On the mechanism of low-level jets formation

Low-level jet (LLJ) is characterized by the maximum wind in the lower part of an atmospheric boundary layers. Given their relatively high speed and low turbulence intensity, LLJs provide an opportunity for the stable atmosphere to serve as a high energy density resource compared to the unstable atmosphere. In this study, we use direct numerical simulation of the atmospheric boundary layer based on the observational data from the meteorological tower to understand the mechanism by which LLJs are formed. Maintenance of turbulence at high Richardson numbers can be associated to submeso motions of unusually well-defined waves that are formed above the atmospheric boundary layer. The disturbances of such motions can induce surface pressure perturbations and contribute to the finite-amplitude wind fluctuations close to the surface. We examine whether the inflection-point instability can induce such wave-like motions above the atmospheric boundary layer and whether such a wave-turbulence mechanism can contribute to the intermittent bursts and consequently formation and evolution of LLJs.