Changes to the Madden-Julian Oscillation with Surface Temperature Warming in Aquaplanet Simulations
Year: 2026
Type: preprint
Abstract: Interactions between waves and the mean-state in the tropics are of fundamental importance for reliable future projection of tropical waves and their impacts under anthropogenic climate change. The Madden-Julian Oscillation (MJO) is the dominant source of weather variability over many parts of the globe on intraseasonal timescales. In this study, we investigate the influence of mean-state changes on the MJO in three aqua-planet experiments made with the Community Atmosphere Model version 6 (CAM6) by prescribing sea surface temperature profiles to capture three different climate states: a current climate-like state, a colder (-4K) state, and a warmer (+4K) state. We find that the MJO strengthens with surface warming, showing higher spectral power over the MJO band (20-100 day period, zonal wavenumbers 1-3) in both circulation and convection fields. Furthermore, MJO-associated precipitation variability increases more strongly than mean-state precipitation with warming, while the east-west ratio increases by a factor of 3x from -4K to +4K. Using a moisture budget approach, two key mechanisms were found to result in MJO strengthening; first, a reduction in the Gross Moist Stability associated with increases in the mean low-level vertical moisture gradient, and second, a reduced damping associated with meridional moisture advection resulting from an increase in the mean low-level meridional moisture gradient. The reduction in GMS is slightly offset, however, by a reduction in the cloud-radiative feedback parameter with warming. This occurs because the cloud top temperature is nearly invariant with warming despite a sharp increase in precipitation.
DOI: 10.31223/x5zr5k
Authors: Spencer Ressel, Daehyun Kim, Peter Blossey
Institutions: Seoul National University, University of Washington
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDG: Climate action
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, National Research Foundation, Seoul National University, Korea Meteorological Administration, National Research Foundation of Korea, Ministry of Science and ICT, South Korea, National Oceanic and Atmospheric Administration
OpenAlex ID: W7214126789