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Accurate simulation and reliable projection of temperature and precipitation over China under climate change is important for proposing adaptation measures for future natural ecosystems. This study proposes a novel method to construct an optimal reliability ensemble averaging (REA) subset from the Coupled Model Intercomparison Project Phase 6 (CMIP6) based on their historical performance in simulating temperature and precipitation across different subregions. The optimal REA ensemble outperforms the multi‐model ensemble mean (MMEM) and single optimal model in reproducing the spatial patterns of historical annual mean temperature and precipitation over China from 1985 to 2014. Under the examined Shared Socioeconomic Pathway scenarios (SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5), the REA projects persistent warming and increased precipitation towards the end of the 21st century, intensifying under higher emissions. Nationwide mean temperature rises of 1.39, 2.69 and 5.05°C, and precipitation increases of 9%, 10% and 20% are projected in the long‐term (2081–2100) relative to 1995–2014 under SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5 scenarios, respectively. Northwestern China and the Tibetan Plateau are expected to experience amplified warming and precipitation increases, respectively. Compared to the MMEM, the REA generally indicates reduced warming but larger precipitation increases, especially over the Tibetan Plateau under higher‐emissions scenarios. The REA exhibits lower projection uncertainty than the MMEM for both temperature and precipitation, primarily attributed to reduced internal variability. The novel optimal framework for REA shows the potential for extracting robust regional climate information applicable to different subregions of China. This study may contribute to new comprehension of future climate change over China. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) partitioning distinguishes the soil evaporation (E) and plant transpiration (T) components and is crucial for understanding the land‐atmosphere interactions and ecosystem water budget. However, the mechanism and controls of ET partitioning for subtropical forests in heterogeneous environments remain poorly understood. Here, we present δ18O and δ2H of about 1,527 isotope samples including atmospheric water, soil and plant water during different seasons in 2 years of 2020–2021 from a coniferous forest across Southeast China. We used the isotopic mass balance of ecosystem water pools, the Craig‐Gordon model and the Keeling‐Plot method to partition T from ET (T/ET) and quantify the controls on T/ET. Results indicated that the uncertainty in the T/ET was principally from the soil water evaporation (δE) value, about 20–30 cm was found to be a reasonable evaporating front depth for estimating δE in this coniferous forest. T/ET presented a "U" shape diurnal pattern and varied from 66.7% to 89.9%. Isotope‐based T/ET in autumn with high temperatures and little rain was higher than those in the summer and winter seasons. Relative humidity (or vapour pressure deficit) dominated the diurnal T/ET variations (relative contributions of > 40%) in summer and autumn, while air temperature and soil water content were the main controls in winter. Our study also showed that δ18O‐derived T/ET was consistent with that of δ2H, although δ2H was found to be more stable in ET partitioning, the dual stable isotope approach should be employed in future studies for the uncertainties brought by samplings or measurements. The agreement between the isotope‐based T/ET and ET partitioning approach that uses eddy covariance and sap flux data was stronger at midday. These isotope‐inferred ET partitioning can inform land surface models and provide more insights into water management in subtropical forests. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Protein‐protein interactions (PPIs) play a crucial role in drug discovery and disease treatment. However, the development of effective drugs targeting PPIs remains challenging due to limited methodologies for probing their spatiotemporal anisotropy. Here, we propose a single‐molecule approach using a unique force circuit to investigate PPI dynamics and anisotropy under mechanical forces. Unlike conventional techniques, this approach enables the manipulation and real‐time monitoring of individual proteins at specific amino acids with defined geometry, offering insights into molecular mechanisms at the single‐molecule level. The DNA force circuit was constructed using click chemistry conjugation methods and genetic code expansion techniques, facilitating orthogonal conjugation between proteins and nucleic acids. The SET domain of the MLL1 protein and the tail of histone H3 were used as a model system to demonstrate the application of the DNA force circuit. With the use of atomic force microscopy and magnetic tweezers, optimized assembly procedures were developed. The DNA force circuit provides an exceptional platform for studying the anisotropy of PPIs and holds promise for advancing drug discovery research targeted at PPIs. [ABSTRACT FROM AUTHOR]

Grylloprimevala jilina is a true cave insect living in the dark areas of caves. It has the characteristics of sparse skin pigmentation, degeneration of the compound eyes and monocular eyes, and obvious preference for high‐humidity and low‐temperature environments. Given the highly specialized, rare, and limited distribution, G. jilina is considered an endangered species and also a first‐level national protected insect in China. Cave creatures often undergo dramatic morphological changes in their sensory systems to adapt to the cave environment. Most previous studies mainly focused on morphological adaptive changes in cave insects, and only a few studied the changes at the gene level. In this study, we performed transcriptome analysis of G. jilina and constructed phylogenetic trees of genes that are related to environmental adaptation, including chemosensory, visual‐related, reproduction‐related, temperature adaptation‐related, and winged morph differentiation‐related genes. Besides, the expression levels of environmental adaption‐related genes in different tissues, including antennae, heads, thoraxes, abdomens, legs, and tails, were analyzed. The results showed the loss of chemosensory genes and vision‐related genes, the conservation of reproduction‐related genes and temperature adaptation‐related genes, and the conservation of wing‐related genes despite the loss of wings, and the results were consistent with other cave insects. The identification and expression study of genes possibly related to the environmental adaptability in G. jilina provided basic data for the protection of this endangered species and increased knowledge about insect evolution in general. [ABSTRACT FROM AUTHOR]

Highly accurate soil moisture information is necessary to understand land surface processes. However, observational techniques do not produce adequately accurate spatial‐temporal continuous regional soil moisture data. The data assimilation method can be used to improve the soil moisture estimations by merging multi‐source observed data, but its performance is affected by error covariance and the quality of assimilated data. We designed eight numerical experiments to analyze how to improve the filter performance through soil moisture assimilation using the unscented weighted ensemble Kalman filter (UWEnKF) and 1‐D Richards equation at Maqu and Erlinghu (ELH) observational sites in the source region of Yellow River (SRYR), China. The experimental results show that the filter performance improves as the quality of assimilated data increases in the soil moisture assimilation experiment when assimilating in‐situ surface soil moisture (SSM) observations, SMAP SSM data and downscaled SMAP SSM data. In other aspects, filter performance is readily affected by model and observation error covariances in soil moisture assimilation. If the SMAP SSM data are taken to be perfect (i.e., small bias), UWEnKF performs differently between different sites because of the underestimation or overestimation of SMAP SSM and model simulations compared to the in‐situ observations. Additionally, different soil moisture assimilation results can be obtained with different initial values at the beginning of the assimilation period. Overall, filter performance can be improved primarily by improving the quality of assimilated data (e.g., downscaling the remote sensing data), and by creating a reasonable and effective method for determining error covariance. Key Points: Filter performance can be influenced by the quality of assimilated data and error covarianceFilter performance improved by assimilating high accurate observed dataData accuracy can be improved by a reasonable downscaling method [ABSTRACT FROM AUTHOR]

