bluuebunny/crossref_metadata_2025 huggingface dataset:
Reducing location error of legacy soil profiles leads to significant improvement in digital soil mapping
Authors: Shangguan Wei , Shi Gaosong
Published: March 2024

Digital soil mapping relies on statistical relationships between soil profile observations and environmental covariates at the sample locations. However, inherent limitations of legacy soil profiles, such as inaccurate georeferencing and inconsistent sampling techniques, frequently introduce location errors into these soil profiles that greatly affect the quality of digital soil mapping. To address this challenge, this study focuses on reducing the location error of legacy soil profiles and evaluating the resulting impact on digital soil mapping. We enhanced the consistency between environmental covariates (i.e., elevation, slope and land use) with relative high accuracy and detailed descriptive information of legacy soil profiles to reduce the location error of legacy soil profiles. We constructed quantile regression forest models to predict soil properties and their uncertainty at different depths using soil profiles before and after location error correction. Our results demonstrate that for the majority of soil variables, correcting positional errors in legacy soil profiles significantly enhances the accuracy of the digital soil mapping. The largest improvement was found for soil organic carbon at 5 cm depth, with 21% increase of   R^2. The impact of reduced location error is particularly noteworthy in regions characterized by complex terrain or sparse sampling. In addition, the accuracy and details of the predicted maps are significantly improved, which better represent the spatial variation of soil attributes across China. Besides, we also found that elevation was the primary controlling factor for correcting location error of legacy soil profiles, followed by land use and slope. This research presents a significant step towards producing high-resolution and high-quality spatial soil datasets, which can provide essential support for soil management and ensure future soil security.
Towards flood risk reduction: Commonalities and differences between urban flood resilience and risk based on a case study in the Pearl River Delta
Authors: Zheng Jiaxuan , Huang Guoru
Published: March 2024

Despite traditional measures to prevent disasters, climate change and urbanization increase flood risk. Thus, flood resilience has attracted increased global concern. Understanding the commonalities and differences between flood resilience and risk is arguably important for flood risk reduction. However, these factors have been seldom reported in previous studies, and discussions on the role of flood resilience in flood risk analysis, assessment, and management are lacking. In this study, the association between flood resilience and risk is discussed using a case study in the Pearl River Delta. Flood resilience is quantified using a pressure-state-response (PSR) model, while flood risk is assessed based on the hazard-vulnerability framework and the extension catastrophe progression method. The implications of considering flood resilience in flood risk analysis, assessment, and management are proposed. The results suggest that the overall flood resilience (risk) in the study area is greater (lower) than that in the highly urbanized areas, and areas with low (high) flood resilience (risk) are mainly concentrated within the highly urbanized areas. Indices extracted from human society and highly related to human activities have the same attributes in both frameworks, while indices associated with climate and geography contribute to the two con- cepts differently. Flood resilience supplements the concept of flood risk, and can be incorporated into risk assessment as an index. Moreover, pre-disruption (post-disaster) measures should follow flood risk (resilience) assessment, and strategies that foster flood resilience should be included in flood risk management. This study provides references for flood resilience improvement and risk mitigation.
Enhanced effects of declining precipitation on the water yield and ecosystem sustainability 
Authors: Yakir Dan , Rotenberg Eyal , Tatarinov Fyodor , Muller Jonathan
Published: March 2024

Climate change is predicted to change precipitation (P) and evapotranspiration (ET) over most land areas, imposing substantial pressure on water supply in some parts, while increasing flooding in others. Our global dataset shows that ET from ecosystems displays a conservative ‘saturation effect’ at ~460±190 mm across climates with P range of ~4000 mm. This implies that changes in P are preferentially reflected in the residual ecosystem water yield (WY=P-ET). Consequently, changes in WY are greatly enhanced compared with those in P both in observations and in model-based future projections. In drying regions, ecosystems will reach the unsustainable state of WY
Hydraulic sensitivity and stomatal regulation of two desert riparian species
Authors: Bai Yan
Published: March 2024

Characterizing plant response to water stresses is among the keys to understanding ecosystem functions. Despite increasing recognition of plant hydraulic and stomatal dynamics not captured by isohydricity, defined as the sensitivity of leaf water potential Ψl to soil water potential, it remains unclear which plant traits are critical to improved representation of plant hydraulic and stomatal dynamics beyond isohydricity, especially in dryland ecosystems. Here, we examine eco-physiological responses of two typical desert riparian species, Populus euphratica and Tamarix ramosissima, to hydro-meteorological variations. Based on measured hydraulic traits, variations of Ψl, leaf gas exchange, groundwater table, and soil moisture across vertical profiles, we investigated how subsurface hydraulic conditions control plant hydraulic sensitivity and stomatal regulation. We found both species exhibited anisohydric behaviors, which, however, were attributed to drying soil at different depths because of root distributions. The similar anisohydric behaviors also led to distinct stomatal regulation, due to the impact of atmospheric dryness decoupled from soil moisture and different sensitivities of stomatal conductance (gs) to Ψl. The latter was found to be dynamic throughout the growing season, which dominated the seasonal variation of gs and thus should not be neglected. The results suggest similar anisohydric behaviors could imply diverging hydraulic behaviors as the evaporate demand and flow regime change. Root morphological trait and stomatal sensitivity to Ψl are identified as keys to characterize responses to water stresses in desert riparian ecosystems. Our findings highlight that improved measurements and representations of these traits could contribute to better assessments of dryland ecosystem functions.
A semi-analytical method for delineating steady-state seawater-freshwater interface in three-dimensional stochastic heterogeneous confined coastal aquifers
Authors: Liu Yuxuan , Fan Bo , Zhang Jia , Lu Chunhui
Published: March 2024

