bluuebunny/crossref_metadata_2025 huggingface dataset:
The Isua (Greenland) relict stromatolites cannot be confidently interpreted as original sedimentary structures
Authors: Zawaski Mike , Kelley Nigel , Orlandini Phil (Omero) , Nichols Claire , Allwood Abigail , Mojzsis stephen
Published: March 2021

The biogenicity of proposed stromatolite structures from Eoarchean (ca. 3.71 Ga) rocks of the Isua Supracrustal Belt (ISB) in West Greenland is under debate. Our 2020 publication argues against biogenicity for the proposed stromatolites. The subsequent Comment to our work challenged some of our fundamental arguments for a tectonic origin to the structures. This Comment has been an opportunity for us to elaborate on these structures and further refine and solidify our initial conclusion that they represent the expected outcome of the tectonic deformation displayed in the ISB. This dialogue between groups is essential as the consequence of these structures being biogenic would move the date for complex microbial communities 200 million years closer to Earth's formation, to a time when Earth’s surface would have been even less habitable. Here we reexamine our four key observations that support our tectonic origin. First, we report detailed field characterization and structural analysis to show that the structures are linear inverted ridges aligned with azimuths of local and regional fold axes and parallel to linear structures; they were never primary linear, deformation-parallel stromatolites or deformed conical stromatolites. Second, our combined major element (e.g., Ca, Mg, Si) scanning μXRF maps fail to reveal internal laminations for the cores of these structures, but other authors argue layers are present. In the instance where layers appear to be preserved, we argue that an amorphous core is still present.  Also, layering on its own is inconclusive of a biogenic origin as relict internal laminations could be preserved. Third, the gross morphology of these structures being nearly identical in morphology and dimensions to clearly tectonic structures only tens of meters away is a more reliable indicator of a tectonic versus biogenic origin than internal laminations. Lastly, discontinuous field relationships and absence of primary sedimentary structures that could serve as way-up indicators preclude confident assignment of these outcrops as being structurally overturned, as originally argued. Collectively, our results reinforce that the Isua structures are the expected result of a tectonic fabric that preserves no fine-scale primary sedimentary structures and were probably never stromatolites.
Spatial prediction of soil parameters after wildfire and their relationship with ecological process of soil and vegetation
Authors: Banda Carrasco David , Tolorza Violeta , Galleguillos Mauricio
Published: March 2021

Novel estimations of burn severity consequences are relevant to improve the understanding of spatial ecosystem dynamics between soil and vegetation. In this study, we implemented digital soil mapping (DSM) with Random Forest (RF) and generalized additive model (GAM) as internal statistical models, to generate maps for spatial prediction of chemical parameters of post-fire litter (N, P, C and OM) in the Purapel River basin, Maule region of Chile. Response variables were the chemical characterization of 67 samples of litter collected in different hillslopes of the basin during the first post-fire winter. The predictive variables that fed the RF model were spectral, topographic, and vegetation structure derivations, obtained from free and private use satellite products (Sentinel 1, Sentinel 2, LiDAR and TanDEM-X). As a result, we generated maps of post-fire spatial distribution of N, P, C and OM with acceptable adjustment (R2 0.52-0.61, nRMSE 54-72, pbias 0.35-1.20). The uncertainty associated with the predictions of these variables was successfully evaluated with the prediction interval coverage probability (PICP). A clear decrease on the concentration of litter elements is observed respect to the degree of burn severity, and this relationship depends on the type of cover and the environmental gradient where they are distributed.
Application of a Spatially Explicit Scaling Factor Method on CO2 Emissions From New York
Authors: Hajny Kristian , Floerchinger Cody , Pitt Joseph , Lopez-Coto Israel , Tomlin Jay , Kaeser Robert , Stirm Brian , Jayarathne Thilina , Gately Conor , Sargent Maryann , Gurney Kevin , Roest Geoffrey , Turner Alexander , Hutyra Lucy , Shepson Paul , Wofsy Steven
Published: March 2021

Assessing progress towards greenhouse gas mitigation targets in recent legislation requires reliable, precise methods for emissions quantification.  Top-down approaches can provide a complementary assessment to the bottom-up inventories typically used by cities.

In this work we have performed a series of 9 winter aircraft measurement flights downwind of New York City in 2018 – 2020.  We use dispersion modeling driven by publicly available meteorological products to calculate footprints relevant to the flight data.  To calculate modeled emissions, we combine these footprints with four CO2 inventories (ODIAC, EDGAR, ACES, and Vulcan) using a spatially explicit scaling factor approach.  We show that we can isolate the emissions from two areas of interest, New York City and the New York-Newark urban area, by using the fraction of modeled enhancements originating in said areas of interest as weighting functions.  We then calculate a scaling factor that optimizes agreement with measurements for each flight.  Here we discuss this technique and the posterior emissions for both areas of interest as compared to inversion analyses for the same areas.  We also quantify the variability across the ensemble including multiple meteorological products, scaling factor calculation methods, and mixing parameterizations across all inventories and flight days.
GPM DPR Profile Classification Algorithm: Enhancement from V6X to V7
Authors: Chandra Chandrasekar V , Le Minda
Published: March 2021

The profile classification module in GPM DPR level-2 algorithm outputs various products  such as rain type classification, melting layer  detection and  identification of  surface snowfall , as well as presence of graupel and hail. Extensive evaluation and validation activities have been performed on these products and have illustrated excellent performance. The latest version of these products is 6X.  With increasing interests  on severe weather  such as hail and  extreme precipitation, in  the next version (version 7), we development a flag to identify hail along the vertical profile using  precipitation type index (PTI).

