•Validation of eight Satellite-derived Precipitation Estimate (SPE) over Vietnam.•SPE datasets included uncorrected and gauge-corrected products.•GPM IMERGF-V6 achieved the best overall performance ...among SPE datasets.•There is a confidence for using SPE in determining monthly streamflow in large river basins.
This study evaluates eight Satellite-derived Precipitation Estimate (SPE) datasets, which include uncorrected SPE and gauge-corrected SPE products from Tropical Rainfall Measurement Mission Multi-satellite Precipitation Analysis (TMPA), Global Precipitation Measurement (GPM), Climate Hazards group Infrared Precipitation (CHIRP), and Precipitation Estimation form Remotely Sensed Information using Artificial Neural Networks (PERSIANN). These datasets are utilized with six representative river basins, corresponding to six sub-climate zones in Vietnam, during the period 2002–2017. The evaluations were carried out in two parts: 1) inter-comparison of the SPE products with rain gauges, for the six basins; 2) comparison of streamflow simulations, using the Soil and Water Assessment Tool (SWAT) forced by precipitation from rain gauge and SPE products. The results indicated that the gauge-corrected SPE datasets exhibited slightly better over the uncorrected datasets in comparison with rain gauges, but showed much higher performances as inputs in hydrological simulations. The GPM Integrated Multi-satellitE Retrievals for GPM (IMERG) Final run version 06B (GPM IMERGF-V6) exhibited the best overall performances among SPE products, in comparison with the rain gauges for the simulation of streamflow. This study is the first of its kind to validate GPM IMERG products in Vietnam, indicating the strong capability of the new IMERG retrieval algorithms. The CHIRP with stations (CHIRPS) dataset demonstrates a relatively low bias, could benefit long-term water resources planning for droughts. In monthly streamflow simulations, the SPE-driven simulations outperformed rain gauge-driven simulations in a larger basin (North West Region), which has low rain-gauge density. The results of this study could be a guide to determine the suitability of different SPE products for hydrological simulations.
•This study tackles the challenge of unbalanced stream gauge distributions by leveraging publicly available datasets and deep learning to enhance hydrological modeling in under-gauged ...regions.•Thisstudy introduces a novel framework combining LSTM-based deep learning with GLDAS and GSIM data for effective runoff prediction across continents.•This study assesses the sensitivity of LSTM models using data from diverse regions, emphasizing the importance of hydrological similarities for accurate runoff predictions in ungauged basins.•LSTM models demonstrate superior runoff prediction skills over traditional GLDAS datasets, influenced by the hydrological similarities between training and test regions.
This study introduces a framework that strategically applies a Long Short-Term Memory (LSTM)-based approach for monthly runoff prediction in South Africa and Central Asia. The framework is distinct in its utilization of newly developed Global Land Data Assimilation System (GLDAS)-derived climate dynamics variables and Global Streamflow Indices and Metadata Archives (GSIM)-derived static descriptors, ensuring a consistent evaluation of Deep Learning (DL) performance across multiple continents, including North and South America, and Western Europe. Seven LSTM models were trained using seven different datasets, each representing a combination of these data-rich regions. We assessed the sensitivity of these seven training data sets to LSTM models by testing these trained models in predicting monthly basin-scale runoff across 214 test catchments located in South Africa and Central Asia. Our results show that runoff predictions generated by LSTM within the test domain could exhibit better prediction skills compared to those derived from GLDAS datasets. The performance of the trained LSTMs appears to be linked to hydrological similarities between the data-rich regions and the test basins. Also, our results indicate the importance of selecting the appropriate input sources for the LSTM models to achieve accurate runoff predictions at the test region. We emphasize the possibility of utilizing LSTM models that are leveraging on either North American catchments or a combination of South American and Western European catchments to predict basin-scale runoff in the test regions. To this end, this study harnesses the burgeoning availability of publicly stream-gauge datasets and DL to enhance water information prediction in ungauged regions, responding to the challenge of geographically unbalanced stream gauge instruments.
