Linkages Between Large-scale and Mesoscale Dynamics, Land-atmosphere Interactions, and Convective Rainfall

首席研究员将研究中尺度陆地-大气相互作用的作用，包括它们受大尺度气象条件的控制和它们在大尺度上的总体影响。目标是确定尺度相互作用对美国大陆暖季对流降水的影响，重点关注土壤湿度和降雨之间的联系。潜在的假设是，尺度之间的非线性相互作用可能是重要反馈的来源，可能有助于控制陆地和大气的联合演化。方法方法是使用最先进的高分辨率陆地-大气耦合模拟系统来研究以下主要研究问题：o由大尺度动力学驱动的降水系统如何缩小到土壤湿度和地表通量的中尺度异质性，以及这种异质性在月至季节时间尺度上的演变情况？这种不断演变的中尺度地面非均质性是如何在更大尺度上影响对流云和降水的？这些中尺度效应对更大尺度区域的总体影响有多重要？我们能否识别大尺度和中尺度过程之间的反馈？o这些降尺度和升尺度过程和反馈作为天气动力系统的函数，在季节内是如何变化的？o这些降尺度和升尺度过程和反馈如何随水文状况（如干湿年）的变化而年际变化？这项调查的结果预计将有助于在从中尺度到天气尺度的空间尺度以及从小时到季节的时间尺度上对陆地-大气耦合有一个更统一的认识。更好地了解控制大陆降雨的因素对于管理水资源和规划与天气有关的紧急情况等应用至关重要。此外，估计由于大气成分变化和自然或人为土地覆盖变化的综合影响而引起的区域气候和水文变化，将需要改进模式中陆地-大气相互作用的表示。

The Principal Investigator will study the role of mesoscale land-atmosphere interactions - both their control by large-scale meteorological conditions and their aggregate impact at large scales. The goal is to determine the impact of the scale interactions on warm season convective precipitation in the continental U.S. with a focus on links between soil moisture and rainfall. The underlying hypothesis is that nonlinear interactions between scales may be a source of important feedbacks that might help control the joint evolution of the land and atmosphere. The methodological approach is to use a state-of-the-art, high-resolution, coupled land-atmosphere modeling system to investigate the following primary research questions:o How do precipitation systems driven by large-scale dynamics scale down to mesoscale heterogeneity in soil moisture and surface fluxes, and what is the evolution of this heterogeneity over monthly to seasonal timescales?o How does this evolving mesoscale surface heterogeneity scale up to influence convective clouds and precipitation at larger scales, and how important is the aggregate impact of these mesoscale effects over a larger-scale region?o Can we identify feedbacks between the large-scale and mesoscale processes? o How do these downscaling and upscaling processes and feedbacks vary intraseasonally, as a function of synoptic dynamical regime?o How do these downscaling and upscaling processes and feedbacks vary interannually, as a function of variations in hydrological regime (e.g., dry vs. wet years)?The results of this investigation are expected to contribute to a more unified picture of land-atmosphere coupling across spatial scales from mesoscale to synoptic, and across timescales from hourly to seasonal. Improved understanding of the factors that control continental rainfall is crucial for applications such as managing water resources and planning for weather-related emergencies. Furthermore, estimating changes in regional climate and hydrology resulting from the combined influence of changing atmospheric composition and natural or anthropogenic land cover change will require improved representations of land-atmosphere interactions in models.