Abstract The Madden–Julian oscillation (MJO) produced by an idealized general circulation model (GCM) is studied. The model is a spectral dynamical core with a simple treatment of the hydrological cycle; MJO-like variability is induced by forcing zonal sea surface temperature gradients in the tropics using a prescribed ocean heat flux. Surface friction in the model is perturbed by altering the roughness length for momentum. The MJO weakens and eventually disappears entirely as the roughness length is decreased from its control value. The MJO is found to be sensitive to the roughness length in both the tropics and extratropics. Composite disturbances are constructed; the MJO has an associated vortex dipole straddling the equator. A similar vortex dipole exists when the roughness length is small, where disturbances have a closer connection to Rossby modes than to the MJO. In the lower- and midtroposphere, the main difference in the vorticity budgets of these two modes is in the rotational advection of vorticity, though the rotational terms are not dominant in the upper troposphere where the absolute vorticity is small. It is argued that greater nonlinearity relative to the mean rotational flow when the roughness length is large causes the transition of Rossby modes into the MJO. Connections to theories for the MJO which focus on the role of nonlinear Rossby wave dynamics are explored. Despite the strong influence on MJO variability, the statistics of the leading principal components of the velocity potential and the structure of the corresponding empirical orthogonal functions are insensitive to changes in the roughness length.

This study clarifies the hydrological cycle structure of the Pingjiang underground river system using hydrogeological mapping (1:50,000), tracer tests, automated groundwater monitoring, and RTK surveys. The obtained results indicate the following: (1) The Pingjiang underground river basin covers an area of 110.66km² and consists of five tributary conduits, forming a dendritic-network composite structure dominated by unilateral recharge; (2) The threshold rainfall required to generate surface runoff is around 20mm, which may exceed even 50mm under prolonged drought conditions. When the daily rainfall exceeds 50mm, the discharge at the underground river outlet increases significantly. The karst conduit system demonstrates a pronounced flood attenuation effect, capable of delaying the flood peak by up to 21h. (3) The flow dynamics at the sinking stream inlet and underground river outlet exhibit strong consistency. The discharge at the outlet ranges from 0.35m3/s to 25.57m3/s, displaying flashy characteristics. The Bujing sinking stream inlet contributes 18.86% of the annual runoff to the underground river. (4) The underground river has a baseflow runoff modulus of 3.21L/s·km2 during the dry season.

Hydrodynamically triggered landslides remain a major concern in reservoir regions, where the mechanisms controlling displacement evolution are still not fully understood and the multi-scale deformation responses induced by individual hydrodynamic factors remain difficult to quantify. To address these issues, this study establishes a TSD-TET composite framework by integrating time-series signal decomposition with deep learning for multi-scale displacement prediction and the mechanism-oriented interpretation of hydrodynamically triggered landslides. The monitored displacement sequence is first decomposed into physically interpretable components, including trend, periodic, and random terms. Each component is subsequently predicted using deep temporal learning models to capture different deformation characteristics at multiple temporal scales. Meanwhile, key hydrodynamic driving factors, including rainfall, reservoir water level, and groundwater level, are decomposed within the same framework to examine their statistical associations with different displacement components. The proposed approach is applied to the Donglingxin landslide located in the Sanbanxi Hydropower Station reservoir area. Results show that the model achieves high prediction accuracy under both long-term forecasting horizons and limited-sample conditions, with a cumulative displacement coefficient of determination reaching R2 = 0.945. Mechanism analysis further indicates that trend deformation is mainly controlled by geological structure and gravitational loading, periodic deformation is strongly modulated by hydrological cycles associated with reservoir water level fluctuations, and random deformation is more likely to reflect short-term disturbances and transient hydrodynamic forcing. These findings provide new insights into the deformation mechanisms of hydrodynamically triggered landslides and offer a promising technical pathway for improving displacement prediction, monitoring, and early warning of reservoir-induced landslide hazards.

Biological soil crusts (biocrusts) develop vertical redox-microbial-nutrient stratification that regulates hydrological and elemental cycles and contributes to ecological restoration in extreme environments, including mining regions. However, the roles of this heterogeneity in metal(loid) immobilization remain unclear, particularly in humid regions, where pronounced redox and microbial stratification may foster unrecognized stabilization mechanisms. We integrated physicochemical characterization with bioinformatic analysis to reveal stratified microbial communities and metabolic potentials in humid tailings biocrusts. Biocrusts exhibited stratified functionality through the upper photoautotrophic layer (PL) and the lower heterotrophic layer (HL). In the PL, Cyanobacteria and SWB02 formed a self-reinforcing oxygen barrier through clay-silt enrichment (2.8-fold higher than bare tailings sand) and extracellular polysaccharide accumulation (18-fold), which swelled upon hydration to physically hinder oxygen infiltration, confining Gammaproteobacteria-associated iron-manganese oxide immobilization to this layer. Beneath this barrier, the HL harbored sulfidogenic potential through microbes enriched in hydB (17.4-fold) and phsC (3.4-fold) genes, including Bacteroidota and Desulfobacterota, supporting a potential mechanism for metal(loid) sequestration via sulfide formation in underlying tailings, where sulfur occurred exclusively as sulfides at 5 cm depth. This barrier-mediated effect may outweigh metal(loid) immobilization within biocrusts. Our findings elucidate biocrust-mediated protection against metal(loid)s and provide theoretical support for remediation in humid mining regions.

