Collaborative Proposal: The Role of Arctic Amplification in Modifying Mid-latitude Atmospheric Circulation and Promoting Extreme Weather Events

合作提案：北极放大在改变中纬度大气环流和促进极端天气事件中的作用

• 批准号: 1304398
• 负责人: Stephen Vavrus
• 金额: $ 38.09万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1304398&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Role; Arctic; Amplification

Intellectual Merit: recent work has suggested and demonstrated a mechanism connecting Arctic Amplification (AA ? enhanced Arctic warming) with an increased probability of extreme weather events in northern hemisphere mid-latitudes, as well as a feedback to arctic wind patterns that drive further ice loss. This study will extend this work using output from reanalyses, model simulations from the CMIP5 archive, and experimental CESM model runs to investigate how and why the ongoing loss of arctic sea ice and high-latitude terrestrial snow cover may cause mid-latitude weather patterns to change. Past and projected patterns in 500 hPa heights will be analyzed using a combination of Self-Organizing Maps (SOMs) ? a neural-network-based technique that reduces large data sets to their representative patterns ? a new meridional circulation index, and an extreme weather index to address the hypothesis that Arctic Amplification of past and future global climate change promotes circulation patterns that favor extreme weather events in middle latitudes of the northern hemisphere. The PIs suggest that changes in the energy budget of the arctic surface, because of sea-ice loss and earlier snow melt on high-latitude land, reduce meridional thickness gradients, which induce generally weaker zonal flow aloft and higher amplitude circulation features. They think these upper-level flow patterns slow the eastward progression of large-scale atmospheric Rossby waves, favoring more persistent weather conditions that increase the probability of extreme weather such as cold-air outbreaks, heat waves, droughts, and heavy precipitation. They believe the primary physical mechanism driving the change is an enhanced and seasonally varying arctic heating: in fall/winter it is ocean-based associated with substantial sea ice loss, while in warmer months it is land-based due primarily to earlier snow melt and reduced soil moisture. Higher-amplitude flow trajectories may also exacerbate sea-ice and snow-cover loss, thereby constituting a positive feedback loop.Because extreme weather events, such as temperature and precipitation extremes, are often caused by high-amplitude, slow-moving upper-level circulation patterns, this analysis will focus on detecting and characterizing these patterns, interpreting the weather conditions associated with them, and identifying regions that are likely to be affected. This study attempts to connect arctic change with the rest of the global climate system.Broader Impacts: Changes in extreme weather as a result of greenhouse gas accumulation will directly and dramatically affect millions of people across the globe, thus a better understanding and more accurate future projection of changes in the frequency, location, and severity of droughts, floods, and temperature extremes are urgently needed by decision-makers at all levels of society. Preliminary work has already attracted world-wide attention via articles in prominent newspapers, radio interviews, interviews for the Weather Channel, magazine articles, and numerous online blogs. This will also be an opportunity for a new post-doc. The PIs will prepare a module for the NSF-supported ?Beyond Penguins and Polar Bears? project for K-5 teachers. Both PIs make frequent public and school presentations on climate-change related issues, and because extreme weather is so relevant to society at large, results from the proposed study will figure prominently into these presentations.

学术价值：最近的工作提出并证明了一种机制，将北极放大（AA？增强的北极变暖）与北半球中纬度地区极端天气事件的可能性增加联系起来，以及对导致进一步冰损失的北极风模式的反馈。这项研究将利用再分析的结果、CMIP5 档案的模型模拟和实验性 CESM 模型运行来扩展这项工作，以研究北极海冰和高纬度陆地积雪的持续消失如何以及为何可能导致中纬度天气模式发生变化。改变。将使用自组织地图 (SOM) 的组合来分析 500 hPa 高度的过去和预测模式 ?一种基于神经网络的技术，可将大型数据集简化为其代表性模式？一个新的经向环流指数和一个极端天气指数，旨在解决北极对过去和未来全球气候变化的放大促进了有利于北半球中纬度地区极端天气事件的环流模式的假设。 PI表明，由于海冰消失和高纬度陆地上积雪提前融化，北极表面能量收支的变化减少了经向厚度梯度，从而导致高空纬向流普遍较弱，环流特征较高。他们认为这些高层流动模式减缓了大规模大气罗斯贝波向东的进展，有利于更持久的天气条件，增加了冷空气爆发、热浪、干旱和强降水等极端天气的可能性。他们认为，推动这一变化的主要物理机制是北极变暖的增强和季节性变化：在秋季/冬季，它是基于海洋的，与大量海冰损失有关，而在温暖的月份，它是基于陆地的，主要是由于较早的雪融化和土壤湿度降低。较高振幅的流动轨迹还可能加剧海冰和积雪的损失，从而构成正反馈循环。因为极端天气事件，如极端气温和降水，往往是由高振幅、缓慢移动的上层造成的。环流模式，该分析将侧重于检测和表征这些模式，解释与其相关的天气条件，并确定可能受到影响的区域。这项研究试图将北极变化与全球气候系统的其他部分联系起来。 更广泛的影响：温室气体积累导致的极端天气变化将直接、巨大地影响全球数百万人，从而更好地理解和更准确的未来社会各阶层的决策者迫切需要预测干旱、洪水和极端气温的频率、地点和严重程度的变化。初步工作已经通过著名报纸上的文章、电台采访、天气频道采访、杂志文章和众多在线博客吸引了全世界的关注。这也将是新博士后的机会。 PI 将为 NSF 支持的“超越企鹅和北极熊”准备一个模块。 K-5 教师项目。两位 PI 经常就气候变化相关问题向公众和学校发表演讲，并且由于极端天气与整个社会息息相关，因此拟议研究的结果将在这些演讲中占据重要地位。