bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a land deformation model from InSAR: combination with heterogeneous geodetic measurements in the Latrobe Valley (Australia) test site
Authors: Filmer Mick , Johnston Paul , Fuhrmann Thomas , Garthwaite Matt , Woods Alex
Published: March 2020

Deformation of the Earth’s surface affects the maintenance of geodetic infrastructure and its reference frame to support e.g., construction, mineral exploration, telecommunications, and environmental monitoring. As the land deforms, the 3D coordinates of each position will change within the reference frame. Monitoring these changes is particularly challenging for local deformation occurring between GNSS continuously operating reference stations (CORS), as it is not directly measured. Hence, a deformation model to correct for this deformation is required, using radar interferometry (InSAR) to measure localised deformation occurring between the sparse GNSS CORS. The Australian Intergovernmental Committee for Surveying and Mapping’s (ICSM’s) Permanent Committee on Geodesy has recently identified the need for such a deformation model, leading to a project to develop a prototype deformation model combining radar interferometry with other geodetic measurements.

We present the first stage of this project where these data are analysed in the Latrobe Valley study area (south east Australia), where we have used 2.7 years (2015-2018) of Sentinel-1 and ~4 years (19 scenes; 2007-2011) of ALOS PALSAR SAR data to provide estimates of line of sight (LOS) velocity and uncertainties. Time series from five local GNSS CORS have been reprocessed in a consistent reference frame (ITRF2014) giving 3D velocities and uncertainties to which the InSAR time series are referenced. The InSAR rates are converted from LOS to vertical within the ITRF2014 reference frame so that the results are comparable to other geodetic measurements. Repeat levelling measurements from 1980 and 2015 and periodic (non-continuous) GNSS measurements were included for 2015.9 - 2018.5, which provided complementary information to constrain the rates in the study area in both time and space. We test methods to combine these data that relate to different time periods, spatial location, temporal and spatial frequency. We find that all of the data contribute to our understanding of deformation in the Latrobe Valley:  GNSS data shows temporal variations at specific sites, InSAR gives information about the spatial variation in deformation, periodic GNSS provides information at additional spatial locations but at limited points in time, and levelling extends the time series several decades into the past. Subsidence rates approaching 30 mm/yr are found near an open cut mining pit, but the deformation is non-linear in time and space across the study area, adding to the challenge of modelling the deformation where the geodetic observations are sparse. An important outcome of the project is to determine which types of observations best constrain the deformation model and how much new data is required.
Numerical Simulation and Mechanism Analysis of an Extreme Precipitation in Ili Valley, Xinjiang
Authors: Huang Xin , Zhou Yushu
Published: March 2020

The Ili Valley is an area with frequent heavy rain in Xinjiang. In this paper, a heavy rainstorm process in this area on June 26, 2015 is taken as an example. The observational data and WRF high-resolution numerical simulation results are used to analyze the synoptic background and the process of the precipitation. The results show that: (1) The Central Asian low vortex and the upper-level jet provides a favorable circulation background for this heavy rain. Northerly winds and westerly winds forms a low-level convergence line in Ili Valley. (2) In addition to the convergence of low-level airflow, the uplifting effect of the terrain on the westerly winds also intensifies the low-level ascending motion. At the same time, the uplifting effect of the terrain on the northerly winds causes the middle-level ascending motion. After the low-level ascending motion is connected with that of the middle level, precipitation begins to occur. The convection further develops, superimposed with the upwards phase of upper-level wave, and the precipitation increases strongly. (3) Through spectral analysis methods, the characteristics of the upper-level wave are obtained, and the wave is an inertial gravity wave. It is further obtained from the mesoscale three-dimensional Eliassen-Palm (EP) flux that during the period of heavy precipitation, the energy of the upper-level inertial gravity wave is transported down to the low level of the precipitation area. (4) Convective instability plays an important role in the enhancement of the precipitation in the Ili Valley. The analysis of potential divergence further indicates that the convective instability in the precipitation area is mainly caused by the vertical shear part of potential divergence, while the divergence part of the potential divergence can strengthen the convective instability in the leeward slope of the terrain. It indicates that the dynamic and thermodynamic factors are coupled with each other, which affects the precipitation location, intensity and evolution.
A Dynamical Systems Characterisation of Atmospheric Jet Regimes in a Simple Model and Reanalysis Data
Authors: Harnik Nili , Messori Gabriele , Madonna Erica , Lachmy Orly , Farranda Davide
Published: March 2020

Atmospheric jet streams are typically separated into primarily "eddy-driven", or "polar-front" jets and primarily "thermally-driven", or "subtropical" jets. Some regions also display “merged” jets, resulting from the (quasi) co-location of the regions of eddy generation with the subtropical jet. The different location and driving mechanisms of the two jet structures, plus the intermediate “merged” jet, issue from very different underlying mechanisms, and result in very different jet characteristics. Here, we link our understanding of the dynamical jet maintenance mechanisms, mostly issuing from conceptual or idealised models, to the phenomena observed in reanalysis data. We specifically focus on developing a unitary analysis framework, grounded in dynamical systems theory, which may be applied to both the model and reanalysis data and allow for direct intercomparison. Our results provide a proof-of-concept for using dynamical systems indicators to diagnose jet regimes in a versatile, conceptually intuitive and computationally efficient fashion.
Simulating Neanderthal extinction: the role of abrupt climate change, resource competition and interbreeding
Authors: Timmermann Axel
Published: March 2020

