摘要
利用1993年1月份的SSM/I亮度温度数据反演了青藏高原的雪水当量,首先使用被动微波SSM/I数据19和37GHz的水平极化数据来反演雪深,根据积雪时间的函数来计算实时的雪密度,由雪的深度和密度计算出雪水当量.最后,利用SSM/I数据的19和37GHz的垂直极化亮度温度梯度对计算出的雪水当量进行回归分析,得到了利用SSM/I数据直接反演雪水当量的算法.
Snow depth and snow water equivalent are the most import factors in the hydrologic model and climate model. So far, there is not an operational algorithm to estimate the snow water equivalent from passive microwave remote sensing data (SSM/I) in the Tibetan Plateau. In this study the SSM/I brightness temperature data in January 1993 are used to estimate the snow water equivalent SWE in the plateau. The frequencies of SSM/I data used to retrieve snow depth are 19 and 37 GHz in horizontal polarization. The results show that all available algorithms overestimate the snow depth in the Tibetan Plateau. In this paper the reasons of overestimation of snow depth from several aspects are analyzed, such as the water content of snow pack, large water bodies (e.g. lakes), and the abnormal field snow depth data. After eliminating some futile data (including the passive microwave brightness temperature values and snow depth data in the weather stations), an improved algorithm has been established to retrieve the snow depth from the difference of 19 and 37 GHz brightness temperatures in horizontal polarization. Here, snow density is obtained by a time function of fresh snow density. The snow depth and density were converted to the snow water equivalent, and are regarded as the ground truth. In finally, the TB vertically polarized differences of 19 and 37 GHz are regressed with the SWE. Using the statistical method, a simple and practical algorithm is developed to estimate the snow water equivalent from the differences of 19 and 37 GHz in vertical polarization.
出处
《冰川冻土》
CSCD
北大核心
2004年第3期363-368,共6页
Journal of Glaciology and Geocryology
基金
国家自然科学基金项目(90202014
49971060)资助
关键词
被动微波遥感
雪水当量
SSM/I数据
snow water equivalent
passive microwave
remote sensing
SSM/I data
Tibetan Plateau
