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Accurate monitoring of leaf phenology, from individual trees to entire ecosystems, is vital for understanding and modeling forest carbon and water cycles, as well as assessing climate change impact. However, the accuracy of many remote-sensing phenological products remains difficult to directly corroborate using ground-based monitoring, owing to variations in the observed indicators and the scales used. This limitation hampers the practical implementation of remote-sensing phenological metrics. In our study, the start of growing season (SOS) from 2016 to 2021 was estimated for the continental USA using Sentinel-2 images. The results were then matched with several ground-based spring vegetation phenology metrics obtained by the USA National Phenology Network (USA-NPN). In this study, we focused on the relationships between the leaf-unfolding degree (LUD), the SOS, and the factors that drive these measures. Our results revealed that: (1) the ground-based leaves and increasing leaf size stages were significantly correlated with the SOS; (2) with the closest match being observed for a leaf spread of 13%; (2) the relationship between the SOS and LUD varied according to the species and ecoregion, and the pre-season cumulative radiation was found to be the main factor affecting the degree of matching between the ground observations and the metrics derived from the Sentinel-2 data. Our investigations provide a ground-based spring phenology metric that can be used to verify or evaluate remote-sensing spring phenology products and will help to improve the accuracy of remote-sensing phenology metrics. [ABSTRACT FROM AUTHOR]

Municipal solid wastes (MSWs) disposed in landfills are generally exposed to drying and wetting cycles because of the variation in environmental conditions, decomposition of organics and leachate recirculation. This paper studies the water retention curves (WRCs) of fresh and degraded MSWs under various numbers of drying and wetting cycles with water and leachate exposure. The result indicates that the water retention capacities of MSWs decrease with drying and wetting cycles. The maximum hysteresis between the drying and wetting cycles is observed in the first cycles for all MSW samples. The WRCs of medium to highly decomposed MSWs under drying and wetting cycles are similar to those of soils. The WRCs of fresh MSWs can undergo substantial changes due to the discharge of intra-particle moisture caused by decomposition and compression. For both fresh and decomposed MSWs, the WRCs stabilize after 3 drying and wetting cycles. However, only the MSWs of one initial composition with similar void ratios were investigated. Further research should be conducted to investigate the water retention behavior of MSWs with diverse initial compositions (e.g., food contents) and void ratios. [ABSTRACT FROM AUTHOR]

Climate change has an adverse effect on the global hydrological cycle and hence climatic extremes are becoming more persistent. Therefore, the present study analyses the characteristics of the compound extremes in India using the Godavari River basin as a test bed. The study examines the individual return period (IRP) and pairwise joint return period (JRP) of several climate extreme indices such as consecutive dry days (CDD), consecutive wet days (CWD), percentage rainfall of very dry days (R5Tot) and very hot days (TX95) considering historical and future period of two scenarios, SSP245 and SSP585, from the CMIP6 consortium. Both SSPs indicates an upward trend in the indices for CWD and TX95, whilst showcasing a declining trend for CDD and R5Tot at 5% significance level. Under SSP585, the values of JRPs TR5Tot,TX952, TR5Tot,TX955, TR5Tot,TX9510 and TR5Tot,TX9525 ranges from 3 to 5 years, 14–55 years, 35–274 years and 104 to >1000 during epoch‐1 (2023–2060). During epoch‐2 (2061–2100), the JRPs values are generally higher. Regions displaying lower JRPs values suggest a higher likelihood of simultaneous occurrences of extremes such as floods and droughts, as well as very dry days and warm days within the same year. Under SSP585, the maximum (minimum) value of change rate (CR) of JRP for TCDD,CWD10 and TCDD,CWD25 during epoch‐1 is more than 900% (−80%) and 1000% (−90%), whereas during epoch‐2, the corresponding CR values are greater than 700% (−80%) and 1000% (−90%). The future possibility of co‐occurrence of 'CDD and CWD' and 'R5Tot and TX95', both exceeding their 10‐ and 25‐year IRP, in a single year, is highly likely for the regions with low CR values and unlikely for the regions with high CR values. The study would help in understanding the spatial and temporal variability of compound climate extremes over the Godavari River basin. [ABSTRACT FROM AUTHOR]

Potential evapotranspiration (PET), as an indicator of atmospheric evaporative demand, is a critical hydrological and meteorological factor to reflect regional and global hydrological cycles and environmental change. Understanding these nuanced responses of PET to environmental changes is important for agricultural production and water demand estimation. This study rigorously evaluated fluctuations in PET using the Penman–Monteith model over a 50-year span from 1970 to 2020 in the Sichuan–Chongqing region, an area notably susceptible to climate change. The changing characteristics of PET and local meteorological factors were detected by integrating the Mann–Kendall method and Pettitt test. Furthermore, the contribution and sensitivity of key meteorological variables to the observed variation in PET were also thoroughly investigated. Breakpoint analysis revealed that abrupt changes appeared in 1996 for annual PET. The detrending method indicated that substantial decreases in net radiation and wind speed (p < 0.01) were responsible for the decrease in annual PET from 1970 to 1996. Marked increases in minimum temperature and wind speed were the driving forces behind the uptick in annual PET in 1997–2020. At seasonal scales, wind speed and net radiation predominantly influenced PET in 1970–1996 in general. However, from 1997 to 2020, the factors controlling PET fluctuations displayed considerable seasonal variation. Sensitivity analysis showed that Ws and Tmin were the second-most sensitive factors. By exploring the impacts of PET changes and shifts, attention must be paid when allocating water resources reasonably under the background of ongoing climate change and likelihood of future drought. [ABSTRACT FROM AUTHOR]

Surface Water–Groundwater (SW–GW) interaction is a crucial aspect of the hydrological cycle and requires accurate modeling for reliable predictions. In many basic hydrological models and calculations, it is common to assume that the water density is constant. However, density-dependent flow, which accounts for changes in water density, plays a significant role in various hydrological processes. This study aims to quantify the effects of density-dependent flow on SW–GW interaction and evaluate the sensitivity of dominant hydrological drivers to density-dependent flow. Our simulations using the HydroGeoSphere model revealed that neglecting density-dependent flow in SW–GW interaction can lead to inaccurate estimations of water and solute balances. In particular, including density-dependent flow in the model yielded more realistic salinity distributions under gaining river scenarios and captured the gradual expansion of freshwater lenses under losing river scenarios. The results also indicated that under non-density-dependent flow, more saline groundwater is exposed to evapotranspiration, resulting in higher solute mass storage and a more saline unsaturated zone. Further, surface recharge and pumping rates played crucial roles in salinity distribution. This study highlights the critical importance of incorporating density-dependent flow in simulations, providing valuable insights for improving the accuracy of predictions and effectively managing water and solute balances in floodplain aquifers. [ABSTRACT FROM AUTHOR]

