bluuebunny/crossref_metadata_2025 huggingface dataset:
Tropical Oceanic Mesoscale Cold Pools in High-Resolution Global Icosahedral Nonhydrostatic (ICON) Model from DYAMOND
Authors: Garg Piyush , Nesbitt Stephen W. , Lang Timothy J. , Priftis George
Published: March 2021

In the recent years, global kilometer-scale convection-permitting models have shown promising results in producing realistic convection and precipitation. In this study, a 2.5 km global Icosahedral Nonhydrostatic (ICON) model simulation ran for 40 days (06 UTC 01 Aug – 23 UTC 10 Aug 2016) from Dynamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) initiative was used to identify thermal cold pools (using virtual temperature) over tropical oceans. In addition to examining cold pool variability, variables such as vertical wind shear (0-600 hPa and 0-300 hPa), relative humidity, convective available potential energy (CAPE), column water vapor and surface fluxes corresponding to each cold pool were analyzed. Grid-point linear regression was applied to identify relationships between these variables and cold pool size and intensity. It was found out that there is a statistically significant regional variability in the relationships between cold pool properties and their environments across the global tropics, and cold pool size and intensity have quite different dependence on the various variables considered. Unsupervised machine learning algorithm was then applied to geospatial linear regression to identify coherent patterns explaining multi-modal feedback between cold pools and their mesoscale environments.

Previous studies have hypothesized that although accurate characterization of cold pool diurnal cycle is essential to resolve realistic deep convection in the current generation climate models, our lack of understanding of feedbacks between cold pools and convection leads to distorted diurnal cycle of precipitation. NASA’s RapidScat satellite was in a non-sun-synchronous orbit for 2014-2016 and thus was able to resolve diurnal cycle. Garg et al. (2020) gradient feature technique was applied on RapidScat’s winds to identify cold pools and observe their diurnal cycle of number, size, precipitation and associated convective system properties. Once an observed perspective of cold pool diurnal cycle is obtained, Fourier analysis was used on all the cold pool-associated variables in ICON simulation to obtain the diurnal phase and amplitude. The simulated diurnal cycle of cold pool number, size, precipitation, and other variables were observed to be similar as RapidScat. In this way, this study creates a holistic overview of cold pool-convection-precipitation-storm environment relationships using high-resolution CRM from DYAMOND and satellite observations.
Understanding the Effect of Age Uncertainty in Recurrence Analysis of Paleoseismic Records
Authors: Kempf Philipp , Moernaut Jasper
Published: March 2021

The ultimate goal of paleoseismology is to estimate the strength, location and timing of future large earthquakes. Paleoseismic records can deliver an accurate description of past hazards, which is the first step towards that goal. To understand how reliably past events forecast the timing of future events, paleoseismologists characterise the periodicity in earthquake sequences. The periodicity is often expressed by the coefficient of variation (CoV, mean-normalised standard deviation) of recurrence intervals. Depending on the CoV, fault rupture behaviour is called periodic, random or clustered. However, sedimentary records rely on age-models, which have various ways to assign age and age uncertainty to events and thus it is unclear how well the CoV can be estimated.

Most onshore paleoseismic studies rely on sedimentary sequences, where sedimentation rate is highly variable and cannot be used as a constraint (Bayesian prior) in age-depth modelling. In these onshore studies, event ages are often determined by dates constraining the event age to a minimum and maximum age and making use of the stratigraphic order of event deposits. In contrast, marine and lacustrine paleoseismic records benefit from a more stable sedimentation rate, which is a suitable prior for Bayesian age-depth models, effectively decreasing age uncertainty. The sediment thickness between event deposits in subaqueous records can thus form a reasonable estimator of recurrence intervals (RI), i.e., the relative age of the events.

Different approaches are used to calculate RIs affecting the reported CoV. For example, there is the "best" age approach, where a single "best" age (often the median of an age distribution) is assigned to each event and the difference is the RI. In another approach the RIs are calculated based on the age differences within Markov chain Monte Carlo iterations that make up the age model. The latter method draws on more information and gives a mathematically more correct estimate for RIs by keeping the probabilistic nature of the event age. This method can be applied through, e.g., the use of the Difference()-function in OxCal or through the subtraction of iteration ages of consecutive events (Bacon.Age.d()-function) from BACON age-depth models.

