Reassessment of MIPAS age of air trends and variability
Reassessment of MIPAS age of air trends and variability
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DOI：
10.5194/acp-15-13161-2015
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发表时间：
2015-11
影响因子：
6.3
通讯作者：
F. Haenel;G. Stiller;T. Clarmann;B. Funke;E. Eckert;N. Glatthor;U. Grabowski;S. Kellmann;M. Kiefer;A. Linden;T. Reddmann
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文献类型：
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作者：
F. Haenel;G. Stiller;T. Clarmann;B. Funke;E. Eckert;N. Glatthor;U. Grabowski;S. Kellmann;M. Kiefer;A. Linden;T. Reddmann
抽象的。采用新的改进的 SF6 反演装置以及新校准版本的 MIPAS-ENVISAT 1b 级光谱（版本 5，ESA 数据版本 5.02/5.06），获得了新的全球 SF6 数据集，首次覆盖了 MIPAS 从 2002 年 7 月到 2012 年 4 月的整个观测周期。使用对流层 SF6 参考曲线将月平均和纬向平均 SF6 剖面转换为空气平均年龄。将获得的空气年龄数据集与空气传播年龄测量值进行比较。然后在 10° 纬度和 1-2 公里海拔区域内研究空气平均年龄的时间演变。回归模型由常数项和线性趋势项、准两年振荡变化的两个代理、季节和半年变化的正弦项以及泛音组成，适合空气年龄时间序列。对平流层特定区域的年度周期进行了调查，并与其他研究进行了比较。对由线性项组成的整个 MIPAS 周期内的空气年龄趋势进行了评估，并与 Stiller 等人之前的发现进行了比较。 （2012）。虽然北半球中纬度地区和南极中平流层的平均年龄线性增加被证实为正值，但在北极平流层上层发现了差异，现在发现那里的平均年龄也在增加。与之前的版本相比，北半球中纬度中平流层的趋势幅度略低，并且趋势与 Engel 等人得出的趋势非常吻合。 （2009）。斯蒂勒等人发现空气趋势的负年龄。 （2012）确认了热带平流层最低层和南中纬度平流层最低层。与之前数据版本的差异出现在 25 公里左右的热带平流层中部，目前该区域的趋势为负。总体而言，新的纬度-海拔趋势分布似乎比以前的趋势分布不那么零散，而且更加连贯。新数据提供了布鲁尔-多布森环流浅层分支加速的证据，至少在南半球是这样。最后，将空气年代际趋势与卡尔斯鲁厄中层大气模拟模型 (KASIMA) 模拟 SF6 值计算出的趋势进行比较，结果吻合良好。 MIPAS 数据中发现的半球不对称趋势也反映在 KASIMA 模型使用模拟 SF6 值计算的趋势中。
Abstract. A new and improved setup of the SF6 retrieval together with a newly calibrated version of MIPAS-ENVISAT level 1b spectra (version 5, ESA data version 5.02/5.06) was used to obtain a new global SF6 data set, covering the total observational period of MIPAS from July 2002 to April 2012 for the first time. Monthly and zonally averaged SF6 profiles were converted into mean age of air using a tropospheric SF6-reference curve. The obtained data set of age of air was compared to airborne age of air measurements. The temporal evolution of the mean age of air was then investigated in 10° latitude and 1–2 km altitude bins. A regression model consisting of a constant and a linear trend term, two proxies for the quasi-biennial oscillation variation, sinusoidal terms for the seasonal and semiannual variation and overtones was fitted to the age of air time series. The annual cycle for particular regions in the stratosphere was investigated and compared to other studies. The age of air trend over the total MIPAS period consisting of the linear term was assessed and compared to previous findings of Stiller et al. (2012). While the linear increase of mean age is confirmed to be positive for the northern midlatitudes and southern polar middle stratosphere, differences are found in the northern polar upper stratosphere, where the mean age is now found to increase as well. The magnitude of trends in the northern midlatitude middle stratosphere is slightly lower compared to the previous version and the trends fit remarkably well to the trend derived by Engel et al. (2009). Negative age of air trends found by Stiller et al. (2012) are confirmed for the lowermost tropical stratosphere and lowermost southern midlatitudinal stratosphere. Differences to the previous data versions occur in the middle tropical stratosphere around 25 km, where the trends are now negative. Overall, the new latitude–altitude distribution of trends appears to be less patchy and more coherent than the previous one. The new data provide evidence of an accelerating shallow branch of the Brewer–Dobson circulation, at least in the Southern Hemisphere. Finally the age of air decadal trends are compared to trends calculated with simulated SF6 values by the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and good agreement is found. The hemispheric asymmetry in the trends found in the MIPAS data is also indicated in the trends calculated with simulated SF6 values by the KASIMA model.