Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming clima...Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming climate has had an impact on the hydrological cycle. As the glacier area subject to melting has increased and the ablation seasor has become longer, the contribution of meltwater to annual river discharge has increased. The earlier onset of ablation at higher elevation glaciers has resulted in the period of minimum discharge occurring earlier in the year. Seasonal runoff variations are dominated by snow and glacier melt, and an increase of meltwater has resulted in changes of the annual water cycle in the Lijiang Basin and Hailuogou Basin. The increase amplitude of runoff in the downstream re- gion of the glacial area is much stronger than that of precipitation, resulting from the promi- nent increase of meltwater from glacier region in two basins. Continued observations in the glacierized basins should be undertaken in order to monitor changes, to reveal the relation- ships between climate, glaciers, hydrology and water supplies, and to assist in maintaining sustainable regional development.展开更多
The Yangtze River Source Region has an area of 137,704 km2.Its mean annual runoff of 12.52 billion m3,which was recorded by the Chumda Hydrological Station in 1961–2000,accounts for only 0.13 percent of the Yangtze R...The Yangtze River Source Region has an area of 137,704 km2.Its mean annual runoff of 12.52 billion m3,which was recorded by the Chumda Hydrological Station in 1961–2000,accounts for only 0.13 percent of the Yangtze River's total annual streamflow.The extensive rivers,lakes,wetlands,glaciers,snow fields,and permafrost of the Yangtze River Source Region,as well as the region's vast alpine grasslands,play a critical role in storing and regulating the flow of water not only in the upper Yangtze River watershed of Qinghai,Sichuan,the Tibet Autonomous Region (TAR) (Tibet) and Yunnan,but also throughout the entire lower Yangtze River basin.Climate change has been the dominant factor in recent fluctuation in the volume of the Yangtze River Source Region's glacier resources.The Chumda Hydrological Station on the lower Tongtian River has registered a mean annual glacial meltwater of 1.13 billion m3 for the period 1961–2000,makes up 9 percent of the total annual runoff.Glacial meltwater makes up a significant percentage of streamflow in the Yangtze River Source Region,the major rivers of the upper Yangtze River Source Region:the Togto,Dam Chu,Garchu,and Bi Chu (Bu Chu) rivers all originate at large glaciers along the Tanggula Range.Glaciers in the Yangtze River Source Region are typical continental-type glaciers with most glacial meltwater flow occurring June–August;the close correlation between June–August river flows and temperature illustrates the important role of glacial meltwater in feeding rivers.Glaciers in the source region have undergone a long period of rapid ablation beginning in 1993.Examination of flow and temperature data for the 1961–2000 period shows that the annual melting period for glacial ice,snow,and frozen ground in the Yangtze River Source Region now begins earlier because of increasing spring temperatures,resulting in the reduction of summer flood season peak runoffs;meanwhile,increased rates of glacier ablation have resulted in more uneven annual distribution of runoff in the source region.The annual glacial meltwater runoff in the Yangtze River Source Region is projected to increase by 28.5 percent by 2050 over its 1970 value with the projected temperature increase of 2℃ and a precipitation increase of 29 mm.As a critical source of surface water for agriculture on the eastern Qinghai-Tibet Plateau and beyond,the mass retreat of glaciers in the Yangtze River Source Region will have enormous negative impacts on farming and livestock-raising ac-tivities in upper Yangtze River watershed,as well as on the viability of present ecosystems and even socioeconomic development in the upper Yangtze River Basin.展开更多
The effects of vegetation and its seasonal variation on energy and the hydrological cycle were examined using a state-of-the-art Community Atmosphere Model （CAM3）. Three 15-year numerical experiments were completed...The effects of vegetation and its seasonal variation on energy and the hydrological cycle were examined using a state-of-the-art Community Atmosphere Model （CAM3）. Three 15-year numerical experiments were completed： the first with realistic vegetation characteristics varying monthly （VEG run）, the second without vegetation over land （NOVEG run）, and the third with the vegetation characteristics held at their annual mean values （VEGMEAN run）. In these models, the hydrological cycle and land surface energy budget were widely affected by vegetation. Globaland annual-mean evapotranspiration significantly increased compared with the NOVEG by 11.8% in the VEG run run, while runoff decreased by 13.2% when the realistic vegetation is incorporated. Vegetation plays different roles in different regions. In tropical Asia, vegetation-induced cooling of the land surface plays a crucial role in decreasing tropical precipitation. In middle latitudes and the Amazon region, however, the vegetation-induced increase of evapotranspiration plays a more important role in increasing precipitation. The seasonal variation of vegetation also shows clear influences on the hydrological cycle and energy budget. In the boreal mid-high latitudes where vegetation shows a strong seasonal cycle, evapotranspiration and precipitation are higher in the summer in the VEG run than in the VEGMEAN run.展开更多
The progress and advances of the detection and attribution of changes in the hydrological cycle in the IPCC Assessment Reports of WGI and WGII from 1990 to 2007 are reviewed. Accomplishment and endorsed by the joint E...The progress and advances of the detection and attribution of changes in the hydrological cycle in the IPCC Assessment Reports of WGI and WGII from 1990 to 2007 are reviewed. Accomplishment and endorsed by the joint Expert Meeting on Detection and Attribution in 2009, the Good Practice Guidance Paper （GPGP） for IPCC Lead Authors with its main content and characteristics are briefly introduced. Based on the review and the purpose of the GPGP, some characteristics on the detection and attribution of global warming and of changes in the hydrological cycle are presented.展开更多
Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on ...Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index （LAI） are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km^2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type （-85%）. Comparison of the modeled results with the observed discharge data suggests that： （1） Daily discharges over the period of 1992-2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. （2） The relative computing error （RCE） of the annual average discharge is -24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and -14.32% when an REDC （Resource and Environment Database of China） land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used.展开更多
