Grant: Discovery Grants Program - Individual

The spatial resolution of large scale numerical models for climate simulations and weather prediction is too coarse to represent the small-scale nonhydrostatic processes that are responsible for the major part of the vertical transport of momentum and heat in the atmosphere. My research employs various numerical models to study small-scale disturbances in the atmosphere. The primary objectives are to improve our understanding of the complex interactions between small-scale internal wave processes and the large-scale circulation, and to facilitate improved representations of these processes in large-scale atmosphere-ocean models. Canada has a critical need for work in this area since the drag exerted by breaking small-scale gravity waves is, along with radiative processes such as ultraviolet absorption in the ozone layer, one of the dominant factors in determining the circulation of the middle atmosphere (roughly 10 to 90 km above mean sea level). Small-scale internal gravity waves also play a prominent role in mesoscale processes, e.g. the development of severe windstorms that form in the lee of mountain ranges, the development of turbulent layers encountered by aircraft, and in the organization of severe thunderstorms. My research will therefore also have an impact in mesoscale forecasting. Our understanding of small-scale processes is far from complete and, in particular, the mechanisms through which gravity waves interact with the large-scale flow are still being hotly debated. My most recent work is making important contributions to this debate -- it demonstrates that one representation of wave-wave interactions (Doppler spreading) is based on a seriously flawed theoretical model that violates conservation of mass and thermodynamic energy. This flawed representation of nonorographic gravity wave drag is currently employed in Canadian numerical weather prediction and climate models (as well as many other models used around the world), and needs to be replaced with an alternative based on sound physics.