bluuebunny/crossref_metadata_2025 huggingface dataset:
Amalgam and Dissolved Mercury Removal A system not just a Separator
Authors: Purves William
Published: March 2020

 

 

Abstract

 

Title: Amalgam and Dissolved Mercury Removal  A system not just a Separator

 

Content

 

Packs Solutions LLC has developed an amalgam and dissolved mercury system that significantly reduces the mercury discharge from the dental practice. The US American Dental Association estimates that 50% of the mercury entering the waste treatment facility is from dental practices.  The system consists of an innovative chairside trap, use of pH neutral vacuum line cleaners and disinfectants, and advanced technology separator that removes the dissolved mercury from the office discharge.  The system is currently in use in the United States and is rapidly gaining popularity with wastewater treatment authorities.

 

The presentation provides data taken from dental offices and the affect of pH on the dissolving of amalgam in water. The average dental office generates over 14,000 ng/L of dissolved mercury that can not be removed by traditional waste treatment processes.  The system has proven to reduce the discharge to <1,000 ng/L on average.  The system requires no changes in office routine or equipment. The separator is maintenance free and the chairside trap is custom made to fit in any brand of trap.  The average annual cost in the United States is as low as $420 for one chair practice to $1300 for a 6 chair practice.

 

 

 

Bill Purves

 

Packs Solutions LLC
Processing and analysis of dense ice velocity time series to reconstruct seasonal fluctuations of 3 greenlandic glaciers : Russell Gletscher, Upernavik Isstrom, Petermann Gletscher.
Authors: Derkacheva Anna , Mouginot Jeremie , Millan Romain , Gillet-Chaulet Fabien
Published: March 2020

Significant seasonal changes in ice flow have been reported for outlet glaciers in Greenland. Understanding the mechanisms that control these rapid intra-annual changes in dynamics could potentially help to clarify Greenland's long-term evolution and climate change response.

In this study, we investigate seasonal changes in ice flow velocity in order to better understand the processes controlling them. We focus on 3 Greenlandic glaciers of different types: Russell which is a land-terminating glacier with speed ranging from 50 to 350 m/yr,  Upernavik Isstrøm which is a marine-terminating tidewater glacier with speeds up to 4 km/yr, and Petermann Gletscher that has a large ice shelf and with speed at the order of 1 km/yr. Since 2014, the number of spaceborne observations over the ice sheet has increased dramatically with the launch of Landsat-8, Sentinel-1 and -2, providing almost continuous monitoring of glacier dynamics.

Here, we develop an automatic processing chain to derive dense time series of surface ice flow from radar sensors, Sentinel -1a/b, and optical sensors, Landsat-7/8 and Sentinel-2, using speckle or feature tracking algorithms. We construct a post-processing analysis based on local polynomial regression to filter our multi-sensor time series and create a velocity database with high temporal resolution and reduced noise. The database allows us to reconstruct the continuous evolution of surface ice velocity with frequency intervals ranging from monthly for the entire glacial basin to weekly for the downstream parts. 

Using this methodology, we obtain velocity fields for 4 years between 2015 and 2019 of the entire basins of Russell, Upernavik and Petermann glaciers. Our results clearly show the seasonal variations in flow to which these glaciers are subjected. We analyze the average seasonal fluctuations during the 4 years, as well as particular behavior in different years. These results are then compared and discussed in relation to potential external forcings such as subglacial hydrology (change in basal friction), fluctuations in the ice front or grounding line positions (change in buttressing) and the presence of sea ice or ice melange in front of the glaciers. 

Finally, we conclude on the benefits of our post-processing approach for the analysis of dense ice flow time series and provide first insights on the causes of seasonal variations observed on these 3 glaciers.
Decadal carbon balance and its response to 2 degree warming among heterogenous Arctic landscapes
Authors: Kou Dan , Virtanen Tarmo , Räsänen Aleksi , Juutinen Sari , Aurela Mika , Heiskanen Lauri , Guo Mingyang , Zhuang Qianlai , Treat Claire , Korhola Atte , Shurpali Narasinha
Published: March 2020

The large amounts of carbon (C) stored in the Arctic region can strongly interact with the climate system through the exchange of carbon dioxide (CO2) and methane (CH4) under the unmitigated environmental changes. Currently, there are still large uncertainties in the C exchange and the subsequent C-climate feedbacks between the land and atmosphere across the Arctic region, to which the highly heterogeneous landscapes make a key contribution. However, our knowledge on the present and future ecosystem C balance jointly considering the exchange of CO2 and CH4 in the Arctic region with heterogeneous landscapes is still limited. In this study, a process-based biogeochemistry model was calibrated and validated using the empirical data on concurrently measured CO2 and CH4 exchange observed using eddy covariance, automatic and manual chamber methods and associated climate, soil and plant data derived from several heterogeneous landscapes in the Kaamanen region. With the validated model, decadal C balance during 2005-2018 and its response to 2 oC warming were evaluated for the constituent land cover types (LCTs). Our results showed that most LCTs were a sink for atmospheric CO2 and a source of CH4 during 2005-2018. Under the 2 oC warming scenario, most ecosystems continued to be CO2 sinks and CH4 sources. Moreover, the CO2 budget in most LCTs did not change significantly as the two major fluxes of gross primary productivity (GPP) and total ecosystem respiration (TER) increased simultaneously thus maintaining similar rates of net ecosystem exchange (NEE) in response to warming, while a significant increase in CH4 emission from most LCTs was evident. Our results presented here provide us a better understanding and prediction of C dynamics and the inherent C-climate feedbacks in the Arctic region.
Synergetic use of Planet data and high-resolution aerial images for windthrow detection based on Deep Learning
Authors: Brandmeier Melanie , Deigele Wolfgang , Hamdi Zayd , Straub Christoph
Published: March 2020

