bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Streamflow Component Structure on Characterizing Storage–Discharge Dynamics in an Analytical Probabilistic Streamflow Model
Authors: Huang Chia-Chi , Yeh Hsin-Fu , Yang Ya-Sin
Published: March 2024

Streamflow represents the hydrological output behavior of the catchment system and can elucidate the physical processes of other hydrological variables, such as rainfall–runoff processes and storage–discharge dynamics. Understanding streamflow dynamics not only enhances comprehension of complex hydrological processes and influencing factors, but also aids in estimating potential hydrological conditions in ungauged areas. In this study, we explored the differences in the flow duration curve (FDC) structure of streamflow components, ranging from slow to fast, using multiple hydrograph separation. Additionally, we analyzed the recession index and recession parameters of individual recession segments to characterize the storage-discharge dynamics based on the linear and nonlinear reservoir assumptions, respectively. We applied an analytical probabilistic streamflow model to determine which structure better aligns with the model’s physical basis, assuming streamflow generation from groundwater discharge when a sequence of rainfall events increases soil moisture beyond the retention capacity. It also provides estimations of optimal recession parameters for comparison with individual recession segment results. The recession analyses and multiple streamflow components separation revealed differences in dominant recession index, recession parameters, and streamflow complexity between catchments, highlighting their relationships with catchment characteristics. Recession parameters from FDCs with different components demonstrated the storage–discharge mechanisms associated with changes in streamflow components. The conformity of multiple streamflow component structures to the model’s basic assumptions can be evaluated through the model performance, contributing to an understanding of streamflow component structures in catchments and their relevance to specific streamflow generation mechanisms.
Streamlining Multi-Data Geophysical Inference with BayesBridge
Authors: Magrini Fabrizio , He Jiawen , Sambridge Malcolm
Published: March 2024

The Earth's interior structure must be inferred from geophysical observations collected at the surface. Compared to just a few decades ago, the amount of geophysical data available today is voluminous and growing exponentially. Dense seismic networks like USArray, AlpArray, and AusArray now enable joint inversions of various geophysical data types to maximise subsurface resolution at scales ranging from local to continental. However, the practical application of joint inversions faces several challenges:Various geophysical techniques typically probe different scales and depths, complicating the choice of an appropriate discretisation for the Earth's interior.
Different geophysical observables may respond to physical properties that are not directly related (e.g., density and electrical conductivity), making the construction of self-consistent parameterisations a non-trivial task.
Without a comprehensive understanding of noise characteristics, standard methods require assigning weights to different data sets, yet robust choices remain elusive.
Capable of overcoming these recognised challenges and allowing estimates of model uncertainty, probabilistic inversions have grown in popularity in the geosciences over the last few decades, and have been successfully applied to specific modelling problems. Here, we present BayesBridge, a user-friendly Python package for generalised transdimensional and hierarchical Bayesian inference. Computationally optimised through Cython, our software offers multi-processing capabilities and runs smoothly on both standard computers and computer clusters. As opposed to existing software libraries, BayesBridge provides high-level functionalities to define complex parameterisations, with prior probabilities (defined by uniform, Gaussian, or custom density functions) that may or may not be dependent on depth and/or geographic coordinates. By default, BayesBridge employs reversible-jump Markov chain Monte Carlo for sampling the posterior probability, with the option of parallel tempering, but its low-level features enable effortless implementations of arbitrary sampling criteria. Utilising object-oriented programming principles, BayesBridge ensures that each component of the inversion -- such as the discretisation, the physical properties to be inferred, and the data noise -- is a self-contained unit. This design facilitates the seamless integration of various forward solvers and data sets, promoting the use of multiple data types in geophysical inversions.
Using Time clustering to anlyze how precipitation cause landslides occurrence
Authors: He Yufeng
Published: March 2024

Landslides are closely related to precipitation events. However, the mechanism of how different types of precipitation events clustering actuate the landslides remains poorly understood. We collected and analyzed the precipitation and landslides data in the upper reach of Min River, Sichuan, China, which is a typical area composed of four counties with frequent landslides and seasonal variations in precipitation. Based on the time cluster algorithm, we identified six models of different landslides with precipitation events clustering drivers. 70% of landslide events are associated with short-term precipitation within 7 days before the occurrences. Nearly all the massive landslide events are preceded by the short-term precipitation and temporal clustering of moderate to extreme precipitation events. We conclude a causal relationship between precipitation event clustering and landslides. Our results represent a clear example of the potential for precipitation events to landslides or other hazards.
Vertical and lateral changes of hydrothermal alteration in andesitic composite volcanoes – Linking flank collapse with hydrothermal activity
Authors: Kereszturi Gabor , Álvarez-Valero Antonio M. , D’Mello Nessa , Suárez Barrios Mercedes , Sanchez Rachelle , Miller Craig , Coulthard Daniel A.
Published: March 2024

