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首页> 外文期刊>Atmospheric Measurement Techniques >Ice crystal characterization in cirrus clouds: a?sun-tracking camera system and automated detection algorithm for halo displays
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Ice crystal characterization in cirrus clouds: a?sun-tracking camera system and automated detection algorithm for halo displays

机译：卷云中的冰晶特征：太阳跟踪摄像机系统和光环显示的自动检测算法

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Halo displays in the sky contain valuable information about ice crystal shape and orientation: e.g., the 22°?halo is produced by randomly oriented hexagonal prisms while parhelia (sundogs) indicate oriented plates. HaloCam, a?novel sun-tracking camera system for the automated observation of halo displays is presented. An initial visual evaluation of the frequency of halo displays for the ACCEPT (Analysis of the Composition of Clouds with Extended Polarization Techniques) field campaign from October to mid-November 2014 showed that sundogs were observed more often than 22°?halos. Thus, the majority of halo displays was produced by oriented ice crystals. During the campaign about 27?% of the cirrus clouds produced 22°?halos, sundogs or upper tangent arcs. To evaluate the HaloCam observations collected from regular measurements in Munich between January 2014 and June 2016, an automated detection algorithm for 22°?halos was developed, which can be extended to other halo types as well. This algorithm detected 22°?halos about 2?% of the time for this dataset. The frequency of cirrus clouds during this time period was estimated by co-located ceilometer measurements using temperature thresholds of the cloud base. About 25?% of the detected cirrus clouds occurred together with a?22°?halo, which implies that these clouds contained a?certain fraction of smooth, hexagonal ice crystals. HaloCam observations complemented by radiative transfer simulations and measurements of aerosol and cirrus cloud optical thickness (AOT and COT) provide a?possibility to retrieve more detailed information about ice crystal roughness. This paper demonstrates the feasibility of a?completely automated method to collect and evaluate a?long-term database of halo observations and shows the potential to characterize ice crystal properties.
机译：天空中的光晕显示包含有关冰晶形状和方向的有价值的信息：例如，22°？光晕是由随机定向的六边形棱柱产生的，而白千层（太阳狗）则表示定向的板。介绍了HaloCam，这是一种用于自动观察光环显示的新型太阳跟踪摄像机系统。从2014年10月至2014年11月中旬，对ACCEPT（使用扩展偏振技术对云的成分进行分析）野外活动的光环显示频率进行了初步的视觉评估，结果表明，观察到的太阳狗比22°晕更常见。因此，大多数光环显示是由定向的冰晶产生的。在战役期间，大约27％的卷云产生了22°晕，日光照射或上切线弧。为了评估2014年1月至2016年6月在慕尼黑定期测量中收集的HaloCam观测值，开发了针对22°晕圈的自动检测算法，该算法也可以扩展到其他晕圈类型。对于该数据集，该算法检测到22°？halos的时间约为2％。卷积云在该时间段内的频率是通过使用云母的温度阈值通过共置云高仪测量来估算的。大约25％的探测到的卷云与22°α晕一起出现，这意味着这些云中包含一定比例的光滑六方冰晶。 HaloCam观测结果辅以辐射传输模拟以及气溶胶和卷云光学厚度（AOT和COT）的测量，为检索有关冰晶粗糙度的更详细信息提供了可能。本文展示了一种完全自动化的方法来收集和评估晕圈观测的长期数据库的可行性，并展示了表征冰晶特性的潜力。

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