Due to climate change the number of storms and, thus, forest damage has increased over recent years. The state of the art of damage detection is manual digitization based on aerial images and requires a great amount of work and time. There have been numerous attempts to automatize this process in the past such as change detection based on SAR and optical data or the comparison of Digital Surface Models (DSMs) to detect changes in the mean forest height. By using Convolutional Neural Networks (CNNs) in conjunction with GIS we aim at completely streamlining the detection and mapping process.

We developed and tested different CNNs for rapid windthrow detection based on Planet data that is rapidly available after a storm event, and on airborne data to increase accuracy after this first assessment. The study area is in Bavaria (ca. 165 square km) and data was provided by the agency for forestry (LWF). A U-Net architecture was compared to other approaches using transfer learning (e.g. VGG32) to find the most performant architecture for the task on both datasets.  U-Net was originally developed for medical image segmentation and has proven to be very powerful for other classification tasks.

Preliminary results highlight the potential of Deep Learning algorithms to detect damaged areas with accuracies of over 91% on airborne data and 92% on Planet data. The proposed workflow with complete integration into ArcGIS is well-suited for rapid first assessments after a storm event that allows for better planning of the flight campaign, and first management tasks followed by detailed mapping in a second stage.
On the role of tropical waves triggering extreme rainfall and flood in Sulawesi, Indonesia: a multi-scale interaction perspective
Authors: Latos Beata , Lefort Thierry , Flatau Maria , Permana Donaldi , Flatau Piotr , Baranowski Dariusz , Paski Jaka , Makmur Erwin , Sulystyo Eko
Published: March 2020

On January 22, 2019 extreme rainfall in the South-Western Sulawesi, Indonesia, triggered a massive, deadly flood, the most devastating one ever reported. This happened during an interaction of a robust Convectively Coupled Kelvin Wave (CCKW) and Equatorial Rossby Wave (ER). Potential causes of a flood include Madden Julian-Oscillation active phase, rainy season with monsoonal flow in the Karimata Strait, positive sea surface temperature anomalies supportive of convection, and synoptic-scale weather systems. All these factors can contribute to extreme rainfall and a flood development. Nonetheless, here we show that in this particular case enhancement of low-level westerlies led to convergence and forced ascend of moist air over orographic features of the south-western Sulawesi. This chain of processes was a result of a propagation of a CCKW, with contribution from an ER. Satellite and radar data analysis, as well as in-situ observations reveal that convergence and strong westerlies in the Java Sea, forced by the CCKW, resulted in the rain events in Jeneberang River Basin and the devastating flood in the city of Makassar.

Additional analysis of 20 years of the flood database together with in situ observations and satellite data support our hypothesis, based on this case study, of a significance of an enhanced westerlies as a precursor of extreme rain events and floods in Makassar, the capital and most populous city in Sulawesi.
Sphagnum reintroduction under a warming climate: keys to success
Authors: Limpens Juul , Tomassen Hilde
Published: March 2020

Restoring peatland functioning is closely related to restoring growth of ecosystem engineering Sphagnum species. In strongly degenerated peatlands reintroducing diaspores of Sphagnum is necessary to overcome strong dispersal and establishment bottlenecks. Which reintroduction strategy varies between peatland types, surface properties and/or microclimate. Comparative analyses of restoration techniques is scarce, hampering informed management choices.    

We set out to assess keys to success for Sphagnum reintroduction on strongly humified bare peat in three degraded and long-time rewetted temperate peatlands in the Netherlands. To this end we experimentally manipulated water table position (control, extra water), type of abiotic shelter (control, nurse plants, mulch), Sphagnum species (S. magellanicum, S. papillosum and S. cuspidatum), species mixture (monoculture, mixed culture), diaspore size (clumped intact plants or fragments) and diaspore density (0, 36, 72, 156 plants/m2) and monitored Sphagnum survival, lateral expansion and environmental conditions. The experiment was established in 2018 and repeated in 2019, covering two of the most extreme summers in recorded history.

Water table close to the surface and shelter of a mulch layer were key to Sphagnum survival and growth irrespective of Sphagnum species, reintroduction method or year. Survival increased linearly with diaspore density. Diaspore size showed an interaction with mulch cover: fragments did best under mulch cover, whereas clumped plants survived better outside shelter.

