bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Evolution of a Meiyu Frontal Rainstorm Based on Doppler Radar Data Assimilation
Authors: Li Hongli , Hu Yang , Zhou Zhimin
Published: March 2020

During the Meiyu period, floods are prone to occur in the middle and lower reaches of the Yangtze River due to the highly concentrated and heavy rainfall, which caused huge life and economic losses. Based on numerical simulation by assimilating Doppler radar, radiosonde, and surface meteorological observations, the evolution mechanism for the initiation, development and decaying of a Meiyu frontal rainstorm that occurred from 4th to 5th July 2014 is analyzed in this study. Results show that the numerical experiment can well reproduce the temporal variability of heavy precipitation and successfully simulate accumulative precipitation and its evolution over the key rainstorm area. The simulated “rainbelt training” is consistent with observed “echo training” on both spatial structure and temporal evolution. The convective cells in the mesoscale convective belt propagated from southwest to northeast across the key rainstorm area, leading to large accumulative precipitation and rainstorm in this area. There existed convective instability in lower levels above the key rainstorm area, while strong ascending motion developed during period of heavy rainfall. Combined with abundant water vapor supply, the above condition was favorable for the formation and development of heavy rainfall. The Low level jet (LLJ) provided sufficient energy for the rainstorm system, and the low-level convergence intensified, which was an important reason for the maintenance of precipitation system and its eventual intensification to rainstorm. At its mature stage, the rainstorm system demonstrated vertically tilted structure with strong ascending motion in the key rainstorm area, which was favorable for the occurrence of heavy rainfall. In the decaying stage, unstable energy decreased, and the rainstorm no longer had sufficient energy to sustain. The rapid weakening of LLJ resulted in smaller energy supply to the convective system, and the stratification tended to be stable in the middle and lower levels. The ascending motion weakened correspondingly, which made it hard for the convective system to maintain.
A framework for quantifying the impacts of future climate and land use/cover changes on runoff in the Han River basin, China
Authors: Tian Jing , Guo Shenglian , Xu Chong-Yu
Published: March 2020

As a link between the atmosphere and the earth’s surface, the hydrological cycle is impacted by both climate change and land use/cover change (LUCC). For most basins around the world, the co-variation of climate change and LUCC will continue in the future, which highlights the significance to explore the temporal-spatial distribution and variation mechanism of runoff and to improve our ability in water resources planning and management. Therefore, the purpose of this study is to propose a framework to examine the response of runoff to climate change and LUCC under different future scenarios. Firstly, the future climate scenarios under BCC-CSM1.1 and BNU-ESM are both downscaled and bias-corrected by the Daily bias correction (DBC) method, meanwhile, the future LUCC scenarios are predicted by the Cellular Automaton-Markov (CA-Markov) model according to the integrated basin plans of future land use. Then, based on the baseline scenario S0 (meteorological data from 1966 to 2005 and current situation LUCC2010), the following three scenarios are set with different combinations of future climate land-use situations, i.e., S1: only climate change scenario; S2: only the LUCC scenario; S3: climate and LUCC co-variation scenario. Lastly, the Soil and Water Assessment Tool (SWAT) model is used to simulate the hydrological process and quantify the impacts of climate change and LUCC on the runoff yield. The proposed framework is applied to the Han River basin in China. Results show that: (1) compared with the base period (1966-2005), the annual rainfall, daily maximum, and minimum air temperature during 2021-2060 will have an increase of 4.0%, 1.8℃, 1.6℃ in RCP4.5 while 3.7%, 2.5℃, 2.3℃ in RCP8.5, respectively; (2) from 2010 to 2050, the forest land and construction land in the Han River basin will have an increase of 2.8% and 1.2%, respectively, while that of farmland and grassland will have a decrease of 1.5% and 2.5%, respectively; (3) comparing with the single climate change or LUCC scenario, the co-variation scenario possesses the largest uncertainty in runoff projection. Under the two concentration paths, there is a consistent upward change in future runoff (2021-2060) of the studied basin compared with that in the base period, furthermore, the increase rate in RCP4.5 (+5.10%) is higher than that in RCP8.5 (+2.67%). The results of this study provide a useful reference and help for water resources and land use management in the Han River basin.
Drifting Electron Holes Occurring During Geomagnetically Quiet Times: BD-IES Observations
Authors: Liu Zhi-Yang , Zong Qiu-Gang , Zou Hong
Published: March 2020

