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青藏高原是地球上海拔最高的地理單元,平均海拔超過4000米,連同周邊的高大山脈被稱為地球的「第三極」。青藏高原擁有的冰川儲量僅次於南極、格陵蘭地區及加拿大。高原也是亞洲幾大主要水系的發源地,因而被譽為亞洲「水塔」。在高原腹地的寬谷有密集的湖泊群,其中面積大於1km²的湖泊超過1000個,以內流湖為主。其湖泊面積占中國湖泊總面積的50%左右。陸地水儲量及年際動態是全球水量平衡的重要組成部分,但是在高緯度的青藏高原地區由於缺乏精細的觀測,還存在諸多疑問。因而,針對青藏高原地區,採用新的觀測手段和方法調查高寒水文系統中冰川和湖泊所引起的水儲量變化對理解全球水分平衡和氣候變化影響十分必要。本研究將利用多種遙感衛星觀測系統回答高原水文研究中存在的一些關鍵問題。 / 青藏高原自上世紀八十年代出現快速升溫,從多方面的研究以達成共識。然而,由於資料的不確定性及高原地區降雨本身的空間異質性,降雨的時空變化尚存在不一致的結論。本研究對八種常用的降雨產品的時空相關性進行相互比較,也採用有限的網站觀測對格網降雨資料集進行評價。結果顯示,GPCP, CMAP-1, CMAP-2和PREC/L四個降雨資料集與網站觀測降雨具有更好的相關性,APHRODITE 和TRMM資料次之,兩個再分析降雨資料最不相關。基於GPCP, CMAP-1, PREC/L和APHRODITE降雨資料,分析青藏高原及周邊地區降雨在1979 - 2011期間的變化趨勢。四個資料集一致反映在高原中部及東北部地方,降雨在上世紀90年代開始出現明顯的增長趨勢,在藏東南地區降雨減少,但趨勢不明顯。而在喜馬拉雅地區,四個降雨資料反映的趨勢不一致。本研究進一步分析降雨對青藏高原地區陸地水儲量的在2003 - 2011期間的影響關係發現,高原中部及東北部的降雨增加及天山地區的降雨減少與GRACE衛星觀測的陸地水儲量變化有十分密切的關係。而在喜馬拉雅山脈及藏東南地區,降雨的變化對陸地水儲量的相關性相對較低,一方面可能是降雨資料在該地區由於更複雜的地形具有更大的不確定性,另外一方面,可能存在其他氣候因素(如變暖引起的冰川融水損失等)影響陸地水量的平衡。 / 因此,選擇藏東南地區為研究典型區,調查青藏高原冰凍圈水文系統的陸地水儲量平衡狀態及其與冰川變化關係。利用2003 - 2009時段內GRACE衛星觀測,藏東南地區的物質平衡以5.99 ± 2.78 Gt/yr的速率減少。然而,基於GLDAS/Noah和CPC的模型輸出資料進行分析發現,該地區的土壤含水量、雪水當量及植被冠層含水量等水文因數均無顯著的降低(或增加)趨勢。而根據ICESat測高衛星對藏東南地區冰川的表面高程進行測量得出,冰川在2003 - 2009期間以平均- 0.31 ± 0.14 m/yr的速率消融,相當於- 4.83 ± 2.46 Gt/yr的負物質平衡量。可以推斷,冰川消融引起的水量流失大約能解釋該地區80%的GRACE衛星觀測的物質負平衡量。進一步分析GRACE衛星連續觀測的區域陸地水儲量平衡與氣候因數的統計關係表明,時間序列中的突變、季節性波動及多年週期振盪信號與降水的變化具有高度的相關性,而區域物質平衡的年際收支及長期趨勢更明顯受溫度的控制。該結論進一步證實藏東南地區近年來的陸地水儲量負平衡很大程度上由增加冰川融水流失引起的。 / 在青藏高原內陸湖泊水文研究方面,由於缺乏長期的湖泊水量平衡、水位及湖底地形等實測資料,大尺度定量估算湖泊水量變化的難題一直尚未解決。上世紀70年代以來的光學遙感影像及2003 - 2009期間的ICESat衛星測高資料成為大尺度觀測青藏高原湖泊面積及水位變化的有力工具。遙感觀測結果表明,整個高原湖泊(選取312個大於10 km²的湖泊)面積從1970年代早期的35,638.11 km²增加到2011年的41,938.66 km²。ICESat測高資料覆蓋的湖泊平均水位變化速率為0.23 m/yr。其中,青藏高原中部地區的湖泊,如色林錯,擴張速度最快,而藏南地區的湖泊在2000年代出現迅速萎縮趨勢。基於2003 - 2009期間的湖泊面積及對應的水位資料,建立湖泊水位隨面積變化的統計關係,從而重建湖泊在缺少ICESat測高資料的時段(2003年之前及2009年之後)的湖泊水位資料,有效估算青藏高原湖泊從1970年代約40年來水量增加92.43 Gt (主要增長髮生在2000年代)。對湖泊群密集的羌塘高原湖泊水量平衡進一步分析,該地區湖泊水量在2000年代以6.79 Gt/yr的速率增加,該類比結果與GRACE觀測的該地區物質正平衡趨勢6.81 Gt/yr十分接近。 / 為了解釋青藏高原地區內陸湖泊在2000年代迅速擴張的主要氣候影響機制,針對117個具有測高資料,分析其湖泊水位的趨勢、突變及季節性變化與氣候變數的關係。結果表明,高原湖泊水位的季節性變化表現明顯的時空異質性:昆侖山南部的密集的小湖泊群在暖(濕)季水位降低,而冷(幹)季水位增加,可能更多依賴于季節性雪蓋融水補給,而暖季該地區強烈蒸發作用造成水量負平衡;其他大部分湖泊暖季由於降水徑流補給水位升高,而冷季水位降低或較小地波動。根據水位季節性變化和突變,湖泊可以劃分為8個聚類,不同聚類表現出不同的水位變化態勢,一些明顯的水位增減與該地區降水和蒸發高低密切相關,而冰川融水補給(表現為溫度波動)並未表現出顯著的相關性。將高原範圍內的湖泊劃分為冰川補給型與非冰川補給型湖泊,兩類湖泊群的水位變化在統計上沒有明顯分異。而水位變化速率與湖泊的補給係數(一定程度上反映湖泊降水徑流對水量平衡的影響)具有顯著相關。從不同的氣候子區具體分析,在高原中部地區,冰川融水補給確實更加加劇了降水引起的湖泊水位增長。此外,集成多顆衛星的測高資料,對18個高原典型大湖泊的水位年際增量與氣候因數進行相關分析發現,水位波動呈現出與降水和蒸發更顯著的相關性。總之,該研究綜合多種新型技術手段,在大尺度上調查青藏高原高寒水文系統(主要針對季風型溫性冰川與內陸湖泊)水量變化及其空間異質性特徵,並解釋其氣候影響因素。 / The Tibetan Plateau (TP) and surrounding mountains are known as the Third Pole, with an average elevation of 4,000 meters above sea level. It holds the largest reserves of glacier ice outside of Antarctica, Greenland, and Canada. It is thus referred as Asian water towers, which form the source of more than ten major rivers in Asia. In the broad basins of the inner plateau, there are more than one thousand lakes, mostly featured by closed watersheds. In the context of climate change and variability, regional terrestrial water storage (TWS) budgets of the TP are critical terms in the global water balance, yet they are poorly observed at high altitude. Thus new strategies are required to investigate changes of mountain glaciers and lakes in the high-altitude hydrologic system. Multiple remote sensing techniques are deployed here to address questions in high-latitude hydrology. / The temperature of the TP has risen rapidly since the 1980s, but spatio-temporal variability of precipitation remains unclear partly due to more spatial incoherence in precipitation variation. Eight gridded precipitation datasets are inter-compared with each other and evaluated by gauge-based data over the TP and surroundings between 1979 and 2011. The results show that the GPCP, CMAP-1/2 and PREC/L precipitation data agreebetter with gauge-based precipitation. The two reanalysis data have the weakest correlations with gauge-based data, and the APHRODITE and TRMM data are in between. Analyses of precipitation trends based on the GPCP, CMAP-1, PREC/L and APHRODITE datasets consistently reveal that an obvious increase is observed in the inner TP since the mid-1990s and insignificant decreasing trends areobserved in the southeastern TP. In the Himalayas, the precipitation trends are rather inconsistent among the four datasets. Comparisons of the GRACE TWS changes and precipitation variability between 2003 and 2011 show that increasing precipitation in the central and northeastern TP and decreasing precipitation in the Tienshan Mountains are tightly associated with the TWS variations in the two regions. However, there are relatively lower correlations between TWS changes and precipitation in the Himalayas and southeastern TP. It implies that there areprobably other factors (such as glacier meltwater loss induced by warming climate) which are also correlated with the GRACE-observed mass changes. / The southeastern TP (SETP) is selected as a demonstrative area to investigate the TWS changes in the cryo-hydrologic system and relations with glacier variations. The GRACE observations during 2003 - 2009 reveal a serious mass loss with rate of - 5.99 ± 2.78 Gt/yr in the SETP. Based on hydrological data by model calculations from the GLDAS/Noah and CPC, other hydrologic elements, including soil moisture, snow water equivalent and canopy water storage, showed no obvious change trends. The glacier measured by the ICESat altimetry showed a thinning rate of - 0.31 ± 0.14 m/yr during 2003 - 2009. An approximate estimation of the glacier mass budget was - 4.83± 2.46 Gt/yr, which accounted for ~ 80% of the GRACE-observed mass loss in this area. The further examinationon climate