Taken together our results suggest that successful reintroduction of Sphagnum is possible under a warming climate, but that strategies should be strongly focussed on amelioration of abiotic stress even when water tables are close to the surface.
The Sailor-diagram. An extension of the Taylor diagram to two-dimensional variables for verification of model data.
Authors: Saenz Jon , Carreno-Madinabeitia Sheila , Esnaola Ganix , González-Rojí Santos J. , Ibarra-Berastegi Gabriel , Ulazia Alain
Published: March 2020

A new diagram is proposed for the verification of vector quantities generated by individual or multiple models against a set of observations. It has been designed with the idea of extending the Taylor diagram to two-dimensional vector such as currents, wind velocity, or horizontal fluxes of water vapour, salinity, energy and other geophysical variables. The diagram is based on a principal component analysis of the two-dimensional structure of the mean squared error matrix between model and observations. This matrix is separated in two parts corresponding to the bias and the relative rotation of the empirical orthogonal functions of the data. We test the performance of this new diagram identifying the differences amongst a reference dataset and different model outputs using examples wind velocities, current, vertically integrated moisture transport and wave energy flux time series. An alternative setup is also proposed with an application to the time-averaged spatial field of surface wind velocity in the Northern and Southern Hemispheres according to different reanalyses and realizations of an ensemble of CMIP5 models. The examples of the use of the Sailor diagram show that it is a tool which helps identifying errors due to the bias or the orientation of the simulated vector time series or fields. An implementation of the algorithm in form of an R package (sailoR) is already publicly available from the CRAN repository, and besides the ability to plot the individual components of the error matrix, functions in the package also allow to easily retrieve the individual components of the mean squared error.
Outcomes of a quantitative analysis of 46 soil chronosequence studies: Vegetation plays the key role for rates of podzolization in most environments.
Authors: Zwanzig Lisa , Zwanzig Martin , Sauer Daniela
Published: March 2020

Soil formation is controlled by climate, vegetation, organisms, topography, parent material and time. There are various hypotheses on the relative importance of these individual soil-forming factors. The quantitative influence of each soil-forming factor on the expression and rates of soil-forming processes, and in particular the influence of the different factors in combination, have not yet been sufficiently analyzed. The aim of this study was to quantify the influence of the soil-forming factors on the rates of podzolization. For this purpose, we compiled published data from 46 soil chronosequence studies in a database. These studies contained altogether 231 soil profiles of known age, on which we tested existing hypotheses on the influence of different soil-forming factors. The formation of an E horizon and its increase in thickness over time is one of the characteristic features of Podzol formation. As it is one of the few features that was described in all 46 studies, we used it as an indicator of progressive podzolization. Through statistical analysis, we investigated how E horizon thickness is affected by latitude, longitude, mean annual precipitation, mean annual temperature, range between minimum and maximum monthly temperature, annual number of days with frost, vegetation class (pioneer, deciduous and coniferous), sand content, clay content, and soil age.

Since E horizon thickness exhibited a zero-inflated (semi-)continuous distribution, we opted for a zero-altered gamma (ZAG) model, consisting of a Bernoulli and a Gamma part. The Bernoulli part shows, how the probability of the presence of an E horizon changes with soil age and environmental conditions. The Gamma part of the ZAG model allows for capturing the effects of the covariates on E horizon thickness. Our results indicate that vegetation is the most important factor for both (1) the soil age at which podzolization starts (used indicator: first occurrence of an E horizon), and (2) the rates of podzolization thereafter (used measure: increase of E horizon thickness with soil age). Climatic factors such as mean annual precipitation and range of temperature play subordinate roles. They are important for the soil age at which podzolization starts but less important for the rates of podzolization. We did not identify a significant influence of sand content, neither on the start nor the rates of podzolization. Thus, this statistical assessment of global data provides new insights into the relative importance of the individual soil-forming factors on the onset and temporal course of podzolization.
Towards the implementation of a transient gravity wave drag parameterization in atmospheric models
Authors: Bölöni Gergely , Kim Young-Ha , Borchert Sebastian , Achatz Ulrich
Published: March 2020

