bluuebunny/crossref_metadata_2025 huggingface dataset:
Carrying capacity of winter geese in the largest freshwater floodplain in different hydrological scenarios
Authors: Xia Shaoxia , Meng Zhujian , Teng Jiakun , Yu Xiubo
Published: March 2020

The maintenance of wetland functions closely relates to the hydrological regime in floodplains. Poyang Lake, a large freshwater floodplain, is one of the most important wintering grounds for geese along East Asian-Australasian Flyway. Wintering geese prefer Carex spp as their main food source whose consequent growth is greatly affected by flooding duration and exposure time of the meadow. Therefore, hydrological condition affects the carrying capacity of the geese through wet meadow growth process.

Combining with remote sensing data and Digital Elevation Models, as well as field study, we identified the exposure time of meadow and the effective growth time of Carex spp. Applying geese’s feeding characteristics with logistic equation, we deduced the time window fit for geese's feeding on vegetation from growth curve. The distribution pattern of Carex spp suitable for geese feeding is also mapped according to the flood recession dates and digital elevation model. In addition, we modelled the above ground biomass using the vegetation index and in-situ experiments data in the wintering period of the wet year (2016), the normal year (2015) and the dry year (2006). Therefrom, we estimated the carrying capacity in wintering period referring the daily energy demand of geese in three different hydrological scenarios.

The results show that the exposure time of the dry year is brought forward 41 days and 56 days compared to the normal year and the wet year respectively. Among them, the average biomass of wet year is the highest, which is about 5.7×104t, while it decreased by 12% and 4.4% of those in dry year and the normal year. The carrying capacity of the geese in Poyang Lake in the three hydrological scenarios are all in surplus compared with the actual amount of geese according to the waterbirds survey of the same year. The maximum carrying capacity in the dry year is in September, while in November for the normal and wet year. In general, the growth process of Carex spp in the normal year and the wet year match the requirements of wintering geese in their peak period better than the wet year. However, the growth process in dry year may even have negative effects on the feeding of geese. This study is very important for appropriate hydrological regulation and wetland management in Poyang Lake, and for predicting habitat carrying capacity and formulating conservation strategies with scientific data.
How Reliable are CME speeds derived from single viewpoint observations?
Authors: Paouris Evangelos , Vourlidas Angelos , Papaioannou Athanasios , Anastasiadis Anastasios
Published: March 2020

Images of Coronal Mass Ejections (CMEs) are primarily acquired by space-based coronagraphs. Such images capture the outward flow of density structures from the Sun by observing Thompson-scattered sunlight from the free electrons entrained in these structures. Because the emission is optically thin, CMEs images are projections of their real 3D structure on the field of view (FOV) of the coronagraph. As a result, the CME characteristics (e.g. linear speed, angular width) calculated from these images, suffer from projection effects and their reliability needs to be quantified. In this work we apply a geometrical method for the de-projection of the linear CME speeds of 4009 CMEs from the CDAW catalog, associated with solar flares (3225 C-class, 736 M-class and 48 X-class solar flares). Our aim is to provide a robust quantification of the reliability of the CME properties from L1 (SOHO/LASCO) single viewpoint measurements.

In addition, we compare the intensity and location of solar flares with the CME kinematic characteristics. In particular, 482 M-class solar flares associated with CMEs with an angular width 30°< w < 120°, show a dependence of the mean CME linear speed with the longitude of the parent solar flare, indicating that projection effects of CMEs should be reduced near the solar limb. However, such deprojections tend to overcorrect the CME speed for sources near the solar meridian. They result in speeds of the order of 5000-7000 km/s, which seem physically unreasonable. By considering the 3D extent of the CMEs, we provide a novel geometrical correction of the deprojected CME linear speed. The resulting speeds range from a few 100 km/s up to almost 2600 km/s, a much more physically acceptable correction. This study has important implications for Space Weather applications since the reliable estimation of the CME linear speed has a direct effect on the time of arrival of CMEs at Earth and the quantification of the expected peak flux of solar radiation storms.

Acknowledgement: This work was funded from the State Scholarships Foundation of Greece (I.K.Y.), in the framework of: "Funding Post-doctoral Researchers" of the b.p.: "Human Resources Development, Education and Lifelong Learning" from ESPA (2014-2020).

 
A novel artificial neural network for flood forecasting based on deep learning encoder-decoder architecture
Authors: Lin Kangling , Chen Hua , Xu Chong-Yu , Zhou Yanlai , Guo Shenglian
Published: March 2020

With the rapid growth of deep learning recently, artificial neural networks have been propelled to the forefront in flood forecasting via their end-to-end learning ability. Encoder-decoder architecture, as a novel deep feature extraction, which captures the inherent relationship of the data involved, has emerged in time sequence forecasting nowadays. As the advance of encoder-decoder architecture in sequence to sequence learning, it has been applied in many fields, such as machine translation, energy and environment. However, it is seldom used in hydrological modelling. In this study, a new neural network is developed to forecast flood based on the encoder-decoder architecture. There are two deep learning methods, including the Long Short-Term Memory (LSTM) network and Temporal Convolutional Network (TCN), selected as encoders respectively, while the LSTM was also chosen as the decoder, whose results are compared with those from the standard LSTM without using encoder-decoder architecture.

