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-既包括大尺度气象条件对它们的控制，也包括它们在大尺度上的综合影响。 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，重点是土壤水分和降雨之间的联系。 基本的假设是，尺度之间的非线性相互作用可能是重要的反馈源，可能有助于控制土地和大气的联合演变。 方法的方法是使用一个国家的最先进的，高分辨率，耦合陆-气模拟系统，调查以下主要研究问题：o如何降水系统驱动的大尺度动力学尺度下到中尺度异质性土壤水分和地表通量，这种异质性的演变是什么在每月到季节的时间尺度？这种不断演变的中尺度表面异质性如何扩大到影响更大尺度的对流云和降水，以及这些中尺度效应在更大尺度区域的综合影响有多重要？o我们能否识别大尺度和中尺度过程之间的反馈？ 作为天气动力系统的一个函数，这些尺度缩减和尺度放大过程和反馈在季节内是如何变化的？这些尺度缩小和尺度扩大的过程和反馈是如何作为水文状况变化的函数逐年变化的（例如，干与湿年份）？这项调查的结果，预计将有助于一个更统一的图片的陆-气耦合跨空间尺度从中尺度到天气，跨时间尺度从每小时到季节。 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，要估计大气成分变化和自然或人为土地覆盖变化的综合影响所造成的区域气候和水文变化，就需要改进模型中陆地-大气相互作用的表述。

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.