On the genesis of multi-peak vertical structure of quasi-two-day waves in the mesosphere–lower thermosphere

Abstract The study presents multi-peak vertical structure of westward propagating quasi-two-day wave with wave-number 3 (W3) and its formation mechanisms in the mesosphere–lower thermosphere, using two decades of multi-satellite measurements, for the first time. W3 in austral summer shows a multi peak vertical structure, with two prominent peaks having amplitudes of 11.24 ± 2.2 K and 8.66 ± 1.1 K at 108 km (M1) and 84 km (M2), respectively. Genesis of this multi-peak structure, which is not explored in details hitherto, is investigated. While weak eastward/westward winds favour vertical growth of W3 in the regions of M1 and M2, strong eastward winds weaken W3 in the region between M1 and M2. These changes in zonal winds are modulated by the altitude variations in meridional temperature gradient and gravity wave filtering. Thus, vertically alternating changes in wind and meridional temperature gradient are the potential drivers for the multi-peak vertical structure of W3, which will be of importance for atmosphere–ionosphere coupling processes. Graphical Abstract