The dynamics of high-altitude inland lakes in the Tibetan Plateau are sensitive indicators of climate change. Due to the remoteness and hard access, satellite altimetry becomes an effective approach to obtaining large...The dynamics of high-altitude inland lakes in the Tibetan Plateau are sensitive indicators of climate change. Due to the remoteness and hard access, satellite altimetry becomes an effective approach to obtaining largescale and temporally continuous information of lake-level changes. The CryoSat-2 altimetry is expected to solve the current problem that earlier radar altimeters are only practical for monitoring large water bodies, while ICESat laser altimetry is available only for the period 2003-2009. In this study, the comparison of CryoSat-2 altimetry for Namco with in situ water-level data suggests a high cor- relation coefficient of 0.71 （P 〈 0.01）, with the mean error of -0.12 m and root-mean-square error of 0.18 m. Further, the combination of ICESat and CryoSat-2 altimetry data and in situ lake-level observations reveals a rapid water- level rise of 0.24 4- 0.04 m/year during 2003-2008 and then a slightly decreasing trend of -0.09 4- 0.04 m/year during 2009-2013. This study suggests that the CryoSat-2 altimetry has the potential of sustaining the fine observa- tions on Tibetan lakes, following the ICESat mission. Besides, the examination of four key climatic variables （temperature, precipitation, potential evapotranspiration, and relative humidity） during 1990-2013 indicates that the wetting climate over Namco Basin stagnated or even reversed around 2006, which may be tightly related to the slowing lake growth.展开更多
China＇s government statement recently reported the plan of constructing Xiong＇an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with t...China＇s government statement recently reported the plan of constructing Xiong＇an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with the priority in eco-environmental protection. The New Area is located in the semi-arid North China Plain （NCP） and is home to NCP＇s largest natural freshwater wetland, Baiyangdian Lake. A comprehensive realization of surface water dynamics would be crucial for policy-makers to outline a sustainable environment development strategy for New Area. In this study, we used a total of 245 time slices of cloud-free Landsat images to document the continuous changes of water bodies within Xiong＇an City dur- ing 1984-2016 and to provide detailed evidence of water presence and persistency states and changes under the influences of climate change and human actions. Our results reveal that the New Area water body areas varied dramatically during the past 33 years, ranging from 0.44 km^2 in April 1988 to 317.85 km^2 in February 1989. The change of surface water area was not characterized by a monotonically decreasing tendency. The evolution processes can be divided into four sub-stages： the first extreme desiccation in mid-1980s, the wet stage with the most extensive inundation areas and strong inter-annual fluctuations from late-1988 to late 1999, another desiccation stage in early 2000s, and the overall recovering stage between 2007 and 2016. We also mapped the maximum water inundation extents and frequencies of all-season, pre-wet season （February-May） and post-wet season （September-December） for the 33 years and different sub-periods. Although there is good agreement between time series of surface water area evolution in the New Area and station-based precipitation and evaporation variations, multipie lines of evidences reviewed in previous research indicate that the degraded Baiyangdian Lake was also tightly associated with human activities from various aspects, including dam construction, g展开更多
Dams and reservoirs play an essential role in regulating and managing water resources.Since the middle of the 20th century,the growing demand for water and hydropower has led to an unprecedented boom in reservoir cons...Dams and reservoirs play an essential role in regulating and managing water resources.Since the middle of the 20th century,the growing demand for water and hydropower has led to an unprecedented boom in reservoir construction worldwide[1,2].Meanwhile,reservoir construction has also resulted in a variety of ecological and socioeconomic impacts[3–5].Reservoirs transform natural flow regimes into conditions favored by human demand.The associated flow regulations,especially in reservoirs constructed in recent decades(e.g.,after 2000)with greater seasonal variability[6,7],represent a strong human-induced alteration of the hydrologic cycle.As reservoir construction continues to boom in many parts of the world,an up-to-date and openaccess inventory of reservoirs worldwide remains critically desired.展开更多