These models were trained and tested by using the hourly flood events data from 2009 to 2015 in Jianxi basin, China. The results indicated that the new neural flood forecasting networks based encoder-decoder architectures generally perform better than the standard LSTM, since they have better goodness-of-fit between forecasted and observed flood and produce the promising performance in multi-index assessment. The TCN as an encoder has better model stability and accuracy than LSTM as an encoder, especially in longer forecast periods and larger flood. The study results also show that the encoder-decoder architecture can be used as an effective deep learning solution in flood forecasting.
The Karakoram Predicament
Authors: Dasgupta Bibhasvata , Sanyal Prasanta
Published: March 2020

The anomalous behaviour of Karakoram Glaciers (Hewitt, 2005) in the backdrop of a warming planet has been a decade long debate baffling climatologists worldwide. While a lot of effort has been given to understand this behaviour, very little has been explored with respect to the factors that favour glaciation rates. A fundamental approach to glacial mass budget calculation involves a simplistic assessment of accumulation and melt. Analysis of meteorological datasets over the last 40 years yields conflicting scenarios. On one hand, we have observed a significant negative trend in winter rainfall and snowfall amount coupled with increasing surface temperatures and vertical mixing of atmospheric vapour. On the other hand, parameters that reflect the bulk of a cryospheric reservoir such as snow depth, dry snow/wet snow percentages show stable to increasing trend. Between lower moisture input and potential ablation rates, the steady-state nature of Karakoram glaciers have emulated optimism in the works of climatologists worldwide. In this study, we have tried to formulate an ‘accumulation index’ as a function of moisture input, surface temperature and atmospheric vertical circulation. Precipitation trends are negative yet periodic which suffices a positive accumulation rate. At the same time, local factors such as debris field and wet snow cover area help preserve the accumulated bulk of a given winter through the upcoming warm summers. However, in a potentially warming planet, accumulation rates aren't proportional to ambient temperature. Studies show that the mass balance turns sharply negative at temperatures above -10 °C due to accelerated ablation which overcompensates accumulation. This makes the Karakoram phenomenon a function of global meteorology rather than local factors i.e. debris cover, vorticity, etc. Therefore, we suggest that the Karakoram Glaciers aren’t behaving anomalously, but lagging in phase with central and eastern Himalayan glaciated regions.
Water vapor isotopic abundance measurement in Tibetan Plateau based on portable laser heterodyne radiometer
Authors: Lu Xingji , Huang Jun , Cao Zhensong , Huang Yinbo , Liu Dandan , Tan Tu , Rao Ruizhong
Published: March 2020

Tibet Plateau is known as the third pole of the world, the environmental changing in this area profoundly impacts on east Asian or even global climate. HDO is the stable isotope of water vapor and is the ideal tracer of water cycle, which has been applied to atmospheric circulation and climatic studies. For monitoring the water vapor isotopic abundance in Tibetan Plateau and providing reliable information for environmental and climatic studies, a portable laser heterodyne radiometer was operated at Golmud (Qinghai Province) in summer 2019. The radiometer adopted a narrow linewidth 3.66 μm DFB laser as the local oscillator and performed high resolution(~0.009 cm-1) and high signal-to-noise ratio(~160). Furthermore, the absorption spectra of atmospheric HDO and H2O were obtained and the retrieval algorithm of water vapor isotopic abundance was discussed. The optimal estimation method based on LBLRTM was chosen for retrieving, the ratio of HDO/H2O at Golmud is 185±7×10-6 during the observation, the value is less than the Vienna Standard Mean Ocean Water (VSMO, 311.5×10-6) but larger than Standard Light Antarctic Precipitation (SLAP, 178.2×10-6).
Recent degradation and transformation of grasslands in the Terai ecosystems of the Indian subcontinent
Authors: Banerjee Subham , Das Dhritiman , John Robert
Published: March 2020

The importance of grasslands for the sustenance of global biodiversity is paramount. Grassland ecosystems support rich and unique diversity at all trophic levels, are remarkably productive, and resilient to environmental changes. Grasslands in the Indian subcontinent are among the most threatened due to habitat loss, sparking renewed interest in the ecology of the different grasslands found here. We studied land cover dynamics of woodland-grassland mixtures that are part of the Terai ecosystems located at the base of the Himalayan mountain ranges. The vegetation in this region is known to be extremely dynamic even within short time scales, but the patterns and processes associated with this dynamism are not well understood. We analyzed the landcover changes at eight protected wildlife conservation areas from the region (four from India and four from Nepal) that occurred over the last three decades. We used the random forest classifier and an ensemble-based classification technique to carry out supervised classification of the land cover, which was dominated by vegetation. Landsat data, verified with a set of ground measurements and Google earth imagery, were used to generate the landcover types. Using the time series of land cover data, we quantified the observed transitions over decadal timescales. We then used Linear Discriminant functions and Bayesian spatial models to determine the relative importance of environmental variables influencing land cover transitions. We found that the area occupied by grasslands have reduced across all the protected areas we studied. In the last 30 years, the overall natural grassland area decreased by 24 percent, while the agricultural area doubled. The woodland cover increased by 28 percent as a result of ecological succession. Distance from human settlements was found to be the most crucial factor affecting the transitions, followed by topography and distance to water bodies. The grasslands are being widely transformed or degraded to early successional woodland and farmlands, and show increased alien plant invasions. Human encroachment and an increase in human activities have a major influence on these transitions. The impact of these changes on biodiversity and ecosystem function needs to be studied and the urgent attention of managers to stop further degradation is needed.
A Cloud Computing-based Micro-Unmanned Aerial Vehicle System for Geological Disaster Surveys
Authors: Xing Gloria , Zhang Mingzhi , Ma Juan , Huang Zack , Liu Cong
Published: March 2020

