Abstract Energetic particle precipitation is one of the main processes by which the sun influences atmospheric composition and structure. The polar middle atmosphere is chemically disturbed by the precipitation-induced production of nitric oxides (NOx) and hydrogen oxides (HOx) and the associated ozone (O3) loss, but the importance for the dynamics is still debated. The role of precipitating medium energy electrons (MEEs), which are able to penetrate into the mesosphere, has received increased attention, but has only recently begun to be incorporated in chemistry-climate models. We use the NCAR Whole Atmosphere Community Climate Model (WACCM) to study the climate impact from MEE precipitation by performing two idealized ensemble experiments under pre-industrial conditions, with and without the MEE forcing, over the period of the solar cycle 23 (only full calendar years, 1997–2007). Each experiment includes 20 11-year ensemble members, total 220 years. Our results indicate a strong month-to-month variability in the dynamical response to MEE throughout the winter period. We find a strengthening of the polar vortex in the northern hemisphere during December, but the signal decays rapidly in the following months. The polar vortex strengthening is likely attributable to planetary wave reduction due to increased zonal symmetries in upper stratospheric ozone heating, initially triggered by MEE-induced NOx advected into the sunlit regions. We also find a similar early winter polar vortex strengthening in the southern hemisphere during June. Changes in mean meridional circulation accompany these anomalous wave forcings, leading to dynamically-induced vertical temperature dipoles at high latitudes. The associated weakening of the stratospheric mean meridional circulation results in an upper stratospheric polar ozone deficit in early winter. This polar cap ozone deficit is strongest in the southern hemisphere and contributes to a polar vortex weakening in late winter, in concert with increased planetary wave forcing. In both hemispheres, the stratospheric polar vortex signal seems to migrate downwards into the troposphere and to the surface.

中文翻译：

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WACCM 模拟：中能电子降水对中层大气和对流层的十年冬季到春季气候影响

摘要 高能粒子降水是太阳影响大气成分和结构的主要过程之一。极地中层大气受到降水引起的一氧化氮 (NOx) 和氧化氢 (HOx) 的产生以及相关的臭氧 (O3) 损失的化学干扰，但其动力学的重要性仍存在争议。能够渗透到中间层的中能电子 (MEE) 的沉淀作用受到越来越多的关注，但直到最近才开始被纳入化学-气候模型。我们使用 NCAR 全大气社区气候模型 (WACCM) 通过在工业化前条件下进行两次理想化的集合实验，在有和没有 MEE 强迫的情况下研究 MEE 降水对气候的影响，在太阳活动周期 23 期间（仅完整日历年，1997-2007）。每个实验包括 20 个 11 年的合奏成员，总共 220 年。我们的结果表明，整个冬季对 MEE 的动态响应存在强烈的逐月变化。我们发现 12 月北半球极地涡旋加强，但信号在接下来的几个月里迅速衰减。由于平流层上层臭氧加热的纬向对称性增加，极地涡旋加强可能归因于行星波减少，最初由 MEE 诱导的 NOx 平流进入阳光照射区域引发。我们还在 6 月期间在南半球发现了类似的初冬极地涡旋加强。平均经向环流的变化伴随着这些异常的波浪强迫，导致高纬度地区动态诱发的垂直温度偶极子。平流层平均经向环流的相关减弱导致初冬平流层上层极地臭氧不足。这种极帽臭氧不足在南半球最强，并导致极地涡旋在晚冬减弱，同时行星波强迫增加。在两个半球，平流层极涡信号似乎都向下迁移到对流层和地表。与增加的行星波强迫相一致。在两个半球，平流层极涡信号似乎都向下迁移到对流层和地表。与增加的行星波强迫相一致。在两个半球，平流层极涡信号似乎都向下迁移到对流层和地表。