bluuebunny/crossref_metadata_2025 huggingface dataset:
Global dryness could intensify vegetation failure even after net-negative emission is achieved
Authors: Mondal Sanjit Kumar , An Soon-Il , Min Seung-Ki , Jiang Tong , Su Buda , Paik Seungmok , Kim Soong-Ki
Published: March 2024

The response of global dryness and vegetation to CO2 removal experiments, especially for net- negative emission is immature. Here we conducted a thorough investigation to identify hysteresis and reversibility in global dryness, as well as the vegetation productivity’s response to dry and wet episodes, considering their asymmetrical nature. The asymmetry index (AI) includes two important aspects such as positive AI indicates a dominant increase of vegetation productivity during wet episodes compared to the decline in dry episodes and negative AI implies a larger reduction of productivity in dry years compared to an increase in wet years. Aggregate results from various drought indices and vegetation productivity reveal a dominant dryness in the CO2 decrease phase. Global dryness shows strong hysteresis and irreversible behavior over half of the global land with significant regional disparity. Irreversible changes in dryness are concentrated in specific areas, i.e., hotspots, covering over 14% of the global land, particularly pronounced in Northern Africa, Southwest Russia, and Central America. Moreover, a wider spread of negative asymmetry indicates a significant decrease in vegetation productivity caused by dryness. Importantly, the potential evapotranspiration is projected to be the primary driver of global dryness as well as vegetation asymmetry. Our findings suggest only CO2 alleviation is not enough to cope with drought rather implementing advanced water management strategies is a must to mitigate the impact of drought effectively.
Unexpected HCHO transnational transport: Influence on the temporal and spatial distribution of HCHO in Tibet from 2013 to 2021 based on satellite
Authors: Xu YiZhou , Su WenJing , Liu Cheng
Published: March 2024

Formaldehyde (HCHO) is a toxic and harmful air pollutant to humans, animals, and plants and is an essential precursor of PM2.5 and ozone compound pollution. Few studies have focused on HCHO in Tibet, the third pole with a unique ecosystem that requires protection. Here, we investigate the spatial-temporal distribution of HCHO from 2013 to 2021 and its influencing factors from satellite observations in Tibet. We found that the average HCHO VCD in Tibet presents a significant annual growth rate of 2.25%/yr, which is similar to that in India and even higher than that in most of the world, including eastern China. Moreover, HCHO VCD in the eastern region of Tibet shows no seasonal pattern, unlike other areas. The anomalous variation in HCHO concentrations in Tibet is primarily attributed to long-distance transnational transport from incomplete combustion in India Assam. Our results help strengthen concerns about atmospheric environmental management in Tibet.
Effects of hydrologic conditions on systematic incremental benefits of basin-wide cooperation of cascade reservoirs in the Yellow River Basin
Authors: Tang Fengzhen , Wang Yuanjian
Published: March 2024

The complicated relationship between water and sediment in the Yellow River Basin (YRB) makes it imperative for reservoir stakeholders to game with each other to balance the short-term and long-term benefits. Basin-wide cooperation could bring the most benefits to the major reservoir stakeholders, engaged with the Longyangxia, Liujiaxia, Wanjiazhai, Sanmenxia, and Xiaolangdi reservoirs on the YRB mainstream. The systematic incremental benefits of grand cooperation based on the historical streamflow in 2006-2019 are all positive, ranging from $15.44 to $44.55 million per year. With different streamflow and sediment conditions, the systematic incremental benefits of grand cooperation vary for different years, implying that basin-scale grand cooperation is always beneficial, but the benefits are impacted by hydrologic conditions. The systematic incremental benefit is larger when the YRB is dryer and sediment concentration is higher. Basin-wide cooperation is especially beneficial when the inflow peak comes earlier and the streamflow process is more fluctuating.
A one-dimensional urban flow model with an Eddy-diffusivity Mass-flux (EDMF) scheme and refined turbulent transport (MLUCM v3.0)
Authors: Lu Jiachen , Nazarian Negin , Hart Melissa , Krayenhoff Scott
Published: March 2024