Seawater intrusion threatens the freshwater resources and the ecosystem in coastal areas. Spatial heterogeneity of hydraulic conductivity is a common feature of coastal aquifers and can significantly influence the location of the seawater-freshwater interface. Conventional approaches primarily rely on numerically solving the advection-dispersion models (e.g. SEAWAT) to determine the interface in three-dimensional heterogeneous aquifers. However, these approaches are mostly computationally intensive. This study developed a semi-analytical approach for determining the location of the sharp seawater-freshwater interface, considering the steady-state seawater intrusion in three-dimensional heterogeneous confined aquifers. The approach decouples the hydraulic conductivity as a spatial variable from the conventional potential definition and defines a new potential expression. A two-dimensional partial differential equation is employed to describe the three-dimensional heterogeneous aquifer system by calculating the transmissivity above the sharp interface. Finally, the potential distribution can be obtained by solving the governing equation using finite-difference method, allowing for determining of the morphology of the sharp interface. 2D cross-sectional and 3D confined coastal aquifers with Gaussian random hydraulic conductivity fields were generated to validate our approach. The seawater-freshwater interfaces were estimated using both the semi-analytical approach and SEAWAT. Comparison analysis showed that the developed semi-analytical approach can accurately simulate the interfaces by correcting the dispersion effect. This study provides a cost-effective means for estimating the seawater-freshwater interface location in three-dimensional heterogeneous confined aquifers. It is useful for future seawater intrusion study of three-dimensional systems and for managing subsurface freshwater resources efficiently.Key Words: seawater intrusion, semi-analytical, three-dimensional, stochastic heterogeneity
Changes in Equilibrium-Line Altitude and Implications for Glacier Evolution in the Asian High Mountains in the 21st Century
Authors: Duan Keqin
Published: March 2024

In the context of global warming, glaciers in the Asian High Mountains (AHMs) are shrinking at an accelerating rate. Projecting their future change is helpful for understanding the hydrological and climatic effects related to glacier retreat. Here, we projected glacier change in the AHMs from 1979 to 2100 under shared socioeconomic pathway (SSP) scenarios from the perspective of temperature, equilibrium-line altitude (ELA), and accumulation area. The annual mean temperature in the AHMs increased by 1.26 ℃ from 1979 to 2014, corresponding to an increase of 210 m in the mean ELA and a decrease of 1.7 × 104 km2 in the glacier accumulation area. Under the SSP2-4.5 (SSP5-8.5) scenario, the annual mean temperature in the AHMs would increase by 2.84 ℃ (3.38 ℃) in 2040–2060 relative to that in 1850–1900, leading to the mean ELA reaching an elevation of 5661 m (5777 m). The accumulation area in the AHMs decreased by 46.3% from 1995 to 2014 and was projected to decrease by 60.1% in 2040–2060. Moreover, the annual mean temperature in the AHMs was projected to increase by 3.76 ℃ (6.44 ℃) in 2080-2100 relative to that in 1850-1900, corresponding to the ELA reaching an elevation of 5821 m (6245 m) and the accumulation area decreasing to 1.8 × 104 km2 (0.5 × 104 km2). These data suggest that the conditions for glacier development will disappear in most of the AHMs, except for extreme high-altitude regions in the Tianshan, Pamir, and Himalaya Mountains. Under the SSP2-4.5 (SSP5-8.5) scenario, when the global mean temperature increases 1.5 ℃ (2 ℃) above pre-industrial levels, the annual mean temperature will increase by 2.12 ℃ (2.86 ℃) and the accumulation area will decrease by 15% (48%) in the AHMs compared with that in 1995–2015. Therefore, a 1.5 ℃ increase in global warming would keep 40% more of the glacial accumulation area (1.5 × 104 km2) in the AHMs compared to a 2 ℃ increase in global warming.
Improving ambiguity resolution success rate in GNSS-based relative positioning with moving-baseline length constraint
Authors: Wu Shaoshi , Fan Bo , Ding Yishan , Jiang Zhijie , Ran Yuzhou , Cao Kaicheng
Published: March 2024

Reliable integer ambiguity resolution is the key to the global navigation satellite system (GNSS)-based precise positioning applications. In many scenarios, it is a common setup that more than one antenna is mounted on the moving platform. The integer ambiguity resolution can therefore be improved if the constant baseline information between the antennas is used reasonably. In this contribution, the baseline information, which can be measured a prior  as the constraint and has been successfully used to improve the GNSS-based attitude determination, is now extended to relative positioning. The baseline length is fully integrated into the ambiguity objective function of the relative positioning model, thus improving the reliability of relative positioning resolution. In experimental validation, both simulated and real datasets are tested to demonstrate the benefits brought by the baseline length constraint. The results show that the constraint ensures a higher ambiguity resolution success rate, and the improvement is more obvious when the observable condition is weaker.
Spring floods and their major influential factors in the source region of the Yangtze River during 2001–202
Authors: Yi Ying , Liu Shiyin , Zhu Yu , Wu Kunpeng , Xie Fuming
Published: March 2024