Chemical and physical denudation rates have been assessed in areas with different lithologies. Surprisingly, there are no studies that attempt to document these rates in the Poços de Caldas Alkaline Massif (PC), the largest alkaline magmatism in South America and an important Al supergene deposit in Brazil. Therefore, the chemical and physical denudation rates were assessed and explained in the PC. Surface water and rainwater samples were collected at the Amoras Stream basin, covering one complete hydrological cycle (2016). All samples were analyzed for dissolved cations, silica, anions, total dissolved solids (TDS), and total suspended solids (TSS). The results reflected the seasonal variation on discharge, water temperature, and electrical conductivity in the Amoras Stream, with most of the cations, anions, silica TDS, and TSS being carried in the wet season. Partial hydrolysis and silicate incongruent dissolution are the main water/rock interactions in the PC, with an atmospheric/soil CO2 consumption rate of 1.6 × 105 mol/km2/a. The annual fluxes of Cl−, PO43−, NO3−, and Al3+ were significantly influenced from rainwater. Chemical and physical weathering rates were 4 ± 0.8 and 3.0 ± 0.6 m/Ma in the PC, respectively, indicating that under the current climatic condition, the weathering profile is in dynamic equilibrium. [ABSTRACT FROM AUTHOR]

Estimations of ecosystem metabolism have rarely been used to quantify productivity in structural reductionist approaches for the description of phytoplankton composition. However, estimations of ecosystem metabolism could contribute to a better understanding of the relationship between phytoplankton composition and ecosystem functioning. To examine this, we investigated the community structure of phytoplankton in a set of Mediterranean coastal lagoons (natural and artificial) during a hydrological cycle to identify the most important environmental variables determining phytoplankton species composition. The focus of the study was on the quantification of productivity-related variables using estimations of ecosystem metabolism, such as different proxies for the estimation of the production-to-biomass ratio and of the relative importance of K- and r-strategies, which are commonly used conceptually but not quantified. Our results demonstrated differences in phytoplankton composition between seasons, due to the dominant hydrological pattern of flooding confinement in the salt marsh, and between lagoons that were caused by different levels of nutrient availability. Moreover, there was a notable decrease in the production/biomass ratio and a prevalence of K-strategists with seasonal succession, as predicted by Margalef's mandala. Thus, the results showed that estimations of ecosystem metabolism are useful for the higher frequency quantification of important ecological variables, and contribute to a better understanding of planktonic assemblages, and physical and chemical changes, in these fluctuating ecosystems. [ABSTRACT FROM AUTHOR]

Climate change accelerates the changes in the hydrological cycle, which increases or decreases the intensity and duration of the drought events. This study assesses the drought risk under future climatic projections by computing drought hazard and drought vulnerability at a sub-basin scale. A multivariate drought hazard index (MDHI) considers deficits in precipitation and streamflow to quantify droughts. MDHI was analyzed using the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and Streamflow Drought Index (SDI). Soil and Water Assessment Tool (SWAT+) simulated hydrological variables under baseline and future SSP scenarios were used to estimate MDHI. Drought vulnerability assessment is estimated by combining exposure, sensitivity and adaptive capacity indicators. The results show that the Drought Hazard Index (DHI) are likely to decrease in future climate change scenarios in comparison with the baseline. The Drought Vulnerability Index (DVI) reveals more than 50% of the basin falls under the high and very high vulnerable category. Based on the drought risk assessment, during the baseline period 48.82%, and 15.25% of the total basin area fall under high and very high drought risk. In the case of the future SSP245 and SSP585 scenarios, the high drought risk area gets reduced extensively with 15.09% and 1.02% respectively. The drought risk will be lower for future scenarios compared to baseline. This study aids the policymakers and water managers in prioritizing the projects on a sub-basin level to solve drought risk in future climatic conditions. [ABSTRACT FROM AUTHOR]

The trend detection in hydro-climatological series is a prime priority in the context of changing climate. Evapotranspiration is a crucial component of the hydrological cycle and surface energy balance that plays a key role in irrigation water management. The present study examined the spatio-temporal variations of annual and seasonal reference evapotranspiration using Mann–Kendall and Innovative trend analysis, in South West and central part of Punjab over the period of 1980–2021. The results revealed that reference evapotranspiration (RET) for the annual, pre-monsoon, and post-monsoon series at Sangrur (Central Zone) and for winter at Bathinda (South-West) were serially correlated using the autocorrelation test of lag-1 at a 5% significance level. The highest aridity index (0.34 ± 0.10) and the lowest moisture index (-0.66 ± 0.10) were detected at Moga station, followed by Sangrur station in Central Punjab. The overall results revealed that annual and seasonal trend of reference evapotranspiration was significantly decreasing over the period 1980–2021. The spatial distribution of Sen's slope percentage change was highest at Mansa station, followed by Sangrur station. Mann–Kendall trend analysis of annual and post-monsoon series revealed that out of a total of six stations, Barnala, Muktsar Sahib, and Sangrur showed a significant decreasing trend. The Sen's slope and ITA trend slope of monsoon series are statistically decreasing at 1% and 5% significance level all over the districts. In the pre-monsoon season, an increasing trend of RET was detected throughout all the stations, with the highest percentage change of 4.3% detected at Mansa station. The ITA trend slope of ET0 exhibited decreasing magnitude in the annual, monsoon, post monsoon except at pre-monsoon season all round the districts. While the contrasting trend is found in MK slope exhibited increasing and decreasing trend in the pre-monsoon season. The innovative trend slope revealed the presence of a hidden trend for RET that was missed by the traditional MK/MMK test. The study may guide planners and policymakers in the effective implementation of crop water management strategies to improve the status of water resources in Punjab. [ABSTRACT FROM AUTHOR]

Drylands, where the water supplies are scarce relative to the atmospheric moisture demands, occupy approximately half of the area of China. With global warming, the response of atmospheric water cycle is a crucial concern for sustainable development in China's drylands. This study investigates the characteristics of the water cycle in China's drylands during 1980–2019, as well as future projections estimated by the Community Earth System Model (CESM) during 2020–2100. The results show that the air temperature in China's drylands has increased significantly since 1980, especially after 2000, with greater warming in the warm season. Meanwhile, China generally tend to be drier from 1980 to 2019 as a whole, especially in the cold season. Both precipitation (P) and evapotranspiration (E) have increased, but the net effect is that drylands become drier (negative P-E) and wetlands become wetter (positive P-E), respectively. In the future, drylands are projected to become more humid due to increased precipitation, showing a pattern of "western wetter and eastern drier" during 2020–2100. These results could improve understanding of the water cycle and provide some guidance for adapting to climate change in drylands. [ABSTRACT FROM AUTHOR]

Global warming has had significant effects on the hydrological cycle. In North Africa, these effects have resulted in a continued decrease in the amount of annual precipitation, greatly influencing the availability of surface and groundwater resources. This paper aims to evaluate drought episodes in a long dataset from Djelfa (Algeria) using a statistical approach based on a decision support system enabled by the Hyfran-plus software, to fit the best statistical distribution model and predict non-exceedance probability of precipitation. The standardized precipitation index is used to highlight sequences of meteorological drought and changes in weather patterns. Shift in precipitation has been identified by Wilcoxon Test for homogeneity; Wold-Wolfowitz test of independence, Kendall's test of trend and new cumulative mean difference curve (CMD) developed to visualize the trend of the precipitation and runoff dataset, Autocorrelation function (ACF) and Fourier spectrum and Deuterium excess isotopes has been used to visualize trends. Log–log plot; the mean excess function (MEF), AIC and BIC criteria are used to select the best distribution fitting model. The statistical results obtained indicate that the dataset follows a heavy-tailed distribution (Pearson type III), Values of excess Deuterium indicate that groundwater recharge has occurred in cold weather different from the actual period. SPI analysis shows that dry years cover more than 51% compared to 49% of wet years. The CMD curve shows a change and trend in the precipitation and runoff time series since 1974. Forecasts show drought recurrences to be between 3 and 200 years. [ABSTRACT FROM AUTHOR]

