Kim et al. (2025) Improved Maritime Continent MJO Simulation in the KMA GloSea6 through Enhanced Thermodynamic Processes

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Climate
• Year: 2025
• Date: 2025-11-24
• Authors: Gayoung Kim, Sun‐Hee Shin, Kangjin Lee
• DOI: 10.1175/jcli-d-25-0201.1

Research Groups

Korea Meteorological Administration (KMA)

Short Summary

This study evaluates the Madden–Julian oscillation (MJO) simulation and prediction skill in the Korea Meteorological Administration’s Global Seasonal Forecast System, version 6 (GloSea6), comparing it with its predecessor, GloSea5. GloSea6 demonstrates enhanced MJO propagation across the Maritime Continent (MC) due to improved thermodynamic processes and background state, leading to better prediction skill in that region.

Objective

• To evaluate and compare the simulation and prediction skill of the Madden–Julian oscillation (MJO) in GloSea6 against GloSea5, focusing on key physical processes over the Maritime Continent (MC).

Study Configuration

• Spatial Scale: Regional (Maritime Continent, Indian Ocean) to Global
• Temporal Scale: Subseasonal to seasonal

Methodology and Data

• Models used: GloSea6, GloSea5
• Data sources: GloSea5 model output (for comparison), observed MJO characteristics (for validation)

Main Results

• Both GloSea6 and GloSea5 exhibit systematic biases, including weaker MJO amplitudes and a tendency for the MJO to stall over the Maritime Continent (MC).
• GloSea6 shows enhanced MJO propagation across the MC compared to GloSea5.
• The eastward-to-westward spectral power ratio improved from 1.52 in GloSea5 to 1.93 in GloSea6, moving closer to the observed value of 2.79.
• Improvements are region-dependent, being more pronounced over the MC but limited over the Indian Ocean (IO).
• MC improvements are linked to better simulation of lower-level moisture convergence, equivalent potential temperature, and available potential energy.
• These MC improvements are supported by reduced sea surface temperature (SST) biases and a steeper meridional moisture gradient in GloSea6.
• Background state changes in GloSea6 strengthen moistening processes that precondition convection and sustain eastward MJO propagation over the MC.
• Improvements in spatial pattern similarity did not consistently translate into propagation skill gains, particularly over the IO.

Contributions

• Demonstrates clear advancements of GloSea6 over GloSea5 in representing MJO propagation, particularly over the Maritime Continent.
• Quantifies the improvement in the balance between eastward and westward spectral power in GloSea6, reflecting a more realistic MJO signal.
• Provides process-based diagnostics linking improved MJO simulation in GloSea6 to better representation of thermodynamic processes (e.g., lower-level moisture convergence, equivalent potential temperature) and background state changes (e.g., reduced SST biases).
• Highlights the region and process-dependent nature of model advancements, offering valuable guidance for targeted improvements in subseasonal to seasonal (S2S) prediction systems.

Funding

Not specified in the provided text.

Citation

@article{Kim2025Improved,
  author = {Kim, Gayoung and Shin, Sun‐Hee and Lee, Kangjin},
  title = {Improved Maritime Continent MJO Simulation in the KMA GloSea6 through Enhanced Thermodynamic Processes},
  journal = {Journal of Climate},
  year = {2025},
  doi = {10.1175/jcli-d-25-0201.1},
  url = {https://doi.org/10.1175/jcli-d-25-0201.1}
}