The aim of the presented work is to improve the parameterization of subgrid-scale gravity wave (GW) effects on the resolved flow in atmospheric models in a large altitude range from the upper troposphere to the mesopause (~85km). State of the art GW parameterization schemes are using the steady-state approximation for the wave field and therefore assume an instantaneous GW propagation neglecting direct interactions between the GW field and the resolved flow within the whole altitude range mentioned above. As such, these schemes rely on dissipative processes - GW breaking and critical layer filtering - as the only mechanism to accelerate/decelerate the resolved flow. In contrast to this, by dropping the steady-state assumption a contribution to the mean-flow forcing emerges in the form of direct GW-mean-flow interactions. Several idealized studies show that, besides dissipative effects, direct GW-mean-flow interactions contribute to GW dynamics in an important extent (Bölöni et al., 2016, J. Atmos. Sci.}, 73, 4833-4852, Wilhelm et al., 2018, J. Atmos. Sci., 75, 2257-2280, Wei et al., 2019, J. Atmos. Sci., 76, 2715-2738). This motivates the implementation of a transient GW model (MS-GWaM: Multi Scale Gravity Wave Model) to UA-ICON, the upper atmosphere version of ICON (Borchert et al., 2019, Geosci. Model Dev., 12, 3541-3569) which does not rely on the steady-state assumption and thus includes direct GW-mean-flow interactions. As a reference and a representative of currently available GW parameterization schemes a steady-state version of MS-GWaM (ST-MS-GWaM) has been implemented to UA-ICON as well, which shares the treatment of all possible components (wave sources and wave saturation scheme) with the transient MS-GWaM scheme and differs from it "only" in the treatment of propagation, i.e. excluding direct GW-mean-flow interactions and thus transience. Both MS-GWaM and ST-MS-GWaM reproduce the observed wind and temperature climatology (e.g. URAP data: Swinbank, R. and D. A. Ortland, 2003, J. Geophys. Res., 108, D19, 4615) reasonably well, but the transient propagation makes a robust difference in the circulation in perpetual runs. The transient propagation in MS-GWaM substantially contributes to an increase of the GW intermittency in the whole altitude range, giving a better comparison with super-pressure balloon observations (e.g. Hertzog et al., 2012, J. Atmos. Sci., 69, 3433-3448), whereas the lack of transience prevents any occurrence of higher GW momentum flux values than the launch magnitude itself. This is explained by the fact that the direct GW-mean-flow interactions involve a highly transient evolution of the wave action and the vertical group velocity, which often leads to increased pseudo-momentum fluxes as compared to the launch magnitude.
Surface and subsurface Labrador Shelf water mass conditions during the last 6,000 years
Authors: Lochte Annalena , Schneider Ralph , Repschläger Janne , Kienast Markus , Blanz Thomas , Garbe-Schönberg Dieter , Andersen Nils
Published: March 2020

The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland Currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late Deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7,000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening and sea ice cover on the Labrador Shelf during the last 6,000 years. Our records reveal that the LC underwent three major oceanographic phases from the Mid- to Late Holocene. From 6.2 to 5.6 ka BP, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka BP, possibly associated with the late Holocene Thermal Maximum. Although surface waters on the Labrador Shelf cooled gradually after 3 ka BP in response to the Neoglaciation, Labrador Shelf subsurface/bottom waters show a shift to warmer temperatures after 2.1 ka BP. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last two millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation. This study was conducted within the HOSST research school with the aim to improve our understanding of the critical processes involved in the North Altantic thermohaline circulation, which is particularly important in light of current climate change. 
A Cluster Analysis of PM2.5 Using CMAQ Model Results for Representativeness of Air Quality Monitoring Networks in Busan, Korea
Authors: Jung Woo-Sik , Do Woo-Gon
Published: March 2020

With increasing interest in air pollution, the installation of air quality monitoring networks for regular measurement is considered a very important task in many countries. However, operation of air quality monitoring networks requires much time and money. Therefore, the representativeness of the locations of air quality monitoring networks is an important issue that has been studied by many groups worldwide. Most such studies are based on statistical analysis or the use of geographic information systems (GIS) in existing air quality monitoring network data. These methods are useful for identifying the representativeness of existing measuring networks, but they cannot verify the need to add new monitoring stations. With the development of computer technology, numerical air quality models such as CMAQ have become increasingly important in analyzing and diagnosing air pollution. In this study, PM2.5 distributions in Busan were reproduced with 1-km grid spacing by the CMAQ model. The model results reflected actual PM2.5 changes relatively well. A cluster analysis, which is a statistical method that groups similar objects together, was then applied to the hourly PM2.5 concentration for all grids in the model domain. Similarities and differences between objects can be measured in several ways. K-means clustering uses a non-hierarchical cluster analysis method featuring an advantageously low calculation time for the fast processing of large amounts of data. K-means clustering was highly prevalent in existing studies that grouped air quality data according to the same characteristics. As a result of the cluster analysis, PM2.5 pollution in Busan was successfully divided into groups with the same concentration change characteristics. Finally, the redundancy of the monitoring stations and the need for additional sites were analyzed by comparing the clusters of PM2.5 with the locations of the air quality monitoring networks currently in operation.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2017R1D1A3B03036152).
Water for maize for pigs for pork: an analysis of inter-provincial trade in China
Authors: Zhuo La , Liu Yilin , Yang Hong , Hoekstra Arjen Y , Liu Wenfeng , Cao Xinchun , Wang Mengru , Wu Pute
Published: March 2020