The Three-River Source Region(TRSR),China's water tower and an important ecological barrier in China,provides a considerable amount of water to the downstream regions,home to more than 500 million people.The prese...The Three-River Source Region(TRSR),China's water tower and an important ecological barrier in China,provides a considerable amount of water to the downstream regions,home to more than 500 million people.The present study focused on the assessment of hydrological components(i.e.,precipitation,actual evapotranspiration,potential evapotranspiration,surface flow,baseflow,streamflow,soil moisture,snowmelt water,and terrestrial water storage),their transformation and trends along with meteorological elements(i.e.,maximum temperature,minimum temperature,mean temperature,relative humidity,wind speed,and sunshine hours)in the historical and future periods.For this,the hydrological model,HEC-HMS,was applied to simulate hydrological components and Mann-Kendal to explore the trends for 1981-2015.First time,the statistical downscaling model,SDSM,was used to generate climatic data under the shared socio-economic scenario-5(SSP585)in the region,which was applied to simulate the hydrological cycle.The assessment results showed that precipitation transformed into evapotranspiration and streamflow by 70% and 30%,respectively.In the region,streamflow was generated by 78%,22%,and 5.6% by baseflow,surface flow,and snowmelt.According to trend results,all climatic variables showed statistically significant trends but insignificant in all hydrological components for the historical period,except evapotranspiration.However,all hydroclimatic components were projected to increase in the future,except windspeed.For example,temperature,precipitation,evapotranspiration,streamflow,and direct flow(surface flow)will increase by 1.4(3.3)℃,12(36)%,8.5(19)%,25(95)%,and 77(473)% in 2021-2060(2061-2100)relative to 1981-2020,which shows,the region will be hotter and wetter,with high flooding potential in the future.These results will be helpful for precise water resources planning and management in this extremely sensitive region to climate change.展开更多
In this study, we focus on changes in three important components of the hydrological-cycle in the Haihe River basin （HRB） during 1957-2005： precipitation （Prep）, actual evaportranspiration （ETa）, and pan evapor...In this study, we focus on changes in three important components of the hydrological-cycle in the Haihe River basin （HRB） during 1957-2005： precipitation （Prep）, actual evaportranspiration （ETa）, and pan evaporation （PE）-a measure of potential evaporation. The changes in these components have been evaluated in relation to changes in the East Asian summer monsoon. Summer Prep for the whole basin has decreased significantly during 1957-2005. Recent weakening of the convergence of the integrated water vapor flux, in combination with a change from cyclonic-like large-scale circulation conditions to anti-cyclonic-like conditions, led to the decrease in the summer Prep in the HRB. ETa is positively correlated with Prep on the interannual timescale. On longer timescales, however, ETa is less dependent on Prep or the large-scale circulation. We found negative trends in ETa when the ERA40 reanalysis data were used, but positive trends in ETa when the NCEP/NCAR reanalysis data were used. PE declined during the period 1957-2001. The declining of PE could be explained by a combination of declining solar radiation and declining surface wind. However, the declining solar radiation may itself be related to the weakening winds, due to weaker dispersion of pollution. If so, the downward trend of PE may be mainly caused by weakening winds.展开更多
Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value ce...Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value center of middle cloud amount over the Sichuan Basin extending to the coastal area of southeastern China along the same latitude,and a low one over the TP.The present day（PD）and Last Glacial Maximum（LGM）climates are simulated by using the NCAR Community Climate Model（CCM3）nested with a regional mesoscale model（MM5）.Comparing the clouds simulated by MM5 with the ISCCP data,it is found that the main patterns of high and middle clouds over China can be reproduced by MM5,which implies that the climate characteristics of clouds might he dominated by relative humidity.Meanwhile,the vertical distributions of water vapor and temperature are also well simulated by MM5.Furthermore,the hydrological cycle changes between the LGM and PD simulations are examined.The results show that during the LGM,the tropospheric temperature decreases in summer with a high value reduction center in the upper and middle troposphere; in winter,a high value reduction center of temperature appears in the middle troposphere over southern China,while the temperature in the upper and middle troposphere increases over northern China.There obviously exists a positive correlation between the water vapor content and temperature change.The water vapor content mostly decreases with the maximum drop in the near-ground surface layer,but it increases in the upper and middle troposphere over northern China in winter.Changes of water vapor content gradually weaken with the altitude increasing,reaching the minimum in the upper troposphere.The relative humidity can either increase or decrease with the maximum change greater than 15%.It is not conservative on the regional scale,and its change is consistent with the changes of middle and low clouds.During the LGM,the high cloud reduces nationwide except over Southwest China,and the middle and low clouds also decrease with the greatest reduction seen in the low cloud.Precipitation changes correspond to the changes of middle and low clouds.Based on the changes of the relative humidity and effective precipitation,it is found that during the LGM,Southwest China is wetter in summer,so is Northwest China.展开更多
Light absorbing particles（LAP, e.g., black carbon, brown carbon, and dust） influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric...Light absorbing particles（LAP, e.g., black carbon, brown carbon, and dust） influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance（a.k.a., surface darkening）, which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice（LAPSI） has been identified as one of major forcings affecting climate change, e.g.in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.展开更多
Accurate drought assessment demands thoughtful consideration of drought definition first of all.Drought is commonly defined as a prolonged period of below-average precipitation leading to water shortages that impact e...Accurate drought assessment demands thoughtful consideration of drought definition first of all.Drought is commonly defined as a prolonged period of below-average precipitation leading to water shortages that impact ecosystems,agriculture,and human societies.However,meteorologists,hydrologists,and agronomists often use different criteria to define drought,depending on their specific focus areas.For example,hydrologists define drought according to water deficits in some components of the hydrological cycle(such as precipitation,soil moisture,river flow,and groundwater)or its impacts on the level of services provided to public water supply,irrigation,or hydropower demands(Tate and Gustard,2000).Differences in drought definitions may result in great uncertainties in drought assessment(Satoh et al.,2021).We cannot expect the existence of any workable generalized objective definition of drought(Lloyd-Hughes,2014).展开更多