Selin Co basin, a representative lake basin situated in the central region of the Tibetan Plateau (TP), is characterized by extensive areas of frozen ground and has undergone a remarkable expansion in its lake area. Evapotranspiration, as an important variable within the lake water cycle, as well as its influencing factors are still under debate at this basin. Actual evapotranspiration (ETa) plays a vital role in influencing land-atmosphere interaction processes and the hydrological cycle. By quantifying the amount of water that is actually transpired by vegetation and evaporated from soil surfaces, ETa provides important information about the mechanisms controlling evapotranspiration. In this study, the advection-aridity (AA) model was employed to estimate ETa in Selin Co basin. The estimated ETa and its influencing factors were investigated between 2001-2018, with an emphasis on examining both spatial and temporal trends. The results demonstrated that the multiyear mean ETa in the basin was 430.3 mm (excluding lakes) with an overall significantly decreasing trend (-5.8 mm/yr). In terms of its seasonal variation, ETa exhibited highest value during summer, while experiencing comparatively lower rates in autumn and spring. Furthermore, the spatial distribution of both the annual and seasonal ETa exhibited a similar decreasing trend from the southeast to the northwest of the basin. The sensitivity of several meteorological variables to modifications in ETa was also examined. Results indicated that specific humidity was the predominant variable, followed by net radiation, air temperature, precipitation, atmospheric pressure, and wind speed. In addition, the area covered by permafrost and seasonally frozen ground was approximately about 1.58 × 104 km2 and 4.22 × 104 km2 in the basin, and permafrost degradation in the northern region of the Selin Co basin resulted in increased average soil moisture content and underground ice melting, leading to a subsequent increase in ETa. [ABSTRACT FROM AUTHOR]

Satellite observations of column‐averaged water isotopes are relatively new retrieval products that are in need of further in situ evaluation. Such evaluation studies are generally difficult to perform due to the wide mismatch in temporal and spatial scales between the satellite observations based on instantaneous pixel averages during an overpass and airborne in situ measurements ranging up to several hours over a km‐scale. In addition, topography, weather conditions and in particular cloudiness impose severe constraints on an exact collocation between satellite and airborne in situ measurement platforms. Here we present a new method that allows a comparison between in situ measurements and satellite observations of δD on a broader statistical basis. We use regional isotope‐enabled model simulations as intermediate information to identify the area for best comparisons. Applying our methodology to TROPOMI total column δD retrievals for the L‐WAIVE campaign in Annecy, France, during June 2019 increases the number of satellite pixels for comparison despite widespread cloudiness on average by a factor of 20. In addition, the comparison of simulated and observed δD revealed a dependency of the satellite evaluation on the structure of the middle and upper troposphere. We conclude that our method provides a more robust statistic basis for in situ evaluation of δD satellite retrievals. The method will thus be useful in planning and executing forthcoming validation and evaluation campaigns, and can potentially be used for the evaluation of other satellite products. Plain Language Summary: A characteristic of atmospheric water vapor is the concentration of stable heavy hydrogen and oxygen isotopes. Isotopic concentrations are observed by diverse techniques such as remote sensing from satellites and land‐based instruments, and direct measurements from aircrafts, ships and stations on land. These measurements lead to a variety of data sets which span different distances (from a few to hundreds of km) and time periods (from seconds to days). While remote measurements provide data of a large spatial and temporal coverage at a coarse resolution, direct measurements are often obtained during research campaigns over a limited time period with high spatial and temporal resolution. Especially the later data sets are of high value as they describe the atmospheric state in high detail. In this study we develop a method to extrapolate direct, campaign based high‐quality measurements of water vapor to the largest possible representative area using output from a numerical weather simulation. This allows us to compare remotely sensed and direct isotope measurements. This comparison illustrates how to interpret total column measurement and to identify where the model has difficulties to correctly simulate the vertical isotope distribution. This knowledge is of use for future application of remotely sensed data sets and model development. Key Points: New, expanded collocation criterion provides larger data sets for comparison of δD observations during a field campaignWe evaluate TROPOMI δD column retrievals with in situ airborne measurements using a COSMOiso‐based collocation criterionThe combination of subcolumn and total column averaged δD is used to characterize vertical δD gradients and reveal model biases [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article examines the effects of climate change on hydrological cycle, water availability, agricultural production, and energy usage in India. Topics discussed include explanation on hydrological cycle, how climate change affects water availability, and effect of climate on groundwater zones. Also mentioned are the effect of climate change on recharge and discharge and effects of climate change on groundwater quality.

The dynamic replacement of soil organic carbon represents a pivotal mechanism through which water erosion modulates soil–atmosphere CO2 fluxes. However, the extent of this dynamic replacement of soil inorganic carbon within this process remains unclear. In our study, we focused on Yuanmou County, China, a prototypical region afflicted by water erosion, as our study area. We leveraged the WaTEM/SEDEM model to quantify the dynamic replacement of soil carbon, accounted for the average annual net change in soil carbon pools, and used isotope tracer techniques to track and measure the process of the coupled carbon–water cycling. This comprehensive approach enabled us to scrutinize the dynamic replacement of soil carbon under water erosion and delineate its ramifications for the carbon cycle. Our findings unveiled that the surface soil carbon reservoir in the Yuanmou area receives an annual replacement of 47,600 ± 12,600 tons following water erosion events. A substantial portion, amounting to 39,700 ± 10,500 tons, stems from the dynamic replacement of soil inorganic carbon facilitated by atmospheric carbon. These results underscore the critical role of the dynamic replacement of soil inorganic carbon in altering the soil–atmosphere CO2 fluxes under water erosion, thereby influencing the carbon cycle dynamics. Consequently, we advocate for the integration of water erosion processes into regional carbon sink assessments to attain a more comprehensive understanding of regional carbon dynamics. [ABSTRACT FROM AUTHOR]

Applying green infrastructure measures helps to retain water in the land during wet periods, which in turn makes it more available during periods of drought. Water retention reduces the volume of rainwater that transforms into surface runoff, allowing for the increase in the intensity of evapotranspiration and infiltration, which helps to establish a catchment with a balanced hydrologic cycle that's effectively more resistant to the consequences of climate change. With increasing popularity of introducing low impact development (LID) solutions in highly urbanised catchments characterised by a high runoff coefficient, it is important also to reduce rainwater runoff in residential areas with lower density of housing. This work presents a numerical assessment of green infrastructure (green roofs, raingardens, permeable paving and rainwater harvesting) performance in increasing retention in a catchment area consisting of single-family houses. The numerical model of potential residency in Ożarów, Poland was developed in SWMM 5.2. software, replicating local conditions with input infiltration data collected through on site and laboratory testing, as well as data gathered during a period of registering local evaporation and precipitation conditions. After running a series of simulations of three rain events, varying in their duration and intensity, the model was enhanced with green infrastructure solutions by the utilisation of LID Controls option in SWMM. With rainfall simulations resulting in varying rainwater outflow hydrographs and with differences in the volume of collected rainwater outflow, the results of LID application were consistent with the reduction of the peak rainwater outflow (reduction rate 61.90-67.99%), as well as the decrease in rainwater outflow volume (reduction rate 61.17-62.12%). This research promotes the hydrologic effectiveness of introducing green infrastructure in low density housing establishments. [ABSTRACT FROM AUTHOR]

