Characteristics of a Multi‐Model Ensemble of Mock‐Walker Simulations

Abstract The Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) phase I provided insights into the tropical radiative‐convective equilibrium state across an unprecedented ensemble of models that includes both those with parameterized and explicit convection. RCEMIP phase II (RCEMIP‐II) introduces mock‐Walker simulations to examine how sea surface temperature (SST) gradients and the forced circulation they theoretically induce interact with the structure of convection and mean climate state. This overview paper presents descriptions of and initial results from 17 numerical models regarding clouds, convective organization, and circulation structure. Results regarding warming the mean SST in the presence of an SST gradient generally mirror those from RCEMIP‐I but a larger range of dynamical circulations, along with additional phenomena, are possible in RCEMIP‐II. Increases in the SST gradient while the mean SST is held constant lead to more convective organization across many models, as measured by a number of organization metrics. Increases in the SST gradient also tend to decrease the frequency of high, thin clouds while increasing the frequency of low clouds, including the possibility of stratocumulus, which were not seen in RCEMIP‐I. RCEMIP‐II also provides an estimate of the influence of a pattern effect, suggesting increased negative climate feedbacks if increases in the SST gradient occur alongside mean warming. However, the SST gradient's inability to fully constrain the circulation structure allows simulations to show varying importance of self‐aggregation and forced clustering over the warm pool, resulting in extreme variety in the circulation structures and important climate variables in the organized state across the model ensemble.

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Journal
Journal of Advances in Modeling Earth Systems
Published
2026-07-30
DOI
https://doi.org/10.1029/2026ms005781
Primary Topic
Climate variability and models
Type
article
Field-Weighted Citation Impact
0.00

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article

Characteristics of a Multi‐Model Ensemble of Mock‐Walker Simulations

Guy Dagan, Gabrielle R. Leung, Allison A. Wing, Peter Hill et al.
Journal of Advances in Modeling Earth Systems
Climate variability and models
article

Characteristics of a Multi‐Model Ensemble of Mock‐Walker Simulations

Guy Dagan, Gabrielle R. Leung, Allison A. Wing, Peter Hill, David M. Romps, Shuhei Matsugishi, Jean‐Pierre Chaboureau, Jacob Shpund, Sebastián Ortega, Romain Roehrig, Romain Fiévet, Adam B. Sokol, Kevin A. Reed, Lorenzo Tomassini, Walter M. Hannah, Levi G. Silvers, Blaž Gasparini, Peter Bogenschutz, Graham L. O’Donnell, Susan C. van den Heever, Chien‐Ming Wu, Keiichi Hashimoto
article en

Abstract

Abstract The Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) phase I provided insights into the tropical radiative‐convective equilibrium state across an unprecedented ensemble of models that includes both those with parameterized and explicit convection. RCEMIP phase II (RCEMIP‐II) introduces mock‐Walker simulations to examine how sea surface temperature (SST) gradients and the forced circulation they theoretically induce interact with the structure of convection and mean climate state. This overview paper presents descriptions of and initial results from 17 numerical models regarding clouds, convective organization, and circulation structure. Results regarding warming the mean SST in the presence of an SST gradient generally mirror those from RCEMIP‐I but a larger range of dynamical circulations, along with additional phenomena, are possible in RCEMIP‐II. Increases in the SST gradient while the mean SST is held constant lead to more convective organization across many models, as measured by a number of organization metrics. Increases in the SST gradient also tend to decrease the frequency of high, thin clouds while increasing the frequency of low clouds, including the possibility of stratocumulus, which were not seen in RCEMIP‐I. RCEMIP‐II also provides an estimate of the influence of a pattern effect, suggesting increased negative climate feedbacks if increases in the SST gradient occur alongside mean warming. However, the SST gradient's inability to fully constrain the circulation structure allows simulations to show varying importance of self‐aggregation and forced clustering over the warm pool, resulting in extreme variety in the circulation structures and important climate variables in the organized state across the model ensemble.

Journal of Advances in Modeling Earth SystemsVol. 18(8)
Florida State University (US), Lawrence Livermore National Laboratory (US), Met Office (GB), Centre National de la Recherche Scientifique (FR), University of Vienna (AT), Planetary Science Institute (US), University of Leeds (GB), Japan Agency for Marine-Earth Science and Technology (JP), University of Wisconsin–Madison (US), Lawrence Berkeley National Laboratory (US), European Centre for Medium-Range Weather Forecasts (GB), National Taiwan University (TW), Université Fédérale de Toulouse Midi-Pyrénées (FR), Hebrew University of Jerusalem (IL), Princeton University (US), Central Institution for Meteorology and Geodynamics (AT), Israel Water Authority (IL), Météo-France (FR), Max Planck Institute for Meteorology (DE), Institut de Recherche pour le Développement (FR), Stony Brook University (US), University of Reading (GB), The University of Tokyo (JP), Colorado State University (US), University of California, Berkeley (US)
RIKEN Center for Computational Science, National Science Foundation, Deutsche Forschungsgemeinschaft, Grand Équipement National De Calcul Intensif, European Research Council, NOAA Research, Lawrence Livermore National Laboratory, NASA Earth Science Technology Office
Climate action
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Climate variability and models
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