bluuebunny/crossref_metadata_2025 huggingface dataset:
Methane release drives subglacial microbial community assembly at the western margin of the Greenland Ice Sheet
Authors: Wentzel Lia Costa Pinto , Klímová Petra , Stehrer Polášková Anna , Hatton Jade , Žárský Jakub , Trubač Jakub , Píka Philip , Murphy Jack , Hawkings Jon , Stibal Marek
Published: March 2024

The basal environments of ice sheets play an important role as places of methane (CH4) production, storage, and release. Recent investigations have confirmed the release of subglacial methane of microbial origin at the western margin of the Greenland Ice Sheet (GrIS). This methane may then serve as a substrate for methane-consuming microorganisms and thus significantly shape microbial community assembly in GrIS subglacial environments.We conducted a comparative analysis of the composition of exported microbial assemblages from six regions spanning a 2,000-km transect along the western margin of the GrIS. Based on 16S rRNA gene sequences, we identified taxa predominantly affiliated with Pseudomonadota (formerly Proteobacteria), Actinomycetota (formerly Actinobacteriota), and Acidobacteriota. Within the Pseudomonadota, notable genera such as Rhodoferax, Polaromonas, and the methylotrophic Crenothrix and Methylotenera were identified as the most abundant. Importantly, we observed a pattern in community composition related to measured methane concentrations at each site, resulting in three distinct clusters: samples from sites with atmospheric methane levels (i.e., with no significant methane release), those from sites with elevated methane concentrations, and methane release hotspots.Our results align with recent findings, suggesting that microbial communities colonizing methane-emitting sites may have the potential to utilize methane as a resource, thereby reducing its release into the atmosphere and so mitigating its impact on climate change. Furthermore, our findings may facilitate the identification of potential methane release hotspots based on microbial community analysis.
Effects of Artificially Reducing Hydraulic Conductivity of Coastal Aquifers on Maximum Sustainable Withdrawal Rate
Authors: Sun Jiazhi , Fan Bo , Lu Chunhui
Published: March 2024

Traditional physical barriers for mitigating seawater intrusion are expensive and necessitate complex engineering measures such as excavation or piledriving. An alternative cost-effective method involves artificially reducing the hydraulic conductivity in the upper parts of selected areas (modified zones) using a precipitate. This study presents an analytical solution using the finite Fourier Cosine transform to evaluate the impact of a modified zone on mitigating seawater intrusion and improving the maximum sustainable withdrawal rate in a coastal confined aquifer. Numerical solutions employing the variable density flow code SEAWAT are conducted to validate the proposed analytical solution. Effects of hydraulic conductivity, length, and thickness of the modified zone, along with the well location on the interface toe location and maximum sustainable withdrawal rate are investigated. Additionally, the sensitivities of dimensionless parameters are accessed under various combinations of the length and thickness of the modified zone. Results show that the interface toe shifts inland with an increase in the dimensionless equivalent hydraulic conductivity (κ) and a decrease in the dimensionless length of the modified zone (lD). Consequently, the maximum sustainable withdrawal rate increases as κ decreases and lD increases. The location of the pumping well significantly influences the maximum sustainable withdrawal rate in aquifers with finite domains, considering both inland and lateral boundary conditions. Sensitivities of β = L/W and η = K1H2/(qf L) to the maximum sustainable withdrawal rate are an order of magnitude greater than the sensitivity of αT,D = αT/H, considering aquifer length (L), aquifer width (W), aquifer hydraulic conductivity (K1), aquifer thickness (H), constant inland flux (qf), and transverse dispersivity (αT). These findings offer valuable insights for constructing modified zones to migrate seawater intrusion and for deploying pumping wells in coastal areas.
Quantitative attribution of historical anthropogenic warming on the extreme rainfall event over Henan in July 202
Authors: Zhao Dajun , Xu Hongxiong , Chen Lianshou
Published: March 2024

The “21·7” Henan extreme rainfall event (HNER) caused severe damage and many fatalities. The daily precipitation during this event (from 1200 UTC on July 19, 2021 to 1200 UTC on July 20, 2021) was 552.5 mm and the maximum hourly precipitation was 201.9 mm (at 0900 UTC on July 20, 2021). Previous studies have suggested that an evaluation of the role of anthropogenic climate change in extreme rainfall events is crucial in disaster prevention and mitigation under the current global climate crisis. We examined the changes in the coverage and intensity of extreme rainfall during the “21·7” HNER event under anthropogenic climate change using a set of convective permitting simulations. Our results showed that the regional-average magnitude of the 48-h accumulated rainfall during the “21·7” HNER was increased by 5.7% (95% confidence interval: 4%–11%), which is in agreement with the Clausius–Clapeyron (CC) rate, while the area of extreme rainfall (≥500 mm) increased by 29.9% (95% confidence interval: 21%–40%) as a result of anthropogenic climate change over the Henan region during the late 20th century. Anthropogenic climate change has led to a warm moist tongue over the target region, which has increased the column-integrated water vapor content and induced an anomalous cyclone–anticyclone pair. Anthropogenic warming has caused stronger southerly and southeasterly winds, leading to stronger convergence in the lower troposphere, stronger updrafts in the mid-troposphere and stronger divergent winds in the upper levels. These effects have all contributed to the increase in rainfall. These results enhance our understanding of the dynamic effects of anthropogenic warming on the “21·7” HNER and provide additional evidence that anthropogenic warming increased the magnitude of the “21·7” HNER in China.
Observations of near-inertial internal wave amplification and enhanced mixing after surface reflection
Authors: Liu Kun , Chen Xu , Zhan Peng , Wang Hui
Published: March 2024