Copyright of Karaelmas Science & Engineering Journal / Karaelmas Fen ve Mühendislik Dergisi is the property of Karaelmas Science & Engineering Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In addition to traditional isotopes, non-traditional isotopes have gradually been applied in the hydrosphere, such as lithium, strontium, magnesium, etc. Magnesium is one of the main elements in the earth's crust and participates in most geophysical and chemical processes. In seawater, the δ26Mg value is -0.82‰ and relatively constant, which determines that the magnesium isotope composition of terrestrial water from seawater recharge is relatively consistent. This provides a constant initial isotope scale for studying water cycle processes and can be used as an ideal tracer element for groundwater research. Through comparative analysis of magnesium isotope composition characteristics and water cycle processes it is shown that the fractionation range of magnesium isotopes can reach 3.5‰, and they have different compositional characteristics in surface water and groundwater. In the process of groundwater rock interaction, magnesium isotopes undergo fractionation, providing valuable information for identifying mineral phase evolution. Magnesium isotopes follow the law of mass dependent fractionation. Therefore, in the process of groundwater infiltration and runoff, magnesium isotope fractionation caused by ion exchange and cohesive soil formation is easier for lighter magnesium isotopes to migrate to heavier magnesium isotopes. This provides the potential for magnesium isotopes to be used to study salt transport and the formation process of clay minerals. [ABSTRACT FROM AUTHOR]

During the early Holocene to mid-Holocene, about 11 500 to 5500 years ago, lakes expanded across the Sahel and Sahara in response to enhanced summer monsoon precipitation. To investigate the effect of these lakes on the West African summer monsoon, previous simulation studies prescribed mid-Holocene lakes from reconstructions. By prescribing mid-Holocene lakes, however, the terrestrial water balance is inconsistent with the size of the lakes. In order to close the terrestrial water cycle, we construct a dynamic endorheic lake (DEL) model and implement it into the atmosphere–land model ICON-JSBACH4. For the first time, this allows us to investigate the dynamic interaction between climate, lakes, and vegetation across northern Africa. Additionally, we investigate the effect of lake depth changes on mid-Holocene precipitation, a neglected aspect in previous simulation studies. A pre-industrial control simulation shows that the DEL model realistically simulates the lake extent across northern Africa. Only in the Ahnet and Chotts basins is the lake area slightly overestimated, which is likely related to the coarse resolution of the simulations. The mid-Holocene simulations reveal that both the lake expansion and the vegetation expansion cause a precipitation increase over northern Africa. The sum of these individual contributions to the precipitation is, however, larger than the combined effect that is generated when lake and vegetation dynamics interact. Thus, the lake–vegetation interaction causes a relative drying response across the entire Sahel. The main reason for this drying response is that the simulated vegetation expansion cools the land surface more strongly than the lake expansion, which is dominated by the expansion of Lake Chad. Accordingly, the surface temperature increases over the region of Lake Chad and causes local changes in the meridional surface-temperature gradient. These changes in the meridional surface-temperature gradient are associated with reduced inland moisture transport from the tropical Atlantic into the Sahel, which causes a drying response in the Sahel. An idealized mid-Holocene experiment shows that a similar drying response is induced when the depth of Lake Chad is decreased by about 1–5 m , without changing the horizontal lake area. By reducing the depth of Lake Chad, the heat storage capacity of the lake decreases, and the lake warms faster during the summer months. Thus, in the ICON-JSBACH4 model, the lake depth significantly influences the simulated surface temperature and the simulated meridional surface-temperature gradient between the simulated lakes and vegetation, thereby affecting mid-Holocene precipitation over northern Africa. [ABSTRACT FROM AUTHOR]

The optimal low impact development (LID) design for restoring the water cycle within watersheds considering climate change is crucial for adaptation to future climate change. In this study, a practical and effective allocation method for permeable pavement was proposed to restore the water cycle within watersheds considering future climate change. A total of 15 general circulation models (GCMs) of the Coupled Model Intercomparison Project (CMIP) Phase 6 were used to simulate future climate variables according to two shared socioeconomic pathway (SSP) scenarios. The stormwater management model (SWMM) was employed for long-term hydrological simulation. The installation priority of permeable pavement in sub-watersheds was robustly determined using coupled fuzzy TOPSIS and VIKOR methods. The results of this study confirmed that the different climate predictions of each GCM could affect the prioritization results. Furthermore, it was confirmed that the allocation method adopted in this study improved water cycle restoration more effectively than when allocating the available capacity at once according to priority. The results of this study could help accurately determine the LID capacity of each sub-watershed under limited resources. [ABSTRACT FROM AUTHOR]

Seasonal climate variations (SCV) have a significant impact on the exchange of surface and groundwater in the reservoir area. As a crucial climatic element, temperature also has an important effect on the hydrological cycle. In the plain reservoir area, the hysteresis response of groundwater in the aquitard to reservoir level (RL) fluctuations is ever-present. To study the impacts of SCV on the hysteresis response of groundwater in the aquitard, the response of groundwater level (GL) of Jiangxiang Reservoir to the variation of the RL was examined. Considering the seasonal temperature variations (STV), the hydraulic diffusivity of the aquitard was calculated. Relying on the STV, the formula for calculating the variation of the GL with the RL was derived. The results showed that the hydraulic diffusivity is sensitive to temperature changes. The higher the temperature, the greater the hydraulic diffusivity, which results in a faster response of groundwater to changes in reservoir level. Additionally, the lag of groundwater level change in the aquitard became smaller. Considering STV, the calculated immersion scope with variable parameters was smaller than that with constant parameters. [ABSTRACT FROM AUTHOR]

The changing climate and intensifying human activities have made an impact on the hydrological processes in the upper Yangtze River (UYR), but quantifying their effects remains uncertain. This study used the Budyko framework to investigate the response of runoff (Q) to climate change and human activities during 1956–2017 and evaluate the impacts of human activities, including land use/cover change, water use, dam construction, and vegetation change, on watershed characteristic. Results show that climate change is the dominant driver of Q variations in the Wujiang River (WJR), Jialing River (JLR), and Jinsha River (JSR) watersheds, with contributions of 58.6%, 66.9%, and 67.6%, respectively. However, in Mingjiang River (MJR) and UYR watersheds, human activities contribute more to Q variations with 55.2% and 51.2%, respectively. Human activities play important roles in variation of watershed characteristics, and they can explain 22%, 26%, 36%, 25%, and 53% of the watershed character change in UYR, WJR, JLR, MJR, and JSR, respectively. This study conducts a comprehensive analysis of the causes of Q change in UYR, and provides a new perspective to explore the effects of specific human activities on watershed characteristics. Plain Language Summary: With climate change and intensifying human activities, the water cycle has been changed. Runoff is an essential component of the water cycle, and its response to changing environments has drawn broad attention. This study aims to quantify the contributions of climate change and human activities to runoff changes in the upper Yangtze River (UYR) and its four sub‐watersheds over the past half‐century. According to the results, human activities and climate change have been responsible for approximately 51.2% and 48.8% of the observed runoff changes in UYR, respectively. It suggests that both human activities and climate change have played significant roles, and their contributions are remarkably comparable. In addition, the impacts of human activities on watershed environment changes are analyzed. The results suggest that increased settlement area and industrial water use are the dominant influencing factors. Key Points: Human activities and climate change have made comparable contributions to the runoff reduction in the upper Yangtze RiverWater use, land use/cover change, vegetation change, and dam construction together explain 22% of the watershed environment changesHuman settlements and increased industrial water use have been the principal factors contributing to the changes in watershed environment [ABSTRACT FROM AUTHOR]