Although there is mounting concern about how high vapor pressure deficit (VPD) and low soil moisture (SM) affect ecosystem productivity, their relative importance is still under debate. Here, we comprehensively quantified the relative impacts of these two factors on ecosystem gross primary production (GPP) using observations from a global network of eddy‐covariance towers and two approaches (sensitivity analysis and linear regression model). Both approaches agree that a higher percentage of sites experience GPP reduction from high VPD than from low SM over the growing season. However, the constraint of high VPD and low SM on GPP reduction is tightly linked with climates and plant functional types. Humid and mesic ecosystems including forests and grasslands are dominated by VPD, while the semi‐arid and arid ecosystems including shrublands and savannas are dominated by SM. The varying dominant role of these two factors on GPP is closely related to plant stomatal behavior, as predicted by a stomatal conductance model. Additionally, we highlight the non‐linear impact of SM on GPP during droughts and the possible underestimation of the SM effects for deep‐rooted plants when only using surface‐layer SM. Our results shed light on a better understanding of the impacts of VPD and SM on vegetation productivity, with important implications for modeling the response and feedback of ecosystem dynamics to current and future climates. Plain Language Summary: Vapor pressure deficit (VPD) has increased over recent decades and is expected to continue to rise in the future with climate change. Projected changes in precipitation and soil moisture (SM) are more uncertain with higher spatial variability and larger projected intermodel spread. Given the global environmental changes underway, it is of paramount importance to independently assess the effects of high VPD and low SM on ecosystem productivity. Here, we assessed the relative impacts of these two factors on ecosystem gross primary production (GPP) using observations from a global network of eddy‐covariance towers. We find that reductions in GPP are more attributable to high VPD rather than low SM, on average. The constraint of these two factors on GPP reduction is tightly linked with climates and plant functional types. We further emphasize the amplified impact of SM on GPP during droughts and the need to consider using deep SM. Overall, our findings provide a more comprehensive and quantitative attribution of the impact of increasing atmospheric dryness and changes in soil water deficit on ecosystem productivity in a changing climate. Key Points: Reductions in gross primary production (GPP) are more attributable to high vapor pressure deficit (VPD) rather than low soil moisture (SM) across all sitesThe constraint of high VPD and low SM on GPP reduction is tightly linked with climates and plant functional typesOur results highlight that the relative and non‐linear impacts of VPD and SM on GPP should be adequately considered [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Recognition of CpG dinucleotide DNA in epigenetic information flow plays a pivotal role for cellular differentiation and development. The TET3 CXXC domain binds to CpG DNA, serving a basic epigenetic information reading mechanism. During the selective recognition of a CpG motif by a CXXC domain from crowded binding sites in a gene sequence, the protein‐DNA interactions are beyond CpG dinucleotide. However, the selective binding dynamics of CpG within a long DNA context by epigenetic enzymes have been rarely exploited, which is hard for ensemble methods to probe. Here, we used single‐molecule magnetic tweezers to quantitatively examine the dynamics of TET3's CXXC domain on a Hoxa9 promoter DNA. Our single‐molecule binding profile revealed that CXXC‐DNA interactions involve both CpG motifs and their flanking sequences. The residence time of TET3 CXXC differs by about 1000 times in five distinguished CpG clusters in the context of a CpG island. Moreover, we performed multi‐state hidden Markov modeling analysis on the zipping/unzipping dynamics of a CpG hairpin, discovering TET3 CXXC's preference on CpG motifs regarding the –2 to +2 flanking bases. Our results shed light on the selective binding dynamics of a CXXC on a gene sequence, facilitating studies on epigenetic information reading mechanisms. [ABSTRACT FROM AUTHOR]

Assessments of water and energy security over historical and future periods require hydrologic models that can accurately simulate reservoir operations. However, scare reservoir operation data limits the accuracy of current reservoir representations in simulating reservoir behaviors. Furthermore, the reliability of these representations under changing inflow regimes remains unclear, which makes their application for long future planning horizons questionable. To this end, we propose a synergistic framework to predict the release, storage, and hydropower production of ungauged reservoirs (i.e., reservoirs without in‐situ inflow, release, storage, and operating rules) by combining remotely sensed reservoir operating patterns and model‐simulated reservoir inflow with conceptual reservoir operation schemes within a land surface‐hydrologic model. A previously developed reservoir operation scheme is extended with a storage anomaly based calibration approach to accommodate the relatively short time series and large time intervals of remotely sensed data. By setting up controlled experiments in the Yalong River Basin in China, we show that remote sensing can improve the parameter estimation and simulations of ungauged reservoirs for all selected reservoir operation schemes, thereby improving the downstream flood and streamflow simulations. However, most of these schemes show degraded accuracies of reservoir operation simulations under a changing inflow regime, which could lead to unreliable assessments of future water resources and hydropower production. In comparison, our newly extended reservoir operation scheme can be more adaptable to flow regime variations. Our study provides a practical framework for reservoir impact assessments and predictions with the ongoing satellite altimetry projects such as Surface Water and Ocean Topography. Key Points: Satellite remote sensing can improve the representation of ungauged reservoirs and streamflow simulations in hydrologic modelsA reservoir operation scheme for ungauged reservoirs is extended and tailored to the use of remotely sensed reservoir operation dataReservoir operation schemes with storage‐based model structures can be more reliable in reservoir simulations under a changing flow regime [ABSTRACT FROM AUTHOR]

Flow hydrodynamic condition impacts the deposition process on vegetation and removal of colloid and colloid‐associated contaminants in saturated vegetative filter strips (VFSs) under rainfall. A 9.6‐m‐long flume was constructed to investigate the retention of colloids through VFSs, with saturated soil and simulated rainfall. Colloidal filtration theory was applied to calculate the colloid deposition rate coefficient (kd) on vegetation surface. The result showed that removal efficiencies (η) of the single‐stem decreased, but colloid kd on the flume scale vegetation increased with increased Reynolds number (Re). Flume experiment found that the colloid retention rate in VFSs decreased as the Re increased. Since deposition on vegetation surface and diffusion into saturated soil are two main removal mechanisms, the discrepancy between kd and retention rate suggests that colloid diffusion into the soil was the dominant process of colloid removal in saturate VFSs. The research deepens the understanding of colloid transport mechanism in VFSs, and provides theoretical basis for the design of VFSs. [ABSTRACT FROM AUTHOR]

Understanding the role of reservoirs in the terrestrial water cycle is critical to support the sustainable management of water resources especially for China where reservoirs have been extensively built nationwide. However, this has been a scientific challenge due to the limited availability of continuous, long‐term reservoir operation records at large scales, and a process‐based modeling tool to accurately depict reservoirs as part of the terrestrial water cycle is still lacking. Here, we develop a continental‐scale land surface‐hydrologic model over the mainland China by explicitly representing 3,547 reservoirs in the model with a calibration‐free conceptual operation scheme for ungauged reservoirs and a hydrodynamically based two‐way coupled scheme. The model is spatially calibrated and then extensively validated against streamflow observations, reservoir storage observations and GRACE‐based terrestrial water storage anomalies. A 30‐year simulation is then performed to quantify the seasonal dynamics of China's reservoir water storage (RWS) and its role in China's terrestrial water storage (TWS) over recent decades. We estimate that, over a seasonal cycle, China's RWS variation is 15%, 16%, and 25% of TWS variation during 1981–1990, 1991–2000, and 2001–2010, respectively, and one‐fifth of China's reservoir capacity are effectively used annually. In most regions, reservoirs play a growing role in modulating the water cycle over time. Despite that, an estimated 80 million people have faced increasing water resources challenges in the past decades due to the significantly weakened reservoir regulation of the water cycle. Our approaches and findings could help the government better address the water security challenges under environmental changes. Key Points: A continental‐scale land surface‐hydrologic model is developed for China by fully coupling 3,547 reservoirs and relevant water managementA calibration‐free reservoir operation scheme is developed for simulations of ungauged reservoirs in hydrologic modelsThe seasonal variation of reservoir water storage is about 19% of China's terrestrial water storage variation averaged over 1981–2010 [ABSTRACT FROM AUTHOR]

