Is the nocturnal atmospheric boundary layer chaotic?

The very stable boundary layer, which usually happens during calm nights with reduced cloudiness, is often the stage to the occurrence of global intermittency, a phenomenon characterized by the non-periodic succession of turbulent and non-turbulent periods. In a recent work, we proposed a model that is able to reproduce the occurrence of bursts of turbulence in an unpredictable and deterministic way, when the mechanical turbulence production is weak enough. However, the degree of complexity of the solutions had not been characterized in the previous study. Therefore, the main purpose of the present work is to provide a complete dynamical description of that system when the surface is disconnected from the upper boundary layer. This is achieved through the analysis of the simulated time series of the mean variables that control the stable boundary layer flow. From the evaluation of the correlation dimension of the reconstructed attractor, it is possible to observe that, for certain magnitudes of the mechanical forcing, the system behaves as a strange attractor, with non-integer fractal dimension that increases as the system approaches the connected state. A bifurcation diagram shows that, under certain parameters, the solutions can assume multiple modes, which are also highly sensitive to the initial conditions. Such results indicate that the system may have a chaotic dynamics, which is confirmed by the presence of at least one greater than zero Lyapunov exponent in such cases. The mechanisms that cause such chaotic behavior are examined in detail.