天山中段非均匀下垫面雪水当量被动微波遥感研究

Surface water resources in arid zones are mainly derived from rain and snowmelt of mountain. The simulation and evaluation of snowmelt is one of research focuses of water resources in recent years. Estimation of snow water equivalent from remote sensing is important to estimate mountainous water resources in arid areas where have sparse weather stations. Using optical radiation data, snow extent is generally felt to be obtained reliably, but snow water equivalent is less confidence due to the band limited and cloud affected. At present, passive microwave remote sensing is the most efficient way to derive snow properties, but its spatial resolution is relatively low. This project intends to study snow water equivalent from passive microwave data in inhomogeneous land surface taking the central of Tianshan in China as a case. This paper takes field observations, MODIS, AMSR-E and MVRI as data source. The relations between terrains and snow physical properties (snow grain size, density, stratigraphy, snow temperature and temperature at the snow/soil interface) will be obtained based on long-term field experiments a priori. In considering of the spatial resolution merit of visible band, the fusion methods of passive microwave and optical data will be constructed. The estimation methods of snow depth will be modified for complex land surface. The dynamic retrieval model of snow depth based on the temperature gradient index will be built and its applicability will be evaluated. Then, the theory and methodology will be finally established for retrieving snow water equivalent of non-uniform underlying surface with passive microwave remote sensing. The reliably estimation of the snow water equivalent can improve the accuracy of the snowmelt-runoff prediction and the management of the water supply.

干旱区典型河流近40%水资源来自山区融雪水，山区融雪水模拟与评估是近年水资源的热点之一，雪水当量遥感估算则是干旱区稀缺站点的山区水资源模拟的重要发展方向之一。研究表明：光学遥感对积雪面积反演效果较好，但受到成像波段限制和云的影响，估算的雪水当量存在一定局限性；微波遥感的穿透能力对雪水当量估算有很大优势，而其空间分辨率较低。本项目利用前期建设的天山山区观测站点，在非均匀下垫面与积雪物理特性内在关系观测实验的基础上，改进积雪深度计算方法，构建温度梯度指数的积雪深度遥感动态反演模型，结合MODIS、AMSR-E和MWRI遥感信息，尝试光学-被动微波融合反演山区雪水当量，分析研究雪水当量的时空变化规律，为新疆天山雪水资源评估和冰雪水文模拟提供参考依据。

干旱区典型河流近40%水资源来自山区融雪水，山区融雪水模拟与评估是近年水资源的热点之一，雪水当量遥感估算则是干旱区稀缺站点的山区水资源模拟的重要发展方向之一。项目利用前期建设的天山山区观测站点，开展多次天山山区积雪特性野外实验, 验证分析了FY3B-MWRI业务化算法和Chang算法在天山山区地区的雪深反演误差。构建了基于地形效应的微波辐射模型和基于下垫面的天山山区积雪深度反演模型，提出了基于地形校正的山区积雪深度反演算法；分析了天山山区积雪深度时空变化规律；结果表明：1)天山山区积雪分布在伊犁地区、巴音布鲁克草原以及玛纳斯河流域等天山中段地区，总体趋势表现为自西向东、自北向南减少。2）天山山区积雪深度空间分布呈自西向东、由北向南减少的趋势，与降水分布特征相似。3）在研究时段，研究区的最大深度在空间分布上总体趋势变化不大，以天山山脊线为界，在天山南、北以及中段皆形成高雪深区域。4）地势起伏度与积雪深度呈负相关，地势起伏度越大，积雪深度越小；5）降尺度模型经过参数优化和修订后与野外实测数据相关性较高，变化趋势一致，误差较小。6） 降水比土地面积对陆地水储量影响更大，气温和风速是影响中亚积雪日数的气候因子。地形对中亚积雪的变化及分布特征的也有一定影响，各高程带的积雪随着海拔的升高而减小，不同坡度的积雪面积与坡度呈反相关关系；不同坡向的积雪差异较大。