Record ozone loss was observed in the stratospheric Arctic in the spring of 2011. In the present work, we show observational evidence that the record loss of Arctic ozone is due to the extremely cold and persistent stratospheric polar vortex in the winter of 2010-2011. The polar vortex was as usual in early winter, but was intensified twice in middle January and middle February, respectively, and remained anomalously strong and stable until early April, 2011. Record low polar temperatures and record high subpolar zonal winds occurred in February and March. Stratospheric wave activity was anomalously weak because waves were refracted equatorward by the anomalously strong polar night jet. With such an extremely cold and isolated environment, Arctic stratospheric ozone was largely depleted in March and early April, 2011. Corresponding to Arctic ozone depletion, the stratospheric Northern-Hemisphere Annular Mode (NAM) displayed anomalously strong high-polarity, and the positive stratospheric NAM propagated downward and led to anomalously strong positive NAM in the troposphere and near the surface.
How the Hadley circulation changes in response to global climate change and how its change impacts upon regional and global climates has generated a lot of interest in the literature in the past few years. In this paper, consistent and statistically significant poleward expansion of the Hadley circulation in the past few decades is demonstrated, using independent observational datasets as proxy measures of the Hadley circulation. Both observational outgoing longwave radiation and precipitation datasets show an annual average total poleward expansion of the Hadley cells of about 3.6° latitude. Sea level pressure from observational and reanalysis datasets show smaller magnitudes of poleward expansion, of about 1.2° latitude. Ensemble general circulation model simulations forced by observed time-varying sea surface temperatures were found to generate a total poleward expansion of about 1.23°latitude. Possible mechanisms behind the changes in the horizontal extent of the Hadley circulation are discussed.
对再分析资料的合成分析表明,10 h Pa北半球环状模（NAM）指数和东北亚地区地面温度（SAT）存在显著的后滞相关关系。正/负位相平流层NAM异常事件往往伴随着东北亚地区正/负异常地面温度变化。负位相NAM指数超前东北亚地面温度异常20～40天,正位相NAM指数超前约20天。定义了有效平流层极端事件（ESE）,并研究了不同标准下平流层NAM异常能够传到对流层的比例。研究表明,NAM异常下传的比例随定义标准的提高而增加。研究结果显示,平流层大气环流异常在一定程度上能够作为先兆因子来延长中国北方冬季对流层天气预报。
21世纪平流层气候变化主要由两个因素所决定,一个是臭氧层恢复造成的变暖,另一个是温室气体增加造成的变冷。针对在这两种相反的辐射效应作用下,平流层气温如何变化这一重要问题,使用CMIP5未来情景模拟试验的结果,对2006—2100年间的平流层温度的变化趋势进行分析。结果表明,臭氧恢复的增温效应在平流层低层起主导作用,而温室气体增加的冷却效应在平流层高层起主导作用,因此,平流层低层(70 h Pa以下)呈变暖趋势,而平流层中高层呈变冷趋势。通过对包含完整平流层的气候模式(高顶模式)和只包含部分平流层的气候模式(低顶模式)预估的温度趋势的差异进行分析,发现高顶模式预估的变暖趋势大于低顶模式的结果,这意味着模式是否包含完整平流层有可能对预估的平流层和对流层未来气候变化有重要影响。
