Sensitivity of Tropical Wave Structure to Resolution and Convection Treatment in a Global Non-Hydrostatic Model

Tropical waves are key drivers of weather and climate variability, yet their accurate simulation remains challenging due to the complexities of moist convection. This study investigates the impact of model resolution and convection treatment on tropical wave representation in a global non-hydrostatic model. Six simulations, with resolutions of 3.75 km, 15 km, and 120 km and convection treatments ranging from fully explicit to fully parameterized, are analyzed for their ability to capture wave-induced rainfall and three-dimensional wave structures. Results indicate that explicit convection outperforms parameterized convection in replicating rainfall anomalies, dynamic and thermodynamic wave structures, and rainfall-wind coupling. The 3.75-km explicit convection simulation performed best overall, indicating that explicit convection requires high resolution for optimal performance. A 15-km simulation using an alternative cumulus scheme produced wave signals nearly as accurate as the 3.75-km run, but with a significant rainfall bias, suggesting that the right results can sometimes be obtained for the wrong reasons. The study concludes that high resolution and explicit convection are essential for accurate tropical wave representation, with profound implications for weather forecasting and climate projections.