Drifting electron holes (DEHs), manifesting as sudden but mild dropout in electron flux, are a common phenomenon seen in the Earth's magnetosphere. It manifests the change of the state of the magnetosphere. However, previous studies primarily focus on DEHs during geomagnetically active time (e.g., substorm). Not until recently have quiet time DEHs been reported. In this paper, we present a systematic study on the quiet time DEHs. BeiDa Imaging Electron Spectrometer (BD-IES) measurements from 2015 to 2017 are investigated. Twenty-two DEH events are identified. The DEHs cover the whole energy range of BD-IES (50–600 keV). Generally, the DEHs are positively dispersive with respect to energy. Time-of-flight analysis suggests the dispersion results from electron drift motion and gives the location where the DEHs originated from. Statistics reveal the DEHs primarily originated from the postmidnight magnetosphere. In addition, superposed epoch analysis applied to geomagnetic indices and solar wind parameters indicates these DEH events occurred during geomagnetically quiet time. No storm or substorm activity could be identified. However, an investigation into nightside midlatitude ground magnetic records suggests these quiet time DEHs were accompanied by Pi2 pulsations. The DEH-Pi2 connection indicates a possible DEH-bursty bulk flow (BBF) connection, since nightside midlatitude Pi2 activity is generally attributed to magnetotail BBFs. This connection is also supported by a case study of coordinated magnetotail observations from Magnetospheric Multiscale spacecraft. Therefore, we suggest the quiet time DEHs could be caused by magnetotail BBFs, similar to the substorm time DEHs.
On the Rainfall Induced Shallow and Deep-seated Landslide Hazard in Central Taiwan
Authors: Shou Keh-Jian
Published: March 2020

Due to active tectonic activity, the rock formations are young and highly fractured in Taiwan area. The dynamic changing of river morphology makes the highly weathered formations or colluviums prone to landslide and debris flow. In addition, due to the impact of 1999 Chi-Chi earthquake, the hazards of landslides and debris flows were significantly increased. For the past decade, the effect of climate change is significant and creates more and more extreme weather events. The change of rainfall behavior significantly changes the landslide behavior, which makes the large-scale landslides, like the Shiaolin landslide, possible. Therefore, it is necessary to develop the new technologies for large-scale landslide investigation, monitoring, analysis, early warning, etc.

Since the landslide hazards are mainly induced by heavy rainfall, due to climate change and the subsequent extreme weather events, the probability of large-scale landslides is also increased. Focusing on the slate formation area in the upstreams of the Tachia River, Wu River, and Chuoshui River, this project studied the behavior and hazard of shallow and deep-seated landslides. This study adopts the SHALSTAB model with the consideration of slope angle to classify the landslides, and then established the landslide susceptibility models based on the classified landslide inventories. Different types of susceptibility models in different catchment scales were tested, in which the control factors were analyzed and discussed. This study also employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to predict the extreme rainfalls in the future. Such that the future hazard of the shallow and deep-seated landslide in the study area can be predicted. The results of predictive analysis can be applied for risk prevention and management in the study area.
Diagnostic efficiency - a diagnostic approach for model evaluation
Authors: Schwemmle Robin , Demand Dominic , Weiler Markus
Published: March 2020

A better understanding of what is causing the performance of hydrological models to be “poor” or “good” is crucial for a diagnostically meaningful evaluation approach. However, current evaluation efforts are mostly based on aggregated efficiency measures such as Kling-Gupta Efficiency (KGE) and Nash-Sutcliffe Efficiency (NSE). These aggregated measures allow to distinguish between “poor” and “good” model performance only. Especially in case of “poor” model performance it is important to identify the errors which may have caused such unsatisfying simulations. These errors may have their origin in the model parameters, the model structure, and/or the input data. In order to provide insight into the origin of the error, we define three types of errors which may be related to the source of error: constant error (e.g. caused by consistent precipitation overestimation), dynamic error (e.g. caused by deficient vertical redistribution) and timing error (e.g. caused by precipitation or infiltration routine). Based on these types of errors, we propose the novel Diagnostic Efficiency (DE) measure, which accounts for the three error types by representing them in three individual metric components. The disaggregation of DE into its three metric components can be used for visualization in a 2-D space using a diagnostic polar plot. A major advantage of this visualization technique is that regions of error terms can be clearly distinguished from each other. In order to prove our concept, we first systematically generated errors by mimicking the three error types (i.e. simulations are calculated by manipulating observations). Secondly, by computing DE and the related diagnostic polar plots for the mimicked errors, we could supply evidence of the concept. Moreover, we tested our approach for a real case example. For this we used the CAMELS dataset. In particular, we compared streamflow simulations of a single catchment realized with different parameter sets to the observed streamflow. For this real case example the diagnostic polar plot suggests, that dynamic errors explain the model performance to a large extent. With the proposed evaluation approach, we aim to provide a diagnostic tool for model developers and model users. Particularly, the diagnostic polar plot enables hydrological interpretation of the proposed performance measure.
The Boundary Layer and its Response to External Forcing at Summit Station Greenland
Authors: Neff William , Cox Christopher , Shupe Mathew
Published: March 2020

The ICECAPS field program (Integrated Characterization of Energy, Clouds, Atmospheric State and Precipitation at Summit) has operated at Summit Station (over 3000 m ASL) since the spring of 2010 with a broad range of instruments to study the role of clouds and precipitation over the Greenland Ice Sheet (GIS).  In addition, a high-resolution minisodar has been operated nearby since 2008 (initially as part of an ice-atmosphere chemical exchange study).  The sodar provides detailed views of the thermodynamic structure of the boundary layer from 2 to 160 m above the surface. Several other collaborating programs support additional boundary-layer measurements such as broadband radiation and turbulent flux measurements. The sodar has proven useful in the interpretation of chemical interactions with the snow surface and underlying firn as well as comparisons of boundary layer depth estimators (Van Dam et al, 2013, 2015).  In addition it has documented the response of the boundary layer to changing cloud forcing (Shupe et al. 2013).  In addition, it has been used to study the wintertime boundary layer with super-cooled fog layers present (Cox et al, 2019).  Additional observations have added to an already rich data set, such as those of stable water vapor isotopes (e.g. Berkelhammer et al. 2016). 