In the context of global warming, the increasing wildfire frequency has become a critical climate research focus in North America. This study used the Community Earth System Model(CESM 1.2) to investigate the impacts ...In the context of global warming, the increasing wildfire frequency has become a critical climate research focus in North America. This study used the Community Earth System Model(CESM 1.2) to investigate the impacts of 20thcentury wildfires on North American climate and hydrology. Summer represents the peak wildfire season in North America, with the Gulf of Mexico and Midwest regions experiencing the most severe effects. Wildfires not only damage vegetation during the fire season but also extend prolonged impacts into non-fire periods, showing distinct seasonal variations. In spring, wildfires increase surface albedo, triggering a cooling effect through enhanced snow cover and delayed snowmelt. Conversely, summer and autumn surface warming stems primarily from wildfire-suppressed vegetation transpiration. Warming near the Gulf of Mexico enhances moisture transport and precipitation, particularly in summer and autumn. Reduced evaporation and increased precipitation from the Gulf of Mexico significantly altered the hydrological cycle across North America, leading to increased runoff continent-wide.展开更多
Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experime...Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experiments using regional climate model RegCM4. In the first experiment used to study the climatic responses to human carbon emissions, the model were configured over entire China because the impacts of carbon emissions can be detected across the whole country. Results from the first experiment revealed that near-surface air temperature may significantly increase from 2007 to 2059 at a rate exceeding 0.1 ~C per decade in most areas across the country; southwestern and southeastern China also showed increasing trends in summer precipitation, with rates exceeding 10 mm per decade over the same period. In summer, only northern China showed an increasing trend of evapotranspiration, with increase rates ranging from 1 to 5 mm per decade; in winter, increase rates ranging from 1 to 5 mm per decade were observed in most regions. These effects are believed to be caused by global warming from human carbon emissions. In the second experiment used to study the effects of human water use, the model were configured over a limited region-- Haihe River Basin in the northern China, because compared with the human carbon emissions, the effects of human water use are much more local and regional, and the Haihe River Basin is the most typical region in China that suffers from both intensive human groundwater exploitation and surface water diversion. We incorporated a scheme of human water regulation into RegCM4 and conducted the second experiment. Model outputs showed that the groundwater table severely declined by -10 m in 1971-2000 through human groundwater over- exploitation in the basin; in fact, current conditions are so extreme that even reducing the pumping rate by half cannot eliminate the ground- water depletion cones observed in the area. Other hydrological and climatic elements, such as soil moisture, runoff generation, air humidity, precipitation, wind field, and soil and air temperature, were also significantly affected by anthropogenic water withdrawal and consumption, although these effects could be mitigated by reducing the amount of water drawn for extraction and application.展开更多
Global ocean temperature has been rising since the late 1970s at a speed unprecedented during the past century of recordkeeping.This accelerated warming has profound impacts not only on the marine ecosystem and oceani...Global ocean temperature has been rising since the late 1970s at a speed unprecedented during the past century of recordkeeping.This accelerated warming has profound impacts not only on the marine ecosystem and oceanic carbon uptake but also on the global water cycle and climate.During this rapid warming period,the tropical Pacific displays a pronounced La Nin a-like trend,characterized by an intensification of west-east SST gradient and of atmospheric zonal overturning circulation,namely the Walker circulation.This La Nin a-like trend differs from the El Nin o-like trend in warm climate projected by most climate models,and cannot be explained by responses of the global water cycle to warm climate.The results of this study indicate that the intensification of the zonal SST gradient and the Walker circulation are associated with recent strengthening of the upper-ocean meridional overturning circulation.展开更多
Oceanic contribution to the poleward heat flux in the climate system includes two components: the sensible heat flux and the latent heat flux. Although the latent heat flux has been classified as atmospheric heat flux...Oceanic contribution to the poleward heat flux in the climate system includes two components: the sensible heat flux and the latent heat flux. Although the latent heat flux has been classified as atmospheric heat flux exclusively, it is argued that oceanic control over this component of poleward heat flux should play a critically important role. The so-called swamp ocean model practice is analyzed in detail, and the critical role of oceanic circulation in the establishment of the meridional moisture transport is emphasized.展开更多
Based on an analysis of our research results and the main problems relating to urban rainwater treatment, we propose a new approach to urban rainwater management in China. The necessity and feasibility of such a new a...Based on an analysis of our research results and the main problems relating to urban rainwater treatment, we propose a new approach to urban rainwater management in China. The necessity and feasibility of such a new approach are discussed. From an ecological point of view all components of the global system, including residents living in cities, have the same right to enjoy rainwater. Therefore, urban rainwater should neither be simply drained as waste water, nor be completely harvested as a kind of resource. The objective of this new approach is to maintain the natural hydrological cycle in urban areas during urbanization. When necessary, it could also be used to regulate the amount of runoff, evaporation and infiltration in a city in order to rehabilitate the hydrological cycle given the local conditions. Three basic principles should be adopted in rainwater management, i.e., separation of rainfall from sewage, limited utilization and small and decentralized facilities. Four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration, rainwater storage and rainwater pipes. The natural hydrological cycle in urban areas could be rehabilitated through rainwater management, which is of great importance for sustainable development of our cities.展开更多
