Stratosphere-troposphere exchange in the vicinity of a tropopause fold
Stratosphere-troposphere exchange in the vicinity of a tropopause fold
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DOI：
10.5194/acp-2015-949
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发表时间：
2016-01
影响因子：
6.3
通讯作者：
C. Hofmann;A. Kerkweg;P. Hoor;P. Jöckel
中科院分区：
文献类型：
--
作者：
C. Hofmann;A. Kerkweg;P. Hoor;P. Jöckel
抽象。空气质量沿沿着对流层顶褶皱从平流层向对流层的输送可导致地面臭氧浓度达到峰值，从而影响对流层臭氧的长期趋势。为了更好地理解负责的过程和交换的首选区域，在对流层顶褶皱附近的瞬态和可逆的交换过程进行了分析的基础上的案例研究。应用了全球和区域大气化学模式系统MECO（n），它将有限区域大气化学和气候模式COSMO-CLM/MESSy与全球大气化学模式ECHAM 5/MESSy（EMAC）耦合起来。在两个模型实例中使用类似的过程参数化，该系统允许在不同的空间分辨率下进行非常一致的同步模拟。用观测资料对平流层气团下降引起的地面臭氧增强进行了模拟评价。由于全球模式的分辨率较低，全球模式实例无法捕捉到观测到的臭氧增强。然而，更精细的解决方案，区域模式实例的结果与测量吻合得很好。本文结合欧拉和拉格朗日分析方法，指出对流层顶褶皱附近的平流层对流层交换（STE）发生在湍流和非绝热过程区。在拉格朗日研究的框架内，对对流层顶褶皱沿着混合的效率进行了量化，表明几乎所有（97%）起源于对流层顶褶皱的空气质量在接下来的两天内都被输送到对流层中。
Abstract. Transport of air masses from the stratosphere to the troposphere along tropopause folds can lead to peaked ozone concentrations at ground level and hereby influence the long-term trend of tropospheric ozone. To improve the understanding of responsible processes and preferred regions of exchange, transient and reversible exchange processes in the vicinity of a tropopause fold are analysed on the basis of a case study. The global and regional atmospheric chemistry model system MECO(n), which couples the limited-area atmospheric chemistry and climate model COSMO-CLM/MESSy to the global model ECHAM5/MESSy for Atmospheric Chemistry (EMAC) is applied. Using similar process parametrisations in both model instances, the system allows for very consistent, simultaneous simulations at different spatial resolutions. Simulated ozone enhancements at ground level, caused by descending stratospheric air masses, are evaluated with observational data. Because of the coarse resolution of the global model, the observed ozone enhancements are not captured by the global model instance. However, the results of the finer resolved, regional model instance coincide well with the measurements. Based on the combination of Eulerian and Lagrangian analysis methods it is shown that stratosphere-troposphere-exchange (STE) in the vicintity of the tropopause fold occurs in regions of turbulence and diabatic processes. Within the framework of a Lagrangian study the efficiency of mixing along a tropopause fold is quantified, showing that almost all (97 %) of the air masses originating in the tropopause fold are transported into the troposphere during the following two days.