Improvement of cloud detection near sunrise and sunset by temporal-differencing and region-growing techniques with real-time SEVIRI
Improvement of cloud detection near sunrise and sunset by temporal-differencing and region-growing techniques with real-time SEVIRI
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DOI：
10.1080/01431160902926632
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发表时间：
2010-03
影响因子：
3.4
通讯作者：
M. Derrien;H. Le Gléau
中科院分区：
文献类型：
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作者：
M. Derrien;H. Le Gléau
欧洲气象卫星利用组织 (EUMETSAT) 通过临近预报卫星应用设施 (SAFNWC) 提供了一个软件包，适合生成来自第二代气象卫星 (MSG) 卫星上的旋转增强型可见光和红外成像仪 (SEVIRI) 的实时产品。云掩模是其主要衍生产品之一。使用动画循环对该软件 v2008 版本的行为进行分析表明，在昼夜过渡附近的低云检测中存在不连续性。因此，当场景包含此类条件时，它的使用可能会产生负面影响。我们的研究为更顺畅的连续性提供了解决方案。结果表明，时间差分技术与区域生长技术相结合可以改善昼夜过渡区域的低层云量检测，但代价是误报的小幅增加。描述并说明了该方法和由此产生的改进。对表面天气观测 (SYNOP) 中报告的欧洲上空云量统计数据和从 SEVIRI 检索到的、有增强和没有增强的欧洲上空云量统计数据进行比较，估计错过云的频率减少了 50%，而误报率仅略有增加。与另一个 EUMETSAT 运行的基于 SEVIRI 的云掩模的比较证实了所提出的技术在倾斜太阳角度下的有用性。
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), through the Satellite Application Facility for Nowcasting (SAFNWC), provides a software package suitable to generate real-time products derived from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite. A cloud mask is one of its key derived products. An analysis of the behaviour of version v2008 of this software using animation loops indicates a discontinuity in the detection of low clouds near the day–night transition. Thus, its use may have a negative impact when the scene includes such conditions. Our study provides solutions for a smoother continuity. It shows that a temporal-differencing technique combined with a region-growing technique can improve low-level cloudiness detection in the day–night transition area at the expense of a small increase of false alarms. The method and the resulting improvement are described and illustrated. A comparison of statistics of the cloudiness over Europe reported in Surface Synoptic Observations (SYNOP) and retrieved from the SEVIRI with and without the enhancement estimates a decrease of 50% of the frequency of missed clouds while the false alarm ratio increases only marginally. A comparison with another EUMETSAT operational SEVIRI-based cloud mask confirms the usefulness of the proposed technique at oblique sun angles.