Collaborative Research: Improving Process-Level Understanding of Surface-Atmosphere Interactions Leading to Convection Initiation in the Central United States

土壤水分对气候系统很重要，因为它控制着蒸发、蒸腾和能量从陆地到大气的运动。通过这些机制，土壤湿度可以在每日到季节的时间尺度上影响降水的时间和强度。然而，关于土壤水分-降水反馈的标志、强度和总体重要性，目前还缺乏科学共识。这个项目将增进我们对美国中部暖季(5月至9月)对流启动和降水的重要陆地和大气过程的了解。从该项目中获得的知识将用于提高业务天气和气候模型中模拟的准确性。该项目将为本科生、研究生和博士后研究人员提供研究、科学交流和公共活动方面的培训。该项目将使用一个耦合的观测-模拟框架来评估美国中部土壤水分对对流降水反馈的性质和强度，以检查土壤和边界层大气之间的物理过程。该项目的目标是：(1)评估美国中部的对流是否优先于潮湿或干燥的土壤；(2)使用基于过程的度量和高质量的土地和大气观测来量化土壤湿度对对流和降水的影响；以及(3)使用天气研究和预报(WRF)模型来评估对流和降水对土壤水分条件变化的响应。该项目将利用国家协调土壤湿度监测网的土壤湿度观测数据和雷神算法确定的数十万次对流事件。这种现场观测和对流事件的巨大样本量相结合，为评估土壤水分-降水反馈提供了前所未有的机会。这项研究的结果将导致天气和气候模式中使用的参数化方案的改进。这项研究侧重于拥有最密集的地表和边界层观测的地区，但对陆地-大气相互作用及其在调节气候中的作用的基于过程的理解很容易转移到世界其他地区。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Soil moisture is important for the climate system because it controls evaporation, transpiration, and energy movement from the land to the atmosphere. Through these mechanisms, soil moisture can influence the timing and intensity of precipitation at daily to seasonal timescales. However, there is a lack of scientific consensus on the sign, strength, and overall importance of soil moisture-precipitation feedbacks. This project will improve our understanding of the land and atmosphere processes that are important to convection initiation and precipitation during the warm season (May to September) in the central United States. The knowledge gained from this project will be used to improve the accuracy of simulations in operational weather and climate models. The project will provide undergraduate students, a graduate student, and postdoctoral researchers with training in research, science communication, and public outreach.This project will assess the nature and strength of soil moisture feedbacks on convective precipitation in the central United States using a coupled observation-modeling framework to examine the physical processes linking the soil and boundary layer atmosphere. The objectives of the project are to: (1) evaluate whether convection occurs preferentially over wet or dry soils in the central United States, (2) quantify the influence of soil moisture on convection and precipitation using process-based metrics and high quality land and atmosphere observations, and (3) evaluate the response of convection and precipitation to changes in soil moisture conditions using the Weather Research and Forecast (WRF) model. This project will utilize soil moisture observations from the National Coordinated Soil Moisture Monitoring Network and hundreds of thousands of convection events identified by the ThOR algorithm. This combination of in situ observations and the immense sample size of convective events provides an unprecedented opportunity to evaluate soil moisture – precipitation feedbacks. The results of this study will lead to improvements in the parameterization schemes that are used in weather and climate models. This study focuses on a region that has the densest land-surface and boundary layer observations, but the process-based understanding of land-atmosphere interactions and their role in modulating the climate is readily transferable to other regions around the world.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.