Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period
Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period
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DOI：
10.5194/acp-12-3311-2012
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发表时间：
2011-10
影响因子：
6.3
通讯作者：
G. Stiller;T. Clarmann;F. Haenel;B. Funke;N. Glatthor;U. Grabowski;S. Kellmann;M. Kiefer;A. Linden
中科院分区：
文献类型：
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作者：
G. Stiller;T. Clarmann;F. Haenel;B. Funke;N. Glatthor;U. Grabowski;S. Kellmann;M. Kiefer;A. Linden
抽象的。由分布在整个地球仪的MIPAS测量的超过106个SF6垂直廓线组成的一个广泛的观测数据集已被浓缩成2002年9月至2010年1月期间空气平均年龄的月纬向平均值，在10°纬度和1-2 km高度处分组。通过拟合由常数和线性增加项、QBO变化的2个代理、季节性和半年变化的正弦项以及用于对观测数据集的形状进行校正的泛音组成的回归模型，分析了数据的时间变化。评估了中层SF6贫化空气下沉和混入非极地纬度对中纬度空气绝对年龄及其线性增长的影响，发现影响很小。对于北方大部分中纬度地区、热带平流层中部、南方中纬度地区部分地区以及南极平流层上部，平流层空气平均年龄的线性增长被认为是正的，并且部分大于Engel等人（2009年）得出的趋势。在热带平流层的最低层和最高层、南部中纬度部分地区和北方极地地区，空气的年龄呈多年下降趋势。对季节变化幅度和相位的分析有助于了解平流层区域之间的相互耦合。特别是，北方中纬度平流层与热带地区耦合良好，而北方最低的中纬度平流层是分离的，证实了布鲁尔-多布森环流的浅分支与深分支的分离。我们建议一个整体增加的热带上升流，连同减弱的混合障碍，特别是在北方半球，作为一个假设的模型来解释所观察到的模式的线性多年增加/减少，振幅和相位的季节变化。
Abstract. An extensive observational data set, consisting of more than 106 SF6 vertical profiles from MIPAS measurements distributed over the whole globe has been condensed into monthly zonal means of mean age of air for the period September 2002 to January 2010, binned at 10° latitude and 1–2 km altitude. The data were analysed with respect to their temporal variation by fitting a regression model consisting of a constant and a linear increase term, 2 proxies for the QBO variation, sinusoidal terms for the seasonal and semi-annual variation and overtones for the correction of the shapes to the observed data set. The impact of subsidence of mesospheric SF6-depleted air and in-mixing into non-polar latitudes on mid-latitudinal absolute age of air and its linear increase was assessed and found to be small. The linear increase of mean age of stratospheric air was found to be positive and partly larger than the trend derived by Engel et al. (2009) for most of the Northern mid-latitudes, the middle stratosphere in the tropics, and parts of the Southern mid-latitudes, as well as for the Southern polar upper stratosphere. Multi-year decrease of age of air was found for the lowermost and the upper stratospheric tropics, for parts of Southern mid-latitudes, and for the Northern polar regions. Analysis of the amplitudes and phases of the seasonal variation shed light on the coupling of stratospheric regions to each other. In particular, the Northern mid-latitude stratosphere is well coupled to the tropics, while the Northern lowermost mid-latitudinal stratosphere is decoupled, confirming the separation of the shallow branch of the Brewer-Dobson circulation from the deep branch. We suggest an overall increased tropical upwelling, together with weakening of mixing barriers, especially in the Northern Hemisphere, as a hypothetical model to explain the observed pattern of linear multi-year increase/decrease, and amplitudes and phase shifts of the seasonal variation.