CAREER: The Hydrological Cycle and the Maintenance of the Atmospheric Circulation: Entropy Perspective

维持大气环流需要不断产生动能来平衡摩擦耗散。传统上，大气被描述为一个热机，通过以热的形式将势能从温暖的地区传递到寒冷的地区来产生动能。然而，最近的研究表明，水汽扩散、不可逆相变和降水等潮湿过程是大气中大部分不可逆熵（一种测量无法转化为运动或动能的势能）的原因。有人认为，由于大气作为除湿器，其作为热机的能力降低了：水文循环严重限制了大气环流产生的动能。本研究探讨了水文循环与环流强度之间的关系。研究方向主要包括三个方面：基于开放系统和瞬态系统的熵和可用势能收支的新理论框架的发展，该框架在案例研究中的应用，包括浅对流、飓风和中纬度风暴系统，以及全球熵收支的分析，重点研究气候变化对熵产生和动能耗散的影响。学术价值：首席研究员将(1)对大气环流的维持及其与水文循环的关系提出新的观点；(2)评估未来气候变化对雷暴和飓风等极端事件的数量和强度的影响。更广泛的影响：将开设两门关于大气热力学和气候的新课程（本科生和研究生各一门）。这些课程将直接让学生参与一些研究活动，包括大气流动的高端模拟。将编写一本关于大气中不可逆热力学的教科书。期望本课题能为研究生提供一个研究课题。

The maintenance of the atmospheric circulation requires a continuous production of kinetic energy to balance frictional dissipation. Traditionally, the atmosphere is described as acting as a heat engine that produces kinetic energy by transporting potential energy in the form of heat from warm to cold regions. However, recent studies indicate that moist processes such as diffusion of water vapor, irreversible phase transition and precipitation are responsible for most of the irreversible entropy (a measure of the potential energy unavailable for conversion to motion or kinetic energy) in the atmosphere. It is argued that, as the atmosphere acts as a dehumidifier, its ability to function as a heat engine is reduced: the hydrological cycle severely limits the amount of kinetic energy produced by the atmospheric circulation. This research investigates the connection between the hydrological cycle and the intensity of the circulation. The research component follows three main directions: the development of a new theoretical framework based on the entropy and available potential energy budgets in open systems and transients, the application of this framework in case studies, including shallow convection, hurricanes, and midlatitude storm systems, and the analysis of the global entropy budget, focusing on the impacts of climate change on entropy production and kinetic energy dissipation.Intellectual merit: The Principal Investigator will (1) develop a new perspective on the maintenance of the general circulation of the atmosphere and its relationship to the hydrological cycle, (2) assess the impacts of future climate change on the number and intensity of extreme events such as thunderstorms and hurricanes.Broader Impacts: Two new courses (one undergraduate and one graduate) on atmospheric thermodynamics and climate will be introduced. These courses will directly involve students in some of the research activities, including high-end simulations of atmospheric flows. A textbook on irreversible thermodynamics in the atmosphere will be prepared. It is expected that this project will provide a research topic for graduate student.