Recent experiments by the authors using several different climate models suggest that the sharpening of mean state meridional moisture gradients throughout the Warm Pool is a principal mechanism through which ocean coupled feedbacks affect MJO simulation in coupled general circulation models (CGCMs). This finding was revealed in model experiments in which monthly mean SSTs from an individual CGCM were prescribed to atmosphere-only GCM (AGCM) simulations with the same model. Despite the insights gleaned from these experiments, an understanding of how sub-monthly SST variability contributes to changes in the mean state moisture distribution and MJO propagation remains elusive.
In this presentation, we outline a hierarchy of proposed AGCM experiments to bridge the experimental and conceptual gaps that fall between fully coupled and prescribed SST (i.e., AMIP-type) experiments. The experiments are designed to answer the following question: “How do the phasing, pattern, and persistence of SST anomalies (SSTAs) impact tropical mean state moisture patterns, and thus MJO propagation?" The model experiments designed to answer this question utilize a variety of SSTA filtering and randomization strategies. Preliminary results from a handful of models are presented. We conclude with an invitation to the broader modeling community to contribute results of the proposed experiments for a model intercomparison study.