In recent years, Unmanned aerial vehicle (UAV) tilt photography, InSAR, LiDAR and other technologies have been used in the field of geological disaster surveys and research to varying degrees, with traditional field survey methods being unable to meet the requirements of rapid and subtilized geological surveys nowadays. Thanks to the rapid development of UAV tilt photogrammetry technology, UAVs have played an important role in geological disaster emergency investigations and geological surveys. However, there are still some problems with the application of UAVs: 1. Geological disaster investigators who commonly hold degrees in geology find it difficult to learn how to operate UAVs; 2. professional UAV pilot training involves high costs and long training cycles, and meanwhile, UAV platforms and their loaded multi-lens tilt cameras are of high value, which render UAVs impossible to use as a standard accessory for geological disaster investigation teams; and 3. professional 3D modelling software is expensive and requires highly configured computer hardware, and in field scenarios, it usually has poor timeliness in terms of data processing. A micro-UAV system, mainly consisting of a UAV flight path control app (supporting Android/IOS) and a web-based data processing cloud platform, has been developed to solve the problems emerging in UAV-based geological disaster surveys, such as the difficult data collection, slow data processing, and high human involvement. The system integrates existing consumer-grade micro-UAV hardware and our newly designed UAV path planning and photogrammetry modes applicable in geological disaster surveys to achieve the fast acquisition of images, DOM, DSM, 3D models and point cloud data for geological disaster survey areas, based on high-speed processing and multi-node distributed GPU cluster technology. The main goal of this micro-UAV geological disaster surveying system is to rapidly acquire, transmit, process and distribute large-scale three-dimensional geographic information for small areas. The UAV flight path control app features one-click take-off and automatic landing, and the web data-processing cloud platform can realize one-click automatic data processing. The system has good application prospects due to its low cost and easy operation, and the fact that it can be widely used as a standard accessory by teams in various geological disaster investigations.

Keywords: micro-UAV system, cloud computing, geological disaster survey, rapid and subtilized survey
Seventeen Years of the Canadian Arctic ACE/OSIRIS Validation Project at PEARL
Authors: Walker Kaley , Strong Kimberly , Fogal Pierre , Drummond James R.
Published: March 2020

Ground-based measurements provide critical data to validate satellite retrievals of atmospheric trace gases and to assess the long-term stability of these measurements.  As of February 2020, the Canadian-led Atmospheric Chemistry Experiment (ACE) satellite mission has been making measurements of the Earth's atmosphere for nearly sixteen years and Canada's Optical Spectrograph and InfraRed Imager System (OSIRIS) instrument on the Odin satellite has been operating for over sixteen years.  As ACE and OSIRIS continue to operate far beyond their planned two-year missions, there is an ongoing need to validate the trace gas profiles from the ACE-Fourier Transform Spectrometer (ACE-FTS), the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) and OSIRIS.  In particular, validation comparisons are needed during Arctic springtime to understand better the measurements of species involved in stratospheric ozone chemistry.

To this end, seventeen Canadian Arctic ACE/OSIRIS Validation Campaigns have been conducted during the spring period (February - April in 2004 - 2020) at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut (80N, 86W). For more than a decade, these campaigns have been undertaken in collaboration with the Canadian Network for the Detection of Atmospheric Change (CANDAC). The spring period coincides with the most chemically active time of year in the Arctic, as well as a significant number of satellite overpasses. A suite of as many as 13 ground-based instruments, as well as frequent balloon-borne ozonesonde and radiosonde launches, have been used in each campaign. These instruments include: a ground-based version of the ACE-FTS (PARIS - Portable Atmospheric Research Interferometric Spectrometer), a terrestrial version of the ACE-MAESTRO, a SunPhotoSpectrometer, two CANDAC zenith-viewing UV-visible grating spectrometers, a Bomem DA8 Fourier transform spectrometer, the CANDAC Bruker 125HR Fourier transform spectrometer, an EM27/SUN Fourier transform spectrometer, a Systeme d’Analyse par Observations Zenithales (SAOZ) instrument, a Pandora spectrometer, and several Brewer spectrophotometers. In the past several years, these results have been used to validate the measurements by the ACE-FTS, ACE-MAESTRO, and OSIRIS instruments as well as the TANSO-FTS instrument on the Japanese Greenhouse Gases Observing Satellite (GOSAT) and the TROPOMI instrument on the Sentinel 5 Precursor. This presentation will focus on an overview of the measurements made by the ground-based, balloon-borne and satellite-borne instruments during the recent ACE/OSIRIS Arctic Validation campaigns and highlight how these have been used for satellite validation.
Benchmark, predictability, and forecast skill of terrestrial water storage based on CMIP6 decadal hindcasts and land surface ensemble simulations
Authors: Zhu Enda , Yuan Xing
Published: March 2020

