Multimodel estimates of atmospheric lifetimes of long-lived ozone-depleting substances: Present and future
Multimodel estimates of atmospheric lifetimes of long-lived ozone-depleting substances: Present and future
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DOI：
10.1002/2013jd021097
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发表时间：
2014-03-16
影响因子：
4.4
通讯作者：
Tummon, F.
中科院分区：
文献类型：
--
作者：
Chipperfield, M. P.;Liang, Q.;Tummon, F.
我们利用六个三维化学-气候模型和一个二维模型，对地表排放和平流层移除的长寿命源气体的寿命进行了诊断。这些模型都使用了相同的标准光化学数据。我们研究了不同寿命定义的影响，包括在混合比（MBC）和通量（FBC）边界条件下运行模型。在同一模型内，不同方法诊断出的寿命吻合良好。使用fbc和MBCs会导致不同的示踪剂负担，因为MBC值中包含的隐含寿命不一定与模型自己计算的寿命相匹配。一般来说，不同模式计算出的寿命差异要大得多，其主要原因是模拟出的热带平流层中下层的上升速率和水平混合速率的变化。模型运行已用于计算瞬时和稳态寿命。对于氟氯化碳（CFCs），其生长阶段的大气分布直到20世纪80年代都远未达到稳定状态，因此诊断出的瞬时寿命要长得多。停止排放后，氟氯化碳的衰变更接近于稳定状态。对于2100年的条件，模式环流速度一般会增加，但由于恢复和气候变化导致的更厚的臭氧层会降低光解速率。这些影响进行了补偿，因此对模拟寿命的净影响很小。在今后对平流层臭氧的评估中，使用氟氯化碳将使氯氟烃去除速率和模式环流速率之间保持一致的平衡。
We have diagnosed the lifetimes of long-lived source gases emitted at the surface and removed in the stratosphere using six three-dimensional chemistry-climate models and a two-dimensional model. The models all used the same standard photochemical data. We investigate the effect of different definitions of lifetimes, including running the models with both mixing ratio (MBC) and flux (FBC) boundary conditions. Within the same model, the lifetimes diagnosed by different methods agree very well. Using FBCs versus MBCs leads to a different tracer burden as the implied lifetime contained in the MBC value does not necessarily match a model's own calculated lifetime. In general, there are much larger differences in the lifetimes calculated by different models, the main causes of which are variations in the modeled rates of ascent and horizontal mixing in the tropical midlower stratosphere. The model runs have been used to compute instantaneous and steady state lifetimes. For chlorofluorocarbons (CFCs) their atmospheric distribution was far from steady state in their growth phase through to the 1980s, and the diagnosed instantaneous lifetime is accordingly much longer. Following the cessation of emissions, the resulting decay of CFCs is much closer to steady state. For 2100 conditions the model circulation speeds generally increase, but a thicker ozone layer due to recovery and climate change reduces photolysis rates. These effects compensate so the net impact on modeled lifetimes is small. For future assessments of stratospheric ozone, use of FBCs would allow a consistent balance between rate of CFC removal and model circulation rate.