In regions of low latitude, both the upper ocean and the tropospheric atmosphere are observed to have typical motions with a relatively small Rossby number (Ro~0.1). These motions are generally known as synoptic-scale waves in the atmosphere and tropical instability waves in the ocean. The dynamics of these waves have been frequently associated with the instability of the underlying currents in both the ocean and the atmosphere. This preliminary investigation compares the formation and dynamics of these waves in both environments, with a particular focus on the role of background shears. By analyzing the behavior of these waves in different fluid contexts, the study seeks to contribute to the understanding of the dynamics of unstable waves in the geophysical fluids of low-latitude regions.

Based on these findings, the study suggests that atmospheric synoptic-scale waves may be initiated through a significant thermodynamic process, which includes a phase shift between the lower-level atmospheric circulation and coupled deep convection. This process appears to involve a feedback mechanism between convective activity, tropospheric water vapor, and the large-scale mean flow. As a disturbance moves into the warmer and more humid western North Pacific, it may disrupt the balance of moisture between vertical moisture advection and condensation, potentially leading to an increase in moisture within the convective area. This increase in water vapor could then enhance zonal moisture advection by the ambient zonal flow, which might contribute to further moistening of the troposphere to the west. Additionally, the moist deep convection may be influenced by the cyclonic vortex, which is warmer and more humid, possibly increasing the overall humidity in the troposphere. This result proposed an additional mechanism for the development of the synoptic-scale waves, in addition to large-scale instability.
 

synoptic-scale,tropical instability wave,ocean,atmosphere,tropic