To quantify the effect of age uncertainty on CoVs of earthquake sequences, we first describe the uncertainty in CoVs from various synthetic earthquake recurrence patterns without age uncertainty (control). Then we simulate the effects that age uncertainty in paleoseismic records can have on earthquake sequence statistics. We evaluate when ignoring the age uncertainty while calculating the CoV is a convenient and appropriate shortcut and when it can cause considerably different results by discussing various natural cases from literature.
Use of multispectral remote sensing data to map magnetite bodies in the Bushveld Complex, South Africa: a case study of Roossenekal, Limpopo.
Authors: Twala Mthokozisi , Roberts James , Munghemezulu Cilence
Published: March 2021

The use of remote sensing in mineral detection and lithological mapping has become a generally accepted augmentative tool in exploration. With the advent of multispectral sensors (e.g. ASTER, Landsat, Sentinel and PlanetScope) having suitable wavelength coverage and bands in the Shortwave Infrared (SWIR) and Thermal Infrared (TIR) regions, multispectral sensors have become increasingly efficient at routine lithological discrimination and mineral potential mapping. It is with this paradigm in mind that this project sought to evaluate and discuss the detection and mapping of vanadium bearing magnetite, found in discordant bodies and magnetite layers, on the Eastern Limb of the Bushveld Complex. The Bushveld Complex hosts the world’s largest resource of high-grade primary vanadium in magnetitite layers, so the wide distribution of magnetite, its economic importance, and its potential as an indicator of many important geological processes warranted the delineation of magnetite.

 

The detection and mapping of the vanadium bearing magnetite was evaluated using specialized traditional, and advanced machine learning algorithms. Prior to this study, few studies had looked at the detection and exploration of magnetite using remote sensing, despite remote sensing tools having been regularly applied to diverse aspects of geosciences. Maximum Likelihood, Minimum Distance to Means, Artificial Neural Networks, Support Vector Machine classification algorithms were assessed for their respective ability to detect and map magnetite using the PlanetScope data in ENVI, QGIS, and Python. For each classification algorithm, a thematic landcover map was attained and the accuracy assessed using an error matrix, depicting the user's and producer's accuracies, as well as kappa statistics.

 

The Maximum Likelihood Classifier significantly outperformed the other techniques, achieving an overall classification accuracy of 84.58% and an overall kappa value of 0.79. Magnetite was accurately discriminated from the other thematic landcover classes with a user’s accuracy of 76.41% and a producer’s accuracy of 88.66%. The erroneous classification of some mining activity pixels as magnetite in the Maximum Likelihood was inherent to all classification algorithms. The overall results of this study illustrated that remote sensing techniques are effective instruments for geological mapping and mineral investigation, especially in iron oxide mineralization in the Eastern Limb of Bushveld Complex. 

 
Ripples going against the flow: How energy propagation determines the global structure of magnetopause surface waves
Authors: Archer Martin , Hartinger Michael , Plaschke Ferdinand , Southwood David , Rastaetter Lutz
Published: March 2021

Impulsive solar wind transients, such as pressure pulses and shocks, excite surface waves on the magnetopause. While much of this surface wave energy is advected downtail by the magnetosheath flow, recently it has been shown that some of these waves can be trapped locally forming a standing wave between the northern and southern ionospheres. It appears that this process can occur across most of the dayside magnetopause, however, it is not clear how these surface waves can resist the advective effect of the tailward flow. Through multispacecraft observations, global MHD simulations, and analytic MHD theory we show that azimuthally standing magnetopause surface waves are possible between 9-15h MLT. In this region, surface waves with Poynting vectors directed towards the subsolar point can exactly balance the advective effect of the magnetosheath flow, leading to no overall energy flow. Further downtail, however, the wave’s propagation cannot overcome advection and the usual tailward energy flow occurs. This trapping of magnetopause surface wave energy following the drivers of intense space weather may in turn have important implications on radiation belt, ionospheric, and auroral dynamics.
Interplay between melt infiltration and strain localization in the lower lithosphere of San Quintin, Baja California
Authors: Murphy Colin , Bernard Rachel , Chin Emily
Published: March 2021

How strain localizes in the lower crust and upper mantle to accommodate transcurrent plate motions is not well understood. Here we focus on a suite of lower crustal and upper mantle xenoliths from the San Quintin Volcanic Field (SQVF) in Baja California, Mexico, located along transcurrent faults at the margin of the Pacific plate. Previous work has suggested that in addition to significant strain localization, the lower lithosphere below SQVF has experienced partial melting, possibly through shear heating. The presence of even minor amounts of melt could significantly affect the deformation mechanisms accommodating strain. While previous studies of SQVF have largely focused on deformation in the upper mantle, less is known about strain localization in the lower crust. We have analyzed the composition and microstructures of nine xenoliths using wavelength dispersive spectroscopy (WDS) and electron backscatter diffraction (EBSD) to elucidate the relationship between melt infiltration and deformation in the lower crust of this actively-deforming region.

We categorize the suite of SQVF xenoliths into two textural and chemical groups: Group 1, consisting of undeformed mafic cumulates, and Group 2, consisting of foliated ultramafic peridotites and mafic granulites. Symplectites and corona textures with olivine-orthopyroxene-clinopyroxene+spinel symplectite-plagioclase layering preserved in Group 2 samples are interpreted to have resulted from basaltic melt infiltration during deformation. The orientation of the shape preferred orientations (SPO) of spinel and orthopyroxene grains relative to foliation in Group 2 samples is consistent with experimental studies of crystallization during melt infiltration. Evidence for deformation is also preserved in the form of moderate crystallographic preferred orientations (CPO), present in plagioclase, orthopyroxene, and olivine. Oxide weight percentages, calculated using electron microprobe data and modal phase abundances from WDS maps, were used to construct pseudosections in order to estimate equilibrium temperatures and pressures. The range of pressures across samples suggest a changing degree of deformation and degree of rock-melt interaction with depth in the lower crust of Baja California.
The effect of flood events on the altimetric response of river alternate bars
Authors: Carlin Mattia , Redolfi Marco , Tubino Marco
Published: March 2021