ABSTRACT Soil moisture is critical for understanding the hydrological cycle and managing climatic extremes such as floods and droughts. This study evaluates the accuracy of satellite-derived soil moisture estimates from remote sensing satellite products Soil Moisture Active Passive (SMAP), Soil Moisture and Ocean Salinity (SMOS), and Advanced Microwave Scanning Radiometer-2 (AMSR-2) in the absence of ground observations. A selective fusion algorithm is introduced that enhances accuracy by fusing data only in regions where it improves the precision of soil moisture estimates, rather than applying a uniform fusion approach across all regions. Using Extended Triple Collocation (ETC) analysis, the error characteristics of individual satellite products are assessed across spatial, temporal, and meteorological aspects. Additionally, Mutual Information (MI) analysis with precipitation data quantifies the information content of each product to validate their effectiveness. Our results demonstrate that SMAP consistently exhibits the lowest error characteristics and highest information content. Notably, AMSR-2 shows superior performance in hot desert and semi-arid regions, highlighting the need for a spatially adaptive fused soil moisture product. An integrated fusion algorithm, guided by a decision map based on these analyses, optimizes the selection of soil moisture products across India’s diverse regions. This decision map revealed the highest spatial coverage by SMAP (62.5%), followed by AMSR-2 (25.7%) and SMOS (5.6%), with the remainder attributed to various combinations of products that provide superior soil moisture estimates in specific contexts. This modified fusion approach is implemented using a Linear Weight Fusion (LWF) technique, significantly enhancing the reliability of the resultant soil moisture product, particularly evident from its validation against data from three in-situ stations. The integrated approach not only refines the accuracy of satellite-derived soil moisture data but also provides a robust framework for enhancing hydrological model predictions, especially in drought monitoring.

Enhancing run-of-river hydropower capacity assessment through integrated time series flow regime modeling and continuous wavelet transform analysis.

ABSTRACT Uptake and distribution of soil water by vegetation is a dynamic phenomenon, which is of utmost importance due to its role in the hydrological cycle and terrestrial productivity. Despite the significance, the soil water–vegetation interaction remains unexplored in large parts of the world, particularly in the tropical forested regions. This study, through measurements of oxygen isotopic compositions (δ 18 O) of water in different hydrological components, such as streams, xylem, groundwater, root and soil pore water, focused on understanding the eco‐hydrological connectivity during the dry season in a tropical humid forest (Western Ghats, India—a biodiversity hotspot). The results indicated that only 12% of the riparian trees primarily accessed stream water, and the dominant portion (36%) of the trees showed lower δ 18 O than the expected (sampled) sources, indicating access to an unsampled/deeper water source, probably accessed only during the summer season to withstand low plant water potential. We explain this isotopic difference by differential access to shallow, deep and redistributed soil water, providing insights into the contribution of multiple water sources to transpiration. Hydraulic redistribution (i.e., root‐mediated transport of deep water to upper soil layers) served as a critical water source for shallow‐rooted plants, helping them meet their water requirements during dry periods. Evidence for limited percolation of water into deeper soil due to quick filling of shallow soil pores during short and heavy precipitation events was noticed, highlighting the importance of continuous moderate rainfall for effective water percolation into the deeper soil.

Impacts of multiple reservoirs on hydrological cycle and hydrochemical evolution in a mountainous river basin of the North China Plain.

Abstract X‐ray amorphous materials (XAMs) are observed to be prevalent on the Martian surface, though their formation mechanisms remain unclear. In this study, we utilize mineralogical data from Zhurong, China's first Mars rover, to provide a deeper understanding of this issue. The shortwave infrared spectra revealed signals of Al‐OH near 2.20 μm, and signals of the vibrations of water molecules and hydroxyl in sulfates around 1.95 μm. These findings suggest the presence of clay and possibly Al‐bearing XAM along with sulfate. Comparative studies of analog samples from the western Qaidam Basin and brine soaking experiments present a mineral evolution model for the formation of XAM through clay‐brine interactions. In this model, evaporites crystallize within the interlayers of clay minerals, impacting their structural stability. Structural ions may be continuously released due to the attack of H + ions, forming XAMs as liquid water rapidly evaporates. These findings indicate that clay‐brine interactions could extend beyond the Martian southern hemisphere, highlighting the importance of carefully considering the ancient hydrologic cycle and the resulting post‐depositional impacts on surface minerals in salt‐weathering environments on Mars.

