Interaction of Aerosols with Clouds and Radiation

未来气候预测的高度不确定性是由于对云与可见光（太阳）和红外线（地面）辐射的相互作用缺乏了解。大气气溶胶粒子作为云凝结核（CCN）或冰核（IN）的能力对云的光学性质和寿命有很大影响。这种所谓的间接气溶胶效应被认为是评估人类对气候影响的最大不确定性来源之一。到目前为止，人们对云的气候相关性质及其形成过程的认识仍然很差，特别是对过冷云滴和冰晶共存的混合相云的认识。以往的研究发现，云的辐射特性强烈依赖于云冰的质量分数，而云冰的质量分数又受IN丰度的影响。IN浓度的增加也被认为会增加降水，从而导致云寿命和云量的减少，导致大气变暖。在这方面，迫切的问题是： 哪些气溶胶颗粒在我们的大气中起作用？ 大气气溶胶通过哪些详细的机制促成冰的形成？为了探索和减少这些不确定性，该项目的一个主要目标是开发一种用于测量云滴和冰晶的新入口。该入口还允许提取混合相云中的小冰粒，用于对流层IN的物理化学表征。该入口将代表一种用于云的现场调查的新工具，并将提供任何其他现有入口无法提供的信息。另一个重点将是结合地面和遥感观测混合相云。这将有助于在气候模式中更好地对混合相云的辐射特性进行参数化。新设计的入口将是这些测量的一个组成部分。这些研究将在少女峰进行，少女峰是世界上最著名的高山研究站之一，位于瑞士中部海拔3580米。这个独特的位置提供了在代表当前欧洲背景的混合相云中进行这些研究的可能性。拟议的研究将在几个瑞士和一个德国研究所的合作努力下进行。它与有关机构的专门知识相一致，这些机构是：Paul Scherrer研究所大气化学实验室（气溶胶/云研究）、达沃斯的PMOD/WRC和Payerne的MeteoSwiss（辐射）以及卡尔斯鲁厄理工学院气象和气候研究所（云微观物理学和光学）。

High uncertainties in future climate predictions arise from insufficient knowledge of the interaction of clouds with visible (solar) and infrared (terrestrial) radiation. The optical properties and lifetime of clouds are strongly influenced by the ability of atmospheric aerosol particles to act as cloud condensation nuclei (CCN) or ice nuclei (IN). This so-called indirect aerosol effect has been recognized as one of the greatest source of uncertainty in assessing human impact on climate. Up to now, the climate relevant properties of clouds and their formation processes are still poorly understood, particularly those of mixed-phase clouds where supercooled cloud droplets and ice crystals coexist. Previous research has found that the cloud radiative properties strongly depend on the cloud ice mass fraction, which is influenced by the abundance of IN. Increased IN concentrations are also thought to enhance precipitation, thus causing a decrease in cloud lifetime and cloud cover, resulting in a warming of the atmosphere. Burning questions in this context are:- Which aerosol particles act as IN in our atmosphere ?- By which detailed mechanisms do atmospheric aerosols contribute to the formation of ice ?To explore and reduce these uncertainties, one major goal of this project is to develop a new inlet for the measurement of cloud droplets and ice crystals. This inlet will also allow the extraction of small ice particles in mixed-phase clouds for the physico-chemical characterization of tropospheric IN. The inlet will represent a novel tool for the in-situ investigation of clouds and will deliver information that is not available by means of any other existing inlet. Another focus will be the combination of ground-based and remote-sensing observations of mixed-phase clouds. This will contribute to better parameterization of radiative properties of mixed-phase clouds in climate models. The newly designed inlet will be an integral part of these measurements. These studies will be performed at the Jungfraujoch, one of the world’s most prominent high Alpine research stations located at 3580 m altitude in the middle of Switzerland. This unique location offers the possibility to perform these studies in mixed-phase clouds that are representative for the current European background. The proposed research will be performed in a collaborative effort of several Swiss and a German institute. It is in line with the expertise of the involved institutions, i.e. the Laboratory of Atmospheric Chemistry of the Paul Scherrer Institut (aerosol/cloud research), the PMOD/WRC in Davos and MeteoSwiss in Payerne (radiation) as well as the Institute for Meteorology and Climate Research at the Karlsruhe Institute of Technology (cloud microphysics and optics).