This paper utilizes a modified Water Accounting Model （WAM） to track the moisture sources of an extreme precipitation event in Shandong during 18-20 July 2007. It is found that different methods in dealing with the ...This paper utilizes a modified Water Accounting Model （WAM） to track the moisture sources of an extreme precipitation event in Shandong during 18-20 July 2007. It is found that different methods in dealing with the residual of the water budget always produce different results in moisture recycling calculations. In addition, results from the backward tracking without the residual are in complete agreement with those from the forward tracking with the residual, and vice versa, implying a mathematical consistency. We thus analyze and derive the conditions under which the two tracking approaches equate with each other. We applied the backward tracking to the Shandong extreme rainfall case and obtained quantitative estimates of moisture contributions of three selected regions away from the rainfall area. The results indicate that the spatial pattern rather than numerical value of the recycling moisture is more reliable in tracking the moisture sources. The moisture of this Shandong rainfall event comes mostly from the nearby upwind area in Southwest China, which is of the terrestrial origin; while the moisture originating from the neighboring West Pacific contributes little to this event.展开更多
Stable water isotopes are natural tracers quantifying the contribution of moisture recycling to local precipitation,i.e.,the moisture recycling ratio,but various isotope-based models usually lead to different results,...Stable water isotopes are natural tracers quantifying the contribution of moisture recycling to local precipitation,i.e.,the moisture recycling ratio,but various isotope-based models usually lead to different results,which affects the accuracy of local moisture recycling.In this study,a total of 18 stations from four typical areas in China were selected to compare the performance of isotope-based linear and Bayesian mixing models and to determine local moisture recycling ratio.Among the three vapor sources including advection,transpiration,and surface evaporation,the advection vapor usually played a dominant role,and the contribution of surface evaporation was less than that of transpiration.When the abnormal values were ignored,the arithmetic averages of differences between isotope-based linear and the Bayesian mixing models were 0.9%for transpiration,0.2%for surface evaporation,and–1.1%for advection,respectively,and the medians were 0.5%,0.2%,and–0.8%,respectively.The importance of transpiration was slightly less for most cases when the Bayesian mixing model was applied,and the contribution of advection was relatively larger.The Bayesian mixing model was found to perform better in determining an efficient solution since linear model sometimes resulted in negative contribution ratios.Sensitivity test with two isotope scenarios indicated that the Bayesian model had a relatively low sensitivity to the changes in isotope input,and it was important to accurately estimate the isotopes in precipitation vapor.Generally,the Bayesian mixing model should be recommended instead of a linear model.The findings are useful for understanding the performance of isotope-based linear and Bayesian mixing models under various climate backgrounds.展开更多
Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the we...Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the westerlies and Indian summer monsoon(ISM) systems and to improve our understanding on the mechanisms of water resource changes in the ‘Asian Water Tower' under climate changes. Based on a Eulerian moisture tracking model(WAM-2) and three atmospheric reanalysis products(ERA-I, MERRA-2, and JRA-55), the contributions of moisture sources to the precipitation in six major sub-basins in the TP were tracked during an approximately 35-year period(1979/1980–2015). The results showed that in the upper Indus(UI),upper Tarim River(UT), and Qaidam Basin(QB), the moisture sources mainly extended westward along the mid-latitude westerlies to the western part of the Eurasian continent. In contrast, in the Yarlung Zangbo River Basin(YB), inner TP(ITP), and the source area of three eastern rivers(TER, including the Nujiang River, Lancang River, and Yangtze River), the moisture sources extended both westward and southward, but mainly southward along the ISM. In winter and spring, all of the sub-basins were dominated by western moisture sources. In summer, the western sources migrated northward with the zonal movement of the westerlies, and simultaneously the southern sources of the YB, ITP, and TER expanded largely toward the Indian Ocean along the ISM. In autumn, the moisture sources of the UI, UT, and QB shrank to the western sources, and the moisture sources of the YB, ITP, and TER shrank to the central-southern TP and the Indian subcontinent. By quantifying the moisture contributions from multiple sources, we found that the terrestrial moisture dominated in all of the sub-basins, particularly in the UT and QB(62–73%). The oceanic contributions were relatively high in the UI(38–42%) and YB(38–41%). In winter, evaporation from the large western water bodies(such as the Mediterranean, Red Sea, and Persian Gul展开更多