The regional terrestrial water cycle is strongly altered by human activities. Among them, reservoir regulation is a way to spatially and temporally allocate water resources in a basin for multi‐purposes. However, it is still not sufficiently understood how reservoir regulation modifies the regional terrestrial‐ and subsequently, the atmospheric water cycle. To address this question, the representation of reservoir regulation into the terrestrial component of fully coupled regional Earth system models is required. In this study, an existing process‐based reservoir network module is implemented into NOAH‐HMS, that is, the terrestrial component of an atmospheric–hydrologic modelling system, namely, the WRF‐HMS. It allows to quantitatively differentiate role of reservoir regulation and of groundwater feedback in a simulated ground‐soil‐vegetation continuum. Our study focuses on the Poyang Lake basin, where the largest freshwater lake of China and reservoirs of different sizes are located. As compared to streamflow observations, the newly extended NOAH‐HMS slightly improves the streamflow and streamflow duration curves simulation for the Poyang Lake basin for the period 1979–1986. The inclusion of reservoir regulation leads to major changes in the simulated groundwater recharges and evaporation from reservoirs at local scale, but has minor effects on the simulated soil moisture and surface runoff at basin scale. The performed groundwater feedback sensitivity analysis shows that the strength of the groundwater feedback is not altered by the consideration of reservoir regulation. Furthermore, both reservoir regulation and groundwater feedback modify the partitioning of the simulated evapotranspiration, thus affecting the atmospheric water cycle in the Poyang Lake region. This finding motivates future research with our extended fully coupled atmospheric–hydrologic modelling system by the community. [ABSTRACT FROM AUTHOR]

Freshwater lakes are subject to variable degrees of eutrophication. Within lakes, the planktonic bacterial community (PBC) and sediment bacterial community (SBC) are both significant participants in biogeochemical processes of lake ecosystems. However, how the assembly patterns of bacterial communities vary seasonally along a trophic gradient in freshwater lakes is poorly understood.Here, we collected and analysed water and sediment samples from 13 shallow lakes located in an urban region of China during summer and winter, the trophic states of which ranged from mesotrophic to middle eutrophic in summer and oligo‐mesotrophic to light eutrophic in winter. High‐throughput sequencing of 16S ribosomal RNA genes was used to determine the diversity and composition of bacterial communities.Our results indicated that bacterial communities derived from different habitats and seasons did not exhibit a uniform response to lake trophic states. Linear and nonlinear mixed effect models suggested that the α‐diversity of PBC and SBC, respectively, showed a unimodal and monotonically decreasing trend with increasing eutrophication in summer, whereas that of PBC and SBC, respectively, exhibited no obvious trend or an increased pattern along the trophic gradient in winter. In addition, the taxonomic compositional dissimilarity of the PBC was most significantly related to lake trophic differences in summer. Phylogenetic structure analysis revealed that mostly environmental selection regulated the SBC and PBC in both seasons. Moreover, dispersal limitation and homogenising dispersal contributed more to the assembly of SBC and PBC in both seasons, respectively. Water temperature, associated with seasonal variability, was the most important variable driving the PBC assembly, while sediment pH overwhelmed nutrients in regulating the seasonal patterns of SBC assemblages.Overall, we highlighted that the water and sediments, as well as the seasons, differentiated the diversity patterns and assembly processes of bacterial communities along a trophic gradient of freshwater lakes. Our findings provide novel information for understanding the ecological responses of lacustrine bacterial communities to trophic gradients and seasonal variations. This study also contributes an important reference for predicting the changes of microbial community biodiversity under future scenarios of eutrophication. ​ [ABSTRACT FROM AUTHOR]

Large dams and reservoirs alter not only the natural flow regimes of streams and rivers but also their flooding cycles and flood magnitudes. Although the effect of dams and reservoirs has been reported for some vulnerable locations, the understanding of the inner‐basin variation with respect to the effects remains limited. In this study, we analyse the Three Gorges Dam (TGD) built on the Changjiang mainstream (Yangtze River) to investigate the dam effect variations in the system of interconnected water bodies located downstream. We investigated the effect of flow alterations along the downstream river network using discharge time series at different gauging stations. The river–lake interactions (referring to the interactions between the Changjiang mainstream and its tributary lakes i.e. the Dongting and Poyang lakes) and their roles in modifying the TGD effect intensity were also investigated in the large‐scale river–lake system. The results show that the water storage of the tributary lakes decreased after the activation of the TGD. Severe droughts occurred in the lakes, weakening their ability to recharge the Changjiang mainstream. As a consequence, the effect of the TGD on the Changjiang flow increase during the dry season diminished quickly downstream of the dam, whereas its impact on the flow decrease during the wet season gradually exacerbated along the mainstream, especially at sites located downstream of the lake outlets. Therefore, when assessing dam‐induced hydrological changes, special attention should be paid to the changes in the storage of tributary lakes and the associated effects in the mainstream. This is of high importance for managing the water resource trade‐offs between different water bodies in dam‐affected riverine systems. [ABSTRACT FROM AUTHOR]

Wet ecosystems are important in terms of global greenhouse gas emissions, where a high soil water content is one of the most typical features. However, the roles of hydrogeological properties in sediment during the emission process of methane and carbon dioxide remain to be researched, especially in lake ecosystems. In this study, through investigating the layered sediment in Chaohu Lake, we discovered that strong correlations exist between the water content and microbial gas emissions (methane and carbon dioxide). To further examine these correlations, a systematic analysis of the hydrogeological properties in sediment, gas emission features, methane bubble emission theories and microbiomics was conducted. The results revealed that microbial methane emissions can influence sediment structure and the interstitial water content. Differently, the similar distributions in different layers probably lead to the correlations between microbial carbon dioxide emission and the water content. This research also discusses the connections with other hydrogeological parameters (particle features, interstitial space, etc.) during the emission process. In addition, this study addresses the significance of methane emissions for the material exchange between overlying water and sediment. The effect of microbial gas emissions on sediment physical‐chemical properties also provides meaningful information for researching the relationships among environmental factors and microbial ecology. Key Points: The emissions of methane and carbon dioxide correlates with sediment water content in Chaohu lakeActive methane emission can influence the content and movement of sediment interstitial waterConnections of several hydrogeological parameters and the emission of two greenhouse gases have been discussed [ABSTRACT FROM AUTHOR]

Groundwater level fluctuations are affected by surface properties due to complex correlations of groundwater‐surface water interaction and/or other surface processes, which are usually hard to be accurately quantified. Previous studies have assessed the relationship between groundwater level fluctuations and specific controlling factors. However, few studies have been conducted to explore the impact of the combination of multiple factors on the groundwater system. Hence, this paper tries to explore the localized and scale‐specific multivariate relationships between the groundwater level and controlling factors (such as hydrologic and meteorological factors) using bivariate wavelet coherence and multiple wavelet coherence. The groundwater level fluctuations of two wells in areas covered by different plant densities (i.e., the riparian zone of the Colorado River, USA) are analyzed. Main findings include three parts. First, barometric pressure and river stage are the best factors to interpret the groundwater level fluctuations at small scales (<1 day) and large scales (>1 day) at the well of low‐density plants stand, respectively. Second, at the well of high‐density plants stand, the best predictors to control the groundwater level fluctuations include barometric pressure (<1 day), the combination of barometric pressure and temperature (1‐7 days), temperature (7‐30 days), and the combination of barometric pressure, temperature, and river stage (>30 days). The best predictor of groundwater head fluctuations depends on the variance of the vegetation coverage and hydrological processes. Third, these results provide a suite of factors to explain the groundwater level variations, which is an important topic in water‐resource prediction and management. Article impact statement: This method note provides a multivariate method to identify multiple factors that can best explain the groundwater level fluctuation. [ABSTRACT FROM AUTHOR]

Understanding the successional patterns of microbial communities during a phytoplankton bloom is crucial for predicting the compositional and functional stability of lake ecosystems in response to the disturbance of a bloom. Previous studies on bacterial communities associated with blooms have rarely studied the dynamics of these communities. The successional patterns of bacterial communities within different micro‐habitats (i.e. water column versus particles) and mechanisms that shape these communities that differ in composition and structure remain unclear.We selected a eutrophic urban lake to investigate the succession of bacterial communities during a bloom. We divided the bacterial communities into free‐living (FL) and particle‐attached (PA) groups based on their different lifestyles. The amplicon‐based 16S rRNA gene high‐throughput sequencing technology was used to obtain bacterial community composition and phylogenetic structure.Our study showed distinct successional patterns between FL and PA bacterial communities, and the two bacterial lifestyles showed different responses and resilience to the bloom, in terms of diversity and relative abundance of bacterial taxa. Alpha‐diversity of the PA bacterial community decreased during the bloom, whereas that of the FL bacterial community increased. More taxa in the FL bacterial community showed resilience after the disturbance than in the PA bacterial community.The influence of phytoplankton blooms on the assembly of the bacterial community can be viewed as niche selection that led to the decrease in the relative importance of stochastic processes in shaping both FL and PA bacterial communities. This study shows the ecological significance of the bacterial community response to bloom events in lakes. It also shows that assembly processes differ for bacterial communities that have different lifestyles in lake ecosystems disturbed by phytoplankton blooms. [ABSTRACT FROM AUTHOR]

