Euro-Atlantic winter storminess and precipitation extremes under 1.5°C vs. 2°C warming scenarios
Euro-Atlantic winter storminess and precipitation extremes under 1.5°C vs. 2°C warming scenarios
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DOI：
10.5194/esd-9-679-2018
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发表时间：
2018-06-05
影响因子：
7.3
通讯作者：
Zahn, Matthias
中科院分区：
文献类型：
--
作者：
Barcikowska, Monika J.;Weaver, Scott J.;Zahn, Matthias
严重的冬季风暴加上极端降水对欧洲构成严重威胁。欧洲海岸线位于北大西洋风暴路径的东南出口，直接受到高风速、风暴洪水和海岸侵蚀的影响。在本研究中，我们分析了模拟冬季暴风雨和极端降水的潜在变化，这些变化可能在升温 1.5 或 2 摄氏度的情况下发生。在这里，我们重点关注 HAPPI 项目中执行的大气模型 CAM5 的第一个模拟套件，并评估水平模型分辨率的变化如何影响大气压力、风暴路径、风速和极端降水等结果。对不同分辨率的 CAM5 模拟进行比较表明，将水平分辨率提高到 0.25 度不仅可以细化区域尺度信息，还可以改善欧洲大西洋地区的大尺度大气环流特征。平均海平面和风场的月压力的纬向偏差（通常在低分辨率模型中发现）已大大减少。这使我们能够以更现实的方式分析区域到局地尺度的极端风速和降水的潜在变化。我们对2摄氏度变暖情景的未来响应的分析总体上证实了之前的模型模拟，表明欧洲-大西洋地区经向环流出现极地移动和加强。进一步的分析表明，这种转变主要发生在全球变暖超过1.5摄氏度之后，此时中纬度急流呈现出向东北方向增强的趋势。与此同时，风暴路径向东北移动使得亚速尔群岛高压增强并向东北扩展，导致比斯开湾和北海的降水量趋于减少。受中纬度急流加强影响的地区，如不列颠群岛、斯堪的纳维亚半岛和挪威海的西北海岸，以及纽芬兰以东的北大西洋上空，平均降水量、日降水量和次日降水量、极端风和风速均有所增加。暴风雨，表明这些地区风暴活动的增加对全球变暖产生了重要影响。
Severe winter storms in combination with precipitation extremes pose a serious threat to Europe. Located at the southeastern exit of the North Atlantic's storm track, European coastlines are directly exposed to impacts by high wind speeds, storm floods and coastal erosion. In this study we analyze potential changes in simulated winter storminess and extreme precipitation, which may occur under 1.5 or 2 degrees C warming scenarios. Here we focus on a first simulation suite of the atmospheric model CAM5 performed within the HAPPI project and evaluate how changes of the horizontal model resolution impact the results regarding atmospheric pressure, storm tracks, wind speed and precipitation extremes.The comparison of CAM5 simulations with different resolutions indicates that an increased horizontal resolution to 0.25 degrees not only refines regional-scale information but also improves large-scale atmospheric circulation features over the Euro-Atlantic region. The zonal bias in monthly pressure at mean sea level and wind fields, which is typically found in low-resolution models, is considerably reduced. This allows us to analyze potential changes in regional-to local-scale extreme wind speeds and precipitation in a more realistic way.Our analysis of the future response for the 2 degrees C warming scenario generally confirms previous model simulations suggesting a poleward shift and intensification of the meridional circulation in the Euro-Atlantic region. Additional analysis suggests that this shift occurs mainly after exceeding the 1.5 degrees C global warming level, when the midlatitude jet stream manifests a strengthening northeastward. At the same time, this northeastern shift of the storm tracks allows an intensification and northeastern expansion of the Azores high, leading to a tendency of less precipitation across the Bay of Biscay and North Sea.Regions impacted by the strengthening of the midlatitude jet, such as the northwestern coasts of the British Isles, Scandinavia and the Norwegian Sea, and over the North Atlantic east of Newfoundland, experience an increase in the mean as well as daily and sub-daily precipitation, wind extremes and storminess, suggesting an important influence of increasing storm activity in these regions in response to global warming.