Analysis of Cirrus Clouds and Atmospheric Humidity with Cloud Resolving Numerical Model Calculations

云对全球气候模型构成了重大挑战，从过程层面对云形成的理解到控制全球云分布的过程仍然存在不确定性。这个项目提供了高分辨率的数值模式模拟，将促进我们从理论上理解控制卷云产生和全球分布的主导因素，它们对大气水汽的影响，以及云/水汽组合系统的辐射影响。卷云在对流层上层脱水中的作用仍然没有得到很好的量化。该项目的重点是卷云与环境之间相互作用的重要性，旨在弥合对个别卷云的详细研究与云场的全域特性之间在数值模拟方面的差距。该项目的目标是：(I)确定成核过程(传统上是卷云研究的重点)与成核后过程(如凝结水的重力再分配)对云微物理性质的相对重要性；(Ii)量化云微物理性质对全域水汽(反过来可能反馈到云形成)和全域云场性质(如出现频率和冰水路径)的影响；(Iii)将(I)和(Ii)的结果与有利于云形成的条件的动力学约束联系起来。该项目特别侧重于卷云在热带对流层顶层中的作用。该项目的成果将有助于更好地理解卷云在TTL和平流层水汽调节中的作用(对气候辐射强迫和平流层化学产生重要影响)。TTL在几个方面也是研究卷云及其与环境相互作用的理想之选，因为有利于就地形成卷云的动力条件以及TTL的大尺度结构都可以被很好地理想化。该项目的目标是通过广泛的数值实验来解决，该模式可以从非常高分辨率的云尺度模拟扩展到整个热带的模拟。智力上的优点：来自该项目的见解将有助于改进一般环流模式的参数化，从而改善气候预测。为决策者提供有关未来气候的更准确信息。该项目将支持一名声誉良好的指定博士后研究员和一名研究生，从而培养下一代云建模专家。此外，PI将积极促进普林斯顿大学本科生的参与(以初级和高级论文的形式)，从而为一群经常跟踪工业、金融和政府职业的学生提供第一手经验和更好地了解气候科学。

Clouds pose a major challenge for global climate models, and uncertainties remain from process level understanding of cloud formation to processes that control the global cloud distribution. This project provides high-resolution numerical model simulations that will advance our theoretical understanding of the dominant factors controlling the genesis and global distribution of cirrus clouds, their impact on atmospheric water vapor, and the radiative impact of the combined cloud/vapor system. The role of cirrus clouds in dehydration of the upper troposphere remains not well quantified. The project's focus is on the importance of the interaction between cirrus clouds and the environment, and aims to bridge the gap in numerical modeling between the detailed study of individual cirrus clouds and the full domain-wide properties of the cloud field. The objectives of this project are (i) to determine the relative importance of nucleation processes (traditionally a focus of cirrus research) to post-nucleation processes (such as gravitational redistribution of condensate) on the cloud's microphysical properties; (ii) to quantify the impact of the cloud microphysical properties on the domain-wide moisture field (which in turn may feed back onto cloud formation) and domain-wide cloud field properties (such as occurrence frequency and ice water path); and (iii) to put the results from (i) and (ii) in context with the dynamical constraints on conditions favorable for cloud formation. The project focuses specifically on the role of cirrus in the tropical tropopause layer (TTL). Results from the project will contribute to improved understanding of the role of cirrus clouds for the regulation of water vapor in the TTL and stratosphere (with important consequences for the radiative forcing of climate, and stratospheric chemistry). The TTL is also in several ways ideal to study cirrus clouds and their interaction with the environment as both the dynamical conditions favoring in-situ cirrus cloud formation, as well as the large-scale structure of the TTL, can be reasonably well idealized.The objectives of the project are addressed with a wide range of numerical experiments with a cloud-resolving model that is scalable from very high resolution simulations at cloud scale to simulations of the entire tropics.Intellectual Merit :Insights from this project will help to improve parameterizations for general circulation models, leading to improved climate predictions.Broader Impacts :This project will help to reduce uncertainties in climate predictions, providing policy makers with more accurate information on future climate. The project will support a designated post-doctoral researcher with excellent reputation and a graduate student, thus training the next generation of cloud modeling specialists. Further, the PI will actively promote involvement of undergraduate students (in the form of Junior and Senior Theses) at Princeton University, thereby providing a first-hand experience and better understanding of climate science to a body of students that frequently follows careers in industry, finance and government.