How robust are stratospheric age of air trends from different reanalyses?
How robust are stratospheric age of air trends from different reanalyses?
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DOI：
10.5194/acp-19-6085-2019
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发表时间：
2019-01
影响因子：
6.3
通讯作者：
F. Ploeger;B. Legras;E. Charlesworth;Xiaolu Yan;Mohamadou A. Diallo;P. Konopka;T. Birner;Mengchu Tao-Meng
中科院分区：
文献类型：
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作者：
F. Ploeger;B. Legras;E. Charlesworth;Xiaolu Yan;Mohamadou A. Diallo;P. Konopka;T. Birner;Mengchu Tao-Meng
摘要。在模式预测中，加速的布鲁尔-多布森环流（BDC）是气候变化的一个强有力的信号，但已受到微量气体观测的质疑。我们分析了平流层平均空气年龄和全年龄谱作为BDC及其趋势的度量。利用ERA-Interim、JRA-55和MERRA-2再分析数据驱动的平流层化学拉格朗日模型（CLaMS）计算空气年龄，以评估当前一代气象再分析中BDC表征的稳健性。再分析结果表明，JRA-55的平均年龄最小，MERRA-2的平均年龄最大。年龄谱分析表明，MERRA-2较老的空气与较强的谱尾有关，这可能与较弱的热带上升流和较强的再环流有关。平流层运输的季节性在再分析中得到了强有力的体现，具有相似的平均年龄变化和年龄谱峰。1989 - 2015年的长期变化与再分析结果相似，主要是平均年龄下降，同时年龄谱峰向更短的传输时间移动，类似于气候模式模拟中对温室气体浓度增加的强迫响应。在较短的时间内，1989-2001年和2002-2015年，空气变化的年龄不那么强劲。根据最近的卫星观测，只有ERA-Interim显示了2002年至2015年半球偶极子模式的年龄变化。因此，在当前的再分析中，BDC的年代际变化的表示似乎不那么稳健，这是BDC建模的主要不确定性。
Abstract. An accelerating Brewer–Dobson circulation (BDC) is a robust signal of climate change in model predictions but has been questioned by trace gas observations. We analyse the stratospheric mean age of air and the full age spectrum as measures for the BDC and its trend. Age of air is calculated using the Chemical Lagrangian Model of the Stratosphere (CLaMS) driven by ERA-Interim, JRA-55 and MERRA-2 reanalysis data to assess the robustness of the representation of the BDC in current generation meteorological reanalyses. We find that the climatological mean age significantly depends on the reanalysis, with JRA-55 showing the youngest and MERRA-2 the oldest mean age. Consideration of the age spectrum indicates that the older air for MERRA-2 is related to a stronger spectrum tail, which is likely associated with weaker tropical upwelling and stronger recirculation. Seasonality of stratospheric transport is robustly represented in reanalyses, with similar mean age variations and age spectrum peaks. Long-term changes from 1989 to 2015 turn out to be similar for the reanalyses with mainly decreasing mean age accompanied by a shift of the age spectrum peak towards shorter transit times, resembling the forced response in climate model simulations to increasing greenhouse gas concentrations. For the shorter periods, 1989–2001 and 2002–2015, the age of air changes are less robust. Only ERA-Interim shows the hemispheric dipole pattern in age changes from 2002 to 2015 as viewed by recent satellite observations. Consequently, the representation of decadal variability of the BDC in current generation reanalyses appears less robust and is a major uncertainty of modelling the BDC.