Search Results (481)

Simulation of the surface energy balance (SEB) is essential for land–atmosphere coupling and weather–climate prediction, yet land surface models remain uncertain in turbulent and ground heat fluxes. We evaluated CoLM2024 with Land Cover Type (LCT) and Plant Community (PC) schemes and ECLand v1.0 against energy-balance-corrected observations from 80 PLUMBER2 towers spanning 11 land cover types. Observations and simulations were decomposed at 30 min, daily, and monthly scales. All experiments reproduced net radiation well, whereas ground heat flux was poorly simulated over forests and wetlands with excessive daytime amplitude. ECLand achieved the best latent heat flux performance through smaller systematic errors. PC reduced unsystematic errors, but this benefit was offset by a large negative growing-season bias. Sensible heat flux performance varied among land-cover classes: PC performed best over evergreen needleleaf and mixed forests, while ECLand was superior over broadleaf forests and had the lowest unsystematic errors, although with damped variability at all timescales. Performance was scale-dependent: ECLand was favored at 30 min, PC was competitive for daily forest sensible heat correlations, and no consistent ranking emerged monthly. These results indicate that complex canopy schemes require robust formulations, improved heat-storage, and careful parameter calibration to translate process detail into better flux simulations. Full article

In order to clarify the effects of the volcanic activity on hydrological, thermal and chemical features of a crater lake, Lake Katanuma, Japan, temperature and electrical conductivity at 25 °C (EC25) of lake water were monitored at two maximum-depth points in 2023−2025. Under closed condition of the lake without river outflow, the lake is characterized by a high acidity of pH = 2 on average and the existence of the surrounding geothermal area. A seasonal variation in the thermal and chemical features of the lake was shown by sporadic vertical profiling (0.1 m pitch) of temperature, EC25 and dissolved oxygen (DO) at the two points. The groundwater flow system around the lake was specified by quantifying the groundwater inflow G_in and groundwater outflow G_out in the lake from the estimate of hydrological and chemical budgets under no precipitation. During the pycnal stratification of May–September, the lake exhibited a four-layer structure with different temperature and EC25 values, probably due to the lower intrusion of groundwater passing through three different pathways. The four-layer structure disappeared due to vertical mixing in October–December and March–April and inverse stratification in January–February. The G_out and G_in values were estimated for three budget periods in the mixing season. Utilizing Darcy’s law for the G_out values as a confined groundwater flow, it is found out that G_out has a linear relationship with lake volume. The relatively high G_in and G_out values estimated are probably caused by the high permeability of lacustrine sand and gravel deposited as bedrock, which furnishes the high adjustability to lake level, i.e., its small variation at ca. 0.5 m in amplitude. Full article

Increasing frequency and intensity of heat events pose significant challenges for the production and early establishment of urban trees. This study evaluated whether horticultural interventions could mitigate heat stress and improve growth of young red maple (Acer rubrum ‘FranksRed’) under full-sun conditions representative of urban planting environments. Six treatments (control, canopy misting, paclobutrazol, propiconazole, kaolin clay, and potassium phosphite) were evaluated over two growing seasons in the Willamette Valley, Oregon, which were characterized by hot, dry summers and episodic heat waves. Canopy temperature, soil volumetric water content, and growth were monitored using high-resolution sensor networks and analyzed using mixed-effects modeling to account for repeated measures and environmental covariates. Across both years, mean canopy temperature largely tracked ambient conditions, and treatment effects on absolute temperature were modest. However, canopy misting reduced daily canopy temperature amplitude (ΔT) and maintained the highest soil volumetric water content, while both misting and kaolin consistently reduced exposure to the highest canopy temperature thresholds. Although these reductions in cumulative thermal exposure were not statistically significant, they coincided with improved tree growth. The chemical treatments produced smaller, context-dependent effects. Despite modest temperature differences, stem caliper increased by 10–20% under misting relative to the control (p < 0.05). Growth responses indicate that small changes in canopy thermal exposure and soil water availability can translate into meaningful differences in early tree performance. These results demonstrate that the absence of strong treatment effects on mean canopy temperature does not preclude biologically relevant outcomes. Management strategies that modify canopy thermal dynamics or plant water relations may improve growth and establishment potential of young trees under increasingly extreme thermal conditions, even when ambient heat loads cannot be fully mitigated. Full article