It still remains unclear what caused the disappearance of Neanderthals during the last glacial period. To determine whether their demise was mainly due to abrupt climate change, interbreeding or competition, I use a spatially resolved numerical hominin dispersal model that simulates the interaction of Anatomically Modern Humans and Neanderthals in the rapidly varying climatic environment of the last ice age. The numerical simulations, which are in good agreement with archeological and fossil data, document that rapid temperature and vegetation changes associated with Dansgaard-Oeschger events played no discernible role in Neanderthal extinction. Instead, the emerging resource competition in Eurasia between Homo sapiens and Neanderthals, along with low levels of interbreeding were the primary drivers for the demise of Neanderthals. 
Research of Landslide Environment Monitoring Technology for Villages at Fluvial Terraces of the Gaoping River Basin of Taiwan
Authors: Yang Han Chung , Su Chih Chiang , Chen Yen Chang
Published: March 2020

A wireless tracer real-time monitoring system was developed and verified to be suitable for the real-time remote dynamic monitoring of typhoon- and flood-related scour at riverbeds and human-made structures (such as bridge abutments, spur dikes, and embedments). This study focused on the use of a wireless tracer to aid the real-time dynamic monitoring of natural disasters, including slope landslides, thus devising a real-time warning system for sediment disaster prevention and response. We selected Dajin Bridge, which is situated at Taiwan’s Zhoukou River, as the research site for deploying the monitoring system. Monitoring stations for detecting changes in the river’s course were established at both a downstream meander of the Dajin Bridge and a nearby revetment. Specifically, scour monitoring columns were separately buried at these two locations. Each column was equipped with five wireless tracers, and 16 coding sand jars were used to facilitate vertical installation of wireless tracers. Real-time monitoring stations for tracking slope changes were constructed using two methods. In both methods, an upright column was used to install the tracers, and a shielding net cover was additionally used in the second method to expand its monitoring range. After several heavy rain events, no slides or landslides were detected by the landslide stations; an on-site investigation corroborated this observation. As for the detection of the change in the river’s course, three wireless tracers were flushed away. Nonetheless, because the scour depth posed no immediate threat to river bank safety, additional safety measures were not required. The remaining wireless tracers were also adequate for the safety monitoring of river banks, bridges, and other structures within the research area. The aforementioned results demonstrate the effectiveness of the devised remote real-time monitoring system for detecting environmental changes. The system can thus provide real-time remote safety information on changes in slope and a river’s course for residents in mountainous areas.
Timing and magnitude of Southern Ocean sea ice/carbon cycle feedbacks over the last eight glacial cycles
Authors: Stein Karl , Timmermann Axel , Kwon Eun Young , Friedrich Tobias
Published: March 2020

The Southern Ocean (SO) played a prominent role in the exchange of carbon between ocean and atmosphere on glacial timescales through its regulation of deep ocean ventilation. Previous studies indicated that SO sea ice could dynamically link several processes of carbon sequestration, but these studies relied on models with simplified ocean and sea ice dynamics or snapshot simulations with general circulation models. Here we use a transient run of the LOVECLIM intermediate complexity climate model, covering the past eight glacial cycles, to investigate the orbital-scale dynamics of deep ocean ventilation changes due to SO sea ice. Cold climates increase sea ice cover, sea-ice export, and Antarctic Bottom Water formation, which are accompanied by increased SO upwelling, stronger poleward export of Circumpolar Deep Water, and a reduction of the atmospheric exposure time of surface waters by a factor of ten. Moreover, increased brine formation around Antarctica enhances deep ocean stratification, which could act to decrease vertical mixing by a factor of four compared to the current climate. The impact of the two mechanisms on carbon sequestration was then tested within a steady-state carbon cycle. The two mechanisms combined can reduce atmospheric carbon by 40 ppm, of which approximately 30 ppm is due to ocean stratification. Moreover, ocean stratification from increased SO sea ice production acts early within glacial cycles to amplify the carbon cycle response.
Large scale particle image velocimetry measurement of river surface velocity based on images captured by a camera of the mobile phone
Authors: Liu Wen-Cheng , Huang Wei-Che
Published: March 2020

In this research, we conducted LSPIV (Large Scale Particle Image Velocimetry) measurements to measure river surface velocity based on images recorded by mobile phone. The realization of this research is based on the developments of two products. The first one is the digital camera, which has been combined with the mobile phone after several years of development. The second one is the three-axis accelerometer, which can measure the attitude of the object. A three-axis accelerometer is one of the necessary parts of the mobile phone nowadays, as many functions of the mobile phone, such as step counting, Do Not Disturb mode, games, require the detection of attitude.