In recent years, urban canopy models (UCMs) have been used as fully coupled components of mesoscale atmospheric models as well as offline tools to estimate temperature and surface fluxes using atmospheric forcings. Examples include multi-layer urban canopy models (MLUCMs), where the vertical variability of turbulent fluxes is calculated by solving prognostic momentum and turbulent kinetic energy (TKE, $k$) equations using length scale ($l$) and drag parameterizations. These parameterizations are based on the well-established 1.5-order $k-l$ turbulence closure theory and are often informed by microscale fluid dynamics simulations. However, this approach can include simplifications such as the assumption of the same diffusion coefficient for momentum, TKE, and scalars. In addition, the dispersive stresses arising from spatially-averaged flow properties have been parameterized together with the turbulent fluxes while being controlled by different mechanisms. Both of these assumptions impact the quantification of turbulent exchange of flow properties and subsequent air temperature prediction in urban canopies. To assess these assumptions and improve corresponding parameterization, we conducted 49 large-eddy simulations (LES) for idealized urban arrays, encompassing variable building height distributions and a comprehensive range of urban densities ($\lambda_p\in[0.0625,0.64]$) seen in global cities. We find that the efficiency of turbulent transport (numerically described via diffusion coefficients) is similar for scalars and momentum but 3.5 times higher for TKE. Additionally, the parameterization of the dispersive momentum flux using the $k-l$ closure was a source of error, while scaling with the pressure gradient and urban morphological parameters appears more appropriate. In response to these findings, we propose two changes to MLUCM v2.0: (a) separate characterization for turbulent diffusion coefficient for momentum and TKE; and (b) introduction of an explicit physics-based "mass flux" term to represent the non-Gaussian component of the dispersive momentum transport as an amendment to the existing "eddy diffusivity" framework. The updated one-dimensional model, after being tuned for building height variability, is further compared against the original LES results and demonstrates improved performance in predicting vertical turbulent exchange in urban canopies.
Plastic pollution in deep seafloor of the South China Sea
Authors: Dasgupta Shamik , Peng Xiaotong , Xu Hongzhou , Wang Dawei , Xu Hengchao , Ta Kaiwen , Song Xikun , Du Mengran
Published: March 2024

Plastic pollution is at the forefront of environmental problems, and has invaded every sphere on Earth. We describe the abundance, distribution, transport pathways and mechanisms, fate and ecological impacts of plastics in the South China Sea (SCS), emphasizing on the deep seafloor microplastics and plastics. We document presence of plastics, primarily based on more than 100 dives in manned submersibles, backed-up by in-depth analysis of dive track videos and images from all locations, providing the first distribution maps of microplastic and plastics on the bottom of the SCS. Abundance of large plastics have been observed to be highest at typical V-shaped geomorphological units, such as canyons, where hydrodynamic conditions are stronger. However, high concentrations of microplastics occur commonly in the sediments of coastal zones. Sources and transportation mechanism of microplastics and plastics in the SCS are thus distinctly different from each other. While a vast majority of microplastics is possibly transported through riverine inputs, most of plastics have a sea-based origin and are discarded from fishing boats, entertainment vessels, and merchant ships. Apart from surface currents, deep-water, seasonal currents, as well as gravity flow, facilitate the transport of marine plastics to deep seafloor sediments. We present two types of models for the transportation of microplastics and plastics in SCS, respectively. We further elucidate the ecosystem which has emerged as a new hot spot with the plastics in SCS. Both large plastics and microplastics additionally act as vectors of chemical pollutants, resulting in ecotoxicological damages. Interaction of biota with deep-sea plastics has been observed and documented in terms of ingestion, entanglement, or proximity, resulting in potential negative effects. The extent of plastic pollution in the SCS is at an alarming level. Therefore, strengthened mitigation procedures, reuse and recycling structures, and waste water management have to be urgently incorporated in National Action Plans to control the burden of plastics entering the SCS. 
Global coupling coordination and interactions between diet, environment, and human health
Authors: Li Meng , Zhuo La , Wu Pute
Published: March 2024

Diet choices and changes are closely linked to environment sustainability and human health. However, a quantitive evaluation of coupling coordination and interactions between diet, environment and human health is still lacking. Here we mapped global coupling coordination degree (CCD) of diet related to 95 food products and associated environmental and health impacts across 175 countries and regions from 2010 to 2020. Results show that global dietary development lags behind environmental and health development with 162 countries having a moderate CCD. Most countries experience environmental degradation while promoting dietary and health systems. Visible trade-offs between food-related water footprints, land footprints, and greenhouse gas emissions exist in space and time. Increasing vegetable and fish intake in China only contribute 228.7% to the reduction in diet-related deaths globally. This analysis provides an efficient approach for measuring the strong coupling between diet, environment, and health systems and subsystems towards their mutual coordination and sustainability.
Vertebrate Biogeography of the Late Cretaceous (Cenomanian-Maastrichtian) Western Interior Seaway of North America by Percent Community Similarity with the Faunal Assemblages of south-central Canada
Authors: Kilmury Aaron
Published: March 2024

Community zonation of the Late Cretaceous Western Interior Seaway (WIS) of North America has been suggested for bivalves, cephalopods, foraminifera, gastropods, and tetrapods. Most proposed WIS community zones consist of a northern and southern subprovince with a gradational boundary in central or south-central North America. Since it has been over three decades since the WIS community zonation hypothesis has been investigated for vertebrates, new information including recent radiometric age determinations, taxonomic revisions, additional fossil discoveries, and recently available online museum specimen catalogues allow for testing of the community zonation hypothesis using an updated dataset. Community percent similarities were calculated between time-averaged, lithostratigraphic unit faunal assemblages of the Manitoba escarpment and other WIS localities using Percent Similarity coefficients calculated from relative abundance data as well as Sorensen’s Coefficients of Communities calculated from presence-absence data on the generic and species levels for comparisons. Additionally, nine time bins were used to represent nine Upper Cretaceous lithostratigraphic units of the Manitoba escarpment to test the zonation hypothesis consistency for nearly the entire Late Cretaceous time interval (~71-95 Ma). Relatively high genus-level community similarity values (25-50%) of south-central WIS localities and low values (
Application of Multi-mission Satellite Remote Sensing Data for Land Surface Data Assimilation
Authors: Khaki Mehdi
Published: March 2024

