Observations and Modeling of Rime Splintering in Southern Ocean Cumuli
Observations and Modeling of Rime Splintering in Southern Ocean Cumuli
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DOI：
10.1029/2021jd035479
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发表时间：
2021-11
期刊：
影响因子：
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通讯作者：
S. Lasher-Trapp;Emma L. Scott;E. Järvinen;M. Schnaiter;Fritz Waitz;P. DeMott;C. McCluskey;T. Hill
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文献类型：
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作者：
S. Lasher-Trapp;Emma L. Scott;E. Järvinen;M. Schnaiter;Fritz Waitz;P. DeMott;C. McCluskey;T. Hill
最近的研究表明，在气候模式中，正确表示南大洋地区的云相对于准确表示能量平衡非常重要。卫星数据显示，尽管这些云的温度很低，但它们大部分是液态的。然而，有时在该地区观测到含有大量冰晶的云，并暗示了称为雾凇分裂的二次制冰过程。本研究利用新的数据集和高分辨率数值模拟，重新研究了南大洋积积物中的雾凇分裂。在南大洋云辐射气溶胶输送实验研究（SOCRATES）期间获得的测量数据提供了对该地区两天内取样的浅积云冰量的评估。与同一天的冰核粒子（INP）测量结果相比，测量结果有时显示出7个数量级或更多的冰粒子。含有多个上升气流的积积云最倾向于含有高冰浓度，并满足雾凇分裂的预期条件。受观测结果约束的理想化数值模拟表明，多次上升气流产生了更多的冰冻雨滴/霰，并允许它们在较长的时间内穿过时间分裂区，从而使冰粒的数量增加了许多数量级。因此，南大洋极低的INP数量似乎需要一些特殊的条件，如多次上升气流来帮助该地区的积雨云结冰，这可能解释了在那里观测到的过冷积雨云占主导地位。
Recent studies have suggested a correct representation of cloud phase in the Southern Ocean region is important in climate models for an accurate representation of the energy balance. Satellite retrievals indicate many of the clouds are predominantly liquid, despite their low temperatures. However, clouds containing high numbers of ice crystals have sometimes been observed in this region and implicated the secondary ice production process called rime splintering. This study re‐examines rime splintering in Southern Ocean cumuli using both a new data set and high‐resolution numerical modeling. Measurements acquired during the Southern Ocean Clouds Radiation Aerosol Transport Experimental Study (SOCRATES) provide an evaluation of the amount of ice in shallow cumuli sampled over two days in this region. The measurements sometimes exhibit seven orders of magnitude or more ice particles compared to amounts expected from measurements of ice‐nucleating particles (INP) on the same days. Cumuli containing multiple updrafts had the greatest tendency to contain high ice concentrations and meet the expected conditions for rime splintering. Idealized numerical modeling, constrained by the observations, suggests that the multiple updrafts produce more frozen raindrops/graupel, and allow them to travel through the rime‐splintering zone over an extended period of time, increasing the number of ice particles by many orders of magnitude. The extremely low number of INP in the Southern Ocean thus appears to require special conditions like multiple updrafts to help glaciate the cumuli in this region, potentially explaining the predominance of supercooled cumuli observed there.