In LSPIV, there are nine parameters of the collinear equation. Three of parameters are the coordinates of the perspective center in the image space (focus distance d and image center position (u, v)), which can be determined in advance in the laboratory; the other three parameters are the coordinates (x, y, z) of the perspective center in real space, which can be set to (0, 0, 0); the last three parameters are the attitude of the camera (i.e., the mobile phone), which is determined by the depression angle, the horizontal angle, and the left-right rotation angle and can be measured by three-axis accelerometer. Therefore, river surface velocity could be analyzed by LSPIV with not only continuous images captured by a camera of the mobile phone but also the acceleration values obtained by the three-axis accelerometer when each image was captured.

In the present study, Yufeng gauging station, which is in the upstream catchment of the Shihmen Reservoir in Taiwan, is selected as the study site. Two other measurement methods were used to measure the river surface velocity and the comparison was conducted. One is using a handheld digital flow meter and another is using LSPIV with control points to calculate the parameters for measuring the river surface velocity.
Correlations among seabed mega pockmark size, water depth, and gas volumes suggest formation by depressurization: A case study of the Reed Basin in the South China Sea
Authors: Wu Ziyin , Zhao Dineng , Zhou Jieqiong , Luo Xiaowen , Shang Jihong
Published: March 2020

Pockmarks are relict seafloor geomorphological features formed by seepage of gas or fluid from the seabed. While seafloor pockmarks are widely distributed around the world, mega pockmarks with diameters > 1 km are rare, and their formation and maintenance mechanisms remain enigmatic. Using high-resolution multi-beam bathymetric data, this paper systematically identified mega pockmark groups in the southern depression of the Reed Basin in the South China Sea. Mega pockmarks of various shapes occur in groups in the Reed Basin, primarily along the sides of submarine canyons. Observed geomorphologic characteristics differ significantly from features reported in the published literature. Based on the collected data, the average ratio of pockmark depth to pockmark radius (d/r) is evaluated as ~0.3, which is consistent with analyses of additional pockmarks in 21 regions around the world. Our observations also agree with the previously reported generalization that small pockmarks are developed in shallow water and large pockmarks in deep water. We propose that pockmarks in the Reed Basin are formed by seafloor gas explosions. Widely developed carbonates store buried gas that continuously seeps along NE-SW trending faults. Cap layers are undercut by submarine canyons forming lines of mechanical weakness. During periods of rapid sea level fall, depressurization causes buried gas to be rapidly ejected along these lines, forming large pockmark groups. Because these results correlate easily observed bathymetric features to the presence of buried gas deposits, they have important implications for the exploration and research of deep-sea gas resources.
Satellite UV-Vis spectroscopy: implications for air quality trends and their driving forces in China during 2005–2017
Authors: Zhang Chengxin , Liu Cheng , Hu Qihou , Cai Zhaonan , Su Wenjing , Xia Congzi , Zhu Yizhi , Wang Siwen , Liu Jianguo
Published: March 2020

Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species. Here, we implemented several spectral fitting methods to retrieve tropospheric NO2, SO2, and HCHO from the ozone monitoring instrument (OMI), with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere. We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005–2017, especially in heavily polluted regions. We found significant decreasing trends in NO2 and SO2 since 2011 over most regions, despite varying temporal features and turning points. In contrast, an overall increasing trend was identified for tropospheric HCHO over these regions in recent years. Furthermore, generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls. Our results indicated that although meteorological parameters, such as wind, water vapor, solar radiation and temperature, mainly dominated the day-to-day and seasonal fluctuations in air pollutants, anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO2, SO2, and HCHO in the past 13 years. Generally, recent declines in NO2 and SO2 could be attributed to emission reductions due to effective air quality policies, and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound (VOC) emissions.
Study on the hydrocarbon accumulation models of the upper Es3 in the gentle slope belt of Chexi Depression
Authors: Zhao Shan , Liu Hua
Published: March 2020

Based on the analysis of hydrocarbon source, reservoir forming period, composition and classification of transportation system, and the reasons of failure well in Chexi Depression of Bohai Bay Basin，Two types of hydrocarbon accumulation models in gentle slope belt of Chexi area are established and the main controlling factors of hydrocarbon accumulation are defined. There are three sets of source rocks（Es1、middle and lover submember of Es3、Es4）in Chexi area, the different strata of source rocks have great differences in the Pr/Ph and the content of gammacerane. It has been found that the crude oil of Es3 has a good geochemical correspondence with the middle and lower of Es3 source rocks, and has the characteristics of near source accumulation. The hydrocarbon accumulation in the study area exists in the sedimentary period of the Dongying formation and the sedimentary period of the Guantao formation to the present two stages, which is dominated by late filling. There are two stages of oil and gas filling in the inner and middle belts, and only late stage hydrocarbon filling in the outer slope belt. The hydrocarbon transportation system is mainly composed of faults and sand bodies. The effective source rocks in the middle and lover submember of Es3 are connected with the upper reservoir of Es3 in a small area, which can be directly migrated to the upper sandstone reservoir of Es3 to form lithologic oil and gas reservoir. However, most of the oil and gas in the upper Es3 reservoir need to be vertically migrated by means of oil source fault, and then through the contact of sand bodies such as main channel and fan body, the main oil and gas reservoir will gradually move up with the distance from the source rock. The area with direct contact source reservoir configuration relationship is a "sand body lateral migration" reservoir formation mode, and the main controlling factors of reservoir formation are sand body connectivity and reservoir porosity and permeability. The source reservoir configuration area with fault connection type is a "fault sand combination T-type migration" reservoir forming mode, and the main controlling factors of reservoir forming are migration convergence facies (structural ridge and cross-section ridge).The area of passive reservoir contact is "fault sand combination step migration" reservoir forming mode, and the main controlling factors of reservoir forming are migration convergence facies (structural ridge) and lateral sealing of faults in preservation conditions.