The overreflection process of near-inertial internal waves (NIWs) has been theoretically predicted for several decades; however, to the best of our knowledge, this phenomenon has never been comprehensively investigated in real ocean scenarios. Based on the buoy observations collected several days after the passage of Typhoon Lekima in the Yellow Sea, a NIW surface overreflection event is clearly captured. The observed NIWs undergo nearly total reflection meridionally but are amplified zonally after reflection by approximately 20% in amplitude and 56% in vertically integrated horizontal kinetic energy. Ray tracing analysis indicates that the NIW was generated in the wake of Typhoon Lekima in the area north of the Shandong Peninsula and may propagated to the buoy station as coastal-trapped internal Kelvin waves. A simulation using a slab mixed layer model suggests that local wind work was insufficient to generate the amplified NIWs. The temporal evolution of near-inertial energy also implies that the intensified near-inertial waves cannot be attributed to the spontaneous generation resulting from unbalanced flows or the parametric subharmonic instability of M2 internal tides during the reflection period. We found a high temporal correlation between the zonal NIW enhancement and the duration of a meridional lens-type shear flow after reflection, which is consistent with the Stern’s overreflection theory (Stern, 1977) that perpendicular background shear flow can feed energy to the incident NIWs. This indicates that the enhanced NIW may be stimulated by the near-surface reflection and the rotation effect plays a crucial role in the NIWs overreflection process in the real ocean. Furthermore, enhanced instability are found between the ocean surface and the upper thermocline after reflection. This study provides observational evidence that the background field could inject energy into the near-inertial band through NIW overreflection process, and may shed some light on understanding upper ocean mixing caused by NIW reflection.
Observations of a Mini-Magnetosphere Above the Martian Crustal Magnetic Fields
Authors: Fan Kai , Wei Yong , Fraenz Markus , Cui Jun , He Fei , Yan Limei , Chai Lihui , Zhong Jun , Rong Zhaojin , Dubinin Eduard
Published: March 2024

Mars is typically regarded as a non-magnetic planet. Currents in the Martian ionosphere generate a Venus-like induced magnetosphere which deflects the solar wind flows and piles up the interplanetary magnetic fields. However, crustal magnetic fields in the southern hemisphere influence local plasma properties. Using observations from the MAVEN mission, we characterize the distinguishing plasma characteristics of a mini-magnetosphere that forms on the Martian dayside. We establish three criteria to differentiate this mini-magnetosphere from the induced magnetosphere. Notably, the mini-magnetosphere exhibits higher plasma beta (values near 1), with a balance between planetary ions, crustal magnetic fields, and the solar wind at the magnetopause. Observations show that the crustal magnetosphere reaches an altitude of 1,300 km, larger than one-third of the Martian radius, indicating a dichotomy between the induced northern and the crustal southern magnetospheres. These findings offer novel insights into the distinctive properties of hybrid magnetospheres in the near-Mars space.
CME Transit Time Prediction Based on Coronagraph Observations and Machine Learning Techniques
Authors: Li Yucong , Yang Yi , Shen Fang , Lin Rongpei
Published: March 2024

A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the solar corona, and is one important source of severe space weather events. With the accumulation of CME observations by coronagraphs and the excellent performance of convolutional neural network (CNN) in image classification, fast and accurate prediction of the transit (arrival) time of CMEs became possible. In this study, we present a new prediction method utilizing both a deep learning framework and the physical characteristic of CMEs based on remote-sensing observations. In total, the initial and arrival data of 168 geo-effective CME events from 2000-2020 are collected for the study. A convolutional neural network model is trained with the coronagraph images of the events observed by SOHO/LASCO. The output of the trained CNN is further combined with the initial CME speed to carry out a linear fitting process. The comparison with the prediction results merely based on a CNN or a linear fitting by CME speed indicates that the hybrid model can improve the accuracy of CME arrival time prediction.
Modeling the occurrence probability of sporadic-E based on GNSS radio occultation data
Authors: Bilitza Dieter , Truhlik Vladimir , Arras Christina , Haralambous Haris
Published: March 2024