Precipitation type index (PTI) plays an important role in a couple of algorithms in the profile classification module. PTI is a value calculated for each dual-frequency profile with precipitation observed by GPM DPR.   DFRm slope, the maximum value of the Zm(Ku) , and  storm top height  are used in calculating PTI. PTI is effective in separating snow and Graupel/Hail  profiles. In version 7, we zoom in further into PTI for  Graupel/ hail profiles and separate  them into graupel and hail profiles with different PTI thresholds. A new Boolean product of “flagHail” is a hail only identifier for each vertical profile.  This hail product will be validated with ground radar products and other DPR products from Trigger module of DPR level-2 algorithm.   In version 7, we make improvements of the surface snowfall algorithm. An adjustment is made accounting for global variability of storm top profiles.. A storm top normalization is introduced to obtain a smooth transition of surface snowfall identification algorithm along varying latitudes globally.
Topotaxial intergrowth and origin of antiperthite in monzogranite 
Authors: Song Yueting , Zhao Shanrong
Published: March 2021

The crystallographic orientation of antiperthite (squared alkali feldspar inclusions grow inside plagioclase host) in Tiantangzai monzogranite from Dabie Mountain was investigated. The morphology of alkali feldspar inclusions is hexahedron, three pairs of parallel faces are controlled by the (010), (001) and (110) planes of the host plagioclase, respectively. Some plagioclase develops albite polysynthetic twin, defined the twinned individuals as Pl(1) and Pl(2), respectively; some alkali feldspar inclusions are related by Carlsbad twin, the twinned individuals are also defined as Kfs(1) and Kfs(2), respectively. Pl(1) is oriented similarly to Kfs(1). The topotaxial relationship between Pl(2) and Kfs(1) is similar to albite-twin. The topotaxial relationship between Kfs(2) and Pl(1) is similar to Carlsbad-twin. Kfs(2) and Pl(2) would form a topotaxial relationship similar to Carlsbad-albite-twin. Pl(1) generally becomes thinner or disappears in the regions where alkali feldspar inclusions developed. The development sequence of the alkali feldspar inclusions and the polysynthetic albite twin needs to be further investigated. Electron microprobe line scanning shows a homogeneous K, Ca and Na distribution in a single plagioclase grain with inclusions developed, suggesting that the origin of alkali feldspar inclusion may not be related to exsolution. The fractures in the host plagioclase are well developed, but most fractures do not pass through the embedded alkali feldspar. The precipitated alkali feldspar may be a result of alkali-bearing fluids penetrating through fractures and replacing plagioclase. The rim of some larger anhedral alkali feldspar inclusions has many voids, the local average misorientation map indicates there is a rectangular area with low misorientation difference inside the anhedral inclusions. The anhedral alkali feldspar inclusions are presumed to form by secondary replacement on top of the original rectangular inclusions.
Ancient Ice Buried Below a Meter of Regolith; Ong Valley, Antarctica
Authors: Bergelin Marie , Putkonen Jaakko , Balco Greg , Morgan Dan , Matheney Ronald K. , Corbett Lee B.
Published: March 2021

We have discovered and cored a massive ice mass buried underneath a meter of glacial debris in Ong Valley, Antarctica, which we report here to consist of two stacked ice bodies dated at >2 Ma. Glacial ice is known to be a great archive of atmospheric gasses, chemical compounds, and airborne particles. An ice mass of such antiquity, as reported here, may reveal information about our past which is otherwise unknown.

We determine the age of the ice directly by dating the dirt suspended within the ice and by dating the till layer covering the ice using cosmogenic nuclide: 10Be, 26Al, and 21Ne. These cosmogenic nuclides are produced by cosmic-ray interactions with minerals near the Earth’s surface, and in this case in suspended dirt embedded in the ice. As the production rate of cosmogenic nuclides decreases rapidly with increasing depth below the Earth’s surface, the cosmogenic nuclide concentration profile yields information about the exposure history and further aid to constrain geological processes such as sublimation rates, and surface erosion rates. We further compare the cosmogenic nuclide model results with mapped glacial moraines adjacent to the current ice, and stable water isotope analysis throughout the core in order to explore the unique history that these two stacked ice masses have.

