Unexpected DE3 Tide in the Southern Summer Mesosphere

Abstract

AbstractSimulation of the January 2017 period using a gravity‐wave resolving global circulation model (HIAMCM) reveals a predominant eastward propagating diurnal tide with zonal wavenumber three (DE3) in the southern summer mesosphere from about 60 to 90 km height at middle to high latitudes. We provide observational evidence based on MERRA‐2 reanalysis and Sounding the Atmosphere using Broadband Emission Radiometry satellite observations for the validity of this result. The attenuation of the DE3 below the mesopause generates a significant eastward Eliassen‐Palm flux divergence that contributes to the residual circulation. We also show that the diurnal tide in the northern summer mesosphere likely consists of mainly eastward propagating components. These findings contradict the common perception of a weak diurnal tide in the summer mesosphere.