Terrestrial water storage (TWS), including surface water storage, soil water storage, and groundwater storage, is critical for the global hydrological cycle and freshwater resources. A reliable decadal prediction of TWS can provide valuable information for sustainable managements of water resources and infrastructures in the face of climate change. Generally, the hydrological predictability mainly comes from two sources, i.e., initial conditions and boundary conditions. To date, the dependence of TWS forecast skill on the accuracy of initial hydrological conditions and decadal climate forecasts is not clear, and the benchmark skill remains unknown. In this work, we use decadal climate hindcasts from CMIP and perform hydrological ensemble simulations to estimate a baseline decadal forecast skill containing the two predictability sources information for TWS over global major river basins with an elasticity framework that considers varying skill of initial conditions and climate forecasts. With the incorporation of decadal climate forecast, our benchmark skill for TWS incorporated is significantly higher than initial conditions-based forecast skill over 25% and 31% basins for the leads of 1–4 and 3–6 years, especially over mid- and high-latitudes. Although the decadal precipitation forecast skill based on individual model is limited, the ensemble forecasts from multiple climate models are better than individuals. In addition, the standardized precipitation index (SPI) predictability and forecast skill from the latest CMIP6 decadal hindcast data are being investigated. Preliminary results suggest that predictability and forecast skill of SPI are positively correlated in general, and the predictability is higher than forecast skill, indicating the room for improving hydro-climate forecast. Our findings provide a new benchmark for verifying the success of decadal TWS forecasts and imply the possibility of improving decadal hydrological forecasts by using dynamical climate prediction information which still has room for improvement.
Sensitivity of convective cell dynamics and microphysics to model resolution for lake-effect shallow convection
Authors: Jensen Anders , Geerts Bart , Bergmaier Philip
Published: March 2020

Shallow convection over an unfrozen lake (Lake Ontario) during a cold-air outbreak is simulated using the Weather Research and Forecasting model (WRF) with two horizontal grid spacings, 148 m and 1.33 km. The dynamics and microphysics of the simulated convective snow band are compared to radar and aircraft observations. The dynamical and microphysical changes that occur when going from 1.33-km to 148-m grid spacing are explored. Improved representation of the convective dynamics at higher resolution leads to a better representation of the microphysics of the snowband compared to radar and aircraft observations. Stronger updrafts in the high-resolution grid lead to larger ice nucleation rates and produce ice particles that are more heavily rimed and thus faster falling. These changes to the ice particle properties in the high resolution grid limit aggregation rates and result in more realistic radar reflectivity patterns. Graupel, observed at the surface, is produced in the strongest convective updrafts, but only at the higher resolution. Ultimately, the quantitative precipitation forecast is improved at a higher grid resolution. Additionally, the duration of heavy precipitation just onshore, where convection collapses, is better predicted.
Sensitivity of carbon fluxes to flash drought based on long-term FLUXNET and satellite observations
Authors: Zhang Miao , Yuan Xing
Published: March 2020

Flash drought is characterized by a rapid onset at subseasonal time scale and enormous impact on society and economics. However, only few extreme case studies assessed the impact of flash drought on vegetation, without specific definition to identify the rapidly intensification stage of flash drought. Here, we use soil moisture to identity flash drought events at in-situ and regional scales, and detect the response of vegetation photosynthetic function using eddy covariance and satellite observations of carbon fluxes and sun-induced chlorophyll fluorescence (SIF). Different vegetation types show high sensitivity to flash drought especially for savanna and grassland, and the lag time between flash drought and ecological response is usually 8-16 days. The resistance of woody plants can be attributed to the positive anomalies of inherent water use efficiency during flash drought. Vegetation over semi-arid and semi-humid is also vulnerable to flash drought. The quick response of vegetation to flash drought is a new challenge for drought monitoring.
Human Health Benefits of the Minamata Convention on Mercury
Authors: Zhang Yanxu
Published: March 2020

The Minamata Convention is a legally-binding international treaty aimed at reducing the anthropogenic release of mercury, a potent neurotoxin. However, its human health benefit has not been quantified at a global scale. Here we evaluate the Convention’s benefit by a coupled climate-atmosphere-land-ocean-ecosystem model and a human mercury exposure component that considers all food categories. We find the mercury health risk decreases nonlinearly with emission reduction, and the most optimistic scenario leads to mercury level in marine biota half of the present-day level. Our results show that the accumulated benefits of the Convention are 660 billion USD avoided earn loss (3% discount rate, realized in 2010) and 1.2 million avoided deaths from fatal heart attacks over the period 2010-2100, with substantial global human health cost if delaying emission reduction actions. Such a comprehensive modelling approach helps parties to evaluate the effectiveness of implementation as required by the Convention.
Impacts of Binary-interacted Typhoons Tembin and Bolaven in 2012 on Surges and Waves over the East China Sea
Authors: Yang Jie , Li Yong , Chen Meixiang
Published: March 2020