Key words: Chexi Depression; Source of hydrocarbon; Accumulation period; Fault sand transport combination; Reservoir forming mode
An EU-wide citizen science network to monitor hydrological conditions in intermittent rivers and ephemeral streams
Authors: Sauquet Eric , van Meerveld Ilja , Sefton Cath , Fortesa Josep , Ramos Ribeiro Helena , Tziortzis Iakovos , de Girolamo Anna Maria , England July , Estrany Joan , Fortuño Pau , Munné Antoni , Csabai Zoltan , Morais Manuela , Alves Helena , Datry Thibault
Published: March 2020

Studying Intermittent Rivers and Ephemeral Streams (IRES) requires regular observations of streamflow. Unfortunately, intermittent streams are poorly monitored, particularly in temperate climates. To fill gaps in knowledge of the dynamics of intermittent streams, a pilot initiative within the SMIRES project (Datry et al., 2017, https://www.smires.eu/) was launched in April 2019. This initiative invited citizens to submit observations for a large number of European intermittent streams.

The goal was collecting datasets that can be used in robust scientific inquiries:

-             To identify IRES at the European scale. Everyone was encouraged to report the flow state for any stream in Europe at any time during 2019;

-             To investigate the dynamics of flow intermittence by repeating field observations along an IRES at least once each month and if possible at multiple locations.

The CrowdWater app (https://crowdwater.ch/en/crowdwaterapp-en/) was used to collect the observations. Each contributor was asked to take a picture of the stream and to identify the current flow state of the stream as one of six classes, from “dry” to “flowing”. The citizen science network has collected, in eight months, more than 3500 observations in ~500 river reaches across 15 countries.

In this presentation, we will discuss the benefits and the limitations of this citizen science effort (i.e., how these data complement the information provided by gauging stations, how and why the collected data were used by the main contributors, how participants can be engaged in the long-term etc.). We will compare the success of this international initiative to other regional or local scale initiatives.

References:

Datry, T., Singer, G., Sauquet, E., Jorda-Capdevilla, D., Von Schiller, D., Subbington, R., Magand, C., Pařil, P., Miliša, M., Acuña, V., Alves, M., Augeard, B., Brunke, M., Cid, N., Csabai, Z., England, J., Froebrich, J., Koundouri, P., Lamouroux, N., Martí, E., Morais, M., Munné, A., Mutz, M., Pesic, V., Previšić, A., Reynaud, A., Robinson, C., Sadler, J., Skoulikidis, N., Terrier, B., Tockner, K., Vesely, D., Zoppini, A (2017) Science and Management of Intermittent Rivers and Ephemeral Streams (SMIRES). Research Ideas and Outcomes 3: e21774. https://doi.org/10.3897/rio.3.e21774
Early-Paleozoic geodynamics of the Altai orogen: Constraints from geochemical and zircon U-Pb-Hf isotopic study of paragneissic rocks from the southern Chinese Altai
Authors: Cui Xing , Sun Min , Zhao Guochun , Zhang Yunying , Yao Jinlong , Han Yigui
Published: March 2020

The high-grade metamorphic complexes in the Chinese Altai were previously regarded as the Precambrian basement and thus important for unravelling tectonic evolution of the Altai orogen. This study reports detailed filed investigation, zircon U-Pb-Hf isotopic and whole-rock geochemical data for the paragneissic rocks from Northern Fuyun Complex (NFC), southern Chinese Altai. Detrital zircons from the paragneisses have a predominant early Paleozoic age population (ca. 535-435 Ma), with minor Neoproterozoic and sparse Mesoproterozoic to Archean ages. The geochemical analyses together with the euhedral shape of the detrital zircons suggest that their sedimentary protoliths mainly came from felsic-intermediate igneous rocks with low maturity. In combination with the cumulative distribution curves of zircon age spectra, the variable zircon εHf(t) values (-25 to +13), as well as the immature geochemical compositions, we infer that the protoliths were most likely deposited on an active continental margin in the early Paleozoic and sourced mainly from proximal igneous rocks, which are comparable to the Habahe Group. Similar detrital zircon age spectra of early Paleozoic sequences from the Chinese Altai, Mongolia Altai and Khovd Zone support the existence of a giant accretionary wedge developed along the western margin of the Ikh-Mongol Arc system, resulting from continuous northeast-dipping oceanic subduction. This research was financially supported by the National Key R&D Program of China (2017YFC0601205), Hong Kong RGC GRF (17302317 and 17303415) and NSFC Projects (41730213 and 41190075).
Dust detection by antenna instruments
Authors: Sternovsky Zoltan , Shen Ming-Hsueh , DeLuca Michael , Fredriksen Åshild , Horányi Mihály , Hsu Sean , Kočiščák Samuel , Malaspina David , Nouzák Libor , Ye Shengyi
Published: March 2020

