Three‐dimensional simulations of stratospheric N2O: Predictions for other trace constituents
Three‐dimensional simulations of stratospheric N2O: Predictions for other trace constituents
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平流层 N2O 的三维模拟：对其他痕量成分的预测
DOI：
10.1029/jd091id02p02687
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发表时间：
1986
影响因子：
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通讯作者：
W. Moxim
中科院分区：
文献类型：
--
作者：
J. Mahlman;H. Levy;W. Moxim
利用地球物理流体动力学实验室（GFDL）三维环流/示踪模型研究了一系列光破坏假设下N2O在平流层中的行为。与这些模拟的观测结果比较表明，大气N2O的寿命在100至130年之间。在三个实验中发现，一个实验的模型导出的全局一维涡扩散系数Kz也适用于其他两个实验。此外，在平流层下部，三个实验中N2O混合比等值线的经向斜率几乎相同。用一个简单的“两板”模型探讨了这两个结果的普遍性。该模型直接求解了微量气体等值线的平衡子午斜率和Kz值。该模型预测，具有弱光破坏速率的长寿命气体应具有相似的经向斜率，但更快的破坏效果是使经向斜率变平。简单模型还预测，Kz取决于化学过程，它直接依赖于给定气体的经向斜率，也依赖于向上传播的对流层扰动对平流层纬向风的强度。三个N2O实验与详细的观测分析进行了比较。这些分析表明，模式经向N2O斜坡过于平坦约30%。简单的两板模式表明，这是由模式平流层纬向风的微弱强迫造成的。将模型N2O的时间变率与Ehhalt等人（1983）的“Δ”统计数据进行比较，结果非常吻合。另一个简单的理论模型被提出，它显示了为什么Δ统计如此有用，并预测了不同的破坏化学反应会导致不同的Δ统计的情况。这些结果使得三个N2O数值实验的一个非常普遍的外推可以预测一类长寿命微量气体的结构。具体来说，支持理论的发展允许预测化学对全球（一维）行为、经向高度（二维）结构和局部时间变率的影响。最后，通过模型时间序列给出了与可用测量点相对应的瞬态行为的一些例子。在水平N2O图的支持下，这些时间序列显示出复杂的行为，包括明显的季节周期，运输产生的N2O“逆温”，以及与瞬态平流层扰动相关的详细经向运输事件。
The Geophysical Fluid Dynamics Laboratory (GFDL) three-dimensional general circulation/tracer model has been used to investigate the stratospheric behavior of N2O under a range of photodestruction hypotheses. A comparison of observations with these simulations shows that the atmospheric N2O lifetime lies between 100 and 130 years. For the three experiments conducted, it was found that the model-derived global one-dimensional eddy diffusion coefficients Kz for one experiment are appropriate for the other two experiments as well. In addition, the meridional slopes of N2O mixing ratio isolines are virtually identical in the lower stratosphere for all three experiments. The generality of these two results was explored with a simple “two-slab” model. In this model the equilibrium meridional slopes of trace gas isolines and Kz values are solved directly. The model predicts that long-lived gases with weak photodestruction rates should have similar meridional slopes, but the effect of faster destruction is to flatten the meridional slopes. The simple model also predicts that Kz depends upon chemical processes through a direct dependence upon the meridional slope for a given gas as well as upon the intensity with which upward propagating tropospheric disturbances force the stratospheric zonal winds. The three N2O experiments have been compared against detailed observational analyses. These analyses show that the model meridional N2O slopes are too flat by about 30%. The simple two-slab model indicates that this results from a somewhat weak forcing of the model stratospheric zonal winds. A comparison of the temporal variability of model N2O against the “Δ” statistics of Ehhalt et al. (1983) shows good agreement. Another simple theoretical model is proposed that shows why Δ statistics are so useful and predicts the circumstances under which different destruction chemistries should lead to different Δ statistics. These results have allowed a very general extrapolation of the three N2O numerical experiments to predicted structure for a wide class of long-lived trace gases. Specifically, the supporting theoretical developments allow predictions for the effect of chemistry on the global (one-dimensional) behavior, meridional-height (two-dimensional) structure, and local temporal variability. Finally, some examples of transient behavior are presented through model time series at points corresponding to available measurements. These time series, with the support of horizontal N2O charts, show complex behavior, including pronounced seasonal cycles, transport-produced N2O “inversions,” and detailed meridional transport events associated with transient stratospheric disturbances.