We find the uppermost section of this buried ice mass to be >2 Ma old. Large variation of cosmogenic nuclide concentrations downcore and stable water isotopes, suggests that the deepest section of the ice core may belong to a separate, older ice mass that has previously been exposed at the surface. Lateral moraines and measurements of cosmogenic nuclides in glacial debris further up valley suggest that this deeper, older ice may be >2.6 Ma old, and was most likely buried during glacial advancement into Ong Valley < 4 Ma ago.
Scaling of magnetic reconnection with a limited x-line extent
Authors: Huang Kai , Liu Yi-Hsin , Lu Quanming , Hesse Michael
Published: March 2021

Magnetic reconnection is a fundamental physical process that is responsible for releasing the magnetic energy during substorms of planetary magnetotails. Previous studies of magnetic reconnection usually take the two-dimensional (2D) approach, which assumes that reconnection is uniform in the 3rd direction out of the 2D reconnection plane. However, observations suggest that reconnection can be limited in the 3rd direction, such as reconnection at Mercury's magnetotail. It turns out that reconnection can be suppressed when reconnection region is very limited in the 3rd direction. An internal x-line asymmetry along the current direction develops because of the transport of reconnected magnetic flux by electrons beneath the ion kinetic scale, resulting in a suppression region identified in Liu et al., 2019. Under the guidance of a series of 3D kinetic simulations, in this work, we incorporate the length-scale of this suppression region ~10di to quantitatively model the reduction of the reconnection rate and the maximum outflow speed observed in the short x-line limit. The average reconnection rate drops because of the limited active region (where the current sheet thins down to the electron inertial scale) within an x-line. The outflow speed reduction correlates with the decrease of the J×B force, that can be modeled by the phase shift between the J and B profiles, also as a consequence of the flux transport. Notably, these two quantities are most essential in defining the well-being of magnetic reconnection, which can tell us when reconnection shall be suppressed.
Multi-hazard mitigation challenges during the Covid-19 crisis? Evidence from the tropical regions
Authors: Pal Indrajit , Udmale Parameshwar , Szabo Sylvia , Pramanik Malay , Ganni Satya Venkata Sai Aditya Bharawaz
Published: March 2021

Across the world, health and disaster managers face the challenge of responding to natural hazards such as cyclones, floods, and droughts while minimizing the impacts of Covid-19. The tropical cyclones and floods affect vulnerable communities and result in losses of life and damages. The drought situations can weaken the agricultural economy and local livelihoods. How these impacts could be amplified by the Covid-19, mainly during the monsoon season, is of great importance for informed-planning. The present study aims to assess exposure to hydro-meteorological hazards (tropical cyclones, floods, and droughts) in terms of the number of people affected, economic activities exposed, and how these hazards superimposed over the Covid-19 pandemic could impact the different phases of disaster risk management cycle. The study focuses on three deltas, namely, Ganges-Brahmaputra-Meghna (GBM) delta spanning over India and Bangladesh, and Red River (RR) and Mekong River (MK) deltas in Vietnam.

Present research found that the GBM delta suffers from frequent cyclones and floods and less with coastal floods and droughts, whereas the MK delta suffers from riverine and coastal floods and droughts. The RR delta faces frequent tropical cyclones, riverine and coastal floods, and droughts. Populations living in Red delta (100%) exposed more to tropical cyclone as compared to GBM (2.22%) and the Mekong delta (0%) with 50-year return period (RP). Similarly, about 36.46 (0.28), 83.24 (47.23), and 72.76 (33.49) % population of the GBM, RR, and MK deltas are exposed to riverine (coastal) flood hazards with 10-year RP, respectively. During May-Aug 2020, a maximum of 0.76, 100, and 33.49 % population in a month was exposed to meteorological drought (SPI3 below -1) in the GBM, RR, and MK deltas, respectively.

The results include probabilistic exposure of urban area, cropland, livestock, and GDP to major hydro-meteorological hazards on a similar line. In the second part, the study explores the number of Covid-19 cases reported at the administrative level 2 and draws qualitative inferences on how tackling multi-hazards in the deltas could have become more challenging during the ongoing pandemic and vice versa.  The study recommends that the pandemic has resulted in an urgent need to incorporate health emergency disasters while designing hydro-meteorological disaster management plans.
Simulation of postfrontal heavy snowfall over the Australian Snowy Mountains 
Authors: Gevorgyan Artur , Ackermann Luis , Huang Yi , Siems Steven , Manton Michael
Published: March 2021

Heavy snowfall associated with the passage of a cold front was observed over the Australian Snowy Mountains (ASM) from 05 to 07 Aug, 2018, producing more than 60 mm of snow at some mountain gauges. The snowfall was mainly observed after the passage of the cold front (in postfrontal period) when north-westerly and westerly cross-barrier winds were observed in the lower and mid troposphere. According to the observations of Cabramurra parsivel located at windward slopes of northern part of the ASM snow intensities exceeded 20 mm h-1 during short time episodes. Furthermore, Himawari-8 observations show convective clouds over the ASM with isolated cold cloud top temperatures varying from -45 to -40 oC. The Weather Research and Forecasting (WRF) model version 4.2 was used to further investigate this event. The WRF model was run at 1 km spatial resolution using Thompson, Morrison, NSSL and WDM7 microphysical schemes. Overall, Thompson scheme (our CONTROL run) successfully simulated the precipitation and cloud pattern over the ASM, but showing underestimation of upwind and near top precipitation amount. Morrison and NSSL schemes produce more snow over highly elevated parts of the ASM leading to overestimation of observed snow at top and leeward gauges. The WDM7 simulates unrealistically high amount of precipitation over entire ASM due to strong glaciation processes produced by this scheme. The evaluation of simulated water vapor and cloud water paths against radiometer observations at Cabramurra location show that all sensitivity runs consistently underestimate water vapor path (WVP) despite strong relationship in the simulated and observed WVP time-variations throughout the event. The underestimation of supercooled liquid water (SLW) path is strongest in the WDM7 scheme, while the overestimation of SLW content is greatest in the Thompson scheme. 
Evaluation of tropospheric ozone residual measurements derived from TOMS-V9 and hyper-spectral total ozone algorithms
Authors: Ziemke Jerry , Kramarova Natalya , Haffner Dave , Bhartia Pawan
Published: March 2021