Surface water is the greatest contributor to many water supplies in urbanized areas. Understanding local water sources and seasonality is important in evaluating water resource management, which is essential to ensure...Surface water is the greatest contributor to many water supplies in urbanized areas. Understanding local water sources and seasonality is important in evaluating water resource management, which is essential to ensure the sustainability of water supplies to provide potable water. Here we describe the municipal water cycle of Columbus, Ohio, USA, using δ18O, δD, and d-excess, and follow water from precipitation through surface reservoirs to a residential tap between May 2010 and November 2011. We show that trends in water isotopic composition of Ohio precipitation have a seasonal character with more negative values during the winter months and more positive values during the summer months. The year of 2011 was the wettest year on record in Central Ohio, with many months having high d-excess values (>+15‰), suggestive of increased moisture recycling, and possibly moisture introduced from more local sources. Tap waters experienced little lag time in the managed system, having a residence time of ~2 months in the reservoirs. Tap waters and reservoir waters preserved the isotopic signal of the precipitation, but the reservoir morphology also influenced the water residence time, and hence, the isotopic relationship to the precipitation. The reservoirs supplied by the Scioto River function like a river system with a fast throughput of water. The other reservoirs display more constant solute concentrations, longer flow-through times, and more lacustrine qualities. This work provides a basic understanding of a regional water supply system in Central Ohio and helps characterize the water flow in the system. These data will provide useful baseline information for the future as urban populations grow and the climate and hydrologic cycle changes.展开更多
Moisture contribution and transport pathways for Central Asia(CA)are quantitatively examined using the Lagrangian water cycle model based on reanalysis and observational data to explain the precipitation seasonality a...Moisture contribution and transport pathways for Central Asia(CA)are quantitatively examined using the Lagrangian water cycle model based on reanalysis and observational data to explain the precipitation seasonality and the moisture transport variation during 1979-2015.Westerly-related(northwesterly and westerly)transport explains 42%of CA precipitation and dominates in southwest CA,where precipitation is greatest in the cold season.Southeast CA,including part of Northwest China,experiences its maximum precipitation in the warm season and is solely dominated by southerly transport,which explains about 48%of CA precipitation.The remaining 10%of CA precipitation is explained by northerly transport,which steadily impacts north CA and causes a maximum in precipitation in the warm season.Most CA areas are exposed to seasonally varying moisture transport,except for southeast and north CA,which are impacted by southerly and northerly transport year-round.In general,the midlatitude westerlies-driven transport and the Indian monsoon-driven southerly-related transport explain most of the spatial differences in precipitation seasonality over CA.Moreover,the contribution ratio of local evaporation in CA to precipitation exhibits significant interdecadal variability and a meridionally oriented tripole of moisture transport anomalies.Since the early 2000s,CA has experienced a decade of anomalously low local moisture contribution,which seems jointly determined by the weakened moisture contribution from midlatitudes(the Atlantic,Europe,and CA itself)and the enhanced contribution from high latitudes(West Siberia and the Arctic)and tropical areas(South Asia and the Indian Ocean).展开更多
