适用于Ku波段雷达高度计海冰干舷高度反演的积雪校正方法  

Snow Correction Method for Sea Ice Freeboard Retrieval Applied to Ku Band Radar Altimeters

作　　者：张晰 赵全芳 孟俊敏 刘眉洁[3] ZHANG Xi;ZHAO Quan-fang;MENG Jun-min;LIU Mei-jie(College of Geomatics,Shandong University of Science and Technology,Qingdao 266590,Shandong Province,China;First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,Shandong Province,China;College of Physics,Qingdao University,Qingdao 266071,Shandong Province,China)

机构地区：[1]山东科技大学测绘科学与工程学院,山东青岛266590 [2]自然资源部第一海洋研究所,山东青岛266061 [3]青岛大学物理学院,山东青岛266071

出　　处：《海洋技术学报》2020年第2期1-9,共9页Journal of Ocean Technology

基　　金：国家重点研发计划资助项目(2018YFC1407203);国家自然科学基金资助项目(41976173);中欧国际合作龙计划资助项目(32292)。

摘　　要：工作在Ku波段的CryoSat-2和Sentinel-3A合成孔径雷达高度计是当前最先进的高度计。由于雷达回波信号的实际时间跟踪点较预设的时间跟踪点总发生偏移,而且Ku波段波长短,进行海冰探测时易受雪层干扰,造成雷达信号主散射面由海冰表面上移至雪层内,这两个因素都影响着海冰干舷高度的反演精度。针对这些问题,本文首先确定了CryoSat-2与Sentinel-3A雷达高度计反演北极海冰干舷高度的最优波形重跟踪阈值组合,然后分析了这两个Ku波段雷达信号的雪层穿透系数,发现Ku波段高度计的主散射面受雪层的影响显著,会高估海冰干舷高度。基于此,文中提出了一种改进的积雪校正方法,并以机载Operation IceBridge(OIB)为验证数据,将本文提出的方法与通用积雪校正法和欧洲空间局(European Space Agency,ESA)海冰干舷高度产品进行了对比验证。实验结果表明,本文提出的方法能够有效估计Ku波段电磁波穿透海冰表面积雪深度的比例系数,显著校正了通用积雪校正方法存在的高估海冰干舷高度的问题,提高了海冰干舷高度的估算精度。The CryoSat-2 and Sentinel-3A synthetic aperture radar altimeters operating at the Ku-band are the most advanced altimeters so far.However,Ku-band electromagnetic wave is easily affected by snow layer,which leads to strong microwave attenuation within the snow volume.These factors may affect the location of main scattering horizon,especially at Ku-band frequencies,shifting toward the snow layer from sea-ice surface.Therefore,the snow layer brings an additional uncertainty for ice freeboard and thickness retrieval.In order to solve these problems,Threshold First Maximum Retracker Algorithm(TFMRA)is used to retrieve sea ice freeboard.To obtain the optimal waveform retracking threshold combination,the accuracy of sea ice freeboard retrieved from CryoSat-2 and Sentinel-3A radar altimeter under 8 threshold combinations is analyzed in comparison with OIB sea ice freeboard.Then the radar penetration factor for CryoSat-2 and Sentinel-3A is calculated,which expresses the radar dominant scattering horizon in relation to the snow and ice surfaces.The results show that the snow cover can significantly change the dominant scattering horizon of radar echo.This leads to an overestimation for sea ice freeboard retrieval.Furthermore,an improved sea-ice freeboard retrieval method is proposed,which accounts for the radar penetration of snow layer.Finally,a comparison of the freeboard supplied in the classic ice freeboard method and ESA ice freeboard product to our method is shown in the paper.The results show that the improved method can effectively improve the accuracy of ice freeboard retrieval under snow cover,and has a good potential to improve the accuracy of sea ice thickness retrieval detection.

关 键 词：CryoSat-2 Sentinel-3A 波形重跟踪 海冰干舷高度 雷达穿透系数 积雪校正 

分 类 号：P731.15[天文地球—海洋科学]