Preprints
https://doi.org/10.5194/gmd-2021-381
https://doi.org/10.5194/gmd-2021-381

Submitted as: model evaluation paper 10 Jan 2022

Submitted as: model evaluation paper | 10 Jan 2022

Review status: this preprint is currently under review for the journal GMD.

Improving Madden–Julian Oscillation Simulation in Atmospheric General Circulation Models by Coupling with Snow–Ice–Thermocline One-dimensional Ocean Model

Wan-Ling Tseng1, Huang-Hsiung Hsu1, Yung-Yao Lan1, Chia-Ying Tu1, Pei-Hsuan Kuo2, Ben-Jei Tsuang3, and Hsin-Chien Liang1 Wan-Ling Tseng et al.
  • 1Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan
  • 2Center Weather Bureau, Taipei, Taiwan
  • 3National Chung-Hsing University, Taichung, Taiwan

Abstract. A one-column turbulent kinetic energy–type ocean mixed-layer model Snow–Ice–Thermocline (SIT) when coupled with three atmospheric general circulation models (AGCMs) to yielded superior Madden–Julian Oscillation (MJO) simulation. SIT is designed to have fine layers similar to those observed near the ocean surface and therefore can realistically simulate the diurnal warm layer and cool skin. This refined discretization of the near ocean surface in SIT provides accurate sea surface temperature (SST) simulation, thus facilitating realistic air–sea interaction. Coupling SIT with European Centre Hamburg Model, Version 5 (ECHAM5); Community Atmosphere Model, Version 5 (CAM5); and High Resolution Atmospheric Model (HiRAM) significantly improved MJO simulation in three coupled AGCMs compared with the AGCM driven with prescribed SST. This study suggests two major improvements to the coupling process. First, during the preconditioning phase of MJO over Maritime Continent (MC), the over underestimated surface latent heat bias in AGCMs can be corrected. Second, during the phase of strongest convection over MC, the change of the intraseasonal circulation in the meridional circulation is the dominant factor in the coupled simulations relative to the uncoupled experiments. The study results indicate that a fine vertical resolution near the surface, which better captures temperature variations in the upper few meters of the ocean, considerably improves different models with different configurations and physical parameterization schemes; this could be an essential factor for accurate MJO simulation.

Wan-Ling Tseng et al.

Status: open (until 07 Mar 2022)

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Wan-Ling Tseng et al.

Wan-Ling Tseng et al.

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Short summary
We show that coupling a high-resolution one-column ocean model to three atmospheric general circulation models dramatically improves Madden–Julian oscillation (MJO) simulations. It suggests two major improvements to the coupling process in preconditioning phase and strongest convection phase over Maritime Continent. Our results demonstrate a simple but effective way to significantly improve MJO simulation and potentially also seasonal to subseasonal prediction.