The NASA TOMS V9 (TOMS-V9) total ozone retrieval algorithm is tested
for sensitvity to boundary-layer ozone and suitability to make daily
maps of tropospheric ozone residual (TOR).  Daily maps of TOR are
derived by differencing co-located MERRA-2 assimilated MLS
stratospheric column ozone (SCO) from total column ozone from the Aura
Ozone Monitoring Instrument (OMI).  The TOMS-V9 algorithm uses a few
discrete channels with an order of magnitude range in ozone
senstivity. We compare the TOR results from TOMS-V9 with results from
several hyper-spectral total ozone retrievals: GODFIT v4 (BIRA-IASB),
OMI-DOAS (KNMI), and total ozone from the SAO PROFOZ algorithm. We
compare all satellite-retrieved TOR with TOR derived from ozonesondes,
lidar, and the Goddard Modeling Initiative (GMI) model simulation.

 

 
On the difference of aerosol hygroscopicity between high and low RH environment in the North China Plain
Authors: Shi Jingnan , Hong Juan , Ma Nan , Luo Qingwei , Xu Hanbing , Tan Haobo , He Yao , wang Qiaoqiao , Tao Jiangchuan , Zhou Yaqing , Peng Long , Cheng Yafang , Su Hang , Sun Yele
Published: March 2021

Simultaneous measurements of aerosol hygroscopicity and chemical composition were performed at a suburban site in the North China Plain in winter 2018 using a self-assembled hygroscopic tandem differential mobility analyzer (H-TDMA) and a capture-vaporizer time-of-flight aerosol chemical speciation monitor (CV-ToF-ACSM), respectively. During the experimental period, aerosol particles usually show an external mixture in terms of hygroscopicity, with a less hygroscopic particles mode (LH) and a more hygroscopic mode (MH). The average ensemble mean hygroscopicity parameter (κmean) are 0.16, 0.18, 0.16, and 0.15 for 60, 100, 150, and 200 nm particles, respectively. Two episodes with different RH/T conditions and secondary aerosol formations are distinguished. Higher aerosol hygroscopicity is observed for all measured sizes in the high RH episode (HRH) than in the low RH episode (LRH). In LRH, κ decreases as the particle size increases, which may be explained by the large contribution of non- or less-hygroscopic primary compounds in large particles due to the enhanced domestic heating emissions at low temperature. The number fraction of LH mode at 200 nm even exceeds 50%. Closure analysis is carried out between the HTDMA-measured κ and the ACSM-derived hygroscopicity using different approximations for the hygroscopic parameters of organic compounds (κorg). The results indicate that κorg is less sensitive towards the variation of its oxidation level under HRH conditions but has a stronger O: C-dependency under LRH conditions. The difference in the chemical composition and their corresponding physical properties under different RH/T conditions reflects potentially different formation mechanisms of secondary organic aerosols at those two distinct episodes.
Deep Learning Stream Temperature Model: Recommendations for Modeling Gauged and Ungauged Basins
Authors: Rahmani Farshid , Lawson Kathryn , Oliver Samantha , Appling Alison , Shen Chaopeng
Published: March 2021

Stream water temperature (Ts) is a variable that plays a pivotal role in managing water resources. We used the long short-term memory (LSTM) deep learning architecture to develop a basin centric single Ts model based on general meteorological data and basin meteo-geological attributes. We created a strong tool for long-term Ts projection and subsequently, improved the Ts model using novel approaches. We investigated the impact of both observed and simulated streamflow data on improving the model accuracy. At a national scale, we obtained a median root-mean-square error (RMSE) of 0.69 oC, and Nash-Sutcliffe model efficiency coefficient (NSE) of 0.985, which are marked improvements over previous values reported in previous studies. In order to test the performance of the model on basins ranging from basins with extensive data to unmonitored basins, we used more than 400 basins with different data-availability groups (DAG) across the continent of the United States to explore how to assemble the training dataset for both monitored and unmonitored basins. Best root-mean-square error (RMSE) for sites with extensive (99%), intermediate (60%), scarce (10%) and absent (0%) data for training were 0.75, 0.837, 0.889, and 1.595 oC, respectively. We observed the negative effect of the presence of reservoirs in Ts modeling. Our results illustrated that the most suitable training set should be different in modeling basins with different availability of observed data. for predicting Ts in a monitored basin, including basins that have at least equal DAG with that particular basin will result in most accurate predictions, however, for Ts prediction in ungauged basin, including all basins in training section will generate the best model, showing a more diverse training set. Furthermore, to decrease overfitting produced by attributes for PUB application, we could improve the accuracy of the model using input-selection ensemble method. We got median correlation higher than 0.90 for PUB after seasonality was removed which is still high. While many Ts prediction models showed better performance in summer, our model was on the opposite side. We found a strong relationship between general available daily meteorological variables and catchment attributes with the presented Ts model. However, our results indicate that combining physics-based criteria to the model can improve the prediction of temperature in river networks.