Typhoon-induced storm surges and waves are highly related with typhoon track and associated wind stresses and atmospheric pressures at sea surface. The effects of binary interaction may alter typhoon tracks and even forward speed, which might influence waves and surge heights in the ocean. In the present study, we execute a series of numerical experiments to investigate how isolated and binary typhoons would impact the ocean waves and generated surges offshore and nearshore. The responses of binary typhoons to sea level rise and land subsidence are also discussed. The Typhoon Tembin and Typhoon Bolaven influenced the East China Sea with equivalent intensity of tropical storm and Category 2, respectively, on the Saffir–Simpson hurricane wind scale. The Weather Research and Forecasting (WRF) model is utilized to hindcast the layered wind and atmospheric pressure fields above sea/land surface. Two synthetic scenarios isolating these individual typhoons are designed to investigate the potential impacts of the binary-interacted typhoons. By coupling with the SCHISM–WWMIII modelling system, the corresponding surge–tide–wave processes are solved and validated with measurements at tidal gauge and wave buoy stations. At the same time, The spatial-varied future relative sea level rise (RSLR) by the end of the century is projected from satellite altimeter data-based sea level analysis and is adjusted for the influence of the Glacial Isostatic Adjustment (GIA) using the ICE-6G/VM5a model. The results indicate that the surge and wave heights induced by these two typhoons were not exacerbated significantly, as the hours influencing the Yellow Sea by Typhoon Tembin were about 30 hours later than Typhoon Bolaven. We also present the spatial distribution of nonlinear responses of storm surge induced extreme sea levels to RSLR, implicating the regions of exacerbation and attenuation, respectively, due to future sea level trend. The present study helps identifying distribution patterns by binary-interacted typhoons and enhancing assessment accuracy of potential coastal hazards and flood risk.
Electrical conductivity of omphacite and garnet in eclogite: implications for water recycling in the mantle
Authors: Liu Hanyong , Yang Xiaozhi
Published: March 2020

Eclogite is an important constituent of subduction slabs and plays a critical role in transporting surface materials (e.g., water) into the deep Earth. Eclogite consists mainly of omphacite and garnet. Although nominally anhydrous, omphacite and garnet contain some amount of structural water (OH) in the lattice, which is up to >1500 ppm wt. H2O. This is virtually the highest content in nominally anhydrous minerals (NAMs) derived from the crust and upper mantle (Ingrin and Skogby, 2000). The electrical property of NAMs is very sensitive to water content and a small amount of water could dramatically enhance the conductivity. Thus, laboratory measured conductivity data of omphacite and garnet may help to understand the deep water recycling by eclogitized slab.

In this study, we have systemically determined the conductivity of omphacite and garnet with different water contents. The experiments were carried out at 350-800 °C, 1 GPa (note that the effect of pressure itself on conductivity is very small) and Ni-NiO buffered conditions. The data show that the conductivity of both omphacite and garnet increases with water content or temperature. The bulk conductivity is then modeled for different mineral compositions and water contents over a range of conditions (Liu et al., 2019). In combination with the geophysically documented high resistivity of the crustal part in deep subducted slabs, we suggest that the water content in omphacite and garnet in the deep-subducted eclogites should not be high at mantle depths. This provides new insights into the deep water recycling by subducted eclogites.

 

References:

Ingrin, J., and Skogby, H., 2000, Hydrogen in nominally anhydrous upper-mantle minerals: Concentration levels and implications: European Journal of Mineralogy, 12, 543–570.

Liu, H., Zhu, Q., and Yang, X., 2019, Electrical conductivity of OH-bearing omphacite and garnet in eclogite: the quantitative dependence on water content: Contributions to Mineralogy and Petrology, 174, doi:10.1007/s00410-019-1593-3.
Numerical modelling for evaluation of the nitrogen removal rate in hyporheic zone
Authors: Liu Suning , Chui Ting Fong May , Kuang Xingxing
Published: March 2020

The hyporheic zone (HZ), the region beneath or alongside a streambed where active groundwater and surface water mix, plays a vital role in the stream ecosystem. Reactions in the HZ such as denitrification and nitrification have been examined in previous studies. However, those numerical models are lack of consideration for the reaction zones for aerobic and anaerobic changes due to the reactions consuming the dissolved oxygen (DO) in hyporheic flux. In order to simulate nitrogen concentration changes in the HZ more accurately, this study proposes a method of evaluating the nitrogen removal rate in the HZ through numerical modeling. Firstly, a basic two-dimensional numerical model following previous simulation models in the HZ, which only couple flow conditions with biochemical reactions, is proposed to consider both nitrification and denitrification, but ignoring the changes generated by the reactions. Next, the zones for different reactions are determined in an improved model under the assumption that related environmental variables (i.e., the DO) will be considered to delineate the boundary between nitrification and denitrification zones and to identify a transition zone where either reaction might take place. The changes of reaction zones through the whole process can be controlled by the characteristic variable of hyporheic flux, and this variable can be selected differently for different reaction processes. In this study, the characteristic variable is determined as median residence time. Using this model, the accuracy of the nitrogen simulation in the HZ can be improved. To overcome the shortcoming that more information about biochemical reactions in the HZ is required to use the improved model, a new model that couples the basic model and genetic programming (GP) is proposed to optimize the simulation results of the basic model and allow for real-time forecasting. The results show that the improved model performs better than the basic model, but the model coupling the basic model with GP performs best. In addition, the function of the HZ in nitrogen removal is examined through a case study of four scenarios, leading to the conclusion that the HZ has a higher nitrogen removal rate when water quality is neither too poor nor too good. Therefore, even though the HZ facilitates nitrogen removal, sewage should still be treated to a certain level before being discharged into rivers. Overall, this study enhances our understanding of the HZ, and can benefit the restoration and management of HZs and streams in the face of the continual degradation caused by human activity.
The seismic structure of the West Iberian continent-ocean transition
Authors: Merino Perez Irene , Prada Manel , R. Ranero César , Sallares Valenti , Grevemeyer Ingo , Calahorrano Alcinoe , L. Cameselle Alejandra , Neres Marta
Published: March 2020