Seasonal variation in SARS-CoV-2 transmissibility is difficult to estimate directly from year-round epidemic data because interventions, behavior, reporting, immunity, and viral evolution change concurrently. We therefore asked whether cross-country differences observed during the initial exponential-growth phase could be used to infer country-specific seasonal modulation. Early-pandemic basic reproduction numbers (R₀) from 118 countries were linked to 96 harmonized environmental and population-level predictors. Among nine candidate algorithms evaluated across 100 repeated train–test splits, ridge regression using the combined predictor set provided the best balance of predictive accuracy, generalization, and temporal stability. The selected model was then driven by daily climatological covariates to reconstruct annual baseline R₀(t) profiles. Predicted transmissibility generally peaked during winter in the Northern Hemisphere and approximately six months later in the Southern Hemisphere, whereas equatorial countries showed weaker or multimodal patterns. Seasonal forcing amplitude increased strongly with absolute latitude (r = 0.85; mean 0.064 across 77 temperate countries), and predicted R₀ peaks aligned more closely with minimum ultraviolet radiation than with minimum temperature. These ecological associations do not establish causality, but they provide country-specific seasonal-forcing parameters for epidemic models and a baseline environmental context for comparing early-pandemic trajectories. Full article

To gain a deeper understanding of the lower-atmospheric dynamic characteristics in the transition zone on the northeastern margin of the Tibetan Plateau, high-resolution wind profile data collected by a Doppler wind lidar (DWL) at Yinchuan Hedong International Airport from 2021 to 2023 were used to analyze the vertical structure, seasonal variations, and diurnal characteristics of the low-height wind field and wind shear in this region. The results indicate that (1) the data acquisition rate (DAR) below 1.5 km is generally high, exceeding 90% during most periods, and decreases monotonically with height; the 90% DAR contour height exhibits clear seasonal and diurnal variations, with the largest diurnal amplitude in summer and the smallest in winter. (2) The middle- and low-height wind fields are jointly modulated by topographic forcing and local circulations. Below 0.4–0.7 km, north–northeast and south–southwest winds prevail across all seasons, which is consistent with the blocking and splitting effects of the Helan Mountains. At 42 m, the wind direction shows a marked diurnal transition that may reflect the combined influence of the Helan Mountains’ bypass flow, mountain–plain circulation, and thermal contrasts between the Yellow River and surrounding desert/plain surfaces. (3) Horizontal wind speeds are predominantly concentrated below 6 m s⁻¹, and the development height of this low-wind-speed zone varies seasonally. The vertical velocity statistics show weak positive values in parts of the observed layer, but these signals are interpreted cautiously because vertical-velocity retrieval is subject to additional uncertainty. (4) The low-level wind shear intensity reaches its peak below 100 m and generally exhibits a U-shaped vertical distribution; severe wind shear below 100 m occurs most frequently from nighttime to early morning during May–October, whereas its occurrence frequency is lowest in winter. These findings provide observational evidence for aviation meteorological support and boundary-layer studies in semi-arid regions of Northwest China. Full article

Soil respiration (Rs) is a key component of terrestrial carbon cycling, yet its temporal structure and vertical environmental controls remain insufficiently understood. This study investigated Rs and its components across four subtropical forest types in Hunan, China, using high–frequency 24–h observations combined with multi–month monitoring and measurements at three soil depths. Temporal dynamics were analyzed using harmonic fitting and two–way ANOVA–based variance partitioning, and environmental controls were quantified using linear mixed–effects models and relative importance analysis. Results showed that annual Rs ranged from 473.50 g C m⁻² yr⁻¹ in secondary broadleaf forest to 652.50 g C m⁻² yr⁻¹ in pure Pinus massoniana Lamb. plantation, with heterotrophic respiration dominating all stands (68.9%–82.1% of Rs). The cosine model best described diel cycles in 64.6% of cases, with amplitude significantly higher in summer than in winter. Variance partitioning revealed that seasonal (month) scale explained 89.2%–97.3% of total variation in Rs and Rh, whereas diel (hour) scale contributed only 0.4%–4.8%; for Ra, seasonal contribution dropped to 36.1%–73.7% and residual variance surged to 21.9%–54.3%, indicating substantially greater stochasticity. Linear mixed–effects models showed that topsoil temperature (0–10 cm) was the dominant driver of Rs and Rh, explaining 48% of their variation, whereas Ra was additionally regulated by subsurface soil moisture and conductivity, with only 19% of variation explained. Overall, soil respiration exhibited a structured, multi–scale, and depth–dependent response system shaped by forest type, temporal variability, and depth–specific soil heterogeneity. Full article