Trade in commodities implies trade in virtual water (VW), which refers to the water that was used to produce the traded goods. Various studies have quantified international or inter-provincial virtual water (VW) flows related to the trade in crops and animal products. Until date, however, no effort has been undertaken to understand how the water embodied in traded feed crops (trade stage TS1) will be transferred further because of trade in animal products (trade stage TS2). This is the first study showing this mechanism, in a case study in China for maize (the major pig feed) and pork (the dominant meat), considering the period 2000-2013. We estimate the annual green and blue water footprints in maize production and then quantify the inter-provincial VW flows related to trade in maize (TS1) and trade in maize embodied in pork (TS2). Results show that in TS1, maize-related VW flowed from the water-scarce North to the water-rich South, with an increase of 40% over the study period (from 43 to 61 billion m3 y-1). In TS2, about 10% of the water embodied in maize exports from North to South China returns in the form of pork, with an increase in the absolute amount of 25% (from 4.8 to 6.1 billion m3 y-1). Considering blue VW flows specifically, we find that North-to-South blue VW flows decreased by 5% in TS1, while South-to-North blue VW flows increased by 23% in TS2.

 

References:

Zhuo, L. et al. (2019) Water for maize for pigs for pork: An analysis of inter-provincial trade in China. Water Research 166, 115074, doi:https://doi.org/10.1016/j.watres.2019.115074.

 
A nonlinear Schrödinger equation for gravity waves slowly modulated by linear shear flow
Authors: Li Shaofeng , Chen Juan , Cao Anzhou , Song Jinbao
Published: March 2020

Assume that a fluid is inviscid, incompressible, and irrotational. A nonlinear Schrödinger equation (NLSE) describing the evolution of gravity waves in finite water depth is derived using the multiple scale analysis method. The gravity waves are influenced by a linear shear flow, which is composed of a uniform flow and a shear flow with constant vorticity. The modulational instability (MI) of the NLSE was analyzed in this paper, and the region of MI for gravity waves (the necessary condition for the existence of freak waves) was identified. In this paper, the uniform background flows along or against wave propagation are referred to as down-flow and up-flow, respectively. Uniform up-flow enhances the MI, whereas uniform down-flow reduces it. Positive vorticity enhances the MI, while negative vorticity reduces it. Hence, the influence of positive (negative) vorticity on MI can be balanced out by that of uniform down- (up-)flow. Furthermore, the Peregrine breather (PB) solution of the NLSE is applied to freak waves. Uniform up-flow increases the steepness of free surface elevation, while uniform down-flow decreases it. Positive vorticity increases the steepness of free surface elevation, whereas negative vorticity decreases it.
Spatiotemporal changes to low flow and catchment storage following a step change rainfall decline in Southwest Western Australia
Authors: Smettem Keith , Liu Ning , Harper Richard , Ruprecht John
Published: March 2020

Understanding how summer low flows in a Mediterranean climate are inﬂuenced by climate and land use is critical for managing both water resources and in-stream ecohydrological health. The Eucalyptus forest ecosystems of southwestern Australia are experiencing a drying and warming climate, with a regional step decline in rainfall in the mid-1970s.  Reductions in catchment water storage may be exacerbated by the deep rooting habit of key overstorey species (>30 m has been reported), which can buffer against drought during dry years. Root exploitation of deep soil moisture reserves and/or groundwater can accelerate the long term decline in summer low ﬂows, with a trend towards more ephemeral ﬂow regimes. In contrast, conversion of forests to agricultural land in some catchments can lead to counter-trends of increased low flows due to a rise in groundwater pressure.  These are invariably associated with an increase in stream salinity as regolith stores of salt are mobilized. There has also been extennsive reforestation of farmland in some catchments. 

In this study we perform a detailed analysis of changes to annual summer seven day low flow trends in perennial catchments and flow duration curves in ephemeral catchments across 39 catchments in south-western Australia that have long term records of runoff, rainfall and land cover.  Results showed that 15% of catchments exhibited increased low flows and 85% decreased flows or decreased flow days since the 1970s.  Significant downward step changes in low flows were observed in 17 catchments (44%). The earliest downward step changes occurred in three catchments between 1981-82 (a lag of one decade after the rainfall decline), with the most recent step changes for five catchments occurring in 2001-2004 (three decades after rainfall decline).  Eleven catchments were already ephemeral in the 1970s, but exhibited continued declines in the number of annual flow days over subsequent decades.  Step changes occur when groundwater becomes disconnected or reconnected to the stream invert, with disconnection associated with rainfall decline and vegetative water use.  

The statistical methods we used in this study can be applied to any catchment in order to aid land and water managers assess the impact of climate change and land cover manipulation on low flow response.
Studying the spatial and seasonal variability of greenhouse gases across West Siberia: large-scale mobile measurement campaigns of 2018-2019
Authors: Arshinov Mikhail , Belan Boris , Davydov Denis , Kozlov Artem , Fofonov Alexander , Arshinova Victoria
Published: March 2020

The continuous ground-based measurements of greenhouse gases carried out in Siberia in the past two decades allowed the long-term trends, as well as the diurnal and seasonal cycles of CO2 and CH4 to be derived for this poorly studied region (Belikov et al., 2019). To date, these in-situ observations are made at the joint Japan-Russia Siberian Tall Tower Inland Observation Network (JR-STATION) consisted of 6 automated stations that should be maintained several times per year. In late October to early November 2018, we have undertaken the first mobile campaign to derive a distribution of CO2 and CH4 concentrations at high spatial resolution while traveling to the sites of the above network. For that, we used a commercially available GHG CRDS analyzer (G4301, Picarro Inc., Santa Clara, CA, USA) installed in an off-road vehicle (Arshinov et al., 2019). Over one trip, the instrument were driven over 7000 km throughout the study area.