Progressive intensification and proliferation of heat waves impose extensively impacts on entire environment and ecology. The far‐reaching implications of heat waves and the severe future projections emphasize the imperative need to explore the driving factors and their quantitative contribution to heat wave variations. In this study, a multiaspect characteristic of heat waves across China during 1961–2017 is evaluated using excess heat factor. Results showed that the number of events, frequency, duration, and intensity has heterogeneous spatial patterns, with a consistent abrupt transition in 1996–1997. The robust positive correlations between heat wave characteristics and warming sea surface temperature (SST) indicate the association of heat wave with SST anomalies. Except the number of events, the other factors (including the frequency, duration, and intensity) of heat waves are strongly influenced by El Niño‐Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). However, the influences have significant variations from region to region, with the central regions experiencing significant decreases in the frequency, duration, and intensity of heat waves during the simultaneous ENSO phases (El Niño‐La Niña), in comparison with northern and western regions dominated by IOD (positive‐negative) experiencing longer and more frequent heat waves. Particularly, the mild heat waves are more vulnerable to the warming SST modes than severe heat waves. The decrease of heat waves is affected by the convergent winds bringing cold air from the high latitude, while the extensively significant increase of heat waves is controlled by the anomalously sinking motions. Key Points: IOD has more impacts on heat wave characteristics than ENSOMild heat waves are more vulnerable to SST modes than severe heat wavesConvergent winds and anomalous sinking motions affect regional heat wave variations [ABSTRACT FROM AUTHOR]

Despite the vast extent of desert soils on the earth's surface, our understanding of the moisture dynamics of near‐surface desert soils (i.e., the top centimeters to few meters of the soil profile) remain limited. The goal of this study was to explore the use of the Peters–Durner–Iden (or PDI) instead of bimodal van Genuchten (or BVG) hydraulic functions to improve water redistribution simulations using HYDRUS‐1D for drier soils in desert environments. The PDI hydraulic functions take capillary and film flow into account, whereas BVG hydraulic functions are limited to capillary flow. By comparing measured with simulated water content data, we found that moisture redistribution simulations were improved by using PDI instead of BVG soil water retention and hydraulic conductivity functions. Compared with the BVG simulations, the PDI simulations particularly improved for drier soil conditions (i.e., volumetric water contents ranging from 6 to 10%; suction heads between pF 2 and pF 3.8, and saturation degrees between 19 and 32%, respectively) for the studied sandy soil of Scaling Environmental Processes in Heterogeneous Arid Soils (SEPHAS) Lysimeter 1. For pF >3, the PDI functions predicted higher hydraulic conductivity than the BVG functions, which confirmed the hypothesis that a hydraulic conductivity function, which can capture film flow, may improve moisture distribution simulations for dry soils. For pF between 2 and 3, however, simulation results improved due to the difference in the water retention rather than the hydraulic conductivity function. [ABSTRACT FROM AUTHOR]

Rhizosphere microbiota has received much attention due to their associations with plant growth and their fundamental importance in terrestrial ecosystems. However, relatively few studies have focused on rhizosphere microbial communities associated with aquatic macrophytes in freshwater lakes. We hypothesized that the rhizosphere microbiome would reflect the presence of macrophyte roots and the concomitant microhabitat conditions the roots create. Here, high‐throughput sequencing and network analysis were employed to compare the composition and structure of bacterial communities in the rhizosphere of two common emergent macrophytes, Zizania latifolia and Phragmites australis, with the surrounding sediments in Lake Taihu (China). Results indicated that bacterial diversity, community composition, and co‐occurrence networks differed between the communities of bulk sediments and the communities of rhizosphere and surface sediments. Richness and phylogenetic diversity were higher and more taxa were enriched in the rhizosphere and surface sediment communities compared with bulk sediment communities. No differences were detected between bacterial communities in rhizosphere and surface sediments, nor between rhizospheres sediment communities of the two macrophyte species. Anaerobic taxa were more abundant in bulk sediment communities. Among the co‐occurrence networks, more nodes (operational taxonomic units) and edges (connections) with higher average degree as well as more topologically important nodes were found in rhizosphere and surface sediment communities relative to bulk communities. These findings suggest that rhizosphere microbiome communities are influenced by the presence of macrophyte roots, with oxygenated rhizosphere and surface sediment communities being more diverse, and organized into more interconnected co‐occurrence networks. [ABSTRACT FROM AUTHOR]

Temporal variation of runoff chemistry and its seasonal controls relating to chemical weathering processes and drainage system evolution were examined at Urumqi Glacier No.1 in Xinjiang, China, over a full melt season. The dominant ions in meltwater runoff are HCO3−, Ca2+, and SO42−; and Fe, Sr, and Al are dominant elements. Concentrations of major ions and some elements show periodic variations with seasons and negatively correlate with discharge, whereas other elements (e.g., Al, Ni, Cu, Zn, Cd, and Pb) show a random change, providing insights into the hydrological and physicochemical controls. HCO3− and Ca2+ are primarily derived from calcite, SO42− and Fe mainly come from pyrite, and Sr and Al principally originate from silicate. Hydrochemical fluxes of solutes exhibit strong seasonality but are positively related to discharge, suggesting an increasing release of solutes during higher flow conditions. Solute yields, cation denudation rate, and chemical weathering intensity observed at Urumqi Glacier No.1 are higher than those at most basins worldwide. This suggests that chemical weathering in central Asia may be stronger than at other glacial basins with similar specific discharge. Concentrations of some elements (e.g., Fe, Al, As, Pb, and Zn) are close to or exceed the guidelines for drinking water standards in meltwater‐fed rivers. These rivers may face future challenges of water quality degradation, and relationships between changing flow and water quality conditions should be established soon, given that development of channelized flow is expected to be earlier over a melt season in a warming climate. [ABSTRACT FROM AUTHOR]

Ice sheets have been shown to deliver large amounts of labile iron (Fe) to aquatic ecosystems; however, the role of glaciers distinct from ice sheets in supplying labile Fe to downstream ecosystems is less well understood despite their rapid volume loss globally. Direct and continuous measurements of Fe from glaciers throughout an entire melt season are very limited to date. Here we present extensive seasonal data on 0.45‐μm‐filtered Fe (dFe) from three glaciers in Asia. Concentrations of dFe are negatively correlated with glacier discharge, and dFe yields are closely related to specific discharge. Based on our study and previously published dFe data, we estimate the release of dFe from Asian glaciers to be 23.8±14.1 Gg/a. We further compile a global data set of dFe from more than 12 glaciers, which, when combined with data on glacier discharge, suggest that the release of dFe from glaciers globally is on the order of 185±172 Gg/a. This finding suggests that glaciers may provide a substantial, but largely unrecognized source of potentially labile Fe, and may become increasingly important for the Fe biogeochemical cycle in a warming climate. Key Points: This study presents data of dFe from three glaciers in Asia over a full melt season and compiles a global dataset of dFe from over 12 glaciersRelease of dFe from Asian glaciers is 23.7 Gg/a, and from global glaciers is 185 Gg/a, which is 4–10 times higher than from ice sheetsGlaciers may provide a substantial but largely unrecognized source of potentially labile Fe and become increasingly important for global Fe cycle [ABSTRACT FROM AUTHOR]

