EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-3744 Biased MJO causing a lack of QBO–MJO connection in multi-model simulations with a nudged QBO Huang Kai 1 Park Chang-Hyun https://orcid.org/0000-0002-1950-3279 2 Back Seung-Yoon 2 3 García-Franco Jorge L. 4 Kim Hera https://orcid.org/0000-0002-8036-9443 2 5 Lin Pu https://orcid.org/0000-0003-2577-6094 6 7 Osprey Scott https://orcid.org/0000-0002-8751-1211 8 9 Richter Jadwiga 1 Chen Chih-Chieh 1 Son Seok-Woo https://orcid.org/0000-0003-2982-9501 2 Yoden Shigeo https://orcid.org/0000-0003-1663-4588 10 Lim Yuna https://orcid.org/0000-0003-2187-0649 11 12 Butchart Neal 13 Anstey James 14 Kawatani Yoshio https://orcid.org/0000-0003-3260-8830 15 Andrews Martin B. 13 Lott Francois https://orcid.org/0000-0003-2126-5510 16 Lu Yixiong https://orcid.org/0000-0001-9823-9367 17 Chai Zhaoyang https://orcid.org/0000-0002-8064-9066 18 Rosenbloom Nan https://orcid.org/0000-0001-7389-3346 1 Tang Qi https://orcid.org/0000-0003-2959-0203 19 Xie Jinbo https://orcid.org/0000-0002-3003-9155 19 20 Serva Federico https://orcid.org/0000-0002-7118-0817 21 Hong Dong-Chan 2 Watanabe Shingo 22 23 Jaison Aleena M. 24 Naoe Hiroaki https://orcid.org/0000-0002-6261-0854 25 Yoshida Kohei https://orcid.org/0000-0002-2422-5584 25 National Science Foundation National Center for Atmospheric Research, Boulder CO, 80305, USA School of Earth and Environmental Sciences, Seoul National University, Seoul, 08826, Korea The Department of the Geophysical Sciences, The University of Chicago, Chicago IL, 60637, USA National School of Earth Sciences (Escuela Nacional de Ciencias de la Tierra), UNAM, Mexico City, 04510, Mexico Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA Department of Earth and Environment Science, Boston College, Chestnut Hill, MA, USA Geophysical Fluid Dynamics Laboratory(NOAA), Princeton, NJ, USA Department of Physics, University of Oxford, Oxford, UK National Centre for Atmospheric Science, Oxford, UK Professor Emeritus of Kyoto University, Kyoto, 606-8501, Japan Earth System Science Interdisciplinary Center, University of Maryland College Park, College Park, MD, 20740, USA Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA Met Office Hadley Centre (MOHC), Exeter, UK Canadian Centre for Climate Modelling and Analysis, Environment and Climate Change Canada, Victoria, British Columbia, Canada Faculty of Environmental Earth Science, Hokkaido University, Sapporo, Japan Laboratoire de Météorologie Dynamique (LMD), Paris, France State Key Laboratory of Severe Weather Meteorological Science and Technology, Earth System Modeling and Prediction Centre, China Meteorological Administration, Beijing, China Earth System Numerical Simulation Science Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China Lawrence Livermore National Laboratory, Livermore, CA, USA High Meadows Environmental Institute (HMEI), Princeton University, Princeton, NJ, USA Institute of Marine Sciences, National Research Council (CNR-ISMAR), Rome, Italy Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Japan Advanced Institute for Marine Ecosystem Change (WPI-AIMEC, Tohoku University, Sendai, Japan) Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, United Kingdom Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan 10 07 2026 2026 1 32 Copyright: © 2026 Kai Huang et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3744/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3744/egusphere-2026-3744.pdf

Observations suggest that the stratospheric Quasi-biennial Oscillation (QBO) modulates the Madden-Julian Oscillation (MJO) in the tropical troposphere, where the MJO is stronger with a smoother eastward propagation in the boreal winter seasons with a QBO easterly (QBOE) than that with a QBO westerly (QBOW) phase. Such connection is not captured by current climate models through their internally generated QBO and MJO. The QBO initiative (QBOi) phase 2 project included climate models from global modeling centers and conducted simulations with the tropical zonal-mean zonal wind in the model stratosphere nudged towards the observations. This paper investigates the potential connection between the nudged QBO and the internally generated MJO in 12 participating climate models. Results show that the stratospheric QBO and its associated impacts on the upper troposphere and lower stratosphere stability around the equator are realistically represented in all models through the nudging although a smaller amplitude is found for the temperature responses. However, there is no significant connection between the QBO and MJO in any of the participating models. Further diagnostics suggest this likely result from the biases in the internally generated MJO by the models where the simulated MJO convective variation is constantly underestimated so that the intense MJO OLR and precipitation anomalies are inadequately induced. However, the QBOi phase 2 models show no systematic bias in the MJO cloud-radiative feedback strength, with individual models spanning the full range from underestimation to overestimation of the observed values. These findings emphasize the importance of accurate representation of the MJO convective system in capturing the QBO-MJO connection by climate models. This paper also underscores the urgency of new theoretical understandings for the observed QBO-MJO connection.

 National Research Foundation of Korea RS-2025-25438815 RS-2025-02363044