In March, June, August, and October 2019 we have performed four more campaigns along the same route. This enabled the seasonal pattern of CO2 and CH4 concentrations to be obtained over a huge area of West Siberia between 54.5° and 63.2° north latitude and between 62.3° and 85.0° east longitude, as well as to reveal a large- and small-scale spatial heterogeneity in CH4 mixing ratios particularly over wetland regions. We plan to continue mobile campaigns to cover interannual variations.

 

This work was supported by the Ministry of Science and Higher Education of the Russian Federation under State Contract No. 14.616.21.0104 (ID No RFMEFI61618X0104).

Belikov, D.; Arshinov, M.; Belan, B.; Davydov, D.; Fofonov, A.; Sasakawa, M.; Machida, T. Analysis of the Diurnal, Weekly, and Seasonal Cycles and Annual Trends in Atmospheric CO2 and CH4 at Tower Network in Siberia from 2005 to 2016. Atmosphere 2019, 10, 689.

Arshinov, M.Yu.; Belan B.D.; Davydov D.K.;  Kozlov A.V., Fofonov A.V., and  Arshinova V. Heterogeneity of the spatial distribution of CO2 and CH4 concentrations in the atmospheric surface layer over West Siberia: October-November 2018, Proc. SPIE 11208, 25th International Symposium on Atmospheric and Ocean Optics: Atmospheric Physics, 1120831 (18 December 2019);https://doi.org/10.1117/12.2539205
Fast acquisition of focal mechanism based on statistical analysis
Authors: Monterrubio-Velasco Marisol , Carrasco-Jimenez José Carlos , Rojas Otilio , Rodríguez Juan Esteban , de la Puente Josep
Published: March 2020

Earthquake and tsunami early warning systems and post-event urgent computing simulations require of fast and accurate quantification of earthquake parameters such as magnitude, location and Focal Mechanism (FM). Methodologies to estimate earthquake location and magnitude are well-established and in place. However, automatic solutions of FMs are not always provided by operational institutions and are, in some cases, available only after a time-consuming inversion of the wave-forms needed to determine the moment tensor components. This precludes urgent seismic simulations, which aim at providing ground shaking maps with severe time constraints. We propose a new strategy for fast (<60 s) determination of FM based on historical data sets, tested it at five different active seismic regions, Japan, New Zealand, California, Iceland, and Italy. The methodology includes the k-nearest neighbor's algorithm in a spatial dimension domain to search the most similar FMs between the data set. In our research, we focus on moderate to large earthquakes. The comparison algorithm includes the four closest events, and also a hypothetical event building by the median values of strike, dip, and rake of the k-neighbors. The validation stage includes the minimum rotated angle measure to compute the similitude between a pair of FMs. We find three model parameters, such as the minimum number of neighbors, the threshold radius that defines the neighboring sphere, and the magnitude threshold, that could improve the statistical similitude results. Our fast methodology has a 75%-90% agreement with traditional inversion mechanisms, depending on the particular tectonic region and dataset size. Our work is a key component of an urgent computing workflow, where the FM information will be used as input for ground motion simulations. Future work will assess the sensitivity of FM uncertainty in the resulting ground-shaking maps.
Polarimetric Radar Signatures and Performance of Various Radar Rainfall Estimators during an Extreme Precipitation Event over the Thousand-Island Lake Area in Eastern China
Authors: Gou Yabin , Chen Haonan , Zhou Juan
Published: March 2020

Polarimetric radar provides more choices and advantages for quantitative precipitation estimation (QPE). Utilizing the C-band polarimetric (CPOL) radar in Hangzhou, China, six radar QPE estimators based on the horizontal reflectivity (ZH), the specific attenuation (AH), the specific differential phase (KDP), and their corresponding double-parameters that further integrate the differential reflectivity (ZDR), namely R(ZH, ZDR), R(KDP, ZDR) and R(AH, ZDR), are investigated for an extreme precipitation event occurred in Eastern China on 1 June 2016. These radar QPE estimators are respectively evaluated and compared with a local rain gauge network and drop size distribution (DSD) data observed by two disdrometers. The results show that (i) Each radar QPE estimator has its own advantages and disadvantages depending on the specific rainfall patterns, and it can outperform other estimators at a certain period of time; (ii) although R(AH, ZDR) underestimates in the light rain pattern, it performs best of all radar QPE estimators according to statistical scores; (iii) Both the optimal radar rainfall relationship and the consistency between radar measurements aloft and surface observations are required to obtain accurate rainfall estimates close to the ground. The contamination of melting solid hydrometeors on AH and/or KDP may make them less effective than ZH. In addition, appropriate α coefficient can eliminate the melting impact on the AH-based rainfall estimator.
Response of Orographic Precipitation to Subsaturated Low-Level Layers
Authors: Fu Shizuo , Rotunno Richard , Xue Huiwen
Published: March 2020

Orographic precipitation is, on the one hand, an important source of fresh water, and on the other hand, a potential cause of floods and other disasters. Previous studies have focused on the situation where the whole atmosphere is saturated and nearly moist-neutral. However, there are times when subsaturated low-level layers are observed to be below saturated, nearly moist-neutral, upper-level layers.