Antenna instruments on space missions have been used to detect dust particles and characterize dust populations. The antennas register the transient electric signal generated by the expansion of the impact plasma from the dust impact on the spacecraft body or the antenna. Given the large effective sensitive area, antenna instruments offer an advantage over dedicated dust detectors for dust populations with low fluxes. The dust accelerator facility operated at the University of Colorado has been employed to investigate the physical mechanisms of antenna signal generation. The dominant mechanism is related to the charging of the spacecraft (or antenna) by collecting some fraction of electrons and ions from the impact plasma. We have carried out a number of experimental campaigns in order to characterize the dust impact charge yields from relevant materials, the effective temperatures of dust impact plasmas, and variations of the antenna signals with spacecraft potential, or magnetic field. Here we report on a physical model that provides a good qualitative and quantitative description of the antenna waveforms recorded in laboratory conditions. The model is based on the separation of the electrons from the ions in the impact plasma and their different timescales of expansion. The escaping and collected fractions of charges are driven by the spacecraft potential. Fitting the model to the laboratory data revealed that the electrons in the impact plasma have an isotropic distribution, while ions are dominantly moving away from the dust impact location. Identifying the fine details in the antenna signals requires a relatively high sampling rate and thus not commonly resolved for past instruments. The high-rate mode of the FIELDS instrument on the Parker Solar Probe, however, can be used to verify the proposed model.
Evaluating nitrogen isotopes as proxies for depositional redox conditions in shales: A case study from the Chang 7 Shale in the Ordos basin, North China.
Authors: Chen Ruiqian , Liu Guangdi
Published: March 2020

Bulk sedimentary nitrogen isotopes (δ15N) have been used as an accurate redox proxy in well-preserved sedimentary systems, however, fewer studies of N-isotope have been performed in lacustrine shales.  In this paper, we report the first δ15N data from the Chang 7 Shale from a core drilled in the Ordos Basin. Bulk δ15N values are significantly higher in Zone A (the Chang 73 and the lower part of the Chang 72 submembers, average = 9.4 ± 1.3‰) than in Zone B (the upper part of the Chang 72 and the Chang 71 submembers, average = 5.4 ± 1.5‰). Given the lithological characteristics and previous geochemical measurements, we suggest that sediments within Zone A of the Chang 7 Shale were mainly deposited under suboxic bottom water conditions, whereas Zone B sediments show evidence of deposition under oxic deep water regimes. Additionally, organic carbon isotopes (δ13Corg) and total nitrogen (TN) values were measured to characterize any processes that might control alteration of the bulk δ15N signal, including changes in organic matter source and post-depositional processes. Our results show that there is no significant difference in the organic carbon isotopes (δ13Corg) and total nitrogen (TN) values between the two zones. In conclusion, we suggest that the difference in δ15N values through the Chang 7 Shale primarily reflects differences in the depositional redox conditions and δ15N values of shale can provide important details regarding the depositional history of unconventional resource plays.
Estimations of net radiation flux distributions from automatic weather stations and satellite data in the Upper Blue Nile (UBN) basin, Ethiopia
Authors: Tegegne Eyale Bayable , Ma Yaoming , Chen Xuelong , Ma Weiqiang , Wang Binbin , Ding Zhangwei , Zhu Zhikun
Published: March 2020

Net radiation is the main energy balance component of land surfaces. It is an important factor in the studies of land-atmosphere processes, water resources management and so on. This is particularly true in the UBN basin where significant parts of the basin are dry and evapotranspiration (ET) is a major path of water loss. In this paper, we have estimated instantaneous net radiation distributions in the basin from MODIS Terra satellite and Automatic Weather Station (AWS) data. As downward shortwave radiation and air temperature usually vary spatially due to topographic effects, which are common features of our study area, we had applied residual kriging spatial interpolation approaches in the conversion processes of point weather data to surface data. Validation attempts of the simulated net radiation outputs with an independent field measurement at Choke flux tower site, which is in the central part of the basin, has shown that our method were able to reproduce downward shortwave, upward shortwave., and net radiation flux with a statistical metrics of Mean bias (MB) and Root Mean Square (RMSE) lesser than other studies done in similar physiographic regions in several parts of the world. It looked that the use of AWS data and residual kriging spatial interpolation technique made our results robust and even comparable to works done using finer spatial resolution satellite data than MODIS. The estimated net shortwave, net longwave and overall net radiations were in close agreement with ground truth measurements with MB of -14.84, 5.7 & 20.53 Wm-2 and RMSE 83.43, 32.54 & 78.07 Wm-2 respectively. The method has potential applications in research works like energy balance, ET estimation, and weather predictions in regions with similar physiographic features as that of the Nile basin.
Application of Probabilistic Neural Network and Rock physics Analysis for Carbonate Reservoir Characterization: A Case Study from Onshore Supergiant Oil Field
Authors: Alali Ali , Stephen Karl
Published: March 2020

Identification and modeling of the carbonate tidal channels is key for finding sweet spots or areas at higher risk to water breakthroughs which have a significant impact on the development and monitoring of reservoir dynamic performance. However, such these channels cannot be easily characterize by conventional seismic attributes. It is important to decipher the complexity of carbonate tidal channel architecture with integrated multisource data and different approaches.

