Two-way interactions between MJO and high-frequency waves over the Maritime Continent in MJOTF/GASS models

Abstract

The two-way interaction between the Madden–Julian Oscillation (MJO) and high-frequency waves (HFW) over the Maritime Continent is investigated through the diagnosis of 12 MJOTF/GASS models. The models are divided into good and poor groups based on their performance in capturing the eastward propagation of MJO. Regarding to the modulation of MJO to HFW, it is noted that there is a significant increase (decrease) of HFW intensity over and to the west (east) of MJO convection in the good model group, similar to the observed. However, enhanced HFW appears only over the MJO convective center in the poor model group. The difference in MJO modulation lies in the wind shear and specific humidity patterns associated with the MJO. The upscale feedback of HFW to MJO is investigated through the diagnosis of both anomalous condensational heating ($\tilde{Q}_{2}$) and eddy momentum transport. It is found that shallow convection associated with $\tilde{Q}_{2}$ develops in front of MJO deep convection in the good model group, as in observations. The primary contributor to $\tilde{Q}_{2}$ among the nonlinear rectification of HFW is the meridional advection of specific humidity anomaly ($\widetilde{{ - Lv^{\prime}\frac{{\partial q^{\prime}}}{\partial y}}}$). The zonally asymmetric nonlinear advection is not seen in the poor model group. The contribution from the nonlinear rectification of HFW ($\widetilde{termA}$) to MJO zonal wind tendency is maximum at 850-hPa and similar in the good and poor model groups because of the significant increased HFW over the MJO convection region in both groups. No eastward propagation of the MJO zonal wind in the poor model group attributes to the MJO flows itself.