Dynamics and Impacts of Mesoscale Gravity Waves

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Gravity waves have been shown to be very important to weather. They can transfer significant amounts of energy and momentum, initiate and organize convection, and generate atmospheric turbulence. Observational studies have repeatedly demonstrated that mesoscale gravity waves with horizontal wavelength of 50-500-km are prevalent in the vicinity of the upper-tropospheric jet streaks. The exact generation mechanism of these waves, however, remains unknown. The ultimate goal of this research is to understand the dynamics and impacts of the gravity waves initiated by the upper-tropospheric jet-front systems and baroclinic instability. A high-resolution mesoscale model with nesting capability will first be used to reproduce the life cycle of the baroclinic waves and to simulate the gravity wave emission from jet streaks. The characteristics, distribution and variability of the gravity waves and their relationship to the parent baroclinic jet-front system in these idealized simulations will be examined in great details. Next, the interaction between balanced and unbalanced dynamics in the initiation of the simulated gravity waves will be investigated through applications of the various balance/imbalance diagnostics including Rossby number, omega equations, nonlinear balance and potential vorticity inversion and also through an extension/implementation of the QG+ theory. QG+ is a systematic asymptotic framework from which the balanced, next-order corrections of quasi-geostrophy in Rossby number are obtained. The final phase of this research will compare the characteristics and dynamics of the gravity waves in the idealized baroclinic-wave simulations with observations and apply the findings from the idealized study to understand the dynamics of the observed gravity waves.Successful completion of this research may lead to better understanding and prediction of the timing and location of local and regional weather events.