摘要:
利用我国自主研制的风云二号静止气象卫星资料,结合地面自动气象站能见度资料,通过对大量不同时相卫星资料的试验分析,找出台湾海峡海雾、云以及晴空海表等典型下垫面的可见光、热红外和中红外3个通道的光谱特征和变化规律,在此基础上运用反射率阈值实现云雾与海洋表面的自动分离,用亮温阈值实现海雾和低云与中高云的自动分离,用中红外和热红外通道的归一化差值指标实现夜间海雾的自动识别,最后建立台湾海峡海雾自动监测业务软件系统,并选择2015年和2016年地面实测资料对遥感监测结果进行精度验证.研究结果表明:风云静止卫星逐时海雾产品能有效地弥补极轨卫星在监测时次上的不足,很好地为台湾海峡海雾动态监测业务提供数据支持;遥感监测结果与地面观测结果相吻合,总体上较为理想,海雾监测平均准确率白天超过70%,但夜间判识精度低于白天;但同时风云静止卫星遥感技术在海雾和低云的有效分离方面仍然存在局限性.
Abstract:
In this paper,the authors analyzed the variation law of visible light, thermal infrared band and mid-infrared band of FY geostationary satellite for sea fog,clouds and sea surface (clear sky) in Taiwan Strait, which was based on a lot of experimental analyses by using different phases of satellite data,combined with the visibility data of automatic meteorological stations. On such a basis, reflectivity threshold was used to separate sea fog and cloud from sea surface, and brightness temperature threshold was used to separate sea fog and low cloud from middle and high cloud. In addition,night sea fog was automatically identified by the normalized difference index of mid-infrared and thermal infrared band. Finally,the automatic monitoring software system of Taiwan Strait sea fog was established,and surface observation data were used to examine the precision of remote sensing monitoring. The research results show that FY geostationary satellite could make up for the deficiency of Polar Orbit Satellite in time resolution,and it has a good performance on the dynamic monitoring service of Taiwan Strait. A comparison shows that the remote sensing monitoring results of sea fog are in accordance with observation results,and the monitoring accuracy is more than 70% in daytime. Night time accuracy is lower than that of the day time, and there exists limitation in the separation of sea fog and low cloud.
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