Enhanced MJO Activity at High SST in a Super-Parameterized GCM

The Madden-Julian Oscillation (MJO) is the dominant mode of tropical intra-seasonal variability, characterized by an eastward propagating envelope of convective anomalies with a 30-70 day timescale. Here we report changes in MJO activity across coupled simulations with a super-parameterized version of the NCAR Community Earth System Model. We find that intra-seasonal OLR variance nearly doubles between a pre-industrial control run and a run equilibrated with 4xCO2. Intra-seasonal precipitation increases at a rate of roughly 15% per degree C of warming, and MJO events become more frequent. Moist static energy budgets of composite MJO events are calculated for each scenario, and changes in budget terms are used to diagnose the physical processes responsible for changes in the MJO with warming. This work has implications for organized tropical variability in past warm climates as well as future global warming scenarios.