Earth and Environmental Sciences

Abstract Atmospheric rivers (ARs) over western North America drive extreme precipitation and flood hazard, yet their intensity upper bounds remain poorly constrained by the short observational record. We combine a differentiable global climate model (~1.4°) with high-resolution dynamical downscaling (~0.11°) to construct physically plausible storylines of five unprecedented AR events in British Columbia. By optimizing minimal perturbations to historical initial conditions, we generate events that maximize integrated vapor transport (IVT) and exceed the observational record under present-day conditions. Pseudo-global warming perturbations under SSP5–8.5 provide a second pathway through end-of-century warming. Both approaches amplify AR intensity through distinct mechanisms: the optimization primarily modifies the wind field, while the pseudo-global warming signal primarily increases atmospheric moisture. These contributions act on largely independent components, and when applied simultaneously, the combined effect is nearly additive, with differences generally below 15%. Non-linear effects, though small, are always positive, and within these storylines the most extreme physically plausible ARs arise from compounding both drivers. The pathways differ in precipitation efficiency: the dynamical amplification largely preserves the conversion of moisture transport to precipitation, whereas the thermodynamic amplification reduces it by up to 29%. Bounding the upper tail of AR hazard may therefore require accounting for both dynamical variability and thermodynamic change.

Tropical cyclones (TCs) are one of the most destructive natural disasters. It is important to document long-term changes in TC properties to better prepare for the damages associated with TCs. TC lifespan is one of the little-studied TC characteristics. Here we show that annual mean TC duration has been decreasing at rates of -13 ± 6 and -7 ± 6 hours per decade, corresponding to approximately 56 and 30 h shorter average lifespans, in the Northeast and Northwest Pacific, respectively, from 1982 to 2024. The decreasing trend is primarily due to shorter TC tracks associated with poleward migration of TC genesis latitude. The TC intensification (weakening) rate before (after) the first (last) lifetime maximum intensity has increased, a phenomenon in which environmental conditions and internal convective structure may both play a role. The shorter TC lifespan over the open ocean before entering coastal zones compresses the time available for weather forecasting and disaster preparedness.

Abstract We investigate the North Atlantic (NA) tropical cyclone (TC) response to a substantial weakened Atlantic Meridional Overturning Circulation (AMOC) under external freshwater forcing using a high‐resolution coupled model. With explicit TC trackings instead of indirect inferences from large‐scale environmental changes, we detect a non‐uniform AMOC‐linked NA TC reduction. The transient TC reduction is more rapid and pronounced over the eastern NA. After several decades, the TCs are almost absent over the eastern NA and the remaining substantially reduced TCs are mostly confined over the western subtropical NA. This non‐uniform TC reduction is related to the equatorward propagation of negative extratropical surface temperature and near‐surface humidity anomalies along a horseshoe pathway as the AMOC weakens. Concurrently, vertical wind shear strengthens over the tropical NA, reinforcing the TC suppression there. In contrast, the AMOC weakening induces TC‐favorable environmental changes (e.g., surface warming) and thus the emergence of TCs over the South Atlantic.

Abstract The deployment of a multistatic radar network in the Oklahoma City metropolitan area in Spring 2024 has allowed for unique observations of several severe weather events. This passive multistatic network operates in conjunction with the operational KTLX WSR‐88D, allowing for synchronous multi‐Doppler analyses. This work presents a case study of a tornadic mesovortex in central Oklahoma. Prior to tornadogenesis, a horizontal rotor circulation is tilted into the mesovortex, providing a pathway for an intense low‐level updraft to develop. The release of horizontal shearing instability beneath this updraft is shown to supply near‐surface vertical vorticity, which is then amplified by vertical stretching, which is followed by tornadogenesis. The ability to derive kinematic fields from a single operational radar represents a major expansion of the current observational capabilities of the WSR‐88D network.

Quantitatively predicting new particle formation (NPF) remains challenging, largely because the true origin of events observed on the surface is often ambiguous. This potential for misattributing particles formed aloft as ground-level events fundamentally compromises predictive models built on local measurements. Here, we propose and validate an analytical framework using airborne eddy covariance and continuous wavelet transform to directly quantify the vertical turbulent flux of newly formed particles and determine their dominant vertical transport direction. Analyzing data from a dedicated airborne campaign over the Southern Great Plains, we observed a consistent and strong downward turbulent flux of ultrafine aerosols during NPF events, with a mean value of −133.8 cm –3 m s –1 in the entrainment zone, whereas fluxes on non-NPF days were negligible. Our spectral analysis further confirms that these directional fluxes can be reliably captured by using standard 1 Hz aerosol instrumentation. These findings suggest that NPF events associated with entrainment from the overlying residual/stable layer during planetary boundary layer growth represent a significant and potentially underestimated source of boundary layer aerosols. The framework presented here provides a new methodology to correctly attribute NPF events to specific altitudes, thereby improving our process-level understanding of particle formation in the atmosphere.

