FOR 1525: INUIT - Ice Nuclei Research Unit

大气中的冰晶对于降水的形成和云的辐射特性起着重要作用。混合相云是由过冷液滴和冰粒组成的云。它们占大气中云的很大一部分，但我们对这些云的微物理特性的了解仍然有限。一个重要的问题是冰是如何在这些云中形成的。虽然人们已经确定，在混合相云中需要冰核作为冰晶初始形成的种子，但关于大气冰核的浓度和变化及其物理化学性质的许多问题仍有待回答。该研究股研究大气层中的异质冰形成。这些研究包括对成核过程的性质以及对与大气有关的冰核的化学、微物理和生物特性（作为温度和水饱和度的函数）进行实验室调查。开展了大量的现场实验和监测调查，研究了不同冻结方式下大气冰核的数量浓度、变化、大小、化学成分、表面性质和来源。各种国家的最先进的方法和设施用于冰核的特性。矿尘颗粒、火山灰和生物冰核的冰成核特性是研究股关注的一个重点。实验研究的结果被送入云过程模式和云分辨中尺度模式，以提高云在模型中的代表性，模拟云过程，并量化冰核类型和冻结模式的贡献。

Ice crystals in the atmosphere play an important role for the formation of precipitation and for the radiative properties of clouds. Mixed-phase clouds are clouds that consist of both, super-cooled liquid droplets and ice particles. They account for a large fraction of the clouds in the atmosphere but our knowledge on the microphysical properties of these clouds is still limited. An important question is how ice forms in these clouds. While it is well established that an ice nucleus is needed as a seed for the initial formation of an ice crystal in mixed-phase clouds many questions remain to be answered on the concentration and variability of atmospheric ice nuclei and their physico-chemical properties. The Research Unit studies heterogeneous ice formation in the atmosphere. The studies include laboratory investigations on the nature of the nucleation process and on the chemical, microphysical and biological characterisation of atmospherically relevant ice nuclei (as a function of temperature and water saturation). Intensive field experiments are conducted as well as monitoring surveys to study the number concentration, variability, size, chemical composition, surface properties and sources of atmospheric ice nuclei in different freezing modes. Various state-of-the-art methods and facilities are used for the characterisation of the ice nuclei. Ice nucleating properties of mineral dust particles, volcanic ash and biological ice nuclei are a focus of attention within the Research Unit. The results of the experimental investigations are fed into a cloud process model and a cloud-resolving mesoscale model to improve the representation of clouds in the models, to simulate cloud processes and to quantify the contribution of ice nuclei types and freezing modes.