Transpiration plays a vital role in determining the watershed water cycle. However, we still have little knowledge of the characteristics of tree transpiration in the Hanjiang River Basin, which is the water source for the middle route of South‐to‐North water diversion project. Here, we measured sap flux density of oak trees (Quercus, the dominant species here) at the 10‐min resolution for 2 years and explored its response to the environmental conditions. The incoming short‐wave radiation and vapour pressure deficit well explained the variation of daytime sap flux density, and a statistical model was then proposed to calculate the daytime sap flux density correspondingly; then a nighttime sap flux density module was proposed based on the daytime sap flux density calculation. Sap flux density showed clear counter‐clockwise hysteresis response to incoming short‐wave radiation, and clockwise hysteresis response to vapour pressure deficit. Our sap flux density model can well reproduce the corresponding hysteresis response to incoming short‐wave radiation and vapour pressure deficit. This study unravelled the environmental controls of sap flux density of the oak trees in the Hanjiang River Basin, proposed an efficient model for the sap flux density simulation, provided important knowledge for understanding the corresponding forests' water use, which is of critical significance in determining the water availability for the middle route of the South‐to‐North water diversion project. [ABSTRACT FROM AUTHOR]

Forest trees greatly influence both the routing of water downward into the subsurface and the re‐routing of water upward through water uptake and transpiration. To reveal how the subsurface soil water pools used by trees change across seasons, we analysed 2 years of stable isotope ratios of precipitation, soil water from different depths (using both bulk sampling and suction‐cup lysimeters), and xylem in a mixed beech and spruce forest. Precipitation as well as mobile and bulk soil waters all showed a distinct seasonal signature; the seasonal amplitude decreased with depth, and mobile soil waters fluctuated less than bulk soil waters. Xylem water signatures in both tree species were similar to the bulk soil water signatures and rather different from the mobile soil water signatures. The beech and spruce trees had different isotope ratios, suggesting the use of different water sources, and these differences were larger under dry antecedent conditions than wet antecedent conditions. Despite these differences, both species predominantly transpired waters with a winter‐precipitation isotopic signature throughout the summer, including during wet conditions when more recent precipitation was available. Over most of the sampling dates, the fraction of recent precipitation (i.e. from the preceding 30 days) in xylem water was low, despite both species typically demonstrating the use of both shallow and deeper soil waters. These results provide evidence that the soil water storages used by these trees are largely filled in winter and bypassed by recent precipitation, implying long residence times. [ABSTRACT FROM AUTHOR]

We investigate a new event of accelerated environmental change that was recorded during the late Barremian in the pelagic Subbetic Basin (Western Tethys). Two pelagic sections have been studied using a multi-proxy approach based on C-isotope stratigraphy and a high-resolution quantitative study of nannofossil assemblages, along with major and trace elements and biomarkers. Our results provide a detailed biostratigraphy and C-isotope stratigraphy, and outline the paleoenvironmental conditions recorded during the early stages of the Taxy Episode. A disturbance has been identified in the C-isotope record, called the IFeNE (Intra-Feradianus negative C-excursion), which is coeval with environmental and biotic changes that predate the well-known ISNE (Intra-Sarasini negative C-excursion). The combined analysis of nannofossil associations, C-isotopes, major and trace elements, and biomarker distributions indicates a separate episode of warming heralding the ISNE, resulting in the acceleration of the hydrological cycle and a consequent increase in continental inputs and the fertilization of surface waters. The origin of the Taxy Episode (the IFeNE and ISNE) has been related to orbital factors (high-eccentricity cycles), and to a global increase in volcanism, probably related to the early phases of the Ontong Java Plateau. [ABSTRACT FROM AUTHOR]

For the first time, the AGRUM model consortium—consisting of the agro-economic model RAUMIS, the water balance model mGROWA, the hydrological nutrient transport models DENUZ, WeKu and MEPhos, and the urban emission model MONERIS—was jointly set up throughout Germany (357,000 km2). This provided a nationwide consistent nutrient model to capture the current status of N and P inputs to surface waters from diffuse sources and urban areas. Diffuse nutrient emissions were quantified in high spatial resolution for the input pathways' groundwater, drainage runoff, and natural interflow (100 m × 100 m), as well as for water erosion and wash-off (25 m × 25 m). The sum of diffuse nutrient inputs to surface waters is about 385,000 metric tons N/yr and ca. 11,530 metric tons P/yr. Urban emissions were quantified either as point source inputs (wastewater treatment plants, industrial direct dischargers) or at municipality scale for different collection and treatment systems, e.g., rainwater sewers or decentralized treatment plants, and sum up to ca. 95,000 t N/yr and 7500 t P/yr. As modelled, total N and P inputs into surface waters correspond well with observed N and P loads in rivers. The model results represent valuable information for water managers, being responsible for the preparation of management plans for the third management cycle of the EC Water Framework Directive spanning from 2021 to 2027. [ABSTRACT FROM AUTHOR]

Stable isotopes in natural water bodies serve as hydrologic tracers, with a history of extensive application in karst groundwater research. The present paper is a systematic review of previous research results, with the objective of sorting out and summarizing the stable isotopic characteristics of karst groundwater in southwest China, which is the most typical karst region worldwide. Comprehensive analysis reveals that the deuterium and oxygen isotope values of most karst groundwater are characterized temporally as 'enriched in the rainy season and depleted in the dry season', which is the opposite of the pattern of precipitation. While the spatial distribution feature is basically consistent with the spatial variation pattern of precipitation, which is characterized as 'depleted from the coast to the interior'. Additionally, the main applications of stable isotopes to karst groundwater are discussed, including karst groundwater recharge source and recharge elevation identification, research on karst groundwater in the hydrological cycle, the hydrological process of karst groundwater, and karst groundwater contamination tracking. Finally, we looked forward to future research on karst groundwater based on deuterium and oxygen isotopes. It is our hope that this review may provide insight into the study of karst groundwater. [ABSTRACT FROM AUTHOR]

Large spatio‐temporal gradients in the Congo basin vegetation and rainfall are observed. However, its water‐balance (evapotranspiration minus precipitation, or ET − P) is typically measured at basin‐scales, limited primarily by river‐discharge data, spatial resolution of terrestrial water storage measurements, and poorly constrained ET. We use observations of the isotopic composition of water vapor to quantify the spatio‐temporal variability of net surface water fluxes across the Congo Basin between 2003 and 2018. These data are calibrated at basin scale using satellite gravity and total Congo river discharge measurements and then used to estimate time‐varying ET − P over four quadrants representing the Congo Basin, providing first estimates of this kind for the region. We find that the multi‐year record, seasonality, and interannual variability of ET − P from both the isotopes and the gravity/river discharge based estimates are consistent. Additionally, we use precipitation and gravity‐based estimates with our water vapor isotope‐based ET − P to calculate time and space averaged ET and net river discharge within the Congo Basin. These quadrant‐scale moisture flux estimates indicate (a) substantial recycling of moisture in the Congo Basin (temporally and spatially averaged ET/P > 70%), consistent with models and visible light‐based ET estimates, and (b) net river outflow is largest in the Western Congo where there are more rivers and higher flow rates. Our results confirm the importance of ET in modulating the Congo water cycle relative to other water sources. Plain Language Summary: Rainfall and vegetation vary substantially across the Congo Basin. However, the spatial variations, seasonality, and interannual variability of the net water balance, (the difference between evapotranspiration and rainfall) is not well quantified. Atmospheric observations of the isotopic composition of water vapor are sensitive to the balance of evapotranspiration (ET) and precipitation (P). We calibrate new observations of the isotopic composition of water vapor to ET − P that is based on satellite gravity measurements and ground‐based river discharge measurements to quantify ET − P across four quadrants of the Congo basin. When combined with satellite measurements of rainfall, we show that ET is the largest source of Congo basin water vapor. As ET is about 70% of observed rainfall, vegetation therefore plays an outsized role on the Congo water cycle. Additionally, when combined with satellite measurements of gravity, we show that river discharge is higher in the western part of the basin, where there are more rivers and stronger flows. Key Points: Water vapor isotopes provide a reliable proxy for evapotranspiration (ET) minus precipitation (P) in the Congo BasinET contributes over 70% to P within the four quadrants of the Congo BasinRiver discharge is highest in the western part of the basin, where there are more rivers and higher flow [ABSTRACT FROM AUTHOR]