Changes in the water cycle on the Tibetan Plateau(TP)have a significant impact on local agricultural production and livelihoods and its downstream regions.Against the background of widely reported warming and wetting,...Changes in the water cycle on the Tibetan Plateau(TP)have a significant impact on local agricultural production and livelihoods and its downstream regions.Against the background of widely reported warming and wetting,the hydrological cycle has accelerated and the likelihood of extreme weather events and natural disasters occurring(i.e.,snowstorms,floods,landslides,mudslides,and ice avalanches)has also intensified,especially in the highelevation mountainous regions.Thus,an accurate estimation of the intensity and variation of each component of the water cycle is an urgent scientific question for the assessment of plateau environmental changes.Following the transformation and movement of water between the atmosphere,biosphere and hydrosphere,the authors highlight the urgent need to strengthen the three-dimensional comprehensive observation system(including the eddy covariance system;planetary boundary layer tower;profile measurements of temperature,humidity,and wind by microwave radiometers,wind profiler,and radiosonde system;and cloud and precipitation radars)in the TP region and propose a practical implementation plan.The construction of such a three-dimensional observation system is expected to promote the study of environmental changes and natural hazards prevention.展开更多
The principles that govern the operation of an open and a closed evaporator are relevant for the understanding of the open and “closed” Earth’s atmospheric behaviors, and are thus described. In these greenhouses, t...The principles that govern the operation of an open and a closed evaporator are relevant for the understanding of the open and “closed” Earth’s atmospheric behaviors, and are thus described. In these greenhouses, the water is included, otherwise the heat and mass balances do not match. It is incorrect to consider the radiation as the only energy transfer factor for an atmospheric warming. Demonstrations show that when the greenhouse effect and the cloud cover increase, the evaporation and the wind naturally decrease. Researchers did not understand why reductions in surface solar radiation and pan evaporation have been simultaneous with increased air temperature, cloudiness and precipitation for the last decades. It is an error to state that the evaporation increases based solely on the water and/or air temperatures increase. Also, researchers did not comprehend why in the last 50 years the clouds and the precipitation increased while the evaporation decreased and they named such understanding as the “evaporation paradox”, while others “found” “the cause” violating the laws of thermodynamics, but more precipitation is naturally conciliatory with less evaporation. The same principle that increases the formation of clouds may cause less rainfall. Several measurements confirm the working principles of greenhouses described in this paper. The hydrological cycle is analyzed and it was also put in form of equation, which analyses have never been done before. The human influence alters the velocity of the natural cycles as well as the atmospheric heat and mass balances, and the evaporation has not been the only source for the cloud formation. It is demonstrated that the Earth’s greenhouse effect has increased in some places and this proof is not based only on temperatures.展开更多
Hydrologic reconstructions from North America are largely unknown for the Middle Miocene.Examination of fungal palynomorph assemblages coupled with traditional plant-based palynology permits delineation of local,as op...Hydrologic reconstructions from North America are largely unknown for the Middle Miocene.Examination of fungal palynomorph assemblages coupled with traditional plant-based palynology permits delineation of local,as opposed to regional,climate signals and provides a baseline for study of ancient fungas.Here,the Fungi in a Warmer World project presents paleoecology and paleoclimatology of 351 fungal morphotypes from 3 sites in the United States:the Clarkia Konservat-Lagerstatte site(ldaho),the Alum Bluff site(Florida),and the Bouie River site(Mississippi).Of these,83 fungi are identified as extant taxa and 41 are newly reported from the Miocene.Combining new plant-based paleoclimatic reconstructions with funga-based paleoclimate reconstructions,we demonstrate cooling and hydrologic changes from the Miocene climate optimum to the Serravallian.In the southeastern United States,this is comparable to that reconstructed with pollen and paleobotany alone In the northwestern United States,cooling is greater than indicated by other reconstructions and hydrology shifts seasonally,from no dry season to a dry summer season.Our results demonstrate the utility of fossil fungi as paleoecologic and paleoclimatic proxies and that warmer than modern geological time intervals do not match the"wet gets wetter,dry gets drier"paradigm.Instead,both plants and fungi show an invigorated hydrological cycle across mid-latitude North America.展开更多
Dear Editor,The use of global navigation satellite system(GNSS)technologies to study the hydrological cycle has gained increasing attention.Current research pri-marily spans two domains:GNSS hydrogeodesy and GNSS remo...Dear Editor,The use of global navigation satellite system(GNSS)technologies to study the hydrological cycle has gained increasing attention.Current research pri-marily spans two domains:GNSS hydrogeodesy and GNSS remote sensing.However,these areas remain fragmented within hydrology-related fields.展开更多
River Basins(RBs)are the cradle of human civilization,providing diversified ecosystem services and sustaining fundamental hydrological and biogeochemical cycles on our planet.However,the loss of these ecosystem servic...River Basins(RBs)are the cradle of human civilization,providing diversified ecosystem services and sustaining fundamental hydrological and biogeochemical cycles on our planet.However,the loss of these ecosystem services from RBs has persisted,e.g.,nearly 80%of the world's population faces serious water crisis[1];and one in three people globally lacks access to safe drinking water.展开更多
基金CAS Western Light Program, No.O828Al1001 China Postdoctoral Science Foundation, No.2012M510219+6 种基金 National Natural Science Foundation of China, No.91025002 No.30970492 No.KZZD-EW-04-05 National Natural Science Foundation of China, No.llJ0930003 The CAS Special Grant for Postgraduate Research, Innovation and Practice The Foundation from the State Key Laboratory of Cryosphere Science The Founda- tion from Lijiang City Government
文摘Studying the response to warming of hydrological systems in Chin＇s temperate glacier region is essential in order to provide information required for sustainable develop- ment. The results indicated the warming climate has had an impact on the hydrological cycle. As the glacier area subject to melting has increased and the ablation seasor has become longer, the contribution of meltwater to annual river discharge has increased. The earlier onset of ablation at higher elevation glaciers has resulted in the period of minimum discharge occurring earlier in the year. Seasonal runoff variations are dominated by snow and glacier melt, and an increase of meltwater has resulted in changes of the annual water cycle in the Lijiang Basin and Hailuogou Basin. The increase amplitude of runoff in the downstream re- gion of the glacial area is much stronger than that of precipitation, resulting from the promi- nent increase of meltwater from glacier region in two basins. Continued observations in the glacierized basins should be undertaken in order to monitor changes, to reveal the relation- ships between climate, glaciers, hydrology and water supplies, and to assist in maintaining sustainable regional development.
