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

由近2 000个北美树木年轮年表组成的网络是一个出色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编码在年轮宽度年表中的不同季节气候信号的平均值，并没有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具体说明，以提供最真实的过去气候重建和气候模式模拟最有用的约束。 许多北美树木年轮年表编码不同的季节性气候信号，可用于单独重建大陆大部分地区的冷季和暖季湿度。 该研究将使用数百个新的和现有的树木年轮年表来重建北美热带，亚热带和温带大部分地区的冷季和暖季湿度水平。 季节性重建将在两个固定的时间段内每年在0.5°网格上进行：AD 1500-现在和AD 1000-现在。 他们将根据现有的年表，重新测量现有的树木年轮收集，以获得季节性明确的早材和晚材宽度年表，并选择新的年表现场收集。 单独的冷季和暖季湿度重建不可能在任何地方都是可能的，但在热带和亚热带北美地区可能是最连续的，那里太平洋海面温度的气候强迫特别强，并随纬度和季节而变化。新的重建将与气候模式模拟一起使用，以测试有关北美冷暖季节气候的海洋-大气强迫、每个季节十年干旱和湿润期的气候动力学以及人为痕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所目睹的极端十年干旱和潮湿时期的古代类似物。 这项合作研究项目将涉及阿肯色州大学、哥伦比亚大学的拉蒙特-多尔蒂地球观测站、孟菲斯大学和美国宇航局的戈达德空间研究所。 这项研究将提供长期的，空间上详细的重建，目前还不存在，但需要提供更现实的季节性限制模型模拟北美气候变率的冷暖季节水分异常。新的重建将有重大的跨学科应用，提供一个客观的准确日期的框架，以评估在史前，殖民地和现代时期的社会和生态变化的季节性气候极端的影响。 将在一个具有互动分析能力的网络界面上提供重建数据，以尽可能广泛地利用季节性重建数据[北美季节性干旱地图集（日本宇宙开发厅）]。 学生将在科学研究和出版方面获得真实的实地和实验室经验。 该项目将支持一名早期职业科学家，将发起与美国航天局科学家的新的合作，并将加强与墨西哥森林研究处（INIFAP，墨西哥托雷翁）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).