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Constraining past bedrock surface temperatures at the Gorner glacier, Switzerland, using feldspar thermoluminescence for surface paleothermometry. 
Authors: Elkadi Joanne , Biswas Rabiul , King Georgina , Herman Frédéric
Published: March 2021

Our ability to quantify past climate conditions is crucial for predicting future scenarios and landscape evolution. To date, reconstructions of the Earth’s past climate have mostly relied on the use of climate proxies to infer previous surface conditions (e.g. Jones and Mann, 2004 for a review). However, few methods exist that are capable of directly measuring past temperature histories, particularly in terrestrial settings.

The aim of this study is to contribute towards a more detailed understanding of glacial and interglacial temperature fluctuations across the Central and Western Alps, from the Last Glacial Maximum to present day, by constraining past temperatures of exposed bedrock surfaces adjacent to the Gorner glacier in Zermatt, Switzerland. This is done through the recently developed application of feldspar thermoluminescence to surface paleothermometry (Biswas et al., 2018; 2020). The thermoluminescence signal of feldspar, from room temperature to 450°C, is sourced from a continuous distribution of electron traps within the crystal lattice (Biswas et al., 2018). The release of this trapped charge is temperature dependent and thus, at room temperature, results in traps with a range of thermal stabilities with electron residence times ranging from less than a year to several billion years (Aitken 1985). Traps sensitive to typical surface temperature variations (e.g. ∼10°C) have been shown to lie between 200°C and 250°C of the TL glow curve (Biswas et al., 2020). From this temperature range, five thermometers (200°C to 250°C in 10°C intervals) can be used together as a multi-thermometer, and subsequently combined with a Bayesian inversion approach to constrain thermal histories over the last ∼50 kyr (Biswas et al., 2020).

In this study, the preliminary temperature histories of five bedrock samples with independently constrained exposure ages, exposed progressively since the Last Glacial Maximum, will be presented.

References:

Aitken, M.J., 1985. Thermoluminescence Dating. Academic Press, London.

Jones, P.D., Mann, M.E., 2004. Climate over past millennia. Reviews of Geophysics, 42, 2004.

Biswas, R.H., Herman, F., King, G.E., Braun, J., 2018. Thermoluminescence of feldspar as a multi-thermochronometer to constrain the temporal variation of rock exhumation in the recent past. Earth and Planetary Science Letters, 495, 56-68.

Biswas, R.H., Herman, F., King, G.E., Lehmann, B., Singhvi, A.K., 2020. Surface paleothermometry using low temperature thermoluminescence of feldspar. Climate of the Past, 16, 2075-2093.
Scattering of internal tide energy to super-tidal frequencies in global HYCOM 
Authors: Solano Miguel , Buijsman Maarten
Published: March 2021

Energy decay in realistically forced global ocean models has been mostly studied in the diurnal and semi-diurnal tidal bands and it is unclear how much of the tidal energy in these bands is scattered to higher frequencies. Global ocean models and satellite altimetry have shown that low-mode internal tides can propagate thousands of kilometers from their generation sites before being dissipated in the ocean interior but their pathway to dissipation is obscured due to lee-wave breaking at generation, wave-wave interactions, topographic scattering, shearing instabilities and shoaling on continental shelves. Internal tides from some generation sites, such as the Amazon shelf and the Nicobar and Andaman island chain, have large amounts of energy resulting in a steepening of the internal waves into solitary wave trains due to non-hydrostatic dispersion. In HYCOM, a hydrostatic model, this process is partially simulated by numerical dispersion. However, it is yet unknown how the dissipation of internal tides is affected by the numerical dispersion in hydrostatic models. In this study we use the method of vertical modes and rotary spectra to quantify the scattering of internal tides to higher-frequencies and analyze the dissipation processes in global HYCOM simulations with 4-km horizontal resolution.
Non stationary combination for the simulation of time-varying flow rates in closed-loop ground heat exchangers
Authors: Beaudry Gabrielle , Pasquier Philippe , Marcotte Denis
Published: March 2021

Ground source heat pump systems are among the most energy-efficient heating and cooling technologies. Their performance is strongly related to the accuracy of the ground heat exchanger sizing, hence requiring the forecast of the system’s temperature evolution in response to the anticipated thermal loads. Through this process, simulation techniques that make use of the superposition principle are commonly used to reduce the computational burden. In their current state, these techniques are however only suitable for addressing linear and stationary problems and do not apply to fundamental non stationary situations related to ground source heat pumps operation that involve time-variant parameters.