Synthesis of multi-satellite altimetry facilitates the acquisition of long-term changes in lake level but may induce biases due to inconsistent data sources,and thus remains largely unexplored.This study investigates ...Synthesis of multi-satellite altimetry facilitates the acquisition of long-term changes in lake level but may induce biases due to inconsistent data sources,and thus remains largely unexplored.This study investigates the integrated application of Ice,Cloud,and land Elevation Satellite(ICESat),ICESat-2,and CryoSat-2 missions to provide consecutive lake level series in 2003–2020.The sample comprises 48 lakes in the world with gauge-based or Hydroweb water level data.The CryoSat-2 data arefirst adjusted to the ICESat-2 height reference based on the mean values of their monthly water level difference during their overlapping period(2018–2020).Then,the corrected CryoSat-2 data are used to link the ICESat and ICESat-2 data.Results show that in the sample lakes,the deviations between CryoSat-2 and ICESat-2 data vary and range from-0.78 m to 0.13 m.The data quality of the synthesized time series is evaluated by comparing against the validation data,with an average R^(2) of 0.84.This study shows that CryoSat-2 has the potential offilling the gap between ICESat and ICESat-2.The three altimeters can be expected to integrate effectively for monitoring lake water level changes in the past two decades.展开更多
The pan-Arctic region has the largest number of lakes in the world,which is rather sensitive to changing climate.It is urgently needed to understand how these lakes were changing in the long term.However,there are few...The pan-Arctic region has the largest number of lakes in the world,which is rather sensitive to changing climate.It is urgently needed to understand how these lakes were changing in the long term.However,there are few lakes with long-term historical monitoring of water level,understanding the hydrologic changes of pan-Arctic lakes over the past century requires the data reconstruction by state-of-art techniques.This study used machine learning algorithms to reconstruct the water level of pan-Arctic lakes on a centennial scale.It further investigated their relationship with long-term hydrological and climatic variables.Comparison of the reconstructed results by four different machine learning models shows that the extreme gradient boosting tree(XGBoost) is better than other three models.Overall,the centennial-scale reconstruction using the XGBoost model performs best for most study lakes.Based on the reconstructed results,we can observe that water level changes of several North American lakes are correlated with potential evapotranspiration,followed by precipitation,while the Eurasian lakes are more strongly associated with temperature and wet day frequency.The water level dynamics of pan-Arctic lakes could be largely attributed to Arctic Oscillation and Atlantic Multidecadal Oscillation.This study is expected to advance our understanding of the pan-Arctic lake water level changes in the past century and to provide a feasible method for reconstructing the regional lake water level in the long term.展开更多
基金supported by the National Special Basic Research Project of the Ministry of Science and Technology(2013FY111400-2,2009CB723901)the National Natural Science Foundation of China(41120114001,41125003,41071254,40971048)+3 种基金the European Space Agency(ESA AO 2605)the Knowledge Innovation Foundation Program for outstanding Young Scholar of Chinese Academy of Sciences(CAS)(KZCX2-EWQN104)supported by Open Research Fund of Key Laboratory of Tibetan Environmental Changes and Land Surface Processes in Chinese Academy of SciencesOpen Fund of State Key Laboratory of Remote Sensing Science
文摘The dynamics of high-altitude inland lakes in the Tibetan Plateau are sensitive indicators of climate change. Due to the remoteness and hard access, satellite altimetry becomes an effective approach to obtaining largescale and temporally continuous information of lake-level changes. The CryoSat-2 altimetry is expected to solve the current problem that earlier radar altimeters are only practical for monitoring large water bodies, while ICESat laser altimetry is available only for the period 2003-2009. In this study, the comparison of CryoSat-2 altimetry for Namco with in situ water-level data suggests a high cor- relation coefficient of 0.71 （P 〈 0.01）, with the mean error of -0.12 m and root-mean-square error of 0.18 m. Further, the combination of ICESat and CryoSat-2 altimetry data and in situ lake-level observations reveals a rapid water- level rise of 0.24 4- 0.04 m/year during 2003-2008 and then a slightly decreasing trend of -0.09 4- 0.04 m/year during 2009-2013. This study suggests that the CryoSat-2 altimetry has the potential of sustaining the fine observa- tions on Tibetan lakes, following the ICESat mission. Besides, the examination of four key climatic variables （temperature, precipitation, potential evapotranspiration, and relative humidity） during 1990-2013 indicates that the wetting climate over Namco Basin stagnated or even reversed around 2006, which may be tightly related to the slowing lake growth.
