SAR与高分辨率光学遥感联合反演雪水当量

Snow Water Equivalent (SWE) is a key parameter for hydrological applications in cold and arid regions. It can be estimated effectively using microwave remote sensing technology. However, the spatial resolution of current spaceborne passive microwave sensors is too coarse to provide useful information at regional and drainage basin scales. On the other hand, active microwave sensors, especially Synthetic Aperture Radar (SAR), have been used to estimate snow properties, such as SWE, because of its significant sensitivity to snow parameters and fine resolution. But there is not yet a practical model for retrieving SWE. Combining SAR data with high spatial resolution multispectral remotely sensed images, this proposal aims to develop a practical and effective method to retrieve SWE by taking advantages of penetration property in microwave spectrum and reflective properties in visible and near-infrared ones. A flat area in Sanchakou in the midstream of Manasi River, located in the north slope of Tianshan Mountains, is chosen to take situ measurements for analyzing the microwave scattering properties of snowpack in various snow statuses and underground conditions. Satellite snow cover estimation based on Bayes' theorem is proposed to discriminate between dry and wet snow. SAR and multispectral remote sensing is integrated to improve the precision of SWE retrieval based on EQeau model, and to investigate the spatial and temporal characteristics of SWE. The expected achievements may be regarded as a theoretic reference in SWE retrieval at regional scale, and applied in snowmelt runoff simulation and forecast, especially in snow water utilization and management.

雪水当量是寒区流域水文研究中的重要参数，利用微波遥感可以估算大面积的雪水当量，但是被动微波遥感的空间分辨率较低，而主动微波遥感反演雪水当量仍处于理论研究阶段。本项目利用星载合成孔径雷达（SAR）的穿透能力和光学遥感的高分辨率、多光谱特性，联合SAR与光学遥感数据开展高分辨率雪水当量反演的关键技术研究。以天山北坡玛纳斯河中游三岔口平坦样地为研究区，在分析不同状态、不同下垫面积雪的微波散射特性的基础上，提出联合SAR和高分辨率光学遥感数据估算卫星雪盖的贝叶斯模型；并利用无雪期和积雪期的后向散射系数差值与积雪热阻差值的关系，建立研究区的雪水当量反演模型；最后利用估算的卫星雪盖范围对雪水当量反演结果进行交叉订正，获取高分辨率的雪水当量空间分布和时间变化信息。研究成果对流域尺度的雪水当量反演具有理论参照意义，对融雪径流模拟与预报、积雪水资源利用与管理具有实际应用价值。

雪水当量是寒区流域水文研究中的重要参数，利用微波遥感可以估算大面积的雪水当量，但是被动微波遥感的空间分辨率较低，而主动微波遥感反演雪水当量仍处于理论研究阶段。以新疆天山北坡玛纳斯河流域为研究区，联合SAR与光学遥感数据开展高分辨率雪水当量反演的关键技术研究。在多次实地考察与地面同步观测基础上，通过充分发挥SAR与光学遥感数据的互补性，研究并建立了一套完整的基于SAR与光学遥感数据联合识别积雪的模型方法，消除了光学遥感数据识别积雪受云的限制，克服了SAR数据识别积雪受地形的影响，实现了山区积雪的表面类型和干湿状态的同时识别。基于地面实测数据，验证了利用C波段SAR数据和EQeau模型反演山区雪水当量的有效性与可行性，解决了山区地形与下垫面条件下EQeau模型的参数优化与反演过程改进的技术难题，最终反演得到研究区高精度的雪水当量分布信息。研究成果对流域尺度的雪水当量反演具有理论参照意义，对融雪径流模拟与预报、积雪水资源利用与管理具有实际应用价值。