Abstract The Ross Ice Shelf Polynya (RISP) is one of the primary production sites of the High Salinity Shelf Water (HSSW), the precursor of Antarctic Bottom Water (AABW) that drives the lower limb of global meridional overturning circulation. Utilizing a multi‐platform historical data set gathered over the western Ross Sea continental shelf, this study employs a box model to estimate heat and salt budgets in the western RISP and Ross Ice Shelf Cavity (RISC) system. Our analysis identifies three dominant controls on heat and salt budgets in the western RISC: cavity‐polynya exchange (EX), glacial basal melting (GM), and subglacial discharge (SD). The rate of SD is estimated at 87.0 Gt·yr −1 , higher compared with previous studies. This study highlights the role of subglacial discharge in modulating water mass evolution in Antarctic marginal seas, a component that requires incorporation in future climate models.

Abstract Hydrologic modeling supports flood forecasting and water resources management, but complex preprocessing, parameterization, and configuration limit broader use. This study defines a six‐level framework for artificial intelligence (AI)‐agent autonomy in hydrologic modeling and develops a Level‐4 agent, powered by large language models, that translates natural‐language requests into data retrieval, model execution, diagnostics, and reports with human oversight. In a proof‐of‐concept application to the July 2025 Texas flash flood, the agent reproduced key flood dynamics in the tested basin and reduced manual workflow effort. Observation‐driven simulations aligned with streamflow records, whereas a forecast‐driven run missed the flood response because the deterministic rainfall forecast displaced the storm core. These results suggest the feasibility of AI‐agent‐assisted hydrologic modeling in the tested case, while robustness and generalization across broader basins and events remain to be established through systematic validation, probabilistic meteorological forcing, and expert review of automated outputs.

Abstract Katabatic flows over sloping terrain exhibit low-level jets, with turbulent transport becoming dominant over local shear production near the jet maximum, challenging the applicability of classical similarity theory developed for horizontal terrain. This study investigates the influence of slope angle on local similarity scaling in katabatic flows using one-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations with first- and second-order turbulence closures. The strengths and limitations of these models are assessed against observations from the Pasterze Glacier, the Vatnajökull ice cap, the MATERHORN experiment, and the Val Ferret field campaigns. The second-order closure reproduces the observed mean jet structure and momentum fluxes more accurately and is therefore used to analyse turbulence dynamics and similarity relations. A characteristic height scale, $$z_{TM}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>z</mml:mi> <mml:mrow> <mml:mi>TM</mml:mi> </mml:mrow> </mml:msub> </mml:math> , is proposed to identify the region where the recently-proposed slope-adjusted stability parameter of Hang et al. (2021) collapses the local dimensionless momentum gradients across observations and simulations. The observed dimensionless temperature gradient exhibits larger scatter, whereas the simulations show a more consistent trend. Overall results indicate that RANS provides an efficient and viable framework for studying katabatic flows, with the second-order closure resolving processes that the first-order closure does not represent but are essential to katabatic dynamics, and that flux–gradient relations based on the slope-adjusted stability parameter collapse the dimensionless momentum gradient well below $$z_{TM}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>z</mml:mi> <mml:mrow> <mml:mi>TM</mml:mi> </mml:mrow> </mml:msub> </mml:math> , while non-local transport processes limit flux–gradient relations near and above the jet peak.

Study region This study focuses on the Yunnan Plateau in southwestern China, examining nine major plateau lakes: Dianchi, Erhai, Fuxian Hu, Chenghai, Lugu Hu, Qilu Hu, Xingyun Hu, Yangzonghai, and Yilong Hu, all located in high-altitude settings with complex surrounding terrain. Study focus Using newly released Surface Water and Ocean Topography (SWOT) satellite data to monitor lake water-level dynamics, we propose an automated method to retrieve high-precision time-series water levels from SWOT observations. The method aims to improve spatiotemporal monitoring capability and provide a complementary alternative to the official SWOT LakeSP product. New hydrological insights for the region The results show that SWOT, combined with the proposed method, can monitor the nine lakes at a monthly scale with high accuracy (achieving an RMSE of less than 0.09 m). The retrieved water levels reveal clear seasonal variations, with minimum levels generally occurring in April–May and maxima from August to November, consistent with regional precipitation patterns. Intra-annual water-level fluctuations range from 0.23 to 1.20 m. Most lakes exhibit periodic annual variations, whereas Fuxian Hu and Yangzonghai show sustained water-level declines over the available observation period.