The abundance of satellite remotely sensed data in the past few decades has provided a great opportunity to improve land surface models. This study aims to apply terrestrial water storage (TWS) estimated from the Gravity Recovery And Climate Experiment (GRACE) mission as well as soil moisture from Soil Moisture and Ocean Salinity Mission (SMOS) and Advanced Microwave Scanning Radiometer Earth Observing System (AMSR-E) to calibrate a land surface model via data assimilation. This is done using a dual scheme to separately update the state and parameters using two interactive ensemble Kalman filters (EnKFs).  The performance of multivariate data assimilation is evaluated against various independent data over different time periods and different basins. According to the evaluation of the results against independent measurements, it is found that the calibrated model parameters lead to better model simulations both in the calibration and forecasting period. The proposed approach also offers better performance in capturing high-frequency water storage variations imposed by climatic events at various spatiotemporal scales.
Weak Anatolian upper mantle inferred from postseismic deformation of the 2023 Türkiye earthquake doublet
Authors: Wang Kai , Hu Yan
Published: March 2024

The eastern Mediterranean hosts complex tectonic units with multiple strike-slip and collision plate boundaries. The Anatolian plate is being pushed away from the Eurasian plate and Arabian plate via two left-lateral transform faults with uncoupled crust and upper mantle inferred from anisotropy studies. The rheological structure is thus important to better understand the plate dynamics of the Anatolian and its surrounding plates. The 2023 Mw7.8 and Mw7.6 earthquake doublet in the East Anatolian Fault zone provides a unique opportunity to study viscoelastic relaxation of the upper mantle and time-dependent afterslip over the crustal faults. Here we have derived the first 3-month postseismic displacements from GNSS time series of 94 stations after the events to investigate the early postseismic deformation processes through a three-dimensional viscoelastic finite element model. Afterslip in the model is simulated through a 2-km thick weak shear zone attached to the fault. Viscoelastic relaxation is represented by the bi-viscous Burgers rheology. We find that the observed long-wavelength displacements is dominated by the viscoelastic relaxation even in this early postseismic stage, and the contribution from the afterslip is spatially limited. The viscosity of the Anatolian upper mantle should be lower than 1019 Pa s to better fit the observed horizontal and vertical displacements. This inferred weak upper mantle may result from the upwelling mantle due to the tearing African slab.
Satellite-Based Inundation Modelling for Large-Scale Wetland Restoration in Semi-Arid Australia
Authors: Kreibich Jan , Bino Gilad , Glamore William , Kingsford Richard
Published: March 2024

Wetlands, among the world’s most biodiverse and productive ecosystems, face severe threats from flow regime alterations, unsustainable water management, land-use conversion, increasingly exacerbated by climate change. Reduced connectivity between river channels and their floodplain habitats is often a consequence of subsequent drying, significantly degrading ecological health. We investigated the impacts of a century of river regulation and upstream water abstractions on the Lowbidgee Floodplain in semi-arid Australia - a nationally important wetland ecosystem on the lower Murrumbidgee River within the Murray-Darling Basin. This floodplain, which includes the indigenous-managed Gayini Wetlands and Yanga National Park, has a rich Aboriginal cultural heritage and supports a range of threatened and endangered native Australian species. We utilized Landsat and Sentinel satellite data to map wetland inundation patterns from 1988 to the present. Through the analysis of discharge data from the floodplain’s river gauges, we modelled the extent and frequency of wetland inundation under variable water availability scenarios, resulting from river regulation and climate change. Additionally, we evaluated the effects of altered flow and flood regimes on the health of flood-dependent vegetation, using remote sensing-derived vegetation indices such as the NDVI and Fractional Vegetation Cover (FVC). Our study aims to inform environmental flow management for large-scale river and wetland restoration efforts. It also provides the indigenous landowners, the Nari Nari Tribal Council, with crucial data to support their land and water management.
Dynamic responses of a building derived from microtremor and seismic signals
Authors: Rau Ruey-Juin , Wu Cheng-Feng , Chen Ying-Chi , Wu Hung-Yu , Lin Chin-Jen
Published: March 2024

We used the liquid-based R2 rotational seismometer in addition to several arrays of translation velocity seismometers on a 12-floor building in the National Cheng Kung University campus to evaluate the dynamic responses of the structure. During the observation period in August-October 2023, we encountered a moderate M 5.6 earthquake sequence 61 km north of the campus and one moderate typhoon passing through this 49-m-long and 12-m-wide building. By examining these data, we investigate the natural frequency and the rotation behavior of the long-strip-shaped building. Both the time-frequency and Fast Fourier Transform analyses of the microtremor and earthquake data show two dominant frequencies of ~1.2 Hz and 1.8 Hz occurred in the horizontal directions. The translation velocity and rotation rate are more significant in the transverse, short-axis direction and at the location away from the elevator of the building. The translation velocity array and rotational seismometer show rotations around the horizontal and vertical axes during the M 5.6 earthquake. The results of two natural frequencies and the corresponding rotational motions are most likely related to the asymmetric design of the building, which resulted in the non-rigid behavior of the structure. These findings may provide insights into improvements that could enhance the building’s resilience to seismic or typhoon events.
Assessment of humidity-inclusive heat index models over tropical megacities: Indonesia case
Authors: Ferdiansyah Muhammad Rezza , Nahas Alberth , Sopaheluwakan Ardhasena
Published: March 2024

