Anomalous two-day wave behavior during the 2006 austral summer

An anomalous behavior of the two-day wave is observed during the 2006 Austral Summer in the mesospheric temperature and line-of-sight wind, retrieved from the Microwave Limb Sounder (MLS) aboard NASA's Earth Observing System (EOS) Aura mission. During January 2006, the wave appears to exist in an unusually strong summer easterly jet, and its spectral signature spreads over a broader range of zonal wavenumber and frequency. In addition to the typical wavenumber 3 component, a wavenumber 2 disturbance with a near 2-day period is also evident, traveling westward at similar phase speed. The wavenumber 3 component exhibits the previously observed dual characteristics of both a normal and an instability mode, while the wavenumber 2 feature appears to be an instability mode, in agreement with recent theoretical calculations. Citation: Limpasuvan, V., and D. L. Wu (2009), Anomalous two-day wave behavior during the 2006 austral summer, Geophys. Res. Lett., 36, L04807, doi:10.1029/2008GL036387.