Marine boundary layer clouds and precipitation observed in a sustained period of open mesoscale cellular convection (MCC) over the Southern Ocean (SO) are investigated using Clouds, Aerosols, Precipitation, Radiation, and atmospherIc Composition Over the southeRn oceaN 2016 observations, Himawari‐8 products, and numerical simulations. The shallow convection was characterized by the presence of supercooled liquid water and mixed‐phase clouds in the sub‐freezing temperature range, consistent with earlier in‐situ observations where ice multiplication is found to be active in producing large quantities of ice in open MCC clouds. Ice‐phase precipitation was observed to melt below cloud base with evidence of cold pools produced in a decoupled boundary layer. Convection‐permitting simulations using the weather research and forecasting model were able to reproduce many of the surface meteorological features and their evolution. However, the evolution of the boundary layer height and the degree of decoupling were poorly simulated, along with the absence of cold pools. The observed cloud morphology and microphysical characteristics were also not well reproduced in the control simulation with the Thompson microphysics scheme, where too much supercooled water was simulated in a too homogenous cloud field. Sensitivity experiments with modified microphysical parameters led to a higher production of glaciated clouds and precipitation. Sensitivity experiments with different boundary layer schemes and vertical resolution, however, showed a smaller impact. A bias of ∼4°C in the initial boundary conditions of the sea surface temperature is discussed. This study highlights the challenge of representing the complex physical processes that underpin the cloud, precipitation, and boundary layer characteristics of the open MCC over the SO.

中文翻译：

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南部海洋的浅对流和降水：以CAPRICORN 2016野战活动为例

使用2016年10月南部观测结果中的云，气溶胶，降水，辐射和大气成分，研究了在南大洋（SO）持续开放的中尺度细胞对流（MCC）的持续时间内观测到的海洋边界层云和降水，Himawari-8产品和数值模拟。浅层对流的特征是在低于冰点的温度范围内存在过冷的液态水和混合相云，这与早期的现场观测结果一致，在该观测中，发现冰的繁殖活跃在MCC的开放云中产生大量的冰。 。观察到冰期降水在云层下方融化，并有在分离的边界层中产生冷池的证据。使用天气研究和预报模型进行的对流允许模拟能够重现许多地表气象特征及其演变。但是，边界层高度和去耦程度的演变很难模拟，而且没有冷池。在汤普森微物理学方案的控制模拟中，所观察到的云的形态和微物理特征也没有得到很好的再现，因为在太均匀的云场中模拟了太多的过冷水。修改了微物理参数的敏感性实验导致了更高的冰川云产量和降水量。但是，使用不同边界层方案和垂直分辨率进行的灵敏度实验显示的影响较小。讨论了在海面温度的初始边界条件下约4°C的偏差。这项研究突显了代表复杂的物理过程所面临的挑战，这些过程是SO上开放MCC的云，降水和边界层特征的基础。