    Many reservoirs have been constructed in the Yangtze River basin, however, spring floods in its source region pose increasingly severe challenges to reservoirs operation and water resources management due to increased climatic variability under global warming. Understanding spring flood variability and their major influential factors under changing climates is crucial to improving water management, agricultural irrigation, reservoir operation, and flood prevention. In this study, we have examined the spring flood characteristics and their influential factors in the source region of the Yangtze River based on station data and multisource remote sensing products during 2001–2020. Late Mays have seen most of the highest spring flood discharge, while some springs have experienced multiple peaks. Extreme spring floods were identified in the years 2012, 2013, 2019, and 2020, with the highest peak discharge (1365.83 m3/s) and longest flood duration (47 days) in 2019. Spring snowmelt played a key role in 2019 spring flood and others were also driven by snowmelt in the UJSB. We defined Snow Water Volume (SWV) as an indicator of the precondition for high spring flood. In 2019, large winter SWV along with spring snowfall melted into meltwater under the rising temperature, resulting in extreme spring flood event in late April. Whereas, in 2012 and 2020, snowmelt and rainfall combined to contribute to the extreme spring flood events in late Mays. In 2013, although snowmelt made a contribution to the first spring flood peak, the flood event at the end of May was primarily contributed by rainfall. Based on spatiotemporal variations in spring SWV and the isotherm of critical temperature for snow melting, the key regions dominating spring floods were identified as the regions with large amount of SWV. Weather pattern analysis showed that the enhanced Westerly jets in winters brought about large snowfall and extended snow cover in the region which can be released as floods triggered by rapid increase in air temperature in the coming spring.
EcoPro: A Digital Twin for Ecological Projections and Environmental Assessment Using Earth Systems Models and Observations
Authors: Lee Seungwon , Kalmus Peter , Ferraz Antonio , Goodman Alex , Pearson Kyle , Doran Gary , Platt Flynn , Hu Beichen , Katugoda Ayesha , Chakraborty Sudip , Kang Emily , Zhang Jia , Dahiyat Sierra , Cavanaugh Kyle
Published: March 2024

EcoPro serves as a digital twin designed for ecological projections, aiming to forecast how ecosystems might change in response to environmental factors. It acts as a platform facilitating access to Earth Systems Model (ESM) outputs and Earth Systems observation datasets. EcoPro enables the development of an ecological model linking ecosystem predictors with environmental drivers. It further allows the downscaling of ESM model outputs to a resolution relevant to the specific ecosystem. The platform then applies the ecological model to these downscaled ESM model outputs. The results of the ecological projection are visualized at a high resolution, providing valuable information for application users and decision-makers. Additionally, EcoPro assesses the performance of new observing systems tailored for ecological projection. This discussion outlines the design and implementation of EcoPro, along with the scientific use cases studied using the digital twin.
The influence of humid heat on morbidity of megacity Shanghai in China
Authors: Liang Chen , Yuan Jiacan , Tang Xu , Kan Haidong , Cai Wenjia , Chen Jianmin
Published: March 2024

Background: Increased attention has been paid to humid-heat extremes as they are projected to increase in both frequency and intensity. However, it remains unclear how compound extremes of heat and humidity affects morbidity when the climate is projected to continue warming in the future, in particular for a megacity with a large population.Methods: We chose the Wet-Bulb Globe Temperature (WBGT) index as the metric to characterize the humid-heat exposure. The historical associations between daily outpatient visits and daily mean WBGT was established using a Distributed Lag Non-linear Model (DLNM) during the warm season (June to September) from 2013 to 2015 in Shanghai, a prominent megacity of China. Future morbidity burden related to the combined effect of high temperature and humidity were projected under four greenhouse gases (GHGs) emission scenarios (SSP126, SSP245, SSP370 and SSP585).Results: The humid-heat weather was significantly associated with a higher risk of outpatient visits in Shanghai than the high-temperature conditions. Relative to the baseline period (2010–2019), the morbidity burden due to humid-heat weather was projected to increase 4.4% (95% confidence interval (CI): 1.1% –10.1%) even under the strict emission control scenario (SSP126) by 2100. Under the high-GHGs emission scenario (SSP585), this burden was projected to be 25.4% (95% CI: 15.8% –38.4%), which is 10.1% (95% CI: 6.5% –15.8%) more than that due to high-temperature weather. Our results also indicate that humid-hot nights could cause large morbidity risks under high-GHGs emission scenarios particularly in heat-sensible diseases such as the respiratory and cardiovascular disease by the end of this century.Conclusions: Humid heat exposures significantly increased the all-cause morbidity risk in the megacity Shanghai, especially in humid-hot nights. Our findings suggest that the combined effect of elevated temperature and humidity is projected to have more substantial impact on health compared to high temperature alone in a warming climate.
Shifts in water availability due to environmental flows
Authors: Zhao Ye , Zhang Xiang , Tao Shiyong , Xiong Feng , Deng Zhimin , Bing Jianping , Yan Shaofeng , Liu Jianfeng , Xia Jun
Published: March 2024

