only simulations run at lower resolution (∼30 km, 10 members) and high resolution (∼10 km, 1 member), which allow to isolate the impact of atmospheric resolution and estimate the internal variability.
We find mixed results in the EERIE coupled simulations compared to previous generation eddy-parametrized and eddy-permitting models (maximum ∼25 km in both atmosphere and ocean). The performance, though overall positive, varies by season, region, and model configuration and a systematic improvement does not emerge clearly. Similarly, the atmosphere-only experiments also indicate limited advances from the increased atmospheric resolution. However, potential benefits may be hindered by the large uncertainty in the ENSO response due to internal variability and sampling.
Review for "ENSO teleconnections in eddy-rich climate models" by Mezzina et al., 2026, submitted to WCD.
SUMMARY:
This study examines the ENSO atmospheric teleconnections mainly in three single-member eddy-rich coupled climate model experiments. A few metrics were created for the purpose of the evaluation. These includes responses over the tropical Pacific, north Pacific, the north Atlantic, and northern polar areas.
This should be an interesting and important study because of known problems in models reproduction of ENSO teleconnections and importance of ENSO teleconnections as sources of predictability, for example for seasonal to subseasonal forecasts.
Unfortunately, I find that there are serious weaknesses in the methodology and therefore the conclusions are not borne out by the results presented. For this reason, I could not (and would not) comment or ask question about the findings and conclusions regarding the performance of the models in terms of ENSO teleconnections.
The following major comments point to specific places in the manuscript where there are methodological issues.
MAJOR COMMENTS:
1. Lines 270 - 272, 294 - 296, 298 - 300, 301 - 302, 321 - 323, 326, etc: My criticism here is about the comparisons with ERA5 (or between model experiments). I assume the qualitative (better, best, worse, etc) comments from the comparisons are based on the mean values. The confidence levels, although shown on the figures, are not used in the evaluation nor discussed. There are substantial overlaps for these intervals.
I think at the very least there should be suitable statistical tests on the difference of the means between data with different variances. Statistical tests for climate teleconnections research is a standard thing to do.
In the current form of the analyses presented, I am unable to form an opinion for the validity of these evaluations.
2. Figures 2, 7: Are the longitudinal locations indicated the mean locations? What are ranges of variations in the longitudinal locations? Are the differences locations statistically significant?
3. Figure 10: I have doubt on the validity of the method used for these rankings, and that these rankings are robust. This is because of the same reason I give above. The relevant differences need to be checked for statistical signficance.
MINOR COMMENTS:
1. Section 2: Tables listing the model experiments and the main features for each would help give a clearer view.
2. Figure 2: Naming of experiments should be mentioned when they are described. See also my previous comment.
3. Line 231 (citing Fig. 10): For readability and convention, figures should be presented in order as they first referred to in the text. You jump from Fig. 2 to Fig. 10, and I had to scroll all the way to the end to find Fig. 10.
4. Line 302: Fig. 6d is for JF, not ND.
5. Line 366 "statically": statistically?
6. Supplementary figures: There are ten supplementary figures and they are cited extensively in description of the results and discussion in the main text. I don't think this is a correct use of supplementary figures. This affects the readability of the paper and processing of the information on the part of the reader. More attention is needed on what are the key results and focusing on presenting them nicely in the main body of the manuscript.