How are inversions destroyed

The technique of large-eddy simulations has been used to investigate thermally driven local circulations in deep valleys for a complete diurnal cycle. A soil model simulates the thermal forcing at the ground, which depends on the season, the soil characteristics, the valley orientation, and the atmospheric variables.

The scales of interest are characteristic of an urban site located in a mountainous area, and the research focuses on low wind conditions without the influence of large-scale pressure gradients. This study highlights the influence of the season on the mechanisms responsible for the formation and the destruction of the thermal inversion layer. The spatial distribution of the convective boundary layer (CBL) within the valley is directly influenced by the season because of the variation of the solar warming. In summer, the altitude of the top of the CBL remains approximately constant across the valley, whereas in winter, this altitude varies with its location within the valley.