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

Water vapor anomalies associated with the convective envelope of the Madden-Julian Oscillation (MJO) develop and propagate in response to the interactions between surface fluxes, diabatic heating and moistening within convective clouds, and large-scale moisture advection. These moisture mode processes are crucial to simulating the MJO and the global-scale teleconnections which result from the associated diabatic heating.

Simulations of the MJO events during the spring and summer of 2015 are produced using the Navy Global Environmental Model (NAVGEM) coupled to the Hybrid Coordinate Ocean Model (HYCOM). To examine the moisture mode processes contributing to the growth and propagation of MJO convective envelopes, the simulated gross moist stability and budget of vertically integrated moist static energy are compared to the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis. To examine the vertical structure of these moisture mode processes, the simulated time tendency of water vapor 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. Lastly, we attempt to relate the large-scale behavior of the simulated MJO events to the moisture mode processes in these simulations.