Pronounced spatio-temporal variability of rainfall in semi-arid basins remains a central challenge for rainfall–infiltration–runoff modeling, particularly in ungauged or newly instrumented catchments where continuous soil-moisture data are unavailable. This study evaluates the comparative predictive performance of the SCS-CN and Green-Ampt (GA) infiltration methods, implemented within HEC-HMS at the sub-basin scale, using eight rainfall–runoff analysis time windows recorded during the 2020–2025 rainy seasons within a monitoring network operational since October 2019 in an instrumented semi-arid basin in Mexico. A blind-validation framework was adopted: parameters for both methods were derived a priori from tabulated sources indexed by land use, hydrologic soil group, soil textural class, and locally supported by textural analysis at three depths per sub-basin, in situ testing of saturated hydraulic conductivity, and gravimetric determination of field capacity; the initial moisture content required by GA was set equal to the measured field capacity (θ_i = θ_fc) to equate initial conditions between the two methods. Spatially distributed rainfall was captured by four monitoring stations under a one-to-one gauge–sub-basin assignment scheme, with monthly rainfall depth varying from 22.8 to 204.9 mm across the four sub-basins. Both methods reproduced observed discharge with varying levels of agreement: SCS-CN yielded very good performance (Pearson R = 0.95; Nash–Sutcliffe efficiency NSE = 0.76), whereas Green-Ampt yielded moderate correlation but unsatisfactory NSE (R = 0.70; NSE = 0.45) against the Levelogger records. Contrary to the initial expectation that the physically based GA would outperform SCS-CN, SCS-CN yielded substantially higher performance across windows, with the two simulated discharge series differing by a mean absolute deviation of 36.9 m³/s. A systematic sensitivity analysis (±6%, ±10%, ±20% perturbations) revealed an asymmetric response: SCS-CN was highly sensitive to Curve Number perturbations (mean-deviation amplitude 65.9 m³/s), whereas Green-Ampt was nearly insensitive to its compound soil-hydraulic parameterization (amplitude 3.2 m³/s), indicating a structural limitation of the physically based method under blind validation. Full article

This study presents a multivariate spatio-temporal clustering framework to characterise joint wind–wave regimes across European seas using the fifth-generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ERA5; 1979–2014). Seasonal and annual statistics of significant wave height, mean wave period, wind speed, and wave/wind direction were computed at 0.5° resolution. Principal component analysis was used to reduce dimensionality, retaining 30 components that captured 99% of the variance. K-means clustering was then used to identify nine coherent dynamical regimes with persistent spatio-temporal signatures. These regimes were grouped into open-ocean, transitional, and enclosed/semi-enclosed categories based on internal variability, directional spread, and geographic exposure. Open-Atlantic regimes are found to be energy-rich, exhibiting clear December–February maxima in significant wave height ($H_s$), mean wave period ($T_{02}$), and 10 m wind speed ($W_{s10}$); enclosed and semi-enclosed basins show lower amplitudes and reduced variability, while transitional shelves and the southern Mediterranean display intermediate conditions, characterised by moderate $T_{02}$ levels and seasonal rotation of wave and wind directions, reflecting a mixed influence of locally generated seas and remotely forced swell. Dispersion analysis highlights a clear Atlantic–Mediterranean partition, with transitional shelves forming a dynamical bridge between open-ocean and enclosed basins. Teleconnection analysis shows that the North Atlantic Oscillation and Arctic Oscillation dominate Atlantic regimes, while the Scandinavia, East Atlantic, and Polar/Eurasia patterns modulate variability and directional persistence in transitional and enclosed seas. The classification defines a climatological framework of European wind–wave conditions and establishes a practical basis for renewable energy assessment, engineering design, and long-term change analysis, with methods transferable to other basins. Full article

