Observed and modelled cloud cover up to 6 km height at Station Nord in the high Arctic,International Journal of Climatology

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Observed and modelled cloud cover up to 6 km height at Station Nord in the high Arctic
International Journal of Climatology ( IF 3.5 ) Pub Date : 2020-10-16 , DOI: 10.1002/joc.6894
Sven‐Erik Gryning ₁ , Ekaterina Batchvarova _{1,

2} , Rogier Floors ₁ , Christoph Münkel ₃ , Henrik Skov ₄ , Lise Lotte Sørensen ₄

Affiliation

We present results from an analyses of cloud cover based on profiles of the attenuated backscatter coefficient from an 8‐year‐long data series (July 2011–April 2019). The observations are carried out in the high Arctic by a ceilometer with a maximum range setting of 7.7 km from the Villum Research Station at Station Nord, Greenland. Results show that the hourly cloud cover turned out to follow a U‐shaped rather than Gaussian‐like distribution. Annual and seasonal cloud cover variation is illustrated. The cloud cover is larger during the autumn and winter as compared to summer and spring. The cloud cover exhibits a substantial variation from year to year without a clear trend. The cloud cover during spring is low and decreasing between 2012 and 2017. The cloud cover during the autumn of 2016 is lowest compared to the other years. The observed cloud cover is compared to the cloud cover provided in the ERA5 reanalysis dataset. The cloud cover for low clouds and medium clouds are combined to represent a total height of 6 km. Both the observed and modelled cloud cover is larger during winter as compared to summer‐time cloud cover. The measured reduction in the cloud cover for the autumn of 2016 is present in the reanalysis data as well but the measured low cloud cover during spring is not apparent in the reanalysis data. Because the cloud cover distribution is U‐shaped rather than of a Gaussian nature, standard metrics are not applicable. We apply a generalized skill score that is developed for contingency tables or joint histograms. Three skill scores were calculated. It was found that for all three methods, skills for the predictability of the cloud cover by the ERA5 modelling is better for winter than summer and is poor during the spring.

中文翻译：

在北极高空的北站，观测到并建模的云层最高可达6 km

我们基于8年数据系列（2011年7月至2019年4月）的衰减后向散射系数曲线，介绍了对云量的分析结果。观测是在高海拔北极地区用云高仪进行的，云高仪距格陵兰北站维拉姆研究站的最大范围设置为7.7公里。结果表明，每小时的云量实际上呈U型而不是高斯型分布。说明了年度和季节性云量变化。与夏季和春季相比，秋季和冬季的云量更大。每年的云量变化很大，没有明显的趋势。春季的云量较低，在2012年至2017年之间呈下降趋势。与其他年份相比，2016年秋季的云量最低。将观察到的云层与ERA5重新分析数据集中提供的云层进行比较。低云和中云的云量总和为6 km。与夏季的云量相比，冬季观测和建模的云量都更大。重新分析数据中也显示了2016年秋季测得的云量减少，但是在春季期间测得的低云量在重新分析数据中并不明显。因为云量的分布是U形而不是高斯性质，所以标准指标不适用。我们应用针对列联表或联合直方图开发的通用技能得分。计算了三个技能得分。发现对于这三种方法，

更新日期：2020-10-16

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