基金supported by the Major State Basic Research Development Program of China (973 Program) (Grant No. 2007CB411504 and 2007CB411507)the National Natural Science Foundation of China (Grant No. 40771047)
文摘The Yangtze River Source Region has an area of 137,704 km2.Its mean annual runoff of 12.52 billion m3,which was recorded by the Chumda Hydrological Station in 1961–2000,accounts for only 0.13 percent of the Yangtze River's total annual streamflow.The extensive rivers,lakes,wetlands,glaciers,snow fields,and permafrost of the Yangtze River Source Region,as well as the region's vast alpine grasslands,play a critical role in storing and regulating the flow of water not only in the upper Yangtze River watershed of Qinghai,Sichuan,the Tibet Autonomous Region (TAR) (Tibet) and Yunnan,but also throughout the entire lower Yangtze River basin.Climate change has been the dominant factor in recent fluctuation in the volume of the Yangtze River Source Region's glacier resources.The Chumda Hydrological Station on the lower Tongtian River has registered a mean annual glacial meltwater of 1.13 billion m3 for the period 1961–2000,makes up 9 percent of the total annual runoff.Glacial meltwater makes up a significant percentage of streamflow in the Yangtze River Source Region,the major rivers of the upper Yangtze River Source Region:the Togto,Dam Chu,Garchu,and Bi Chu (Bu Chu) rivers all originate at large glaciers along the Tanggula Range.Glaciers in the Yangtze River Source Region are typical continental-type glaciers with most glacial meltwater flow occurring June–August;the close correlation between June–August river flows and temperature illustrates the important role of glacial meltwater in feeding rivers.Glaciers in the source region have undergone a long period of rapid ablation beginning in 1993.Examination of flow and temperature data for the 1961–2000 period shows that the annual melting period for glacial ice,snow,and frozen ground in the Yangtze River Source Region now begins earlier because of increasing spring temperatures,resulting in the reduction of summer flood season peak runoffs;meanwhile,increased rates of glacier ablation have resulted in more uneven annual distribution of runoff in the source region.The annual glacial meltwater runoff in the Yangtze River Source Region is projected to increase by 28.5 percent by 2050 over its 1970 value with the projected temperature increase of 2℃ and a precipitation increase of 29 mm.As a critical source of surface water for agriculture on the eastern Qinghai-Tibet Plateau and beyond,the mass retreat of glaciers in the Yangtze River Source Region will have enormous negative impacts on farming and livestock-raising ac-tivities in upper Yangtze River watershed,as well as on the viability of present ecosystems and even socioeconomic development in the upper Yangtze River Basin.
基金supported jointly by the National Basic Research Program of China (Grant No. 2006CB400502)the Foundation of the Jiangsu Key Laboratory of Meteorological Disaster KLME0704the China Postdoctoral Science Foundation 20070410133
文摘The effects of vegetation and its seasonal variation on energy and the hydrological cycle were examined using a state-of-the-art Community Atmosphere Model （CAM3）. Three 15-year numerical experiments were completed： the first with realistic vegetation characteristics varying monthly （VEG run）, the second without vegetation over land （NOVEG run）, and the third with the vegetation characteristics held at their annual mean values （VEGMEAN run）. In these models, the hydrological cycle and land surface energy budget were widely affected by vegetation. Globaland annual-mean evapotranspiration significantly increased compared with the NOVEG by 11.8% in the VEG run run, while runoff decreased by 13.2% when the realistic vegetation is incorporated. Vegetation plays different roles in different regions. In tropical Asia, vegetation-induced cooling of the land surface plays a crucial role in decreasing tropical precipitation. In middle latitudes and the Amazon region, however, the vegetation-induced increase of evapotranspiration plays a more important role in increasing precipitation. The seasonal variation of vegetation also shows clear influences on the hydrological cycle and energy budget. In the boreal mid-high latitudes where vegetation shows a strong seasonal cycle, evapotranspiration and precipitation are higher in the summer in the VEG run than in the VEGMEAN run.
基金supported by the National Basic Research Program of China(2010CB428406)the Ministry of Water Resources Commonwealth Project (200801001)
文摘The progress and advances of the detection and attribution of changes in the hydrological cycle in the IPCC Assessment Reports of WGI and WGII from 1990 to 2007 are reviewed. Accomplishment and endorsed by the joint Expert Meeting on Detection and Attribution in 2009, the Good Practice Guidance Paper （GPGP） for IPCC Lead Authors with its main content and characteristics are briefly introduced. Based on the review and the purpose of the GPGP, some characteristics on the detection and attribution of global warming and of changes in the hydrological cycle are presented.
文摘Using the three-layer variable infiltration capacity （VIC-3L） hydrological model and the successive interpolation approach （SIA） of climate factors, the authors studied the effect of different land cover types on the surface hydrological cycle. Daily climate data from 1992 to 2001 and remotely-sensed leaf area index （LAI） are used in the model. The model is applied to the Baohe River basin, a subbasin of the Yangtze River basin, China, with an area of 2500 km^2. The vegetation cover types in the Baohe River basin consist mostly of the mixed forest type （-85%）. Comparison of the modeled results with the observed discharge data suggests that： （1） Daily discharges over the period of 1992-2001 simulated with inputs of remotely-sensed land cover data and LAI data can generally produce observed discharge variations, and the modeled annual total discharge agrees with observations with a mean difference of 1.4%. The use of remote sensing images also makes the modeled spatial distributions of evapotranspiration physically meaningful. （2） The relative computing error （RCE） of the annual average discharge is -24.8% when the homogeneous broadleaf deciduous forestry cover is assumed for the watershed. The error is 21.8% when a homogeneous cropland cover is assumed and -14.32% when an REDC （Resource and Environment Database of China） land cover map is used. The error is reduced to 1.4% when a remotely-sensed land cover at 1000-m resolution is used.
基金financially supported by Qinghai Provincial Natural Science Foundation(2019-ZJ-7020)the Scientific Research and Promotion Projects of the Second Phase Project of Ecological Protection and Construction of the Three Rivers Headwater Region in Qinghai Province(2018-S-3)the Alliance International Sceince Organaizations(ANSO)Collaborative Research Project(ANSO-CR-PP-2022-06).