Andesitic composite volcanoes located at convergent plate margins can host extensive zones of hydrothermally altered rocks, which can influence their rock mechanics and potentially modulate eruptive activity. Hydrothermal minerals typically form along fractures and permeable zones above cooling and degassing magma bodies. A robust understanding of the vertical and lateral distribution of hydrothermal minerals can therefore reveal the location of (former) magma bodies/fluid source and can indicate areas susceptible for future flank collapse processes.This study investigates the type and extent of hydrothermal alteration within the Wahianoa Formation (160-80 ky) of Ruapehu volcano in New Zealand by integrating field observations, Scanning Electron Microscopy (SEM-EDS), Shortwave Infrared (SWIR) reflectance spectroscopy, X-Ray Diffraction (XRD), sulfur isotope systematics and Inductively coupled plasma mass spectrometry (ICP-MS), thermodynamic modelling and airborne geophysics. Ruapehu shows a diverse suite of weathering and hydrothermal alteration minerals formed in relation to the present and fossil hydrothermal systems. Wahianoa Formation is one of the oldest formations, showing remarkable diversity of hydrothermal alteration that has never been studied before. The distal rock has only supergene alteration with abundant goethite, hematite and phyllosilicate mineral associations, while the hydrothermally altered rock are rich in phyllosilicates, Fe-oxides, pyrite, jarosite, alunite, gypsum anhydrite, and native sulphur. The latter is interpreted to be formed under intermediate and advanced argillic alteration conditions (>150 °C and low pH). In contrast, the some of the exposed outcrops within the upper Wahianoa valley show distinct mineralogy, that is rich in quartz, pyrite, illite(-chlorite) and tourmaline, indicating a transition from the advanced argillic conditions toward more phyllic alteration type (>220 °C and more neutral pH). Our results indicate a complex hydrothermal system developed within the Wahianoa Formation between 150-80 ky, providing a great example to study vertical and lateral mineralogical changes. A new model has been proposed to integrate hydrothermal alteration history into the Mt Ruapehu’s evolution that can better depict ongoing alteration processes and triggers for flank instability and volcanic hazards associated hydrothermal systems.
Characterization of near-shore fresh water and seawater interactions-the scale issues drawn from the experimental and numerical approaches
Authors: Ni Chuen-Fa , Duong Thanh Quynh , Hsu Chia-Yu , Vinh-Truong Nguyen Thai , Chang Yu-Huan
Published: March 2024

Understanding the dynamics of water and mass interactions in the coastal area is essential to quantify the influences of near-shore land use on the coastal aquifers and water environment. The study aims to integrate innovative experiments and modeling techniques to assess the heat and water exchanges in the coastal aquifer of the Taoyuan Tableland in northwestern Taiwan. The site-specific hydraulic and heat tracer tests are conducted to obtain flow and heat transfer properties for the specific aquifer layers at the site. We then used the SEAWAT numerical model to quantify the freshwater and seawater interactions. The model calibration relies on the groundwater levels and quality obtained from monitoring wells installed perpendicular to the shoreline. The experimental results show that the active heat tracer tests could significantly improve the identification of aquifer layers along a well and allow for the estimations of high-resolution natural groundwater flux toward the sea. The estimated flow rate based on the heat tracer test is approximately 0.2 m/day per unit depth. The numerical model shows good agreement with the observed water levels in wells. In the study area, the location of the seawater/groundwater mixing interface is estimated at approximately 350m seaward from the shoreline, which suggests the submarine groundwater discharge zone for the site. The vertical profile model shows that the flow rate for the 100m depth aquifer varies from 51 to 60 m3/day per unit width, depending on the tidal variations and upstream groundwater levels. The results show a large flow rate discrepancy between experimental and numerical approaches, which the resolution scales of the approaches might induce in the calculations. The water levels obtained from the fully opened screen wells might mix the flow responses in different aquifer layers.
Formation mechanism of continental mid-lithosphere discontinuity and its effects on craton instability under variable tectonic regimes
Authors: Fu Hui-Ying , Li Zhong-Hai
Published: March 2024

The continental mid-lithospheric discontinuity (MLD) has been widely detected within most cratons, with the dominant depth of 70-100 km and a significant drop of shear-wave velocity of 2-12%. However, the formation mechanism and corresponding strength of the MLD are widely debated, which may strongly affect the roles of MLD on craton evolution. In this study, we have conducted systematic numerical models with hydrated blocks generation routine to simulate the formation of MLD. Model results indicate that the MLD may be induced by the accumulation of hydrous minerals within cratonic lithosphere, and acts as a water collector during craton evolution. Further on, we focus on the roles of MLD in craton evolution. Based on the comparison among variable mechanisms, the viscosity of MLD may vary from the relatively high viscosity induced by wet olivine to the rather low viscosity induced by antigorite. Thus, systematic numerical modeling has been conducted with the MLD of contrasting strengths, i.e. the wet olivine-induced MLD or antigorite-induced MLD, to investigate the effects of MLD on the craton instability under variable tectonic regimes (stable, extension, compression, mantle flow traction, or mantle plume). Model results indicate that the wet olivine-induced MLD could not lead to lithospheric delamination under all the tested tectonic regime. In contrast, the weak antigorite-induced MLD could localize large strain and decouple the overlying and underlying lithosphere significantly; despite this, the lithospheric delamination requires additional conditions. Craton destruction only occurs with the connection of the weak antigorite-induced MLD and the sub-plate asthenosphere during craton extension or mantle plume activity. The partial melting process during large amount of extension or upwelling of mantle plume with high temperature anomaly and large size is a key condition. In addition, the depleted cratonic lithospheric mantle with low density would increase the intrinsic buoyancy of lithosphere, and inhibit the lithospheric delamination and craton destruction. Therefore, the effect of MLD on the craton destruction is not as significant as previously considered in the models, which requires additional strict conditions that are not widely satisfied on the Earth. This may explain the general stability of most cratons with widespread MLDs.
The research of early arrival waveform inversion and its application in imaging the shallow fault zone structure
Authors: Ma Xiaona , Wang Weitao , Xu Shanhui , Yang Wei , Zhang Yunpeng
Published: March 2024

