On spatiotemporal intermittency of infrasound fields in stable atmospheres

Ducting of infrasound in the stratosphere is sensitive to upward-propagating gravity waves (GWs). GWs are generated by tropospheric sources such as convection or jet/front systems. The effects of GWs on the resolved scales are parameterized in Global Climate Models (GCMs). GW fields can be computed as a combination of a large number of individual wave packets, whose horizontal wavenumber, direction and phase velocity are chosen randomly. This representation allows the phenomenon of intermittency, which is known to produce positive outcomes regarding the long-standing cold-pole bias of GCMs. Intermittency redistributes the GW drag in the stratosphere, in a way which is likely impossible to reach using a spectral parameterization of GWs. In this work, it is shown that the intermittency of GWs can be observed in infrasound data, because of the nonlinearity between the forcing of GW sources and the statistical effects on acoustic waveguides higher up. It is also demonstrated that a minor shift in the phase velocity of GWs at the launching altitude may lead to significant changes in the acoustic waveguides. This sensitivity suggests that infrasound signals, that are recorded worlwide, may provide relevant additional constraints to tune stochastic parameterizations of GWs in GCMs.