SWOT performance in monitoring water level of high-mountain lakes on the Tibetan Plateau

Spatio – temporal hydrological cycle characteristics in the upper reaches of the Yangtze River: A multi-source remote sensing and machine learning perspective

Groundwater resources are increasingly threatened by rapid urbanization, which disrupts the natural hydrological cycle. Urban development replaces permeable soils with impervious materials such as concrete, asphalt, and interlocking pavers, thereby reducing aquifer recharge and altering streamflow patterns. This study analyzed the impact of urban expansion on groundwater recharge in the Chaliyar basin, Kerala, over a 20-year period (2002-2022) using remote sensing data. The results revealed a 208% increase in built-up areas, with substantial conversion of natural land to urban surfaces including buildings, roads, and pavements. Field infiltration tests conducted at 20 locations following ASTM C1701 and ASTM D5126-90 standards showed a complete loss (100% reduction) in infiltration capacity in areas with concrete, roads, and buildings, and an 80 ± 1.61% reduction under interlocking pavers compared to natural soil. Consequently, the basin experienced a 48.5% decline in groundwater recharge and a 70% rise in surface runoff during the study period. These findings underscore the severe impact of unplanned urbanization on groundwater dynamics and highlight the urgent need for sustainable urban planning practices that enhance surface permeability and ensure long-term groundwater sustainability.

Functional dynamics of fish assemblages in a tropical estuary during different phases of El Niño‒Southern Oscillation.

There exists strong geomorphological, sedimentary and mineralogical evidence that Mars had an active surface hydrological cycle during the Noachian period, about 3.8 Gyr ago (Ga). However, how surface temperatures compatible with perennial liquid water could be sustained in spite of a Sun that only had 75% of its present-day brightness has remained elusive, leading to the faint young Sun paradox for Mars. Recently, the greenhouse effect of hydrogen peroxide (H 2 O 2 ) has been proposed as a solution by Ito et al. (2020). Radiative transfer models have shown that a few ppmv of H 2 O 2 in a 1 or 2 bar CO 2 atmosphere could solve the faint young Sun paradox on early Mars. In a warm and wet CO 2 atmosphere, H 2 O 2 is produced by photochemistry and contributes to the stability of the CO 2 atmosphere along with the HO x (H, OH and HO 2 ) catalytic cycles. Nevertheless, a thorough assessment of the viability of such a high H 2 O 2 abundance is still lacking. Using 1D and 3D climate models coupled with a C-H-O photochemistry solver, we show that in the most favourable case for H 2 O 2 to build up, its steady-state abundance is several orders of magnitude short from its required abundance of ∼ 1 ppmv to have a significant radiative effect. Furthermore, we also show that a transient warming episode associated with massive H 2 O 2 release cannot exceed 10 Martian years. We therefore rule out H 2 O 2 as a warming agent for early Mars. • An upper bound for the abundance of hydrogen peroxide (H 2 O 2 ) in a warm and wet early Mars atmosphere is determined using coupled 3D global circulation model and photochemistry simulations. • Hydrogen peroxide does not exceed a few ppbv in a 2 bar CO 2 atmosphere, which is too low to induce greenhouse warming. • In a warm and wet early Mars atmosphere, CO 2 restoration relies approximately as much on odd hydrogen (H, OH and HO2)-based as on hydrogen peroxide-based catalytic cycles. • Transient extreme release of hydrogen peroxyde dissolved in an ice cap might raise the surface temperature above 273 K for less than 10 Martian years at most.

ABSTRACT Water remains the most critical limiting resource for the arid and semi‐arid China's Loess Plateau (CLP). Over the past three decades, large‐scale ecological restoration (ER) has significantly increased vegetation coverage but also altered the regional hydrological cycle. This study quantifies the spatiotemporal dynamics of water resource conflicts (WRC) by integrating multisource remote sensing data and the water balance equation, and predicts future trends (2021–2100) under CMIP6 climate scenarios. The results indicate that: (1) While vegetation greening has enhanced ecosystem services, it has intensified the trade‐off between ecosystem water use and human demand, contributing to a 30% reduction in average annual runoff from 2000 to 2020. (2) WRC has become prominent, with available water resources approaching sustainable limits in 2020, particularly in Central and Northern Shanxi and Northern Shaanxi provinces. (3) However, future projections under SSP2‐4.5 and SSP5‐8.5 scenarios suggest a turning point: benefiting from a predicted warmer and wetter climate, the intense WRC is projected to be alleviated by 2100. These findings reveal the nonlinear evolution of water scarcity and provide critical insights for adaptive water management in dryland restoration.