Waveform inversion is a robust geophysical tool for reconstructing subsurface structures, involving an iterative process that begins with an initial model and utilizes complete information from observed data to update the target model. However, its wide field applications have been impeded by challenges such as strong nonlinearity, nonconvexity of the misfit function, and complexity of the propagation medium. To mitigate these issues and enhance the linearity and simplicity of the inversion process, we employ early arrival wavefields to construct misfit function that promotes  global convergence.High-resolution structure imaging of active faults within urban areas is vital for earthquake hazard mitigation, so we perform a seismic survey line crossing the Pearl River Estuary Fault (PREF) in Guangzhou, China. First, ten shots of a new and environmentally friendly gas explosion source are excited with about 1 km spacing and recorded by 241 nodal short-period seismometers with an average spacing of 60 m. Then, based on these acquisition data, we adopt waveform inversion to explore the kinematic and dynamic information of early arrival wave-fields to recover the subsurface structures. Here, the early arrival wavefields were defined as those events that arrived within a few periods of the first arrivals. The inversion results indicate that while the low-velocity zone (LVZ) in depth surrounding the PREF is 2.5 km in width and extended to 0.7 km, another LVZ of 1.5 km in width and extended to 0.7 km in depth is surrounded by the Beiting-Nancun fault. We observe that the analysis of evolution and activities of the fault systems reveal no historical earthquakes in our study area; we interpret that the two LVZs controlled by the faults are probably attributed to the fluid dynamics, sediment source, and fault motion at different geological times, rather than fault-related damage zones.Summarily, the results can provide significant basis for earthquake prevention and hazard assessment in Guangzhou. The finding also shows that the waveform inversion can effectively explore the fine structure of active faults in urban area with dense linear array and spare active source excitations. This acquisition and inversion methods should have broad applications in other cities.
Improving cloud forecasts with assimilation of cloud-/precipitation-affected microwave and infrared radiances using MPAS-JEDI
Authors: Liu Zhiquan , Ban Junmei , Banos Ivette
Published: March 2024

MPAS-JEDI, a relatively-new data assimilation (DA) system for the Model for Prediction Across Scales – Atmosphere (MPAS-A) based upon the Joint Effort for Data assimilation Integration (JEDI), allows to assimilate cloud-/precipitation-affected satellite microwave and infrared radiance data to analysis microphysical parameters, e.g., mixing ratios of hydrometeors. Global cycling DA experiments were conducted in the context of MPAS-JEDI’s hybrid-3DEnVar configured at 30km resolution with 80-member ensemble input at 60km that is produced using MPAS-JEDI's ensemble of 3DEnVar. The benchmark experiment assimilates conventional observations plus clear-sky radiances from AMSU-A and MHS. All-sky experiments add the assimilation of all-sky microwave (MW) radiances from AMSU-A’s and/or ATMS’s window channels over water as well as infrared (IR) channels of two geostationary sensors GOES-ABI and Himawari-AHI. In addition to the impact assessment on dynamic and thermodynamic variables, we investigated more the impact on cloud forecasts in terms of fitting to ABI/AHI radiance data at different wavelengths. The community radiative transfer model (CRTM) is used as the observation operator in both all-sky radiance DA and evaluation. The substantial positive impact on cloud forecasts was obtained with all-sky microwave DA (individually or collectively from AMSU-A and ATMS) in terms of a better forecast fitting to observed ABI/AHI channel 13's radiances up to 7 days, especially over tropical regions, where the day-1 forecast root-mean-square error is reduced up to 10%. Cloud forecast impact from assimilating all-sky ABI/AHI 3 water vapor channels' radiances is more limited although a clear benefit is seen for middle/upper troposphere moisture field, which is consistent with ABI/AHI water vapor channels' sensitivity height. Future research direction for all-sky MW and IR radiance DA with MPAS-JEDI will also be discussed.
Effects of regolith properties on the Martian subsurface water distribution using a global climate model
Authors: Kobayashi Mirai , Kamada Arihiro , Kuroda Takeshi , Kurokawa Hiroyuki , Aoki Shohei , Nakagawa Hiromu , Terada Naoki
Published: March 2024