A series of idealized two-dimensional simulations are performed here to investigate the impact of this subsaturated low-level layer on orographic precipitation. It is found that the impact is mainly controlled by a nondimensional parameter and two competing effects. The nondimensional parameter is N2zt/U, where N2 and zt are, respectively, the dry Brunt–Väisälä frequency and depth of the subsaturated low-level layer, and U the cross-mountain wind speed. When the nondimensional parameter exceeds a critical value, the decelerated region on the upwind side of the mountain moves upwind, resulting in weak surface precipitation near the mountain peak. When it is smaller than the critical value, surface precipitation occurs near the mountain peak.

The two competing effects are: 1) the vapor-transport effect, meaning that increasing zt decreases the amount of vapor transported to the mountain, and hence tends to decrease surface precipitation; and 2) the updraft width effect, meaning that increasing zt enhances flow blocking, producing a wider updraft over the upwind slope, and hence tends to increase surface precipitation. When the vapor-transport effect dominates, surface precipitation decreases with zt. When the updraft-width effect dominates, surface precipitation increases with zt.
Effects of Rainfall and Vegetation Conditions on Colloid Transport in Saturated Vegetative Filter Strips
Authors: Yu Congrong , Sun Yufeng
Published: March 2020

Non-point source pollution has become the main pollution source of surface water , among which colloidal pollutants are a kind of important non-point source pollutants. Rainfall runoff is the main factor that causes non-point source pollutants to migrate to water. Vegetative filter strips is an effective measure to control non-point source pollution. Vegetative density is one of the important factors affecting pollutant removal efficiency. In order to clarify the removal efficiency of colloidal non-point source pollutants by vegetative filter strips with different densities under rainfall conditions, it is necessary to study the effects of vegetative density and rainfall intensity on the migration and removal mechanism of colloids in vegetative filter strips. Based on the numerical model established by coupling non-Darcy flow water balance equation and colloid transport equation, combined with laboratory experiments and numerical simulation, the removal mechanism of colloid at different migration distances was studied under the conditions of fixed inflow, different rainfall intensity and vegetative density.

The results show that: 1) Although there is no infiltration, the colloid diffuses from surface water into saturated sand, which increases the removal efficiency of colloid. 2) Increasing vegetative density will increase the removal efficiency of colloids in vegetative filter strips. With the increase of density, the velocity of flow decreases, which decreases the deposition capacity of colloids on vegetative and increases the diffusion of colloids from surface water to soil. 3) Under rainfall conditions, the presence of rainfall increases the removal efficiency of colloids by vegetative filter strips. Although rainfall weakens the ability of vegetative to deposit colloids, it enhances the ability of colloids to diffuse to soil. The deposition capacity of colloids on vegetative increased with the increase of rainfall intensity. 4) The interception ability of vegetative enhances the diffusion ability of colloids to soil, and enhances the removal efficiency of colloids by vegetative. 5) In the vegetative filter strips, the adsorption coefficient of colloids decreases with the migration distance, mainly due to the heterogeneity of colloids. In the process of colloid migration, the absolute value of surface potential and the colloid with smaller particle size along the course are easy to be removed by vegetative filter strips because of the smaller barrier between colloid and plant, the smaller second energy potential well and the strong adsorption capacity of colloid deposition.

The research results provide important theoretical basis and reference for designing vegetative filter strips to remove colloidal non-point source pollutants under rainfall conditions.
Automated mapping of Antarctic supraglacial lakes and streams using machine learning
Authors: Dirscherl Mariel , Dietz Andreas , Baumhoer Celia , Kneisel Christof , Kuenzer Claudia
Published: March 2020

Antarctica stores ~91 % of the global ice mass making it the biggest potential contributor to global sea-level-rise. With increased surface air temperatures during austral summer as well as in consequence of global climate change, the ice sheet is subject to surface melting resulting in the formation of supraglacial lakes in local surface depressions. Supraglacial meltwater features may impact Antarctic ice dynamics and mass balance through three main processes. First of all, it may cause enhanced ice thinning thus a potentially negative Antarctic Surface Mass Balance (SMB). Second, the temporary injection of meltwater to the glacier bed may cause transient ice speed accelerations and increased ice discharge. The last mechanism involves a process called hydrofracturing i.e. meltwater-induced ice shelf collapse caused by the downward propagation of surface meltwater into crevasses or fractures, as observed along large coastal sections of the northern Antarctic Peninsula. Despite the known impact of supraglacial meltwater features on ice dynamics and mass balance, the Antarctic surface hydrological network remains largely understudied with an automated method for supraglacial lake and stream detection still missing. Spaceborne remote sensing and data of the Sentinel missions in particular provide an excellent basis for the monitoring of the Antarctic surface hydrological network at unprecedented spatial and temporal coverage.