The West Iberian margin has been studied since the 1980 to mid 1990’s when some of the most emblematic geophysical cross-sections and borehole samples were collected in the area. Despite of this wealth of information, there is little understanding on how the transitional domain, commonly interpreted as exhumed mantle, transitions into oceanic crust. The lack of appropriate geophysical data makes the nature of the basement, and thus the origin of the structures, still debated. Also, the mechanisms of thinning occurring in the continental-ocean transition are poorly constrained due to data quality or methodological limitations.

Here, we present spatially coincident multichannel seismic (MCS) and wide angle seismic (WAS) data collected during the FRAME-2018 survey across the Tagus Abyssal Plain, South-West the Iberian margin. The MCS data were recorded with a 6-km-long streamer, while 17 Ocean Bottom Seismometers and 18 Ocean Bottom Hydrophones were deployed each 10 km and used to record the WAS data, both along a 350 km-long, E-W trending profile located at 38º N, and crossing the Tagus Abyssal Plain.

The MCS time-migrated seismic section provides a high-quality image from which we interpret the tectono-stratigraphic structure from the continent to the ocean, ~180 km eastwards from the J-anomaly. The seismic image shows three main domains: a first domain closest to the continent with tilted fault blocks with possible syn-rift sediments and a possibly continental basement. In this domain, there is high-reflectivity reflections at 1-2 s TWT from the top of the basement. Then, westwards, a domain displays gentle basement-top topography, high intra-basement complex reflectivity and deep-penetrating landward dipping reflections. No clear Moho reflection occurs. A third domain to the west correspond to a very smooth and highly reflective top of basement coincident with the magnetic J-anomaly. Further west top basement shows an irregular topography with comparatively numerous short tilted blocks.

We use refracted and reflected travel-times (TT) WAS and MCS field data to jointly invert for P-wave velocity (Vp) and the geometry of interfaces in the sediment, the top of the basement, and Moho. Combining MCS TT with WAS TT allows retrieving the Vp structure of the shallow part of the model and the geometry of seismic interfaces with a level of resolution that is beyond what can be obtained with WAS TT alone. The result of this joint WAS-MCS tomography is a Vp model of the margin that is fully consistent with the MCS image along the whole profile. The preliminary models show that the crustal structure is laterally more complex than previously modelled, presenting sharp boundaries between at least 5 different domains from the base of the continental slope to the ocean basin.
Head-to-head encountering dune-fields under reversing flows in the Beibu Gulf, South China Sea
Authors: Ma Xiaochuan , Gan Yu , Yan Jun
Published: March 2020

Dunes and dune-fields, being indicators and recorders of environmental conditions, have attracted extensive attentions and are massively studied on the individual behaviors and dune-dune interactions. However, the processes of field-field interaction are still elusive. Here, using the latest bathymetric datasets, we presented the new-found dune fields developing under reversing tidal currents on a shallow shelf, northwest South China Sea. The dune fields separately had dunes with opposite inclination and were head-to head colliding with a coarse-coarse pattern and a coarse-fine pattern in term of the sediment character. The dune-field fronts defined by the transition of dune asymmetry were outlined, where convergent bed load transports coexisted with divergent suspended load transports. The dunes had apparent spatial variability in their scale and morphology across the dune fields. Dunes obtained steeper shapes towards the dune-field fronts due to the different responses of height and length when dune-fields met together, which were benefited from the bidirectional sand supply and the comparable reversing current speed. Dune scale also exhibited distinct variations towards the dune-field fronts, suggesting the past dominant southward migration of the north fields and the resistance of the south fields. From 2014 to 2016, dunes inside the dune fields mostly moved to their inclining direction while some dunes in the dune-field fronts migrated to oppositely. The dune-field fronts shifted oppositely in various regions because of the rebalance of sand transports, which are inferred to essentially result from the regional flow changes. The migrating rates of the fronts are also influenced by the magnitude of grain size, water depth, dune height, and current speed. The behaviors of dune-field fronts can possibly record the interactions between dune-field and local environmental changes. More studies are still required on the internal structures of dunes near dune-field fronts and the modelling of local effects of regional environment modification.
Ecosystem-based approaches to disaster risk reduction in Japan: transdisciplinary research and actions
Authors: Yoshida Takehito
Published: March 2020