Human society is grappling with the need to supply reliable and affordable freshwater for growing populations without destroying ecosystems. Environmental flows (EF) have been considered, and implemented, as a promising approach to sustainable water systems since its inception. However, the persistent antagonism between EF and other water demands is questionable, as the loss of hydro-ecological functions due to excessive water withdrawal (WW) could be balanced by the compensatory benefits of EF (i.e., EF improves resilience). Here, we introduce a mathematical push-pull framework to demonstrate how can EF be applied to lead to shifts in water availability explicitly in terms of magnitude and frequency. Our case study in the Yangtze River Basin reveals that EF implementation improves water availability over long time scales. We determine a boundary between EF and WW that leads to an escape from or stabilization within a stable equilibrium attraction. We use this boundary to define reasonable EF tailored to repeated, discrete WWs. Our results support the implementation of EF and its accompanying measures as part of the post-2030 eco-restoration framework.
Riverbed Sediment Topography Mapping Using UAV LiDAR and Insights into Sediment Redistribution Following an Extreme Rainfall Event and Dam Failure
Authors: Chan Yu-Chang , Sun Cheng-Wei
Published: March 2024

Accurate characterization of riverbed sediment is crucial for monitoring cross-sectional changes in rivers and modeling water dynamics, especially during large water discharge events. The UAV LiDAR technique, with recent advancements, offers enhanced capabilities for detailed riverbed topography mapping by eliminating surface vegetation. Despite its potential, the adoption of UAV LiDAR for riverbed cross-sectional profiling has faced delays and skepticism in regular practices. In this study, we applied the UAV LiDAR technique to measure the riverbed topography of a relatively wide river in the Ilan plain, northeast Taiwan. Our findings reveal that UAV LiDAR provides significantly more detailed results compared to Airborne LiDAR and surpasses topography measurements obtained through photogrammetry. The accuracy of UAV LiDAR-derived point clouds outperforms photogrammetry, especially when ground control points for the work of photogrammetry are insufficient or poorly distributed. Despite challenges posed by water bodies absorbing LiDAR signals, UAV LiDAR allows the production of complete riverbed topography, offering reliable estimates during dry seasons. Utilizing UAV LiDAR data, we conducted a comprehensive analysis of both cross-sectional and longitudinal riverbed profiles. The longitudinal profiles exhibit wavy frequencies associated with sediment transport processes, opening avenues for further investigation. Additionally, we evaluated Digital Elevation Models (DEMs) of Differencing (DoD) using previously acquired Airborne LiDAR point clouds. The DoD analysis unveiled the substantial magnitude of sediment movement and redistribution following an extreme rainfall event and dam failure, with a height difference exceeding 9m. This analysis, extending along the river's longitudinal profile, serves as a ground-truth field dataset illustrating how extreme rainfall events can trigger large sediment movements, posing potential hazards to the residents near rivers. Our study demonstrates the utility of UAV LiDAR in high-resolution mapping of riverbed sediment topography and provides valuable insights into sediment dynamics under extreme events, contributing to improved monitoring and hazard assessment practices.
Dramatic transition of abyssal oceanic carbon reservoir driven by deep ocean overturning circulation during the Cenozoic
Authors: Du Jinlong , Tian Jun
Published: March 2024

The Cenozoic era reflects a discernible global cooling trend attributed to the prolonged decrease in atmospheric pCO2. Various theories have been proposed to elucidate the mechanisms behind this reduction, with a focus on the substantial carbon exchange between the atmosphere and the global ocean. However, the carbon storage dynamics in the abyssal ocean during the geological past remain enigmatic. Employing a state-of-the-art ocean-biogeochemical model and leveraging recently published paleoceanographic records, this study unveils distinct basin-scale carbon storage patterns in the Pacific and Atlantic in a hypothetical no-Tibetan-Plateau scenario. Through sensitivity experiments, our findings suggest that orographic forcing, specifically the absence of the Tibetan Plateau, may have triggered a significant carbon transition from the Atlantic to the Pacific. This transition appears to be driven by a substantial reorganization of deep ocean overturning circulation. Importantly, this observed phenomenon could be a contributing factor to the long-term reduction in atmospheric pCO2.
Under-Dip Toppling in the Outer Western Carpathians: Insight into Investigation of Slope Failures and Implication of Paleo-Seismic Activity
Authors: Nguyễn Thanh-Tùng , Baroň Ivo , Dong Jia-Jyun , Melichar Rostislav , Hartvich Filip , Klimeš Jan , Černý Jan , Šutjak Martin , Kociánová Lenka , Dušek Václav , Rowberry Matt , Braucher Régis , Tomasz Goslar , Hu Jyr-Ching , Tseng Chia-Han , Chen Yi-Chin , Lin Cheng-Han
Published: March 2024

