Effect of rotational moisture advection on the amplitude and phase speed of the MJO in aquaplanet SP-CAM3

We present follow-up results to a recent suite of simulations that demonstrated horizontal moisture advection through tropical vorticity anomalies is critical to the propagation and maintenance of the superparameterized MJO as a moisture mode. In order to test the robustness of this result, the SuperParameterized CAM (SPCAM) v.3.0 with a novel horizontal moisture advection modulator is run on a perpetually equinox aquaplanet, known to produce a realistically responsive MJO-like signal. The results from a suite of simulations broadly confirm the key findings in real-geography mode - that not only the speed of the MJO, but also its amplitude, has a positive correlation with rotational horizontal moisture advection. Interestingly, the correlation between upper-level equatorial superrotation and MJO amplitude is oppositely signed in the aquplanet vs. realgeography configuration of the model. In the aquaplanet, as horizontal moisture advection is artificially amplified, the MJO amplitude increases in tandem with equatorial supperotation, as has also been seen in idealized aquaplanet global warming experiments (Arnold et al. 2013). However this is opposite to the MJO amplitude – superrotation correlation in real-geography mode.