Moisture Mode Processes and MJO Predictability in Coupled NAVGEM/HYCOM Hindcasts

Surface fluxes, radiative heating, and large-scale moisture advection are all important to the development and propagation of water vapor anomalies associated with the convective envelope of the Madden-Julian Oscillation (MJO). These moisture mode processes are crucial to simulating the MJO and the global-scale wind anomalies which result from the diabatic heating within the convective envelope.

MJO structure and behavior as well as moisture mode processes are examined in coupled hindcasts produced using the Navy Global Environmental Model (NAVGEM) and Hybrid Coordinate Ocean Model (HYCOM) during 2014. The simulated moisture tendency is decomposed into the direct contributions from sub-grid moistening and large-scale advection as well as the indirect effect of sub-grid heating on large-scale vertical velocity and as a result vertical moisture advection. Particular attention is paid to the ability of the physics parameterizations to capture the vertical structure of moistening and drying during the transition from convectively suppressed to convectively active regimes. The ability of the model to represent the interaction between convection and moisture is then related to biases in the propagation, large-scale structure, and predictability of the MJO.