As in the 2012 melt episode that encompassed nearly the entire ice sheet, atmospheric rivers (ARs) bring moisture from the south along the coasts of Greenland and have been increasing (Mattingly et al., 2018; Neff 2018).  We will present a climatology from 2000 to 2012 of ARs some of which are associated with increased transport of moisture from the subtropics at times in concert with hurricanes and tropical storms that follow the same path.  This climatology reveals a distinct low-high pressure pattern spanning from NE Canada to the central Atlantic: the boundary between these systems provides the pathway for moisture to flow from the subtropics.  In this presentation will describe the characteristic cloud/clear skies sequence and accompanying boundary layer structure at Summit Station during these events.  A typical sequence is one of ARs trapped along the west coast and then spreading moisture over the GIS in subsequent days.

To understand the origin of the moisture arriving at Summit Station we also carried out back trajectory analyses that show connections to both ARs and extratropical remnants of hurricanes that follow the same path to Greenland.  Of particular interest will be the boundary layer behavior during the dramatic melt episodes of June and then July 2019 that had their origins in heat waves off of Africa and over Europe. 

 
Interannual Variations of Summer Precipitation in Southwest China: Anomalies in the Moisture Transport and Roles of the Tropical Atlantic
Authors: Mengzhou Yang , Chaoxia Yuan , Wenmao Li , Yahan Zhong
Published: March 2020

Using a Lagrangian trajectory model, contributions of moisture from the Indian Ocean (IO), South China Sea (SCS), adjacent land region (LD) and Pacific Ocean (PO) to the interannual summer precipitation variations in Southwest China (SWC) are investigated. Results show that on average, IO, SCS, LD, and PO contribute 46.8%, 25.3%, 21.8% and 2.3% of total moisture release in SWC in summer. In the above-normal precipitation summers, the moisture from IO and LD is increased by 48.2% and 28.8%, whereas that from SCS is decreased by 37.2%. In the below-normal precipitation summers, the moisture from IO and LD is decreased by 34.6% and 25.2%, while that from SCS is increased by 23.7%. In addition, the moisture anomalies from the four source regions can explain 85% of the total variances of the SWC summer precipitation.

The variations in the moisture from IO, SCS, and LD to SWC are not independent to one another and strongly influenced by the large-scale atmospheric circulation anomalies in the lower troposphere analogous to the Pacific-Japan (PJ) pattern and further studies showed that the PJ pattern was stimulated by the SST anomaly in the equatorial Atlantic. The anomalous warming in the tropical Atlantic that can modify the Walker circulation and introduce an anomalous descending over the central Pacific, thus inducing the anomalous anticyclone in the western North Pacific as the classical Matsuno-Gill response. The resultant suppressed precipitation in the western North Pacific excites the PJ pattern. The observed impacts of the tropical Atlantic SSTs on the atmospheric circulation can be well reproduced in an atmospheric general circulation model and the ability of the CMIP5 and CMIP6 models to reappear this relationship is verified, which will help the models to improve the simulation performance of summer large-scale circulation anomalies and precipitation in East Asia.
How do shrubs impact the mass failures on the loess sidewall?
Authors: Gao, Hang , Xu Xiangzhou
Published: March 2020

The effects of plants on gravity erosion are still controversial, although vegetation has been widely used in soil and water conservation. In order to evaluate the influence of vegetation on gravity erosion, a series of laboratory experiments was performed on a 1.5-m-high loess-gully sidewall with a 70° slope, involving two types of shrubland (SL model) and bare land (BL model). The results revealed only an 8–20% decrease in total gravity erosion in the SL model compared to the corresponding BL model, which indicated that the impact of vegetation on gravity erosion is not significant. Compared with the BL model, the average landslide volume was 42% greater in the SL model, while the average avalanche and mudslide volumes in the SL model were 50% and 36% less, respectively. In addition, vegetation can change the type of gravity erosion and improve the degree of soil fragmentation. The amount of erosion after rain in the SL model was 33.17×103 cm3 more than that in the BL model. Compared with the anchoring effect of vegetation, the change of soil water caused by vegetation on the slope has a greater effect on the gravity erosion under heavy rains. It is suggested that the shrub restoration measures can be used in the areas with frequent debris flow and hydraulic erosion, and structural measures may reduce the negative impact of plants on gravity erosion of the Loess Plateau.
Sources and cycling of dissolved black carbon (DBC) in rivers and ocean revealed by carbon isotopes
Authors: Wang Xuchen
Published: March 2020

Abstract

Dissolve black carbon (DBC) has been recently recognized as an important fraction of dissolved organic carbon (DOC) in both rivers and ocean. It is estimated that about 10% of the riverine DOC transported by the world rivers could be DBC. The sources and fate of DBC in both rivers and ocean, however, is not well known. In this study, we present radiocarbon (14C) and stable carbon isotope (13C) measurements of DBC in several large rivers in China, and in coastal and open ocean waters. DBC was concentrated using solid phase extraction (SPE) method and quantified by chemothermal oxidation (CTO) method.

