Joint Impacts Of Two Types Of ENSO And QBO On Winter Stratospheric Ozone In Northern Hemisphere

Using SWOOSH ozone observations,European Centre for Medium Range Weather Forecasting(ECMWF)reanalysis data,and climate model simulations,the independent and joint impacts of the Eastern Pacific El Ni?o-Southern Oscillation(EP ENSO),ENSO Modoki,and quasi-biennial oscillation(QBO)on stratospheric ozone in the Northern Hemisphere(NH)during winter were investigated in this thesis.Then the underlying mechanism is discussed.Main results are obtained as follows:1.The stratospheric ozone is increased in the NH in winter during El Ni?o events and the east wind phases of the QBO(EQBO)but decreased during La Ni?a events and the west wind phases of the QBO(WQBO).Using observational data,it was found that the Arctic polar vortex weakened and warming during the EP El Ni?o and EQBO phases,while increased and cooling during the EP La Ni?a and WQBO phases.And the change of wave-1 planetary wave is the main reason for the Arctic polar vortex change caused by EP ENSO and QBO.The features of the joint effect of EP ENSO and QBO on stratospheric ozone were further analyzed.The results show that during EQBO phases,the stratospheric ozone anomalies are amplified during El Ni?o events but reduced during La Ni?a events,and vice versa during WQBO phases.Numerical sensitivity experiments are performed to further investigate the independent and joint impacts of ENSO and QBO on stratospheric ozone in the NH during winter.The results from simulations agree well with the results from statistical analysis.In addition,the model results also show that the joint effects of EP ENSO event and QBO on stratospheric ozone in the NH in winter are related to their independent nonlinear interactions.2.During the EQBO phase,the stratospheric ozone anomalies in the NH were amplified during El Ni?o Modoki events but reduced during La Ni?a Modoki events.During WQBO phases,the El Ni?o Modoki events only weakly increased the stratosphere ozone concentration in the NH in winter,while the ozone concentration was greatly reduced during the La Ni?a Modoki events.The stratospheric ozone in the NH in winter is increased during El Ni?o Modoki events but decreased during La Ni?a Modoki events.Moreover,the effect of ENSO Modoki event on stratospheric ozone in the NH in winter is the result of the interaction of wave-1 planetary wave and wave-2 planetary wave.The features of the joint effect of ENSO Modoki and QBO on stratospheric ozone were further analyzed.The results show that EQBO enhanced the effect of El Ni?o Modoki events on stratospheric ozone in the NH,but weakened the effect of La Ni?a Modoki events.WQBO weakened the effect of El Ni?o Modoki on stratospheric ozone in the NH,but enhanced the effect of La Ni?a Modoki events.The comparison shows that the responses of the wave-1 and wave-2 planetary waves to EP ENSO activity are different from that to ENSO Modoki activity.During the EP El Ni?o and La Ni?a events,the wave-1(wave-2)planetary waves anomaly are strongly in phase(out of phase)with the background stationary wave-1(wave-2)planetary waves,while the phase of the wave-1(wave-2)response is in approximate quadrature with the background wave-1(wave-2)in the stratosphere during El Ni?o and La Ni?a Modoki periods.It can be seen that the stratospheric planetary waves in the NH in winter have different responses to the EP ENSO event and ENSO Modoki event.This also led to the position of the wave-1(wave-2)planetary waves on the EQBO or WQBO phase,which is almost the same as the response position to the EP ENSO,but different from the response position of ENSO Modoki.