This paper presents insights on the thermodynamics and kinetics of the cobalt electronucleation and growth mechanisms onto glassy carbon electrode from a eutectic mixture of choline chloride and ...urea. The behavior of the current density transients can be described by a model capable of considering the cobalt three-dimensional nucleation and diffusion-controlled growth from metallic nuclei and the induction-time. Using the proposed model, typical kinetic parameters such as nucleation frequency A, number density of nuclei, N0, and diffusion coefficient, D, were determined at different temperatures and applied potentials. It was found that the residual water has some effects on the early stage of the Co electrodeposition, especially on the nucleation types. Thus, at low temperature it is predominant by progressive nucleation, while at high temperature it is governed by instantaneous nucleation mechanism. Furthermore, from the temperature-dependent relationship of the diffusion coefficient, the Gibbs free energy for cobalt nucleation in DES was able to be estimated.
•Mechanisms and kinetics of cobalt nucleation and growth from DES were investigated.•Chemical species of DES containing Co (II) were established using UV–vis spectra.•A model comprising (3D) nucleation and growth and induction-time was proposed.•Gibbs free energy for nucleation was determined through a model fitting method.
In this paper, a novel material based on Er-Yb-Mo tri-doped HA/β-TCP phosphor for intense green up-conversion (UC) emission was successfully synthesized by solid-state reaction method. X-ray ...diffraction (XRD) measurements verified that the materials including a trace amount of HA phase has a hexagonal structure and main β-TCP phase has a rhombohedral structure, which is controlled by the doped ions. Under excitation wavelength of 976 nm laser diode, the HA/β-TCP:Er-Yb-Mo phosphor showed strong green UC emission band at 520/556 nm and weak red emission band at 656 nm which are attributed to (2H11/2, 4S3/2) - 4I15/2, 4F9/2 - 4I15/2 transition of the Er3+ ion, respectively. Remarkably, compared with the sample without Mo6+, the green emission intensities increased ∼650 times was achieved by using Er3+-Yb3+-Mo6+ doped phosphor. The high efficiency of the UC can be attributed to novel energy transfer process from |2F7/2, 3T2> state of Yb3+ - MoO42− dimer to the 4F7/2 of Er3+ ions. Moreover, the grain orientations due to the effect of Mo6+ ions doped in β-TCP phosphor could play an important role in the enhancement of UC emission intensity. These results indicate that the HA/β-TCP: Er-Yb-Mo phosphor has potential application in biological imaging and medicine.
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•Novel upconversion material (Er-Yb-Mo tri-doped HA/β-TCP phosphor) was facilely synthesized by solid-state reaction method.•The crystalline single – phase of β-TCP was achieved by doping with Mo6+ ions.•The green emission intensity of the sample doped with Mo was 650 times higher compared with the sample without Mo.•The selective green upconversion emission can be controlled by controlling the doping Mo6+ concentration in HA/β-TCP: Er3+-Yb3+.
The Vietnamese Mekong Delta (VMD) is located in Vietnam
The Vietnamese Mekong Delta (VMD) region has one of the leading productions of rice in the world and it stands at the intersection of extreme ...anthropogenic activity and climate change. To this end, the major focus of this study is to explore the changes in land use, climate, water resources, and their inter-relationship, which are intended to showcase the ability of publicly available earth observations and models in improving understanding of the past changes and future scenarios and contribute to improved decision making. We analyzed the change of agricultural crops (single, double, and triple) and climatic parameters (precipitation, and land surface temperature, and evapotranspiration). Consequently, we used Soil and Water Assessment Tool Model (SWAT) and selected six GCMs for extreme climate to investigate the change of streamflow.
Our results indicated that double rice crop and aquaculture are the top two land use categories in the VMD, the areas of triple rice crop have increased significantly, especially for the An Giang and Dong Thap provinces. However, by examining the climate, water, and land data analytics, we see challenges in the expansion of triple rice crop over VMD. The spatio-temporal changes in climate variables and future streamflow projections provide strong evidence to water resources managers and decision-makers in the VMD.
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•The areas of triple rice crop have increased significantly (2000–2018).•Trend of climatic variables (precipitation, temperature, and ET) are analyzed.•We selected extreme climatic scenarios for future projection on the VMD.•We simulated the projected streamflow due to extreme climatic conditions.