forces of TWS changes in the SETP suggest that abrupt, seasonal and multi-year undulating signals of GRACE TWS anomaly time series were tightly associated with precipitation variability, while the annual mass budgets and trends were more related to temperature variability. / In contrast to glacial meltwater loss in outflow areas of the SETP, the hydrological processes in the inner TP are characterized by closed lake systems. In-situ measurements of lake water balance and lake bathymetry are missing to monitor the TWS changes in lake-hydrologic system of the TP. Remote sensing allows observation of area and water level variations in Tibetan lakes (312 lakes larger than 10 km²). The total lake area increased from 35,638. 11km² in the early-1970s to 41,938.66 km² in 2011. The mean rate of change in water level for all examined lakes was 0.23 m/yr between 2003 and 2009. The most dramatic lake expansion was observed in the central TP. Lakes in South Tibet showed shrinking tendency in the past decade. Then, based on the time series of lake area and water level, the statistical relationships between lake area and water level are established to estimate lake water volume (storage) variations and compare with GRACE-observed mass gains in this area. The results show that the total water storage increased by 92.43 Gt (km³) from the early 1970s to 2011.The positive water mass budget of 6.81 Gt/yr in the Changtang Plateau derived from GRACE data agrees well with the change rate of lake water storage (6.79 Gt/yr) derived from the statistical models in the 2000s. / Based on satellite altimetry data, the trends, abrupt and seasonal changes of water level for 117 lakes with elevation measurements are examined to explore the potential climate forces of lake variations in the 2000s. Results suggest that seasonal water-level variations were featured by strong spatio-temporal heterogeneity which was largely associated with the seasonally and spatially varied climate. The rates of change of non-glacier-fed lakes in the 2000s were basically as high as those of glacier-fed lakes across the plateau while the lake level changes were closely associated with the lake supply coefficients (the basin / lake area ratio, which partly indicates the role of precipitation and runoff on lake water balance). The lake variations agreed well with the spatial pattern of precipitation changes.In addition, the correlation analyses between water level variations and climatic variables for 18 typical large lakes indicate that lake dynamics were more related to precipitation and evaporation than temperature. In sum, this study provides new insight and large-scale investigation on high-altitude hydrologic systems of the TP. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Song, Chunqiao. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 181-203). / Abstracts also in Chinese.