青藏高原上坐落著眾多冰河與湖泊，由於地勢高聳、環境險峻且人煙稀少，故在過往研究中曾被證實能提早反映氣候變遷。過去幾十年來，隨著溫度升高以及降水和蒸發散的改變，這些高山湖泊的水位也與此呈現高度正相關之震盪，因此，透過監測青藏高原的湖水位變化能夠了解氣候變遷對環境造成的影響。由於現地資料取得不易，從1980年代開始，衛星遙測技術的應用便成了資料蒐集的良好工具，然而，目前多半研究都著重在湖泊面積的變化，亦或是短期的湖水位監測，因此，本研究希望能夠利用Landsat影像和SRTM數值高程模型的結合，對青藏高原上所有面積大於10平方公里的湖泊進行長達30年的湖水位監測。 本研究方法主要辨識各張衛星影像中湖泊邊界並將其和SRTM數值高程模型套和進而估算水位高程，如此便能建立出長時間序列來觀測季節性以及年際水位變化，我們更計算了從1989到2019年湖泊的面積及水量變化，本研究總共完成了385口湖泊並將結果和ICESat雷射測高衛星以及Sentinel-3雷達測高衛星做比較，根據資料點介於五天之內的數據結果顯示，兩者之標準差為0.6公尺，相關係數約為0.6，結果顯示，從1989到2019年間青藏高原上湖泊的總體水量約增加了216 (Gt)，此外，如同過往研究所呈現，青藏高原湖泊的年際水位變化和溫度、降水以及蒸發量息息相關，且有空間上區域分佈的特徵。 ;Alpine lakes on the Tibetan Plateau (TP) are the indicators of global climate change as their altitude is sensitive to the atmospheric forcing. In the last four decades, hundreds of lakes experienced a strong spatiotemporal variability along with the rising temperature, changing precipitation, and faster evaporation as revealed by the in-situ record. Lake level and water volume are thus a good proxy to identify environmental effects of the climate change. Due to the remoteness and wideness, satellite remote sensing has become the primary choice for data collection since the 1980s. However, most of hydrological evidences so far only revealed either the change of lake extent or short-term water level variation using limited sensors. Therefore, this study aims to build a historical water level time series in a time span of 30 years, for lakes larger than 10 km2 on TP using satellite optical images and SRTM digital elevation model (DEM). The Thematic Imagery Altimetry System (TIAS) approach is used to identify the boundary of water bodies in each image and co-register with SRTM to estimate lake level through hypsometry. Hence, a multidecadal time series can be formed to observe the change of hydrological regimes from seasonal to decadal epochs. We also calculate the lake area/volume variation between 1989 and 2019. A total of 385 lakes are analyzed and compared with ICESat laser altimetry in 2003–2009 and Sentinel-3 radar altimetry from 2016 till now. The standard deviation between TIAS and the altimetry satellites (ICESat and Sentienl-3) equals to 0.6 m and the correlation coefficient is 0.6 while matching the temporally coincident (<5 days) water levels. The result shows that the overall lake volume from 1989 to 2019 increase about 216 Gt. Besides, the interannual variability of lakes over TP are associated with temperature and precipitation rate in different geographical regions, as mentioned in previous studies.