Middle East.
Droughts are a major natural disaster in almost every region of the world, causing negative impacts on natural resources and water basin management. However, it is challenging to study ...drought mechanisms in transboundary rivers where hydrometeorological observations are often not available or limited due to administrative issues. This study aims to assess drought conditions at three Iraqi transboundary river basins – (a) Mosul River Basin (between Iraq and Turkey), (b) Qadisiyah River Basin (between Iraq, Syria and Turkey), and (c) Dukan River Basin (between Iraq and Iran). The Famine Early Warning Systems Network Land Data Assimilation System (FLDAS) and satellite datasets have been used to calculate various drought indices and reservoir areas for the study period between 1987 and 2019.
We exhibited the usefulness of FLDAS and satellite datasets in analyzing the variations and trends in hydro-meteorological variables and reservoirs surface areas over three transboundary river basins. Results exposed a significant drought exacerbation over the study regions during the periods of 1989–1991, 2000–2003, 2007–2012, and 2015–2018. Based on our analysis on drought duration and severity for inside- and outside- Iraq, we suggest the long-term meteorological drought indices (12-,24-month timescales) in monitoring drought conditions. Our results could be beneficial for water and natural resources managers in understanding spatial variability and impact of droughts.
•Evaluation of ten different drought indices•Understanding of drought conditions based on administrative boundary•Study on three transboundary river basins across different climactic conditions
The use of satellite–based precipitation products (SPPs) have become increasingly prevalent as key inputs to provide regional rainfall for improving hydrological simulations in data–spare regions. ...This study introduces a new approach – Comprehensive Assessment Framework of Rainfall (CAFR) to evaluate six satellite–based precipitation products (SPPs) for eleven basins with different sizes across Vietnam (2007–2015). These SPPs include the Global Precipitation Mission (GPM) Integrated Multi-satellitE Retrievals for Global Precipitation Measurement Final run Version 6 (GPM IMERGF V6), Multi–Source Weighted–Ensemble Precipitation (MSWEP) V2.2, Soil Moisture to Rain (SM2RAIN) – Advanced SCATterometer (ASCAT) V1.5, Asian Precipitation–Highly–Resolved Observational Data Integration Towards Evaluation (APHRODITE) V1901, Climate Hazards group Infrared Precipitation with Stations (CHIRPS) V2.0, and Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN) – Climate Data Record (CDR) V1.0. With the proposed CAFR: (1) IMERGF is suggested to have the best performance overall, especially when simulating flood peaks; (2) SM2RAIN–ASCAT demonstrates the best skills in metrics related to the dry season; (3) For streamflow simulations, SPPs' performance is sensitive to basin size, with larger basins showing better performance skills. In this study, we demonstrate the capability of our proposed framework to better understand SPP applications in hydrological modeling.
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•A novel framework, namely the Comprehensive Assessment Framework of Rainfall (CAFR), is proposed.•IMERGF exhibits the best overall performance while PERISANN–CDR is the poorest.•SM2RAIN–ASCAT performs better than other rainfall products for drought detection during dry season.•A relationship is found between rainfall products' performances and watersheds' area.
The crust near an extinct mid‐ocean ridge provides unique constraints on how its accretion and deformation responded to the cessation of spreading. Here we present crustal thickness and Vp/Vs ...measurements beneath 11 Ocean Bottom Seismograph sites that cross the South China Sea's extinct spreading axis. We find that the oceanic crust, which generally had only slight thickness changes once spreading started, abruptly thins at sites close to the extinct ridge axis. Abnormally high Vp/Vs ratios are obtained at several sites south of the ridge, indicating the presence of serpentine. These observations imply that, in its final stage, spreading changed to an ultraslow accretion style. As the axial crust thinned, normal faults and/or detachment faults began to form. Water could penetrate more deeply through these faults, and large fault slip could raise ultramafic peridotites to near or at the seafloor, creating favorable conditions for their enhanced serpentinization.
