Kelvin-Helmholtz Instability: A Source of High-Frequency Gravity Waves in the Middle and Upper Atmosphere

A high-resolution compressible atmosphere model is utilized to investigate the emission of gravity waves (GWs) from a shear region exhibiting Kelvin-Helmholtz Instability (KHI). The simulations conducted demonstrate that wind shears can induce vigorous KHI dynamics, resulting in the emission of high-frequency and small-scale GWs. The density-weighted amplitudes of the KHI-radiated GWs give rise to a distinctive "fishbone" structure in z-t plots, indicating the presence of upward- and downward-propagating gravity waves originating from the KHI layer. Our findings indicate that the instability present in wind shears can serve as a significant source of GWs that propagate into the mesosphere, thermosphere, and ionosphere. Some GWs reaching the ionosphere possess the potential to trigger plasma instability, thereby causing irregularities and disturbances in the ionospheric region.