基于卫星升降轨X/C/L波段SAR影像监测贡嘎山冰川分布及其动态演变

The glacier ablation of the mountains in the western part of China is considered as a prominent problem. As the glacial retreats are ongoing around the Gongga Mountain (the National Nature Reserve Zone) in the Sichuan Province of China, it is very important to monitor the kinematic evolution process of glaciers in the study area. In view of the challenging task of tracking the glaciers in the Gongga Mountain usually covered by clouds and fogs, this research project intends to develop the theory and methods for monitoring alpine glaciers with use of X/C/L-band SAR images collected by different satellites along their ascending and descending orbits. The primary strategies are provided here. By analyzing backscattering characteristics and interferometric coherence of the glacial targets with use of multi-band SAR images, we will propose the methods of identifying glaciers and extracting their outlines and relevant parameters. By integrating three approaches, i.e., differential interferometric SAR (DInSAR), multi-aperture interferometry (MAI) and pixel offset tracking (POT), we will establish the model of glacial displacement velocity field (GDVF) and its solution method. By using the multi-band SAR images collected in different time periods, we will also extend the long-term time series (LTTS) InSAR method for tracking and inversing the long-term displacements in the selected typical glacial bodies. The primary research contents of this project include analysis of backscattering characteristics and detection of targets with steady reflection, analysis of interferometric coherence and identification of glacial bodies, the DInSAR-MAI-POT model and method for extracting GDVF, and the LTTS-InSAR method for monitoring the long-term glacial displacements. The objective of this project is to improve the accuracy, reliability and spatiotemporal resolution in monitoring the distribution of alpine glaciers and their kinematic evolution, thus providing the strong technological support for monitoring the various alpine glaciers in the western part of China.

我国西部高山冰川消融问题十分突出，属于国家级自然保护区的四川贡嘎山冰川普遍出现退缩现象，及时开展该区域内冰川的动态演变监测与分析至关重要。顾及多云雾天气条件下贡嘎山冰川监测难题，本项目将针对基于卫星升降轨X/C/L波段SAR影像的冰川监测理论与方法展开研究。其基本思路是：开展卫星升降轨多波段SAR冰川目标散射特性和干涉相关分析，提出冰川识别及其边界和相关参数的提取方法；融合卫星升降轨差分干涉、多孔径干涉和像素偏移跟踪方法提取冰川位移速度场；扩展融合多卫星平台SAR影像的长时序InSAR模型与方法，对典型冰川的长时序位移进行监测与反演。本项目将重点针对冰川散射特性分析及散射稳定目标探测、干涉相关分析与冰川识别、冰川位移速度场建模与求解、长时序InSAR冰川位移建模与解算等方面展开研究，旨在提高冰川分布及其动态演变监测的精度、可靠性与时空分辨率，为我国西部高山冰川监测提供重要的技术支撑。

近些年来，全球气候变暖背景下我国藏东南地区冰川呈加速退化的趋势。然而，受季风的影响，藏东南地区暖季无云遮挡的光学遥感影像极其匮乏，制约着这一地区冰川的常态化监测。顾及多云雾天气条件下的冰川监测难题，本项目选取青藏高原东南缘贡嘎山地区的冰川作为研究区域，基于卫星升降轨X/C/L波段SAR影像针对冰川监测的理论与方法开展研究。已完成的主要研究内容包括：开展了冰川目标雷达散射特性和干涉相关分析，提出了冰川识别及其边界和相关参数的提取方法；提出了融合卫星升降轨差分干涉和像素偏移跟踪方法的冰川位移速度场提取方法；扩展了融合多卫星平台SAR影像的长时序InSAR模型与方法，并对典型冰川的长时序位移进行了监测与反演。.在冰川识别方面，课题组提出了联合振幅离差指数和干涉相干系数的RAC模型，旨在增强冰川和毗邻地物的对比度，从而降低冰川分类的难度并提高边界提取的精度。在流速场监测方面，课题组基于POT技术提出了融合升降轨的三维时序流速场解算方法，并融合多源SAR影像开展了贡嘎山东西坡长时间序列冰川流速的动态演化监测。结果表明，贡嘎山冰川在近十年间流速减缓显著，其中海螺沟冰川和贡巴冰川流速减缓率分别为15.57%/a和4.21%/a，均高于藏东南地区冰川的平均水平。.作为该项目研究的扩展，课题组借助地基雷达对海螺沟冰川末端的次生滑坡进行了高时间分辨率的持续监测，揭示了该滑体与冰川活动高相关性的滑移规律。在无人机遥感影像生产的DOM和DSM基础上，课题组发展了现有光学遥感匹配技术，并开展了冰川三维流速及冰面消融的研究。在项目的研究过程中，课题组发表了科研论文27篇，其中SCI论文16篇。申请了国家发明专利10项、软件著作权2项，并培养了研究生20余名。本项目研究成果提高了冰川分布及动态演化监测的精度、可靠性与时空分辨率，可为我国西部高山冰川监测提供重要的技术支撑。