Plain Language Summary
Mid‐ocean ridges can both form and die. As a ridge dies, what happens to melt generation beneath the ridge axis? Clues exist in the oceanic crust near an extinct ridge that was created during the ridge's final stages of seafloor spreading. We explore a well‐known extinct spreading center within the South China Sea. Using ocean bottom seismometers and the receiver function technique, we determine the thickness of the magmatic crust, and a parameter (Vp/Vs) that reflects the structure of the underlying crust. We find that, approaching the extinct spreading axis, the crust, typically uniform in thickness, thins significantly. This indicates that the melt supply decreases relative to spreading rate during the final stages of spreading. The Vp/Vs ratio at three sites nearest to the extinct spreading axis is abnormally high. Our inference is that the spreading rate and magma production has decreased to the point where large crustal faults can develop at several locations along the ridge. These faults provide pathways for seawater to reach and react with the uppermost mantle, forming minerals with higher Vp/Vs ratios which are then uplifted to the seafloor as the faults grow.
Key Points
Ocean Bottom Seismograph receiver functions constrain crustal structure near the extinct ridge of the South China Sea
Thinned crust indicates reduced spreading rate and magma supply during the final stage of spreading
Anomalously high Vp/Vs ratios are likely due to serpentine along faults formed in response to slowing spreading
Abstract
Background
High-resolution anorectal manometry (HRAM) has been developed to improve measurement of anorectal functions. This study aims to identify normal HRAM values in healthy young ...Vietnamese adults.
Methods
We conducted a cross-sectional study at the National Hospital of Traditional Medicine (Hanoi, Vietnam) from July through December 2014. Healthy young adults were invited to participate in the study. All anorectal measurement values were performed using the ISOLAB high-resolution manometry system. Differences between groups were analyzed using Student’s t-tests.
Results
Thirty healthy young adults, including 15 males and 15 females aged 19–26 years, were recruited. Mean functional anal canal length was 3.4 ± 0.5 cm (range: 2.4–4.8 mm). Mean maximum resting pressure, mean maximum squeezing pressure, mean maximum coughing pressure, and mean maximum strain pressure were 65.5, 168.0, 125.9, and 84.2 mm Hg, respectively. All anal pressure values were significantly different between males and females. For rectal sensation measurements, only the volume at first sensation was significantly higher in males than in females.
Conclusions
This study provides normal HRAM value for healthy young adults in Vietnam. Sex may influence anal pressure and first rectal sensation values in this cohort. Further studies should be conducted in order to improve the quality of HRAM normal values and to confirm the effects of sex.
Streamflow is one of the key variables in the hydrological cycle. Simulation and forecasting of streamflow are challenging tasks for hydrologists, especially in sparsely gauged areas. Coarse spatial ...resolution remote sensing soil moisture products (equal to or larger than 9 km) are often assimilated into hydrological models to improve streamflow simulation in large catchments. This study uses the Ensemble Kalman Filter (EnKF) technique to assimilate SMAP soil moisture products at the coarse spatial resolution of 9 km (SMAP 9 km), and downscaled SMAP soil moisture product at the higher spatial resolution of 1 km (SMAP 1 km), into the Soil and Water Assessment Tool (SWAT) to investigate the usefulness of different spatial and temporal resolutions of remotely sensed soil moisture products in streamflow simulation and forecasting. The experiment was set up for eight catchments across the tropical climate of Vietnam, with varying catchment areas from 267 to 6430 km^2 during the period 2017–2019. We comprehensively evaluated the EnKF-based SWAT model in simulating streamflow at low, average, and high flow. Our results indicated that high-spatial resolution of downscaled SMAP 1 km is more beneficial in the data assimilation framework in aiding the accuracy of streamflow simulation, as compared to that of SMAP 9 km, especially for the small catchments. Our analysis on the impact of observation resolution also indicates that the improvement in the streamflow simulation with data assimilation is more significant at catchments where downscaled SMAP 1 km has fewer missing observations. This study is helpful for adding more understanding of performances of soil moisture data assimilation based hydrological modelling over the tropical climate region, and exhibits the potential use of remote sensing data assimilation in hydrology.
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