A few relatively large reservoirs, hundreds of small reservoirs, and numerous farm dams were built in the upper Gan River Basin, China. The operation of such a reservoir network can serve as a significant source of variability in the local hydrological regime and should be included in research to better understand the interaction between multiple hydrological processes and watershed management. In this study, a reservoir network module that included reservoirs of multiple sizes was developed and fully integrated into the coupled land surface and distributed hydrologic model system (CLHMS), for a detailed description of the hydrological impact of a reservoir network. A generalized release scheme was employed to determine the outflow of both large and small reservoirs. The integrated model was then evaluated against observations and reanalysis data, which indicate that the model can reasonably reconstruct the reservoir operation, streamflow, and other hydrological variables. Results quantitatively demonstrate that a reservoir network can result in an increased streamflow in dry seasons, a decreased streamflow in wet seasons, a generally larger groundwater discharge, higher groundwater level, a slightly damper soil condition, and a larger amount of evapotranspiration at the basin level. With the integrated model, it is feasible to achieve more sustainable watershed planning and management. [ABSTRACT FROM AUTHOR]

Ice sheets and glaciers have been shown to deliver large amounts of labile dissolved organic carbon (DOC) to downstream aquatic ecosystems, but recent studies may underestimate the release of DOC from mountain glaciers. To date, continuous measurements of DOC from mountain glaciers throughout entire glacier melt season are very limited. Here we present high‐density data on DOC from two Asian mountain glaciers over a full melt season in 2013 and compile a global data set of DOC from 42 mountain glaciers. Based on our study and previously published DOC data, we estimate the storage and release of DOC associated with Asian mountain glaciers to be 8.8 to 13.8 Tg C and 0.19 Tg C/a, respectively. Rough extrapolation of glacier runoff to a global scale suggests that DOC release from mountain glaciers is on the order of 0.8 Tg C/a, which is 1.4 times higher than the most current estimates. The current release of DOC from mountain glaciers is therefore far more significant than previously thought and should be considered in future evaluation of the global carbon cycle. Key Points: Data on DOC from two Asian glaciers have been collected, and a global data set of DOC from worldwide mountain glaciers have been compiledStorage of DOC in Asian glaciers is 8.8 to 13.8 Tg C, and release of DOC from mountain glaciers worldwide is on the order of 0.8 Tg C/aCurrent release of DOC from mountain glaciers is far more significant than previously thought and should be considered in future evaluation of the global carbon cycle [ABSTRACT FROM AUTHOR]

Understanding climate change impacts on hydrological regime and assessing future water supplies are essential to effective water resources management and planning, which is particularly true for the Tibetan Plateau (TP), one of the most vulnerable areas to climate change. In this study, future climate change in the TP was projected for 2041–2060 by a high‐resolution regional climate model, RegCM4, under 3 representative concentration pathways (RCPs): 2.6, 4.5, and 8.5. Response of all key hydrological elements, that is, evapotranspiration, surface run‐off, baseflow, and snowmelt, to future climate in 2 typical catchments, the source regions of Yellow and Yangtze rivers, was further investigated by the variable infiltration capacity microscale hydrological model incorporated with a 2‐layer energy balance snow model and a frozen soil/permafrost algorithm at a 0.25° ×0.25° spatial scale. The results reveal that (a) spatial patterns of precipitation and temperature from RegCM4 agree fairly well with the data from China Meteorological Forcing Dataset, indicating that RegCM4 well reproduces historical climatic information and thus is reliable to support future projection; (b) precipitation increase by 0–70% and temperature rise by 1–4 °C would occur in the TP under 3 RCPs. A clear south‐eastern–north‐western spatial increasing gradient in precipitation would be seen. Besides, under RCP8.5, the peak increase in temperature would approach to 4 °C in spring and autumn in the east of the TP; (c) evapotranspiration would increase by 10–60% in 2 source regions due to the temperature rise, surface run‐off and baseflow in higher elevation region would experience larger increase dominantly due to the precipitation increase, and streamflow would display general increases by more than 3% and 5% in the source regions of Yellow and Yangtze rivers, respectively; (d) snowmelt contributes 11.1% and 16.2% to total run‐off in the source regions of Yellow and Yangtze rivers, respectively, during the baseline period. In the source region of Yangtze River, snowmelt run‐off would become more important with increase of 17.5% and 18.3%, respectively, under RCP2.6 and RCP4.5 but decrease of 15.0% under RCP8.5. [ABSTRACT FROM AUTHOR]

ABSTRACT The soil moisture-precipitation (SM-P) feedback process can affect the water and energy cycles at local to regional scale, subsequently affecting the water distribution in space and time. This study investigates SM-P feedback at different time scales over Asia during boreal summer season based on the covariation between SM and P. In this article the positive (negative) feedback means positive (negative) statistical correlations between SM-P. This is based on the statistical relationship and do not reflect physical process associated between SM and P. The Global Land Data Assimilation System (GLDAS) data, Climate Forecast System Reanalysis (CFSR) data and regional climate model, version 4 (RegCM4) simulations are adopted for analysis in this study. The results indicate a negative SM-P relationship at a seasonal time scale over mid-high latitudes of the study area whereas a positive but weak and spatial scattered correlation pattern is observed at the interannual time scale. A positive relationship is diagnosed over India, Indochina, and southeast China regions at seasonal (though weak) and interannual time scales. The positive and/or negative SM-P correlation patterns observed at different time scales depends on the memory associated with seasonal precipitation and soil moisture. The strength of the SM-P relationship seems to be influenced by the threshold behaviour of soil moisture, especially at the interannual time scale. This indicates that beyond a certain threshold in soil moisture anomalies likely to have significant influence on precipitation. [ABSTRACT FROM AUTHOR]

Ammonia oxidation is a crucial process in global nitrogen cycling, which is catalyzed by the ammonia oxidizers. Emergent plants play important roles in the freshwater ecosystem. Therefore, it is meaningful to investigate the effects of emergent macrophytes on the abundance and community composition of ammonia oxidizers. In the present study, two commonly found emergent macrophytes ( Zizania caduciflora and Phragmitas communis) were obtained from freshwater lakes and the abundance and community composition of the ammonia-oxidizing prokaryotes in the rhizosphere sediments of these emergent macrophytes were investigated. The abundance of the bacterial amoA gene was higher in the rhizosphere sediments of the emergent macrophytes than those of bulk sediments. Significant positive correlation was found between the potential nitrification rates (PNRs) and the abundance of bacterial amoA gene, suggesting that ammonia-oxidizing bacteria (AOB) might play an important role in the nitrification process of the rhizosphere sediments of emergent macrophytes. The Nitrosotalea cluster is the dominant ammonia-oxidizing archaea (AOA) group in all the sediment samples. Analysis of AOB group showed that the N. europaeal cluster dominated the rhizosphere sediments of Z. caduciflora and the bulk sediments, whereas the Nitrosospira cluster was the dominant AOB group in the rhizosphere sediments of P. communis. [ABSTRACT FROM AUTHOR]

The characteristics of karst aquifers are difficult to be determined due to their heterogeneous physical properties and lack of hydrogeological information. In this case study, we applied two methods for a comparative analysis of storage and drainage characteristics in upstream, midstream, and downstream of Houzhai cave stream basin. In the first method, Minimum Smoothed Method ( MSM) is used to determine the proportion of baseflow to the total flow (Baseflow Index, BFI). In the second method, a bicarbonate-base two-end member mixing model is used to quantify the slow flow component and fast flow component. For both methods, slow flow and quick flow are quantified at three sampling sites, which provide useful information for the analysis of storage and drainage characteristics. The results from flow separation method and hydrogeochemical analysis show a consistently increasing trend of the proportion of slow flow to total flow from the upstream to downstream which indicates that the voids of highly conductive conduits and well-connected fissures decrease along the flow paths in the Houzhai cave stream basin in southwest China. The upstream areas have a low proportion of baseflow which indicates a high drainage capacity due to high permeable conduits and well-connected fissures. The downstream areas, on the contrary, have a high proportion of baseflow which indicates a high storage capacity and slow infiltration due to the predominant presence of matrix and poorly-connected fissures. These numerical methods provide alternative ways to investigate the storage and drainage characteristics of karst aquifers where direct measurement are not available. [ABSTRACT FROM AUTHOR]

