An advanced multiwavelength polarization Raman lidar was operated aboard the icebreaker Polarstern during the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition to continuously monitor aerosol and cloud layers in the central Arctic up to 30 km height. The expedition lasted from September 2019 to October 2020 and measurements were mostly taken between 85 and 88.5^∘ N. The lidar was integrated into a complex remote-sensing infrastructure aboard the Polarstern. In this article, novel lidar techniques, innovative concepts to study aerosol–cloud interaction in the Arctic, and unique MOSAiC findings will be presented. The highlight of the lidar measurements was the detection of a 10 km deep wildfire smoke layer over the North Pole region between 7–8 km and 17–18 km height with an aerosol optical thickness (AOT) at 532 nm of around 0.1 (in October–November 2019) and 0.05 from December to March. The dual-wavelength Raman lidar technique allowed us to unambiguously identify smoke as the dominating aerosol type in the aerosol layer in the upper troposphere and lower stratosphere (UTLS). An additional contribution to the 532 nm AOT by volcanic sulfate aerosol (Raikoke eruption) was estimated to always be lower than 15 %. The optical and microphysical properties of the UTLS smoke layer are presented in an accompanying paper (Ohneiser et al., 2021). This smoke event offered the unique opportunity to study the influence of organic aerosol particles (serving as ice-nucleating particles, INPs) on cirrus formation in the upper troposphere. An example of a closure study is presented to explain our concept of investigating aerosol–cloud interaction in this field. The smoke particles were obviously able to control the evolution of the cirrus system and caused low ice crystal number concentration. After the discussion of two typical Arctic haze events, we present a case study of the evolution of a long-lasting mixed-phase cloud layer embedded in Arctic haze in the free troposphere. The recently introduced dual-field-of-view polarization lidar technique was applied, for the first time, to mixed-phase cloud observations in order to determine the microphysical properties of the water droplets. The mixed-phase cloud closure experiment (based on combined lidar and radar observations) indicated that the observed aerosol levels controlled the number concentrations of nucleated droplets and ice crystals.

中文翻译：

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MOSAiC 期间野火烟雾、北极雾霾和气溶胶对北极地区混合相云和卷云的影响：介绍

在 MOSAiC（北极气候研究多学科漂移观测站）探险期间，在破冰船Polarstern上运行了先进的多波长偏振拉曼激光雷达，以连续监测北极中部高达 30 公里高度的气溶胶和云层。这次探险从 2019 年 9 月持续到 2020 年 10 月，测量主要在 85 到 88.5 ^∘  N 之间进行。激光雷达被集成到Polarstern上的复杂遥感基础设施中. 在本文中，将介绍新颖的激光雷达技术、研究北极气溶胶-云相互作用的创新概念以及独特的 MOSAiC 发现。激光雷达测量的亮点是在北极地区 7-8 公里和 17-18 公里高度之间检测到 10 公里深的野火烟雾层，气溶胶光学厚度 (AOT) 在 532 nm 处约为 0.1（10 月– 2019 年 11 月）和 12 月至 3 月的 0.05。双波长拉曼激光雷达技术使我们能够明确地将烟雾识别为对流层上部和平流层下部 (UTLS) 气溶胶层中的主要气溶胶类型。据估计，火山硫酸盐气溶胶（Raikoke 喷发）对 532 nm AOT 的额外贡献始终低于 15%。（Ohneiser 等人，2021 年）. 这次烟雾事件为研究有机气溶胶粒子（作为冰核粒子，INP）对对流层上部卷云形成的影响提供了独特的机会。提供了一个封闭研究的例子来解释我们在该领域研究气溶胶-云相互作用的概念。烟雾颗粒显然能够控制卷云系统的演化并导致冰晶数浓度较低。在讨论了两个典型的北极雾霾事件之后，我们提出了一个关于自由对流层中嵌入北极雾霾中的长期混合相云层演化的案例研究。最近引入的双视场偏振激光雷达技术首次应用于混合相云观测，以确定水滴的微物理特性。