Sporadic E (Es) layers are a well-known ionospheric phenomenon, whose occurrence can cause anomalous propagation of radio waves utilized for communication and broadcast. Es layers are very thin layers of metallic ions such as Fe+, Mg+, and Ca+ formed  mainly by atmospheric tidal wind shears.  Their peak density exceeds the E-layer peak density and can even exceed the F-layer peak density. Because of their effect on radio waves a user needs to know when there is a high probability of Es occurrence. It is the goal of this study to develop a global model of Es occurrence probability and to make it publicly available through inclusion in the International Reference Ionosphere (IRI).We use Es data obtained by Arras et al. (2022) from GNSS radio occultation observations from various satellites (CHAMP, Spire, KOMPSAT-5, COSMIC1 & 2, TANDEM-X, and TerraSAR-X) for the time period 2001-2022. We will briefly discuss the variation of the Es occurrence rate with latitude, longitude, local time, season, solar activity, and magnetic activity. as observed with this data base. We found that the strongest dependencies are with local time, latitude and season, while weaker ones exist with longitude and solar activity. We use spherical harmonics to describe the global expansion of the strongest influences establishing a core model. Second order influences, e.g., solar activity variations, are modelled as a perturbation on the core model. First results obtained with the new model will be presented.ReferencesArras, C., Resende, L.C.A., Kepkar, A. et al. Sporadic E layer characteristics at equatorial latitudes as observed by GNSS radio occultation measurements. Earth Planets Space 74, 163 (2022). https://doi.org/10.1186/s40623-022-01718-y 
The predictability of eddy shedding from Kuroshio loop in the Luzon Strait: insights from ensemble forecast
Authors: Liu Danian , Shu Yeqiang
Published: March 2024

The Kuroshio often intrudes into the South China Sea (SCS) in the form of a loop through the Luzon Strait in winter, accompanied by eddy shedding, significantly impacting the circulation and thermodynamic state in the northern SCS. The eddy shedding of the Kuroshio loop into the SCS is influenced not only by local winds but also modulated by the western Pacific (WP) circulation. Given the uncertainties in simulating the WP circulation, accurately forecasting the process of the Kuroshio loop and eddy shedding into the SCS poses a considerable challenge. Ensemble forecast based on Ensemble Kalman Filter (EnKF) assimilation represents an advanced forecasting methodology. Compared to deterministic forecast from a single model, ensemble forecast effectively considers model error uncertainties throughout the forecasting process. Utilizing the high-resolution SCS-WP EnKF assimilation forecast system, our study focuses on the predictability of a strong Kuroshio loop and subsequent eddy shedding into the SCS during the winter of 2016-2017. The findings indicate that the successful forecast of this strong Kuroshio loop and eddy shedding primarily attributed to the assimilation of ocean observations in the Subtropical Countercurrent (STCC) region, partially supported by the assimilation of observations in the North Equatorial Current (NEC) region. Specifically, assimilating observations in the STCC region reproduced observed westward-propagating cyclonic eddies, which, upon collision with the Kuroshio in the Luzon Strait, intensified its intrusion into the SCS and led to eddy shedding. Meanwhile, assimilation in the NEC region represented the weak background current of the Kuroshio, further promoting the formation of a strong Kuroshio background loop and the occurrence of eddy shedding in the Luzon Strait according to the teapot effect.
Global vulnerable basins suffering social-ecological impacts of water scarcity
Authors: Zhao Fubo , Wu Yiping
Published: March 2024

The UN water conference, convened in March 2023, calls for governing water and addressing climate change in tandem to co-achieve related sustainable development goals. However, the actual (water scarcity under current climate conditions) and potential (potential water scarcity under climate change) impacts of water scarcity on social-ecological impacts are rarely assessed. Herein, we developed a framework that integrates water scarcity and climate sensitivity to assess the socio-ecological vulnerability of global basins. We found that basins that already experience water scarcity are exhibit a disproportionate magnitude of climate sensitivity, which exacerbated the challenges associated with water resources management. We identified the vulnerable basins by integrating socio-ecological vulnerability and found that the most vulnerable basins are mainly located in developing countries. Therefore, the urgent international cooperation for reducing vulnerabilities of water scarcity is required. Measures involved in current Integrated Water Resources Management and Climate Change Adaptation may not be enough to alleviate the water crisis and to adapt to climate change in these vulnerable basins. We thus urge policy makers in regions suffering vulnerable water scarcity to integrate both approaches to manage water and climate in tandem and synergistically achieve related sustainable goals.
Promoting effect and mechanism of algae bloom on in situ N2O emission: a case from Zhanjiang Bay, China
Authors: Cai Shangjun , Lao Qibin , Chen Chunqing , Zhou Xin , Liu Sihai , Jin Guangzhe , Chen Fajin
Published: March 2024