Concentrations of DBC varied in rivers depending on the drainage basin of the river and accounted for 3.7-7.6% of the riverine DOC pool. DBC was slightly lower, accounted for 2.9-5.9% of DOC in coastal and open oceans. Carbon isotope results indicate that DBC δ13C values were all slightly enriched (by 2-3‰) than the values of DOC in both rivers and ocean. The DBC Δ14C values varied largely in rivers and the values were significantly higher than DOC Δ14C values in rivers but similar to DOC Δ14C values in the ocean. Using a two-end member isotope mass balance model, we calculated that the most DBC (80%) with relatively young 14C ages in the rivers was derived from biomass burning. Laboratory incubation studies also found that DBC released from recent charcoal was able to be utilized by bacteria, supporting the speculation that river transported DOC could be decomposed during estuaries mixing. Our study suggests that DBC is cycled in the same time scales with the DOC pool in the ocean and no extremely older DBC was identified as reported in other studies previously.
Model adequacy tests for improving predictions in ungauged basins
Authors: Prieto Cristina , Le Vine Nataliya , Kavetski Dmitri , Álvarez César , Medina Raúl
Published: March 2020

Flow prediction in ungauged catchments is a major unresolved challenge in scientific and engineering hydrology. Meeting this challenge is made difficult by the uncertainty in the “regionalization” model used to transpose hydrological data (e.g., flow indices) from gauged to ungauged basins, and by the uncertainty in the hydrological model used to predict streamflow in the ungauged basin. This study combines recent advances in flow index selection, regionalization via machine learning methods, and a Bayesian inference framework. In addition, it proposes two new statistical metrics, “DistanceTest” and “InfoTest”, to assess the adequacy of a model before estimating its parameters. “DistanceTest” quantifies whether a model (hydrological or regionalization) is likely to reproduce the available hydrological information in a catchment. “InfoTest” is based on Bayes Factors and quantifies the information added by a model (hydrological or regionalization) over prior knowledge about the available hydrological information in a catchment). The proposed adequacy tests can be seen as a prerequisite for a model (hydrological or regionalization) being considered capable of providing meaningful and high quality flow time series predictions in ungauged catchments. If a model is found inadequate a priori and rejected, the modeler is spared the effort in estimating the model parameters, which can be a substantial saving.

The proposed regionalization approach is applied to 92 northern Spain catchments, with 16 catchments treated as ungauged. It is found that (1) a small number of PCs capture approximately 87% of variability in the flow indices, and (2) adequacy tests with respect to regionalized information are indicative of (but do not guarantee) the ability of a hydrological model to predict flow time series. The adequacy tests identify the regionalization of flow index PCs as adequate in 12 of 16 catchments but the hydrological model as adequate in only 1 of 16 catchments. In addition, the case study results suggest that the hydrological model is the main source of uncertainty in comparison to the regionalization model, and hence should receive the main priority in subsequent work at the case study catchments.
Using temperature depth profiles to identify the origin of groundwater salinization in Pingtung coastal plain, Southern Taiwan
Authors: Chen Wenfu
Published: March 2020

Temperature depth profiles has been applied on many topics, e.g. climate change, groundwater velocity and saltwater-groundwater interface. In this study, temperature depth profiles are used to identify the origin of groundwater salinization in Pingtung coastal plain, southern Taiwan. Some monitoring wells in the coastal area have reached salty groundwater. Even some of the deeper aquifers, down to 300 m are saltwater. There are two arguments for the origin of those saltwater. One theory is those saltwater were Holocene transgression relics. The other theory is that those saltwater were sea water intrusion due to over-pumping of groundwater. Using the measured temperature depth profiles, a 2D numerical model is developed to simulate the heat transfer of sea water intrusion. The preliminary results show that the cause of salinization is not likely by the modern sea water intrusion. The sea water below a depth of 100 m is a cooler source and the intrusion of sea water should decrease temperature in aquifer. However, the measured temperature data of those salty aquifer are higher.
Relationship of soil moisture with solar-induced chlorophyll fluorescence and normalized difference vegetation index in different phenological stages
Authors: Shen Qiu , Wu Jianjun , Liu Leizhen , Zhao Wenhui
Published: March 2020

