The Representation of Convectively Coupled Kelvin Waves in Global Simulations with Modified Wave Amplitudes

Convectively coupled Kelvin waves (CCKWs) are important drivers of tropical weather and may influence extreme rainfall and tropical cyclone formation. However, directly attributing these impacts to CCKWs remains a challenge. Numerical models also struggle to simulate the convective coupling of CCKWs. To address these gaps in understanding, this study examines a set of global simulations in which CCKW amplitudes are modified at initialization. The Model for Prediction Across Scales –Atmosphere (MPAS-A) is used to simulate a time period in which several CCKW coexisted around the globe, including an unusually strong CCKW located over the Atlantic. Prior to running the simulation, Kelvin-filtered fields are identified in initial conditions and used to either amplify or dampen the initial wave amplitude. This method is effective at robustly changing the strength and structure of simulated CCKWs and can better isolate their convective coupling. These results also show that the simulated rainfall intensity in CCKWs is partially controlled by column saturation fraction and deep convective inhibition. Despite the accurate depiction of most CCKWs during this time period, however, these experiments fail to simulate convective coupling in the strong Atlantic CCKW. This is true even after amplifying this wave at initialization. The cause of this failure is unclear and motivates additional work into the modeling and predictability of CCKW events. Overall, this study demonstrates that modifying CCKW amplitudes can serve as a useful tool for understanding the dynamics of CCKWs. Such a method could also be useful for future attributional work on the impacts of CCKWs.