Investigations Of The Long-term Variability Of Global Total Column Ozone And Its Impacts On Regional Climate Change

Despite of the small amount in the atmosphere, ozone is one of the most critical atmospheric component as it protects human beings and any other life forms on the Earth from the Sun’s high frequency ultraviolet radiation. Due to uncontrolled anthropogenic emissions of the substances such as chlorofluorocarbons after the industry revolution, ozone amount in the atmosphere has been greatly depleted through photochemical reactions with those ozone depleting substances, in particularly over the Antarctica, where dramatic ozone depletion occurred in the past decades resulting in the well-known "ozone hole" effects. The direct consequence of ozone hole phenomenon is that lots of harmful ultraviolet radiation will penetrate the ozone layer coming down to the earth surface to threat the life forms health on the Earth. Meanwhile, ozone depletion will result in significant regional climate changes due to its forcing effect. However, due to the implementation of the Montreal Protocol, the total amount of ozone depleting substances in the atmosphere has been prominent reduced, and in turn the ozone layer starts to recovery. Since ozone depletion has caused significant regional climate changes, the recovery of the ozone layer thus would result in new climate changes. Within this context, investigations of the long-term variability of global total column ozone in the past decades to project the future ozone recovery and the mechanisms between regional climate changes and ozone depletion would be much helpful in better prediction of the changing climate.In this thesis, several studies relevant to the aforementioned topics have been conducted, results and conclusions can be generally summarized as follows:1) cross-mission biases are observed between multi sensors total column ozone products. These observed biases are nonlinear and non-stationary in the spatiotemporal domain, which makes it difficult to be removed and a big obstacle for merging multi sensors observations to create a long-term record. In order to remove those observed nonlinear and non-stationary cross-mission total column ozone biases, a new algorithm relying on the distribution mapping theory was proposed in this study. Practical applications of this modified algorithm indicates that the modified algorithm works efficiently in addressing those complex biases. Compared to previous data, bias corrected data are more consistent in the spatiotemporal domain.2) Singular Spectrum Analysis (SSA) was applied to derive the long-term variability of total column ozone at the global scale during the time period of 1979-2015. Before that, SSA was compared with Ensemble Empirical Mode Decomposition (EEMD) to analyze the accuracy and stability of both methods. It shows that results from SSA are much more stable and accurate than EEMD. In addition, SSA works much more efficient than EEMD. Based on the derived long-term variability, the total column ozone variability in the past decades has been divided into three different phases, with ozone depletion during 1979-1994 and transition during 1995-2005 as well as ozone recovery since 2006.3) Assuming a constant response of total column ozone to the implementation of Montreal Protocol in the coming decades, forecasted results from DHR models indicate that the ozone layer in the Northern Hemisphere will recover to its 1980’s level by about 2030 while approximately by 2040 in the Southern Hemisphere.4) Quantified precipitation responses to each climatic forcing factors indicate that Antarctic ozone depletion is the predominant forcing factor in contributing to the observed wetting climate over the extratropics in the Southern Hemisphere. In addition, the equatorial SST anomaly was observed to play an important role in modulating the variability of austral extratropical precipitation. Differed from those results obtained in large climate modelling experiments highlighting the relative role of the increasing greenhouse gases concentration in modulating the global scale climate, results from this study found a very weak contribution of greenhouse gases in affecting the austral extratropical precipitation. Thus, further investigations are required. Coupled MCA patterns between Antarctic ozone depletion and austral wind suggest that the Antarctic ozone depletion has caused a pole-ward shift of the circulation pattern, which in turn resulted in significant regional climate changes.