Understanding tropical cirrus by combining laboratory cloud simulation and field experiments with process and circulation modelling

这个项目（TropiC）是由芝加哥大学领导的国际卷云研究合作项目的一部分。PIRE项目汇集了一个由四个美国专家小组和四个欧洲专家小组组成的国际小组，进行协调研究，以提高对冷热带过渡层（TTL）中薄的高空卷云的认识，这是大气中最不为人所知的区域之一。虽然这些冰云在光学上很薄，而且经常是看不见的，但它们在大气和气候系统中扮演着重要的角色。PIRE项目重点研究卷云的形成过程、内部动力学以及与大气辐射和动力过程的相互作用。作为PIRE的一部分，TropiC的目标是研究和更好地理解(1)非均质和非均质冰形成作为卷云冰晶来源的过程细节和作用，(2)水在混合相云和卷云中的平衡和动力学同位素分异效应，(3)卷云层中冰晶的丰度模式，以及(4)热带卷云在全球和区域模式设置中的表现和影响。TropiC是卡尔斯鲁厄理工学院（KIT）和科学研究中心（FZJ）的实验室、实地和建模活动的协调努力。工作计划包括在KIT的AIDA云室设施中进行控制良好的云模拟实验，在StratoClim和FZJ的其他野外活动期间对卷云原位测量的详细分析，以及使用MAID （FZJ）和ACPIM（曼彻斯特大学）过程模型，大尺度拉格朗日型模型CLaMS-Ice (FZJ)，全球模式框架ICON GCM (KIT)，以及来自欧洲和美国的PIRE联盟合作伙伴的观测和过程模式。项目成果包括云、天气和气候模式的卷云过程的新模式参数化，StratoClim和AIDA云实验中观测到的典型卷云案例的特征数据集，这些数据集将被PIRE建模合作伙伴用作比较模式中不同冰核和卷云形成方案的试验平台。以及一组全球和区域ICON对当今气候和全球变暖的模拟，以便与PIRE联盟所做的高分辨率和大规模模拟进行比较。最后，该项目的工作和整个PIRE合作将导致对TTL卷云形成过程的深入了解，并在最先进的大气模型中扩展对卷云的描述。因此，区域和全球模式将更准确地模拟TTL卷云的发生及其在气候变化中的作用。作为对PIRE项目的一项服务，新的博士生和博士后将在AIDA独特的云室设施接受实验云过程研究和相关建模的培训。

This project (TropiC) is part of the PIRE International Partnership for Cirrus Studies lead by the University of Chicago. The PIRE project brings together an international team of four US American and four European expert teams for coordinated studies to advance knowledge of thin, high-altitude cirrus clouds in the cold tropical transition layer (TTL), one of the least understood region in the atmosphere. Though optically thin and often not visible, these cold ice clouds play important roles in the atmosphere and the climate system. The PIRE project focuses on formation processes of cirrus clouds, their internal dynamics, as well as their interaction with atmospheric radiative and dynamic processes. The objectives of TropiC as part of PIRE are to study and better understand (1) the process details and roles of heterogeneous and homogeneous ice formation as a source for cirrus ice crystals, (2) the equilibrium and kinetic isotopic fractionation effects of water in mixed-phase and cirrus clouds, (3) the abundance patterns of ice crystals in cirrus layers, and (4) the representation and impact of tropical cirrus clouds in global and regional model setups.TropiC is a coordinated effort of laboratory, field and modelling activities of the Karlsruhe Institute of Technology (KIT) and the Forschungszentrum Jülich (FZJ). The work program includes well-controlled cloud simulation experiments in the AIDA cloud chamber facilities at KIT, the detailed analysis of cirrus in situ measurements during StratoClim and other field activities of FZJ, and modelling studies with the process models MAID (FZJ) and ACPIM (University of Manchester), the large-scale Lagrangian type model CLaMS-Ice (FZJ), the global model framework ICON GCM (KIT), as well as the observational and process models from the PIRE consortium partners in Europe and the U.S. Among the project deliverables are new model parameterizations of cirrus processes for cloud, weather and climate models, well characterized data sets of typical cirrus cases from observations during StratoClim and AIDA cloud experiments to be used by the PIRE modelling partners as a test bed for comparing different ice nucleation and cirrus formation schemes in models, and a set of global and regional ICON simulations of the present-day climate and of global warming for comparison with the high-resolution and large-scale modeling done within the PIRE consortium. Finally, the work within this project and the whole PIRE collaboration will lead to a well advanced process understanding of TTL cirrus formation, and an extended description of cirrus clouds in the most advanced atmospheric models. Therefore, regional and global models will more accurately simulate the occurrence of TTL cirrus and their role in a changing climate. As a service to the PIRE project, new PhD students and postdocs will be trained at the unique AIDA cloud chamber facility in experimental cloud process studies and related modelling.