The kinetic fractionation of open-water evaporation against the stable water isotope H_2 ^(18)O is an important mechanism underlying many hydrologic studies that use ^(18)O as an isotopic tracer. A recent in-situ meas...The kinetic fractionation of open-water evaporation against the stable water isotope H_2 ^(18)O is an important mechanism underlying many hydrologic studies that use ^(18)O as an isotopic tracer. A recent in-situ measurement of the isotopic water vapor flux over a lake indicates that the kinetic effect is much weaker(kinetic factor 6.2‰) than assumed previously(kinetic factor14.2‰) by lake isotopic budget studies. This study investigates the implications of the weak kinetic effect for studies of deuterium excess-humidity relationships, regional moisture recycling, and global evapotranspiration partitioning. The results indicate that the low kinetic factor is consistent with the deuterium excess-humidity relationships observed over open oceans.The moisture recycling rate in the Great Lakes region derived from the isotopic tracer method with the low kinetic factor is a much better agreement with those from atmospheric modeling studies than if the default kinetic factor of 14.2‰ is used. The ratio of transpiration to evapotranspiration at global scale decreases from 84±9%(with the default kinetic factor) to 76±19%(with the low kinetic factor), the latter of which is in slightly better agreement with other non-isotopic partitioning results.展开更多
Tibetan Plateau(TP)receives moistures from different directions,so variations of isotope elevation gradient on different sides may exist.In this study,we systematically monitored and modeled the elevation effect of st...Tibetan Plateau(TP)receives moistures from different directions,so variations of isotope elevation gradient on different sides may exist.In this study,we systematically monitored and modeled the elevation effect of stable isotopes in precipitation of the eastern margin of the Tibetan Plateau,where we collected 265 water samples for stable isotope(δ2H andδ^(18)O)analyses,of which 70 are eventful rainfall samples,and 195 are surface water samples,for comparison.Alpine lakes on the mountain peaks were used to reconstruct the average isotope composition of the local precipitation based on the evaporation effect.An elevation gradient of−4.2‰km^(−1)(R^(2)=0.93)was established for the eastern marginal region of TP.This elevation gradient was further confirmed by fractionation assessment using the Rayleigh fractionation model.This is the highest ever reported for the TP and it is the highest as compared to those of all the other slopes as well as that of the interior part of the TP.Precipitation isotopes in the interior of TP show a lower elevation gradient,which is likely caused by significant local moisture recycling.This paper also discusses the limitations of using river water samples to construct the elevation gradient.展开更多
基金Supported by the National Science and Technology Support Program of China(2012BAC20B06)
文摘This paper utilizes a modified Water Accounting Model （WAM） to track the moisture sources of an extreme precipitation event in Shandong during 18-20 July 2007. It is found that different methods in dealing with the residual of the water budget always produce different results in moisture recycling calculations. In addition, results from the backward tracking without the residual are in complete agreement with those from the forward tracking with the residual, and vice versa, implying a mathematical consistency. We thus analyze and derive the conditions under which the two tracking approaches equate with each other. We applied the backward tracking to the Shandong extreme rainfall case and obtained quantitative estimates of moisture contributions of three selected regions away from the rainfall area. The results indicate that the spatial pattern rather than numerical value of the recycling moisture is more reliable in tracking the moisture sources. The moisture of this Shandong rainfall event comes mostly from the nearby upwind area in Southwest China, which is of the terrestrial origin; while the moisture originating from the neighboring West Pacific contributes little to this event.
基金This study was supported by the National Natural Science Foundation of China(42261008,41971034)the Natural Science Foundation of Gansu Province,China(22JR5RA074).
文摘Stable water isotopes are natural tracers quantifying the contribution of moisture recycling to local precipitation,i.e.,the moisture recycling ratio,but various isotope-based models usually lead to different results,which affects the accuracy of local moisture recycling.In this study,a total of 18 stations from four typical areas in China were selected to compare the performance of isotope-based linear and Bayesian mixing models and to determine local moisture recycling ratio.Among the three vapor sources including advection,transpiration,and surface evaporation,the advection vapor usually played a dominant role,and the contribution of surface evaporation was less than that of transpiration.When the abnormal values were ignored,the arithmetic averages of differences between isotope-based linear and the Bayesian mixing models were 0.9%for transpiration,0.2%for surface evaporation,and–1.1%for advection,respectively,and the medians were 0.5%,0.2%,and–0.8%,respectively.The importance of transpiration was slightly less for most cases when the Bayesian mixing model was applied,and the contribution of advection was relatively larger.The Bayesian mixing model was found to perform better in determining an efficient solution since linear model sometimes resulted in negative contribution ratios.Sensitivity test with two isotope scenarios indicated that the Bayesian model had a relatively low sensitivity to the changes in isotope input,and it was important to accurately estimate the isotopes in precipitation vapor.Generally,the Bayesian mixing model should be recommended instead of a linear model.The findings are useful for understanding the performance of isotope-based linear and Bayesian mixing models under various climate backgrounds.