Maintenance of Convectively Coupled Kelvin Waves: Relative Importance of Internal Thermodynamic Feedback and External Momentum Forcing

Previous studies suggest that convectively coupled Kelvin waves (KWs) are likely maintained by two distinct processes: (1) the internal thermodynamic feedback between KW diabatic heating and temperature and (2) the external momentum forcing from the midlatitude Rossby waves exerting on KW zonal wind. This study quantifies the relative importance of the two processes to KW maintenance by comparing the growth rate of eddy available potential energy (EAPE) and eddy kinetic energy (EKE) within KWs using satellite and reanalysis data. Results show that internal thermodynamic feedback is the dominant mechanism that maintains KWs in all regions and seasons. Among all regions, the external forcing is the least important over the Indian Ocean, possibly associated with the highest sea surface temperature and weakest westerly in the upper troposphere, which enhances diabatic heating and inhibits midlatitude waves approaching the tropics, respectively. This study highlights investigating the internal thermodynamic feedback within KWs in observations and numerical simulations.