Sugar, gravel, fish and flowers: Mesoscale cloud patterns in the trade winds
Sugar, gravel, fish and flowers: Mesoscale cloud patterns in the trade winds
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DOI：
10.1002/qj.3662
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发表时间：
2019-11
影响因子：
8.9
通讯作者：
B. Stevens;S. Bony;H. Brogniez;L. Hentgen;C. Hohenegger;C. Kiemle;T. L’Ecuyer;A. K. Naumann;H. Schulz;P. Siebesma;J. Vial;D. Winker;P. Zuidema
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文献类型：
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作者：
B. Stevens;S. Bony;H. Brogniez;L. Hentgen;C. Hohenegger;C. Kiemle;T. L’Ecuyer;A. K. Naumann;H. Schulz;P. Siebesma;J. Vial;D. Winker;P. Zuidema
描述了一项旨在观测下游行业浅云中尺度（20至2，000公里）组织模式的活动。从空间观察到的中尺度组织模式由12名训练有素的科学家主观定义和学习。对个人交流、学习和复制分类的能力进行了评价。对10年（2007/2008年至2016/2017年）北半球冬季月份（12月至2月）从48°W到58°W，10°N到20°N的900张卫星图像进行了分类。每一个场景都被六位科学家独立地标记为六种模式之一（其中一种是“无模式”）。四种模式的中尺度组织可以标记在一个可重复的方式，并标记糖，砾石，鱼和花。糖云由反射率低的小而低的云组成，砾石云沿着明显的阵风锋形成，鱼云是云的骨架网络（通常像鱼骨一样），而花云则是由层状云元素定义的圆形团块特征。鱼和花都被大面积的清新空气所包围。这四种命名的模式在40%的时间内被识别出来，最常见的模式是Gravel。糖被确定为最少，并表明无组织和非常浅的对流不太可能主导下游信风的大面积。有些模式显示出季节和年际变化的迹象，以及一定程度的规模选择性。典型模式与雷达图像的比较表明，即使是这种主观和定性的视觉检查图像似乎捕捉到几个重要的物理差异之间的浅云制度，如降水和辐射效应。
An activity designed to characterise patterns of mesoscale (20 to 2,000 km) organisation of shallow clouds in the downstream trades is described. Patterns of mesoscale organisation observed from space were subjectively defined and learned by 12 trained scientists. The ability of individuals to communicate, learn and replicate the classification was evaluated. Nine‐hundred satellite images spanning the area from 48°W to 58°W, 10°N to 20°N for the boreal winter months (December–February) over 10 years (2007/2008 to 2016/2017) were classified. Each scene was independently labelled by six scientists as being dominated by one of six patterns (one of which was “no‐pattern”). Four patterns of mesoscale organisation could be labelled in a reproducible manner, and were labelled Sugar, Gravel, Fish and Flowers. Sugar consists of small, low clouds of low reflectivity, Gravel clouds form along apparent gust fronts, Fish are skeletal networks (often fishbone‐like) of clouds, while Flowers are circular clumped features defined more by their stratiform cloud elements. Both Fish and Flowers are surrounded by large areas of clear air. These four named patterns were identified 40% of the time, with the most common pattern being Gravel. Sugar was identified the least and suggests that unorganised and very shallow convection is unlikely to dominate large areas of the downstream trade winds. Some of the patterns show signs of seasonal and interannual variability, and some degree of scale selectivity. Comparison of typical patterns with radar imagery suggests that even this subjective and qualitative visual inspection of imagery appears to capture several important physical differences between shallow cloud regimes, such as precipitation and radiative effects.