The present work addresses this issue by introducing a novel method based on the principle of superposition that tackles the fast evaluation of the temperature of a closed-loop ground heat exchanger operating with a dynamic heat load as well as time-variant circulation flow rates. The developed method relies on the non stationary combination, a technique borrowed from the field of seismic data processing. This technique achieves discontinuous transitions of convolution products that can be smoothened near transition times by realizing a linear interpolation over the duration of the fluid residence time.

The accuracy and efficiency of the proposed method are verified by comparing its results with those provided by reference 3D finite-elements models developed in the Comsol Multiphysics environment. For this purpose, comparative simulations representing the non stationary operation of a closed-loop system having time-variant circulation flow rates are conducted. The case of a single well is first investigated, followed by a borefield of eight wells to demonstrate the validity of the method in both scenarios.

Findings indicate that the proposed method can reproduce the reference results with a mean absolute error that is lower than 0.02 °C, and that it is faster than the numerical models by several orders of magnitude. These findings suggest that a broader range of operating scenarios can be handled by highly efficient simulation tools based on the superposition principle, which could foster the development of optimal operating strategies and lead to enhanced overall performances of ground source heat pump systems.
Modelling post-fire runoff and erosion processes for emergency assessment of post-fire flood hazards 
Authors: Pradhan Nawa Raj , Floyd Ian , Berli Markus , Pak Jang , Price Mitchell , Turnbull Stephen , Hobbs Brandon , Aguilera Francisca Olmos de , Shillito Rose , Giovando Jeremy
Published: March 2021

Land use change, as well as changes in the soil physical and chemical properties impact the runoff and erosion generation processes, and overall transport mechanism. Therefore, research and development of a watershed’s physics-based distributed runoff and erosion processes is needed to better predict discharge and erosion under different environments. This is important   for not only local floods and droughts and, geomorphological and landform changes point of view but also for a better understanding of the hydrology, erosion and land surface processes and its impact on ecosystem, transport system, environment and socio-economy and safety. One of the natural and/or manmade causes that brings about changes in land use and soil property is wildfires. In an effort to represent the physics of the watershed under post-fire conditions, this study presents a  detailed analysis of runoff and erosion generation processes, by including soil hydrophobicity and burn severity related soil hydraulic properties changes,  and transport responses, under sediment laden fluid flow conditions, in watersheds under burn conditions.  This study also conducted distributed hydro-geomorphological parameter value identification process for enabling engineers and hydrologists to provide critical post-fire flooding assessments for stakeholders and decision makers in relatively short period.
Long term variation of 137Cs inventory in the global ocean from 1957 to 2018
Authors: Inomata Yayoi , Aoyama Michio
Published: March 2021

The spatial and temporal variations in 137Cs concentrations in the surface seawater in the global ocean from 1957 to 2018 were analyzed by using the ''HAM database - global 2018'' and “IAEA-MARIS database” in order to understand the behaviors of 137Cs originated atmospheric weapons tests, nuclear fuel reprocessing plants, and nuclear power plant accidents at Chernobyl and Fukushima. The global ocean was divided into 37 boxes. The 0.5yr average value of 137Cs, apparent half residence times (Tap), and 137Cs inventory in each box was estimated. The 0.5yr average value of 137Cs in each oceanic region (box) indicate that 137Cs decreased exponentially from 1970 to 2010 in the Pacific Ocean (PO), Indian Ocean (IO), and Atlantic Ocean (AO), except for the Arctic Ocean, North Atlantic Ocean and its marginal sea due to the discharge of 137Cs from the nuclear fuel reprocessing plants. The geographical difference of 137Cs activity concentrations in the global ocean become to be small in the year of 2010. The temporal variation of 137Cs column inventory suggests that 137Cs derived from the large scale atmospheric weapon tests exist largely in the subtropical NPO, equatorial PO, and subtropical SPO (25°N-25°S). 137Cs transport from the PO to the IO occurs in the region from 0°-15°S via Indonesian through flow. The signature of 137Cs transport from the IO to the AO is also detected. The 137Cs inventory in the surface seawater in the year 2010 is estimated to be 57±17 PBq. Considering that the radioactive decay 137Cs are estimated to be 347 PBq, the 137Cs existed into the ocean interior is estimated to 173±52 PBq. These indicate that about 30% of 137Cs released into the surface seawater have been transported into the ocean interior in 2010. The 137Cs inventory in 2011 in the surface seawater in the global ocean were 69±15 PBq. The 137Cs released by the Fukushima Nuclear Power Plant 1 accident increased to 16.5±4.8 PBq and this value is in good agreement with previous studies.
Applications of a hydro-geomorphic (dis)connectivity framework to study vegetation transitions in semiarid ecosystems.
Authors: Saco Patricia , Moreno-de las Heras Mariano , Rodriguez Jose , Sandi Steven , Azadi Samira , Quijano Juan
Published: March 2021