As an important part of water cycle in terrestrial ecosystem, soil moisture (SM) provides essential raw materials for vegetation photosynthesis, and its changes can affect the photosynthesis process and further affect vegetation growth and development. Thus, SM is always used to detect vegetation water stress and agricultural drought. Solar-induced chlorophyll fluorescence (SIF) is signal with close ties to photosynthesis and the normalized difference vegetation index (NDVI) can reflect the photosynthetic characteristics and photosynthetic yield of vegetations. However, there are few studies looking at the sensitivity of SIF and NDVI to SM changes over the entire growing season that includes multiple phenological stages. By making use of GLDAS-2 SM products along with GOME-2 SIF products and MODIS NDVI products, we discussed the detailed differences in the relationship of SM with SIF and NDVI in different phenological stages for a case study of Northeast China in 2014. Our results show that SIF integrates information from the fraction of photosynthetically active radiation (fPAR), photosynthetically active radiation (PAR) and SIFyield, and is more effective than NDVI for monitoring the spatial extension and temporal dynamics of SM on a short time scale during the entire growing season. Especially, SIFPAR_norm is the most sensitive to SM changes for eliminating the effects of seasonal variations in PAR. The relationship of SM with SIF and NDVI varies for different vegetation cover types and phenological stages. SIF is more sensitive to SM changes of grasslands in the maturity stage and  rainfed croplands  in the senescence stage than NDVI, and it has significant sensitivities to SM changes of forests in different phenological stages. The sensitivity of SIF and NDVI to SM changes in the senescence stages stems from the fact that vegetation photosynthesis is relatively weaker at this time than that in the maturity stage, and vegetations in the reproductive growth stage still need much water. Relevant results are of great significance to further understand the application of SIF in SM detection.
Development of a global geoid model 2020 (GGM2020)
Authors: Shen WenBin , Xie Youchao , Han Jiancheng , Li Jiancheng
Published: March 2020

We present an updated 5′ ×5′ global geoid model 2020 (GGM2020), which is determined based on the shallow layer method (or simply Shen method). We choose an inner surface S below the EGM2008 global geoid by 15 m, and the layer bounded by the inner surface S and the Earths geographical surface E is referred to as the shallow layer. We formulate the 3D shallow mass layer model using the refined 5′ ×5′ crust density model, CRUST1.0-5min, which is an improved 5′ ×5′ density model of the CRUST1.0 with taking into account the corrections of the areas covered by ice sheets and the land-ocean crossing regions. Based on the shallow mass layer model and the gravity field EGM2008 that is defined in the region outside the Earth’s geographical surface E, we determine the gravity field model EGM2008S that is defined in the whole region outside the inner surface S. Based on the gravity field EGM2008S and the geoid equation W(P) =W0, where W0 is the geopotential constant on the geoid and P is the point on the geoid G, we established a 5′ ×5′ global geoid model GGM2020. Comparisons show that in average the GGM2020 fits the globally available GPS/leveling points better than the EGM2008 global geoid. This study is supported by NSFCs (grant Nos. 41721003, 41631072, 41874023, 41804012, 41429401, 41574007).
The Mineral Exploration of the Haimur Gold-Mine in the South Eastern Desert-Egypt, by Using Geophysical Techniques
Authors: Mekkawi Mahmoud , Ismail Ayman , Al Deep Mohamed , Arafa Sultan , Abdel Hai Mahmoud , Mohamed Abbas
Published: March 2020

The Haimur gold mine is located in the south Eastern Desert, Egypt, about 200 km far from Aswan city and is known as historical mine dated back to (7th–11th centuries). An evidence of ancient mining activities is manifested by excavated quartz veins and old stone tools used for gold extraction. A number of important ancient gold mines in the Allaqi area have, however, received relatively little geological and geophysical attention. Haimur area comprises a variety of Precambrian rocks including igneous and metamorphic units. It is covered by: ophiolite assemblage, metasediments and metavolcanic.

The geophysical measurements are carried out along the ancient mine where the quartz veins are concentered. Several geoelectrical and land magnetic profiles were done perpendicular to the structure of the area, The Electrical Resistivity was acquired by using dipole-dipole configuration of electrode spacing 5, 10 and 15 m of lengths ranging from 160-240 m. In additional to magnetic profiles are applied around old mine. The results indicate that the quartz veins are accomplished with sulfide zones which refer to low resistive zones, high chargeability with moderate to high magnetic anomalies.

Key words: South Eastern Desert, Alter mineralized zone, Land magnetic, Electrical Resistivity and Induced polarization.
Interaction and Reorganization of Loess Gully Network Evolution
Authors: Chen Siming , Xiong Liyang
Published: March 2020

Loess gully is the most active and changeable landform unit in the Loess Plateau of China, whose morphology has been shaped under various formation processes. During the evolution process, gullies in the Loess Plateau interacted with each other and formed an intricate network system, which was the channel for material transportation and energy transmission in this area. From the perspective of the gully evolution process, the development of gully network is dynamic because such a network gradually tends to equilibrium through continuous reorganization. During the evolutionary process, stream capture occurs when a stream or watershed is diverted from its own bed, and flows instead down the bed of a neighboring stream. The stronger and more powerful streams (in terms of channel gradient, stream velocity, discharge and kinetic energy) capture the upstream of weak streams. In the process of dynamic reorganization, the loess gullies formed different shapes and gradually evolved into a stable network structure. In this paper, several gully areas in the Loess Plateau were selected. Based on the geological background, 5 m horizontal-resolution DEM data were used to analyze these areas. The χ index was used to describe the dynamic characteristics of the gully network, which could characterize the evolution trend of the gully. Finally, the author reveals the evolution and reorganization process of the loess gully networks by comparing the χ index diagrams of different areas in different developmental stages. The results show that the area with the stable geological background is closer to the equilibrium state than the area with the complicated geological structure. In other regions, networks composed of gullies in the middle development stage are more stable than networks in the early development stage. More importantly, for two adjacent mature gully networks, the developmental trends at different locations on their watershed boundaries may be different. The results provide for an understanding of gully network evolution and reorganization process in the Loess Plateau, which also contribute to the development of a process-based gully evolution model.

