RII Track-4: Turbulence Effects on Cloud Microphysical Processes: Development and Testing of Subgrid-Scale Parameterizations for Large Eddy Simulation

云对地球系统中的许多过程起着关键作用，包括降水、大气化学和气候。在过去的几十年里，科学家们已经证明，云中的湍流会导致湿度、温度和水滴浓度的大幅波动，这直接影响云的寿命和降雨形成。尽管小尺度云湍流很重要，但很少有研究关注如何在用于研究和天气预报的计算机模型中表示其影响。在这个项目中，首席调查员(PI)将与密歇根理工大学(MTU)的专家合作开发模型，在计算机模型中准确地表示小尺度云湍流的影响。为了实现这一目标，PI和一名研究生将在MTU云室进行实验室实验，这是美国唯一能够在受控实验室环境中创造和维持湍流云的湍流室。这笔资金将在国际和平研究所和东道国之间建立持久的合作关系，并将通过提供独特的实验室设施来支持研究生的教育。通过将PI的专业知识扩展到包括实验室实验和云湍流，该项目将使PI与国家天气中心合作伙伴之间的未来合作成为可能，从而增强俄克拉荷马州中部气象企业的整体竞争力。湍流是云混合和夹带的关键驱动因素，导致温度、湿度、云颗粒浓度以及碰撞或解体的显著波动。最近的研究表明，过饱和度的湍流波动可以导致云滴尺寸分布的加宽，启动降雨形成的速度比理论预测的静止环境快得多。随着计算能力的提高，直接解析最大尺度湍流的大涡模拟(LES)正成为天气预报和研究湍流、微物理和大尺度云特性之间联系的一种很有前途的技术。该项目旨在发展新的亚网格尺度模式，能够准确地表示大涡模拟系统中过饱和的小尺度湍流起伏。PI和一名研究生将与密歇根理工大学的东道主合作，在MTU云室进行实验，在那里，通过潮湿的瑞利-贝纳德对流可以产生稳定的湍流云。将进行一系列实验室实验，以研究过饱和波动在空间和时间尺度上的分布，并开发新的模型，仅基于流动的分辨尺度特征，就可以恢复次网格过饱和度方差。该项目将使PI能够发展实验室实验和云层湍流方面的研究专长，从而使未来能够与国家天气中心的合作伙伴进行合作。该项目带来的未来研究领域具有显著的社会效益，包括改进的降水预报和雷达测量，以及更好地了解云在地球目前和气候中的作用。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。

Clouds play a critical role for many processes in the Earth system, including precipitation, atmospheric chemistry, and climate. Over the past few decades, scientists have shown that turbulence within clouds can cause large fluctuations in humidity, temperature, and water droplet concentrations, which directly impact cloud lifetimes and rain formation. Despite the importance of small-scale cloud turbulence, few studies have focused on how to represent its effects in computer models used for research and weather forecasting. In this project, the Principal Investigator (PI) will partner with experts at Michigan Technological University (MTU) to develop models that accurately represent the effects of small-scale cloud turbulence in computer models. In order to achieve this goal, the PI and a graduate student will perform laboratory experiments in the MTU cloud chamber, the nation's only turbulence chamber capable of creating and sustaining turbulent clouds in a controlled laboratory environment. This funding will establish a lasting collaboration between the PI and hosts and will support the education of a graduate student by providing access to unique laboratory facilities. By expanding the PI's expertise to encompass laboratory experiments and cloud turbulence, this project will enable future collaborations between the PI and partners in the National Weather Center, thereby strengthening the overall competitiveness of the Central Oklahoma weather enterprise.Turbulence is a key driver of cloud mixing and entrainment, causing significant fluctuations in temperature, humidity, cloud particle concentrations, and collisions or breakup. Recent studies have demonstrated that turbulent fluctuations of supersaturation can lead to a broadening of the cloud droplet size distribution, initiating rain formation significantly faster than what theory predicts for a quiescent environment. As computational power increases, large eddy simulation (LES), which directly resolves the largest scales of turbulence, is becoming a promising technique for both weather forecasting and for studying the linkages between turbulence, microphysics, and large-scale cloud properties. This project aims to develop new subgrid-scale models that can accurately represent small-scale turbulent fluctuations of supersaturation in LES. The PI and a graduate student will partner with hosts at Michigan Technological University to perform experiments in the MTU cloud chamber, where steady-state turbulent clouds can be produced through moist Rayleigh-Benard convection. An ensemble of laboratory experiments will be performed to investigate the distribution of supersaturation fluctuations across spatial and temporal scales, and to develop new models that can recover the subgrid supersaturation variance based only on knowledge of resolved-scale features of the flow. This project will allow the PI to develop research expertise in laboratory experiments and cloud turbulence, thereby enabling future collaborations with partners in the National Weather Center. The future research areas enabled by this project have significant societal benefits, including improved precipitation forecasts and radar measurements, and an improved understanding of the role of clouds in Earth's present and climate.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.