In today’s extremely dry Mars, water vapor “adsorption” on regolith grains is thought to play crucial roles in subsurface water retention and water vapor exchange with the atmosphere (Fanale & Cannon, 1971; Zent et al., 1993, 1995, 2001; Böttger et al., 2005; Savijärvi et al., 2016, 2020). Global models that explicitly account for water diffusion in the shallow subsurface and calculate subsurface water distribution have assumed globally uniform regolith properties to simplify assumptions (Böttger et al., 2005; Schorghofer & Aharonson, 2005; Steele et al., 2017). However, Pommerol et al. (2009) examined the adsorption efficiency of six samples similar to the Martian regolith and found that the samples with smaller grain sizes store more adsorbed water due to their larger specific surface areas. Therefore, we have newly implemented a regolith scheme in a Mars Global Climate Model (MGCM), considering regolith properties like grain size, porosity, and the specific surface area. The grain size distribution was obtained from the empirical equation as a function of thermal conductivity (Presley & Christensen, 1997). The distributions of porosity and the specific surface area are also determined, referring to the laboratory experiments of Sizemore & Mellon (2008). Our results clarify that regolith grains with large specific surface areas in the northern low and mid-latitudes and the southern high latitudes, which have high adsorption coefficients, affect water storage. Subsurface water in the northern low and mid-latitudes exists up to 0.5–1wt% as adsorbed water. Regolith with high adsorption properties makes the depth of subsurface ice shallower in the southern high latitudes. Pore ice accumulates in regions poleward of 50°N and 50°S and the west of Elysium Mons and Olympus Mons, which is consistent with previous simulations. Also, with a homogeneous specific surface area, seasonal increases in pore ice were calculated at a depth of about 60 cm in mid-latitudes with low thermal inertia and high atmospheric water vapor content, but with the specific surface area map, the seasonal increases were not demonstrated. This study suggests that adsorption properties influence subsurface water dynamics, emphasizing the importance of considering inhomogeneous regolith properties in models of subsurface water distributions and the atmospheric water cycle including the regolith.
Evaluation of the Potential for Detecting MCS Causing Heavy Rainfall in the Korean Peninsula Based on Rawinsonde Data-Derived Instability Indices
Authors: Kim Minsu , Suh Myoungseok
Published: March 2024

Recent studies have shown an increase in frequency and intensity of heavy rainfall (Hev_Ran) events in the Korean Peninsula, located along the eastern coast of the Asian continent, due to global warming. Additionally, several studies have shown that the atmospheric environment and MCS(Mesoscale Convective Systems) causing Hev_Ran in East Asia differs from those in North America and Europe. Therefore, this study aims to reevaluate the possibility of detecting MCS causing Hev_Ran in Korea using 8 instability indices (Inst_Ind) (CAPE, KI, LI, SSI, SRH, SWEAT, TTI, and TPW) derived from rawinsonde data provided by the KMA(Korea Meteorological Administration). Considering the regional, seasonal, and temporal variations of Hev_Ran events in Korea, this study also conducts a detailed investigation on the detection capability of each instability index and optimize thresholds. For the recent ten years (2013~2022) during the rainy season (May~Sep), hourly accumulated precipitation data from the KMA and upper-air observation data from 8 rawinsonde stations in Korea were used for this purpose. While AWS measures precipitation every minute, rawinsonde observes the upper atmosphere twice (00 and 12UTC) or four times (00, 06, 12, and 18UTC) a day depending on the station. Thus, this study defines the collocated data as those AWS data within -2h~+2h temporally and 100km spatially based on Rawinsonde observations. Comparing the Inst_Ind during climate average (Cli_Ave) and Hev_Ran, significant differences were noted for KI, SWEAT, and TPW, with more than 20% differences between Cli_Ave and Hev_Ran for exceeding 30mm/h. However, CAPE, LI, SSI, SRH, and TTI did not show significant differences between Cli_Ave and Hev_Ran. POD and FAR were used to reevaluate the Hev_Ran detection level of the Inst_Ind, and the Hev_Ran detection level of the Inst_Ind was evaluated for various Hev_Ran intensity (30, 40, and 50 mm/h). Thresholds for Inst_Ind were used from the marginally instability levels suggested by KMA or the NOAA. The analysis has indicated usefulness in detecting Hev_Ran using SSI, KI, and TPW showing high POD(0.92~0.98) and FAR(0.91~0.99). However, detection levels using CAPE, LI, SWEAT, SRH were less effective regardless of Hev_Ran intensity, showing low POD (0.32~0.48) and high FAR (0.90~0.98). It was noted that while POD increases with higher Hev_Ran intensity, FAR also increases simultaneously.This presentation will further detail the optimization of thresholds for Inst_Ind and provide a more detailed presentation of the detection capability of Hev_Ran systems and MCS, segmented by station and time.This work was funded by the Korea Meteorological Administration Research and Development Program under Grant (RS-2023-00239653)
Advancing Cloud Science: Exploring the Lifetime of Indiviual Cloud Droplets through Aerosol Optical Tweezers and Raman Spectroscopy
Authors: Guo Shuqi , Zhao Chunsheng
Published: March 2024