Key words: Loess Plateau ; Gully Network ; Geomorphologic Evolution ; Digital Terrain Analysis
Site effects on Gros Morne Hill, Port-au-Prince, Haïti
Authors: Havenith Hans-Balder , Ulysse Sophia
Published: March 2020

After the M = 7.0 Haiti earthquake in 2010, many teams completed seismic risk studies in Port-au-Prince to better understand why this not extraordinarily strong event had induced one of the most severe earthquake disasters in history (at least in the Western World). Most highlighted the low construction quality as the main cause for the disaster, but some also pointed to possible soil and topographic amplification effects, especially in the lower and central parts of Port-au-Prince (e.g., close to the harbor). Therefore, we completed a detailed site effect study for Gros-Morne hill located in the district of Pétion-Ville, southeast of Port-au-Prince by using near surface geophysical methods. The horizontal to vertical spectral ratio technique was applied to ambient vibrations and earthquake data, and multichannel analysis of surface waves and P-wave refraction tomography calculation were applied to seismic data. Standard spectral ratios were computed for the S-wave windows of the earthquake data recorded by a small temporary seismic network. Electrical resistivity tomography profiles were also performed in order to image the structure of the subsurface and detect the presence of water.

Different site effect components are represented for the entire survey area; we present maps of shear wave velocity variations, of changing fundamental resonance frequencies, and of related estimates of soft soil/rock thickness, of peak spectral amplitudes and of ambient ground motion polarization. Results have also been compiled within a 3D surface-subsurface model of the hill that helps visualize the geological characteristics of the area, which are relevant for site effect analyses. From the 3D geomodel we extracted one 2D geological section along the short-axis of the hill, crossing it near the location of the Hotel Montana on top of the hill, which had been destroyed during the earthquake and has now been rebuilt. This cross-section was used for dynamic numerical modelling of seismic ground motion and for related site amplification calculation. The numerical results are compared with the site amplification characteristics that had been estimated from the ambient vibration measurements and the earthquake recordings. Related results only partly confirm the strong seismic amplification effects highlighted by previous papers for this hill site, which had been explained by the effects of the local topographic and soil characteristics.
Accuracy of GNSS campaign site velocities with respect to ITRF14 solution
Authors: Turen Yener , Sanli Dogan Ugur
Published: March 2020

In this study, we assess the accuracy of deformation rates produced from GNSS campaign measurements sampled in different frequencies. The ideal frequency of the sampling seems to be 1 measurement per month however it is usually found to be cumbersome. Alternatively the sampling was performed 3 measurements per year and time series analyses were carried out. We used the continuous GPS time series of JPL, NASA from a global network of the IGS to decimate the data down to 4 monthly synthetic GNSS campaign time series. Minimum data period was taken to be 4 years following the suggestions from the literature. Furthermore, the effect of antenna set-up errors in campaign measurements on the estimated trend was taken into account. The accuracy of deformation rates were then determined taking the site velocities from ITRF14 solution as the truth. The RMS of monthly velocities agreed pretty well with the white noise error from global studies given previously in the literature. The RMS of four monthly deformation rates for horizontal positioning were obtained to be 0.45 and 0.50 mm/yr for north and east components respectively whereas the accuracy of vertical deformation rates was found to be 1.73 mm/yr. This is slightly greater than the average level of the white noise error from a global solution previously produced, in which antenna set up errors were out of consideration. Antenna set up errors in campaign measurements modified the above error level to 0.75 and 0.70 mm/yr for the horizontal components north and east respectively whereas the accuracy of the vertical component was slightly shifted to 1.79 mm/yr.
Behavior of hydrogen defects in olivine at high temperature and high pressure: disordering, re-configuration and interation
Authors: Yang Yan , Xia Qunke
Published: March 2020

