基于Radarsat-2 SAR图像分类与HY-2微波辐射计反演获取北极海冰密集度的比较研究

COMPARISONS OF ARCTIC SEA ICE CONCENTRATIONS OBTAINED BY CLASSIFICATION OF RADARSAT-2 SYNTHETIC APERTURE RADAR IMAGERY AND RETRIEVALS FROM HY-2 SCANNING MICROWAVE RADIOMETER

在北极东北航道东西伯利亚海和楚科奇海交汇的关键区域,利用四景2012年北极夏季Radarsat-2 SAR海冰图像,通过图像分类提取了海冰密集度;同时采用NASA TEAM算法,基于海洋二号(HY-2)卫星扫描微波辐射计亮温数据反演了对应区域的海冰密集度;并引入美国冰雪数据中心(NSIDC)发布的SSMIS海冰密集度产品进行了对比研究。通过不同来源海冰密集度数据的分析发现HY-2、SAR和SSMIS的结果在4个研究区域上的分布趋势基本吻合;但在海冰边缘区,由SAR图像分类得到的海冰密集度高于HY-2和SSMIS的反演结果,说明了高分辨率的SAR图像在监测边缘区小尺寸浮冰上有优势。三种数据中,原始分辨率相同(25 km)的HY-2与SSMIS的结果最为相近,而HY-2同SAR的相关性与SAR同SSMIS的相关性一致。在冰边缘,HY-2的反演值偏低于SAR和SSMIS的结果,这是受该处较高水汽含量影响的结果,也是未来发展HY-2微波辐射计反演算法需要重点改进的地方。

In the region where the East Siberia Sea and the Chukchi Sea join at the Arctic Northeast Passage,four Radarsat-2 synthetic aperture radar（ SAR） images were used to obtain the sea ice concentration（ SIC） through image classification. The NASA TEAM algorithm was employed to retrieve the SIC in the corresponding area based on the brightness temperature data of the scanning microwave radiometer onboard the satellite HY-2. The SIC product of the Special Sensor Microwave Imager / Sounder（ SSMIS） released by the Nation Snow and Ice Data Center was used for comparison. An analysis of the SIC revealed that the SIC distribution trends obtained by the SAR images and the SSMIS were in agreement. In the marginal ice zone（ MIZ）,the SIC derived from the SAR imagery was higher than that retrieved from HY-2 and the SSMIS,implying that SAR imagery is advantageous when observing small ice floes in the MIZ. Of the three data sources,the SIC retrievals of HY-2 were closest to the SSMIS because they had the same initial spatial resolution（ 25 km）,and the correlation between the HY-2 and SAR results was similar to that between the SSMIS and SAR results. However,in the ice edge,the retrievals of HY-2 were lower than the SAR and SSMIS results. This was caused by the high water vapor concentration in the air at the ice edge; this issue should be addressed when improving the retrieval algorithm of the HY-2 microwave radiometer in the future.