Effect of Quasi Stationary Wave 1 on Ozone Distribution During November 1993

Microwave Limb Sounder (MLS) observations show southern hemisphere ozone and potential temperature fields that are dominated by quasi stationary wave number one during November 1993. These fields show wave 1 ozone and potential temperature perturbations that are in phase in the lower stratosphere (30 hPa) and in opposition of phase in the upper stratosphere (2 hPa), indicating the role of vertical transport induced by the wave in the presence of vertical gradient. Ozone and potential temperature gradients have the same sign in the lower stratosphere and opposite sign in the upper stratosphere. Ozone field reconstructed using temperature perturbation and the vertical mean gradient is comparable to the observations in the lower stratosphere; while in the upper stratosphere, the amplitude of the reconstructed ozone is smaller, indicating the presence of other process. Diabatic heating field calculated using MLS data and the NCAR radiation model exhibits in the upper stratosphere a strong wave 1 structure, which tend to damp temperature perturbations, inducing cross isentropic ozone transport. This result is supported by ozone distribution on isentropic surface that show a residual wave 1 fluctuation in the upper stratosphere, which is small in the lower stratosphere. Ozone field evolution in the lower stratosphere computed using back trajectories technique shows large filament like equator-ward transport of ozone depleted air over South America region. This transport seems to be associated with the quasi stationary wave, which induce an upward displacement of isentropic surfaces in this region, reducing air density and the potential vorticity gradient.