Collaborative Research: Examining Cloud-Radiation Feedback at Convective Scales in Tropical Cyclones

这项研究的首要目标是扩大我们对热带气旋（如飓风和台风）如何形成和加强的理解。热带气旋是美国造成生命财产损失的主要原因，沿海人口增长和气候变化加剧了这些影响。然而，尽管经过数十年的研究，在了解它们的形成和强化方面仍存在许多差距。因此，这个项目解决的问题只会随着时间的推移而变得更加紧迫。研究人员将研究云和辐射之间的相互作用。最近的研究表明，这种相互作用加速了热带气旋的形成。这个项目将促进我们在单个雷暴系统尺度上对这种反馈的理解。通过这样做，这项研究将最终有助于改善热带气旋的预报，这将反过来有助于减轻热带气旋登陆时的生命和财产损失。该项目还将直接支持早期职业科学家、研究生研究人员和本科生研究人员的领导能力和专业发展。为了支持推进STEM教育，项目团队将通过“Skype a Scientist”和其他虚拟活动开展K-12教育推广。为了解决与热带气旋（tc）云辐射反馈相关的科学空白，本研究将解决以下问题：在热带浅对流、深对流和层状降水的对流尺度上，浮力、垂直运动和湿熵对云辐射强迫（CRF）的响应是什么？在这些机制中，辐射反馈在加速对流高级化发展和TC形成中有什么独特的作用？它们是通过什么机制这样做的？模拟对流尺度对CRF的响应对模型框架、物理参数化和网格分辨率变化的鲁棒性如何？这些问题将通过一系列新颖的、以过程为导向的数值模型实验来解决，这些实验使用区域和全球允许对流的模型。采用假设驱动的方法，将进行模式实验，以检验云和深层对流（即，时间尺度降至~1小时或更短）对云辐射强迫（CRF）的消除和开启的瞬态响应。实验的一个新颖方面是在云和降水的特定种群中选择性地包含/排除CRF。这种方法的动机是一种新的假设，即层状雨和砧状云中的CRF在加速TC的形成中起主导作用。这些实验将在现实和理想化的框架下进行，以支持鲁棒性和代表性。该项目还将需要研究与不同云群中水成物和辐射强迫的数值表示相关的模式不确定性，这是第一个在对流尺度上检查和记录TC起源背景下的这种敏感性的项目。因此，预计该项目的结果将支持模型预测的进步，并在广泛的尺度和环境中进行预测。由于CRF被认为是在广泛的物理尺度上的重要物理过程，因此从这项工作中产生的新经验教训预计将比TC主题应用得更广泛。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The overarching goal of this research is to expand our understanding of how tropical cyclones (e.g., hurricanes and typhoons) form and intensify. Tropical cyclones are the leading driver of losses to life and property in the US, with coastal population growth and climate change exacerbating these impacts. However, many gaps remain in understanding their formation and intensification, despite decades of study. This project therefore addresses an issue that only grows more pressing with time. The investigators will examine the interaction between clouds and radiation. Recent work reveals that this interaction accelerates the formation of tropical cyclones. This project will advance our understanding of this feedback at the scales of individual thunderstorm systems. By doing so, this research will ultimately help improve the forecasting of tropical cyclones, which will in turn help mitigate losses of life and property when they make landfall. The project will also directly support the leadership and professional development of early-career scientists, graduate researchers, and undergraduate researchers. In support of advancing STEM education, the project team will conduct K-12 educational outreach through “Skype a Scientist” and other virtual activities.To address science gaps related to cloud–radiation feedback in tropical cyclones (TCs), this research will address the following questions:1. What are the responses of buoyancy, vertical motion, and moist entropy to cloud–radiation forcing (CRF) on convective scales in tropical shallow convection, deep convection, and stratiform rainfall?2. What are the unique roles of radiative feedback in these regimes in accelerating convective upscale development and TC genesis, and through what mechanism(s) do they do so?3. How robust are simulated convective-scale responses to CRF to changes in model framework, physical parameterization, and grid resolution?These questions will be addressed through a series of novel, process-oriented numerical model experiments using both regional and global convection-permitting modeling. Following a hypothesis-driven approach, model experiments will be executed to examine the transient response of clouds and deep convection (i.e., on time scales down to ~1 hour and less) to the removal and switch-on of cloud–radiative forcing (CRF). A novel aspect of the experiments is the selective inclusion/exclusion of CRF in specific populations of clouds and precipitation. This approach is motivated by the novel hypothesis that CRF in stratiform rain and anvil clouds plays a leading role in accelerating TC genesis. These experiments will be cast in both realistic and idealized frameworks to support both robustness and representativeness. The project will also entail studying model uncertainty tied to the numerical representation of hydrometeors and radiative forcing in distinct cloud populations, being among the first to examine and document this sensitivity at convective scales in the context of TC genesis. The results of this project are therefore expected to support the advancement of model prediction and forecasting across a broad range of scales and settings. Since CRF is recognized to be an important physical process on a wide range of physical scales, the new lessons arising from this work are expected to apply more broadly than the TC subject.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.