A step wise approach has been taken in this work. First, rock physics model was carried out to ensure that elastic properties can be applied for reservoir characterization from the seismic data. Then, post-stack seismic inversion was carried out on the high resolution of 3D seismic dataset. The seismically derived porosity estimation is undertaken using geostatistical method and multiattributes combination was used. Probabilistic neural network training technique was then performed to improve the results for thick reservoir and the result has been used for seismic conditioning of geological models. Finally, the spatial distribution of porosity volume was cautiously assessed through the comparison between input and blind wells, also validated by core data.

The analysis of rock physics displayed a high correlation between elastic properties and the porosity distribution of the Mishrif channel, three facies were observed. The final interpretation of seismically derived characterization in Mishrif channel, observed a different lateral distribution of inverted elastic properties. These features of Mishrif carbonate tidal channels could be classified into these regions: north, southwest, and east. Related a high porosity with low acoustic impedance appeared mostly in these channels which reflect a good reservoir quality grainstone channels or sholas bodies. While, outside these channels is heavily mud filled by peritidal carbonates and characterized a high acoustic impedance anomaly with low quality of porosity distribution.

The results provided a new insight into the distribution of the petrophysical properties and reservoir architecture of facies with quantification of their influence on dynamic reservoir behavior in the Mishrif channelized systems and also for similar heterogeneous carbonate reservoirs
Effects of large macropores on soil evaporation in salt marshes
Authors: Zhou Tingzhang , Xin Pei , Jirka Šimůnek Jirka
Published: March 2020

The occurrence of macropores in salt marsh sediments is a natural and ubiquitous phenomenon. Although they are widely assumed to significantly affect water flow in salt marshes, the effects are not well understood. We conducted physical laboratory experiments and numerical simulations to examine the impact of macropores on soil evaporation. Soil columns packed with either sand or clay and with or without macropores were set up with water tables in the columns set at different levels. A high potential evaporation rate was induced by infrared light and a fan. The results showed that in the soil with a low saturated hydraulic conductivity (and thus a low transport capacity), macropores behaved as preferential flow paths, delivering water from the groundwater towards the soil surface and maintaining a high evaporation rate in comparison with the soil without macropores. This effect was more pronounced for sediments with lower hydraulic conductivities and shallower groundwater tables. These results not only improve our understanding of water flow and soil conditions in salt marshes but also shed light on soil evaporation in other hydrological systems.
Sub-seasonal precipitation forecast skills over China during the boreal summer monsoon
Authors: Li Yuan , Wu Zhiyong , He Hai , Wang Qj , Wasko Conrad , Li Tianyi , Lu Guihua
Published: March 2020

Sub-seasonal precipitation forecasts during the boreal summer monsoon season are very valuable for flood and drought mitigation over China. Here, we evaluate the sub-seasonal precipitation forecast skills of 11 dynamic models from the Sub-seasonal to Seasonal (S2S) Prediction Project at various spatial and temporal scales. For ensemble mean forecasts, most models show significant correlations with observations at both grid and basin scales with lead time up to 2 weeks. When the lead time is beyond week-2, significant correlations are only observed over southeast and western China at the grid scale. Spatial aggregation helps improve week-3-4 average forecast skills at basin scales; significant correlations can be found for all hydroclimatic regions over China. For ensemble forecasts, most S2S models produce skilful forecasts at basin scale as measured by discrimination scores. Both the El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO) have an impact on precipitation forecast skills at week-3-4. In particular, forecast skill improvement is most pronounced when the forecasts are initialized during active MJO center located in Maritime Continent (Phase 4~5). The results here will help inform the usefulness of sub-seasonal forecasts for hydrological modelling for drought and flood mitigation.
High resolution GPR investigations employing single and multichannel systems in the Necropolis of Monte Abatone, Cerveteri (Roma, Italy).
Authors: Piro Salvatore , Malandruccolo Bruna
Published: March 2020

The Monte Abatone Necorpolis is one of the main important necropolis of Cerveteri, located 60 km north of Rome (Latium, Italy). In this area, several tombs have been discovered and excavated from the 1800, though still many remain hidden underneath the subsurface.

In the last two years, geophysical surveys have been carried out to investigate the unexplored portions of the ancient Etruscan Necropolis, to provide a complete mapping of the position of the tombs. Ground Penetrating Radar and the Magnetometric methods have been used during 2018 to investigate few parts of the Necropolis. During 2019 (July and September) GPR system SIR 3000 (GSSI), equipped with a 400 MHz antenna with constant offset, SIR4000 (GSSI) equipped with a dual frequency antenna with 300/800 MHz and the 3D Radar Geoscope multichannel stepped frequency system were employed to survey 5 hectares where the presence of tombs was hypothesized from previous archaeological studies.

