Preprints
https://doi.org/10.5194/gmd-2021-346
https://doi.org/10.5194/gmd-2021-346

Submitted as: development and technical paper 22 Nov 2021

Submitted as: development and technical paper | 22 Nov 2021

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

Embedding a One-column Ocean Model (SIT 1.06) in the Community Atmosphere Model 5.3 (CAM5.3; CAM5–SIT v1.0) to Improve Madden–Julian Oscillation Simulation in Boreal Winter

Yung-Yao Lan, Huang-Hsiung Hsu, Wan-Ling Tseng, and Li-Chiang Jiang Yung-Yao Lan et al.
  • Research Center for Environmental Changes, Academia Sinica, Taipei 11529, Taiwan

Abstract. The effect of the air–sea interaction on the Madden–Julian Oscillation (MJO) was investigated using the one-column ocean model Snow–Ice–Thermocline (SIT 1.06) embedded in the Community Atmosphere Model 5.3 (CAM5.3; hereafter CAM5–SIT v1.0). The SIT model with 41 vertical layers was developed to simulate sea surface temperature (SST) and upper-ocean temperature variations with a high vertical resolution that resolves the cool skin and diurnal warm layer and the upper oceanic mixed layer. A series of 30-year sensitivity experiments were conducted in which various model configurations (e.g., coupled versus uncoupled, vertical resolution and depth of the SIT model, coupling domains, and absence of the diurnal cycle) were considered to evaluate the effect of air–sea coupling on MJO simulation. Most of the CAM5–SIT experiments exhibited higher fidelity than the CAM5-alone experiment in characterizing the basic features of the MJO such as spatiotemporal variability and the eastward propagation in boreal winter. The overall MJO simulation performance of CAM5–SIT benefited from (1) better resolving the fine structure of upper-ocean temperature and therefore the air–sea interaction that resulted in more realistic intraseasonal variability in both SST and atmospheric circulation and (2) the adequate thickness and vertical resolution of the oceanic mixed layer. The sensitivity experiments demonstrated the necessity of coupling the tropical eastern Pacific in addition to the tropical Indian Ocean and the tropical western Pacific. Enhanced MJO could be obtained without considering the diurnal cycle in coupling.

Yung-Yao Lan et al.

Status: open (until 17 Jan 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Yung-Yao Lan et al.

Yung-Yao Lan et al.

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Short summary
This study has shown that coupling a high-resolution 1-D ocean model (SIT 1.06) with the Community Atmosphere Model 5.3 (CAM5.3) significantly improves the simulation of the Madden-Julian Oscillation (MJO) over the standalone CAM5.3. Systematic sensitivity experiments resulted in more realistic simulations of the MJO because they had better upper ocean resolution, adequate upper ocean thickness, coupling regions including the eastern Pacific and southern tropics, and a diurnal cycle.