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program (Grant Nos. 2019QZKK0201 & 2019QZKK020705)the National Natural Science Foundation of China (Grant Nos. 41988101 & 41871057)"Strategic Priority Research Program" of Chinese Academy of Sciences (Grant No. XDA20060202)。
文摘Tracking and quantifying the moisture sources of precipitation in different drainage basins in the Tibetan Plateau(TP)help to reveal basin-scale hydrological cycle characteristics under the interactions between the westerlies and Indian summer monsoon(ISM) systems and to improve our understanding on the mechanisms of water resource changes in the ‘Asian Water Tower' under climate changes. Based on a Eulerian moisture tracking model(WAM-2) and three atmospheric reanalysis products(ERA-I, MERRA-2, and JRA-55), the contributions of moisture sources to the precipitation in six major sub-basins in the TP were tracked during an approximately 35-year period(1979/1980–2015). The results showed that in the upper Indus(UI),upper Tarim River(UT), and Qaidam Basin(QB), the moisture sources mainly extended westward along the mid-latitude westerlies to the western part of the Eurasian continent. In contrast, in the Yarlung Zangbo River Basin(YB), inner TP(ITP), and the source area of three eastern rivers(TER, including the Nujiang River, Lancang River, and Yangtze River), the moisture sources extended both westward and southward, but mainly southward along the ISM. In winter and spring, all of the sub-basins were dominated by western moisture sources. In summer, the western sources migrated northward with the zonal movement of the westerlies, and simultaneously the southern sources of the YB, ITP, and TER expanded largely toward the Indian Ocean along the ISM. In autumn, the moisture sources of the UI, UT, and QB shrank to the western sources, and the moisture sources of the YB, ITP, and TER shrank to the central-southern TP and the Indian subcontinent. By quantifying the moisture contributions from multiple sources, we found that the terrestrial moisture dominated in all of the sub-basins, particularly in the UT and QB(62–73%). The oceanic contributions were relatively high in the UI(38–42%) and YB(38–41%). In winter, evaporation from the large western water bodies(such as the Mediterranean, Red Sea, and Persian Gul
文摘Surface water is the greatest contributor to many water supplies in urbanized areas. Understanding local water sources and seasonality is important in evaluating water resource management, which is essential to ensure the sustainability of water supplies to provide potable water. Here we describe the municipal water cycle of Columbus, Ohio, USA, using δ18O, δD, and d-excess, and follow water from precipitation through surface reservoirs to a residential tap between May 2010 and November 2011. We show that trends in water isotopic composition of Ohio precipitation have a seasonal character with more negative values during the winter months and more positive values during the summer months. The year of 2011 was the wettest year on record in Central Ohio, with many months having high d-excess values (>+15‰), suggestive of increased moisture recycling, and possibly moisture introduced from more local sources. Tap waters experienced little lag time in the managed system, having a residence time of ~2 months in the reservoirs. Tap waters and reservoir waters preserved the isotopic signal of the precipitation, but the reservoir morphology also influenced the water residence time, and hence, the isotopic relationship to the precipitation. The reservoirs supplied by the Scioto River function like a river system with a fast throughput of water. The other reservoirs display more constant solute concentrations, longer flow-through times, and more lacustrine qualities. This work provides a basic understanding of a regional water supply system in Central Ohio and helps characterize the water flow in the system. These data will provide useful baseline information for the future as urban populations grow and the climate and hydrologic cycle changes.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences Sci-ences under Grant No.XDA20020201the National Natural Sci-ence Foundation of China(NSFC)under Grant Nos.41975099,U2006210,and 41475072.
