Avaliação do desempenho de um modelo de coluna simples na representação de aspectos importantes do escoamento na camada limite noturna

Abstract

The proper description of the atmospheric flow in the stable atmospheric boundary layer is one of the most complex tasks to be performed by numerical models of weather and climate prediction. Most of the parameterizations used in these models are based on the statistical theory of turbulence in their conception. However, this theory is valid only for a flow in which turbulence is homogeneous, isotropic and stationary, a conditions that are not commonly found overnight. Basically, the nighttime flow can be classified in two major regimes: very stable, where turbulence is almost entirely suppressed; and weakly stable regime, with intense turbulent mixing. The transition between these regimes is known as atmospheric coupling, and it can happens a lot of times along the same night. In this work, we implemented a single column model with turbulence closure 1.5, in three different configurations and three different turbulence formulations. In general, the model results show that, all the configurations are able to reproduce the average characteristics of the flow in the weakly stable conditions. However, the representation of the transition from the weakly stable regime to the very stable regime is not adequately represented, even when a parameterization that unrealistically reduce the intensity of turbulence is used. This result clearly shows the inefficiency of the atmospheric numerical models in reproduce the atmospheric coupling.