Our study focuses on an experimental demonstration of a novel method for CO 2 removal from ocean water, which has captured up to 40% of all anthropogenically released CO 2 emissions, that combines H 2 and redox salt looping to induce pH swings in electrochemical flow cells. Model-driven design optimization guides 3-D printed electrolyte flow channel designs to alleviate mass-transfer limitations. A ridged flow channel with 1 mm thick fins protruding at an angle of 30° from the base reduces ferri-/ferro-cyanide redox salt concentration boundary layer thickness by up to 35% while restricting the pressure drop to less than 415 Pa. A notable feature of this work is the experimental validation of the intrinsic operando cleaning capabilities enabled by the reversible looping process, eliminating what would otherwise be process down time. Over 4 acidification/basification cycles, 86% removal of fouling from electrode surfaces is demonstrated, while distinctly maintaining a constant electrochemical energy intensity. The lab-scale, proof-of-concept experimental demonstration shows promising results, which are interpreted to provide insights and guidelines toward further enhancing scalability and efficiency of oceanic carbon removal and utilization processes.

Abstract The deep Earth water cycle is a key process in Earth's evolution. Stishovite has been proposed as a major carrier of water from the surface into the lower mantle. However, its role remains unclear because its water solubility is controversial. We investigated the water solubility of Al‐free stishovite at pressures of 33–38 GPa and temperatures of 700–1200 K using in situ X‐ray diffraction in an advanced multianvil apparatus. Water solubility is high, around 3 wt%, at 700 K but decreases rapidly with increasing temperature and becomes negligible (&lt;1,000 ppm), at temperatures above 1000 K. These results suggest that pure stishovite is unlikely to transport significant amounts of water into Earth's lower mantle under comparable pressure‐temperature conditions. Previously reported high water contents in pure stishovite under deep Earth conditions likely reflect the solubility of post‐stishovite or experimental artifacts.

High Resolution Image Download MS PowerPoint Slide A potential approach for mitigating the climate impact of hard-to-abate, dilute (less than 1000 ppm; ppm) methane (CH 4 ) is gas-phase advanced oxidation (GPAO). Here, we present experimental results from a benchtop GPAO reactor oxidizing CH 4 with chlorine radicals (Cl · ) produced from the photolysis of chlorine gas (Cl 2 ), a process we term “Cl 2 -GPAO.” We find that at CH 4 concentrations from 2 to 90 ppm, supplying Cl 2 in a ratio of 1:1 with CH 4 uses photogenerated Cl · efficiently, with 3 Cl · photogenerated for each CH 4 oxidized with only 20% of Cl · recombining to Cl 2 . When more Cl 2 is added, the product balance shifts from mainly carbon monoxide to mainly carbon dioxide. Cl 2 -GPAO performs similarly under relative humidities between 5 and 60%. In the presence of ppm-level ammonia, toluene, nitric oxide, and hydrogen sulfide, CH 4 conversion decreases, suggesting that gaseous contaminants compete with CH 4 for Cl · . Gas chromatography–mass spectrometry revealed that Cl 2 -GPAO with 30 ppm CH 4 and Cl 2 produces 1.05 ± 0.32 part per billion (ppb) methyl chloride and 1.25 ± 0.38 ppb chloroform. Methylene chloride and carbon tetrachloride were not detected. We discuss the implications for cost-effective and climate-beneficial Cl 2 -GPAO at scale.

Abstract Using simultaneous magnetic field observations from 10 satellites and an automated detection algorithm, we identify broad regions of electromagnetic ion cyclotron (EMIC) wave activity during the initial phases of geomagnetic storms between September 2015 and October 2019. Since an initial phase typically drives compression of the dayside magnetosphere, we expect the majority of activity to be found here. However, in over 50% of initial phases examined in this study, there is EMIC activity in the nightside magnetosphere. Occurrence of this nightside activity increases as an initial phase progresses, with a lag of at least 35 min before it begins. Additionally, the shock impact angle, solar wind dynamic pressure, and substorm activity level have strong positive correlations to dayside EMIC activity rates compared to nightside. With these observations, we can characterize the extent of magnetospheric response in the form of EMIC wave activity throughout the initial phase of a geomagnetic storm.