基金funded by the Thousand Young Talents Program in China(Y7QR011001)National Natural Science Foundation of China(41501445,41771366)+2 种基金Program of Provincial Natural Science Foundation of Anhui(1608085QD77)Program of Nanjing Institute of Geography and Limnology(NIGLAS2016TD01)funded by the United States Geological Surveying(USGS)Landsat Science Team Program Grant(G12PC00071)
文摘China＇s government statement recently reported the plan of constructing Xiong＇an New Area, which aims to phase out some extra capital functions from Beijing and to explore an innovative urban development mode with the priority in eco-environmental protection. The New Area is located in the semi-arid North China Plain （NCP） and is home to NCP＇s largest natural freshwater wetland, Baiyangdian Lake. A comprehensive realization of surface water dynamics would be crucial for policy-makers to outline a sustainable environment development strategy for New Area. In this study, we used a total of 245 time slices of cloud-free Landsat images to document the continuous changes of water bodies within Xiong＇an City dur- ing 1984-2016 and to provide detailed evidence of water presence and persistency states and changes under the influences of climate change and human actions. Our results reveal that the New Area water body areas varied dramatically during the past 33 years, ranging from 0.44 km^2 in April 1988 to 317.85 km^2 in February 1989. The change of surface water area was not characterized by a monotonically decreasing tendency. The evolution processes can be divided into four sub-stages： the first extreme desiccation in mid-1980s, the wet stage with the most extensive inundation areas and strong inter-annual fluctuations from late-1988 to late 1999, another desiccation stage in early 2000s, and the overall recovering stage between 2007 and 2016. We also mapped the maximum water inundation extents and frequencies of all-season, pre-wet season （February-May） and post-wet season （September-December） for the 33 years and different sub-periods. Although there is good agreement between time series of surface water area evolution in the New Area and station-based precipitation and evaporation variations, multipie lines of evidences reviewed in previous research indicate that the degraded Baiyangdian Lake was also tightly associated with human activities from various aspects, including dam construction, g
基金supported by the National Key Research and Development Program of China(2022YFF0711603)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23100102,XDA19090120)+3 种基金the National Natural Science Foundation of China(42371399,42301431)the Science and Technology Planning Project of NIGLAS(2022NIGLAS-CJH04,2022NIGLAS-TJ18)supported by the NASA Surface Water and Ocean Topography(SWOT)Science Team(80NSSC20K1143)supported by the CNES TOSCA program of research for his role as PI of the Surface Water and Ocean Topography(SWOT)mission。
文摘Dams and reservoirs play an essential role in regulating and managing water resources.Since the middle of the 20th century,the growing demand for water and hydropower has led to an unprecedented boom in reservoir construction worldwide[1,2].Meanwhile,reservoir construction has also resulted in a variety of ecological and socioeconomic impacts[3–5].Reservoirs transform natural flow regimes into conditions favored by human demand.The associated flow regulations,especially in reservoirs constructed in recent decades(e.g.,after 2000)with greater seasonal variability[6,7],represent a strong human-induced alteration of the hydrologic cycle.As reservoir construction continues to boom in many parts of the world,an up-to-date and openaccess inventory of reservoirs worldwide remains critically desired.
基金supported by the National Key Research and Development Program of China[grant numbers 2022YFF0711603,2019YFA0607101]the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDA23100102]+1 种基金Science and Technology Planning Project of NIGLAS[grant numbers 2022NIGLAS-CJH04,2022NIGLAS-TJ18]the National Natural Science Foundation of China[grant numbers 41971403,41930102,42171421 and 41975036].
文摘Synthesis of multi-satellite altimetry facilitates the acquisition of long-term changes in lake level but may induce biases due to inconsistent data sources,and thus remains largely unexplored.This study investigates the integrated application of Ice,Cloud,and land Elevation Satellite(ICESat),ICESat-2,and CryoSat-2 missions to provide consecutive lake level series in 2003–2020.The sample comprises 48 lakes in the world with gauge-based or Hydroweb water level data.The CryoSat-2 data arefirst adjusted to the ICESat-2 height reference based on the mean values of their monthly water level difference during their overlapping period(2018–2020).Then,the corrected CryoSat-2 data are used to link the ICESat and ICESat-2 data.Results show that in the sample lakes,the deviations between CryoSat-2 and ICESat-2 data vary and range from-0.78 m to 0.13 m.The data quality of the synthesized time series is evaluated by comparing against the validation data,with an average R^(2) of 0.84.This study shows that CryoSat-2 has the potential offilling the gap between ICESat and ICESat-2.The three altimeters can be expected to integrate effectively for monitoring lake water level changes in the past two decades.
基金jointly funded by the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA23100102)the National Key Research and Development Program of China (Nos.2018YFD0900804,2018YFD1100101,and 2019YFA0607101)the National Natural Science Foundation of China (Nos.41971403,41801321,and 42101402)。
文摘The pan-Arctic region has the largest number of lakes in the world,which is rather sensitive to changing climate.It is urgently needed to understand how these lakes were changing in the long term.However,there are few lakes with long-term historical monitoring of water level,understanding the hydrologic changes of pan-Arctic lakes over the past century requires the data reconstruction by state-of-art techniques.This study used machine learning algorithms to reconstruct the water level of pan-Arctic lakes on a centennial scale.It further investigated their relationship with long-term hydrological and climatic variables.Comparison of the reconstructed results by four different machine learning models shows that the extreme gradient boosting tree(XGBoost) is better than other three models.Overall,the centennial-scale reconstruction using the XGBoost model performs best for most study lakes.Based on the reconstructed results,we can observe that water level changes of several North American lakes are correlated with potential evapotranspiration,followed by precipitation,while the Eurasian lakes are more strongly associated with temperature and wet day frequency.The water level dynamics of pan-Arctic lakes could be largely attributed to Arctic Oscillation and Atlantic Multidecadal Oscillation.This study is expected to advance our understanding of the pan-Arctic lake water level changes in the past century and to provide a feasible method for reconstructing the regional lake water level in the long term.