All the GPR profiles were processed with GPR-SLICE v7.0 Ground Penetrating Radar Imaging Software (Goodman 2017). The basic radargram signal processing steps included: post processing pulse regaining; DC drift removal; data resampling; band pass filtering; background filter and migration. With the aim of obtaining a planimetric vision of all possible anomalous bodies, the time-slice representation technique was applied using all processed profiles showing anomalous sources up to a depth of about 2.5 m.

The preliminary obtained results clearly show the presence of a network of strong circular features, linked with the buried structural elements of the searched tombs.

Together with archaeologists, these anomalies, have been interpreted to have a better understanding of the archaeological definition of these features and to enhance the knowledge of the necropolis layout and mapping; after the geophysical surveys, excavations have been conducted, which brought to light few of the investigated structures.

 

References

Campana S., Piro S., 2009. Seeing the Unseen. Geophysics and Landscape Archaeology. Campana & Piro Editors. CRC Press, Taylor & Francis Group. Oxon UK, ISBN 978-0-415-44721-8.

Goodman, D., Piro, S., 2013. GPR Remote sensing in Archaeology, Springer: Berlin.

Piro S., Papale E., Zamuner D., Kuculdemirci M., 2018. Multimethodological approach to investigate urban and suburban archaeological sites. In “Innovation in Near Surface Geophysics. Instrumentation, application and data processing methods.”, Persico R., Piro S., Linford N., Ed.s. pp. 461 – 504, ISBN: 978-0-12-812429-1, pp.1-505, Elsevier.
Drivers of multi environmental impacts embodied in international rice trade
Authors: Caro Dario , Sporchia Fabio
Published: March 2020

Global rice production and trade have strongly increased in recent years. Trade of rice corresponds to a high share of virtual resources shipped from a country to another one. While most of the studies have focused on single impacts embodied in international trade of agricultural products, this study reveals a complete overview of the three most relevant resources/impacts embodied in international rice trade such as water, land and CH4 emissions. Our analysis includes more than 160 countries for the period 2000-2016 by using country-specific impact factors. This trilateral analysis allows the assessment of tradeoffs between different impact categories and relative discussion about international trade policies. Indeed, while the outcome of the impacts embodied in trade is mostly due to the volume of rice traded, the three country-specific impact factors such as water demand, yield and emission factor also determinate the results thus revealing tradeoffs among the three impacts generated. Existing trade flows are mainly leaded by economic aspects rather than focusing on environmental performances. We conclude that international policies should lead developing countries, which are the largest exporters of rice and have a lower efficiency production, to invest in the improvement of their environmental performances thus maintaining their international market competitiveness.  
The effect of multi-GNSS and ionospheric delay on real-time velocity estimation with the variometric approach
Authors: Geng Tao , Ding Zhihui
Published: March 2020

The variometric approach, based on time difference technique in which single-receiver code and carrier phase observations are processed along with available broadcast orbits and clocks, presents a high accuracy on estimating receiver velocity (at mm/s level) in real time. In order to analyze the effect of ionospheric delay on velocity estimation, we evaluate the velocity estimation accuracy of six selected stations with different latitude at approximately 120-degree longitudes during a solar cycle from 2009 to 2019. Compared with the low-solar activity year, velocity estimation RMS during the high-solar activity year will increase by 2-4 mm/s in the east, north and up direction. Velocity estimation RMS time series agree well with the sunspot number time series. The correlation coefficients of six stations between RMS values and sunspot number are 0.45-0.66, 0.39-0.52, 0.39-0.63 in the east, north and up direction respectively. The accuracy of velocity estimation is positively correlated with the sunspot number. We also reconstructed seismic velocity waveforms caused by the 2017 Mw 6.5 Jiuzhaigou earthquake using variometric approach. The results show that multi-GNSS fusion can improve the velocity accuracy by 1-2 mm/s in the horizontal component and 3-4 mm/s in vertical component, with an improvement of 47%, 54%, 41% in the east, north, up direction compared with GPS-only results.
Geochemical and isotopic data of Zheduo-Gongga granitic intrusive complex, eastern margin of the Tibetan Plateau: no evidence for middle-lower crustal flow
Authors: Hu Fangyang , Wu Fuyuan , Ducea Mihai , Chapman James
Published: March 2020