The lifetime of clouds has an important influence on radiation balance, atmospheric matter cycling, and global precipitation patterns. However, current assessments of cloud lifetime rely on statistical methods, underscoring the need for effective observational techniques. Moreover, existing research predominantly centers on precipitation removal, neglecting the process of cloud dissipation.Utilizing optical tweezers-Raman spectroscopy technology and CCD real-time imaging, this study conducts experiments on the evaporation of individual suspended droplets with a series of concentration gradients. We establish a method for quantifying the evaporation time of microdroplets, and characterize their evaporation dynamics through the temporal variation of OH-stretching Raman peak. Our research reveals the substantial influence of droplet solute concentration on evaporation time, indicating that even minute variations in solute concentration within cloud droplets can induce profound disparities in their lifetime.Furthermore, alterations in environmental relative humidity also have an impact on the dissipation of cloud droplets. These findings hold critical scientific significance, enhancing our understanding of cloud lifetime and providing a scientific foundation for accurately simulating cloud generation and dissipation processes in numerical models.
Hydrological dynamics of a Northern cultivated peatland and implications for management
Authors: Pham Tung , Marttila Hannu , Liimatainen Maarit , Lötjönen Timo , Kekkonen Jarkko , Läpikivi Miika , Kløve Bjørn
Published: March 2024

Cultivated peatlands play a significant role in grass and dairy production, particularly in Northern regions. However, agricultural activities on these organic soils often lead to undesirable environmental effects, namely increased nutrient leaching and greenhouse gas (GHG) emissions. The hydrological characteristics and dynamics of cultivated peatlands significantly influence the formation of leachable nutrients and GHGs. Currently, there is a gap in the comprehensive understanding of hydrological responses in these cultivated areas. To address this gap, the NorPeat research platform at Ruukki research station, managed by the Natural Resources Institute Finland (Luke), has been established in Northern Ostrobothnia, Finland. The site features varying peat thickness (10-80 cm) over a mineral subsoil and a subsurface drainage system consisting of perforated pipes installed within the mineral layer at a depth of 120-130 cm from the surface. Continuous hydrological monitoring of key parameters such as groundwater table, soil moisture, drainage discharge, precipitation, and soil temperature has been ongoing on the platform since 2016. In this study, we focus on the dynamics of the groundwater table and soil moisture in response to seasonal variations, soil structure, and land management; to establish a comprehensive water balance quantifying water fluxes (evapotranspiration, drain flow, overland flow) to the adjacent stream; and to develop a hydrological conceptual model of the field. The outcomes of this research are expected to improve our understanding of cultivated peatland hydrology, inform future studies on environmental impacts, and provide valuable data for both farmers and policymakers.
Modelling sub-grid peatland vegetation dynamics in the ORCHIDEE-PEAT land surface model
Authors: Qiu Chunjing , Ciais Philippe
Published: March 2024

Peatlands store about one-third of global soil organic carbon. The carbon dynamics and storage of peatlands depend on the balance between plants’ carbon uptake and microbial carbon decomposition. As a result of global warming and climate-driven ecohydrological changes, the plant community composition of peatlands is projected to change, affecting the carbon sequestration and storage capacity of these ecosystems both directly and indirectly by modulating water flows. However, while there has been a notable focus on studying the variation in the water table position of peatlands and its consequential influence on the dynamics of peatland soil carbon, the impacts of peatland plant community composition have been largely overlooked. To accurately predict peatland carbon dynamics, land surface models need to account for the diversity of peatlands plant types and the competitive interactions among them. We incorporated six plant functional types (PFT) into the ORCHIDEE-PEAT model to represent mosses, grasses, shrubs, and trees growing in peatlands. Areas covered by each PFT are functions of the bioclimatic limitations, mortality, and establishment of each PFT, as well as competitions among PFTs. The model will be employed to assess the effect of climate change on peatland vegetation dynamics and carbon fluxes.
Spectral Indices and Evidence of Wave-Wave Modulation in Observations of the Interplanetary Magnetic Field
Authors: Loto'aniu Paul , Krista Larisza
Published: March 2024

We present wave and turbulence observations by the DSCOVR spacecraft during solar flare and CME events. Over 9-day period, the spectral indices within the magnetic field power spectral density (PSD) in the RTN and mean-field-aligned (MFA) coordinates do not agree. In the inertial range the transverse PSD follows a Kraichnan–Iroshinikov -3/2 index when in MFA coordinates, while in the RTN frame the same PSD is more complex showing Kolmogorov -5/3 index at lower frequencies followed by a shallow index close to -1 at the inertial subrange before steepening to -2 close to the He+ cyclotron frequency. We show that the differences are due to the changing interplanetary magnetic field (IMF) direction relative to the solar wind velocity within the CME periods. We present evidence of wave-wave modulation and suggest that lower frequency waves in the solar wind can modulate the growth rates/propagation of ion cyclotron waves providing a method to transfer energy in the solar wind to smaller scales. Furthermore, we suggest that the Kraichnan–Iroshinikov -3/2 index in the inertial range can be explained by combining containment due to wave generation/propagation and stochastic Brownian motion in the solar wind. When these two phenomena are equal, they combine to create a -3/2 index.
Bathymetry derivation and slope-assisted benthic mapping using optical satellite imagery in combination with ICESat-2
Authors: Liu Yuhui , Zhou Yu , Yang Xiaoqiang
Published: March 2024

