A Numerical Study on Intraseasonal Variations in Planetary Waves and Ozone Distribution in the Southern Hemisphere Stratosphere

The column ozone distribution in southern hemisphere (SH) have a maximum in midlatutede called subpolar maximum and the location of the maximum gradually shifts poleward as the seasonal progress from late winter to early spring. From the dynamical aspect, a quasi-periodic amplification of planetary wave with wavenumber 1 (wave 1) is observed in the stratosphere in SH. Some resent analyses of the satellite data suggested that the amplification is caused by the interaction with an eastward traveling wave with wavenumber 2 (wave 2). However, it is not well understood that mechanisms of the subpolar maximum formation and wave 1 amplification through the interaction with the eastward traveling wave. First part of this thesis explores fundamental roles of planetary waves on the formation of the subpolar maximum and its poleward shift in early spring under simplified conditions. Second part shows that horizontal variation of the total ozone content can be realized more realistically in the context of the wave 1-wave 2 interaction. The mechanism of the wave 1 amplification interacting with wave 2 is explored in the third part. Semi-spectral models with low-order longitudinal truncation are used to express the transient transport process and the interaction among waves and mean flow. The hemispheric version of the model is used to simulate the wave 1 amplification. The spherical version of the model is used to reveal roles of planetary wave amplification on the ozone transport and formation of the subpolar maximum. A series of experiment calculating ozone transports during planetary wave amplification for each month reveals the roles of planetary waves on the formation of subpolar maximum. Amplification of planetary waves in SH winter induces a meridional circulation whose downward motion is concentrated into the midlatitude lower stratosphere, and results in the ozone increase there. On the other hand, meridional circulation in the northern hemisphere(NH) extends to the polar stratosphere and contributes to the formation of ozone maximum in the polar region throughout winter. Diagnoses based on TEM theory and wave-propagation theory show that the asymmetric circulation between SH and NH is arisen from the difference of propagation field of waves. Planetary waves in SH propagates equatorward through a maximum line of refractive index which makes the convergence region of EP flux in the midlatitude stratosphere. Therefore, the residual circulation cannot reach the SH polar region. It is shown that the amplification of wave 1 and associated temporal variation of horizontal ozone distribution can be realized in the framework of the interaction between stationary wave with wavenumber 1 and eastward traveling wave with wavenumber 2. From the analyses of energetic, it was found that the amplification of wave 1 is attributed to the abrupt decrease of kinetic energy conversion to the zonal-mean flow which is caused by suppression of equatorward propagation of the wave 1. The wave-wave interaction decreases the phase gradient during the amplification stage and increases it during the post-amplification stage. The combined system of the wave-mean flow and wave-wave interactions causes the periodic amplification of wave 1, which leads to realistic representation of ozone distibusion in SH.