中文摘要：

湖泊透明度是湖泊水体性质的一个重要参数,是湖泊浮游生物和进入湖泊的有机和无机颗粒溶解程度的综合反映,对湖泊生态环境研究具有重要的科学及实践意义。遥感影像是获取面积广、时间长的湖泊透明度的重要手段,但由于实测数据缺乏,目前对青藏高原地区湖泊透明度的遥感反演研究相对不足。本文基于青藏高原地区24个湖泊实测透明度SD（Secchi Depth）值和相应的MODIS遥感影像,建立了该地区湖泊水体透明度SD值MODIS遥感反演模型。结果表明：基于MODIS绿色波段B4的单波段幂函数模型在该地区反演效果最好,精度较高（R2=0.91,N=24）,并具有较好的稳定性。以当惹雍错为例,选用该模型反演得到湖泊透明度的时间变化序列,发现该湖存在明显的季节波动和较为明显的年际变化。初步分析得出,降水/融水季节的湖泊透明度与湖泊所在流域的降水率具有密切的关系。本文结果表明,利用遥感手段能够有效地开展青藏高原地区湖泊透明度的反演,可为进一步深入研究该地区湖泊透明度及其影响要素奠定基础。

英文摘要：

Lake water clarity is an important parameter of lake water property, which is an integrated response of lake plankton and organic and inorganic solutions, and has significant scientific and practical implications for lake ecological condition research. Remote sensing is a key method for obtaining lake clarity in wide areas and within long time spans. On the Tibetan Plateau, there are more than 389 lakes with area greater than 10 km2,making the Plateau an ideal region for environmental and climate change research. However, study on the estimation of lake water clarity on the Tibetan Plateau by satellite data is insufficient at present due to the paucity of in situ lake water clarity measurement data. In this study, retrieval models of lake water clarity were established based on the in situ water clarity measurements of 24 lakes distributed in different areas on the Tibetan Plateau and the corresponding MODIS imageries. Statistical methods including linear, exponential,power function, and logarithm regressions were used to build relationships between lake water clarity and the reflectance of MODIS bands on the Tibetan Plateau. The results show that power function model with MODIS green band B4 as single independent variable is the best model for estimating lake water clarity（SD value） on the Plateau（R~2=0.91, N=24）. The stability of the model was also tested based on 10 in situ SD data at different times in a single lake. Based on this model, we analyzed the temporal variation of lake water clarity of a typical lake Tangra Yumco as an example. The result demonstrates clear seasonal and inter-annual variations of lake water clarity for this lake. Preliminary analysis indicates that the variation of water clarity in precipitationmeltwater rich season is correlated with precipitation intensity of the basin. Our work proved that the reflectance of remote sensing imageries is valid for estimating lake water clarity on the Tibetan Plateau. This may promote further investigation of lake water clarity and its infl