The algae bloom in the bay can lead to a large amount of N2O in situ production. However, the coupling relationship between N2O and algae bloom and their mechanism in the bay remains unclear. To address this issue, N isotope culture experiment and qPCR experiment were measured in Zhanjiang Bay during the normal period and algae bloom period. The results showed that the in situ N2O production in algae bloom is 3 times than normal period. Stable isotope rate cultivation experiments also indicated that denitrification and nitrification-denitrification were promoted in the water during algae bloom period, but the increase in nitrification-denitrification is more significant. In addition, the main way for in situ N2O production, shifted from denitrification in the normal period to nitrification-denitrification during algae bloom period. The increase of denitrification and nitrification-denitrification during algae bloom period was attributed from the increase  of fresh particulate organic matter (POM) from algae bloom organisms. The increase of fresh POM enhanced the degradation, providing the necessary anaerobic and hypoxic environment for denitrification and nitrification-denitrification. Additionally, a positive linear correlation between N2O concentrations and ammonia-oxidizing bacteria (AOB) and denitrifying bacteria (nirK), provided further evidence of significant nitrification-denitrification and denitrification processes occurring in the water during algae bloom. Our findings contribute to a clearer understanding of mechanism of in situ N2O emission during algae bloom period.
Qc, Qp, Qs, Qi, and Qsc attenuation parameters in the southern part of Georgia
Authors: Shengelia Ia , Jorjiashvili Nato , Godoladze Tea , Buzaladze Albert
Published: March 2024

Georgia is located in the Caucasus between The black and the Caspian seas and is surrounded by the Greater and Lesser Caucasus. Among the seismic areas of Georgia, the volcanic upland of Javakheti situated in the south of Georgia is notable for its high level of seismicity where three large earthquakes with M6 occurred in the last century. The main goal of the study is to investigate the attenuation properties of the lithosphere in the region using a hundred and twenty local earthquakes in 2008-2020  recorded at five seismic stations equipped with broadband Guralp CMG40T and Trillium 40  seismometers. Earthquake magnitudes varied from 1.5 to 4.1; epicentral distances and depth were smaller than 60 km and 19 km, respectively. The quality factors of coda waves Qcand direct P, S waves Qp,and Qs have been estimated using the single back-scattering model and the extended coda normalization methods, respectively. Wennerberg’s approach has been used to estimate intrinsic Qi and scattering Qs attenuation parameters. The Q values were fitted to a  power-law, of form Q(f)= Q0 (f)n, where Q0 is the quality factor at 1Hz and n is the frequency relation parameter, which depends on the heterogeneity of the medium. The obtained values of Qc, Qp, Qs, Qi, andQsc show the frequency-dependent character in the frequency range of 1.5-24 Hz and are expressed as:Qc = (47.6±3.8)(1.034±0.048),  Qp = (17.4±2.3)𝑓(1.100±0.033), Qs = (28.8±3.3)𝑓(1.048±0.039), Qi = (62 ± 4) f (0.969±0.052),  Qsc = (177 ± 6) f (0.932±0.051)The calculated attenuation parameters characterize the entire earth's crust under the Javakheti plateau and the surrounding area. The observed Qc and Qi values are almost identical at different central frequencies and both of them are less than Qsc. This means that the effect of intrinsic attenuation is dominated by scattering attenuation. Comparison of our results for similar lapse times to those obtained in other tectonic and seismic active regions show that the Q values and their frequency-dependent relationships are in an interval of values of tectonically active and highly heterogeneous regions. The results obtained will be useful for source parameter estimation, ground motion prediction, and hazard assessment of the study regions.
Storyline approach for the analysis of the 2012 drought in Serbia and possible future similar events
Authors: Tosic Milica , Djurdjevic Vladimir , Tosic Ivana , Lazic Irida
Published: March 2024

In 2012, Serbia experienced one of its warmest and driest years on record. The summer of 2012 marked the highest temperatures recorded since meteorological measurements began in Serbia, in relation to the reference period from 1991 to 2020. Throughout the summer, the entire country faced severe drought conditions persisting until the end of November. Serbia's agriculture is very vulnerable to drought - an estimated annual economic loss is approximately 2 billion euros due to extreme 2012 drought. Recent studies emphasize the value of the storyline approach in offering a comprehensive and manageable framework for evaluating environmental, societal and economic risks associated with climate change. Considering the potential for more intense climate events resulting from climate change, we decided to apply the storyline approach, to determine what future events similar to drought 2012 might look like and how they are influenced by different climate change scenarios. We constructed drought metrics based on precipitation deficit, following the method proposed by van der Wiel et al. [1], and with the use of the EOBS dataset. Analyzing future scenarios involved creating a meteorological analogue to the 2012 drought, using single model large ensemble historical and future scenario simulations from CMIP6 database - the MPI-M Earth System Model version 1.2, for different SSP scenarios. This analysis offers insights into different storylines, aiding the assessment of climate risks and the potential impacts of hypothetical drought scenarios.The summer of 2012 was extraordinarily warm, and, as previous studies show significant changes in temperature extremes during the summer season in Serbia, we included analyses of temperature anomalies during the summer. Additionally, to create more comprehensive storylines, our study involves analyzing large-scale atmospheric patterns. Our results show an increase in drought severity in a warmer future, offering an enhanced understanding of how extreme events like the 2012 drought (or more severe) are changing measurably due to climate change, and provide examples of potential impacts, in order to raise public awareness about the potential consequences of future climate change in Serbia.[1] van der Wiel, K., Lenderink, G. and de Vries, H., 2021. Physical storylines of future European drought events like 2018 based on ensemble climate modelling. Weather and Climate Extremes, 33, p.100350.
Potential of land-based terrestrial carbon sinks to mitigate climate change
Authors: Wang Ang , Fang Yunting , Gurmesa Geshere Abdisa
Published: March 2024