文摘Moisture contribution and transport pathways for Central Asia(CA)are quantitatively examined using the Lagrangian water cycle model based on reanalysis and observational data to explain the precipitation seasonality and the moisture transport variation during 1979-2015.Westerly-related(northwesterly and westerly)transport explains 42%of CA precipitation and dominates in southwest CA,where precipitation is greatest in the cold season.Southeast CA,including part of Northwest China,experiences its maximum precipitation in the warm season and is solely dominated by southerly transport,which explains about 48%of CA precipitation.The remaining 10%of CA precipitation is explained by northerly transport,which steadily impacts north CA and causes a maximum in precipitation in the warm season.Most CA areas are exposed to seasonally varying moisture transport,except for southeast and north CA,which are impacted by southerly and northerly transport year-round.In general,the midlatitude westerlies-driven transport and the Indian monsoon-driven southerly-related transport explain most of the spatial differences in precipitation seasonality over CA.Moreover,the contribution ratio of local evaporation in CA to precipitation exhibits significant interdecadal variability and a meridionally oriented tripole of moisture transport anomalies.Since the early 2000s,CA has experienced a decade of anomalously low local moisture contribution,which seems jointly determined by the weakened moisture contribution from midlatitudes(the Atlantic,Europe,and CA itself)and the enhanced contribution from high latitudes(West Siberia and the Arctic)and tropical areas(South Asia and the Indian Ocean).
基金supported by the National Natural Science Foundation of China (Grant Nos. 41475141, 41830860, 41575147 & 41505005)the National Key Research and Development Program of China (Grant No. 2016YFC0500102)+5 种基金the U. S. National Science Foundation (Grant No. 1520684)the Science and Technology Department of Ningxia (Grant No. 2015KJHM34)the China Special Fund for Meteorological Research in the Public Interest (Major projects, Grant No. GYHY201506001-6)the NUIST Scientific Foundation (Grant No. KLME1415)the Priority Academic Program Development of Jiangsu Higher Education Institutions (Grant No. PAPD)the Ministry of Education of the People’s Republic of China (Grant No. PCSIRT)
文摘The kinetic fractionation of open-water evaporation against the stable water isotope H_2 ^(18)O is an important mechanism underlying many hydrologic studies that use ^(18)O as an isotopic tracer. A recent in-situ measurement of the isotopic water vapor flux over a lake indicates that the kinetic effect is much weaker(kinetic factor 6.2‰) than assumed previously(kinetic factor14.2‰) by lake isotopic budget studies. This study investigates the implications of the weak kinetic effect for studies of deuterium excess-humidity relationships, regional moisture recycling, and global evapotranspiration partitioning. The results indicate that the low kinetic factor is consistent with the deuterium excess-humidity relationships observed over open oceans.The moisture recycling rate in the Great Lakes region derived from the isotopic tracer method with the low kinetic factor is a much better agreement with those from atmospheric modeling studies than if the default kinetic factor of 14.2‰ is used. The ratio of transpiration to evapotranspiration at global scale decreases from 84±9%(with the default kinetic factor) to 76±19%(with the low kinetic factor), the latter of which is in slightly better agreement with other non-isotopic partitioning results.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42130809 and 41602276)the Beijing Advanced Innovation Program for Land Surface Science of China+1 种基金the Frontiers Science Center for Critical Earth Material Cycling Fund (Grant No. JBGS2102)the CRP Project of IAEA (Grant No. F31006)。
文摘Tibetan Plateau(TP)receives moistures from different directions,so variations of isotope elevation gradient on different sides may exist.In this study,we systematically monitored and modeled the elevation effect of stable isotopes in precipitation of the eastern margin of the Tibetan Plateau,where we collected 265 water samples for stable isotope(δ2H andδ^(18)O)analyses,of which 70 are eventful rainfall samples,and 195 are surface water samples,for comparison.Alpine lakes on the mountain peaks were used to reconstruct the average isotope composition of the local precipitation based on the evaporation effect.An elevation gradient of−4.2‰km^(−1)(R^(2)=0.93)was established for the eastern marginal region of TP.This elevation gradient was further confirmed by fractionation assessment using the Rayleigh fractionation model.This is the highest ever reported for the TP and it is the highest as compared to those of all the other slopes as well as that of the interior part of the TP.Precipitation isotopes in the interior of TP show a lower elevation gradient,which is likely caused by significant local moisture recycling.This paper also discusses the limitations of using river water samples to construct the elevation gradient.
