Motivated by the need to interpret the influence of convection schemes on tropical variability, the interaction between gravity-driven waves and moisture in a shallow water model is analysed with an emphasis on physical interpretation.

The phasing between the height, divergence and moisture fields is calculated, and the behaviour of moist gravity waves for finite convective relaxation timescales is explained using the phase differences between the various fields. Physical arguments are provided to show that no propagating solutions exist for high values of the gross moist stability.