1 3 DOI 10.1007/s00382-016-3046-2 Clim Dyn Global normal mode planetary wave activity: a study using TIMED/SABER observations from the stratosphere to the mesosphere-lower thermosphere Sherine Rachel John 1 · Karanam Kishore Kumar 1 Received: 16 September 2013 / Accepted: 14 February 2016 © Springer-Verlag Berlin Heidelberg 2016 to the equator. A detailed discussion on the height-latitude structure, interannual variability and inter-hemispheric propagation of quasi 16-, 10- and 5-day waves are dis- cussed. The significance of the present study lies in estab- lishing the 5-year climatology of normal mode planetary waves from the stratosphere to the MLT region including their spatial–temporal evolution, which are very important from the middle atmospheric dynamics standpoint. Keywords Middle atmospheric dynamics · Planetary waves · Interhemispheric propogation · TIMED/SABER 1 Introduction Planetary scale waves dominate the middle atmospheric dynamics by depositing energy and momentum which they carry from the lower atmosphere. These waves also play a key role in filtering of gravity waves. By now, it is well established that the wave driven dynamics is one of the most important processes in the middle atmosphere apart from the dynamics driven by solar radiation. The unforced solutions to the linearized equations of an isothermal and dissipationless atmosphere are referred to as “free oscil- lations” or “normal modes (Forbes et al. 1999). These normal modes can take the form of gravitational modes, Rossby modes, mixed Rossby-Gravity or Kelvin modes. Other free mode travelling planetary waves are the com- monly observed modes with periods of around 2, 5, 10 and 16 days. The gravitational modes are usually referred to as Lamb waves (Bretherton 1969; Lindzen and Blake 1972). The Lamb waves are also referred as “gravitational nor- mal modes”. The period of these waves are much shorter as compared to other normal mode waves. The various terms like “Lamb waves”, “Rossby waves”, “Gravitational Abstract A comprehensive study of three normal mode travelling planetary waves, namely the quasi-16, -10 and -5 day waves, is carried out globally using 5 years (2003– 2007) of TIMED/SABER temperature measurements from the stratosphere to the mesosphere-lower thermosphere (MLT) by employing the two dimensional Fourier decom- position technique. From preliminary analysis, it is found that significant amplitudes of normal modes are confined to wave numbers-2 (westward propagating modes) to 2 (east- ward propagating modes). The westward propagating quasi 16-day waves with zonal wave number 1 (W1; W1 refers to westward propagating wave with zonal wave number 1) peaks over winter-hemispheric high latitudes with northern hemisphere (NH) having higher amplitudes as compared to their southern hemispheric (SH) counterpart. The W1 quasi 16-day waves exhibit a double peak structure in alti- tude over winter hemispheric high latitudes. The eastward propagating quasi 16-day waves with wave number 1 (E1; E1 refers to eastward propagating wave with zonal wave number 1) exhibits similar features as that of W1 waves in the NH. In contrast, the E1 quasi 16-day waves in the SH show larger amplitudes as compared to the W1 waves and they do not exhibit double peak structure in altitude. Similar to the quasi 16-day waves, the quasi 10- and 5-day wave amplitudes with respect to their wavenumbers are delineated. Unlike quasi-16 and -10 day waves, quasi-5 day waves peak during vernal equinox both in the SH and NH. The peak activity of the W1 quasi-5 day wave is centered around 40°N and 40°S exhibiting symmetry with respect * Karanam Kishore Kumar kishore_nmrf@yahoo.com 1 Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022, India