冰雷达与卫星测高协同的南极冰下湖遥感识别研究

Subglacier lakes in Antarctic are an unknown world for mankind, and one of last important scientific advanced fields on the earth. On the basis of ice radar data from public website and Chinese Antarctic Expedition along the transect from Zhongshan station to Dome A, they are preprocessed by band-pass filtering. The relationship between dielectric features of ice, water and basal rock of subglacier lakes and reflectance signal of ice radar is analyzed in order to extract waveform characteristics and shape information, and this information is cross-validated. The signal thresholds of interface between ice and water, and interface between ice and basal rock are confirmed, and classification criteria system of subglacier lakes is established in order to identify them. The subglacier lakes parameters, including length along the transects, ice sheet thickness above the subglacier lakes, depth, salinity, surrounding basal rock topography and geographic location, are obtained. Cryosat-2 altimeter data in the same region is corrected, filtered, interpolated in order to calculate the elevation and generate the digital elevation model, and minimize the errors. The surface slopes of ice sheet above subglacier lakes are calculated, and topographic features are analyzed. The area and volume are estimated on the basis of the integration of ice radar data and the existent digital elevation model of basal rock under the ice sheet. With the help of GIS technology, the subglacier lakes are inventoried, and the subglacier database with attribute and spatial information are established. All parameters of subglacier lakes are systematically evaluated and compared, and a suitable and potential Antarctic subglacier lake is selected in order to prepare in advance for drilling and comprehensive research of China.

南极冰下湖是人类的未知领域，是地球上最后的重要科学前沿领域之一。以已公开的和中国南极科学考察队的冰雷达数据为基础，先进行带通滤波等预处理，分析冰下湖的冰、水、基岩介电特性与冰雷达反射信号之间的关系，抽取反射信号波形特征与形态信息，并进行交叉验证，确定冰水界面、冰岩界面的反射信号阈值，建立冰下湖的分类准则体系，并识别冰下湖。获取测线方向湖泊长度、上覆冰盖厚度、深度、盐度、周围基岩地形条件以及地理位置等信息。同时对相应的Cryosat-2测高数据进行纠正、滤波、插值处理与高程解算，生成数字高程模型，并进行误差修正；计算冰下湖上覆冰盖表面坡度，分析地形特征，结合冰雷达数据和已有的冰盖底部数字高程模型，估算冰下湖的面积和体积。在GIS技术的支持下，建立包含属性和空间信息的冰下湖数据库。综合评估、比对多种冰下湖参数，并选择合适的冰下湖，为中国的南极冰下湖钻探和系统研究做前期准备。

南极冰下湖是人类的未知领域，是地球上最后的重要科学前沿领域之一。1）冰雷达数据处理与冰下湖的识别和分类。收集到的冰雷达数据包括Cresis、Ice bridge、AGAP、以及中国南极科学考察队获取的中山站至Dome A断面冰雷达数据，开展了数据的有效性检查、带通滤波和纵向差分等预处理。进行了冰下湖的冰、水、基岩介电特性与冰雷达反射信号之间的关系研究。经过系列实验，确定了冰水界面、冰岩界面等反射信号的阈值，抽取了反射信号波形特征、形态信息，并对不同反射界面、不同频率雷达反射信号进行了对比与交叉验证研究。根据测线方向雷达反射信号的强弱、波形特征和阈值建立了冰下湖的分类准则体系，进而识别了大部分冰下湖。对于确定的冰下湖进一步全面分析其雷达反射信号，获取测线方向湖泊长度、上覆冰盖厚度、湖泊深度、盐度、周围基岩地形条件以及地理位置等。2）卫星测高数据处理与冰下湖参数提取。对Cryosat-2测高数据进行了有效性检查、无效和冗余数据的剔除等预处理。并对测高数据进行了系统误差的纠正，并解算出了高程。开展了滤波与空间插值等处理，生成了数字高程模型，并与已有的数字高程模型进行了交叉验证、对比。同时参照其他高度计数据，进行了误差的评估和修正。分析了已确定冰下湖的上覆冰盖表面地形特征，计算了坡度，验证了具备似镜面的平坦地形特征。同时根据卫星测高数据获取的平坦地形范围的大小，结合冰雷达获取的冰下湖测线方向地形和已有的冰盖底部数字高程模型综合估算了冰下湖的面积和体积。3）冰下湖编目。在GIS技术的支持下，建立了包含地理位置、周围基岩地形条件、上覆冰盖厚度、长度（冰雷达测线方向）、深度、面积、体积等属性和空间信息的冰下湖数据库。综合评估、比对多种冰下湖参数，并选择合适的冰下湖，可以为中国的南极冰下湖钻探和系统研究做前期准备。