Water resource availability is one of the primary limiting factors with regard to ecosystems in the western China. Having a clear understanding of multi-scale drought patterns in this region is a key step for adaption...Water resource availability is one of the primary limiting factors with regard to ecosystems in the western China. Having a clear understanding of multi-scale drought patterns in this region is a key step for adaption and mitigation to climate change. The Palmer drought severity index （PDSI） is a widely applied index to assess drought conditions. In this study, long-term monthly self-calibrated PDSI data from 1951 to 2012 were examined for drought spatiotemporal variations in the western China. The results clearly indicated that apparent spatial heterogeneities were evidenced between two sub-regions （arid land with annual precipitation less than 200 mm and semiarid land with annual precipitation between 200 to 500 mm） as well as in the entire region of the western China. Ensemble empirical mode decomposition （EEMD） analyses on monthly PDSI and other atmospheric variable time-series obtained from the Department of Civil and Environmental Engineering, Princeton University revealed that all monthly time-series of variables could be completely decomposed into eight intrinsic mode functions （IMFs） and a trend （residual）. This indicates that the monthly PDSI and atmospheric variables of the semiarid area in the western China contain eight quasi-period oscillations on various timescale spanning, seasonal to decadal cycles and a trend of a larger timescale from 1951-2012. The multi-scale drought patterns identified in this research could be powerful supports for decision-making regarding coping with droughts in this region.展开更多
Climate change investigation at a watershed-scale plays a significant role in re- vealing the historical evolution and future trend of the runoff variation in watershed. This study examines the multisource hydrologica...Climate change investigation at a watershed-scale plays a significant role in re- vealing the historical evolution and future trend of the runoff variation in watershed. This study examines the multisource hydrological and meteorological variables over the source area of the Yellow River （SAYR） from 1961 to 2,012 and the future climate scenarios in the region during 2006-2100 based on the CMIP5 projection data. It recognizes the significant charac-teristics of the recent climate change in the SAYR and predicts the change trend of future flow in the region. It is found that （1） The climate in the SAYR has experienced a significant warm-wet change since the early 2000s, which is very different from the antecedent warm-dry trend since the late 1980s; （2） The warm-wet trend in the northwestern SAYR （the headwater area of the Yellow River （HAYR）, is more obvious than that in the whole SAYR; （3） With pre- cipitation increase, the runoff in the region also experienced an increasing process since 2006. The runoff variations in the region are sensitive to the changes of precipitation, PET and maximum air temperature, but not very sensitive to changes in mean and minimum air temperatures; （4） Based on the CMIP5 projection data, the warm-wet climate trend in SAYR are likely to continue until 2049 if considering three different （i.e. RCP2.6, RCP4.5 and RCP8.5） greenhouse gas emission scenarios, and the precipitation in SAYR will not be less than the current level before 2100; however, it is estimated that the recent flow increase in the SAYR is likely to be the decadal change and it will at most continue until the 2020s; （5） The inter-annual variations of the East Asian winter monsoon are found to be closely related to the variations of annual precipitation in the region. Meanwhile, the increased precipitation as well as the increase of potential evapotranspiration （PET） being far less than that of precipitation in the recent period are the main climate causes for the flow increase in the region.展开更多
Based on the hydrological data in the headwater region of the Kaidu River during 1972-2011, the multifractal process of runoff fluctuation was analyzed. Results indicated that, in the past 40 years, the overall runoff...Based on the hydrological data in the headwater region of the Kaidu River during 1972-2011, the multifractal process of runoff fluctuation was analyzed. Results indicated that, in the past 40 years, the overall runoff of the Kaidu River in Xinjiang has shown significant multifractal behavior. Its singular curve 1nχq（ε）-1n（ε） verified a favorable scale invariance over the entire time scale, r（q）-q proved that evolution of the runoff time series presented multifractal characteristics. Moreover, the multifractal spectrumf（α）-α curve was hooklike leftward which indicated that, compared to relatively large runoff events. And △f〈0 indicated that these relatively small events took the leading role; B〈0 explained the Kaidu River＇s daily-runoff ascending tendency presented during 1972-2011. Besides that, the multifractal behavior of the Kaidu River＇s runoff variability over four decades was also analyzed. Generally speaking, by decades, their four corresponding spectrum variations were not noticeable. These △α values showed larger runoff events occupied the leading position with some local values falling. During the 1970s to the 1990s, △f〈0 illustrated the probability of the daily runoff at the lowest point is always larger than that of the highest during three continuous decades. At the beginning of the 21 st century, for △f〉0 the trend presented was contrary from the 1970s to the 1990s. B values suggested an overall trend of increases during 1972-2011. Until the 21 st century, the runoff with a slightly descending tendency on the whole explained these relatively large runoff events taking the leading role for the Kaidu River; but sometimes, some small events also played the dominant role.展开更多
基金supported by the National Basic Research Program of China(2012CB956204)the National Natural Science Foundation(41371364)
文摘Water resource availability is one of the primary limiting factors with regard to ecosystems in the western China. Having a clear understanding of multi-scale drought patterns in this region is a key step for adaption and mitigation to climate change. The Palmer drought severity index （PDSI） is a widely applied index to assess drought conditions. In this study, long-term monthly self-calibrated PDSI data from 1951 to 2012 were examined for drought spatiotemporal variations in the western China. The results clearly indicated that apparent spatial heterogeneities were evidenced between two sub-regions （arid land with annual precipitation less than 200 mm and semiarid land with annual precipitation between 200 to 500 mm） as well as in the entire region of the western China. Ensemble empirical mode decomposition （EEMD） analyses on monthly PDSI and other atmospheric variable time-series obtained from the Department of Civil and Environmental Engineering, Princeton University revealed that all monthly time-series of variables could be completely decomposed into eight intrinsic mode functions （IMFs） and a trend （residual）. This indicates that the monthly PDSI and atmospheric variables of the semiarid area in the western China contain eight quasi-period oscillations on various timescale spanning, seasonal to decadal cycles and a trend of a larger timescale from 1951-2012. The multi-scale drought patterns identified in this research could be powerful supports for decision-making regarding coping with droughts in this region.