One of the impacts on humans in megacities experiencing rapid urbanization is the increase in heat risk, primarily due to the urban heat island (UHI) phenomenon. One of the reasons for the intensification of UHI can be attributed to changes in land use and population growth. Additionally, global warming and climate change conditions that are currently occurring exacerbate this issue. For megacities located in tropical regions, such as Indonesia, there is limited available data regarding the impact of heat stress. Therefore, it is essential to develop a heat index suitable for tropical climates, characterized by high temperatures and humidity levels. Temperature and humidity are two crucial factors in quantifying the heat index to mitigate the risk of heat-related disasters. Consequently, when modeling the heat index for megacities in tropical regions, it is necessary to incorporate humidity. This study aims to compare different models for humidity-inclusive temperature indices, specifically Apparent Temperature (AT), Heat Index (HI), and Wet Bulb Globe Temperature (WBGT). These indices are computed using standard weather measurement data and re-analysis data to obtain spatial distribution. The current results demonstrate that these indices effectively captured the unusual heat conditions in Indonesia during the September 2023 period.
The effects of Mach number and IMF on the location of Venus bow shock: an MHD study
Authors: Xu Qi
Published: March 2024

Using global magnetohydrodynamics simulations, we investigate the effects of the solar wind magnetosonic Mach number and the interplanetary magnetic field (IMF) on the bow shock of Venus.  Our results reveal the following findings:  (1) The size of the Venusian bow shock is primarily determined by Mach number. An increase in Mach number results in the bow shock moving closer to Venus and a reduction in its flaring angle. (2) Both the subsolar standoff distance and the bow shock's flaring angle increase with the strength of the IMF components that are perpendicular to the solar wind flow direction (By and Bz in the VSO coordinate system), whereas the parallel IMF component (Bx) has a limited impact on the subsolar standoff distance but affects the flaring angle. (3) The cross-section of the bow shock is elongated in the direction perpendicular to the IMF on the Y-Z plane, and the elongation degree is enhanced with increasing intensities of By and Bz. (4) The quasi-parallel bow shock locates closer to the planet as compared to the quasi-perpendicular bow shock. These findings are in alignment with prior empirical and theoretical models. The influences of Mach number and IMF on the bow shock's position and geometry are attributed to the propagation of fast magnetosonic waves, showing the nature of the formation of a collisionless bow shock under the interaction of magnetized flow with an atmospheric object.
Effects of Forcing Uncertainties on the Thermospheric and Ionospheric Ensemble-based data assimilation.
Authors: Hsu Chih Ting , Pedatella Nicholas
Published: March 2024

Ensemble Data assimilation is a state-of-the-art method that can combine the observation information into a numerical model and further improve the performance of numerical weather prediction of the thermosphere and ionosphere.  The thermospheric and ionospheric weather are highly sensitive to the variation of forcings from above, including the solar irradiance and the magnetospheric forcings, and forcings from below, including waves and tides from the lower atmosphere. However, these forcings are hard to quantify. Building up the connection between the uncertainty of the forcings and the variability of a numerical model of the thermosphere and ionosphere that is used in a data assimilation system is a critical issue in thermospheric and ionospheric weather prediction.This study aims to advance our understanding of how solar irradiance variability and tide and wave variability drive the variability of Earth's thermosphere and ionosphere and improve our capability to represent this driver-response relationship in physics-based models using ensemble data assimilation. This study focuses on the National Center for Atmospheric Research’s (NCAR’s) Whole Atmosphere Community Climate Model – eXtended (WACCM-X). In the WACCM-X, the solar irradiance is determined by an empirical model, such as EUVAC, or by a real data set, and the waves and tides are generated self-consistently from the lower atmosphere in the model.We first try to quantify the solar irradiance variability in different wavelengths based on real data, including data from the Extreme Ultraviolet Variability Experiment (EVE) on Solar Dynamics Observatory (SDO) and the X-ray Photometer System (XPS)and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) on Solar Radiation and Climate Experiment (SORCE). Then, we quantify and qualify the response of the thermosphere and ionosphere in the WACCM-X to both the variation of solar irradiance and waves and tides by launching a set of ensemble simulation experiences. This will help prove the predictability of the thermospheric and ionospheric weather. 
Seasonal Shifting Patterns Emerge in Projected Trends of Solar Photovoltaic Potential over China 
Authors: Liu Yawen
Published: March 2024