The study of the water cycle in the forest at large scales, such as countries, is challenging due to the difficulty of correctly estimating forest water flows. Hydrological models can be coupled with extensive forest data sources, such as national forest inventories, to estimate the water flow of forests over large extents, but so far the studies conducted have not analysed the role of stand structure variables or the functional traits of the forest on predicted blue and green water flows in detail. In this study, we modelled the water balance of Spanish forests using stand structure and species data from forest inventories to understand the effects of climate, stand structure, and functional groups on blue water flows. We calculated blue water and green water flows and expressed them relative to received precipitation. Relative blue water flow was mainly concentrated in the wetter regions (Atlantic and alpine biomes) of Spain (around 25 %) in comparison with the Mediterranean biomes (10 %–20 %) and during the autumn–winter season. The leaf area index (LAI) of the forest stand is the most important predictor of relative blue water, exhibiting a negative effect until it reaches a plateau at higher levels (around 2.5–3). Deciduous forests showed a greater relative blue water flow than evergreen functional groups (25 %–35 % and 10 %–25 %, respectively) primarily due to leaf fall during the autumn–winter season. This study highlights how green water is decoupled from blue water; namely, blue water depends on winter and autumn precipitation, while green water depends on the spring and summer water demand and how the species' functional traits (deciduous vs. evergreen) can influence blue water production. [ABSTRACT FROM AUTHOR]

The global terrestrial water storage (TWS), the most accessible component in the hydrological cycle, is a general indicator of freshwater availability on Earth. The global TWS trend caused by climate change is harder to detect than global mean temperature due to the highly uneven hydrological responses across the globe, the brevity of global freshwater observations, and large noises of internal climate variability. To overcome the climate noise and small sample size of observations, we leverage the vast amount of observed and simulated meteorological fields at daily scales to project global TWS through its fingerprints in weather patterns. The novel method identifies the relationship between annual global mean TWS and daily surface air temperature and humidity fields using multi-model hydrological simulations. We found that globally, approximately 50% of days for most years since 2016 have climate change signals emerged above the noise of internal variability. Climate change signals in global mean TWS have been consistently increasing over the last few decades, and in the future, are expected to emerge from the natural climate variability. Our research indicates the urgency to limit carbon emission to not only avoid risks associated with warming but also sustain water security in the future. [ABSTRACT FROM AUTHOR]

Sulfate and nitrate aerosols degrade air quality, modulate radiative forcing and the hydrological cycle, and affect biogeochemical cycles, yet their global cycles are poorly understood. Here, we examined trends in 21 years of aerosol measurements made at Ragged Point, Barbados, the easternmost promontory on the island located in the eastern Caribbean Basin. Though the site has historically been used to characterize African dust transport, here we focused on changes in nitrate and non-sea-salt (nss) sulfate aerosols from 1990–2011. Nitrate aerosol concentrations averaged over the entire period were stable at 0.59 µ g m -3 ± 0.04 µ g m -3 , except for elevated nitrate concentrations in the spring of 2010 and during the summer and fall of 2008 due to the transport of biomass burning emissions from both northern and southern Africa to our site. In contrast, from 1990 to 2000, nss-sulfate decreased 30 % at a rate of 0.023 µ g m -3 yr -1 , a trend which we attribute to air quality policies enacted in the United States (US) and Europe. From 2000–2011, sulfate gradually increased at a rate of 0.021 µ g m -3 yr -1 to pre-1990s levels of 0.90 µ g m -3. We used the Community Multiscale Air Quality (CMAQ) model simulations from the EPA's Air QUAlity TimE Series (EQUATES) to better understand the changes in nss-sulfate after 2000. The model simulations estimate that increases in anthropogenic emissions from Africa explain the increase in nss-sulfate observed in Barbados. Our results highlight the need to better constrain emissions from developing countries and to assess their impact on aerosol burdens in remote source regions. [ABSTRACT FROM AUTHOR]

[Display omitted] Estimation of evapotranspiration (ET a) change on the Tibetan Plateau (TP) is essential to address the water requirement of billions of people surrounding the TP. Existing studies have shown that ET a estimations on the TP have a very large uncertainty. In this article, we discuss how to more accurately quantify ET a amount and explain its change on the TP. ET a change on the TP can be quantified and explained based on an ensemble mean product from climate model simulations, reanalysis, as well as ground-based and satellite observations. ET a on the TP experienced a significant increasing trend of around 8.4 ± 2.2 mm (10 a)−1 (mean ± one standard deviation) during 1982–2018, approximately twice the rate of the global land ET a (4.3 ± 2.1 mm (10 a)−1). Numerical attribution analysis revealed that a 53.8% TP area with the increased ET a was caused by increased temperature and 23.1% part was due to soil moisture rising, because of the warming, melting cryosphere, and increased precipitation. The projected future increase in ET a is expected to cause a continued acceleration of the water cycle until 2100. [ABSTRACT FROM AUTHOR]

Chemical equilibrium represents the highest efficiency achievable by a thermochemical cycle under specific operational conditions. This study delves into two-step thermochemical water splitting cycles, which dissociate water into hydrogen (H 2) and oxygen (O 2) via sequential thermal reduction and re-oxidation processes. Building on the thermal reduction analysis presented in Part 1, this paper zeroes in on the re-oxidation reaction within the optimal reactor framework – the counter-current reactor. It elucidates the equilibrium pathway, delineating the progression of chemical equilibrium at each incremental stage of re-oxidation. Using ceria (CeO 2) as a model redox-active metal oxide, the investigation analyzes the influence of operational parameters on the re-oxidation reaction. Findings reveal the theoretical feasibility of maintaining near constant temperature (±2.5 °C) during re-oxidation, achieving a total extent of reduction of 0.038 and a hydrogen conversion yield of 32%. While near adiabatic operation is also achievable, practicality is constrained by a maximum total extent of reduction of 6.5·10−3. The study also explores the economic implications of thermochemical water splitting, particularly focusing on the steam-to-hydrogen output ratio. It highlights the severe economic hurdles associated with hydrogen yields below approximately 1%. Furthermore, the investigation reveals that the addition of inert gas to the re-oxidation step offers no significant advantages. Concluding the analysis, a comparative assessment exposes negligible differences in outcomes when substituting carbon dioxide (CO 2) for water (H 2 O) as the oxidant in low-temperature scenarios (800 °C). This comprehensive study not only advances the understanding of re-oxidation dynamics in thermochemical water splitting but also informs practical and economic considerations crucial for the advancement of this technology. • Reversible/equilibrium re-oxidation pathway defined for water splitting cycles. • Reversible quasi-constant temperature and quasi-adiabatic re-oxidation is feasible. • Limited impact of gas purity on re-oxidation at fixed flow/minimum temperature. • Inert gas addition offers no thermodynamic advantage in re-oxidation. • Low re-oxidation temperatures expand the solution space for high cycle efficiency. [ABSTRACT FROM AUTHOR]

