Future Directions for Research on Meter - and Submeter - Scale Atmospheric Turbulence

It is impossible to measure, simulate, predict, and understand the earth’s atmosphere without taking into account its turbulent nature. When simulating the macrostructure of atmospheric flows, because of practical limitations, there is no way to simultaneously and explicitly simulate small-scale turbulence or even microphysical processes. Yet, the small scales can significantly impact the large scales. Therefore, the small-scale phenomena have to be accounted for, but in many cases that can be done only in a parameterized fashion. For instance, the grids of conventional numerical weather forecasting models have horizontal mesh widths of a few tens of kilometers, which, in this case, makes it impossible to deterministically simulate even structures as large as thunderstorms. That is, conventional numerical weather forecasting relies heavily on parameterizations of subgrid processes such as formation of clouds and precipitation, turbulent exchange between surface and atmosphere, mixing within the atmospheric boundary layer (ABL), and entrainment of less turbulent, free-tropospheric air into the ABL. The situation is even more demanding for climate modeling. Those parameterizations are typically constructed on the basis of idealized considerations, often using similarity arguments. Therefore, an important task of theoretical and applied meteorology has been, and continues to be, to develop and empirically verify those parameterizations in the context of their applications, and to determine dimensionless coefficients and functions that cannot be obtained through dimensional analysis. The suitability of a numerical model for simulating a turbulent atmospheric flow is limited by the accuracy of its subgrid-scale parameterizations. A classic example for turbulence parameterization is the Monin–Obukhov similarity theory, which provides turbulent flux parameterizations in the atmospheric surface layer (ASL), involving meter-scale features. Future Directions for Research on Meterand Submeter-Scale Atmospheric Turbulence