Long-term temperature reconstructions provide essential context for evaluating regional climate change, but synthesis across China is complicated by uneven spatial coverage, seasonal sensitivity, and proxy-specific biases. Here, we compiled 93 published quantitative temperature records spanning the past 10,000 years and applied a Bayesian multilevel regression framework to reconstruct national and subregional temperature trajectories. Annual mean, summer, and winter temperatures were compared among four climatic regions, proxy groups, and sedimentary archives. Within-stage temperature ranges were assessed using both primary and robust-extrema estimators. National annual mean and summer integrations indicate generally warmer early–middle Holocene conditions followed by late-Holocene cooling, whereas winter results remain exploratory because only five records are available. Regional trajectories were heterogeneous, with stronger cooling in northern monsoon China, larger within-stage proxy-derived ranges in the northern non-monsoon region, weaker changes in southern monsoon China, and pronounced seasonal differences on the Tibetan Plateau. Large branched glycerol dialkyl glycerol tetraethers (brGDGTs) and loess amplitudes were substantially reduced by robust estimation, suggesting sensitivity to isolated extremes and archive-specific processes rather than direct atmospheric temperature changes. These results demonstrate that regional, seasonal, proxy, and archive-specific baselines are essential for interpreting paleoclimate evidence and its implications for ecosystem and resource management. Full article

Understanding how urbanization modifies stream thermal regimes is essential for assessing freshwater ecosystem responses to climate variability and land-use and land-cover (LULC) change. This study investigated air temperature (AT)–water temperature (WT) relationships at annual, monthly, and diurnal timescales in two adjacent, relatively flat watersheds with contrasting urbanization levels in North Central Texas: the urbanized Doe Branch and less urbanized Little Elm Creek during 2012–2021. A single harmonic analysis was applied to characterize annual and diurnal thermal patterns, including mean temperature, amplitude, and phase, while statistical analyses were used to evaluate seasonal and daily thermal variability and peak timing. At the annual scale, AT and WT metrics were strongly correlated at both sites (r = 0.85–0.94, p < 0.01) indicating that atmospheric conditions were the dominant control of annual stream temperature variability. Annual mean WT increased with AT, suggesting strong air–water thermal coupling and the potential for warmer stream temperatures under future climate warming. However, Doe Branch exhibited higher annual mean WTs, delayed seasonal peak WTs, and reduced annual temperature ranges compared with Little Elm Creek, reflecting the influence of urban watershed characteristics on seasonal thermal responses. At the diurnal scale, daily mean WT remained strongly coupled with daily mean AT, whereas daily temperature range and peak timing showed weaker relationships with AT. The greater variability in peak WT timing at Doe Branch suggests that short-term stream thermal dynamics were influenced by additional watershed characteristics beyond atmospheric forcing alone. Full article