With the projected rising use of solar energy, comprehensive knowledge of the spatial-temporal variations of future photovoltaic (PV) potential is of necessity, which however remains absent. Here based on the multi-model output from the Coupled Model Intercomparison Project Phase 6, trends of PV potential in three shared socioeconomic pathways (SSP) were examined with a focus on the seasonal characteristics. In SSP126 and SSP245, increases of PV potential are found over eastern Central China (ECC) in contrast to decline trends over Northwestern China in SSP370. Notably, the positive trends exhibit a distinct seasonality with maximum centers shifting south- north-south from spring to winter, forming an inverted V-shape pattern. This pattern is primarily determined by the reductions of anthropogenic aerosols. Meanwhile, the magnitudes of the maximum centers are strongly modified by aerosol compositions, background climatology PV potential, and the pace and amounts of emission reductions. Northern ECC shows the most profound increase in summertime PV potential among all regions and seasons. This increase remains significant and stable during different sub-time ranges from 2015 to 2050. The distinct seasonality signifies possibilities of coordinating energy supply across broader regions and multi- timescales, providing references for future PV deployment.
Nitrogen removal and carbon mineralization under coastal salinity intrusion
Authors: Wang Ziyan , Thibodeau Benoit
Published: March 2024

Rapid population growth and intensification of human activities have led to a massive increase in the release of nitrogen (N) to the environment, often ending up in aquatic ecosystems. Coastal wetlands, a transition ecosystem in the freshwater-to-marine continuum, play a vital role in reducing nitrogen through natural processes, including denitrification and anaerobic ammonium oxidation (anammox). Considering denitrification's risk of producing nitrous oxide—a potent greenhouse gas—and anammox's efficient co-removal of ammonium and nitrite, it's crucial to identify what controls the balance between these two key processes. However, the identity of the drivers controlling the relative abundance of these two N-removal processes and their respective interactions with carbon (C) and sulfur cycles are not well-documented, especially in coastal wetlands.This study investigated salinity's role in N reduction with carbon remineralization in coastal wetlands facing salinity intrusion. Using air-dried mangrove sediments mixed with anoxic artificial seawater of contrasting salinities (0, 10, 20, and 30 ppt) over a 28-day period, we monitored N and C transformation by the concentration of NH4+, NO2-, NO3-, dissolved inorganic carbon (DIC) and total alkalinity in the supernatant, and microbial community adaptation in sediment by molecular analysis. We applied the revised 15N-paring isotope technique in slurry incubation to quantify the potential of N loss pathways.Preliminary results indicate that significant N removal starts after a week of internal cycling between organic and inorganic N, with the maximum removal potential at 30 ppt salinity. Depletion of NO3- in the last week of incubation makes anammox stand out by utilizing NH4+ and NO2-. The rate of DIC release decreased with increasing salinity, displaying an inverse pattern to that of N species. This decoupling points to the co-existence of autotrophic anammox, heterotrophic denitrification, and sulfate reduction processes. The stoichiometric ratio of total alkalinity to DIC suggests a shift of the predominant carbon decomposition process as salinity increased, from denitrification to sulfate reduction. This shift could enhance the total nitrogen removal potential while slowing carbon remineralization, indicating a positive feedback loop for both nitrogen removal and blue carbon storage in response to salinity intrusion. We will further focus on 15N2 samples and microbial evidence to elucidate the interplay among nitrogen removal processes.
Influence of Tropical Seaways on the Climate and Vegetation in Tropical Africa and South America 
Authors: Tan Ning , Li Huan , Zhang Zhongshi , Wu Haibin , Ramstein Gilles , Sun Yong , He Zhilin , Su Baohuang , Zhang Zijian , Guo Zhengtang
Published: March 2024

The tectonically induced closure/constriction of the Central American Seaway (CAS) and Indonesian Seaway (Indo) during the early to mid-Pliocene has been associated with many climatic events, such as the onset of Northern Hemisphere glaciation, the intensification of the Atlantic meridional overturning circulation (AMOC) and Australian aridification. However, studies on how the closure/constriction of tropical seaways affects the tropical climate system are still sparse and not systematic. Previous studies have linked the constriction of Indo to the aridification over East Africa and discussed the role of CAS closure in affecting the moisture supply over South America, but the underlying mechanism and combined effect of both tropical seaways are not well studied. In this study, we evaluate the impacts of tropical seaways' closure/constriction and distinguish the relative roles of CAS and Indo on climate in tropical Africa and South America using the NorESM-L Atmosphere-Ocean General Circulation Model (AOGCM) and a dynamic vegetation model (LPJ-GUESS). Our results show that the closure of the CAS leads mainly to aridification in northeastern Brazil, resulting in an expansion of tropical xerophytic shrubland and savanna in this region. The narrowing of the Indo mainly leads to enhanced aridification in eastern tropical Africa and reduces the extent of tropical forests in eastern and northern tropical Africa, which is generally consistent with the data. The closure/narrowing of the two tropical seaways results in a superposition of the individual seaway's effect, particularly over the northeastern Brazil region, which exhibits enhanced aridification compared to the closure of the individual CAS. The seaways’ changes are shown to be pivotal for the evolution of climate and vegetation over East Africa and northeastern South America to contemporary conditions.
Seismicity under a dormant volcano: unveiling active crustal faulting beneath Piton des Neiges, La Réunion
Authors: Firode Lise , Duputel Zacharie , Ferrazzini Valérie , Lengliné Olivier
Published: March 2024