文摘The Three-River Source Region(TRSR),China's water tower and an important ecological barrier in China,provides a considerable amount of water to the downstream regions,home to more than 500 million people.The present study focused on the assessment of hydrological components(i.e.,precipitation,actual evapotranspiration,potential evapotranspiration,surface flow,baseflow,streamflow,soil moisture,snowmelt water,and terrestrial water storage),their transformation and trends along with meteorological elements(i.e.,maximum temperature,minimum temperature,mean temperature,relative humidity,wind speed,and sunshine hours)in the historical and future periods.For this,the hydrological model,HEC-HMS,was applied to simulate hydrological components and Mann-Kendal to explore the trends for 1981-2015.First time,the statistical downscaling model,SDSM,was used to generate climatic data under the shared socio-economic scenario-5(SSP585)in the region,which was applied to simulate the hydrological cycle.The assessment results showed that precipitation transformed into evapotranspiration and streamflow by 70% and 30%,respectively.In the region,streamflow was generated by 78%,22%,and 5.6% by baseflow,surface flow,and snowmelt.According to trend results,all climatic variables showed statistically significant trends but insignificant in all hydrological components for the historical period,except evapotranspiration.However,all hydroclimatic components were projected to increase in the future,except windspeed.For example,temperature,precipitation,evapotranspiration,streamflow,and direct flow(surface flow)will increase by 1.4(3.3)℃,12(36)%,8.5(19)%,25(95)%,and 77(473)% in 2021-2060(2061-2100)relative to 1981-2020,which shows,the region will be hotter and wetter,with high flooding potential in the future.These results will be helpful for precise water resources planning and management in this extremely sensitive region to climate change.
基金Supported by the National Basic Research and Development （973） Program of China （2006CB403404）National Natural Science Foundation of China （40675038） Acknowledgments. The authors would like to thank the reviewers for their comments that have helped improve the manuscript.
文摘In this study, we focus on changes in three important components of the hydrological-cycle in the Haihe River basin （HRB） during 1957-2005： precipitation （Prep）, actual evaportranspiration （ETa）, and pan evaporation （PE）-a measure of potential evaporation. The changes in these components have been evaluated in relation to changes in the East Asian summer monsoon. Summer Prep for the whole basin has decreased significantly during 1957-2005. Recent weakening of the convergence of the integrated water vapor flux, in combination with a change from cyclonic-like large-scale circulation conditions to anti-cyclonic-like conditions, led to the decrease in the summer Prep in the HRB. ETa is positively correlated with Prep on the interannual timescale. On longer timescales, however, ETa is less dependent on Prep or the large-scale circulation. We found negative trends in ETa when the ERA40 reanalysis data were used, but positive trends in ETa when the NCEP/NCAR reanalysis data were used. PE declined during the period 1957-2001. The declining of PE could be explained by a combination of declining solar radiation and declining surface wind. However, the declining solar radiation may itself be related to the weakening winds, due to weaker dispersion of pollution. If so, the downward trend of PE may be mainly caused by weakening winds.
基金Supported by the National Natural Science Foundation of China under Grant Nos.40231011,90102055,and 40233034
文摘Based on the International Satellite Cloud Climatology Project（ISCCP）data in 1983-2006,it is found that there is a high value center of high cloud amount over the Tibetan Plateau（TP）,while there is a high value center of middle cloud amount over the Sichuan Basin extending to the coastal area of southeastern China along the same latitude,and a low one over the TP.The present day（PD）and Last Glacial Maximum（LGM）climates are simulated by using the NCAR Community Climate Model（CCM3）nested with a regional mesoscale model（MM5）.Comparing the clouds simulated by MM5 with the ISCCP data,it is found that the main patterns of high and middle clouds over China can be reproduced by MM5,which implies that the climate characteristics of clouds might he dominated by relative humidity.Meanwhile,the vertical distributions of water vapor and temperature are also well simulated by MM5.Furthermore,the hydrological cycle changes between the LGM and PD simulations are examined.The results show that during the LGM,the tropospheric temperature decreases in summer with a high value reduction center in the upper and middle troposphere; in winter,a high value reduction center of temperature appears in the middle troposphere over southern China,while the temperature in the upper and middle troposphere increases over northern China.There obviously exists a positive correlation between the water vapor content and temperature change.The water vapor content mostly decreases with the maximum drop in the near-ground surface layer,but it increases in the upper and middle troposphere over northern China in winter.Changes of water vapor content gradually weaken with the altitude increasing,reaching the minimum in the upper troposphere.The relative humidity can either increase or decrease with the maximum change greater than 15%.It is not conservative on the regional scale,and its change is consistent with the changes of middle and low clouds.During the LGM,the high cloud reduces nationwide except over Southwest China,and the middle and low clouds also decrease with the greatest reduction seen in the low cloud.Precipitation changes correspond to the changes of middle and low clouds.Based on the changes of the relative humidity and effective precipitation,it is found that during the LGM,Southwest China is wetter in summer,so is Northwest China.