The Outer Western Carpathians, situated in the central European segment of the Alpine-Himalayan orogenic zone, present an intriguing case of an accretionary wedge. This region is characterized by Mesozoic and Cenozoic flysch sedimentary rocks, comprising massive sandstone benches and intercalated clay layers. These formations have undergone significant deformation, including being thrust over the European foreland during the Paleogene and Neogene periods. The resulting hilly to mountainous terrain exhibits notable slope failures. Here we focused on the phenomenon of under-dip toppling –sandstone beds steeply dipping in the direction of the slope, which were locally overturned along systems of brittle fractures. Utilizing high-resolution LiDAR data, our study investigates the locations, geometrical characteristics, and tectonic settings of these toppling. In the Javorníky Mountains, these topples predominantly occur in SSE-dipping fold limbs, an orientation conducive to under-dip toppling. The mechanism of under-dip toppling, involving the lifting of the center of gravity of the toppled layers, presents a complex geomechanical challenge. Recent field investigations, including structural measurements on faults, electrical resistivity tomography (ERT) profiles, and 10Be dating, have identified active polyphase strike-slip surface ruptures in the region. These findings raise questions about the origins of toppling and their implications for understanding paleo-earthquakes in the area. Our preliminary analysis suggests a two-tiered approach to understanding toppling processes: firstly, exploring the deeper structural implications – could active tectonic faulting be the cause of the under-dip toppling? Secondly, we analyzed the mechanism of toppling near to the surface. By analyzing the geometry of near-surface persistent sandstone slabs and employing Pseudo-static analysis to assess seismic slope response, our results indicate that the layer while overturned may be attributed to strong paleo-seismic events. This study employs comprehensive site investigations and back analyses to understand a range of possible trigger and controlling mechanisms. It elucidates the geological conditions of slopes and performs a geomechanical analysis of under-dip toppling.The research is part of the international bi-lateral project “Earthquake triggered landslides in recently active and stabilized accretionary wedges”, supported by the Czech Science Foundation (GAČR 22-24206J) and the Taiwanese Ministry of Science and Technology (NTSC 111-2923-M-008-006-MY3).
Climate factors control inter-annual variability of radial growth, while microsite conditions affect absolute growth and long-term growth trend in the multi-stemmed shrub Alnus alnobetula at the alpine treeline
Authors: Oberhuber Walter , Gruber Andreas , Wieser Gerhard
Published: March 2024

Green alder (Alnus alnobetula (Ehrh.) K. Koch = Alnus viridis (Chaix) DC), a tall multi-stemmed deciduous shrub, is widespread at high elevations in the Central European Alps especially within avalanche slide path, screes and steep, north-facing slopes with high water availability. The ascending growth of stems frequently leads to eccentric growth, discontinuous rings and elliptical shape of annual rings making development of representative ring-width time series, necessary to determine climate forcing of radial growth and long-term growth trends, a challenge. Therefore, the focus of this study was to assess growth variability among radii of one shoot (n=4 radii), among shoots belonging to one stock (n=20 shoots per stock) and among stocks exposed to different site conditions (n=3 sites). Stem discs were sampled within the treeline ecotone (c. 2150 m asl) on Mt. Patscherkofel (Tyrol, Austria), and annual increments were measured along 188 radii. Variability in inter-annual agreement among ring-width series was evaluated by applying dendrochronological techniques, i.e., the parameters (i) percentage of parallel variation (“Gleichläufigkeit”, Glk) and (ii) the correlation coefficient r, adjusted for the amount of overlap (tBP-score) were determined. Variation in intra-annual dynamics of radial growth among shoots belonging to different stocks was evaluated by mounting diameter dendrometers (n=6). Results revealed a high agreement in ring-width variation among radii of one shoot (Glk: P5), among shoots of one stock (Glk: P4) and among stocks from different sites (Glk: P
A tipping point in the contribution of extratropical cyclones to Antarctic surface mass balance
Authors: Xu Dongze , Lin Yanluan
Published: March 2024

Extratropical cyclone (EC) is a main source of precipitation at midlatitudes, but its contribution to the Antarctic surface mass balance (SMB) still remains uncertain. Based on five global climate model simulations, we propose that it probably exists a tipping point of the SMB during the evolution of the Antarctic Ice Sheet (AIS), and EC greatly contributes to the tipping point. Before the tipping point, decreasing elevation of the AIS and warming sea surface temperature promote southward movement of ECs, leading to increased precipitation and inhibiting the AIS melting. However, EC becomes a negative contribution to SMB due to increased AIS surface temperature, runoff and rainfall. This study highlights that EC contributes to the tipping point of the AIS evolution.
A North Atlantic Ocean-originated mode of the AMOC multicentennial variability
Authors: Yang Kunpeng , Yang Haijun , Liu Mengyu
Published: March 2024