Unveiling fDOM dynamics in shallow lakes via a coupled "spectral-thermal" XGBoost-SHAP retrieval framework: Implications for water diversion management in Lake Honghu.

Unraveling future hydrological and sediment dynamics through an integrated GCMs-PLUS-SWAT coupling framework.

The páramo is a high-altitude ecosystem characterized by its herbaceous vegetation and distribution in tropical and subtropical regions. This ecosystem is highly sensitive to environmental disturbances, making it a priority area for conservation and research due to its biodiversity and strategic ecosystem functions. Consequently, it is essential to conduct ecological and conservation studies of páramo areas within interdisciplinary frameworks that address the various environmental, geopolitical, economic, and sociocultural challenges. The objectives of this study were: (1) to identify the richness of páramos and the evolution of knowledge in research during the period from 2014 to 2023; and (2) to determine the scientific output, keyword cooccurrence in articles, and the most influential researchers in the field during the period from 2014 to 2023. The methodology employed was descriptive bibliometric analysis, involving a comprehensive search for scientific articles in the Scopus database. For parameter visualization, VOSviewer and the Bibliometrix package in R Studio were used to apply Lotka’s Law. The results show that Colombia is the leading country in scientific production in this field, playing a central role in advancing knowledge about the páramo. Furthermore, the findings indicate that the impact of climate change and intensive human activities (such as agriculture, grazing, pine plantations, and tourism) have increased the risk of páramo degradation, altering hydrological cycles and reducing its regulatory capacity. This bibliometric study provides a robust foundation for the planning of public policies aimed at conservation, sustainable water resource management, and biodiversity protection in páramo ecosystems. Therefore, it is crucial to promote research that considers the páramo as a socio-ecological system, analyzing the interactions between human actors and the natural environment, which will enable the design of more equitable and effective management policies.

ABSTRACT Canopy conductance (Gc) is critical for assessing forest ecosystem responses to climate change. The Hanjiang River Basin represents a typical subtropical humid region in China and serves as the water source for the middle route of the South‐to‐North Water Diversion Project. Studies on canopy conductance of trees in this region remains lacking, limiting the corresponding understanding of forest transpiration and hydrological cycle. In this study, we measured sap flux density and derived canopy conductance (Gc) of three representative tree species of oak, pine and poplar from 2021 to 2023. We then explored characteristics of Gc and the corresponding responses to key environmental factors. Results showed that incoming short‐wave radiation (Rsi) and vapour pressure deficit (VPD) are the two major controlling factors of Gc, and a crossed hysteresis pattern exists in the diurnal response of Gc to Rsi for all the three species, whereas the response of diurnal Gc to VPD (and air temperature) exhibits a closed clockwise hysteresis. The response of Gc to VPD has a clear VPD threshold: A linear relation was found when VPD is lower than the threshold, and a logarithmic relation was found when VPD is higher than the threshold. When taking Rsi and VPD as controlling factors of Gc, a statistical model for canopy conductance was developed; the model can explain over 64% of the variation in Gc for all the three tree species. This study contributes important knowledge to understanding the canopy conductance of representative tree species in the Hanjiang River Basin.

Abstract Background Andean Páramos represents a unique ecosystem, which is rich in diversity and endemism that plays a key role in climate regulation, hydrological cycle, and biodiversity. However, these ecosystems are among the most threatened due to deforestation and fire associated with agricultural activities. Methods This study provides the first assessment of vascular plant diversity in response to experimental prescribed fire in a grassy páramo in southern Ecuador. Three permanent sampling plots (T1, T2, and a control) were established, each measuring 4 m × 20 m (80 m 2 ) and separated by 3 m. T1 was subjected to burning in the direction of the slope, T2 was burned against the slope, and the control plots were left unburned. Monitoring was conducted at three intervals: 2, 12, and 24 months post-burn. In each plot, vascular plant cover and species richness were assessed using a 1 m × 1 m quadrat. Results A total of 29 vascular plant species were recorded, distributed in 20 families and 29 genera. Fire treatments and time since burning significantly influenced vascular plant diversity, while community composition differed between the control and burned plots (T1 and T2). Conclusions These findings suggest that both alpha and beta diversity of vascular plants serve as valuable indicators of fire effects in páramos. Thus, prescribed fire may serve as an essential tool for ecological management and vegetation restoration in tropical páramos.