基金supported by the U.S.Department of Energy, Office of Science, Biological and Environmental Research, as part of the Earth System Modeling ProgramThe NASA Modeling, Analysis, and Prediction (MAP) Program by the Science Mission Directorate at NASA Headquarters supported the work contributed by Teppei J.YASUNARI and William K.M.LAU+2 种基金The NASA GEOS-5 simulation was implemented in the system for NASA Center for Climate Simulation (NCCS).M.G.Flanner was partially supported by NSF 1253154support from the China Scholarship FundThe Pacific Northwest National Laboratory is operated for DOE by Battelle Memorial Institute under contract DE-AC06-76RLO1830
文摘Light absorbing particles（LAP, e.g., black carbon, brown carbon, and dust） influence water and energy budgets of the atmosphere and snowpack in multiple ways. In addition to their effects associated with atmospheric heating by absorption of solar radiation and interactions with clouds, LAP in snow on land and ice can reduce the surface reflectance（a.k.a., surface darkening）, which is likely to accelerate the snow aging process and further reduces snow albedo and increases the speed of snowpack melt. LAP in snow and ice（LAPSI） has been identified as one of major forcings affecting climate change, e.g.in the fourth and fifth assessment reports of IPCC. However, the uncertainty level in quantifying this effect remains very high. In this review paper, we document various technical methods of measuring LAPSI and review the progress made in measuring the LAPSI in Arctic, Tibetan Plateau and other mid-latitude regions. We also report the progress in modeling the mass concentrations, albedo reduction, radiative forcing, and climatic and hydrological impact of LAPSI at global and regional scales. Finally we identify some research needs for reducing the uncertainties in the impact of LAPSI on global and regional climate and the hydrological cycle.
基金supported by the National Natural Science Foundation of China(Grant No.42471027).
文摘Accurate drought assessment demands thoughtful consideration of drought definition first of all.Drought is commonly defined as a prolonged period of below-average precipitation leading to water shortages that impact ecosystems,agriculture,and human societies.However,meteorologists,hydrologists,and agronomists often use different criteria to define drought,depending on their specific focus areas.For example,hydrologists define drought according to water deficits in some components of the hydrological cycle(such as precipitation,soil moisture,river flow,and groundwater)or its impacts on the level of services provided to public water supply,irrigation,or hydropower demands(Tate and Gustard,2000).Differences in drought definitions may result in great uncertainties in drought assessment(Satoh et al.,2021).We cannot expect the existence of any workable generalized objective definition of drought(Lloyd-Hughes,2014).
基金National Natural Science Foundation of China(42175022)。
文摘In the context of global warming, the increasing wildfire frequency has become a critical climate research focus in North America. This study used the Community Earth System Model(CESM 1.2) to investigate the impacts of 20thcentury wildfires on North American climate and hydrology. Summer represents the peak wildfire season in North America, with the Gulf of Mexico and Midwest regions experiencing the most severe effects. Wildfires not only damage vegetation during the fire season but also extend prolonged impacts into non-fire periods, showing distinct seasonal variations. In spring, wildfires increase surface albedo, triggering a cooling effect through enhanced snow cover and delayed snowmelt. Conversely, summer and autumn surface warming stems primarily from wildfire-suppressed vegetation transpiration. Warming near the Gulf of Mexico enhances moisture transport and precipitation, particularly in summer and autumn. Reduced evaporation and increased precipitation from the Gulf of Mexico significantly altered the hydrological cycle across North America, leading to increased runoff continent-wide.
文摘Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experiments using regional climate model RegCM4. In the first experiment used to study the climatic responses to human carbon emissions, the model were configured over entire China because the impacts of carbon emissions can be detected across the whole country. Results from the first experiment revealed that near-surface air temperature may significantly increase from 2007 to 2059 at a rate exceeding 0.1 ~C per decade in most areas across the country; southwestern and southeastern China also showed increasing trends in summer precipitation, with rates exceeding 10 mm per decade over the same period. In summer, only northern China showed an increasing trend of evapotranspiration, with increase rates ranging from 1 to 5 mm per decade; in winter, increase rates ranging from 1 to 5 mm per decade were observed in most regions. These effects are believed to be caused by global warming from human carbon emissions. In the second experiment used to study the effects of human water use, the model were configured over a limited region-- Haihe River Basin in the northern China, because compared with the human carbon emissions, the effects of human water use are much more local and regional, and the Haihe River Basin is the most typical region in China that suffers from both intensive human groundwater exploitation and surface water diversion. We incorporated a scheme of human water regulation into RegCM4 and conducted the second experiment. Model outputs showed that the groundwater table severely declined by -10 m in 1971-2000 through human groundwater over- exploitation in the basin; in fact, current conditions are so extreme that even reducing the pumping rate by half cannot eliminate the ground- water depletion cones observed in the area. Other hydrological and climatic elements, such as soil moisture, runoff generation, air humidity, precipitation, wind field, and soil and air temperature, were also significantly affected by anthropogenic water withdrawal and consumption, although these effects could be mitigated by reducing the amount of water drawn for extraction and application.
基金supported by the Major Project of National Science Foundation of China(Grant Nos. 40890150 and 40890155)the National Science Foundation for Distinguished Young Scholars of China(Grant No. 40788002)
文摘Global ocean temperature has been rising since the late 1970s at a speed unprecedented during the past century of recordkeeping.This accelerated warming has profound impacts not only on the marine ecosystem and oceanic carbon uptake but also on the global water cycle and climate.During this rapid warming period,the tropical Pacific displays a pronounced La Nin a-like trend,characterized by an intensification of west-east SST gradient and of atmospheric zonal overturning circulation,namely the Walker circulation.This La Nin a-like trend differs from the El Nin o-like trend in warm climate projected by most climate models,and cannot be explained by responses of the global water cycle to warm climate.The results of this study indicate that the intensification of the zonal SST gradient and the Walker circulation are associated with recent strengthening of the upper-ocean meridional overturning circulation.
文摘Oceanic contribution to the poleward heat flux in the climate system includes two components: the sensible heat flux and the latent heat flux. Although the latent heat flux has been classified as atmospheric heat flux exclusively, it is argued that oceanic control over this component of poleward heat flux should play a critically important role. The so-called swamp ocean model practice is analyzed in detail, and the critical role of oceanic circulation in the establishment of the meridional moisture transport is emphasized.