基金The Key Deployment Project of the Chinese Academy of Sciences, No.Y322G73001 National Natural Science Foundation of China, No.91225302, No.91437217, No.41375022, No.41175027 Acknowledgments The TRMM data are provided by the NASA/Goddard Space Flight Center＇s Mesoscale Atmospheric Processes Laboratory and PPS, which develop and compute the TMPA as a contribution to TRMM. We acknowledge computing resources and time on the Supercomputing Center of Cold and Arid Region Environment and Engineering Research Institute of Chinese Academy of Sciences. We also acknowledge National Climate Center of China for collecting, analyzing and providing the data of the World Climate Research Programme＇s （WCRP＇s） the Fifth Phase of the Coupled Model Intercomparison Project （CMIP5）.
文摘Climate change investigation at a watershed-scale plays a significant role in re- vealing the historical evolution and future trend of the runoff variation in watershed. This study examines the multisource hydrological and meteorological variables over the source area of the Yellow River （SAYR） from 1961 to 2,012 and the future climate scenarios in the region during 2006-2100 based on the CMIP5 projection data. It recognizes the significant charac-teristics of the recent climate change in the SAYR and predicts the change trend of future flow in the region. It is found that （1） The climate in the SAYR has experienced a significant warm-wet change since the early 2000s, which is very different from the antecedent warm-dry trend since the late 1980s; （2） The warm-wet trend in the northwestern SAYR （the headwater area of the Yellow River （HAYR）, is more obvious than that in the whole SAYR; （3） With pre- cipitation increase, the runoff in the region also experienced an increasing process since 2006. The runoff variations in the region are sensitive to the changes of precipitation, PET and maximum air temperature, but not very sensitive to changes in mean and minimum air temperatures; （4） Based on the CMIP5 projection data, the warm-wet climate trend in SAYR are likely to continue until 2049 if considering three different （i.e. RCP2.6, RCP4.5 and RCP8.5） greenhouse gas emission scenarios, and the precipitation in SAYR will not be less than the current level before 2100; however, it is estimated that the recent flow increase in the SAYR is likely to be the decadal change and it will at most continue until the 2020s; （5） The inter-annual variations of the East Asian winter monsoon are found to be closely related to the variations of annual precipitation in the region. Meanwhile, the increased precipitation as well as the increase of potential evapotranspiration （PET） being far less than that of precipitation in the recent period are the main climate causes for the flow increase in the region.
基金supported by the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.201611319050)Science and Technology Project of Jiangxi Provincial Department of Education(No.GJJ161097)+4 种基金China Postdoctoral Science Foundation(No.2016M600515)Jiangxi Province Postdoctoral Science Foundation(No.2017KY48)the Open Research Fund of Jiangxi Province Key Laboratory of Water Information Cooperative Sensing and Intelligent Processing(2016WICSIP012)the Opening Fund of the Key Laboratory of Poyang Lake Wetland and Watershed Research(Jiangxi Normal University)Ministry of Education(No.PK2017002)
文摘Based on the hydrological data in the headwater region of the Kaidu River during 1972-2011, the multifractal process of runoff fluctuation was analyzed. Results indicated that, in the past 40 years, the overall runoff of the Kaidu River in Xinjiang has shown significant multifractal behavior. Its singular curve 1nχq（ε）-1n（ε） verified a favorable scale invariance over the entire time scale, r（q）-q proved that evolution of the runoff time series presented multifractal characteristics. Moreover, the multifractal spectrumf（α）-α curve was hooklike leftward which indicated that, compared to relatively large runoff events. And △f〈0 indicated that these relatively small events took the leading role; B〈0 explained the Kaidu River＇s daily-runoff ascending tendency presented during 1972-2011. Besides that, the multifractal behavior of the Kaidu River＇s runoff variability over four decades was also analyzed. Generally speaking, by decades, their four corresponding spectrum variations were not noticeable. These △α values showed larger runoff events occupied the leading position with some local values falling. During the 1970s to the 1990s, △f〈0 illustrated the probability of the daily runoff at the lowest point is always larger than that of the highest during three continuous decades. At the beginning of the 21 st century, for △f〉0 the trend presented was contrary from the 1970s to the 1990s. B values suggested an overall trend of increases during 1972-2011. Until the 21 st century, the runoff with a slightly descending tendency on the whole explained these relatively large runoff events taking the leading role for the Kaidu River; but sometimes, some small events also played the dominant role.
