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

云对全球气候模式构成了重大挑战，从云形成的过程水平理解到控制全球云分布的过程，都存在不确定性。该项目提供了高分辨率的数值模式模拟，这将促进我们对控制卷云的成因和全球分布的主导因素的理论理解，它们对大气水汽的影响，以及云/蒸汽组合系统的辐射影响。卷云在对流层上部脱水中的作用仍然没有很好的量化。该项目的重点是卷云和环境之间的相互作用的重要性，并旨在弥合差距在数值模拟之间的个别卷云的详细研究和云场的全域属性。这个项目的目标是（i）确定成核过程的相对重要性（传统上是卷云研究的焦点）到后成核过程（如凝结物的重力再分布）对云的微物理性质的影响;（ii）量化云微物理特性对全域湿度场的影响（这反过来又可能反馈到云的形成）和全域云场特性（如出现频率和冰水路径）;以及（iii）将（i）和（ii）的结果与有利于云形成的条件的动力学约束相结合。该项目特别侧重于卷云在热带对流层顶层（TTL）中的作用。该项目的结果将有助于更好地了解卷云在TTL和平流层中调节水蒸气的作用（对气候的辐射强迫和平流层化学具有重要影响）。TTL在几个方面也是研究卷云及其与环境相互作用的理想方法，因为它既有利于卷云形成的动力学条件，也有利于TTL的大尺度结构，可以合理地理想化。该项目的目标是通过对云进行广泛的数值实验来解决的-分辨率模式，可从云尺度的极高分辨率模拟扩展到整个热带的模拟。智力优势：该项目的见解将有助于改善大气环流模式的参数化，从而改善气候预测。该项目将有助于减少气候预测的不确定性，为决策者提供关于未来气候的更准确信息。该项目将支持一名具有良好声誉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），从而为经常从事工业，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.