Natural disasters occur at an increasing rate probably due to the ongoing climate change, and adaptation to natural disaster risks is a key to the sustainability of local communities in Japan. At the same time, Japan is experiencing a rapid decline of human population and consequent aging. Ecosystem-based approaches to disaster risk reduction (Eco-DRR) takes advantage of the multi-functionality of ecosystems and biodiversity, including their capacity to mitigate natural disasters while providing multiple ecosystem services, and population decline provides ample opportunity for implementing Eco-DRR. We are developing practical solutions for implementation of Eco-DRR by visualizing natural disaster risks, evaluating multi-functionality of Eco-DRR solutions, conducting transdisciplinary approaches in collaboration with diverse stakeholders, and advocating traditional and local knowledge of disaster risk reduction. I will talk about some progress of our ongoing research project in RIHN (Research Institute for Humanity and Nature), Japan.
Study on spacial-correlation between water pollution and industrial agglomeration in the developed regions of China
Authors: Shi Li-hong
Published: March 2020

Abstract: Agglomeration of the manufacturing industries is not only a fundamental driving force for urban development However, a large number of manufacturing industries produce sewage and thus have negative effects on regional environment. This study first estimates the degree of clustering of pollution intensive manufacturing industries in the developed region of China at city level by introducing the Kernel density distribution function, and then evaluates the pollution distribution pattern by dividing the study area into several environmental units according to the naturally integrated characteristics of the primary streams. Furthermore, we quantitatively analyze the mechanism of the response of water environment quality to industrial distribution by utilizing the bi-variate spatial autocorrelation model. Results show that pollution-intensive manufacturing industries form clusters in suburban and non-sensitive areas. Besides, the density of pollution sources gradually decreases from the chief canals to the peripheral areas. Spatial autocorrelation analysis shows that spatial-relationships show differences according to industry categories: the agglomeration of textile, petrochemical and metallurgical industries prominently affects the spatial heterogeneity of water pollution distribution while the effects of the agglomeration of food manufacturing and paper-making industry on water pollution are not significant. Based on the spatial autocorrelation between industrial agglomeration and pollution distribution, we divide the study area into four types: high-agglomeration and high-pollution area, low-agglomeration and low-pollution area, low-agglomeration and high-pollution area, high-agglomeration and low-pollution area. Based on the that, we analyze the formation scheme and provide policy suggestions regarding industrial development. This paper provides a new perspective for the study of the interaction between industrial agglomeration and environment effects, and will be benefit the sustainable development of cities.

Key words: industrial agglomeration; Kernel Density Distribution function; water pollution; manufacturing industry; spatial autocorrelation
Influence of Upslope Fog on Hygroscopicity and Chemical Composition of Aerosols at a Forest Site in Taiwan
Authors: Chen Chia-Li , Chen Ting-Yu , Hung Hui-Ming , Tsai Ping-Wen , Chen Wei-Nai , Chou Charles C.-K.
Published: March 2020

This study investigated the influence of upslope fog formation on the chemical composition and single hygroscopicity parameter (κ) of rural aerosols. The compositions were monitored using a mini compact time-of-flight aerosol mass spectrometer (mini-C-ToF-AMS), and a scanning mobility particle sizer (SMPS) from Dec. 1st to Dec. 24th, 2018 at the Xitou forest site (23.40°N, 120.47°E, 1,178 m asl) in Taiwan. Ambient wet aerosol particles were collected by a 13-stage nano-MOUDI II impactor (micro-orifice uniform deposit impactors) and analyzed using a Fourier-transform infrared spectrometer with an attenuated total reflectance accessory (FTIR-ATR). The single hygroscopicity parameter (κ) of aerosols derived from the comparison of AMS pToF size distribution using the κ-Köhler equation and FTIR-ATR measurement. The moderate correlation (r = 0.73) between the oxidized oxygenated organic aerosol (OOA) and CO evidenced the upstream anthropogenic emission transport by sea/land breezes. The decreasing (aerosol mass)/CO ratio with decreasing visibility trends during in-fog periods at two dense foggy events indicated that the fog activation scavenging mechanism dominated the aerosol particle removal. The inconsistency of online real-time AMS and offline FTIR-ATR measurement for submicrometer particles indicated that the evaporation loss of HNO3 or NH4NO3 particles during MOUDI filter sampling could lead to the unavailable κ retrieval for nitrate-containing particles at non-foggy daytime and the discrepancy of aerosol acidity. Similar κ ranges of organic carboxylic acid group particles (0.1 < κp-org < 0.3), ammonium-containing, and sulfate-containing particles (0.2 < κp-NH4 or κp-SO4< 0.5) but ambiguous nitrate-containing particles (0.4 < κp-NO3 < 0.6 or 0.6 < κp-NO3 < 0.8) were observed at foggy daytime, suggesting that ammonium sulfate and organic carboxylic acid compounds were more likely internal mixture particles with similar hygroscopicity and physicochemical mixing state influenced by upslope fog. However, the distinct κ ranges of sulfate-containing particles (0.5 < κp-SO4 < 0.7 or 0.6 < κp-SO4 < 0.8) and organic carboxylic acid group particles (0.1 < κp-org < 0.2) revealed the different chemical and physical properties of external mixture particles at non-foggy daytime.

