New publication on the Impact of Gravity Waves on Transport and Mixing

In the middle and upper atmosphere, small-scale waves called gravity waves (GW) caused by events like thunderstorms or jet streams strongly influence winds, temperature, and circulation. This paper explores how non-orographic GWs, especially those traveling at an angle to the vertical (obliquely), alter transport and mixing of air. Unlike vertically propagating GWs, oblique GWs can deposit their momentum and energy across a wider region and altitudes. Using a state-of-the-art GW parameterization and atmospheric model alongside a novel theoretical framework, we simulate these oblique GWs and their interaction with turbulence—the chaotic motions of the atmosphere. Results show that neglecting these processes may lead models to underestimate transport, mixing, and circulation, particularly in the tropical stratosphere and mesosphere where GW activity is strongest. Oblique propagation is found to cool and lower the summer mesopause (the coldest region of the atmosphere), while reducing vertical shear and intensifying turbulence. In contrast, when GWs are coupled to turbulence, the mesopause warms and rises, but shear is still reduced and turbulence intensified. This coupling also enhances mixing, influencing heat and chemical redistribution. Overall, the findings point to the need for GW parameterizations that account for oblique propagation and turbulence coupling.