Changes in hydro-geomorphic connectivity have been previously linked to catastrophic shifts in landscape structures and function leading to irreversible degradation. Here we present evidence and new observations to better understand the link between connectivity of water and sediments and possible phase transitions for the case of semiarid ecosystems at the catchment and hillslope scales.  We first focus on rangelands, where coevolving vegetation and landform structures lead to a distinct connectivity pattern responsible for the healthy functioning of the system. Positive feedbacks, triggered by disturbances in vegetation, water or sediment structures can alter the hydro-geomorphic connectivity leading to degradation. Our results for rangelands in Australia, from both simulations and observations, suggest that an increase in connectivity beyond a threshold may lead to irreversible degradation, meaning that the system return to a functional state is unlikely without extensive management interventions. We also analyse the case of semi-arid floodplain wetlands of the Murray-Darling Basin, where we observe that dis-connectivity during droughts promote terrestrial vegetation encroachment and degradation. Simulations and observations also indicate the presence of thresholds beyond which the recovery of the system is unlikely without interventions.
First experiences with an absolute quantum gravimeter during field campaigns
Authors: Güntner Andreas , Reich Marvin , Reinhold Andreas , Glässel Julian , Wziontek Hartmut
Published: March 2021

Recent technological advances in the field of quantum gravimetry led to the first commercially available absolute quantum gravimeters (AQG) that are designed for deployment in field surveys (AQG by Muquans, B series). Limitations of other relative or absolute gravimeters currently used for environmental applications which require highly accurate and precise data (e.g. monitoring subsurface water storage changes), are expected to be at least partly overcome with AQGs.

In this contribution, we report on the first experiences gained with the Muquans AQG-B02 during a gravimetric field survey in the vicinity of the Geodetic Observatory Wettzell (Bavarian Forest, Germany). The instrument is part of MOSES, a novel observing system of the German Helmholtz Association, comprising flexible and mobile observation modules for event-based investigation of hydrological extreme events, among other processes. To our knowledge, this is the first use of an AQG in an outdoor field campaign. During the 4-day survey, measurements with the AQG were performed on small concrete pillars at 4 field locations and partly repeated on consecutive days. In between the field measurements, reference measurements were carried out on a laboratory pillar of the Geodetic Observatory. We present the AQG field deployment with regard to transport, site design and power supply. The AQG survey is evaluated with respect to its technical and operational feasibility and the data are assessed in terms of their sensitivity, accuracy and reproducibility. Parallel recordings of environmental conditions such as wind speed and air temperature allow for assessing their potential disturbing effect on the gravity measurements. Observations with an A10 absolute gravimeter on the same sites few days before or after the AQG measurements were used for comparing the absolute gravity values.
Dynamic evolution of debris flow grain composition
Authors: Li Yong
Published: March 2021

Debris flow is composed of solid grains of different sizes. the characteristics of grain size distribution reflect the movement mode and dynamic conditions of the fluid, and have different effects on the movement of debris flow. Due to the high variability of debris flow materials, the granular interaction is bound to affect the fluid properties. The grain size distribution (GSD) of debris flow satisfies the formula: P(D)=CD-μexp(-D/Dc), where, GSD parameters μ and Dc can comprehensively reflect the change of grain composition. with μ reflecting the structure and variation characteristics of fine grains, and Dc reflecting the range of grain size. Field surveys in various regions indicate that the GSD parameters are distinct in materials of flow, source, and deposition. The GSD parameters of source soil and deposition soil are random and discrete, while the GSD parameters of fluid samples show obvious negative power function form: Dc= aμb (Figure 1). This shows that the grain composition of debris flow contains some dynamic information. In this paper, we use natural soil materials in a typical debris flow valley to conduct a series dynamically mixing and rotating experiments to simulate the flow evolution, and explore the change of grains under the action of dynamics and the effect of grain adjustment on the mobility of debris flow. The results show that the GSD shows a significant regularity after dynamic rotation. The specific performance is that μ and Dc change from the initial random discrete state to negative power correlation (Figure 2), and the appearance of this correlation corresponds to the best mobility of debris flow. At the same time, the Malvern laser grain size analyzer was used to analyze the specific surface area of fine grains (<0.20 mm) in the dynamic rotation experiment. The results show that with the increase of dynamic time, the specific surface area increases according to power law, and when the time reaches about 100 minutes, the growth slows down, and the specific surface area changes little. The experimental results are helpful for a deep understanding of the dynamics of debris flow.
Comparing digitalization of urban water processes and services in Singapore and Bengaluru
Authors: Banerjee Chandan , Saraswat Chitresh , Bhaduri Anik
Published: March 2021

Digitalization is claimed to revolutionize water utilities in many urban areas across the world, contributing to urban water security.  It involves the use of Information Technology, Data Analysis and Electronic Monitoring in urban water governance with significant improvements in quality water services and customer satisfaction. However, a holistic success story where digitalization of each and every urban water process and service, is found only in a handful of cities. The challenge in most cases is not the availability of an appropriate digital technology but the implementation of the technology. In our study, we try to find the constraints faced in the implementation processes by assessing the required enabling conditions of digitalization as well as the outcomes. Two cities, Singapore and Bengaluru as case studies were selected to compare the implementation process of Smart Water Meters, Supervisory Control and Data Acquisition (SCADA) and Flood Early Warning. Singapore is a developed city in terms of water with an excellent water management system that provides remarkable water-related services. On the other hand, Bengaluru, a rapidly growing city in India and known for its information technology and digital industry, has embarked on the path towards digitalization in water. The comparison of the implementation of these three technologies provides interesting insights that we have extended to generalized inferences about the implementation of digitalization in urban water. We have found that the enabling conditions such as the existence of enabling technologies, management capacity and conducive policy framework are crucial for implementation. Interestingly, outlining the target problems that digitalization is expected to address is equally important for achieving favourable outcomes. The inferences developed in this study will help the adoption of digital technology by urban water utilities, especially in the developing world and in turn strengthen water security.
Emergence of projected scaled patterns of extreme weather events over Europe
Authors: Ozturk Tugba , Matte Dominic , Christensen Jens Hesselbjerg
Published: March 2021