基金Projects 40371113 supported by the National Natural Science Foundation of China and OF060096Young Foundation of China University of Mining &Technology
文摘Based on an analysis of our research results and the main problems relating to urban rainwater treatment, we propose a new approach to urban rainwater management in China. The necessity and feasibility of such a new approach are discussed. From an ecological point of view all components of the global system, including residents living in cities, have the same right to enjoy rainwater. Therefore, urban rainwater should neither be simply drained as waste water, nor be completely harvested as a kind of resource. The objective of this new approach is to maintain the natural hydrological cycle in urban areas during urbanization. When necessary, it could also be used to regulate the amount of runoff, evaporation and infiltration in a city in order to rehabilitate the hydrological cycle given the local conditions. Three basic principles should be adopted in rainwater management, i.e., separation of rainfall from sewage, limited utilization and small and decentralized facilities. Four methods can be used for urban rainwater management: rainwater harvest, rainwater infiltration, rainwater storage and rainwater pipes. The natural hydrological cycle in urban areas could be rehabilitated through rainwater management, which is of great importance for sustainable development of our cities.
基金This research was jointly funded by the Second Tibetan Plateau Scientific Expedition and Research Program(Grant Nos.2019QZKK0103 and 2019QZKK0105)the National Natural Science Foundation of China(Grant Nos.91837208 and 42075085).
文摘Changes in the water cycle on the Tibetan Plateau(TP)have a significant impact on local agricultural production and livelihoods and its downstream regions.Against the background of widely reported warming and wetting,the hydrological cycle has accelerated and the likelihood of extreme weather events and natural disasters occurring(i.e.,snowstorms,floods,landslides,mudslides,and ice avalanches)has also intensified,especially in the highelevation mountainous regions.Thus,an accurate estimation of the intensity and variation of each component of the water cycle is an urgent scientific question for the assessment of plateau environmental changes.Following the transformation and movement of water between the atmosphere,biosphere and hydrosphere,the authors highlight the urgent need to strengthen the three-dimensional comprehensive observation system(including the eddy covariance system;planetary boundary layer tower;profile measurements of temperature,humidity,and wind by microwave radiometers,wind profiler,and radiosonde system;and cloud and precipitation radars)in the TP region and propose a practical implementation plan.The construction of such a three-dimensional observation system is expected to promote the study of environmental changes and natural hazards prevention.
文摘The principles that govern the operation of an open and a closed evaporator are relevant for the understanding of the open and “closed” Earth’s atmospheric behaviors, and are thus described. In these greenhouses, the water is included, otherwise the heat and mass balances do not match. It is incorrect to consider the radiation as the only energy transfer factor for an atmospheric warming. Demonstrations show that when the greenhouse effect and the cloud cover increase, the evaporation and the wind naturally decrease. Researchers did not understand why reductions in surface solar radiation and pan evaporation have been simultaneous with increased air temperature, cloudiness and precipitation for the last decades. It is an error to state that the evaporation increases based solely on the water and/or air temperatures increase. Also, researchers did not comprehend why in the last 50 years the clouds and the precipitation increased while the evaporation decreased and they named such understanding as the “evaporation paradox”, while others “found” “the cause” violating the laws of thermodynamics, but more precipitation is naturally conciliatory with less evaporation. The same principle that increases the formation of clouds may cause less rainfall. Several measurements confirm the working principles of greenhouses described in this paper. The hydrological cycle is analyzed and it was also put in form of equation, which analyses have never been done before. The human influence alters the velocity of the natural cycles as well as the atmospheric heat and mass balances, and the evaporation has not been the only source for the cloud formation. It is demonstrated that the Earth’s greenhouse effect has increased in some places and this proof is not based only on temperatures.
基金supported by the Richard A.Walls Geological Research Fund through the Morehead State University Foundation.The Fungi in a Warmer World(Fia WW)project was jointly funded by NSF/Geo and NERC under NSF award#2015813 to J.M.K.O.and NERC award identifier NE/V01501X/1 to M.J.P.
文摘Hydrologic reconstructions from North America are largely unknown for the Middle Miocene.Examination of fungal palynomorph assemblages coupled with traditional plant-based palynology permits delineation of local,as opposed to regional,climate signals and provides a baseline for study of ancient fungas.Here,the Fungi in a Warmer World project presents paleoecology and paleoclimatology of 351 fungal morphotypes from 3 sites in the United States:the Clarkia Konservat-Lagerstatte site(ldaho),the Alum Bluff site(Florida),and the Bouie River site(Mississippi).Of these,83 fungi are identified as extant taxa and 41 are newly reported from the Miocene.Combining new plant-based paleoclimatic reconstructions with funga-based paleoclimate reconstructions,we demonstrate cooling and hydrologic changes from the Miocene climate optimum to the Serravallian.In the southeastern United States,this is comparable to that reconstructed with pollen and paleobotany alone In the northwestern United States,cooling is greater than indicated by other reconstructions and hydrology shifts seasonally,from no dry season to a dry summer season.Our results demonstrate the utility of fossil fungi as paleoecologic and paleoclimatic proxies and that warmer than modern geological time intervals do not match the"wet gets wetter,dry gets drier"paradigm.Instead,both plants and fungi show an invigorated hydrological cycle across mid-latitude North America.
基金jointly supported by the National Natural Science Foundation of China(NSFC)projects(grant no.42471511)the Beijing Nova Program(grant nos.20230484327 and 20240484540)+2 种基金the Hunan Provincial Natural Science Foundation project(grant no.2024JJ9186)the Fundamental Research Funds for the Central Universities,Peking Universitysupported by 1311 DFG under SFB 1502/1-2022(project number 450058266).
文摘Dear Editor,The use of global navigation satellite system(GNSS)technologies to study the hydrological cycle has gained increasing attention.Current research pri-marily spans two domains:GNSS hydrogeodesy and GNSS remote sensing.However,these areas remain fragmented within hydrology-related fields.
基金supported by the National Natural Science Foundation of China(41925007)。
文摘River Basins(RBs)are the cradle of human civilization,providing diversified ecosystem services and sustaining fundamental hydrological and biogeochemical cycles on our planet.However,the loss of these ecosystem services from RBs has persisted,e.g.,nearly 80%of the world's population faces serious water crisis[1];and one in three people globally lacks access to safe drinking water.