Enhancing terrestrial ecosystem carbon sinks is one of the effective strategies to achieve carbon neutrality targets for climate change mitigation. However, efforts to enhance the carbon sink mainly focused on natural climate solutions, including protecting, restoring, and managing terrestrial ecosystems. The contributions of artificial measures, such as rock weathering, urban alkaline material weathering, and desert saline alkali soil water to terrestrial ecosystem carbon sinks have often been overlooked by previous estimates of terrestrial carbon sinks. To account for major carbon sink measures, we proposed a new concept of “four-color” terrestrial carbons based on their formation/sink mechanisms, i.e., green carbon (the carbon sequestered by forest, grassland, and inland wetland), black carbon (carbon sink through the addition of carbon-rich materials, such as straw, organic fertilizers, and biochar to the soil), blue carbon (the carbon stored in coastal ecosystems), and white carbon (carbon sink by chemical processes). We reviewed the potential measures for enhancing the different carbon sinks to provide a framework for achieving carbon neutrality targets.We identified 15 measures for enhancing the sink of the different carbon groups. The enhancement approaches for green carbon sinks mainly include protecting, restoring, and managing forest, grassland, and inland wetland ecosystems. Adding carbon-rich materials to cropland soil is the major measure to enhance black carbon sink. The enhancement of blue carbon sink mainly focuses on ecosystem protection and restoration. We proposed enhancing silicate and carbonate rock weathering, irrigation and salt washing in arid regions, and utilizing urban alkaline materials as measures to enhance white carbon sink. With proper implementation of the above measures, we estimated C sequestration of 16.7 Pg CO2 yr-1 for green carbon, 5.8 Pg CO2 yr-1 for black carbon, 1.1 Pg CO2 yr-1 for blue carbon, and 7.7 Pg CO2 yr-1 for white carbon. Our results showed the potential to enhance the “four-color” carbon sinks globally by 31.4 Pg CO2 yr-1, higher than the estimate in the IPCC AR6. However, large uncertainties still exist in the estimation of current and future carbon sink potential in terrestrial ecosystems due to the different approaches used in different studies, large spatiotemporal variation, and insufficient data of carbon storage and sink. Therefore, we emphasize the need for strengthening monitoring and basic data acquisition and establishing rapid and accurate quantification techniques for terrestrial carbon sinks. Furthermore, future research should focus on the potential and multiple enhancement measures of white carbon under different climates and its response to global change.
The impact of the Airflow Separation on the Wind-Wave Momentum Flux
Authors: Tan Peisen , Savelyev Ivan , Haus Brian , Matt Silvia
Published: March 2024

In this laboratory investigation, a range of wind and wave conditions was sampled to visualize the airflow and to quantify the mechanisms through which the momentum is transferred towards a wavy surface. The experiments were conducted in the SUrge STructural AIr-sea INteraction facility located at the University of Miami. Three distinct background wave conditions were subjected to wind forcing U 10  of 7 and 14 m/s, to investigate the effects of wave amplitude, frequency, as well as wind forcing on the airflow regime and momentum transfer. We report that under the milder wind forcing (U 10 = 7 m/s ) and the least steep wave, no sign of sheltering was observed. The airflow streamlines follow the shape of surface waves, resulting in a wide area of lower-than-average pressure above the wave crest. In this regime, more than 90% of the air-sea momentum transfer comes from the viscous drag at the surface due to the smooth airflow tightly following a smooth wave surface. Meanwhile, such pressure distribution above the waves is mostly the result of the Bernoulli Effect due to the wave shape, with almost-symmetrical low pressure above the wave crest and high pressure above the wave trough. However, a sole increase in wave frequency, while maintaining the amplitude and the wind forcing, is enough to induce airflow sheltering on the leeward side of the wave due to the steepened wave crest. Further, an increase of wind forcing over the same steepened crest did not alter the airflow regime or the pattern of the airflow pressure distribution, while doubling the momentum transfer magnitude. Here, the sheltered airflow regime is further evidenced by the enhanced turbulent kinetic energy observed on the leeward side of the wave. In these conditions, the viscous drag weakens, and the form drag rises to become the dominant mechanism for the air-sea momentum flux, accounting for over 50% of the total stress. In this regime, the pressure distribution is the result of aerodynamic sheltering, with high pressure on the windward side and low pressure on the leeward side. The results of this work will serve as the first step within a larger effort to develop a new formulation for the wave model wind input function, which will account for the airflow separation physics.
Role of groundwater during hydrological extremes in the glaciated and snow-fed high Alpine catchment under climate change
Authors: Fan Xinyang , Hofmeister Florentin , Schaefli Bettina , Chiogna Gabriele
Published: March 2024