Abstract We present observations from two consecutive TRACERS‐2 orbits through the northern low‐altitude cusp. During the first crossing, TRACERS‐2 observed reversed cusp ion dispersion and sunward convection, consistent with magnetopause reconnection tailward of the cusp during this northward IMF interval. Simultaneous THEMIS‐D observations at the equatorial magnetopause show heated magnetosheath plasma captured on closed field lines, with similar particle spectra as in the low‐altitude cusp, indicating that reconnection indeed occurred tailward of the cusp and in both hemispheres. When TRACERS‐2 traversed the northern cusp again, 95 min later, the IMF was dominated by a negative B X component. Despite the different IMF conditions, TRACERS‐2 recorded nearly the same cusp signatures as before, that is, reversed ion dispersion and sunward convection. The observations indicate that tailward‐of‐cusp reconnection can occur for both northward and B X ‐dominated IMF and that these distinct IMF geometries can produce remarkably similar plasma and field signatures in the low‐altitude cusp.

Terraces are a defining feature of Mediterranean mountain landscapes, enabling agriculture on steep slopes while providing multiple ecosystem services. Land suitability analysis (LSA) can guide authorities and land users to sustainably manage and expand these environments. It typically requires fully labelled datasets, but in many real-world applications only a fraction of positive examples is available, with the rest unlabelled. This study aims to present an integrated predictive modelling framework that combines GIS with data-driven Machine Learning (ML) techniques, capable of learning from Positive and Unlabelled (PU) datasets for LSA. The proposed framework was applied to develop a terrace suitability map for Cyprus’ Troodos Mountains. A 5-m DEM was processed to extract the mountain area, with elevation ≥ 500 m and slopes ≥ 15%, defining the study area. Crop plots registered under the Single Area Payment Scheme of the European Common Agricultural Policy were used to classify the study area into Terrace-Present (TP) and Terrace-Absent (TA) cells, with TP serving as labelled positive and TA as unlabelled samples. A two-step ML approach was applied, first identifying reliable negatives from TA cells, then using these with TP cells for suitability prediction. The developed PU-classifier was evaluated under the selected completely-at-random (SCAR) assumption, achieving a Recall of 84.6%, Precision of 81.5% and an F1 score of 83%. Feature importance analysis identified land cover, terrain slope and tree cover density as the most influential parameters for terrace suitability. Comparative analysis between 2017 and 2024 revealed abandonment of terraced agricultural land (29% decrease) as well as revitalisation (12% increase). The resulting suitability map and accompanying data layers are accessible through a Google Earth Engine application, aiming to support informed decision-making for sustainable landscape planning.

Algal organic matter (AOM) is a critical precursor for aquatic photochemical reactions, yet how molecular composition relates to the contrasting photoreactivity of extracellular and intracellular organic matter (EOM/IOM) remains insufficiently understood. This study systematically analyzed the photoreactivity of EOM and IOM derived from representative Chlorophyta and Cyanobacteria. Integrating optical spectroscopy and ultrahigh-resolution mass spectrometry (FT-ICR MS), we characterized the molecular features associated with their photosensitization capacity. EOM, dominated by humic-like substances, functions as a more effective photosensitizer with reactive species (RS) quantum yields up to 22.5-fold higher than protein-like IOM. At the taxonomic level, Chlorophyta-EOM outperformed Cyanobacteria-EOM, whereas Cyanobacteria-IOM exhibited pigment-mediated reactivity. NaBH 4 reduction coupled with FT-IR and 2D-COS suggested that EOM photoreactivity was more sensitive to borohydride-sensitive chromophoric moieties, whereas IOM appeared less affected by borohydride treatment. FT-ICR MS revealed EOM contained relatively lignin/CRAM-like and unsaturated molecular features, while irradiated IOM evolved into more saturated and recalcitrant residues, indicative of photochemical aging. These findings provide molecular-level insights into the divergent environmental fates of algal fractions, highlighting EOM as an important contributor to oxidative self-purification, while irradiation of IOM was associated with photochemical aging and the formation of more saturated residual molecular signatures.