Earthquakes occur regularly in the vicinity of La Réunion's two main hotspot volcanoes, Piton des Neiges and Piton de la Fournaise. While earthquakes at Piton de la Fournaise volcano are clearly linked to its volcanic activity, the seismicity beneath Piton des Neiges is not well understood. However, except during eruptive periods, we often record more seismic events at Piton des Neiges than at Piton de la Fournaise. This study aims to better capture this seismicity to understand the nature and causes of the activity beneath Piton des Neiges, a volcano that has been dormant for 27,000 years. We improve previously available seismicity catalog by using template matching, double relocation and focal mechanism determination. Results indicate that the seismicity is primarily concentrated on a northeast-dipping reverse fault located in the oceanic crust beneath the volcanic edifice. We also identify secondary seismicity clusters with the same orientation in the vicinity of the main fault. Seismicity occurs continuously since the installation of the first seismological stations in the vicinity of Piton des Neiges in 1999. Although occasional periods of increased swarm-like activity are observed in 2011 and 2018, they do not correlate with markers of deep magma transfers that are often observed prior to the eruptions of the Piton de la Fournaise. These variations in seismic activity are limited to the main reverse fault and might be associated with periods of creeping activity. Our findings suggest that the seismic activity beneath Piton des Neiges is likely caused by regional tectonic stress and edifice loading on pre-existing faults, rather than from deep magma transfers. This conclusion is supported by the presence of various reverse faults with similar orientation and the lack of correlation between seismicity fluctuations and deep magmatic activity.
Global evaluation of simulated high- and low-flows from 23 macro-scale models
Authors: Guo Hui
Published: March 2024

Macro-scale hydrological/land surface models are important tools for assessing historical and predicting future characteristics of extreme hydrological events, yet quantitative understandings of how these large-scale models perform in simulating extreme hydrological characteristics remain limited. Here we evaluate simulated high- and low-flows from 23 macro-scale models within three modeling experiments (i.e., 14 climate models from CMIP6, 6 global hydrological models from ISIMIP2a and 3 land surface models from GLDAS) against observation in 633 unimpaired catchments globally over 1971-2010. Our findings reveal limitations in simulating extreme flow characteristics by these models. Specifically, we find that (i) most models overestimate high-flow magnitudes (bias range: +15% to +70%) and underestimate low-flow magnitudes (bias range: -80% to -20%); (ii) interannual variability in high- and low-flows is reasonably reproduced by ISIMIP2a and GLDAS models but poorly reproduced by CMIP6 models; (iii) no model consistently replicates the observed trend direction in high- and low-flows in over two-thirds of the catchments, and most models overestimate high-flow trends and underestimate low-flow trends; and (iv) CMIP6 and GLDAS models show timing biases, with early high-flows and late low-flows, while ISIMIP2a models exhibit the opposite pattern. Furthermore, all models performed better in more humid environments and non-cold regions, with model structure and parameterization contributing more to uncertainties than climatic forcings. Overall, our results demonstrate that extreme flow characteristics simulated from current state-of-the-art macro-scale models still contain large uncertainties and provide important guidance regarding the robustness of assessing extreme hydrometeorological events based on these modeling outputs.
Improving prediction of marine low clouds with cloud droplet number concentration and a deep learning method
Authors: Cao Yang , Zhu Yannian , Wang Minghuai , Rosenfeld Daniel , Zhou Chen
Published: March 2024

Marine low clouds have a pronounced cooling effect on the climate system because of their large cloud fraction (CF) and high albedo. However, predicting marine low clouds with satellite data remains challenging due to the non-linear response of marine low clouds to cloud-controlling factors (CCFs) and the ignorance of cloud droplet number concentration (Nd). Here, we developed a unified convolutional neural network (CNN) incorporating meteorology and Nd as CCFs to predict critical properties of marine low clouds, such as CF, albedo, and cloud radiative effects (CRE). Our CNN model excels in capturing the variability of these cloud properties, achieving over 70% variance explanation for daily 1x1 degree areas, surpassing previous studies. It also effectively replicates geographical patterns of CF, albedo, and CRE, including climatology and long-term trends from 2003 to 2022. This research underscores the significant potential of deep learning in deep exploitation of the information content of the data and, thus, advancing our understanding of aerosol-cloud interactions, a pioneering effort in the field.
Hygroscopic Behavior of Sea Spray Aerosols in Offshore Waters and Open Sea Areas Investigated with Aerosol Optical Tweezers
Authors: Qiu Jie , Zhao Chunsheng
Published: March 2024