Water in the form of hydrogen defects in olivine strongly influences the physical properties of olivine, thereby being responsible for physical/chemical processes in the deep Earth. Knowledge of hydrogen defects in olivine is fundamental to understand water distribution and its impact on the upper mantle. However, the current explanations of water effects on processes in the deep Earth are mainly based on hydrogen defects observed at ambient conditions. Since hydrogen is highly mobile, the migration of hydrogen between lattice sites at high temperature and high pressure may not be quenchable. Therefore, there arises a question: whether the hydrogen defects in olivine obtained from infrared spectra at ambient conditions are the same as those at the temperature and pressure conditions of the upper mantle? Here, we carry out in situ high-temperature and high-pressure infrared spectroscopic investigations on hydrogen defects in the natural olivine and synthetic Fe-free forsterite. We find that hydrogen defects exhibit disordering at temperature-pressure conditions of the upper mantle, and hydrogen defects corresponding to pure Si vacancies display re-configuration under compression. Interestingly, dehydrogenation experiments of the natural olivine indicate interactions of hydrogen defects. The lost hydrogen of the titanium-clinohumite defects does not completely release out of the crystal. It can migrate to pure Si vacancies and, also, can move to Mg vacancies coupling with trivalent cations. Thus, dehydrogenation and interactions of hydrogen storage sites may be very complex. There may be other reactions among storage sites during dehydrogenation, depending on the chemical compositions, hydrogen storage sites, and the annealing conditions. In conclusion, we report disordering and reconfiguration of hydrogen storage sites at high temperature and high pressure, and also interactions of hydrogen storage sites during dehydrogenation. These are vital for understanding water distribution and processes in the deep Earth.
Few large trees drive the carbon dynamics of temperate forests
Authors: Yuan Zuoqiang
Published: March 2020

Although large trees explain the most variation in biomass and structure of forests, but little is known about whether and how large trees can explain variation of forest dynamics (forest productivity and biomass loss). To shed light on the effects of large trees on forest dynamics we analyzed repeated forest inventory data on 74,300 adult trees spread across 700 quadrats of temperate mixed forest in northeastern China. Here, using piecewise structural equation modeling we examined how top 1% high-biomass, 99% remaining-biomass trees, functional trait diversity (FD) and composition (CWM), climate and soil conditions influence forest dynamics in temperate old growth forests. We found that top 1% high-biomass and top 1% large-diameter trees highly increased forset dynamics and biomass stock rather their relevant 99% remaining trees, FD and CWM supporting big-size trees hypothesis. In addition, climate is more important determinant of forest productivity rates than soil nutrients. Moreover, forest productivity and biomass stock declined with CWM traits. Hence, we highlight top 1% trees overruled the effect of 99% remaining trees, FD and CWM on forest dynamics and biomass stock. We argue that including site variation and the big trees to the integrative ecological modeling help better understanding of ecological mechanisms and drivers of forest dynamics.   
Simulating debris flows triggered by rainfall in Shiyang gully, China
Authors: Li Jiaoyang
Published: March 2020

A debris flow occurred in Shiyang gully, located between Hebei Province and Beijing, on 8 June 2017, resulting in 6 people dead or injured. Short-term heavy rainfall is the main factor that triggered this event, however, the meteorological agency didn’t forecast this event very well. In this study, numerical simulation using FLO-2D was performed to reproduce the debris flow event (flow depths, flow velocities, and sediment depositions)occurred in 2017. The results of the field survey showed that the influential range of debris flow is consistent with the simulation results. Simulated depth accuracy is greater than 70%. Then, we used FLO-2D is calibrated to simulate debris flows disasters under different rainfall scenarios. The results showed that, the Beijing needs to be warned when the accumulated precipitation is 40mm at the rainfall intensity of 1mm/min. As cumulative rainfall and rainfall intensity increase, the risk of Shiyang gully is increasing.  This study used FLO-2D simulated process of debris flows triggered by rainfall. The results showed the early warning time and influential range for different intensity ,accumulated precipitation, and rain area, which is beneficial to the debris flow management in the western mountainous areas of Beijing.
Did the Yangsan Fault in a stable continent region move continuously during the Holocene?
Authors: Choi Sung-Ja , Choi Jinhyuk , Ko Kyoungtae , Jang Yirang , Choi Jeong-Heong
Published: March 2020

The Korean Peninsula is more than 400 km away from passive plate margins and considered a stable continent region. However, it has suffered from damaging earthquakes in the last 20 years. There are two major North–North East tectonic faults in the region: the Chugaryong fault running from Wonsan through Seoul to the west coast and the Yangsan fault in the southeastern part of the peninsula. The Yangsan fault extends for over 170 km and has been active since the late Cretaceous period. The fault has experienced many earthquakes in the last 2000 years, most recently  Mw 5.5 earthquake in its vicinity without any surface rupture. The fault has been studied by various disciplines, such as structural geology to determine the characteristics of the fault, geophysical exploration to determine the extension of the fault, and mineralogy to analyze fault gouges.[A1]  However, the last fault movement remains unknown. Trench studies on the Yangsan Fault undertaken in the central south of the Yangsan Fault to obtain its last movement revealed that the fault had been reactivated at least twice during the Holocene period, at approximately 2 ka and 4 ka. Before the Holocene, another fault movement occurred at approximately 50 ka, with a strike-slip motion creating a meter-wide fault damage zone. LIDAR and aerial photographs demonstrated that a higher terrace younger than 320 ka had moved by 1.5 km with a left-lateral-strike-slip motion. We now surmise that the Yangsan Fault has been continuously reactivated for more than 60 million years, and could potentially generate severe geohazards in the near future. Furthermore, even if the fault is inside an intraplate, we propose that it has continuously been reactivated from the Late Cretaceous to the present by plate tectonics.
Case Study of Blowing Snow Potential Diagnosis with Dynamical Downscaling
Authors: Tanji Seika , Inatsu Masaru
Published: March 2020

