Collaborative Research: P2C2--Cool and Warm Season Moisture Reconstruction and Modeling over North America

近2000个北美树木年轮年表网络是一个杰出的高分辨率古气候数据集，已被用于重建整个大陆的长期土壤水分平衡。然而，这些现有的重建代表了在年轮宽度年表中编码的不同季节气候信号的平均值，不能提供冬季和夏季条件的离散重建。古代干旱和潮湿时期的精确季节性需要明确，以提供对过去气候最真实的重建和对气候模式模拟最有用的约束。许多北美树木年轮年表编码了不同的季节气候信号，这些信号可用于单独重建该大陆大部分地区的冷季和暖季水分量。这项研究将使用数百个新的和现有的树木年轮年表来重建热带、亚热带和温带北美大部分地区的冷季和暖季水分水平。季节性重建将在两个固定时间段（公元1500年至今和公元1000年至今）每年以0.5°网格进行。它们将基于现有年表，重新测量现有树木年轮收集，以得出明确的早木和晚木宽度年表，并选择性地收集新的年表。不可能在任何地方单独进行冷暖季节的水分重建，但在北美热带和亚热带地区可能是最连续的，因为太平洋海面温度的气候强迫特别强烈，并且随纬度和季节变化。新的重建结果将与气候模式模拟结合使用，以检验有关北美冷暖季节气候的海洋-大气强迫、导致每一季节十年代际干旱和湿润期的气候动力学以及人为微量气体和陆地表面变化对季节性干旱和湿润期的影响的假设。重建和气候模拟还将用于确定现代十年极端干旱和潮湿时期的古代相似物。这项合作研究项目将涉及阿肯色大学、哥伦比亚大学的拉蒙特-多尔蒂地球天文台、孟菲斯大学和美国宇航局的戈达德空间研究所。该研究将提供目前尚不存在的冷暖季节水分异常的长时间、空间详细重建，但需要为北美气候变率的模式模拟提供更现实的季节约束。新的重建将具有重要的跨学科应用，为评估季节性极端气候对史前、殖民和现代时代的社会和生态变化的影响提供客观准确的年代框架。重建结果将在一个基于网络的界面上提供，该界面具有交互式分析功能，以尽可能广泛地利用季节性重建结果[北美季节性干旱地图集（NASDA）]。学生将获得真实的科学研究和出版的实地和实验室经验。该项目将支持一名早期职业科学家，将发起与美国宇航局科学家的新合作，并将加强与墨西哥森林研究局（墨西哥托雷昂）的长期合作。

The network of nearly 2,000 North American tree-ring chronologies is an outstanding high-resolution paleoclimate data set and has been used to reconstruct the long-term soil moisture balance across the continent. However, these existing reconstructions represent an average of the differing seasonal climate signals encoded in the annual ring width chronologies and do not provide discrete reconstructions of winter and summer conditions. The precise seasonality of ancient droughts and wet periods needs to be specified to provide the most realistic reconstructions of past climate and the most useful constraints for climate model simulations. Many North American tree-ring chronologies encode distinct seasonal climate signals that can be used for the separate reconstruction of cool and warm season moisture amounts over large sectors of the continent. The research will use hundreds of new and existing tree-ring chronologies to reconstruct both cool and warm season moisture levels across much of tropical, subtropical, and temperate North America. The seasonal reconstructions will be developed on a 0.5° grid for every year during two fixed time periods: AD 1500-present and AD 1000-present. They will be based on existing chronologies, re-measurements of existing tree-ring collections to derive seasonally explicit earlywood and latewood width chronologies, and selective field collections of new chronologies. Separate cool and warm season moisture reconstructions will not be possible everywhere, but are likely to be most continuous over tropical and subtropical North America where climate forcing from Pacific sea surface temperatures is particularly strong and changes sign with latitude and season. The new reconstructions will be used with climate model simulations to test hypotheses concerning the ocean-atmospheric forcing of cool and warm season climate over North America, the climate dynamics responsible for decadal droughts and wet periods in each season, and the influence of anthropogenic trace gas and land surface changes on seasonal droughts and wet periods. The reconstructions and climate simulations will also be used to identify ancient analogues for the extreme decadal droughts and wet periods witnessed during the modern era. This collaborative research project will involve the University of Arkansas, Lamont-Doherty Earth Observatory of Columbia University, the University of Memphis, and NASA's Goddard Institute for Space Studies. The research will provide the long, spatially detailed reconstructions of cool and warm season moisture anomalies that currently do not exist but are needed to provide more realistic seasonal constraints on model simulations of North American climate variability. The new reconstructions will have major interdisciplinary applications by providing an objective exactly dated framework for evaluating the impacts of seasonal climate extremes on social and ecological change during the prehistoric, colonial, and modern eras. The reconstructions will be served on a web-based interface with interactive analytical capabilities to leverage the widest possible use of the seasonal reconstructions [the North American Seasonal Drought Atlas (NASDA)]. Students will be provided with authentic field and laboratory experience in scientific research and publication. This project will support an early career scientist, will initiate a new collaboration with NASA scientists, and will strengthen a long-term collaboration with the Mexican Forest Research Service (INIFAP, Torreon, Mexico).