Chlorofluorocarbon (CFC) emissions in the latter part of the 20th century reduced stratospheric ozone abundance substantially, especially in the Antarctic region. Simultaneously, polar stratospheric ozone is also destroyed catalytically by nitrogen oxides (NO_x = NO + NO₂) descending from the mesosphere and the lower thermosphere during winter. These are produced by energetic particle precipitation (EPP) linked to solar activity and space weather. Active chlorine (ClO_x = Cl + ClO) can also react mutually with EPP-produced NO_x or hydrogen oxides (HO_x) and transform both reactive agents into reservoir gases, chlorine nitrate or hydrogen chloride, which buffer ozone destruction by all these agents. We study the interaction between EPP-produced NO_x, ClO and ozone over the 20th century by using free-running climate simulations of the chemistry–climate model SOCOL3-MPIOM. A substantial increase of NO_x descending to the polar stratosphere is found during winter, which causes ozone depletion in the upper and mid-stratosphere. However, in the Antarctic mid-stratosphere, the EPP-induced ozone depletion became less efficient after the 1960s, especially during springtime. Simultaneously, a significant decrease in stratospheric ClO and an increase in hydrogen chloride – and partly chlorine nitrate between 10–30 hPa – can be ascribed to EPP forcing. Hence, the interaction between EPP-produced ${\mathrm{NO}}_x/{\mathrm{HO}}_x$ and ClO likely suppressed the ozone depletion, due to both EPP and ClO at these altitudes. Furthermore, at the end of the century, a significant ClO increase and ozone decrease were obtained at 100 hPa altitude during winter and spring. This lower stratosphere response shows that EPP can influence the activation of chlorine from reservoir gases on polar stratospheric clouds, thus modulating chemical processes important for ozone hole formation. Our results show that EPP has been a significant modulator of reactive chlorine in the Antarctic stratosphere during the CFC era. With the implementation of the Montreal Protocol, stratospheric chlorine is estimated to return to pre-CFC era levels after 2050. Thus, we expect increased efficiency of chemical ozone destruction by EPP-NO_x in the Antarctic upper and mid-stratosphere over coming decades. The future lower stratosphere ozone response by EPP is more uncertain.

中文翻译：

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20世纪高能粒子降水对南极平流层氯和臭氧的影响

20 世纪后期的氯氟烃 (CFC) 排放大大减少了平流层臭氧丰度，特别是在南极地区。同时，在冬季，从中间层和低热层下降的氮氧化物（NO _x  =  NO  +  NO ₂ ）也会催化地破坏极地平流层臭氧。这些是由与太阳活动和太空天气相关的高能粒子降水（EPP）产生的。活性氯 (ClO _x  =  Cl  +  ClO) 也可以与 EPP 产生的 NO _x或氢氧化物 (HO _x) 并将这两种反应性试剂转化为储层气体、硝酸氯或氯化氢，从而缓冲所有这些试剂对臭氧的破坏。我们通过使用化学-气候模型 SOCOL3-MPIOM 的自由运行气候模拟来研究 20 世纪EPP 产生的 NO _{x 、ClO 和臭氧之间的相互作用。NO x}大幅增加发现在冬季下降到极地平流层，这会导致平流层上层和中层的臭氧消耗。然而，在南极平流层中部，EPP 引起的臭氧消耗在 1960 年代之后变得不那么有效，尤其是在春季。同时，平流层二氧化氯的显着减少和氯化氢的增加——以及部分在 10-30 hPa 之间的硝酸氯——可归因于 EPP 强迫。因此，EPP 产生的相互作用${\mathrm{不}}_X/{\mathrm{何}}_X$由于 EPP 和二氧化氯在这些海拔高度，二氧化氯可能抑制了臭氧消耗。此外，在本世纪末，冬季和春季在 100 hPa 高度处获得了显着的 ClO 增加和臭氧减少。这种较低的平流层响应表明，EPP 可以影响极地平流层云中储层气体中氯的活化，从而调节对臭氧洞形成很重要的化学过程。我们的研究结果表明，在 CFC 时代，EPP 一直是南极平流层中活性氯的重要调节剂。随着蒙特利尔议定书的实施，平流层氯预计将在 2050 年后恢复到 CFC 时代之前的水平。因此，我们预计 EPP-NO _{x化学臭氧破坏效率会提高}未来几十年在南极上层和中层平流层。EPP 对未来平流层低层臭氧的反应更加不确定。