Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements
Incidence of rough and irregular atmospheric ice particles from Small Ice Detector 3 measurements
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DOI：
10.5194/acp-14-1649-2014
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发表时间：
2013-09
影响因子：
6.3
通讯作者：
Z. Ulanowski;P. Kaye;E. Hirst;R. Greenaway;R. Cotton;E. Hesse;C. T. Collier
中科院分区：
文献类型：
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作者：
Z. Ulanowski;P. Kaye;E. Hirst;R. Greenaway;R. Cotton;E. Hesse;C. T. Collier
在冰和混合相云的辐射特性的背景下，了解冰晶的特性（例如尺寸、形状、凹度和粗糙度）至关重要。通过获取二维光散射图案而不是粒子图像，可以克服当前云探测器测量这些特性的局限性。这种模式是首次使用小冰探测器 3 (SID-3) 探测器在各种中纬度混合相云和卷云中进行多次飞行时在原位获得。使用多种图案纹理测量方法对图案进行分析，选择这些测量方法来揭示颗粒粗糙度或复杂性的大小。将检索到的粗糙度与实验室中一系列经过充分表征的测试颗粒获得的值进行比较。研究发现，典型的原位粗糙度与测试颗粒的较粗糙子集中的粗糙度相对应，有时甚至超出了实验室中发现的最极端值。在这项研究中，我们不区分小尺度、精细的表面粗糙度和大尺度晶体复杂性。相反，我们认为两者在光散射特性和原因方面可能具有相似的表现。总体而言，现场数据是一致的，以具有高度不规则或粗糙表面的冰粒为主。在卷云的生长区和升华区也发现了类似的粗糙度。发现粗糙度与晕圈比呈负相关，但与现场发现的其他热力学或微观物理性质无关。我们观察到，在清洁的海洋气团中形成的卷云的粗糙度比在受污染的大陆气团中形成的要略高。总体而言，与由更规则、光滑的冰晶形状组成的卷云相比，粗糙度和复杂性预计会导致短波云反射率增加。这些发现对通过气溶胶播种来改变气候以减少卷云覆盖和光学深度的建议提出了质疑，因为播种可能会导致短波反射率降低。
The knowledge of properties of ice crystals such as size, shape, concavity and roughness is critical in the con- text of radiative properties of ice and mixed-phase clouds. Limitations of current cloud probes to measure these proper- ties can be circumvented by acquiring two-dimensional light- scattering patterns instead of particle images. Such patterns were obtained in situ for the first time using the Small Ice Detector 3 (SID-3) probe during several flights in a variety of mid-latitude mixed-phase and cirrus clouds. The patterns are analysed using several measures of pattern texture, se- lected to reveal the magnitude of particle roughness or com- plexity. The retrieved roughness is compared to values ob- tained from a range of well-characterized test particles in the laboratory. It is found that typical in situ roughness corre- sponds to that found in the rougher subset of the test particles, and sometimes even extends beyond the most extreme values found in the laboratory. In this study we do not differentiate between small-scale, fine surface roughness and large-scale crystal complexity. Instead, we argue that both can have sim- ilar manifestations in terms of light-scattering properties and also similar causes. Overall, the in situ data are consistent, with ice particles with highly irregular or rough surfaces be- ing dominant. Similar magnitudes of roughness were found in growth and sublimation zones of cirrus. The roughness was found to be negatively correlated with the halo ratio, but not with other thermodynamic or microphysical properties found in situ. Slightly higher roughness was observed in cir- rus forming in clean oceanic air masses than in a continental, polluted one. Overall, the roughness and complexity are ex- pected to lead to increased shortwave cloud reflectivity, in comparison with cirrus composed of more regular, smooth ice crystal shapes. These findings put into question sugges- tions that climate could be modified through aerosol seeding to reduce cirrus cover and optical depth, as the seeding may result in decreased shortwave reflectivity.