Wave mean flow interactions in the thermosphere induced by a major tsunami

We investigate how the dynamics of the thermosphere is influenced by the dissipation of a tsunami‐driven gravity wave disturbance. Unlike typical lower atmospheric sources, the tsunami generates a spectrum entirely of fast gravity waves that can efficiently propagate to the upper atmosphere. This disturbance transports momentum into the thermosphere while dissipation due to molecular viscosity and thermal conduction drives a downward sensible heat flux within the thermosphere. The divergence of the momentum flux forces a change in velocity of 150–200 m/s between 200 and 300 km altitude. A tsunami propagating for ∼10 h before making landfall will produce a secular change in the wind and temperature field that extends as much as 8000 km along the direction of wave propagation. The induced winds should be observable through a variety of methods. The thermal effects driven by the divergence of the sensible heat flux are more modest and would be difficult to observe. These simulations show that large tsunami events could have a pronounced dynamical effect in the thermosphere until conditions relax to their undisturbed state.