Pollen concentrations on Alpine mountain tops are poorly known due to few observations and few modeling studies. We present two case studies from the Alps that provide insights into the spatial and temporal distribution of birch pollen. The numerical pollen dispersion model COSMO-ART (COnsortium for Small-scale MOdelling-Aerosols and Reactive Trace gases) was used to simulate the birch pollen transport during the 2017 pollen season. The model configuration included 1.1-km horizontal grid spacing and 80 vertical levels. The simulations were compared with daily pollen concentrations from two mountain tops in the Alps (Weissfluhjoch near Davos, Switzerland, at 2692 m and Schneefernerhaus, Germany, at 2650 m a.s.l.). In addition, the Swiss pollen stations at Davos (1587 m a.s.l.) and Buchs (446 m a.s.l.) were used. COSMO-ART simulations agreed well with the observations at Davos and Weissfluhjoch. At the Environmental Research Station Schneefernerhaus, the pollen concentrations were generally overestimated. We analyzed the pollen transport episode of 9 April 2017 at Weissfluhjoch in more detail using vertical cross sections of the COSMO-ART simulations. The results suggest that pollen can be lifted up to 3000 m in the morning hours and are subsequently transported by large-scale winds leading to higher birch pollen concentrations at Weissfluhjoch than at Davos. This suggests that the actual situation regarding sources, topography and wind determines the pollen distribution and not only altitude. Still, pollen levels at Weissfluhjoch are more than one order of magnitude lower than typical pollen levels at lowland Swiss stations such as Buchs.

中文翻译：

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复杂地形中的花粉预测：使用数值花粉预测模型 COSMO-ART 的阿尔卑斯山的两个案例研究

由于很少观察和建模研究，对高山山顶的花粉浓度知之甚少。我们展示了来自阿尔卑斯山的两个案例研究，它们提供了对桦树花粉的空间和时间分布的见解。数值花粉扩散模型 COSMO-ART（小型建模气溶胶和反应性微量气体联盟）用于模拟 2017 年花粉季节的桦树花粉运输。模型配置包括 1.1 公里的水平网格间距和 80 个垂直水平。模拟结果与阿尔卑斯山两个山顶（瑞士达沃斯附近的 Weissfluhjoch，海拔 2692 m 和德国 Schneefernerhaus，海拔 2650 m）的每日花粉浓度进行了比较。此外，还使用了位于达沃斯 (1587 m asl) 和 Buchs (446 m asl) 的瑞士花粉站。COSMO-ART 模拟与达沃斯和 Weissfluhjoch 的观察结果非常吻合。在环境研究站 Schneefernerhaus，花粉浓度普遍被高估。我们使用 COSMO-ART 模拟的垂直横截面更详细地分析了 2017 年 4 月 9 日在 Weissfluhjoch 的花粉传输事件。结果表明，花粉在早晨可以上升到 3000 米，随后被大风吹散，导致 Weissfluhjoch 的桦树花粉浓度高于达沃斯。这表明，来源、地形和风的实际情况决定了花粉的分布，而不仅仅是高度。尽管如此，Weissfluhjoch 的花粉水平仍比 Buchs 等低地瑞士站的典型花粉水平低一个数量级以上。