Groundwater plays a pivotal role in the water cycle but its interplay with hydrological processes has often been neglected or overly simplified in hydrological models of high-elevation catchments. This may increase uncertainties in future projections and impede a holistic understanding of the hydrological changes. High Alpine catchments, in fact, display complex surface and subsurface processes and lack of observations. Here, we investigate the role of alpine groundwater in the hydrologic response by partitioning the observed streamflow variations to glacier recessions, snowmelt, rainfall, and for the first time - groundwater fluxes at the Martell valley in Italy since the 2000s. To examine the dynamic interactions of these components in detail, we adopt a modeling framework that combines the physics-based model WaSiM (with an integrated groundwater module) with meteorological inputs obtained from the weather model WRF. Extensive field observations (meteorology, hydrology, geomorphology, piezometric levels, stable water isotopes) are collected to constrain the hydrological model parameters and for model evaluation. This study quantifies the contribution of groundwater in moderating the intensity and timing of hydrological extremes (high and low flows) in the selected high-elevation catchment and emphasizes the significance of groundwater in sustaining water availability in this sensitive environment subject to climate change.
Declining trend of dust aerosols over central China observed with polarization lidar during 2010-202
Authors: He Yun , Jing Dongzhe , Liu Fuchao , Yin Zhenping
Published: March 2024

East Asian desert is one of the most important dust sources that contribute approximately ~40% of the global annual dust emissions and ~88% of the dust over mainland China and adjacent seas, significantly impacting the regional environment and climate. In the past decade, the frequency of dust storm outbreaks has largely declined in the sources of Asian dust due to the improvement of natural conditions (i.e., weakened surface wind speed, enhanced precipitation, and soil water) and the promotion of vegetation cover caused by afforestation in North China. However, it is still rarely reported how the dust properties after long-range transport in the downstream regions respond to this downtrend. During 2010-2020, we have been conducting routine monitoring of height-resolved dust aerosols with a ground-based polarization lidar in Wuhan (30.5°N, 114.4°E), a mega city in central China. The dust optical depths (DOD) have decreased by 0.011 per year, accounting for ~22% of the decrease rate for local aerosol optical depths (AOD). The dust mass concentration and columnar mass density also have declined by 2.03 μg·m-3 and 1.97 mg·m-2 per year, respectively. During spring and winter, a mass of long-range transported dust plumes intrude into Wuhan, with seasonal mean DOD of 0.21 and 0.15, respectively. Dust aerosols in winter are generally located at lower altitudes than in spring, concentrating mainly below 1.0 km. Wintertime dust shows a slightly smaller particle depolarization ratio than spring (0.11 versus 0.14), indicating a weakened nonspherical shape caused by high-level moisture/polluted conditions during winter. The surface PM10 concentration presents a downtrend with a rate of -8.0 μg·m-3·yr-1. This study provides the climatology of dust properties over central China, supplementing our understanding of the feedback in the downstream regions to the reduction of dust emissions in the East Asia desert.
Exploring Runoff Generation Processes: A Global Comparative Study of Experimental Watersheds
Authors: Tian Fuqiang , Cui Zhen
Published: March 2024

Comprehending runoff generation processes remains a formidable challenge for hydrologists. This study advocates for a comparative examination of these processes across global experimental watersheds. As part of the HELPING decadal initiative, a dedicated working group has been established. Embracing a Darwinian methodology, our objective is to synthesize information through comparative studies across a diverse array of local ecosystems, with the aim of cultivating a global perspective and formulating overarching theories.We warmly welcome and invite research groups managing experimental watersheds worldwide to actively participate in this collaborative effort. The working group is designed to achieve the following objectives:1) Compile datasets for experimental watersheds globally, maximizing the utilization of available information.2) Identify both similarities and differences in watershed characteristics and processes across diverse experimental sites.3) Develop a more quantitative framework to discern dominant processes within specific watersheds, thereby contributing to a profound understanding of hydrological dynamics.By bringing together researchers and research groups from across the globe, this collaborative initiative seeks to transcend geographical boundaries and foster a holistic understanding of runoff generation processes.
Simulation of soil water transport in apple-soybean intercropping system under drip irrigation and film mulching
Authors: Wang Lisha , Wang Ruoshui , Dai Houshuai , Xiong Chang , Zhang Meng , Chen Li , Wang Xin
Published: March 2024

Intercropping and mulched drip irrigation are widely used techniques for achieving high yields and water savings. Understanding the soil moisture distribution characteristics of intercropping farmland under mulched drip irrigation is crucial for improving water use efficiency, increasing yields, and boosting income. This study aimed to investigate soil moisture under different irrigation amounts and film mulching times through a two-year field experiment.In the experiment, two upper limits of irrigation amount (50% and 80% of field water holding capacity) and two film mulching times (soybean sowing to pod setting stage and film mulching throughout the growth period) were set. The HYDRUS2D model was used to simulate the difference in soil moisture at various positions and the two-dimensional distribution characteristics of soil moisture in intercropping drip irrigation farmland. The results showed that the soil moisture model based on HYDRUS2D had high precision, with a coefficient of determination ranging from 0.60 to 0.93 and a root mean square error ranging from 0.006 to 0.038 cm3/cm3. In the horizontal direction, the soil moisture content at 2.3 m from the tree row increased by an average of 4.87% to 17.65% compared to other distances. In the vertical direction, the maximum soil moisture content was observed in the 40 cm soil layer, with an increase of 26.04% to 42% compared to the 10 cm soil layer. The 2-D soil moisture distribution showed that the moisture saturation zone of drip irrigation was mainly concentrated in the 0-20 cm soil layer. These findings can serve as a reference for developing irrigation schedules for intercropping farmland under drip irrigation.
Extreme rainfall in Northern China in September 2021 tied to air–sea multi‐factors
Authors: Sun Yue , Li Jianping , Wang Hao , Li Ruize , Tang Xinxin
Published: March 2024

