Doctoral Dissertation Research: Analysis of Decadal Moisture Anomalies over North America: 1700-1979

博士论文研究：北美年代际湿度异常分析：1700-1979

• 批准号: 0101245
• 负责人: David Stahle
• 金额: $ 0.78万
• 依托单位: University of Arkansas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-04-01 至 2003-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0101245&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Analysis; Decadal

Recent research on the complex interactions among ocean, atmosphere, and terrestrial systems have highlighted the need for more complete understanding of the processes that influence climatic variability at seasonal, annual, and decadal time scales. Once facet of vulnerability that has special significance for many different sectors of society is the tendency for longer-term dry and wet spells, which can have critical impacts because of the absence or overabundance of precipitation. This doctoral dissertation research project will analyze the spatial and temporal variation and forcing of natural modes of drought and wet spells over the U.S. and northern Mexico. Analyses will focus on the regional spatial scale and decadal to century time scales. Instrumental and tree-ring-reconstructed Palmer Drought Severity Index (PDSI) data sets are available as June-July-August means covering the U.S. for cells measuring 2 degrees of latitude by 3 degrees of longitude, with the instrumental data extending over the period from 1895 to1995 period while the dendroclimatological data cover the period from 1700 to 1979. The reconstructed data set will be expanded in this study with new tree-ring chronologies over northern Mexico. The overall goal of this study is to better understand how moisture anomalies vary spatially and temporally and what factors within the natural variation of earth's climate system cause them to occur. The project's first objective is a description of the spatial and temporal characteristics of well-known epic droughts and wet spells during the 20th century. Potential analogs to these epic events and their spatial position, progression, and severity will be characterized from the long tree-ring reconstructed PDSI data set and historical evidence in the literature. Animations of PDSI map sequences will help analyze drought/wet spell progression and dissipation. Studies of factors that lead to or "force" droughts/wet spells will include examination of the effects of solar insolation variation, Pacific sea surface temperatures, and indices like the Pacific/North American Pattern, Pacific Decadal Oscillation, Southern Oscillation, North Atlantic Oscillation, and Arctic Oscillation on the position, duration, and intensity of drought/wet spells. Methods used for these "forcing" analyses will be the mapping of composite sea surface temperatures and correlation statistics obtained from pair-wise comparisons between the forcing time series and individual grid point PDSI time series. The possible link between moisture anomalies and various forcing factorswill also be assessed and plotted using t-tests and spectral analyses.This research project should result in a better understanding of the geographical positioning, timing, progression, intensity, and causes of long-duration drought and wet periods in the U.S. and northern Mexico. The focus will be on long-term drought and wet periods because of the enormous impact they have had on the environment and society. Examples are the 1930s epic drought and the wet periods of the early 1900s and the early 1990s. These events are not unprecedented in the climate history of the U.S., however. Based on a 300-plus-year record of U.S. moisture anomalies reconstructed from tree-rings, recurring long duration drought/wet periods will be identified and characterized. Causal mechanisms such as variations in solar irradiation and sea surface temperature will then be statistically associated with these recurring moisture anomalies to identify common causes. The expected result is an improved understanding of the timing, position, and severity of drought and wet spells associated with certain forcing or causal mechanisms. This is expected to lead to improved forecasts of drought/wet spells and provide valuable insight and data for continued research into these profound climatic anomalies. 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.

关于海洋，大气和陆地系统之间复杂相互作用的最新研究强调了对影响季节，年和十年时间尺度上影响气候变化的过程的完全了解。 曾经对社会许多不同部门具有特殊意义的脆弱性方面是长期干和湿法的趋势，由于缺乏或过度降水，这可能会产生关键的影响。 该博士学位论文研究项目将分析美国和墨西哥北部的干旱和湿法自然模式的空间和时间变化。 分析将集中在区域空间量表上，并将其十年时间尺度纳入。 工具性和树木环的帕尔默干旱严重程度指数（PDSI）数据集可作为6月至7月 - 8月份意味着覆盖美国的细胞，这些细胞测量2度的延长度乘以3度，工具性数据在1895年的期间内延长至1995年，该期间从12995年期间延伸到1799年度，该数据涵盖了1799年的时间表。在墨西哥北部的新树环按年表。 这项研究的总体目标是更好地了解水分异常在空间和时间上如何变化，以及地球气候系统自然变化中的哪些因素导致它们发生。 该项目的第一个目标是描述20世纪众所周知的史诗干旱和湿法的时空特征。 对这些史诗事件的潜在类似物及其空间位置，进展和严重程度将以文献中的长树环重建的PDSI数据集和历史证据来表征。 PDSI地图序列的动画将有助于分析干旱/湿法的进度和耗散。 研究导致或“力量”干旱/湿法的因素的研究将包括检查太阳能破裂变化的影响，太平洋海面温度以及诸如太平洋/北美模式，太平洋衰老振荡，南部振荡，北大西洋振荡和北大西洋振荡和北极振荡的位置振荡和drationd draughts draints offeration drainds of draints offeration occillation oscill和Pacific offication。 用于这些“强迫”分析的方法将是复合海面温度的映射以及通过强迫时间序列与单个网格点PDSI时间序列之间的成对比较获得的相关统计。 还会使用t检验和光谱分析来评估和绘制水分异常与各种强迫因子之间的可能联系。这项研究项目应更好地了解美国和墨西哥墨西哥墨西哥的长期干旱和长期干旱和长期干旱和潮湿的地理位置，时机，进展，强度以及长期干旱和潮湿的原因。 由于他们对环境和社会的巨大影响，重点将放在长期干旱和潮湿时期。 例子是1930年代的史诗般的干旱以及1900年代初和1990年代初期的潮湿时期。 但是，在美国气候历史上，这些事件并不是前所未有的。 根据从树木中重建的美国水分异常的300多年记录，将确定和表征经常出现的长时间干旱/潮湿时期。 在统计上，与这些反复出现的水分异常相关的因果机制，例如太阳照射和海面温度的变化，以识别常见原因。 预期的结果是对与某些强迫或因果机制相关的干旱和湿法的时机，位置和严重程度的理解得到了改进。 预计这将改善对干旱/湿法的预测，并为对这些深刻气候异常的持续研究提供宝贵的见解和数据。 作为博士学位论文研究改进奖，该奖项还将提供支持，使有前途的学生能够建立强大的独立研究职业。