ABSTRACT Temporal and spatial variations in reference evapotranspiration (ET0) from 1980 to 2012 were investigated for 33 meteorological stations in the three-river source region ( TRSR). Penman-Monteith reference evapotranspiration in the TRSR significantly decreased at a rate of 0.91 mm a−2 from 1980 to 2012, and the decrease was actually an offset of the positive effect of increasing air temperature on ET0 and the negative effect of decreasing net radiation, wind speed, and actual vapor pressure. A differential equation method based on the Penman-Monteith formula was used to attribute the change in ET0. As for the decrease of reference evapotranspiration from 1980 to 2012, the contributions of net radiation, wind speed, actual vapor pressure, and air temperature were −0.57, −0.49, −0.26, +0.41 mm a−2, respectively. Thus, 'net radiation decrease' was the major reason for the decrease in ET0 for the TRSR. In addition, it appears that the change in ET0 was more sensitive to meteorological variables in high-elevation regions than in low-elevation regions. [ABSTRACT FROM AUTHOR]

There can be marked variations in soil hydraulic properties in a soil vertical profile from the soil surface to the base of the root zone. Many existing two-layer soil moisture ( TLSM) models cannot well describe typical stratified soil profiles. A modified TLSM model is presented in this study. The modified model results and those from two existing models are compared with field observations. The modified TLSM model had the best agreement with the field observations. In both the surface layer and the root zone layer, the root mean square errors of soil moisture estimated by the modified model were smaller than those for the other models. The parameters in the modified TLSM model are relatively easy to determine. The modified TLSM model offers clear advantages over current TLSM models. [ABSTRACT FROM AUTHOR]

A closed description of the regional water balance requires hydro-meteorological modeling systems which represent the atmosphere, land surface, and subsurface. We developed such a mesoscale modeling system, extending the atmospheric model WRF with the distributed hydrological model HMS in a fully coupled way. It includes explicit lateral groundwater and land surface flow parameterization schemes and two-way groundwater-unsaturated zone interaction by replacing the free drainage bottom boundary of WRF's Noah-LSM with a Fixed-head or Darcy-flux boundary condition. The system is exemplarily applied for the Poyang Lake basin (160,000 km2) and the period 1979-1986 using a two-nest approach covering East Asia (30 km) and the Poyang Lake basin (10 km) driven by ERA Interim. Stand-alone WRF effectively simulates temperature (bias 0.5°C) and precipitation (bias 21-26%). Stand-alone HMS simulations provide reasonable streamflow estimates. A significant impact on the regional water balance was found if groundwater-unsaturated zone interaction is considered. But the differences between the two groundwater coupling approaches are minor. For the fully coupled model system, streamflow results strongly depend on the simulation quality for precipitation. Two-way interaction results in net upward water fluxes in up to 25% of the basin area after the rainy season. In total, two-way interaction increases basin averaged recharge amounts. The evaluation with CPC and GLEAM indicates a better performance of the fully coupled simulation. The impact of groundwater coupling on LSM and atmospheric variables differs. Largest differences occur for the variable recharge (26%), whereas for atmospheric variables, the basin-averaged impact is minor (<1%). But locally, a spatial redistribution up to ±5% occurs for precipitation. [ABSTRACT FROM AUTHOR]

Located in the northeast of the Tibetan Plateau, the headwaters of the Yellow River basin (HYRB) are very vulnerable to climate change. In this study, we used the Soil and Water Assessment Tool (SWAT) model to assess the impact of future climate change on this region's hydrological components for the near future period of 2013-2042 under three emission scenarios A1B, A2 and B1. The uncertainty in this evaluation was considered by employing Bayesian model averaging approach on global climate model (GCM) multimodel ensemble projections. First, we evaluated the capability of the SWAT model for streamflow simulation in this basin. Second, the GCMs' monthly ensemble projections were downscaled to daily climate data using the bias-correction and spatial-disaggregation method and then were utilized as input into the SWAT model. The results indicate the following: (1) The SWAT model exhibits a good performance for both calibration and validation periods after adjusting parameters in snowmelt module and establishing elevation bands in sub-basins. (2) The projected precipitation suggests a general increase under all three scenarios, with a larger extent in both A1B and B1 and a slight variation for A2. With regard to temperature, all scenarios show pronounced warming trends, of which A2 displays the largest amplitude. (3) In the terms of total runoff from the whole basin, there is an increasing trend in the future streamflow at Tangnaihai gauge under A1B and B1, while the A2 scenario is characterized by a declining trend. Spatially, A1B and B1 scenarios demonstrate increasing trends across most of the region. Groundwater and surface runoffs indicate similar trends with total runoff, whereas all three scenarios exhibit an increase in actual evapotranspiration. Generally, both A1B and B1 scenarios suggest a warmer and wetter tendency over the HYRB in the forthcoming decades, while the case for A2 indicates a warmer and drier trend. Findings from this study can provide beneficial reference to water resource and eco-environment management strategies for governmental policymakers. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Most glaciers in the Tibetan Plateau ( TP) are not closely monitored for mass balance (MB) due to their inaccessibility, which makes it difficult to better understand the dynamics of glacial advancement or retreat. Surface energy budget, MB, and the resulting melt runoff were calculated for Zhadang glacier (5,710 m above sea level) of the central TP. Energy balance was calculated on 30-m square grids for the summers of 2007 and 2008. On average, net radiation dominated the total energy source (66%) while the residual was supplied by sensible heat flux. More than 67% of the energy sink was available for melting on the glacier. Thus, less than 33% of the total energy was consumed by latent heat flux. A large and a slightly negative summer MB were calculated for the 2007 and 2008 summers, respectively. The high sensitivity of the glacier to air temperature may indicate that the lower than average seasonal temperature was more important than the increased precipitation for the slightly negative MB in the summer of 2008. Comparisons of glacial melt runoff indicated that rainfall and snowmelt were the dominant contribution to total runoff in the glacierized basin and the ice melting is also very important. Glacial melt calculation provides a basis for quantifying glacial melt-runoff contribution to the river streamflow in the TP. [ABSTRACT FROM AUTHOR]

ABSTRACT Given the availability of a new generation of general circulation model simulations from the Coupled Model Intercomparison Project Phase 5 ( CMIP5) archive, we attempt to evaluate the model output by using three variants of the transformed Mielke measure to assess (1) the performance of the models in simulating historical surface temperature and precipitation, (2) the climate change response of the models to future greenhouse gases ( GHGs) scenarios, and (3) the consistency of the projected change of each model with that of the multi-model ensemble ( MME) mean. Most models exhibited varying degrees of skills, depending on the region and season, whereas a few models were identified as performing well globally, including the CMCC models, IPSL-CM5A-MR, and BCC-CSM1.1M. Models with the highest and lowest climate sensitivities, as well as those that project future climate changes most resembling the MME mean, were identified. The future precipitation and temperature changes projected by the MPI models and NCAR-CESM1 models were found to best resemble the overall MME. Finer resolution was found to improve model performance in simulating historical climate in most regions and seasons, particularly for temperature; however, it does not have a significant effect on the response of model climates to future GHGs scenarios. We found that no model can simultaneously exhibits good performance in simulating historical climate and in projecting a future climate that is close to the MME mean. Determining the 'best' overall model is difficult because 'best' is dependent on the specific applications for which a model will be used. Evaluating climate models is an important step to build confidence in their application for impact assessment. Our study provides a basis for concerned groups choosing climate models for their subsequent studies. [ABSTRACT FROM AUTHOR]