The September rainfall over Northern China (NC) in 2021 was the heaviest since 1961 and had unprecedented socioeconomic impacts. Holding the hypothesis that the drivers of extreme climate events usually contain extreme factors, we firstly propose the Ranking Attribution Method (RAM) to find the possible air–sea multi-factors responsible for this rainfall event. Via the atmospheric bridges of zonal-vertical circulation and Rossby wave energy propagation, the remote factors of warm sea surface temperature anomalies (SSTA) over the tropical Atlantic, cold SSTA over the tropical Pacific, Southern Annular Mode-like pattern in the Southern Hemisphere and North Pacific Oscillation-like pattern in the Northern Hemisphere jointly strengthened the Maritime Continent (MC) convection and Indian monsoon (IM). Through meridional-vertical circulation, the intensified MC convection enhanced the subtropical high over southern China and induced ascending motion over NC. The local factor of extreme air acceleration in the east Asian upper-level jet entrance region further anchored the location of the southwest-northeast rain belt. The strengthened IM and subtropical high over southern China induced considerable moisture transport to the rain belt via two moisture channels. The combined effect of these extreme dynamic and moisture conditions formed this unprecedented rainfall event. This study suggests that the RAM can effectively reveal the factors that contributed to this extreme rainfall event, which could provide a new pathway for a better understanding of extreme climate events.
The future changes in spatio-temporal distribution of urban heat load and factors that affect its variability
Authors: Janků Zdeněk , Dobrovolný Petr , Geletič Jan , Lehnert Michal
Published: March 2024

Summer temperature extremes are increasing rapidly under the current global climate change. Urban environments are among those most exposed to temperature extremes due to the urban heat island, and these exacerbated conditions significantly affect human health and activities, making urban heat load one of the most fundamental concerns for people living in cities. Our research quantifies spatio-temporal changes in urban heat load in two Central-European cities (Brno and Ostrava, Czech Republic) in different geographical configurations. We applied the urban climate model MUKLIMO_3, combined with the cuboid method, to simulate recent and future distributions of four summer climate indices. The simulation results clearly indicate continuous climate warming and project a significant increase in the mean annual values of summer climate indices by the end of the 21st century, particularly in the built-up areas with a predominance of impervious surfaces. Both model simulations and in-situ observations confirm that the magnitude of these changes can differ significantly from city to city suggesting the distribution of urban heat load is not only influenced by climate change, but also by local geography and anthropogenic factors. To determine the causes of the differences in urban heat load variability, we applied land use/land cover configuration metrics and correlation analysis using various geographical factors. Our results show that a compact and less fragmented land use/land cover structure can significantly increase the urban heat load. Altitude also has a strong influence on the heat load pattern in complex terrain. Therefore, some cities are and may continue to be extremely vulnerable to adverse summer temperature extremes. We suggest that urban planners should take into account the current impact of land use/land cover structure on temperature conditions when designing effective adaptation measures to mitigate urban heat load.
Expansion of wildfires and their impact on carbon emissions over pan-Arctic permafrost
Authors: Zhu Xingru , Jia Gensuo , Xu Xiyan
Published: March 2024

Wildfires over permafrost put perennially frozen carbon at risk. However, burned area and wildfire carbon emissions from biomass burning over the diverse range of permafrost regions have not been revealed. Here, we show that continuous permafrost was a major contribution to wildfire expansion and carbon emission in the pan-Arctic over the last two decades. Burned area and wildfire carbon emissions dramatically increased over continuous permafrost during the last two decades, but decreased in other permafrost regions. Accelerating wildfire emission from continuous permafrost region is the single largest contribution to the increased emissions in northern permafrost regions. The share of permafrost in global wildfire CO2 emissions grew from 2.42% in 1997 to 20.86% in 2021. Wildfire expansion is closely linked to an increased soil moisture deficit, considering wildfires there combust more than 90% of belowground fuel. Continuous permafrost experiences more severe fire-induced degradation. Active layer thickening following wildfires over continuous permafrost lasts more than three decades to reach a maximum of more than triple the pre-fire thickness. These findings highlight expansion of wildfires and acceleration of fire-induced carbon emission from continuous permafrost region, which disturbs organic carbon stock, accelerates the positive feedback between permafrost degradation and climate warming. 
Revolutionizing Groundwater Level Prediction in Taiwan: Unleashing the Power of Transformer Neural Networks
Authors: Sun Wei , Liou Jia-Yi , Chang Fi-John
Published: March 2024