Sea spray aerosols (SSA) play a crucial role as a primary aerosol source on a global scale, exerting significant influence on the Earth's radiative balance. Variations in sea water composition and concentrations across different regions can introduce disparities in sea spray aerosol properties. This study focuses on investigating and comparing the hygroscopicity of artificial sea salt particles and nascent sea spray aerosols from offshore waters and open sea areas within the Pacific Ocean. An aerosol optical tweezer (AOT) system is developed to measure the diameter hygroscopic growth factor (GF) and the hygroscopicity parameter (κ) of both artificial sea salt and natural sea spray aerosol particles. Our findings indicate that the hygroscopic properties of supermicron sea spray aerosols from offshore waters and open sea areas are remarkably similar and can be effectively represented by artificial sea salt particles. Furthermore, through the application of the theoretical Zdanovskii, Stokes, and Robinson (ZSR) mixing rule, the calculated κ values reinforce the validity of our aerosol optical tweezer measurements. Hence, we propose that, for modeling supermicron sea spray aerosol particles produced in either offshore waters or open sea areas, the properties of artificial sea salt particles, rather than NaCl particles, serve as robust proxies for natural sea spray aerosols. To be specific, we recommend utilizing a κ value of 1.20, for modeling sea spray aerosol properties at a relative humidity of 90% (RH=90%). This empirically derived κ value, rooted in our study, can enhance the accuracy of climate models and contribute to a more precise understanding of aerosol-climate interactions. 
Rayleigh and Love Wave Tomographic Imaging of Heterogeneous Crust in a magmatic rift: the Turkana Depression, East Africa
Authors: Musila Martin , Civilini Francesco , Ebinger Cynthia , Bastow Ian , Kounoudis Rita , Illsley-Kemp Finnigan , Ogden Chris
Published: March 2024

Theory and geoscientific observations demonstrate that plate stretching, heating, faulting, active and frozen magma intrusions, and extrusive eruptive products are consequences of mantle upwelling mechanism driving continental rifting. Problematic to this picture is the lack of consensus on how, when and where these processes modify the crust’s thermal and mechanical structure. We use data from East Africa’s 300-km wide Turkana Depression to investigate how the superposition of these rift processes and the spatial migration of the active plate boundary through time within one geodynamic setting modify the crust’s structure. Utilizing ambient noise seismic methods and data from the 34 station Turkana Rift Arrays Investigating Lithospheric Structure (TRAILS) seismic network, we invert for Rayleigh and Love tomographic models and overlay results with our local earthquakes crustal splitting results. Preliminary results show that regions that experienced Eocene flood magmatism have localized high Vs of > 3.4 km/s at mid-lower crustal depths implying that flood magmatism is fed by unknown localized centers and/or dike swarms. Quaternary eruptive centers with Vs < 3.4 km/s at mid-lower crustal depths are punctuated and irregularly spaced suggesting that bottom-up mantle upwelling influence their location. Regions with superposed Cretaceous-Paleogene and Miocene-Recent rift phases have persistent low velocities (Vs ≥ 3.8 km/s) to the mid-crust with thinner crust (~ 20 km); the active Miocene-Recent rift structures are oblique to the largely inactive Cretaceous-Paleogene rift structures implying no reactivation of pre-existing structures during modern-day rifting.
Surface Deposition of Icy Dust Entrained in Europa’s Plumes
Authors: Tseng Wei-Ling , Lai Ian-Lin , Ip Wing-Huen , Hsu Hsiang-Wen , Tzeng Yi-Shiang
Published: March 2024

With its subsurface ocean, Europa raises intriguing possibilities about the potential for extraterrestrial life beneath its icy crust. Its unique surface features present a dynamic and complex geophysical landscape that offers valuable insights into its evolution. This study explores the plume dynamics and deposition of icy dust particles on Europa. Utilizing a Direct Simulation Monte Carlo (DSMC) modeling of Europa's gaseous plumes, we use a hybrid model to understand dust dynamics entrained in the plumes. This approach allows us to consider various parameters such as production rate, initial velocity of gas and dust, and size distribution of dust particles, providing a comprehensive view of plume dynamics and highlighting their impact on Europa's surface characteristics. The results showing distinct plume morphologies and dust deposition patterns offer clues to our understanding of Europa's ongoing geological activity and subsurface ocean.
Three-dimensional characterization of an excavation-induced fracture network with gas tomography
Authors: Ringel Lisa Maria , de la Vaissière Rémi , Brauchler Ralf , Bayer Peter
Published: March 2024

In the safety assessment of a nuclear waste repository, it is crucial to identify and isolate possible pathways for radionuclides from the waste canister to the biosphere and vice versa. Despite the potential self-sealing properties depending on the host rock and the decrease of the permeability over time, the migration depends on the presence of a fracture network, the connectivity of the fractures, and their connectivity to tunnels or drifts. To describe the initial state of said pathways, we demonstrate the inversion of transient pressure measurements to delineate the structural and pneumatic properties of an excavation-induced fracture network at the Meuse/Haute-Marne Underground Research Laboratory (URL) operated by the French radioactive waste management agency ANDRA.The tomographic tests were carried out as sequential constant-rate injections of nitrogen and the resulting pressure perturbations were recorded in nearby borehole intervals. In total, nine boreholes with two injection/monitoring intervals each are available on a volume of approximately 3m times 3m times 5m. Therefore, the joint inversion of more than 300 signals allows unique insights into the excavation-induced fracture network.A discrete fracture network (DFN) model is applied for the forward and inverse modeling. Thereby, the strong heterogeneity of the distribution of hydraulic or pneumatic properties caused by the fracture network can be described. A numerical model is used to simulate the transient pressure diffusion in the DFN. The structural properties and the permeability of the DFN model are characterized by solving the inverse problem. The inversion relies on a stochastic model of the DFN parameters based on the Bayesian equation. The posterior distribution, i.e., the distribution of the DFN parameters given the measured data, is the product of likelihood and prior distribution. The likelihood function compares the error between the measured data and the simulated outcome of the tomography experiments for a given DFN model. The prior distribution includes information about the fracture properties obtained in previous studies. The posterior distribution is characterized by generating samples from the posterior with Markov chain Monte Carlo (MCMC) methods. Due to the unknown number of fractures, the insertion and deletion of fractures are possible according to the reversible jump MCMC algorithm.The inversion approach results in several DFN realizations that are approximately equally likely which is illustrated in a fracture probability map and a map of the permeability distribution. Thereby, preferential flow paths can be characterized.
Forecasting of air pollution episodes using machine learning in Kathmandu Valley
Authors: Pokharel Binod
Published: March 2024