Geophysical studies have shown that middle-lower crustal flow started from central Tibetan Plateau may exist in the eastern margin of the Tibetan Plateau, which controls the mountain building, crustal thickening and deformation (Schoenbohm et al., 2006; Bai et al., 2010; Bao et al., 2015; Zhu et al., 2017). However, no geological and petrological evidence have been presented. We carried out detailed studies on the geochemical and isotopic compositions of the Mesozoic-Cenozoic Zheduo-Gongga granitic intrusive complex on the eastern margin of the Tibet Plateau. Geochronology studies show that these granitoid rocks are formed during Mesozoic to Cenozoic, including ~220-200 Ma Gongga granodiorite to biotite granite with mafic enclaves, ~40 Ma Zheduo gneissic granite, ~28 Ma Zheduo monzogranite, and ~20-4 Ma Zheduo biotite granite and monzogranite. Two groups of geochemical features are obtained: Group 1 (gnessic granite, granodiorite, monzogranite, and leucogranite) has relatively low K2O, Th/La, La/Yb and Rb/Sr ratios, but high Sr/Y ratio with no Eu negative anomalies; Group 2 (biotite granite) has relatively high K2O, Th/La, La/Yb and Rb/Sr ratios, but low Sr/Y with strong negative Eu anomalies. The Sr-Nd-Hf-O isotopic studies on plagioclase, apatite and zircon show that their sources are primarily the basement of the western margin of Yangtze Craton and Songpan-Ganzi sediments. These features indicate that they have different petrogenesis processes. Group 1 is mainly derived from partial melting of mafic rocks in the lower crust, whereas the Group 2 is primarily derived from partial melting of metasedimentary rocks experiencing fractionation of plagioclase. Magma derived from different sources mixing with each other are observed as well. Therefore, from geochemical aspects, no exotic materials are involved in the formation of granitoid rocks during Mesozoic to present. The flow of crustal material in the middle-lower crust may be not existed. The low velocity and high conductivity layer in the middle-lower crust may represent a regional partial melting zone, which could be related to the upwelling of asthenosphere. Both crustal deformation and upwelling of asthenosphere may contribute to the crustal thicknening and uplift.
Polar vortex shape-transition during SSW depending on preceding NAO conditions
Authors: Choi Hyesun , Choi Wookap , Kim Seong-Joong , Kim Baek-Min
Published: March 2020

Sudden stratospheric warming (SSW) characterized by a rapid increase in polar stratospheric temperature and an abrupt decrease in circumpolar westerly wind is accompanied by deformation in the shape of the polar vortex. The SSW type can be distinguished depending on the vortex shape. SSW events preceded by a displacement in polar vortex center are characterized by whether they retain their displaced form (displacement-displacement type) or split into two vortices (displacement-split type) after onset. Here, we show that existence of a polar vortex shape-transition during the course of the SSW life cycle can be attributable to the condition of North Atlantic Oscillation (NAO) preceding before onset: Positive NAO favors SSW of displacement-displacement type with no transition while negative NAO favors the displacement-split type. We show that, in positive NAO precondition, vertical flux of wave activity immediately before onset is mostly contributed only by wavenumber 1 component, which contrasts with the relatively stronger contribution of wavenumber 2 in negative NAO pre-condition. This study provides probability that the North Atlantic anomaly can induce a favorable condition for the development of small scale waves and lead to the occurrence of SSW type-transition. Whole Atmosphere Community Climate Model (WACCM) simulation results reproduce well the observational findings. Therefore, NAO can be regarded as a useful predictor for distinguishing the type of forthcoming SSW events.

 
Carbon emissions from wildfires in larch forest ecosystems of Northeast Siberia
Authors: Delcourt Clement J. , Izbicki Brian , Kukavskaya Elena A. , Mack Michelle C. , Maximov Trofim C. , Petrov Roman E. , Rogers Brendan M. , Scholten Rebecca , Shestakova Tatiana , van der Werf Guido , van Wees Dave , Veraverbeke Sander
Published: March 2020

The boreal forest is one of the largest terrestrial carbon reservoirs on Earth and accounts for approximately 30% of the world’s forest cover. The boreal carbon balance is thus of global significance. Wildfires affect the boreal carbon balance, releasing large amounts of carbon into the atmosphere when soil organic layers and aboveground biomass are combusted. The boreal forest is warming faster than the global average. These higher temperatures lead to increases in the frequency and severity of wildfire disturbance in boreal regions.

Significant progress has been made in quantifying carbon combustion in North American boreal forests, yet few measurements have been conducted in the larch dominated boreal forests of Northeast Siberia. Deciduous needleleaf larch forest growing on continuous permafrost is a unique ecosystem of Siberia. Although these larch forests cover approximately 20% of the boreal biome, the consequences of intensifying fire regimes on the carbon stocks and vegetation dynamics of these ecosystems remain poorly understood.

We conducted a field campaign in larch forests around Yakutsk, Northeast Siberia, during the summer of 2019 with the goal of filling parts of these knowledge and data gaps by collecting ground measurements of carbon combustion from two large fire events in 2017 and 2018. During this campaign, we sampled 42 burned sites in two fire scars that cover gradients of fire severity, vegetation composition and landscape position. Within these sites, we performed a wide range of measurements to quantify aboveground and belowground carbon emissions, constrained by data from 12 unburned sites. We also assessed post-fire recovery and active layer deepening. We investigated major drivers of pre-fire carbon stocks and subsequent combustion at the site level. Our results will reduce uncertainties in larger scale estimates of carbon emissions from Siberian fires which is in turn essential for assessing the implications of the climate-induced intensification of fire regimes for the global carbon cycle.