The Tarim River Basin is a special endorheic arid drainage basin in Central Asia, characterized by limited rainfall and high evaporation as common in deserts, while water is supplied mainly by glacier and snow melt from the surrounding mountains. The existing drought indices can hardly capture the drought features in this region as droughts are caused by two dominant factors (meteorological and hydrological conditions). To overcome the problem, a new hybrid drought index (HDI), integrating the meteorological and hydrological drought regimes, was developed and tested in the basin in the work. The index succeeded in revealing the drought characteristics and the ensemble influence better than the single standardized precipitation index or the hydrological index. The Artificial Neural Network approach based on temperature and precipitation observations was set up to simulate the HDI change. The method enabled constructing scenarios of future droughts in the region using climate simulation of the GCMs under four RCP scenarios from the latest CMIP5 project. The simulations in the study have shown that the water budget patterns in the Tarim River Basin are more sensitive to temperature than to precipitation. Dominated by temperature rise causing an accelerating snow/glacier melt, the frequency of drought months is projected to decrease by about 14% in the next decades (until 2035). The drought duration is expected to be shortened to 3 months on average, with the severity alleviated. However, the region would still suffer more severe droughts with a high intensity in some years. The general decrease in drought frequency and intensity over the region in the future would be beneficial for water resources management and agriculture development in the oases. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Environmental estrogens are widely spread across the world and are increasingly thought of as serious contaminators. The present study looks at the influence of different concentrations of 17β-estradiol on greenhouse gas emissions (CO2, CH4, and N2O) in simulated systems to explore the relationship between environmental estrogen-pollution and greenhouse gas emissions in natural water bodies. The present study finds that 17β-estradiol pollution in simulated systems has significant promoting effects on the emissions of CH4 and CO2, although no significant effects on N2O emissions. The present study indicates that 17β-estradiol has different effects on the different elements cycles; the mechanism of microbial ecology is under review. Environ Toxicol Chem 2015;34:977-982. © 2015 SETAC [ABSTRACT FROM AUTHOR]

Soil temperature plays an important role in hydrology, agriculture, and meteorology. In order to improve the accuracy of soil temperature simulation, a soil temperature data assimilation system was developed based on the Ensemble Particle Filter (EnPF) and the Common Land Model (CLM), and then applied in the Walnut Gulch Experimental Watershed (WGEW) in Arizona, United States. Surface soil temperature in situ observations and Moderate Resolution Imaging Spectroradiometer Land Surface Temperature (MODIS LST) data were assimilated into the system. In this study, four different assimilation experiments were conducted: (1) assimilating in situ observations of instantaneous surface soil temperature each hour, (2) assimilating in situ observations of instantaneous surface soil temperature once per day, (3) assimilating verified MODIS LST once per day, and (4) assimilating original MODIS LST once per day. These four experiments reflect a transition from high-quality and more frequent in situ observations to lower quality and less frequent remote sensing data in the data assimilation system. The results from these four experiments show that the assimilated results are better than the simulated results without assimilation at all layers except the bottom layer, while the superiority gradually diminishes as the quality and frequency of the observations decrease. This demonstrates that remote sensing data can be assimilated using the ensemble particle filter in poorly gauged catchments to obtain highly accurate soil variables (e.g., soil moisture, soil temperature). Meanwhile, the results also demonstrate that the ensemble particle filter is effective in assimilating soil temperature observations to improve simulations, but the performance of the data assimilation method is affected by the frequency of assimilation and the quality of the input data. [ABSTRACT FROM AUTHOR]

ABSTRACT Flowing water bodies often have plants that differ greatly in size and type, which interfere with fluid flow structure. Although there are studies describing vegetation-flow interactions in ideal laboratory conditions, their practical application is sometimes still difficult. This paper presents results of research involving laboratory simulations channel flow and the effects upon its structure as it passes through a combined layer of submerged and emerged vegetation in an open-channel flume. Instantaneous time-average velocity and turbulence at various locations were measured with a 3D acoustic Doppler velocimeter. The experimental results showed that the mean velocity profiles can be divided into three layers: bottom, middle and upper. The velocity profiles show the flow structure was complex variable over time creating mixing velocity layers associated with inflection points and velocity spikes. Turbulence intensity urms, vrms, wrms was nearly invariant for the flow depth at the bottom layer in most locations within the vegetation area. Maximum turbulence intensity occurred within the middle layer and migrated vertically as frontal width of the plant increased. Maximum turbulence intensity fluctuated at the velocity mixing layer where there is significant momentum exchange. The Manning's vegetation roughness coefficient n(v) due to vegetation resistance increased with vegetation density as expected. In all, the results show flow structure varies substantially at the stem section and at the canopy top of submerged vegetation. These analytical findings will be useful in understanding river channel hydraulic transport and mixing processes and useful in river engineering applications and modelling. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, an unconventional method called Modified Weighted Function (MWF) is presented for the conventional moment estimation of a probability distribution function. The aim of MWF is to estimate the coefficient of variation (CV) and coefficient of skewness (CS) from the original higher moment computations to the first-order moment calculations. The estimators for CV and CS of Pearson type three distribution function (PE3) were derived by weighting the moments of the distribution with two weight functions, which were constructed by combining two negative exponential-type functions. The selection of these weight functions was based on two considerations: (1) to relate weight functions to sample size in order to reflect the relationship between the quantity of sample information and the role of weight function and (2) to allocate more weights to data close to medium-tail positions in a sample series ranked in an ascending order. A Monte-Carlo experiment was conducted to simulate a large number of samples upon which statistical properties of MWF were investigated. For the PE3 parent distribution, results of MWF were compared to those of the original Weighted Function (WF) and Linear Moments (L-M). The results indicate that MWF was superior to WF and slightly better than L-M, in terms of statistical unbiasness and effectiveness. In addition, the robustness of MWF, WF, and L-M were compared by designing the Monte-Carlo experiment that samples are obtained from Log-Pearson type three distribution (LPE3), three parameter Log-Normal distribution (LN3), and Generalized Extreme Value distribution (GEV), respectively, but all used as samples from the PE3 distribution. The results show that in terms of statistical unbiasness, no one method possesses the absolutely overwhelming advantage among MWF, WF, and L-M, while in terms of statistical effectiveness, the MWF is superior to WF and L-M. [ABSTRACT FROM AUTHOR]

Medium heterogeneity affects reaction kinetics by controlling the mixing of reactant particles, but the linkage between medium properties and reaction kinetics is difficult to build, even for simple, relatively homogeneous media. This study aims to explore the dynamics of bimolecular reactions, aniline + 1,2-naphthoquinone-4-sulfonic acid → 1,2-naphthoquinone-4-aminobenzene, in relatively homogeneous flow cells. Laboratory experiments were conducted to monitor the transport of both conservative and reactive tracers through columns packed with silica sand of specific diameters. The measured tracer breakthrough curves exhibit subdiffusive behavior with a late-time tail becoming more pronounced with decreasing sand size, probably due to the segregated flow regions formed more easily in columns packed with smaller size sand. Numerical analysis using a novel Lagrangian model shows that subdiffusion has a twofold effect on bimolecular reactions. While subdiffusion enhances the power-law growth rate of product mass by prolonging the exposure of reactant particles in the depletion zone, the global reaction rate is constrained because subdiffusion constrains the mobility of reactant particles. Reactive kinetics in deceptively simple homogeneous media is therefore controlled by subdiffusion, which is sensitive to the dimensions of packed sand. [ABSTRACT FROM AUTHOR]