A multicentennial oscillation (MCO) of the Atlantic meridional overturning circulation (AMOC) is exhibited in a CESM1 control simulation. It primarily arises from internal oceanic processes in the North Atlantic, potentially representing a North Atlantic Ocean-originated mode of AMOC multicentennial variability (MCV) in reality. Specifically, this AMOC MCO is mainly driven by salinity variation in the subpolar upper North Atlantic, which dominates local density variation. Salinity anomaly in the subpolar upper ocean is enhanced by the well-known positive salinity advection feedback that is realized through anomalous advection in the subtropical-subpolar upper ocean. Meanwhile, mean advection moves salinity anomaly in the subtropical intermediate ocean northward, weakening the subpolar upper salinity anomaly and leading to its phase change. This mechanism aligns with a theoretical model we proposed earlier. In this theoretical model, artificially deactivating either the anomalous or mean advection in the AMOC upper branch prevents it from exhibiting AMOC MCO, underscoring the indispensability of both the anomalous and mean advections in this North Atlantic Ocean-originated AMOC MCO. In our coupled model simulation, the South Atlantic and Southern Ocean do not exhibit variabilities synchronous with the AMOC MCO; the Arctic Ocean’s contribution to the subpolar upper salinity anomaly is much weaker than the North Atlantic. Hence, this North Atlantic Ocean-originated AMOC MCO is distinct from the previously proposed Southern Ocean-originated and Arctic Ocean-originated AMOC MCOs. 
Automated glacier extraction using a Transformer based deep learning approach from multi-sensor remote sensing imagery
Authors: Peng Yanfei , He Jiang , Yuan Qiangqiang , Wang Shouxing , Chu Xinde , Zhang Liangpei
Published: March 2024

Glaciers serve as sensitive indicators of climate change, making accurate glacier boundary delineation crucial for understanding their response to environmental and local factors. However, traditional semi-automatic remote sensing methods for glacier extraction lack precision and fail to fully leverage multi-source data. In this study, we propose a Transformer-based deep learning approach to address these limitations. Our method employs a U-Net architecture with a Local-Global Transformer (LGT) encoder and multiple Local-Global CNN Blocks (LGCB) in the decoder. The model design aims to integrate both global and local information. Training data for the model were generated using Sentinel-1 Synthetic Aperture Radar (SAR) data, Sentinel-2 multispectral data, High Mountain Asia (HMA) Digital Elevation Model (DEM), and Shuttle Radar Topography Mission(SRTM) DEM. The ground truth was obtained for a glaciated area of 1498.06 km2 in the Qilian mountains using classic band ratio and manual delineation based on 2 m resolution GaoFen (GF) imagery. A series of experiments including the comparison between different models, model modules and data combinations were conducted to evaluate the model accuracy. The best overall accuracy achieved was 0.972. Additionally, our findings highlight the significant contribution of Sentinel-2 data to glacier extraction.
Foreland basin development in response to Proto-Tethyan Ocean closure, western North China Block
Authors: Sun Jiaopeng , Dong Yunpeng
Published: March 2024

Closure timing of the northeastern Proto-Tethys between the Qilian/Qinling terranes and the North China Block remains unsolved, with assumptions ranging from end-Ordovician to the Devonian. To address this issue, integrated studies of stratigraphy and geochronology were conducted on Late Ordovician strata in the southwestern Ordos, which recorded earliest tectonic transition from passive margin to foreland basin in the westernmost North China Block. Stratigraphic and paleontologic syntheses demonstrate that pre-Katian strata are shallow-marine deposits dominated by benthonic faunas. While, Katian successions above a paraconformity are characterized by deep-water debrites and turbidites containing abundant planktonic graptolites. Provenance analysis reveals an evolving source from the North China Block basement to the Qilian/Qinling arc terranes at the beginning of Katian (ca. 450 Ma). Detrital zircons from pre-Katian quartz arenites yield ages of ca. 1600–2800 Ma, significantly older than their depositional timing. In contrast, Katian turbidites in the southwestern Ordos and the North Qilian Orogen display similar age patterns dominated by ca. 450–900 Ma ages. These clues imply a basin-filling shift from passive margin to underfilled foreland, separated by forebulge unconformity formation at Sandbian/Katian boundary. Stratigraphic correlation further suggests that sequence of foreland basin-infill transitions was broadly simultaneous along-strike over ~1200 km across the southwestern North China Block, including forebulge flexural uplift, followed by rapid shallow shelf drowning to abyssal plain, until arrival and superimposition of arc-derived turbidites. Along-strike synchronicity of orogenic activities implies that closure of the northeastern Proto-Tethys was nearly synchronous. The L-shaped orogen-parallel foreland encompassing the southwestern North China Block unveils oroclinal bending of the Qilian/Qinling collision belt, which still dominates geology of the present northeastern Tibet. Our new insights provide a stratigraphic constraint for the timing and mode of the initial elimination of northeastern Proto-Tethys.
Precipitation forecast post-processing: blending deterministic NWPs with machine learning
Authors: Monaco Luca , Cremonini Roberto , Laio Francesco
Published: March 2024

