COLLABORATIVE RESEARCH: Nonlinear Dynamics of Soil Moisture Climate at Continental Scales: The Climatic Origins of Droughts

合作研究：大陆尺度土壤湿度气候的非线性动力学：干旱的气候起源

• 批准号: 9120367
• 负责人: Dara Entekhabi
• 金额: --
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-09-01 至 1991-10-01
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9120367&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Nonlinear; Dynamics; Soil

The goal of this collaborative research project will identify and analyze the interactions and feedbacks between the land and atmosphere that result in observed complexities and lack of predictability of hydroclimatology. In particular, it is intended to study the dynamics of soil moisture and its excursions into dry (drought) and wet (flood) states. The first hypothesis is that local recycling of moisture at continental scales, and time periods on the order of seasons to years leads to soil moisture dynamics that can be described by a stochastic differential equation with multiplicative noise. The solution to such nonlinear system is a probability distribution of soil moisture with at least two modes; that is, two preferred states, one dry and one wet. This contrasts with the traditional unimodal view of the soil moisture distribution. This distribution can be studied to obtain answers like the probability of the onset of drought or vice versa the end of a drought period. Another question of interest is the duration of droughts. The multimodal distribution can also be the basis of a new classification of climatic regions. The second hypothesis is that at time scales on the order of the occurrence of individual events (i.e., weeks) the soil moisture has a delayed effect on atmospheric dynamics. This phenomena is due to the moisture supply as well as to dynamic influences resulting from soil moisture effect on surface temperature and atmospheric pressure. The implication of this hypothesis is a highly nonlinear delayed differential equation for the description of soil moisture. The solution of this equation leads to a fixed equilibrium, a limit cycle with bifurcations or to chaos. This will be used to study amplification of seasonal effects over continental regions like the Amazonia as well as the predictability of soil moisture and hydroclimatology in general. Principal Investigators and staff from the University of Arizona and the Massachusetts Institute of Technology will collaborate on this project.

该合作研究项目的目标将确定并分析陆地和大气之间的相互作用和反馈，这些相互作用和反馈导致观察到的复杂性和水文气候学缺乏可预测性。 特别是，它的目的是研究土壤湿度的动态及其向干燥（干旱）和潮湿（洪水）状态的变化。 第一个假设是大陆尺度上水分的局部循环以及季节到年份的时间段导致土壤水分动态，可以通过带有乘性噪声的随机微分方程来描述。 这种非线性系统的解是具有至少两种模式的土壤湿度的概率分布；即，两种优选状态，一种干燥，一种潮湿。 这与土壤湿度分布的传统单峰视图形成对比。 可以研究这种分布以获得诸如干旱开始的概率或干旱期结束的概率等答案。 另一个令人感兴趣的问题是干旱的持续时间。 多峰分布也可以作为气候区新分类的基础。 第二个假设是，在单个事件发生顺序的时间尺度（即几周），土壤湿度对大气动态有延迟影响。 这种现象是由于水分供应以及土壤水分对地表温度和大气压力的动态影响造成的。 该假设的含义是用于描述土壤湿度的高度非线性延迟微分方程。 该方程的解导致固定平衡、具有分岔的极限环或混沌。 这将用于研究亚马逊等大陆地区季节性影响的放大以及土壤湿度和水文气候学的总体可预测性。 亚利桑那大学和麻省理工学院的首席研究员和工作人员将在该项目上进行合作。