Analytical Study of the Low Level Jet Formation in a Diurnal Density Oscillation Model

A problem of nocturnal low-level jet (LLJ) formation taking into account the diurnal density variations in the atmospheric boundary layer is studied analytically. The system of nonlinear partial differential equations of hydrodynamics is reduced to a system of linear differential equations for a simplified consideration of the LLJ phenomenon. This model does not use the Boussinesq approximation. An analytical solution of this system of equations shows that LLJ can develop due to the resonance mechanism at a small coefficient of amplification, the value of which determines an amplification of wind speed. The resonance occurs due to the interaction of rotation forces and diurnal density variations. This diurnal density oscillation mechanism amplifies only the horizontal components of wind velocity, which can be supergeostrophic. The diurnal density oscillation mechanism is capable to amplify the horizontal components of the wind speed over a shorter time compared to the inertial oscillation mechanism. The basic properties of the solution extend the inertial oscillation mechanism and have some additional behaviour.