Multiscale numerical sensitivity simulations of a mesoscale gravity‐wave event

Abstract The generation and maintenance mechanisms of extratropical cyclone‐coupled, large‐amplitude mesoscale gravity waves (MGWs) remain fundamental challenges in mesoscale meteorology, as the precursor synoptic patterns associated with cyclogenesis events that do and do not produce MGWs are often remarkably similar. Using high‐resolution Advanced Research Weather Research and Forecasting (WRF‐ARW) model simulations, this study examines the mechanisms governing the genesis and maintenance of the Stormscale Operational and Research Meteorology–Fronts Experiment Systems Test (STORM‐FEST) gravity‐wave event on February 14–15, 1992. Wave genesis occurred over southwestern Kansas as a singular wave of depression embedded within a dry slot and subsequently amplified while propagating northeastward, evolving into a wave train that initiated deep convection over eastern Kansas and Missouri. Diagnostics based on the cross‐stream Rossby number and the nonlinear balance equation (NBE) residual reveal pronounced flow imbalance within the upper‐tropospheric jet, accompanied by enhanced vertical wind shear associated with a jetlet. These results indicate that MGW genesis is governed by geostrophic adjustment linked to upper‐level jet imbalance. Wave‐duct diagnostics confirm the presence of a persistent duct across the genesis and propagation regions, with additional contributions from shear instability supporting wave propagation and amplification. Following convective initiation, nonlinear coupling between the MGW and convection plays a critical role in maintaining and amplifying the wave. Sensitivity experiments demonstrate further that latent heating from moist convection is not required for MGW genesis but is essential for downstream wave amplification and maintenance, while upstream terrain enhances the initial upper‐level flow imbalance and thereby modulates wave genesis.