In this study, we employ state-of-the-art machine learning for automated supraglacial lake and stream mapping on basis of optical Sentinel-2 satellite data. With more detail, we use a total of 72 Sentinel-2 acquisitions distributed across the Antarctic Ice Sheet together with topographic information to train and test the selected machine learning algorithm. In general, our machine learning workflow is designed to discriminate between surface water, ice/snow, rock and shadow being further supported by several automated post-processing steps. In order to ensure the algorithm’s transferability in space and time, the acquisitions used for training the machine learning model are chosen to cover the full circle of the 2019 melt season and the data selected for testing the algorithm span the 2017 and 2018 melt seasons. Supraglacial lake predictions are presented for several regions of interest on the East and West Antarctic Ice Sheet as well as along the Antarctic Peninsula and are validated against randomly sampled points in the underlying Sentinel-2 RGB images. To highlight the performance of our model, we specifically focus on the example of the Amery Ice Shelf in East Antarctica, where we applied our algorithm on Sentinel-2 data in order to present the temporal evolution of maximum lake extent during three consecutive melt seasons (2017, 2018 and 2019).
Global Monitoring and Characterization of Infrasound Signatures by Large Fireballs
Authors: Pilger Christoph , Gaebler Peter , Hupe Patrick , Ott Theresa , Drolshagen Esther
Published: March 2020

Large meteoroids can be registered in infrasound recordings during their entry into the Earth’s atmosphere. A comprehensive study of 10 large fireball events of the years 2018 and 2019 highlights their detection and characterization using global infrasound arrays of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The study focuses on the observation and event analysis of the fireballs to estimate their respective location, yield, trajectory, and entry behavior. Signal characteristics are derived by applying the Progressive Multi-Channel Correlation method as an array technique. The comparison of the events with a NASA reference database as well as the application of atmospheric propagation modeling allows to draw conclusions about infrasound-based detection capability, localization accuracy, yield estimation, and source characterization. The infrasound technique provides a time- and location-independent remote monitoring opportunity of impacting near-Earth objects (NEOs), either independent or complementary to other fireball observation methods. Additionally, insights about the detection and localization capability of IMS infrasound stations can be gained from using large fireballs as reference events, being of importance for the continuous monitoring and verification of atmospheric explosions in a CTBT context.
K-cymrite as Redox Insensitive Transporter of Nitrogen in the Mantle
Authors: Sokol Alexander , Kupriyanov Igor , Seryotkin Yurii , Sokol Ella
Published: March 2020

The current flux of nitrogen into the mantle in subduction zones is about three times its amount outgassing at mid-ocean ridges, arc and intraplate volcanoes, i.e., some efficient nitrogen hosts and carriers should exist in slabs. The K+ → (NH4+) substitution in silicate minerals is possible only within limited redox-favorable parts of slabs. Whether nitrogen can be transported and immobilized in the mantle as part of solids by some redox-independent mechanisms? The experimental study of the muscovite-NH3-N2-H2O and eclogite+muscovite-NH3-N2-H2O systems at 6.3-7.8 GPa and 1000 to 1200°C shows that NH3- and N2-rich K-cymrite can be stable in metapelite and act as a redox insensitive carrier of nitrogen to mantle depths >200 km in downgoing slabs. This ability is related to its unique clathrate structure that can accommodate three species of nitrogen: N2 and NH3 molecules in cages and (NH4)+ substituting for K+, while imprisoned N2 and NH3 were first discovered in cages of ultra-high pressure minerals. The storage capacity K-cymrite with respect to nitrogen increases from 2.9 to 6.3 wt.% with increase of fO2 from ~IW to ~NNO, at the N2/(NH3+N2) ratio in fluid from 0.1 to 0.9. Comparison of equilibrated muscovite and K-cymrite synthesized at 7.8 GPa, 1070°C, and fO2 ~IW demonstrates that the clathrate mechanism of nitrogen entrapment by aluminosilicates (in the form of N2 and NH3 molecules) is much more efficient than the K+ ® (NH4+) substitution even in strongly reduced conditions. The presence of an N-bearing fluid in the studied systems stabilizes the K-cymrite structure. Muscovite does not convert to K-cymrite in the absence of NH3-N2-bearing fluid within 7.8 GPa and 1070-1120°C. Our estimates of normalized volume per non-hydrogen atom show that N2-bearing cymrite is the densest in the series of K-cymrite with cages filled to different degrees: K-CymNH3 > K-CymH2O > K-CymN2 and is thus the most stable among cymrite-type compounds under high pressure.

The research was performed by a grant of the Russian Science Foundation (16-17-10041).