Assessment of the Madden‐Julian Oscillation in CMIP6 Models Based on Moisture Mode Theory

• Published in: Geophysical research letters Vol. 51; no. 8
• Main Authors: Lin, Qiao‐Jun, Mayta, Víctor C., Adames Corraliza, Ángel F.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.04.2024; Wiley
• Subjects: Climate; Climate models; CMIP6; Criteria; Intercomparison; Madden-Julian oscillation; Moist static energy; Moisture; moisture mode; Oceans; Simulation; Temperature gradients; Theories; Thermodynamics; Winds; Zonal winds; Indian Ocean
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL106693

The moist processes of the Madden‐Julian Oscillation (MJO) in the Coupled Model Intercomparison Project Phase 6 models are assessed using moisture mode theory‐based diagnostics over the Indian Ocean (10°S–10°N, 75°E–100°E). Results show that no model can capture all the moisture mode properties relative to the reanalysis. Most models satisfy weak temperature gradient balance but have unrealistically fast MJO propagation and a lower moisture‐precipitation correlation. Models that satisfy the most moisture mode criteria reliably simulate a stronger MJO. The background moist static energy (MSE) and low‐level zonal winds are more realistic in the models that satisfy the most criteria. The MSE budget associated with the MJO is also well‐represented in the good models. Capturing the MJO's moisture mode properties over the Indian Ocean is associated with a more realistic representation of the MJO and thus can be employed to diagnose MJO performance. Plain Language Summary The Madden‐Julian Oscillation (MJO) is arguably the most important tropical phenomenon that drives weather at the intraseasonal time scale. Although the MJO has been analyzed for the past decades, its simulation in climate models can still be improved. Previous studies have emphasized that the MJO evolution is tightly modulated by moisture fluctuations and posited the moisture mode theory to explain its behavior. Here, we show that no climate model can realistically reproduce the moist thermodynamics of the MJO, particularly its sensitivity to humidity anomalies. The models that most reproduce the MJO's moist thermodynamics simulate a stronger MJO, and are generally more realistic. Key Points Madden‐Julian Oscillation (MJO) simulation skill in 25 Coupled Model Intercomparison Project Phase 6 models is assessed using moisture mode theory No model can realistically reproduce all the moisture mode properties of the MJO over the Indian Ocean Models that best capture the MJO's moisture mode features exhibit more realistic mean states and MJO structure and propagation features