Air pollution, increasingly aggravated by climate change, presents a multifaceted threat encompassing environmental degradation, public health risks, and social disruptions. In Kathmandu, Nepal's capital, the city's distinctive bowl-shaped topography frequently results in the entrapment of pollutants, leading to prolonged periods of hazardous air quality. This study focuses on identifying the broad-scale synoptic conditions that intensify air pollution in the Kathmandu Valley across various seasons. Our analysis encompasses high pollution instances, scrutinizing alterations in local and external sources, transboundary transport, and meteorological conditions. Our prior research highlights the profound impact of transboundary smoke from agricultural burning in northwest India and forest fires in Nepal, particularly evident in early 2021 when severe pollution led to the closure of schools in Kathmandu. The objective of this study is to delineate the specific meteorological conditions that facilitate the ingress and retention of polluted air in the valley, driven by large-scale synoptic weather patterns. Subsequently, we plan to employ machine learning techniques for pattern recognition, aiming to precisely predict high pollution events. This approach is expected to serve as a vital instrument for timely intervention and strategic policy formulation, addressing the complex challenges of urban air pollution.
Warming has differential effects on the diversity, richness and biomass of soil bacteria and fungi
Authors: Wang Xudong , Zhu Biao
Published: March 2024

Climate warming has caused widespread global concern. However, how warming affects soil microbial diversity, richness, community structure and biomass is still poorly understood. Therefore, this study conducted a meta-analysis of 1044 observations from 144 publications by collecting relevant data on a global scale. The results showed that warming significantly altered soil temperature, soil water content, community structure of soil bacteria and fungi, and beta diversity of fungi. Warming decreased soil microbial diversity, richness and biomass, but the overall effect was not significant, while warming increased soil physicochemical and plant biomass indicators. Soil bacteria and fungi showed opposite trends in response to warming (e.g., the weighted mean effect values of the bacterial Shannon index, OTU Richness, and PLFA were all negative, whereas those for fungi were all positive), with fungi being more sensitive to warming than bacteria. Model selection analysis indicated that the RR (response ratio) of pH, ecosystem type and warming magnitude are important factors influencing the RR of soil bacterial diversity and richness. In addition, warming significantly decreased the OTU richness of forest soil bacteria and significantly increased the OTU richness of cropland soil fungi. The RR of bacterial richness (Chao1, OTU Richness) was significantly different among ecosystems, whereas that of fungal richness was not. The RR of diversity and richness of soil bacteria showed significant correlations with the RR of pH and warming magnitude. Overall, these findings improve our understanding of soil microbial responses under global warming. 
The Ieodo Ocean Research Station (Ieodo-ORS) and Research Endeavors by the Korea Hydrographic and Oceanographic Agency (KHOA)
Authors: Jeong Kwang-Young , Seo Gwangho , Kwon Seok Jae , Ham Hyun-Sik , Oh Hyun-Ju
Published: March 2024

Constructed in June 2003, "The Ieodo Ocean Research Station (Ieodo-ORS)," a steel-framed tower-type platform, is strategically positioned near a submarine rock named Ieodo. Its primary objective is to advance our understanding of oceanic and atmospheric phenomena and their intricate interactions in the East China Sea. This station attains global significance owing to its distinctive open-sea location, situated approximately 149 km away from Jeju Island. Initially established by KIOST as part of the Research and Development project of the Ministry of Oceans and Fisheries, control of the Ieodo-ORS was transferred to the KHOA in 2007. Outfitted with 29 instruments for collecting oceanographic, meteorological, and environmental data, the Ieodo-ORS functions as a central hub for diverse projects initiated by the KHOA. These projects are geared towards refining observation techniques, optimizing the utilization of observational data, and systematically monitoring oceanic and atmospheric environments. Since 2014, the KHOA has executed the 'Ieodo-ORS Field Research Trip' program, providing support for a dedicated ship to service the Ieodo-ORS and leverage its facilities. The ultimate objective of the KHOA is to establish the Ieodo-ORS as a globally recognized scientific station through a comprehensive array of academic research initiatives.