The 2-day wave during the boreal summer of 1994

Abstract

The 2-day wave during the boreal summer of 1994 was observed using stratospheric analyses from the British Met Office and at mesospheric heights using medium-frequency (MF) radars and the microwave limb sounder (MLS) and high-resolution Doppler imager (HRDI) satellite instruments. Most of the evidence from our study points to a high latitude source for the boreal 2-day wave event we observed. We found little evidence for a connection between the 2-day wave event in the mesosphere and activity at lower altitudes. Instead we contend that the 2-day wave observed at upper mesospheric heights was excited in-situ. This event was predominantly zonal wave number 2, was highly localized in time, and the disturbance propagated equatorially from high northern latitudes. At stratopause and lower mesospheric heights the largest 2-day wave amplitudes were seen at high Southern Hemisphere latitudes (i.e., in the winter hemisphere). However, the austral winter 2-day wave was trapped and did not penetrate to upper mesospheric heights.