Abstract Extratropical cyclones of type Vb develop over the western Mediterranean and move north-eastward, leading to heavy precipitation over central Europe and posing a major natural hazard. Thus, this study aims at assessing their sensitivity to climate change and deepens the understanding of the underlying processes of Vb-type cyclones. The analysis is based on global climate model output, which is dynamically downscaled for extreme Vb cyclones. Thereby two periods are compared: the reference period 1979 to 2013, and the future period 2070 to 2099 under the representative concentration pathway RCP8.5. Additionally, we include the analysis from a large ensemble (LENS), where 25 ensemble members are analysed for the reference period 1990–2005 and the future period 2071–2080. The results show a reduction of Vb cyclones from 3.2 events per year during the reference period to only 2.1 Vb cyclones per year at the end of the 21st century. This result is supported by the LENS, which shows a significant reduction from 2.9 to 2.6 Vb events per year. This reduction is induced by a northward shift of cyclone track over Europe in the future. To gain insight into the impact of Vb cyclones, 10 Vb cyclones with the most intense precipitation over the Alps are selected and dynamically downscaled for each period, separately. Although the overall precipitation in the innermost domain stays the same in the two periods, results indicate that future Vb events tend to affect more strongly the eastern coasts of the Mediterranean Sea, while the impact in the Alpine region becomes slightly ameliorated compared to the current conditions. Furthermore, the dynamical downscaling exhibits an increased temperature contrast between the Mediterranean Sea and the European land for these 10 events in future. This contrast leads to a higher instability at coastal areas and thus explains the changed precipitation pattern.

中文翻译：

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气候变化对 Vb 气旋气候学的影响

摘要 Vb 型温带气旋在地中海西部发展并向东北移动，导致中欧强降水，构成重大自然灾害。因此，本研究旨在评估它们对气候变化的敏感性，并加深对 Vb 型气旋潜在过程的理解。该分析基于全球气候模型输出，该输出针对极端 Vb 气旋进行了动态缩减。因此比较了两个时期：参考时期 1979 至 2013 年，以及未来时期 2070 至 2099 年在代表性浓度路径 RCP8.5 下。此外，我们还包括来自大型集合 (LENS) 的分析，其中分析了 1990-2005 年参考期和未来 2071-2080 年期间的 25 个集合成员。结果显示 Vb 旋风分离器从 3 减少。参考期内每年发生 2 次事件，而 21 世纪末每年仅发生 2.1 Vb 气旋。这一结果得到了 LENS 的支持，表明每年的 Vb 事件从 2.9 显着减少到 2.6 Vb。这种减少是由未来欧洲上空的气旋轨道向北移动引起的。为了深入了解 Vb 气旋的影响，选择了阿尔卑斯山上降水最强烈的 10 个 Vb 气旋，并在每个时期分别动态缩小规模。尽管两个时期最内域的总体降水量保持不变，但结果表明，未来 Vb 事件对地中海东海岸的影响往往更强烈，而对高山地区的影响与当前情况相比略有改善. 此外，对于未来这 10 个事件，动态降尺度显示地中海和欧洲陆地之间的温度对比增加。这种对比导致沿海地区的不稳定性更高，从而解释了降水模式的变化。