Towards Understanding the Phase Composition of Mixed-Phase Clouds in High Latitudes using a Novel Airborne Technique for Discriminating Ice Crystals and Liquid Droplets

混合相云仍然是了解高纬度对气候变化反应的最大不确定因素之一，特别是由于不准确地表示冰和液体的相对组成(相组成)。尽管如此，模拟的冰粒浓度和测量的冰粒浓度之间仍然存在差异，这导致对云的宏观物理性质(如云量)的不准确描述，以及对沉积的太阳能的错误计算。需要现场测量来解决这些差异，并改进气候和大气环流模型。然而，在高纬度地区，现场测量要么很少，要么受到现场仪器区分小(50微米)云粒相的能力的限制。相组成的不确定性，特别是高纬度混合相云中小冰粒的存在是提出这一建议的动机。我们计划调查北极和南大洋即将开展的实地活动中小冰粒的存在和冰粒浓度，同时详细了解这些冰粒的微物理和光学性质。为了达到我们的目标，我们建议利用现有的粒子习性成像和极地散射(PHIPS)探测器，结合冰粒成像和散射测量，开发一种新的数据产品，根据球形和非球面冰滴的角光散射特性区分球形和非球形冰滴。该项目的主要目标将是：(1)在高纬度混合相云中选择性地探测尺寸小于50微米的冰粒；(2)表征混合相云粒子的微观物理性质，包括冰晶的形状和晶体的复杂性；(3)量化混合相冰粒子的短波角光散射特性。结合云室模拟实验对三次野外活动收集的数据进行分析，将为理解高纬度对气候变化的响应及其在气候模式中的表现做出重要贡献。

Mixed-phase clouds remain one of the greatest source of uncertainties in understanding the high latitude response to climate change in particular due to an inaccurate representation of the relative composition of ice and liquid phases (phase composition). Still, discrepancies exist between the modeled and measured ice particle concentrations, which leads to inaccurate representation of the cloud macrophysical properties, such as cloud fraction, and to miscalculation of the deposited solar energy. In-situ measurements are needed to address these discrepancies and to improve climate and general-circulation models. However, in high latitudes in-situ measurements are either scarce or limited by the capabilities of the in-situ instruments to discriminate the phase of small (<50 micrometer) cloud particles.The uncertainty in the phase composition and especially the existence of small ice particles in high latitude mixed-phase clouds was the motivation for this proposal. We plan to investigate the existence of small ice particles and the ice particle concentrations in upcoming field campaigns in the Arctic and in the Southern Ocean and simultaneously get a detailed insight into the microphysical and optical properties of those ice particles. To reach our goals, we propose to use the existing Particle Habit Imaging and Polar Scattering (PHIPS) probe that combines ice particle imaging and scattering measurements and develop a new data product that separates spherical droplets from aspherical ice particles based on their angular light scattering properties.The main objectives of the proposed project will be (1) the selective detection of ice particles in the sub-50 micrometer size range in high latitude mixed-phase clouds, (2) the characterization of the microphysical properties of mixed-phase cloud particles, including the ice crystal shape and crystal complexity, and (3) the quantification of the shortwave angular light scattering properties of mixed-phase ice particles. The analysis of the data gathered from three field campaigns combined with cloud chamber simulation experiments will provide an important contribution to the understanding of the high latitude response to climate change and its representation in climate models.