Role of Stratospheric Processes in Climate Change: Advances and Challenges

In this review,instead of summarizing all the advances and progress achieved in stratospheric research,the main advances and new developments in stratosphere-troposphere coupling and stratospheric chemistry-climate interactions are summarized,and some outstanding issues and grand challenges are discussed.A consensus has been reached that the stratospheric state is an important source of improving the predictability of the troposphere on sub-seasonal to seasonal(S2S)time scales and beyond.However,applying stratospheric signals in operational S2S forecast models remains a challenge because of model deficiencies and the complexities of the underlying mechanisms of stratosphere-troposphere coupling.Stratospheric chemistry,which controls the magnitude and distribution of many important climate-forcing agents,plays a critical role in global climate change.Convincing evidence has been found that stratospheric ozone depletion and recovery have caused significant tropospheric climate changes,and more recent studies have revealed that stratospheric ozone variations can even exert an impact on SSTs and sea ice.The climatic impacts of stratospheric aerosols and water vapor are also important.Although their quantitative contributions to radiative forcing have been reasonably well quantified,there still exist large uncertainties in their long-term impacts on climate.The advances and new levels of understanding presented in this review suggest that whole-atmosphere interactions need to be considered in future for a better and more thorough understanding of stratosphere-troposphere coupling and its role in climate change.

The Influence of Meridional Variation in North Pacific Sea Surface Temperature Anomalies on the Arctic Stratospheric Polar Vortex

This study examines the dependence of Arctic stratospheric polar vortex(SPV)variations on the meridional positions of the sea surface temperature(SST)anomalies associated with the first leading mode of North Pacific SST.The principal component 1(PC1)of the first leading mode is obtained by empirical orthogonal function decomposition.Reanalysis data,numerical experiments,and CMIP5 model outputs all suggest that the PC1 events(positive-minus-negative PC1 events),located relatively northward(i.e.,North PC1 events),more easily weaken the Arctic SPV compared to the PC1 events located relatively southward(i.e.,South PC1 events).The analysis indicates that the North PC1-related Aleutian low anomaly is located over the northern North Pacific and thus enhances the climatological trough,which strengthens the planetary-scale wave 1 at mid-to-high latitudes and thereby weakens the SPV.The weakened stratospheric circulation further extends into the troposphere and favors negative surface temperature anomalies over Eurasia.By contrast,the South PC1-related Aleutian low anomaly is located relatively southward,and its constructive interference with the climatological trough is less efficient at high latitudes.Thus,the South PC1 events could not induce an evident enhancement of the planetary-scale waves at high latitudes and thereby a weakening of the SPV on average.The Eurasian cooling associated with South PC1 events(positive-minus-negative PC1 events)is also not prominent.The results of this study suggest that the meridional positions of the PC1 events may be useful for predicting the Arctic SPV and Eurasian surface temperature variations.

用于EUV图案化的新型氧化锌簇交联策略的辐射化学

由于C=C双键交联反应机制的成熟,金属氧化物光刻胶得到了广泛的发展.然而,由于不稳定的C=C双键,这种材料需要低温和遮光存储.在此,首次在金属氧簇中提出了C-F键交联策略用于光刻图案化.以光刻胶Zn-TBA为例,它形成光滑无缺陷的薄膜,且表面粗糙度Rq小于0.2 nm.使用极紫外(EUV)干涉掩模,在65 mJ cm^(-2)曝光剂量下形成37.5 nm的半周期(HP)图案.在EUV曝光和正己烷显影后,通过原子力显微镜(AFM)观察到负性光刻胶形貌.重要的是,Zn-TBA可以在室温和明亮的环境中储存.除了脱羧之外,我们还提出光引发的C-F交联是Zn-TBA图案的主要贡献者,并通过高分辨率X射线光电子能谱(HRXPS)和密度泛函理论(DFT)计算得以证明.这种新颖的光刻机制为下一代金属基材料的设计提供了新的思路.