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Planetary waves in the upper stratosphere and lower mesosphere during 2009 Arctic major stratospheric warming

The AURA-MLS daily mean temperatures and zonal wind from NASA-MERRA reanalysis for latitudes be- tween 60 N and 80 N are used to investigate the plane- tary wave (PW) characteristics in the stratosphere and lower mesosphere during sudden stratospheric warming (SSW) (November 2008 to March 2009). Here, we used a novel method called empirical mode decomposition (EMD) to ex- tract the PWs from the temperature data. The EMD is an interesting approach to decompose signals into locally pe- riodic components, the intrinsic mode functions (IMFs), and will easily identify the embedded structures, even those with small amplitudes. The spectral analysis reveals prevailing planetary wave periods of 6-day, 8-day, 15-day, and 21-23-day in IMFs 1, 2, 3, and 4, respectively. Clear up- ward propagation of these waves (20-30 days) is observed, suggesting that sources for these oscillations are in the tropo- sphere.