 

 
A New MODIS C6.1 and MERRA-2 Merged Aerosol Products: Validation over The Eastern Mediterranean Region
Authors: Shaheen Abdallah
Published: March 2020

In this study, we used long-term (2003–2018) aerosol datasets acquired from Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2),  along with two products of MODerate resolution Imaging Spectroradiometer (MODIS)/Terra and Aqua, Collection 6.1(C6.1) and Level 2 (L2), to conduct a comprehensive validation of Aerosol Optical Depth (AOD) using 9 AERONET sites with continuous observations for at least 1 year over the Eastern Mediterranean (EM) region. In order to reduce the number of missing cells from the satellite instruments and produce a near-daily dataset, the “Dark _Target _Deep_Blue_AOD _550_Combined” (DTDB) for both Tera and Aqua at 550 nm were merged, and named as MODIS AOD. The MODIS and MERRA-2 AODs at high spatial resolution (10 km × 10 km and 50 km× 62.5 km, respectively) were resampled to 100 km spatial grid, using the nearest neighbor interpolation technique to overlap the pixels of each other, and to match the full field view of AERONET.Using the 9 collected AERONET observations, the overall performance of the daily MODIS and MERRA-2 AODs over the EM region was validated first. The results showed a significant spatial agreement between these AODs and ground-based AOD, with an acceptable bias (For MODIS: R=0.71, RMSE=0.12, MAE= 0.09, MFE= 40.3% and IOA= 0.81), (For MERRA-2: R=0.75, RMSE=0.10, MAE= 0.06, MFE= 32.1% and IOA=0.83) Moreover, the monthly mean of these AODs were also validated using the monthly mean of the AERONET observations.  The results also showed significant spatial agreement, with an acceptable bias (For MODIS: R=0.78, RMSE=0.06, MAE= 0.05, MFE= 23.7% and IOA =0.79) and (For MERRA-2: R=0.83, RMSE=0.04, MAE= 0.03, MFE= 19.5% and IOA=0.86).The obvious over estimation of daily and monthly mean in the performance of MODIS AOD [i.e., (for daily; RMB=1.2, FGE=24.4%) and (for monthly; RMB=1.21, FGE=20.1%)], and the under estimation of MERRA-2 AOD [ i.e., (for daily; RMB=0.86, FGE=-9.34% ) and (for monthly RMB=0.87, FGE=-13.2%)], should not be overlooked. Due to these systematic under-over estimation error, a new merged AOD product of MERRA-2 and MODIS named as MERRA-2 MODIS Merged AOD (MMM) was generated, on daily time series data during the years 2003-2018 using the combination method. The MMM performance results not only indicated an agreement between the MMM AOD and AERNONT AOD higher than MODIS and MERRA-2 [ i.e., (for daily; R=0.77, RMSE=0.09, MAE= 0.05, MFE= 31.3% and IOA=0.86) and (for monthly; ( R=0.86, RMSE=0.04, MAE= 0.02, MFE= 14.03% and IOA=0.92)] , but also it showed an efficient estimation closer to line1:1 [ i.e., (for daily; RMB=0.99 and FGE=6.6%) and (for daily; RMB=1.03 and FGE=5.5%)]. 
Ultramafic rocks at the Isua supracrustal belt and East Pilbara Terrane are crustal cumulates, not slices of early mantle
Authors: Zuo Jiawei , Webb Alex , Harvey Jason , Haproff Peter , Mueller Thomas , Byerly Gary , Hickman Arthur , Wang Qin
Published: March 2020

The initiation of plate tectonics remains enigmatic, with the proposed onset timing ranging from Hadean to Proterozoic. Recently, many mineralogical, petrological and geochemical studies suggest onset of plate tectonics at ~3 Ga. For example, the geology of East Pilbara Terrane (~3.55 to 2.70 Ga; Australia) is widely interpreted as representing Paleoarchean non-plate tectonics, followed by plate tectonics after a ~3.2 Ga transition. In contrast, Isua supracrustal belt (3.85 to 3.55 Ga; Greenland) has been dominantly interpreted via plate tectonics. There, two ultramafic lenses have been interpreted as depleted mantle slices, emplaced via thrusting in an Eoarchean subduction zone, implying early plate tectonics. We present new petrological and geochemical data of ultramafic samples from the Isua lenses and from the East Pilbara Terrane to explore their origins. Pilbara samples appear to preserve cumulate textures; protolith textures of Isua samples are altered beyond recognition. Samples with low chemical alteration show similar whole-rock chemistry, including up to 5.0 wt.% Al2O3 and up to 0.25 wt.% TiO2 that both covary negatively with MgO (37.1 to 47.5 wt.%); these variations suggest cogenetic relationships with local lavas. Flat trace-element fractionation trends parallel those of local lavas in the primitive-mantle normalized spider diagram. Spinel crystals from Pilbara samples yield ~20-60 Mg#, relatively constant Cr# at ~70, and 0.61-4.81 wt.% TiO2. Our data are consistent with crustal cumulate emplacement. In contrast with depleted mantle rocks, our samples have higher whole-rock Al2O3 and TiO2, flat (vs. upward) trace-element fractionation trends from less to more compatible elements, and spinel crystals with higher TiO2 and relatively constant (vs. varied) Cr#. Therefore, Isua and Pilbara ultramafic rocks may have similar, non-plate tectonic origins, and the Isua record allows a ~3 Ga onset of plate tectonics.