The transport of bromide (Br) under matric heads of 0, −2, −5, and −10 cm using undisturbed soil columns was investigated for understanding the solute transport in arid soils. Undisturbed soil cores were collected at ground surface, directly below where tension infiltrometer measurements were made in the Amargosa Desert, Nevada, United States. Laboratory experiments were conducted by introducing water containing Br tracer into a soil column maintained at steady-state conditions. The observed data of breakthrough curves ( BTC) were well fitted to an one-region model, except for the cores at saturation, and a core at the matric head of −5 cm, from which the observed data were better fitted to a two-region model. Fitted pore water velocities with the one-region model ranged from 1.2 to 56.6 cm/h, and fitted dispersion coefficients ( D) ranged from 2.2 to 100 cm2/h. Results for the core analyzed with the two-region model indicated that D ranged from 27.6 to 70.9 cm2/h at saturation, and 25.7 cm2/h at the matric head of −5 cm; fraction of mobile water ( β) ranged from 0.18 to 0.65, and mass transfer coefficient ( ω) ranged from 0.006 to 0.03. In summary, the water fluxes and Br dispersion coefficients at investigated matric heads were very high due to the coarseness of the soils and possibly due to preferential flow pathways. These high water fluxes and Br dispersion coefficients would lead to a higher risk of deeper leaching accumulating nitrate nitrogen to the groundwater, and have significant effects on the desert ecosystem. [ABSTRACT FROM AUTHOR]

The statistical characteristics of precipitation on the daily resolution play an important role not only in the risk assessment of floods and droughts but also in the land use management. In this study, spatial and temporal patterns of the precipitation concentration in the Yangtze River Basin are investigated by using three indices, i.e. precipitation concentration index (CI), precipitation concentration degree (PCD) and precipitation concentration period (PCP). Based on meteorological data of 147 stations for the period of 1960-2008, non-parametric trend analysis and wavelet transformation analysis are employed to detect the temporal variation of these indices. Spatial variability of precipitation concentration indices and their trends are analysed and demonstrated with the help of GIS tools. The results indicate the following: (i) The high precipitation CI values mainly distribute in the middle region of the Yangtze River Basin, whereas the lower and lowest CI values are found in the lower and upper regions, respectively. A roughly east-west gradient for PCD value and PCP value varies from 0.26 to 0.77 and from 123 to 197, respectively. (ii) The analysis results of precipitation CI trends for different periods (i.e. recent 40, 30 and 20 years) show that the middle region of the Yangtze River Basin experienced a transition from decreasing precipitation CI to increasing precipitation CI during the last two decades, although the decreasing long-term trends in the precipitation CI are not significant in most areas during the period of 1960-2008. (iii) The upper basin, middle basin and lower basin are, respectively, dominated by the significant decreasing, increasing and no significant trends in PCD. A dominance of insignificant PCP trends is observed in the entire basin during 1960-2008 despite that a few areas in the upper region are characterized by significant decreasing trends. (iv) Interdecadal oscillations can be found for three precipitation indices, but with no constant periodicity. Furthermore, good positive correlations have been detected between precipitation CI and PCD, whereas insignificant correlation coefficients of PCP with precipitation are common in the basin. The results can provide beneficial reference to water resource and eco-environment and mitigation to flood or drought hazards in the Yangtze River Basin for policymakers and stakeholders. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Particle-based models and continuum models have been developed to quantify mixing-limited bimolecular reactions for decades. Effective model parameters control reaction kinetics, but the relationship between the particle-based model parameter (such as the interaction radius R) and the continuum model parameter (i.e., the effective rate coefficient Kf) remains obscure. This study attempts to evaluate and link R and Kf for the second-order bimolecular reaction in both the bulk and the sharp-concentration-gradient (SCG) systems. First, in the bulk system, the agent-based method reveals that R remains constant for irreversible reactions and decreases nonlinearly in time for a reversible reaction, while mathematical analysis shows that Kf transitions from an exponential to a power-law function. Qualitative link between R and Kf can then be built for the irreversible reaction with equal initial reactant concentrations. Second, in the SCG system with a reaction interface, numerical experiments show that when R and Kf decline as t−1/2 (for example, to account for the reactant front expansion), the two models capture the transient power-law growth of product mass, and their effective parameters have the same functional form. Finally, revisiting of laboratory experiments further shows that the best fit factor in R and Kf is on the same order, and both models can efficiently describe chemical kinetics observed in the SCG system. Effective model parameters used to describe reaction kinetics therefore may be linked directly, where the exact linkage may depend on the chemical and physical properties of the system. [ABSTRACT FROM AUTHOR]

With the firm demonstration of the in vivo presence and biological functions of many non- B DNA structures, it is of great significance to understand their physiological roles from the perspective of structural conformation, stability, and transition kinetics. Although relatively simple in primary sequences compared to proteins, non- B DNA species show rather versatile conformations and dynamic transitions. As the most-studied non- B DNA species, the G-quadruplex displays a myriad of conformations that can interconvert between each other in different solutions. These features impose challenges for ensemble-average techniques, such as X-ray crystallography, NMR spectroscopy, and circular dichroism ( CD), but leave room for single-molecular approaches to illustrate the structure, stability, and transition kinetics of individual non- B DNA species in a solution mixture. Deconvolution of the mixture can be further facilitated by statistical data treatment, such as iPoDNano ( integrated population deconvolution with nanometer resolution), which resolves populations with subnanometer size differences. This Personal Account summarizes current mechanical unfolding and refolding methods to interrogate single non- B DNA species, with an emphasis on DNA G-quadruplexes and i-motifs. These single-molecule studies start to demonstrate that structures and transitions in non- B DNA species can approach the complexity of those in RNA or proteins, which provides solid justification for the biological functions carried out by non- B DNA species. [ABSTRACT FROM AUTHOR]

Generally, the statistical downscaling approaches work less perfectly in reproducing precipitation than temperatures, particularly for the extreme precipitation. This article aimed to testify the capability in downscaling the extreme temperature, evaporation, and precipitation in South China using the statistical downscaling method. Meanwhile, the linkages between the underlying driving forces and the incompetent skills in downscaling precipitation extremes over South China need to be extensively addressed. Toward this end, a statistical downscaling model (SDSM) was built up to construct future scenarios of extreme daily temperature, pan evaporation, and precipitation. The model was thereafter applied to project climate extremes in the Dongjiang River basin in the 21st century from the HadCM3 (Hadley Centre Coupled Model version 3) model under A2 and B2 emission scenarios. The results showed that: (1) The SDSM generally performed fairly well in reproducing the extreme temperature. For the extreme precipitation, the performance of the model was less satisfactory than temperature and evaporation. (2) Both A2 and B2 scenarios projected increases in temperature extremes in all seasons; however, the projections of change in precipitation and evaporation extremes were not consistent with temperature extremes. (3) Skills of SDSM to reproduce the extreme precipitation were very limited. This was partly due to the high randomicity and nonlinearity dominated in extreme precipitation process over the Dongjiang River basin. In pre-flood seasons (April to June), the mixing of the dry and cold air originated from northern China and the moist warm air releases excessive rainstorms to this basin, while in post-flood seasons (July to October), the intensive rainstorms are triggered by the tropical system dominated in South China. These unique characteristics collectively account for the incompetent skills of SDSM in reproducing precipitation extremes in South China. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A statistically based runoff-yield model is proposed in this paper. The model considers spatial heterogeneities of rainfall, soil infiltration capacity and soil water storage capacity that are main factors controlling runoff-yield process. It assumes that the spatial variation of rainfall intensity at each time step can be characterized by a probability density function, which is estimated by matching the hyetograph through goodness-of-fit measure, whereas the spatial heterogeneities of soil infiltration capacity and soil water storage capacity are described by parabola-type functions. Surface runoff is calculated according to infiltration excess mechanism; the statistical distribution of surface runoff rate can be deduced with the joint distribution of rainfall intensity and soil infiltration rate, thus obtaining a quasi-analytical solution for surface runoff. Based on saturation excess mechanism, the groundwater flow (flows below the ground are collectively referred to as groundwater flow) is calculated by infiltration and the probability distribution of soil water storage capacity. Consequently, the total runoff is composed of infiltration excess and saturation excess runoff components. As an example, this model is applied to flood event simulation in Dongwan catchment, a semi-humid region and a tributary of Yellow River in China. It indicates that the proposed runoff-yield model could achieve acceptable accuracy. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]