Reference labels for crop-type mapping are frequently coarse, and administrative land-use registries such as Japan’s eMAF (electronic Map of Agriculture and Forestry) database routinely group agronomically distinct crops under broad, ambiguous categories. This study addresses that problem for the Nakasatsunai region of Hokkaido, Japan, by combining Sentinel-1 synthetic aperture radar (SAR) time series with field-level optical vegetation-index analysis in a modular processing pipeline. The principal novelty of the work is not the pipeline architecture alone but a three-step, Normalized Difference Vegetation Index (NDVI)-driven label-refinement procedure—automatic removal of non-growing or low-amplitude field samples, Euclidean k-means subclass discovery within each coarse label, and trajectory-based label correction—that converts noisy nine-class eMAF labels into a more reliable training set prior to classifier training. The feature set combines the Radar Vegetation Index (RVI), VV and VH backscatter, the γVH/γVV polarization ratio, and NDVI, together with temporal-shape descriptors (phenological timing, peak magnitude, amplitude, maximum slope, and area under the curve) derived from monthly growth trajectories over the 2018 growing season. A Random Forest classifier, together with a gradient-boosting comparator, is evaluated before and after preprocessing under stratified k-fold cross-validation. Across n = 1208 field samples spanning the nine eMAF classes, classification accuracy improved from an overall accuracy of 71.8% on the raw labels to 82.6% after the three-step refinement; Cohen’s kappa increased from 0.63 to 0.77. Correlation analysis indicates that γVH/γVV tracks field-level NDVI more consistently (mean Pearson r = 0.68) than RVI does (mean Pearson r = 0.43) across the eight classes with sufficient samples, motivating its use as a SAR-only phenological proxy; this comparison is extended to the polarimetric PRVI, DPSVI, and DpRVI indices in the discussion. The underlying 80–90% label-accuracy estimate is derived from NDVI trajectory inspection rather than independent, field-surveyed ground truth, and a factorial ablation is used to characterize, to the extent the cross-validated evidence allows, how much of the reported accuracy gain is attributable to label-error correction as opposed to NDVI–SAR feature fusion; both this attribution and the label-accuracy estimate itself are identified as priorities for field validation in future work. The proposed framework is intended to convert coarse, noisy crop labels into a structured and reliable dataset while producing interpretable, field-level phenological insight for agricultural monitoring. Full article

Long-term chlorophyll-a (Chl-a) phenology and recurrent high-Chl-a conditions provide important evidence for identifying spatially persistent water-quality concerns in coastal bays. However, seasonally normalized screening of high-Chl-a recurrence at the sampling-cell scale remains limited for subtropical multi-bay coastlines, where regional monsoon forcing, hydrodynamic retention, riverine inputs, aquaculture, and coastal development jointly shape phytoplankton variability. Based on Copernicus Marine ocean-colour records from 2003 to 2024, this study developed a reproducible ~4 km sampling-cell framework for seven coastal bays in Fujian, China. Monthly geometric-mean climatologies, phenological metrics, P90-based high-Chl-a exceedance frequencies, monitoring-priority classes, and exploratory machine-learning diagnostics were derived. Bay-scale phenology showed clear divergence: Sansha and Xinghua Bays exhibited winter or year-end Chl-a enhancement, Xiamen Bay peaked in summer, and Quanzhou Bay reached an early-autumn maximum. Four seasonal phenological regimes further revealed cell-scale heterogeneity, with C2 representing winter-enhanced, high-amplitude cycles and C3 identifying cells with the most frequent seasonally normalized high-Chl-a exceedances. High- and moderate-priority cells were concentrated mainly in Sansha and Xinghua Bays, whereas Dongshan and Quanzhou Bays showed only localized priority cells. Exploratory diagnostics indicated that distance to the bay mouth was the most important correlate of recurrent high-Chl-a susceptibility, suggesting the role of bay-scale exchange and retention gradients. This framework converts long-term ocean-colour archives into spatially explicit phenological and anomaly-screening evidence to support targeted coastal water-quality monitoring and ecosystem management. Full article

The Tibetan Plateau ozone valley is a prominent summertime ozone minimum in the Northern Hemisphere upper troposphere–lower stratosphere (UTLS), with implications for regional radiative balance and climate. Although previous studies emphasized large-scale circulation during the Asian summer monsoon, the contributions of local topographic and thermodynamic processes remain less well quantified, in part because most analyses rely on coarse-resolution data. Here we develop a refined multi-source remote sensing framework integrating high-resolution TROPOMI observations (total column ozone, NO₂, and HCHO), Microwave Limb Sounder (MLS) ozone profiles, ERA5 reanalysis, and SRTM topography. Within a physically informed scheme, local factors are treated as pixel-level predictors and large-scale circulation as regional-mean background fields, complemented by interpretable machine-learning attribution (XGBoost-SHAP). The ozone valley exhibits a pronounced horizontal and vertical structure, with its core anomaly confined to the UTLS and spatially anchored to plateau topography. The covariability between the South Asian High (SAH) and ozone mainly reflects a shared response to thermal forcing, while circulation modulates its amplitude. Attribution shows that topography (~41%) and stratosphere–troposphere exchange (~16%) together dominate the spatial organization of the ozone minimum (~58% of the explained variance; anomaly–elevation slope −0.0035 DU m⁻¹, R² = 0.89), whereas large-scale circulation (~13%) mainly drives its seasonal amplification. Mechanistically, the elevated plateau and intense summer heating lift the tropopause, injecting ozone-poor tropospheric air into the stratospheric reservoir and thereby diluting its ozone content. Consequently, while topographic and thermodynamic factors dictate the spatial pattern of ozone, large-scale circulation primarily modulates its seasonal amplitude over complex terrain. The ozone valley thus represents a quasi-stationary climatic imprint, and our framework advances refined satellite-based atmospheric observation over complex terrain. Full article