    In the face of evolving global weather patterns attributed to climate change, precise prediction of groundwater levels is increasingly essential for effective water resource management. This significance is particularly pronounced in regions like Taiwan, where groundwater is a pivotal water source. This study focuses on the Zhuoshui River basin in central Taiwan and explores a Transformer Neural Network (TNN) based on a 20-year hydrometeorological dataset at a 10-day scale to predict groundwater levels. Our investigation reveals that the innovative TNN model outperforms conventional models, such as the Convolutional Neural Network (CNN) and the Long Short-Term Memory neural network (LSTM). The TNN model's superiority is evidenced by its enhanced predictive capabilities, as measured by metrics like R2 and MAE. Notably, the TNN model excels in providing precise forecasts (MAE < 1 m) for the majority of groundwater monitoring stations, notwithstanding challenges in areas facing overexploitation.    This groundbreaking study marks the first attempt of the TNN model to predict groundwater levels, showcasing its robust performance and broad applicability. The TNN model emerges as a valuable tool for groundwater level prediction, contributing to sustainable groundwater management and effective resource utilization amid the backdrop of climate change. With the potential to address climate-related challenges, the TNN model stands as a pivotal asset for optimizing strategies in groundwater resource management.
Studying Western North Pacific High Activity in Relation to the East Asian Summer Monsoon Using GK-2A Data
Authors: Wie Jieun , Byon Jae-Young , Moon Byung-Kwon
Published: March 2024

The Western North Pacific High demonstrates a close association with the East Asian Summer Monsoon. By employing GK-2A satellite data, we categorized the Western North Pacific High into three types and analyzed how the distinctive features of each type correlated with East Asian Summer Monsoon. The analysis extended from June to August, encompassing the years 2020 through 2023. Additionally, we utilized ERA5, NCEP2, and ASOS data for the same period to compare and complement the findings derived from the satellite observations. By performing empirical orthogonal function (EOF) analysis on the cloud amount data obtained from GK-2A observations over East Asia, we identified three primary modes: the first, second, and third modes denoting unimodal patterns, tropical influences, and high-latitude influences, respectively. Notably, the second mode is correlated with the northward movement of the East Asian rain bands attributed to the westward expansion and intensification of the western subtropical high. Moreover, there is a discernible lag relationship, PC1 precedes PC2 and PC2 precedes PC3. Consistency between the results obtained from ERA5 and NCEP2 data is evident across all modes, except for EOF1. These findings collectively underscore the potential of this study to detect variations in the Western North Pacific High and their impact on the East Asian Summer Monsoon.Acknowledgement: This research was supported by “The Technical Development on Weather Forecast Support and Convergence Service using Meteorological Satellites” of the NMSC/KMA (KMA2020-00121) and the National Research Foundation of Korea (NRF) grant funded by the Government of Korea (MSIT) (No. 2022R1A2C 1008858)
What can we learn from X-ray diffraction and seismic velocities across the alpha-beta quartz transition at lower crust conditions? 
Authors: Mingardi Giulia , Gasc Julien , Ardit Matteo , Alvaro Matteo , Schubnel Alexandre
Published: March 2024

Quartz, the most common mineral constituent of the Earth’s continental crust, undergoes the displacive α-β transformation at pressures and temperatures of the lower crustal conditions. This transition is associated with important variations in the thermodynamic properties (such as thermal expansion and isothermal bulk modulus) and is therefore thought to cause important seismic velocity contrasts that are distinguished by seismic tomography. The α-β transition is characterized by a non-linear increase in volume with temperature and an abrupt variation in bulk modulus, which, at the transition, drops from about 70 GPa to nearly zero within 10-15 K. Although well-known at room pressure, the behavior of quartz across the transition at high pressure, i.e., at Earth-relevant conditions, remains largely unexplored.In this work, we have characterized this transition at high P-T conditions by means of X-ray diffraction and acoustic measurements. The experiments were performed at the European Synchrotron Radiation Facility (ESRF, beamline ID06) using a multi anvil press up to 3 GPa and 1400 °C. The measured velocities show a strong decrease of Vp toward the phase transition, followed by a steep increase in the β-field, reaching values higher than those in the α-field. In our data, this increase is not as large as that predicted by thermodynamic models using the known elastic properties of quartz (e.g., Abers and Hacker 2016). As anticipated, Vs is rather constant throughout the transition, resulting in major variations in the Vp/Vs ratio. The unit cell volume was calculated from the collected diffraction patterns. Contrary to the well-documented negative thermal expansion of quartz in the β-field at room pressure, the unit cell volumes obtained at high-pressure show a slight continuous volume increase during heating after the phase transition.In conclusion, we document here that the behaviour of quartz across the α-β transition at high P-T is different from what has been previously predicted, which is likely a consequence of the poor knowledge of β-quartz thermo-elastic properties at high P-T. This could affect the interpretation of seismic data in the deep crust, which is currently based on extrapolations of the room-pressure behavior of the α-β quartz transition.