Abstract. The thermodynamic phase of clouds in low and middle levels over the Southern Ocean and the Arctic marine regions is poorly known, leading to uncertainties in the radiation budget in weather and climate models. To improve the knowledge of the cloud phase, we analyse 2 years of the raDAR-liDAR (DARDAR) dataset based on active satellite instruments. We classify clouds according to their base and top height and focus on low-, mid-, and mid- to low-level clouds as they are the most frequent in the mixed-phase temperature regime. Low-level single-layer clouds occur in 8 %–15 % of all profiles, but single-layer clouds spanning the mid-level also amount to approx. 15 %. Liquid clouds show mainly a smaller vertical extent but a horizontally larger extent compared to ice clouds. The results show the highest liquid fractions for low-level and mid-level clouds. Two local minima in the liquid fraction are observed around cloud top temperatures of −15 and −5 °C. Mid-level and mid- to low-level clouds over the Southern Ocean and low-level clouds in both polar regions show higher liquid fractions if they occur over sea ice compared to the open ocean. Low-level clouds and mid- to low-level clouds with high sea salt concentrations, used as a proxy for sea spray, show reduced liquid fractions. In mid-level clouds, dust shows the largest correlations with liquid fraction, with a lower liquid fraction for a higher dust aerosol concentration. Low-level clouds clearly show the largest contribution to the shortwave cloud radiative effect in both polar regions, followed by mid- to low-level clouds.

中文翻译：

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南大洋和北极海洋区域低基底和中基底云的特征及其热力相


摘要。南大洋和北极海洋地区低层和中层云层的热力学阶段鲜为人知，导致天气和气候模型中的辐射收支存在不确定性。为了提高对云相的了解，我们分析了基于主动卫星仪器的 2 年雷达-激光雷达 (DARDAR) 数据集。我们根据云的底部和顶部高度对云进行分类，并重点关注低层、中层和中低层云，因为它们在混合相温度状况中最常见。低层单层云占所有剖面的 8%–15%，但跨越中层的单层云也达到约 10%。 15%。与冰云相比，液体云的垂直范围主要较小，但水平范围较大。结果显示低层和中层云的液体比例最高。在云顶温度 -15 和 -5°C 附近观察到液体部分的两个局部最小值。与公海相比，南大洋上空的中层和中低层云以及两极地区的低层云如果出现在海冰上方，则显示出更高的液体分数。低层云和具有高海盐浓度的中低层云（用作海雾的代表）显示出液体分数减少。在中层云中，灰尘与液体分数的相关性最大，液体分数越低，灰尘气溶胶浓度越高。低层云清楚地显示出对两极地区短波云辐射效应的最大贡献，其次是中低层云。