Abstract Dolomite is among the most common carbonate minerals in ancient rocks but its formation is rarely observed today, a longstanding puzzle known as the “Dolomite Problem.” Recent advances in experimental mineralogy, geochemistry, and global abundance reconstructions have begun to resolve this problem. One hypothesis is that dolomitization should be reframed as a two‐stage process involving the nucleation and growth of protodolomite, followed by thermally driven recrystallization. Levenson et al. (2026, https://doi.org/10.1029/2025GL120386 ) provide geochemical evidence for this model using clumped isotope thermometry, finding formation temperatures in Mesozoic dolomites consistent with progressive burial alteration. They suggest that the scarcity of dolomite in younger rocks reflects insufficient time at elevated burial temperatures. Alternative pathways to dolomite formation, including at low temperatures and shallow burial depths, also deserve continued consideration as the community works toward a more complete resolution of the Dolomite Problem.

ABSTRACT This study compares eight third‐round NDC submissions to assess ambition, data systems, sectoral coverage, and adaptation planning. Using qualitative content analysis and cross‐country benchmarking, it evaluates institutional readiness, sectoral alignment, financing feasibility, and monitoring, reporting, and verification (MRV) quality. Results show rising ambition but persistent implementation gaps. Lower‐income countries emphasize vulnerability and equity yet face data and financing constraints. Sectoral pathways and baselines vary, limiting comparability. NDC4.0 should strengthen MRV systems and define clear, harmonized sectoral trajectories.

Despite widespread recognition of dermal exposure to hazardous compounds transferred from consumer products, limited information exists on the friction-mediated transfer of low molecular weight (LMW) chemicals. These chemicals, readily soluble in skin secretions, may pose prolonged dermal exposure risks. To address the knowledge gap, we investigated the frictional transfer of chemicals (formamide, benzothiazole, p -bis(2-hydroxyisopropyl)benzene ( p HPB), and bis(2-ethylhexyl) terephthalate (DEHT)) from mats to rubbing fabrics under dry and skin-secretion conditions to simulate clothing-mediated dermal exposure. Gas-phase emissions were also measured. Under dry conditions, transfer efficiencies inversely correlated with molecular weights, namely, for formamide (0.072–0.4%), benzothiazole (0.047–0.072%), p HPB (0.0054–0.035%), and DEHT (0.00037–0.0083%). Skin secretions facilitated friction-mediated chemical transfer, with the extent of facilitation correlating with log K ow . Sweat increased formamide accumulation 5.6–9.0-fold, while sebum boosted DEHT transfer up to 110-fold. Chemical transfer was amplified under intensified mechanical conditions (duration, load, and sliding speed) and modulated by mat surface roughness. In 30 min exercise simulations, formamide (an LMW chemical) transfer efficiency through friction (0.16–1.6%) was comparable to that through gas-phase emission (0.026–0.23%). These findings indicate that frictional contact is a significant pathway for LMW chemical transfer from mats to clothing, providing critical insight for dermal exposure.

Railway infrastructure requires the execution of various nonroutine interventions over time, such as major track renewals, infrastructure upgrades, and technological improvements, to ensure continued safety and meet evolving transportation demands. The full planning process for these interventions spans multiple departments and planning phases, yet no single unit or individual typically holds a complete ownership or visibility over the full process. This fragmented understanding hampers efforts to improve planning efficiency and effectiveness, as innovation efforts targeting isolated planning phases or tasks often overlook their temporal and functional interdependencies. Tasks may rely on inputs from upstream tasks, must deliver outputs to downstream tasks, and are often initiated years in advance of intervention execution. This work provides a detailed description and discussion of the nonroutine intervention planning process within a Swiss railway organization. Using Business Process Model and Notation (BPMN) 2.0, the process is modeled across several key phases, including (1) network development; (2) development intervention planning; (3) maintenance intervention planning; (4) network coordination; (5) production planning; (6) project planning; and (7) capacity planning. The findings highlight the challenges in improving the planning process in railway organizations and point out several ways that research could be focused to improve the process that are best identified when understanding the full process. The areas of research identified are efforts to improve (1) integrated planning and process alignment; (2) process transparency and ownership; (3) interdisciplinary coordination and communication; and (4) decision support through operations research, machine learning, and digital tools such as building information modeling and geographic information systems. Beyond these identified areas of research, the described planning process is unique in its level of detail and, to the best of our knowledge, the first of its kind in the published literature, and it offers a foundational reference for academic research and practical improvement initiatives in similar contexts.