Direct model output forecasts by Numerical Weather Prediction models (NWPs) present some limitations caused by errors mostly due to sensitivity to initial conditions, sensitivity to boundary conditions and deficiencies in parametrization schemes (i.e. orography).These sources of error are unavoidable, and atmosphere chaotic dynamics makes prediction errors to spread rapidly in time in the course of the forecast, inducing both systematic and random errors.Nonetheless, in the last 50 years NWPs had a significant decrease in the impact of these source of errors, even in the long-term forecast, thanks for instance to an ever-increasing computational capability, but still their relevance is not neglectable.Moreover, different NWPs present specific different pros and cons which are findable empirically. For instance, in the case of precipitation forecast in the north-west Italy, low spatial resolution models (e.g. ECMWF-IFS) tend to be more reliable in terms of space and time in predicting the average precipitation, while high resolution models (e.g. COSMO-2I) tend to forecasts the maximum precipitation better. Research purposes apart, actual limitations must be seen in an operational context, where weather forecasts’ skillfulness and associated uncertainty are information of the utmost importance to the forecaster and in general to the user of a certain forecasts system.In order to tackle the limitations of NWPs and the need of an uncertainty-quantified meteorological forecast, we propose a machine learning based multimodel post-processing technique for precipitation forecast. We focus on precipitation since it is the most important variable in the issue of spatially localized weather alert notice by the Italian Civil Protection’ system and at the same time it is one of the most challenging variables to forecast.We use different Convolutional Neural Networks (CNNs) to obtain both deterministic and probabilistic forecast grids over 24h up to 48h focusing in the North-West Italy, using different high and low resolution deterministic NWPs as input and using high resolution rain-gauge corrected radar observations as ground truth for the training. We use constrainted linear regressions as a mean of deterministic benchmark, and ECMWF-EPS as a mean of probabilistic benchmark. The test phase show decent improvements in terms of RMSE for every season.
Latest developments of the Aerosol Layer Height retrieval from S5P/TROPOMI
Authors: de Graaf Martin , Sneep Maarten , Tilstra Gijsbert , ter Linden Mark , Veefkind Pepijn
Published: March 2024

The height of aerosols is important for many applications, such as the Earth’s radiation budget, transport of aerosols, aviation, retrieval of aerosol optical thickness and the atmospheric correction. Active instruments, such as the lidars on Caliop and Aeolus have provided important insight in the vertical distribution of aerosols, but these missions had a small spatial coverage and have now ended. EarthCare will provide an important replacements for these instruments, but the daily, global coverage provided by passive instruments, such as TROPOMI, remains essential.In 2019, the first operational, global Aerosol Layer Height (ALH) product was released, retrieved from near-infrared measurements by TROPOMI on Sentinel-5P.  The operational algorithm uses a machine learning technique in the forward model, to quickly and accurately simulate the around 4000 spectral absorption lines in the O2-A band around 760 nm, and the inversion problem is solved iteratively using an optimal estimation routine, in order to have a proper error estimation.Since its release, many important improvement have been implemented. First focused on single, selected layers of absorbing aerosols, the processor now provides the ALH for all cloud-free scenes, including scattering aerosol layers. The algorithm performs well over oceans (within the 1 km accuracy requirement) but not over land surfaces. The surface albedo is an important error source, especially over bright surfaces and for thin aerosol layers. In order to improve the retrieval over land, the surface albedo can be fitted, yielding highly improved results. However, for the operational processor this required the retraining of the neural network, since the derivatives to the fit parameters are needed in the optimal estimation routine. Therefore, the derivatives to surface albedo at two wavelengths in the continuum (outside the  O2-A band) were added to the algorithm forward model. This yielded improved accuracy over land and a large increase in the number of successful retrievals. The latest version of the S5P/TROPOMI ALH (version 2.6.0, including all these improvements and the surface fit) was released in November 2023. We will present the algorithm and the latest validation results, including ALH estimates from various instruments in space and from ground-based lidar networks. The TROPOMI ALH algorithm is developed and maintained within the EU Copernicus program. Its developments are important for Sentinel-3 OLCI, for which a similar O2-A band retrieval is being developed, and the upcoming geostationary mission Sentinel-4 and the successor missions for S5-precursor (Sentinel-5), which will also have a similar ALH product. 
Multivariate state and parameter estimation using data assimilation in a Maxwell-Elasto-Brittle sea ice model
Authors: Chen Yumeng , Smith Polly , Carrassi Alberto , Pasmans Ivo , Bertino Laurent , Bocquet Marc , Finn Tobias Sebastian , Rampal Pierre , Dansereau Véronique
Published: March 2024

In an idealised setup, a dynamics-only sea ice model is used to investigate the fully multivariate state and parameter estimations that uses a novel Maxwell-Elasto-Brittle (MEB) sea ice rheology. In the fully multivariate state estimation, the level of damage, internal stress and cohesion are estimated along with the observed sea ice concentration, thickness and velocity. In the case of parameter estimation, we estimate the air drag coefficient and the damage parameter of the MEB model. The air drag coefficients adjust the strength of the forcing on the sea ice dynamics while the damage parameter controls the mechanical behaviour of the internal property of sea ice. We show that, with the current observation network, it is possible to improve all model state forecast and the parameter accuracy using data assimilation approaches even though problems could arise in such an idealised setup where the external forcing dominates the model forecast error growth.
Asphalt Concrete Density’s Monitoring during Construction
Authors: Abufares Lama , Al-Qadi Imad
Published: March 2024

