Model studies of chlorine deactivation and formation of ClONO2 collar in the Arctic polar vortex
Model studies of chlorine deactivation and formation of ClONO2 collar in the Arctic polar vortex
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DOI：
10.1029/96jd00442
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发表时间：
1997-01-20
影响因子：
4.4
通讯作者：
Roche, AE
中科院分区：
文献类型：
--
作者：
Chipperfield, MP;Lutman, ER;Roche, AE
我们研究了导致活性氯 (ClO + 2Cl(2)O(2)) 失活以及在北极极地涡旋内部和周围形成 ClONO2 的过程。通过使用一系列三维和轨迹模型，在 1991/1992 年冬季气象分析的推动下，我们已经能够将与模型公式和分辨率相关的过程与真实的化学过程分开。由于较差的传输方案或低分辨率导致的数值扩散，在三维模型中，ClO 失活的速率可能会被高估。在我们的实验中，我们发现垂直分辨率至少与水平分辨率一样重要。等熵水平的使用通过提供水平和垂直运动之间的真正分离来减少虚假垂直混合。增加模型的水平分辨率会减少混合，并产生更锐利、更窄的 ClONO2 环区域，且最大值略高。域填充轨迹产生 ClONO2 领结构，包裹之间没有混合。这些结果表明，正是 ClO 的原位化学失活而不是混合产生了 ClONO2 项圈。将高分辨率等熵模拟和域填充轨迹的结果与低温肢体阵列标准具光谱仪数据进行比较，并诊断出 ClO 失活的化学原因。这些模型通常再现了观察到的领口区域特征，但低估了最高的 ClONO2 混合比。由于极地平流层下部严重脱氧，ClONO2 恢复的原因是从 HNO3 中释放出 NO2。对于这个过程，HNO3 与 OH 的反应与高太阳天顶角下的光解作用一样重要。
We have investigated the processes which lead to the deactivation of active chlorine (ClO + 2Cl(2)O(2)) and the formation of ClONO2 in and around the Arctic polar vortex. By using a range of three-dimensional and trajectory models, forced by meteorological analyses for the 1991/1992 winter, we have been able to separate processes associated with the model formulation and resolution, from true chemical processes. The rate of ClO deactivation can be overestimated in a three-dimensional model due to numerical diffusion from a poor transport scheme or to low resolution. In our experiments we found that vertical resolution is at least as important as horizontal resolution. The use of isentropic levels reduced the spurious vertical mixing by providing a true separation between horizontal and vertical motion. Increasing the horizontal resolution of the model reduced mixing and produced a sharper, narrower ClONO2 collar region with slightly higher maximum values. The domain-filling trajectories produce a ClONO2 collar structure with no mixing between parcels. These results show that it is in situ chemical deactivation of ClO and not mixing which produces the ClONO2 collar. Results from the high-resolution isentropic simulations and domain-filling trajectories have been compared with Cryogenic Limb Array Etalon Spectrometer data and diagnosed for the chemical cause of ClO deactivation. The models generally reproduce the observed features of the collar region but underestimate the highest ClONO2 mixing ratios. As the polar lower stratosphere is heavily denoxified the cause of the ClONO2 recovery is release of NO2 from HNO3. For this process, reaction of HNO3 with OH can be as important as photolysis at high solar zenith angles.