Mapping benthic reefs at high resolution and accuracy is vital for the management and conservation of coral habitats. Optical remote sensing data has emerged as a valuable tool for large-scale reef mapping in the past decades, with numerous data sets and methods being utilised and developed. In this study, we present a comprehensive comparison of optical remote sensing based bathymetry and benthic mapping methods. We use different optical data including WorldView-2 stereo and Sentinel-2 imagery to map the water depths of coral reef areas in the Xisha region of the South China Sea. Bathymetry data derived from photogrammetric and linear regression methods are compared to the reprocessed Ice, Cloud and land Elevation Satellite-2 (ICESat-2) data. We find that the linear regression method (root-mean-square-error, RMSE=0.60 m) outperforms photogrammetry (RMSE=1.02 m), and the higher resolution WorldView-2 data yields less systematic biases than Sentinel-2 data. Considering that water depths reflect changes in temperature and light, which are critical factors influencing coral reef distribution, we propose to use satellite-derived bathymetry as a feature for coral reef classification. We demonstrate that combining topography and spectral information can improve the overall mapping accuracy, particularly for compositions characterised by sharp boundaries.
Conjunctive management strategies of groundwater and surface Water: a case study of meinong reservoir in Taiwan
Authors: Lai Cai Chun , Lin Yuan Chien
Published: March 2024

Water is an essential natural resource for human survival and development. In recent years, global climate change has led to noticeable shifts in rainfall patterns. In Taiwan, the gap between wet and dry years has gradually widened, and rainfall has become shorter in duration but more intense. This has increased the frequency of spring droughts in Taiwan. Hence, there is an urgent need to propose a new water utilization model.The bucket model is employed to estimate parameters that are challenging to measure, while Bayesian networks are utilized to establish causal relationships among environmental factors. In addition, Bayesian Network is a systematic network based on conditional probability for constructing relationships between factors. It has been shown to capture crucial groundwater flow properties and uncertainties in groundwater systems. This study seeks to alter the previous management strategy, which prioritized the use of surface water during the rainy season. Consequently, two distinct theoretical models were established for comparison. Model 1 gives precedence to surface water usage, whereas Model 2 prioritizes groundwater usage. Compare the remaining water in surface and groundwater before the next rainy season. The results indicate that, under 'high' conditions, the capacity of groundwater and surface water in Model 2 will be 18% greater than in Model 1. This is attributed to groundwater resources flowing to the surface or serving as a source of submarine groundwater discharge due to saturated aquifers. Additionally, Bayesian networks were employed to conduct a sensitivity analysis of factors. The two most influential factors on the target node are rainfall and groundwater inflow and outflow from the outside area.
Sensitivity analysis of streamflow responses to varied rainfall spatial patterns in small tropical watersheds
Authors: Huang Yu-Fen , Tsang Yinphan
Published: March 2024

Flash floods, characterized by rapid streamflow response to rainfall, pose a significant natural hazard, particularly in small tropical watersheds (< 40 km2). Understanding the role of rainfall event characteristics, including amount, intensity, and spatial structure, is crucial for addressing and predicting flash floods. This study employs the WRF-Hydro® model with high-resolution (250-m, hourly) rainfall data and the Random Balance Designs – Fourier Amplitude Sensitivity Testing (RBD-FAST) method to investigate how rainfall impacts streamflow, specifically peak flow events, in seven watersheds on Oʻahu, USA.Analyzing storm events from 2015 to 2020, we examined peak flow responses to corresponding rainfall event characteristics and estimated their contributions to model efficiency. In addition, (1) random redistribution of rainfall and (2) spatial shifting of rainfall were experimented with to assess the sensitivity of peak flow to rainfall event characteristics. Not only the rainfall amount and intensity but heavy rainfall areas (>= 25 mm) within an event also exerted a significant impact on peak flow, while other spatial features contributed varying degrees of influence. Notably, spatially shifting rainfall for at least 250-m in any direction highly affected event peak streamflow, emphasizing the importance of rainfall amount, intensity, heavy rainfall areas, total rainfall areas, and connectivity among rainfall areas.Given the significance of rainfall's spatial heterogeneity, these findings underscore the benefits of incorporating rainfall spatial characteristics in probabilistic flood forecasting and the mitigation of flood risks. This research contributes valuable insights for enhancing flood prediction strategies in small tropical watersheds, providing a basis for informed decision-making and risk management.
A new method for constraining crustal Vp/Vs ratio using P and S wave multiples
Authors: Meng Fanchang , Yu Chunquan , Zeng Xianwei
Published: March 2024

