Collaborative Research: P2C2--Inferring Spatio-Temporal Variations in the Risk of Extreme Precipitation in the Western United States from Tree Ring Chronologies

该项目旨在通过分析美国西部海岸和内陆树木年轮记录的湿度异常，了解美国西海岸极端寒冷季节的降水动态。沿海地区总降水量高的冬季以少量极端风暴为标志，这些极端风暴在沿海和更远的内陆表现出明显的降水空间模式。这项研究将以这一观察为基础，力求开发树枝气候证据的新应用，以探索下列问题：a)极端降水变异性如何用树轮年表网络来表示；b)这些信息是否能够深入了解导致这些极端事件的风暴路径的时空变异性；以及c)如何对极端降水和风暴路径的联合变异性进行模拟，以便对两者进行一致的、百年来的重建。社会利用针对历史极端降水量变化而设计的风险缓解战略(例如基础设施、保险)来管理这一负担，这种变化是根据相对较短的工具记录估计的，并可能在人为气候变化的影响下发生变化。该项目将有助于确定这些影响的频率、持续性、重复性和地理模式在过去在自然气候多变的情况下发生了怎样的变化。这将为这些转变的原因和未来的可预测性提供重要的见解。该项目还为研究生和博士后研究人员提供支持。推广工作将集中在与洛杉矶县防洪区、美国陆军工程兵部队和管理该地区极端事件风险的相关机构的高层讨论上。这种直接接触将加强研究产品的应用，并为其设计提供指导。研究成果的创新可视化将通过哥伦比亚水中心提供给公众使用。

This project aims to understand extreme cold-season precipitation dynamics along the west coast of the United States through an analysis of the moisture anomalies recorded by tree-ring chronologies across the coast and interior of the western U.S. Winters with high total precipitation amounts in the coastal regions are marked by a small number of extreme storms that exhibit distinct spatial patterns of precipitation across the coast and further inland. Building from this observation, this research will seek to develop a novel application of dendroclimatic evidence to explore the following questions: a) how is extreme precipitation variability expressed in a network of tree-ring chronologies; b) can this information provide insight on the space-time variability of storm tracks that cause these extreme events; and c) how can the joint variability of extreme precipitation and storm tracks be modeled to develop consistent, multi-centennial reconstructions of both.The broader impacts include the potential to better understand extreme precipitation events which exert significant social costs through both loss of life and substantial damage to property. Society manages this burden using risk mitigation strategies (e.g., infrastructure, insurance) designed for historic extreme precipitation variability that is estimated from relatively short instrumental records and may be changing under anthropogenic climate change. This project will help determine how the frequency, persistence, recurrence and geographic pattern of these impacts have varied in the past under natural climate variability. This will provide important insights into the causes of these shifts and the potential for predictability in the future. This project also provides support for graduate and post-doctoral researchers.Outreach efforts will focus on high-level discussions with the L.A. County Flood Control District, U.S. Army Corps of Engineers, and related agencies that manage extreme event risk in the region. This direct engagement will enhance the application of the research products, as well as provide guidance for their design. Innovative visualizations of research output will be made available through the Columbia Water Center for public use.