FOR 1525: INUIT - Ice Nuclei Research Unit

大气中的冰晶对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观物理性质的了解仍然有限。一个重要的问题是这些云中的冰是如何形成的。虽然已经确定在混合相云中需要冰核作为初始形成冰晶的种子，但关于大气冰核的浓度和可变性及其物理化学性质仍有许多问题有待回答。研究组研究大气中非均质冰的形成。这些研究包括对成核过程的性质以及与大气有关的冰核的化学、微物理和生物学特征(作为温度和水饱和度的函数)的实验室调查。为研究不同冰冻模式下大气冰核的数量浓度、变异性、大小、化学成分、表面性质和来源，进行了密集的野外实验和监测调查。各种最先进的方法和设施被用于描述冰核的特征。矿物粉尘颗粒、火山灰和生物冰核的成冰特性是研究股关注的一个焦点。实验研究结果被输入到云过程模式和云分辨中尺度模式中，以改进云在模式中的表示，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.