Earthen plasters are attracting interest as low-impact, vapour-open finishing systems, yet most evidence still derives from laboratory characterization rather than from full-scale exposure. Their application in real buildings is still constrained by regulatory and material-related barriers, as national regulatory frameworks remain uneven and existing guidelines provide limited support for fibre-reinforced earthen mixtures. Moreover, natural soils vary in composition, making standardization and quality control difficult. In Mediterranean climates, vapour-open materials can support passive moisture regulation. However, seasonal changes in solar exposure and rainfall make full-scale assessment under real operating conditions necessary. This study assesses the in situ hygrothermal behaviour of an experimental circular earthen plaster, formulated with marble-processing dust and sisal fibres, against a natural hydraulic lime (NHL) reference. Two near-identical hollow-clay-block masonry test boxes were built near Catania (Southern Italy, Köppen Csa) and monitored under free-running conditions across winter, transition and summer campaigns in 2026, recording surface temperatures, indoor air temperature, relative humidity and CO₂. In winter, the earthen finish reduced the daily internal surface amplitude from 4.9 °C to 4.2 °C consistently on every paired monitoring day. During the transition period, surface differences were negligible, but relative humidity emerged as the discriminating variable, the earthen room remaining higher and more stable. In summer, the hygroscopic buffering became most evident, with the earthen room holding indoor humidity near 72% almost unchanged across a near-five-degree seasonal warming. A difference in solar absorptance between the two external finishes was identified and quantified, reducing the external surface peak of the earthen prototype by about 2 °C at maximum west-wall irradiance. The results support the use of full-scale monitoring for circular earthen plasters, advancing scientific understanding of circular earthen plasters under Mediterranean exposure and providing applied evidence for their performance-oriented use. Full article

Assessing nitrate sensitivity to hydroclimatic variability is important for evaluating water-quality vulnerability under hydroclimatic variations in coupled surface-water and groundwater systems. This study applies a hybrid, scenario-based projection framework combining a Long Short-Term Memory (LSTM) model and Weighted Regression on Time, Discharge, and Season with Projections (WRTDS-P) to examine nitrate plus nitrite responses under idealized wet and dry conditions across seven U.S. river basins and three associated groundwater wells. LSTM projections evaluate conditional sensitivity to altered precipitation forcing, while WRTDS-P projections assess discharge-conditioned responses based on empirically derived concentration–discharge relationships. Results show strong basin-scale heterogeneity in nitrate sensitivity. Agriculturally dominated Midwestern and central U.S. basins generally exhibit higher nitrate concentrations under the idealized wet scenarios, whereas basins influenced by groundwater buffering, flow regulation, or managed hydrology show weak or slightly negative wet–dry responses. For the three evaluated wells, groundwater projections show site-specific damped or delayed responses relative to nearby surface-water systems, reflecting aquifer storage and legacy nitrogen effects, although the Illinois well shows a larger projected wet–dry amplitude than the associated river. Cross-framework comparison reveals moderate agreement in response direction but notable differences in magnitude, highlighting sensitivity to model structure and forcing assumptions. These findings emphasize the value of hybrid projection frameworks for cross-framework sensitivity analysis and for interpreting nitrate vulnerability under hydroclimatic variation while accounting for uncertainty across surface-water and groundwater systems. Full article