Blowing snow potential is diagnosed for typical cases in roads around Sapporo, Japan, as snow concentration and visibility based on dynamically downscaled data with 1-km resolution. The results are consistent with the blowing-snow records on time and place of traffic disruption, when the dynamical downscaling (DDS) reproduced wind speed well for a case. Moreover, the DDS-based diagnosis had a strength on the onset and cease of blowing snow in the event. The diagnosis with mesoscale model analysis with 5-km resolution does not reproduce the blowing snow events in most area, however. Hence, the DDS potentially, not perfectly, adds the value to estimate blowing snow potential, despite a large scale-gap from an explicit representation of small-scale turbulence related to blowing snow. The meteorological forecast with 1-km resolution might improve the estimate of blowing snow potential.
Innovative Approach for Addressing Coastal Erosion Protection Using Microbial Induced Carbonate Precipitation
Authors: Imran Md Al , Nakashima Kazunori , Evelpidou Niki , Kawasaki Satoru
Published: March 2020

Considering the global climate change and the ensuing sea level rise, the subsequent acceleration of coastal erosion is evident. Phenomena of coastal erosion, coastal flooding and shoreline retreat are expected to show a significant increase in frequency and intensity, in global level. The effects of coastal erosion are worsened by storms, and the reduction of sediment supply associated with global warming and anthropogenic modification of rivers and coastlines. As a countermeasure to coastal erosion, this work focuses on the development of coastal artificial in-situ rocks. We developed a new method that encompasses microbes and the related mechanism is called “Microbial Induced Carbonate Precipitation” (MICP). We successfully isolated three microorganisms, Micrococcus sp., Pseudoalteromonas sp., and Virgibacillus sp., from the selected area, and investigated their effectiveness in order to make a solidified sand sample. The precipitated bounding material has also been confirmed as calcite by XRD and XRF analysis. We successfully demonstrated that all of these bacterial species are very sensitive with certain environmental parameters, such as temperature, pH, culture type, culture duration, etc. In laboratory scale, we successfully obtained solidified sand by syringe (d = 2.3 cm, h = 7.1 cm) solidification method bearing UCS (Unconfined Compressive Strength) up to 1.8 MPa using 0.5 M CaCl2 and urea as cementation solution at 30°C. In addition, we propose a new sustainable approach for field implementation of this method through a combination of geotube and MICP mechanism, which will contribute to coastal erosion protection. The proposed approach is more economic, energy-saving, eco-friendly, and sustainable for bio-mediated soil improvement.
Classification and Diagnosis of Summer Monsoon Rainfall Patterns and their Potential Predictability in Southeast China
Authors: Dai Lun , Cheng Tat Fan , Lu Mengqian
Published: March 2020

The East Asian Summer Monsoon (EASM) is a crucial monsoon system that profoundly influences the summer climate in Southeast China (SEC). Classification of monsoon rainfall patterns is vital to physical diagnosis, rainfall prediction and identification of sites that are prone to rainfall-triggering floods. With the great endeavors on understanding the complexity of the EASM in the past decades, the traditionally accepted rainfall patterns in SEC and the relevant analyses appear outdated or even inadequate. Having highly-improved observations at hand helps update the monsoon rainfall patterns in SEC and the potential predictability.

The present study employs a nonlinear neural network classification technique, the Self-organizing map (SOM), to identify the rainfall patterns in SEC based on gauge data. Three distinct rain belts over the Huai River basin (HRB), lower Yangtze River basin (LYRB) and South Coast region (SCR) are found. Their subseasonal variability highly agrees with the stepwise progression of the East Asian Summer Monsoon (EASM) front in space and time. Analysis reveals that precipitation in the SCR and HRB rain belts undergo a regime shift after the mid-1990s, whereas the 1990s is the most active decade for the LYRB rain belt. These systematic changes are in abreast with similar changes in EASM and other climate events documented in the literature.

Additionally, a SOM-based algorithm is developed to further divide gauge stations into three groups featuring homogeneous rain belt patterns. Promising predictability of group-averaged daily rainfall is then achieved, with about 39% to 50% of the total variance explained by circulation-informed regression models, verified by both cross-validation and blind prediction. Through further diagnosis in the useful predictors, the western North Pacific subtropical high, blocking high anomalies over northeast China and the upper-level divergence over SEC, are found to best explain the variability of the rain belts. The proposed Russia-China wave pattern (western/central Russia → north of Tibetan Plateau → SEC) and teleconnection between the El Niño-Southern Oscillation and the rain belts also offer additional predictability. This study aims to set an updated benchmark on the summer monsoon rainfall patterns in SEC, from which the promising daily predictability and the informative circulation patterns are obtained. Findings from this work may also advance the understanding of the EASM rain belts, and offer insights to the source of bias for numerical simulations of daily summer monsoon rainfall in the region.