Changes in precipitation and its causes under future warming scenarios in Northwest China are of great concern. Based on the dynamical downscaling results of the Weather Research and Forecasting model (WRF), this study quantitatively identified the contribution of local evaporation and external moisture transport to future precipitation changes in western and eastern Northwest China (WNWC and ENWC) by calculating the precipitation recycling ratio (PRR). The results showed that the WRF could reasonably reproduce the observed spatial and temporal distribution of precipitation and evaporation during the historical reference period of 1985–2014. Under the 1.5 and 2.0°C stabilized warming scenarios from 2071 to 2100, there is a stronger precipitation growth in WNWC than in ENWC, and the PRR generally increases in WNWC and decreases in ENWC. Further analysis indicates that external moisture transport is the dominant contributor to the increased precipitation in all cases with its contribution exceeding 70%, while the difference of precipitation growth in two sub‐regions arises from the summer moisture transport at the southern boundary as the inflow in WNWC and outflow in ENWC. Compared to the negligible contribution of evaporation in ENWC (less than 7%), evaporation contributes more than 23% to the precipitation increase in WNWC under future warming scenarios, which may be related to the strong land‐atmosphere coupling there. Furthermore, an additional warming of 0.5°C leads to an increase in precipitation for both sub‐regions, which is mainly due to the contribution of external moisture transport. Plain Language Summary: In this study, we discuss the relative contributions of evaporation and moisture transport to precipitation changes in Northwest China under 1.5/2.0°C stabilized warming scenarios. With Northwest China (NWC) dividing it into two sub‐regions of western and eastern parts, we find that although the western NWC has less precipitation during the reference period of 1985–2014, the increase in precipitation is about twice that of the eastern NWC under the warming scenarios. The contribution of evaporation to the increased precipitation is greater in the western NWC compared with the reference period, which may indicate the accelerating hydrological cycle in western NWC. Moisture transport is the main contributor to the increase in precipitation and is also the main reason for the difference in precipitation changes between the two sub‐regions, mainly due to differences in summer moisture transport across the southern boundary. This work provides a scientific basis for assessing water resources in Northwest China under future warming scenarios. Key Points: External moisture transport contributes more than 70% of precipitation in Northwest China, both in terms of mean and variabilityContribution of evaporation to the precipitation increase is stronger in western Northwest China, due to its strong land‐atmosphere couplingThe difference in moisture transport between the two regions is mainly due to changes in southern border moisture transport in summer [ABSTRACT FROM AUTHOR]

Mixed‐phase stratiform clouds contain numerous liquid, mixed‐phase, and ice clusters, quantifying the cluster scales is potentially helpful to improve the parameterizations of microphysics and radiation models. However, the scales of hydrometeor clusters at different levels of stratiform clouds are not well understood. In this study, using airborne measurements and a large eddy simulation, we show that turbulence plays an important role in controlling the clusters with length of a few hundred meters, while the scales of larger clusters have stronger vertical variations from cloud base to top. The liquid clusters are the largest near the cloud top, while the lengths of ice clusters decrease from cloud base to top. The lengths of mixed‐phase clusters depend on the glaciation process, a faster glaciation results in smaller mixed‐phase clusters. The results improve our understanding on how the liquid and ice are mixed at different levels in stratiform clouds. Plain Language Summary: Mixed‐phase clouds are vital to the global radiative balance and water cycle. The coexistence of liquid and ice, and the way they mix have significant impacts on the cloud microphysical properties. Observations suggest hydrometeors organize in clusters in mixed‐phase stratiform clouds, while such inhomogeneity is still poorly represented in models. In this study, using airborne measurements and model simulation, we analyzed the scales of liquid, mixed‐phase, and ice clusters at different levels in a stratiform cloud observed in Northeast China. The results suggest turbulence controls the scale of clusters with length of a few hundred meters, while larger clusters have stronger vertical variations. The results improve our understanding on the cluster scales of hydrometeors at different levels in stratiform clouds, and are potentially helpful to improve the parameterizations of microphysics and radiation. Key Points: Turbulence plays an important role in controlling the scale of hydrometeor clustersThe scales of liquid, mixed‐phase, and ice clusters have different height dependencies from cloud top to baseA faster glaciation process results in smaller mixed‐phase clusters [ABSTRACT FROM AUTHOR]

Accurate estimation and attribution of large‐scale changes in plant transpiration are critical to understand the impacts of vegetation dynamics on the terrestrial hydrological cycle. However, these aspects remain poorly understood due to the limited reliability of global transpiration products. Here we compile data from 101 site‐based transpiration measurements across the globe and use them to constrain three biophysically based data‐driven transpiration products. The constrained transpiration reveals a prominent increasing trend of 0.61–0.79 mm yr−2 during 1980–2021, which is overestimated by 8%–32% in unconstrained transpiration. We further find that the global transpiration increase is mainly driven by leaf area index increase (40%), followed by climate change (19%), though offset partly by CO2‐induced stomatal closure (−38%) and land use and cover change (−3%). Our refined estimates indicate a less substantial increase of global transpiration than previously thought, improving the understanding of transpiration change impact on global hydrological cycle. Plain Language Summary: As a major component of terrestrial evapotranspiration, plant transpiration plays a critical role in global hydrological cycle and climate. However, transpiration and its changes are far from constrained due to the lack of field observations. By compiling a large number of in situ transpiration measurements, we correct three widely used transpiration products using the in situ data (i.e., constraints). We find that the original transpiration trend reflects an overestimation by 8%–32% compared to our constrained results, indicating that cautions should be taken when using the unconstrained products to detect transpiration trend. By combining five land surface models, we further find that the transpiration increase is mainly driven by leaf area index increase and climate change, whereas CO2‐induced stomatal closure and land use and cover change offset a considerable part of this increase. Our results improve the understanding the transpiration changes and the underlying drivers over the past four decades. Key Points: We compile data from 101 site‐based transpiration measurements across the globe and use them to constrain three transpiration productsConstrained transpiration reveals an increasing trend of 0.61–0.79 mm yr−2, while original transpiration overestimates this trend by 8%–32%Global transpiration increase is mainly driven by LAI increase and climate change, through offset partly by stomatal closure and LUCC [ABSTRACT FROM AUTHOR]

The meridional overturning circulation (MOC) in the ocean is a key player in the global climate system, while continental topography provides an essential backdrop to the system. In this study, we design a series of coupled model sensitivity experiments to investigate the influence of various mountain ranges on the global thermohaline circulation. The results highlight the influence of the Tibetan Plateau (TP) on the global thermohaline circulation. It emerges as a requisite for establishing the Atlantic MOC (AMOC) and a determining factor for the cessation of the Pacific MOC (PMOC). Additionally, the Antarctic continent plays a vital role in facilitating the TP to form the AMOC. While the formation of the AMOC cannot be attributed to any single mountain range, the TP alone can inhibit the PMOC's development. By modifying the global hydrological cycle, the TP is likely to have been crucial in molding the global thermohaline circulation. This paper presents quantitative evaluation of the role of different continental mountains in shaping the global meridional overturning circulation. The Tibetan Plateau is likely to have been crucial in molding the global thermohaline circulation. [ABSTRACT FROM AUTHOR]

