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

这项合作研究项目的目标将确定 并分析土地与环境之间的相互作用和反馈， 导致观察到的复杂性和缺乏 水文气候学的可预测性。 特别是，它旨在 研究土壤水分动态及其向干旱区的漂移， （干旱）和湿润（洪水）状态。 第一个假设是，局部循环的水分在 大陆尺度，和时间周期的顺序季节， 年导致土壤水分动态，可以描述为 带乘性噪声随机微分方程 的 这种非线性系统的解是 土壤水分至少有两种模式;也就是说，两个优选的 一个干，一个湿。 这与传统的 土壤水分分布的单峰视图。 这种分布 可以进行研究以获得诸如发病概率等答案 干旱期的结束，反之亦然。 另一 感兴趣的问题是干旱的持续时间。 多式 分布也可以是一个新的分类的基础， 气候区域。 第二个假设是，在时间尺度上， 单个事件的发生（即，周）土壤湿度 对大气动力学有延迟影响。 这种现象 由于水分供应以及动态影响 由于土壤湿度对地表温度的影响， 常压 这一假设的含义是 高度非线性时滞微分方程 土壤水分。 这个方程的解导致一个固定的 平衡，极限环与分叉或混沌。 这 将被用来研究季节性效应的放大， 像亚马逊这样的大陆地区， 土壤湿度和水文气候学的研究。 主要 来自亚利桑那大学的调查人员和工作人员以及 马萨诸塞州理工学院将就此展开合作 项目

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.