The ratio between compressional and shear wave speeds (Vp/Vs) in the Earth's crust is crucial for gaining a better understanding of its chemical composition and geological evolution history. Many studies employed H-κ stacking of receiver functions to estimate the crustal Vp/Vs ratio. However, the Vp/Vs ratio obtained from H-κ stacking can be biased due to lateral variations in crustal structures and/or incorrect absolute wave speed assumption. In this study, we propose a novel method to estimate the crustal Vp/Vs ratio using P and S wave multiples near receivers, that is the PpPmp (where m represents the Moho) and SsSms phases. The absolute arrival times of PpPmp and SsSms are sensitive to crustal thickness and wavespeeds, but the ratio of their arrival times is most sensitive to the crustal Vp/Vs ratio. We first verify the new method using synthetic tests on various crustal models. Synthetic results show that in the presence of lateral variation in crustal structure, the new method gives more accurate Vp/Vs ratios than the conventional H-κ stacking of receiver functions. We further validate the new method using field data recorded by the broadband station HYB in the eastern Dharwar Craton. Our data analysis involved preprocessing and manual selection of teleseismic events. Ultimately, the observed PpPmp and SsSms phases from 351 teleseismic events were used to calculate the Vp/Vs ratio beneath the HYB station, resulting in a value of 1.737±0.016. We find that this value is comparable to research results obtained by previous researchers using receiver function inversion (Zhou et al., 2000). Our new method for estimating crustal Vp/Vs ratio can potentially to applied to many other regions of tectonic importance.This study is supported by National Natural Science Foundation of China (43/K22431006).
Addressing validation challenges for TROPOMI solar-induced chlorophyll fluorescence products using tower-based measurements and an NIRv-scaled approach
Authors: Du Shanshan , Duan Weina , Liu Liangyun
Published: March 2024

Several satellite-based solar-induced chlorophyll fluorescence (SIF) products have progressively emerged and have been developed in recent years. However, till date, no direct validation has been conducted on existing satellite-based SIF products. In this study, validation of two groups of TROPOspheric Monitoring Instrument (TROPOMI) SIF products, namely TROPOSIFCaltech (containing far-red and red TROPOSIFCaltech datasets) and TROPOSIFESA (containing TROPOSIF735 and TROPOSIF743 datasets that are retrieved from two different retrieval windows), was conducted using tower-based SIF measurements over seven sites. Several issues and potential obstacles emerged while matching satellite-based and in situ SIF retrievals, including spatial scale mismatch. To overcome the spatial scale mismatch between the satellite data and ground observations, a near-infrared reflectance of vegetation (NIRv)-scaled approach was employed to mitigate the spatial difference between the locations of specific sites and the matched TROPOSIF samples using Sentinel-2 imagery. Other issues related to retrival methods and instrument differences were examined. Subsequently, the 3FLD retrieval method was chosed for the in situ data. The validation results showed that the three far-red TROPOSIF datasets exhibit slightly different performances in terms of the validation accuracy; the R2 for TROPOSIFCaltech, TROPOSIF735, and TROPOSIF743 was 0.43, 0.33 and 0.40, respectively, which is asociated with root-mean-square error(RMSE) values of 0.59, 0.42 and 0.57 mW m−2 sr−1 nm−1, respectively. However, red TROPOSIFCaltech exhibited no significant correlation with tower-based SIF with R2 of 0.02 and RMSE of 0.34 mW m−2 sr−1 nm−1. Furthermore, the validation results at different sites varied, with R2 ranging from 0.01 to 0.70. Uncertainties still exist in the validation of the four TROPOSIF datasets, which are attributed to some unresolved issues, such as the limited quality of in situ SIF retrievals and the spatial scaling difference. Thus, to fully utilize satellite-based SIF products for wide ranging applications, further improvements in SIF product quality are urgently required at both ground and satellite scales.
Geochemical characterization of Anatolian tephras from Late Middle and Early Upper Palaeolithic sites in the Jebel Qalkha area, southern Jordan
Authors: Zhang Shuang , Blockley Simon , Harman Naima , Manning Christina , White Dustin , Timms Rhys , Kadowaki Seiji
Published: March 2024

The Middle to Upper Palaeolithic transition in the Levant is characterized by key archaeological shifts, including the interaction between Neanderthals and AMH and the appearance and dispersal of the Upper Palaeolithic. During this period there is also potential for abrupt climatic transitions to influence the distribution of humans across the region. One issue is the precision and resolution to which we can date Levantine archaeological sites and the wider environmental record. Ongoing studies have demonstrated that archaeological sites in this region receive volcanic ash horizons (tephra), which can be utilised as a tool to provide chronological markers to date archaeological sites and to link them to important palaeoclimate records (Barzilai et al., 2022).Here we present the detailed cryptotephra stratigraphic profiles from two Jordanian archaeological sites in the Jebel Qalkha area, one Early Upper Palaeolithic (EUP) to Epipalaeolithic site – Tor Hamar, and another Late Middle Palaeolithic (LMP) site – Tor Faraj. The data include tephra shard concentrations in different cultural layers. We also present new major and trace element geochemical data that trace the majority of these tephra layers to Anatolian volcanic centres. This allows existing radiometric ages for some of these tephra to provide additional age constraints in these archaeological sites. Our data show the potential for sites in this region to be correlated into Anatolian and Aegean volcanic records and distal environmental records from marine cores and the Dead Sea sequence (Kearney et al., 2022). This would allow further underpinning of studies that link environmental change with early human adaptations in the region. Barzilai, O., Oron, M., Porat, N., White, D., Timms, R., Blockley, S., Zular, A., Avni, Y., Faershtein, G., Weiner, S. and Boaretto, E., 2022. Expansion of eastern Mediterranean Middle Paleolithic into the desert region in early marine isotopic stage 5. Scientific reports, 12(1), p.4466.Kearney, R., Schwab, M. J., Neugebauer, I., Pickarski, N., and Brauer, A.: The TephroMed project: Precise synchronising of two key palaeoclimatic ICDP records of the eastern Mediterranean using tephra, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-468, https://doi.org/10.5194/egusphere-egu22-468, 2022.
Spontaneous Formation of Mantle Wind by Subduction and Its Impacts on Global Subduction Asymmetry
Authors: Lee Youngjun , Lee Changyeol
Published: March 2024