Global climate change is considered one of the greatest environmental threats in the world. It is expected to significantly change the global hydrological cycle. The two main water cycle components, potential evapotranspiration (PET) and precipitation (P), are closely related to vegetation dynamics. In this study, the partial correlation analysis method was used to analyzed the relationship between Normalized Difference Vegetation Index (NDVI) and climate factors (PET and P) based on grid cells. PET was calculated by FAO-56 Penman-Monteith method. Moreover, we also investigated the NDVI and climate factors in different vegetation cover types. The results showed that grassland, forest and cropland in China were positively correlated with PET and P. The time scales of the maximum partial correlation coefficients between NDVI and PET of grassland vegetation were mostly longer than 5-6 months. These time scales were longer than the time scales related to P. The partial correlation coefficients between NDVI and PET, P of forest vegetation were higher in northern China, whereas the spatial distribution of related time scales was the opposite. The partial correlation coefficients between NDVI and PET, P of forest vegetation were higher in northern China. However, the spatial distribution of related time scales was the opposite. The correlations between NDVI and PET, P of cropland vegetation and the time scales related to PET had clear spatial heterogeneity. The time scale of the correlation between NDVI and P for cropland in the northern China was about 2 months. P had a strong influence on the growth of various types of vegetation in the study area, and grassland vegetation was affected by P over the shortest time scale. We compare and analyze the results of this study with other related studies. These results provide a reference for exploring the dynamic changes in different vegetation types and factors impacting them. [ABSTRACT FROM AUTHOR]

[Display omitted] • High sugar, protein of sludge shows outstanding biodrying potential. • Low ventilation rate improved bio-drying cycle and water removal effect. • Revealed the contribution of different water types to water removal. • Lipid degradation role: Crucial for releasing and transforming bound water. • Energy-saving ventilation changes the degradation sequence of organic matter. The effectiveness of dehydration and utilization processes for citric acid dewatered sludge is hampered by its high concentrations of polysaccharides, proteins, and water-binding properties of microbial extracellular polymers (EPS). This research explores the efficacy and mechanisms involved in extracting water from this type of sludge using biological drying technology, with varying rates of ventilation. Especially pertinent was the use of low ventilation rates as control variables. Our results suggest that a scheduled intermittent ventilation at lower rates allows for the most efficient removal of water, achieving a rate of 41.71 % within eight days, according to the zero-order kinetic model. Remarkably, the peak temperature registered was 60 °C, reaching this threshold in just 0.1 days and maintaining high temperatures for approximately 5.9 days. Component analysis of organic matter illustrated a preferential degradation process for lipids under these ventilation conditions which is pivotal for releasing and transforming bound water for efficient extraction, as well as facilitating the breakdown of easily hydrolysable materials. Further, polysaccharide/protein (EPS) decomposition contributed to water removal, though less significantly. The periodic ventilation strategy allowed for the maximum cumulative temperature to be sustained, demonstrating superior efficiency in harnessing bio-generated heat (82.77 % for water evaporation), resulting in dry sludge suitable for self-sustained combustion at relatively low cost ($26.61/t). Highlighted by this study is the considerable potential of energy-efficient ventilation methods in the biological drying treatment of citric acid fermented sludge and similar industrial waste materials. [ABSTRACT FROM AUTHOR]

Lakes are essential components of the terrestrial water cycle. Their size and quantity reflect natural climate change and anthropogenic activities in time. Lakes on the Inner-Mongolian Plateau (IMP) have experienced significant changes in recent decades, but the current situation remains elusive. In this study, we conducted multi-decadal intensive monitoring of lake area and performed comprehensive variation analysis on the IMP. The study involved pre-processing, lake area extraction, post-processing, and lake area analysis procedures using multi-source satellite images. The results reveal the detailed variation in the lake from various aspects. The temporal analysis indicates that the lake area has undergone two distinct periods of decline followed by subsequent increase, and the variation pattern from January to December was diverse. The spatial analysis suggests that the lake area expanded slightly in the western and southern parts, while the area shrank in the other two. Variations in lakes of different sizes exhibited spatial heterogeneity. To some extent, effective actions have led to lake rehabilitation, but it has not yet reached or surpassed the level of 2000. This study provides a substantial data basis and technological guidance for conducting lacustrine surveys. The results can play important roles in fostering further analyses of the water cycle and the carbon cycle. [ABSTRACT FROM AUTHOR]

The feedback of vegetation on cloud cover is an important link in the global water cycle. However, the relative importance of vegetation and related factors (surface properties, heat fluxes, and environmental conditions) on cloud cover in the context of greening remains unclear. Combining the Global Land Surface Satellite (GLASS) leaf area index (LAI) product and the fifth-generation reanalysis data of the European Centre for Medium-Range Weather Forecasts (ERA5), we quantified the relative contribution of vegetation and related factors to total cloud cover (TCC) in typical regions (Eastern European Plain, Western Siberian Plain, Mongolian Plateau, and Northeastern China Plain) of Eurasia over 21 years, and investigated how vegetation moderated the contribution of the other factors. Here, we show that the relative contribution of different factors to TCC was closely related to the climate and vegetation characteristics. In energy-limited (moisture-limited) areas, temperature (relative humidity) was more likely to be the factor that strongly contributed to TCC variation. Except for sparsely vegetated ecosystems, the relative contribution of LAI to TCC was stable within a range of 8–13%. The case study also shows that vegetation significantly modulated the contribution of other factors on TCC, but the degree of the regulation varied among different ecosystems. Our results highlight the important influence of vegetation on cloud cover during greening, especially the moderating role of vegetation on the contribution of other factors. [ABSTRACT FROM AUTHOR]

The surface energy budget plays a critical role in terrestrial hydrological and biogeochemical cycles. Nevertheless, its highly spatial heterogeneity across different vegetation types is still missing in the ORCHIDEE-MICT (ORganizing Carbon and Hydrology in Dynamic EcosystEms–aMeliorated Interactions between Carbon and Temperature) land surface model. In this study, we describe the representation of a tiling energy budget in ORCHIDEE-MICT and assess its short-term and long-term impacts on energy, hydrology, and carbon processes. With the specific values of surface properties for each vegetation type, the new version presents warmer surface and soil temperatures (∼ 0.5 °C , + 3 %), wetter soil moisture (∼ 10 kgm-2 , + 2 %), and increased soil organic carbon storage (∼ 170 PgC , + 9 %) across the Northern Hemisphere. Despite reproducing the absolute values and spatial gradients of surface and soil temperatures from satellite and in situ observations, the considerable uncertainties in simulated soil organic carbon and hydrological processes prevent an obvious improvement in the temperature bias existing in the original ORCHIDEE-MICT model. However, the separation of sub-grid energy budgets in the new version improves permafrost simulation greatly by accounting for the presence of discontinuous permafrost types (∼ 3×106 km2), which will facilitate various permafrost-related studies in the future. [ABSTRACT FROM AUTHOR]