Entrainment and Freezing Processes in Tropical Convective Clouds during EC-TOOC

云是地球气候的重要组成部分，影响辐射收支、水文循环和全球环流。特别是热带，它涵盖了从信风区的浅积云到内热带辐合区的深对流云的过渡，被认为是一个关键因素。提高我们对云和环流在这个气候子系统中的相互作用的理解是EC-TOOC运动的主要目标，本提案中所述的努力将有助于实现这一目标。通过在研究飞机HALO上部署我们的多用途高光谱云成像仪specMACS，我们计划通过提供云形态和云微物理过程的测量来为EC-TOOC的总体目标做出贡献。具体来说，我们计划使用specMACS的二维RGB图像来重建三维云边界及其运动，从specMACS的光谱辐射观测中检索到的冰分数分布，以及云弓和后向散射荣耀的观测，这些观测揭示了云边缘的平均（液体）液滴大小及其方差。此外，specMACS还将提供重要的二维信息，例如在EC-TOOC期间解释其他仪器观测所需的云掩模。我们的测量也将作为EarthCARE/MSI短波信道的验证。我们将使用我们的测量，以提高云与其环境的湍流混合过程的理解。这一过程对于预测云的发展至关重要，因为卷吸通常会降低云的浮力，而卷吸则为后续热气流的环境提供先决条件。具体来说，我们要分析的云边界运动的统计特性，我们希望相关的湍流混合过程的关键特征（湍流动能，区域的优先夹带或detrainment）。此外，我们计划使用三维云边界来分析其几何特性和缩放行为，其中尺度突变预计与混合特性（均匀与非均匀混合）的变化有关。混合对混合相云的影响在很大程度上是未知的，但预计会影响云的冰川作用，从而影响云的光学特性和降水量。因此，我们计划分析云冰分数如何随高度变化。通过专注于液滴尺寸分布的影响，这是部分由湍流混合过程中形成的，我们将能够提供重要的信息的模型表示的冰川作用过程中，液滴尺寸分布宽度通常不预测在当前的微物理模型。

Clouds are an essential part of the Earth’s climate by affecting the radiation budget, hydrological cycle, and global circulation. Especially the Tropics, which cover the transition from shallow cumuli in the trade-wind regions to deep convective clouds in the inner-tropical convergence zone, are considered a key factor. Improving our understanding of the interactions of clouds and circulation in this subsystem of the climate is a primary goal of the EC-TOOC campaign, to which the efforts described in this proposal will contribute. By deploying our multipurpose hyperspectral cloud imager specMACS on the research aircraft HALO, we plan to contribute to the overarching goals of EC-TOOC by providing measurements of the cloud morphology and cloud microphysical processes. Specifically, we plan to use specMACS’ two-dimensional RGB imagery to reconstruct the three-dimensional cloud boundary and its motion, ice fraction profiles retrieved from specMACS’ spectral radiance observations, and observations of the cloud bow and backscatter glory, which reveal the mean (liquid) droplet size and its variance at the cloud edge. Furthermore, specMACS will provide important two-dimensional information, such as the cloud mask required for interpreting other instruments’ observations during EC-TOOC. Our measurements will also serve as validation for the shortwave channels of EarthCARE/MSI. We will use our measurements to improve the understanding of the turbulent mixing process of clouds with their environment. This process is essential to predict the development of clouds, as entrainment typically decreases their buoyancy, while detrainment preconditions the environment for subsequent thermals. Specifically, we want to analyze the statistical properties of the cloud boundary motion, which we expect to relate to key features of the turbulent mixing process (turbulence kinetic energy, regions of preferential entrainment or detrainment). Furthermore, we plan to use the three-dimensional cloud boundary to analyze its geometrical properties and scaling behavior, where scale breaks are expected to relate to changes in the mixing character (homogeneous vs. inhomogeneous mixing). The impact of mixing on mixed-phase clouds is largely unknown, but is expected to influence glaciation of the cloud and hence cloud optical properties and precipitation production. Accordingly, we plan to analyze how the cloud ice fraction changes with height. By focusing on the influence of the droplet size distribution, which is partially shaped by the turbulent mixing process, we will be able to provide important information for the model representation of the glaciation process, as the droplet size distribution width is typically not predicted in current microphysical models.