Various subduction zone characteristics, including the slab dip, plate velocity, seismicity, and back-arc stress regime, show the global asymmetry with respect to the subduction direction. In particular, the east-directed subducting slabs show shallow dips and slow convergences, contrast to the steep dips and fast convergences of the west-directed subducting slabs. To explain the global asymmetry, the westward lithospheric motion or the eastward mantle wind with respect to the underlying mantle and the overlying plate, respectively, have been proposed. However, the causative force for the lithospheric motion, the tidal force between the Earth and Moon, is only acceptable when the asthenospheric viscosity is dramatically low such as 1015 ~ 1016 Pa·s, which could not globally exist in the mantle. The causative force for the mantle wind has left unknown even though the impact of the mantle wind has been verified. Past studies have shown that slabs sinking into the lower mantle can cause global mantle flow. That is, the slabs sinking at the eastern and western trenches around the Pacific ocean can cause the global mantle flow above the low-viscosity liquid outer core, expressed as the mantle wind. Therefore, to verify whether the subducting slabs around the Pacific ocean cause the mantle wind, we conducted a series of 2-D numerical models using an annulus-shape model domain, which simplifies the subduction history in the paleo- and present-Pacific ocean. Along with an allowance of dynamic subduction, both the realistic mantle viscosity and the major phase transition in the mantle were considered. Results show that the global-scale mantle wind is spontaneously formed by the imbalance in lateral mantle stresses owing to the subducting slabs around the Pacific ocean when the slippery core-mantle boundary operates as a lubricant layer, and the direction and magnitude of the mantle wind are periodically changed every tens of million years. When he eastward mantle wind occurs, it induces the relative westward drift of the plate, and as a result, the westward plate velocity becomes greater than the eastward plate velocity with respect to the hotspot reference frame. Simultaneously, the mantle wind pushes the west-directed subducting slab toward the ocean, forming steep slab dips but does the east-directed subducting slab toward the arc, forming shallow slab dips, consistent with the present subduction asymmetry in the Pacific ocean. After that, the negative buoyancy of the shallow slab steepens the slab itself, changing the direction of mantle wind westward; the opponent slab dips and plate velocities occur in the subduction zones. This study reveals that the present subducting asymmetry is a snapshot expression of the evolving global mantle flow, formed by the subducting slabs.
Observation of intraplate repeating earthquakes within the fault zone of the 2008 ML 3.6 earthquake
Authors: Jung Seula , Sheen Dong-Hoon , Cho Chang-Soo , Kim Kwangsu
Published: March 2024

The repeating earthquake (RE) ruptures a single fault patch repeatedly and generates highly similar waveforms. The RE is often observed in the area of subduction zones (Uchida and Matsuzawa, 2013; Yu et al., 2013; Uchida, 2019). However, even in the intraplate region, the RE has been found in the ruptured fault zones (Li et al., 2007; Li et al., 2011; Bisrat et al., 2012). We searched for REs around the epicenter of the 2008 ML 3.6 Gyerong earthquake that occurred in Mount Gyeryong, the Korean Peninsula, located in a stable intraplate region. In the study area, 48 earthquakes (ML 0.4–3.6) were reported during 2002–2022, while we found 50 earthquakes during 2018–2022 using a template matching. We located the events based on the Hypoellipse (Lahr, 1999), and also refined the hypocenters using the double difference method (hypoDD; Waldhauser and Ellsworth, 2000) to obtain the high-resolution fault geometry. It is found that the epicenters exhibit a linear alignment of the fault striking along WNW-ESE consistent with one of the strikes of the ML 3.6 event which has a strike-slip focal mechanism with a strike of 108° or 198°, a dip of 83° or 88°, and a rake of -2° or -173°, which indicates that the ML 3.6 earthquake occurred with a left-lateral fault slip. We estimated the rupture directivity of the ML 3.6 event from the apparent source time functions obtained by the empirical Green’s function approach. A vast number of microearthquakes including aftershocks of the ML 3.6 event occurred in the rupture direction (i.e. the east-southeast of the epicenter of the ML 3.6 event). We identified REs based on the waveform similarity (cross-correlation coefficient > 0.95) and their locations (co-location) to distinguish them from neighboring earthquakes. We found that the REs occurred within the rupture radius of the ML 3.6 event. Upon categorizing these REs according to their family duration, we identified three swarm-type families that occurred in 2007, 2009, and 2010, along with a continuous-type family spanning from 2011 to 2019. These observations demonstrate the close relationship between the REs and the ML 3.6, specifically highlighting the fault’s rupture and healing process.