Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014
Properties of Arctic liquid and mixed-phase clouds from shipborne Cloudnet observations during ACSE 2014
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DOI：
10.5194/acp-20-14983-2020
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发表时间：
2020-12-04
影响因子：
6.3
通讯作者：
Tjernstrom, Michael
中科院分区：
文献类型：
--
作者：
Achtert, Peggy;O'Connor, Ewan J.;Tjernstrom, Michael
这项研究提出了Cloudnet检索北极云的测量期间进行了为期3个月的研究考察沿着西伯利亚大陆架在夏季和秋季2014年。在秋季，我们发现一个强烈的减少发生的液体云和增加的混合相和冰云在低层相比，夏季。在研究巡航期间观测到的所有液态云中，约有80%显示出低于约50 g m（-2）的红外黑体极限的液态水路径。大多数混合云和冰云的冰水路径小于20 g m（-2）。这些参数的变化对液云的几何厚度影响不大，而暖空气平流事件期间的混合相云通常比不存在此类事件时更薄。所有混合相云的云顶温度非常相似。然而，在没有暖空气平流的情况下，观测到了更多的低云顶温度的情况。对于液态水云，液态水含量廓线显示出随高度的增加而增加，在云的上四分之一内达到最大值，然后向云顶急剧减少。液态水含量最低的云下面观察到的逆温在暖空气平流事件。大多数mixedphase云显示液态水含量的轮廓与非常相似的形状的液体云，但较低的最大值在事件与暖空气以上的行星边界层。混合云中的冰水含量廓线与液态水含量廓线有很大的不同。它们的最大值范围更广，逆温以下的云的冰水含量最低，逆温以上或穿过逆温的云的冰水含量最高。冰水含量曲线通常在低于液态水含量曲线峰值的高度处达到峰值-通常在云的中心，有时更接近云底，这可能是由于晶体穿过云落下时粒子升华所致。
This study presents Cloudnet retrievals of Arctic clouds from measurements conducted during a 3-month research expedition along the Siberian shelf during summer and autumn 2014. During autumn, we find a strong reduction in the occurrence of liquid clouds and an increase for both mixed-phase and ice clouds at low levels compared to summer. About 80 % of all liquid clouds observed during the research cruise show a liquid water path below the infrared black body limit of approximately 50 g m(-2). The majority of mixed-phase and ice clouds had an ice water path below 20 g m(-2).Cloud properties are analysed with respect to cloud-top temperature and boundary layer structure. Changes in these parameters have little effect on the geometric thickness of liquid clouds while mixed-phase clouds during warm-air advection events are generally thinner than when such events were absent. Cloud-top temperatures are very similar for all mixed-phase clouds. However, more cases of lower cloudtop temperature were observed in the absence of warm-air advection.Profiles of liquid and ice water content are normalized with respect to cloud base and height. For liquid water clouds, the liquid water content profile reveals a strong increase with height with a maximum within the upper quarter of the clouds followed by a sharp decrease towards cloud top. Liquid water content is lowest for clouds observed below an inversion during warm-air advection events. Most mixedphase clouds show a liquid water content profile with a very similar shape to that of liquid clouds but with lower maximum values during events with warm air above the planetary boundary layer. The normalized ice water content profiles in mixed-phase clouds look different from those of liquid water content. They show a wider range in maximum values with the lowest ice water content for clouds below an inversion and the highest values for clouds above or extending through an inversion. The ice water content profile generally peaks at a height below the peak in the liquid water content profile - usually in the centre of the cloud, sometimes closer to cloud base, likely due to particle sublimation as the crystals fall through the cloud.