Over the past three decades, GPR has been implemented for various applications in civil engineering infrastructure, including predicting in-situ density of AC pavements. Given the sensitivity of asphalt concrete (AC) layer density to compaction effort during construction, real-time AC density monitoring is invaluable. Unlike traditional approaches that estimate in-situ AC density (e.g., extracted cores and nuclear gauge measurements), ground penetrating radar (GPR) technology may be used for real-time prediction of AC density, allowing modification of compaction pattern and effort on the fly. A new GPR mount prototype was designed, allowing direct installation on various roller compactor types. The design was field validated.Electromagnetic mixing theory is used, and bulk AC dielectric constant is related to its components’ dielectric constants and their corresponding volumetric proportions. The AC volumetrics could be determined from the job mix formula. The relative dielectric constants of binder and air are known to be approximately 3 and 1, respectively. However, cores are usually required to back-calculate the aggregates’ dielectric constant, which depends on aggregate minerology. In this study, aggregate dielectric constant values were used from an established aggregate dielectric constant database for Illinois.Six stone matrix asphalt (SMA) test sections were constructed using different aggregate types at the Illinois Center for Transportation. GPR data were collected for each roller pass during compacting the test sections. An automated density prediction tool was developed to provide the roller operator with real-time prediction of the AC density. The AC predicted densities were compared to values obtained from nuclear gauge measurements and extracted cores densities. The GPR-predicted AC densities were better correlated to ground truth core densities than those by a nuclear gauge. In addition to ensuring AC quality when the introduced system is used, cost savings and emission reduction could be realized when compaction effort is optimized. 
Titan in Late Northern Summer from JWST and Keck Observations
Authors: Nixon Conor , Bézard Bruno , Cornet Thomas , Coy Brandon , de Pater Imke , Es-Sayeh Maël , Hammel Heidi , Lellouch Emmanuel , Lora Juan , Lombardo Nicholas , López-Puertas Manuel , Rannou Pascal , Rodriguez Sébastien , Teanby Nicholas , Turtle Elizabeth ,   Titan JWST and Keck Observation Team
Published: March 2024

Titan is an object of fascination for scientists researching the solar system, as a ‘terrestrial-like’ world with active meteorology and fluvial and lacustrine formations based on methane chemistry and condensation. The Cassini-Huygens mission explored Titan extensively from 2004 to 2017, but since that time further observation of its slow seasonal cycle has been possible only via telescopes positioned on or close to the Earth. Titan’s unique characteristics led to a concerted post-Cassini observational campaign, with many of the most powerful telescopes available to astronomy. In this work we report on observations from 2022 & 2023 with three instruments on the James Webb Space Telescope (JWST), NIRCam, NIRSpec and MIRI, also in coordination with imaging from Keck II. In November 2022 and July 2023, Titan was the subject of multi-spectral filter imaging with JWST NIRCam and Keck II NIRC2, revealing tropospheric clouds at mid-northern latitudes, in line with climate modeling predictions for this season (late northern summer). In filters sensitive to the upper troposphere, we observed clouds growing and apparently ascending in altitude during a Titan day. JWST NIRSpec spectroscopy yielded for the first time a high resolution (R=2700) spectrum of Titan across the entire near-infrared (1-5 microns) unobscured by telluric absorption. This, among other things, enabled measuring the detailed structure of the CO 4.7 micron non-LTE emission, including the fundamental, the first two overtone bands and two isotopic bands. It is also the first time that CO2 emission has been resolved in the NIR and the first time it has been seen on Titan’s dayside.  Finally, very sensitive spectroscopy with JWST MIRI in the mid infrared (5-28 microns) confirmed the many stratospheric gases seen by Cassini CIRS, but also added a new detection of methyl (CH3) in the middle atmosphere, a product of methane photochemistry that was expected but not previously seen. We modeled parts of the spectra to find a global mean temperature profile and profiles of minor gases. Soon we hope to extract yet more results from the NIRSpec and MIRI spectra as our understanding of the calibration and modeling progresses. In this presentation we summarize our results to date and describe planned future observations of Titan with JWST and Keck cycles.
Unveiling the characteristics of ZVI-AC-sand mixtures in remediating contaminated groundwater using spectral induced polarization
Authors: Mao Deqiang , Ma Xinmin , Furman Alex , Schwartz Nimrod , Chao Chen , Xia Teng , Yang Kai , Guan Xiaolei
Published: March 2024

The long-term performance of the permeable reactive barriers in remediating contaminated groundwater may diminish as a result of oxidation, precipitation on the particle surfaces, and pore space clogging. Evaluating its performance through monitoring could address this dilemma. We investigate the spectral induced polarization (SIP) response of zero valent iron (ZVI)-activated carbon (AC)-sand mixtures.The chargeablity exhibits a perfect linear relation to the volumetric concentration of ZVI (2.5-50%) and AC (2.5%-75%) with r = 0.99. However, the low-frequency electrical conductivity shows low sensitivity to the volumetric content of ZVI and AC. The relaxation time increases with the particle sizes. When these two particles are mixed, chargeablity is approximated as a superposition of their individual values. In terms of phase values and frequencies of the phase peaks, it also exhibits this superposition effect. Furthermore, we conducted 720-hour SIP measurements on ZVI-AC-sand columns flushed with NaCl or NaNO3 solutions. It suggests that precipitation of 0.06 mm thick sedimentation onto the ZVI surface induced by changes in redox chemistry observed in micromorphology images, resulting an increase in the normalized chargeability by 44.05%, the scaled relaxation time and Cole–Cole model exponent by 1098.99% and 23.11%. Compared to flow-through by NaCl solution, changes in these parameters are more pronounced for columns saturated with NaNO3 solution, indicating the corrosion of ZVI. Our findings illustrate that induced polarization parameters vary in response to the chemical alteration of ZVI-AC-sand mixed media, showing the potential for noninvasive long-term monitoring of the reactive barriers.