Infrasound from tropospheric sources: Impact on mesopause temperature?

Abstract

Temperature fluctuations with a 3-6 day modulation are frequently observed in the mesopause height region (around 80-90 kilometer) especially from OH*-airglow measurements. The northern hemisphere wintertime appearance of these fluctuations is often explained by tropospheric planetary wave activity (4- and 5-day-wave) propagating up to the mesopause, but the physical mechanism leading to these variations in summertime is still under discussion. Planetary waves are strongly influenced by stratospheric winds. Therefore, the westward winds in the northern hemisphere summertime normally prevent the propagation through the stratosphere. One effect that might be contributing to such summertime temperature fluctuations in the mesopause altitude region could be acoustic heating. Infrasound, which is known to be generated by low pressure areas or thunderstorm cells, propagates more or less unhindered into the upper atmosphere and deposits heat in this region. It is speculated that the oftentimes about weekly variation of low pressure areas due to planetary wave activity in the troposphere can therefore be a potential source mechanism for mesopause temperature fluctuations through infrasound as a transporting mechanism.