In this work, we investigate the scalability of wet and dry persisting conditions over the European domain. For this aim, we have used the EURO-CORDEX ensemble of regional climate projections at 0.11° grid-mesh for daily minimum and maximum temperature and precipitation to analyze future changes in relation with extreme weather events addressing climate warming targets of 1°C, 2°C and 3°C, respectively. A simple scaling with the annual mean global mean temperature change modeled by the driving GCM is applied. We also identify the emergence of the scaled patterns of minimum and maximum temperatures and of wet and dry persisting conditions in relation with certain extreme weather indices. In particular we focus on pattern scaling of extreme temperatures and precipitation over sub-regions over the Mediterranean basin since this region has been identified as a climate change hot spot.
Trends in volcanic degassing through eruption cycles: insights from satellite measurements
Authors: Carn Simon , Fioletov Vitali , McLinden Chris , Krotkov Nickolay , Li Can
Published: March 2021

Effective use of volcanic gas measurements for eruption forecasting and hazard mitigation at active volcanoes requires an understanding of long-term degassing behavior as context. Much recent progress has been made in quantifying global volcanic emissions of sulfur dioxide (SO2) and other gas species by expanding the coverage of ground-based sensor networks and through analysis of decadal-scale satellite datasets. Combined, these advances have provided valuable constraints on the magnitude and variability of SO2 emissions at over 120 actively degassing volcanoes worldwide. Being less constrained by the style or location of volcanic activity, satellite measurements can provide greater insight into trends in volcanic degassing during eruption cycles. Here, we present an analysis of ~15 years of volcanic SO2 measurements by the ultraviolet (UV) Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite, focused on observed trends in SO2 emissions spanning eruptions of varying magnitude. The Aura/OMI measurements have been used to estimate annual mean SO2 emissions at ~100 volcanoes active between 2005 and 2020, around 80 of which erupted during the 15-year period. Superposed epoch analysis (SEA) of SO2 emission trends for the erupting volcanoes (with eruption magnitudes ranging from Volcanic Explosivity Index [VEI] 2 to 4) provides evidence that volcanoes exhibiting higher levels of SO2 emission in the years prior to eruption typically produce eruptions of lower magnitude, and vice versa. Post-eruptive SO2 degassing exceeds pre-eruptive emissions for several years after eruptions with VEI 3-4 and may scale with eruption size; perhaps consistent with larger eruptions being supplied by larger magma intrusions which continue to degas in subsequent years. The SEA is most robust for eruptions of intermediate magnitude (VEI 3) which are the most common events in the recent global eruption record covered by the OMI measurements. Limited observations of larger eruptions (VEI 5+) suggest significant differences in degassing trends during these larger events. Future work will extend the satellite-based estimates of volcanic SO2 emissions both forward and backward in time using other UV satellite instruments, generating longer records of SO2 degassing (extending back to 1978 for the strongest volcanic sources of SO2) that will be used to further explore and constrain these relationships.  
Automatic Extraction of Intermittent Channel Systems of a Low‐Relief, Low‐Gradient Floodplain
Authors: Xu Haiqing , van der Steeg Shailesh , Torres Raymond
Published: March 2021

Intermittent floodplain channels are low‐relief conduits etched into the floodplain surface and remain dry much of the year. These channels comprise expansive systems and are important because during low‐level inundation they facilitate lateral hydraulic connectivity throughout the floodplain. Nevertheless, few studies have focused on these floodplain channels due to uncertainty in how to identify and characterize these systems in digital elevation models (DEMs). In particular, their automatic extraction from widely available DEMs is challenging due to the characteristically low‐relief and low‐gradient topography of floodplains. We applied three channel extraction approaches to the Congaree River floodplain DEM and compared the results to a channel reference map created through numerous field excursions over the past 30 years. The methods that we tested are based on flow accumulation area, topographic curvature, and mathematical morphology, or the D8, Laplacian, and bottom‐hat transform (BHT), respectively. Of the 198 km of reference channels the BHT, Laplacian, and D8 extracted 83%, 71%, and 23%, respectively, and the BHT consistently had the highest agreement with the reference network at the local (5 m) and regional (10 km) scales. The extraction results also include commission “error”, augmenting the reference map with about 100 km of channel length. Overall, the BHT method provided the best results for channel extraction, giving over 298 km in 69 km2 with a detrended regional relief of 1.9 m.