Doctoral Dissertation Research: Understanding the Climate Mechanisms Associated with Past Drought and Vegetation Change.

摘要本博士论文研究项目将利用现代气候模拟技术研究与美国西部干旱相关的天气和动态气候过程，以及生态系统对过去特大干旱的可能响应。该博士生将为植物对过去水文气候变化和干扰的反应如何帮助保护和减轻生态群落免受未来环境变化的影响提供新的见解。对与现代干旱相关的气候过程的理解，将提供对过去干旱变化的更深入的了解，以及导致古生态记录中明显的特大干旱的机制。该学生将与当地社区和政府机构密切合作，为资源管理者提供有关过去水文气候变化及其对宝贵自然资源影响的有用知识。此外，对与过去特大干旱相关的生物多样性动态的新见解将为有关生态可持续性和土地管理问题的政策相关讨论提供信息。这项研究的结果将有广泛的用途，包括物种范围建模，预测未来生态系统对未来气候变化的迁移模式，以及某些生态系统的火灾管理。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。了解与过去干旱和潮湿时期有关的自然变率的范围对于为水资源管理者提供未来水资源规划的背景非常重要。该博士生的论文研究将得到该奖项的支持，他将使用过去干湿事件的现代气候数据作为沉积记录中所见事件的类比。该项目将重点关注两个核心问题：(1)在距今4200年左右的大干旱期间，北美西部主要的季节性大气环流模式和地表条件是什么？(2)在特大干旱之后的潮湿事件中，北美西部主要的季节性大气环流模式是什么？为了确定可能导致美国西部这两个事件的天气和动力模式，学生将应用现代气候模拟技术，这是一个概念模型，使用现代极端事件作为过去事件的类似物。为了实现这一目标，将对选定的现代气候模拟案例年的异常值组合进行制图和分析，以确定其地表和大气条件的时空变异性。

NATIONAL SCIENCE FOUNDATIONGEOGRAPHY SPATIAL SCIENCES (GSS) PROGRAMABSTRACTThis doctoral dissertation research project will use the modern climate analog technique to investigate the synoptic and dynamic climate processes associated with drought in the western U.S. and the possible responses of ecosystems to past megadroughts. The doctoral student will provide new insights into how vegetative responses to past hydroclimate variability and disturbances can help protect and mitigate ecological communities against future environmental change. An understanding of the climate processes associated with modern drought will provide deeper insights into past drought variability and the mechanisms that caused megadroughts evident in paleoecological records. The student will work closely with local communities and government agencies by providing useful knowledge to resource managers regarding past hydroclimate variability and impacts to valuable natural resources. In addition, the new insights into biodiversity dynamics associated with past megadroughts will inform policy-related discussions regarding ecological sustainability and land-management issues. Results from this research would be useful for a broad range of uses, including species range modeling, predicting future ecosystem migration patterns in response to future climate change, and fire management in certain ecosystems. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.Understanding the range of natural variability related to past drought and wet periods is important for providing context to water resource managers for future water planning. The doctoral student whose dissertation research will be supported by this award will use modern climate data during past dry and wet events as analogs for the events seen in the sedimentary record. The project will focus on two core questions: (1) What were the prevailing seasonal atmospheric circulation patterns and surface conditions over western North America during the megadrought centered around 4,200 years BP? (2) What were the prevailing seasonal atmospheric circulation patterns over western North America during the wet event that followed the megadrought? In order to identify possible synoptic and dynamic patterns that may have caused these two events in the western U.S., the student will apply a modern climate analog technique, which is a conceptual model that uses modern extremes as analogs of past events. To accomplish this, a composite of anomaly values for selected modern climate analog case years will be mapped and analyzed for their spatiotemporal variability of surface and atmospheric conditions.