Variations of the stratospheric chemical species in the Antartic spring observed by ILAS

Temporal variation of chemical species in the stratosphere was investigated based on observations by the Improved Limb Atmospheric Spectrometer onboard the Advanced Earth Observing Satellite. The zonal mean mixing ratio of nitrous oxide at high latitudes in the Southern Hemisphere increased rapidly during November 1996. During the period the circulation pattern changed from the winter polar vortex to the summer pattern and was influenced by the periodic fluctuation of the planetary wave activities. The altitude on which the polar vortex broke down gradually changed from the upper stratosphere to the lower stratosphere. The vertical gradient of the zonal mean mixing ratio of nitrous oxide showed positive value at the level of the rapid temporal increase. The level of the positive vertical gradient is closely associated with that of the polar vortex breakdown. The variation of the tracer mixing ratio was investigated with respect to the boundary of the polar vortex. The mixing ratios inside and outside of the polar vortex evolved with distinctive patterns with time. The evolution of the polar vortex and the shape of it have significant influences on the zonal mean mixing ratio of tracers.