The moisture mode framework of the madden-julian oscillation

Abstract

Moist thermodynamics play a central role in regulating tropical deep convection. In particular, tropospheric humidity has been found to be highly spatially and temporally correlated with precipitation, particularly at the intraseasonal (20-100 day) timescale and the planetary scale (zonal wavenumbers 1-5). This and other evidence support the hypothesis that tropospheric moisture variations are central to the dynamics of the Madden-Julian Oscillation (MJO), the most prominent mode of tropical intraseasonal variability. Numerous studies have developed this hypothesis into a view of the MJO in which it is considered to be a moisture mode. The intraseasonal moist static energy budget in combination with the weak temperature gradient approximation has been used to understand the processes that maintain and propagate the intraseasonal precipitation anomalies. These analyses indicate that horizontal and vertical moisture advection play essential roles in the propagation of the MJO while longwave radiative heating is a key process in the maintenance of the MJO.