Alternate bars are large bedforms, characterized by an ordered sequence of scour and deposition zones, which often appear in rivers. It is well proved by many experimental, theoretical and numerical works that the formation of migrating alternate bars results form an intrinsic instability mechanism occurring when the width-to-depth ratio of the channel is larger than a critical threshold. Although a large amount of literature is available to describe equilibrium bar properties under steady flow conditions, much less information exists about the evolution of bars when flow discharge is variable in time. In a recent work we investigated how the long-term, average properties of bars respond to changes of the hydrological regime. This average state represents the net result of a multitude of flood events, each of them producing a different morphological alteration. However, a systematic description of how changes of the bar properties depend on the characteristics of the individual floods is still missing, as existing studies are limited to a small number of flood events, not sufficient to make a statistical description of the riverbed response. In this work, we aim at studying the time evolution of the bar amplitude in a relatively straight, channelized reach of a gravel bed river. Specifically, we considered a 10 km-long reach of the Alpine Rhine River, for which a detailed record of flow stages is available for the period from 1984 to 2010. This is accomplished by modelling the bed evolution through the theoretically-based model of Colombini et al. (1987), here applied by considering a time-varying basic flow and numerically integrating the bar amplitude. Compared with classical approaches based on numerically solving the two-dimensional shallow-water equations, our procedure allows for calculating the bar response over long periods of time with a very low computational cost. This enables for modelling different scenarios of hydrological alterations, due to dam constructions or climate changes, and to statistically analyse the expected impact on bar evolution. Assuming that bars cannot evolve when the flow is too low to fully submerge the bar crests, we identify 200 morphologically-active flood events, covering about 1.1% of the total duration of the flow series. Model results reveal that moderate flow events tend to increase the bar amplitude, while larger floods reduce the bar height. However, the value of the peak discharge alone is not sufficient to explain the morphological changes, as an important (and opposite) role is also played by the duration of the events. Specifically, longer floods tend to promote an increase of the bar height during the receding phase, which implies that a strong reduction of the bar amplitude requires intense, but relatively short flood events.
Unconstrained global simulations of ocean tides up to degree 3 for satellite gravimetry
Authors: Sulzbach Roman , Dobslaw Henryk , Thomas Maik
Published: March 2021

Tidal de-aliasing of satellite gravimetric data is a critical task in order to correctly extract gravimetric signatures of climate signals like glacier melting or groundwater depletion and poses a high demand on the accuracy of the employed tidal solutions (Flechtner et al., 2016). Modern tidal atlases that are constrained by altimetry data possess a high level of accuracy, especially for partial tides exhibiting large open ocean signals (e.g. M2, K1). Since the achievable precision directly depends on the available density and quality of altimetry data, the accuracy relative to the tidal amplitude drops for minor tidal excitations (worse signal-to-noise ratio) as well as in polar latitudes (sparse satellite-data). In contrast, this drop in relative accuracy can be reduced by employing an unconstrained tidal model acting independently of altimetric data.
We will present recent results from the purely-hydrodynamic, barotropic tidal model TiME (Weis et al., 2008) that benefit from a set of recently implemented upgrades. Among others, these include a revised scheme for dynamic feedbacks of self-attraction and loading; energy-dissipation by parametrized internal wavedrag; partial tide excitations by the tide-generating potential up to degree 3; and a pole-rotation scheme allowing for simulations dedicated to polar areas. Benefiting from the recent updates, the obtained solutions for major tides are on the same level of accuracy as comparable modern unconstrained tidal models. Furthermore, we show that the relative accuracy level only drops moderately for tidal excitations with small excitation strength (e.g. for minor tides), thus narrowing down the accuracy gap to data-constrained tidal atlases. Exemplarily for this, we introduce solutions for minor tidal excitations of degrees 2 and 3 that represent valuable constraints for the expected ocean tide dynamics. While they are currently not considered for GRACE-FO de-aliasing we demonstrate that third-degree tides can lead to relevant aliasing of satellite gravity fields and correspond closely to recently published empirical solutions (Ray, 2020).
CO2 temporal variability over Mexico City metropolitan area  from ground-based FTIR column measurements
Authors: Taquet Noémie , Stremme Wolfgang , González del Castillo Eugenia , Bezanilla Alejandro , Grutter Michel , Blumenstock Thomas , Hase Frank , Dubravica Darko , Blandin Edouard , Lopez Morgan , Ramonet Michel
Published: March 2021

About seventy-five percent of the global carbon dioxide emissions from fossil fuel come from cities. Reducing anthropogenic greenhouse gas emissions, in particular in developing countries, is a major concern for local, national and international policies. Different mitigation strategies are and will be implemented to reduce greenhouse gas emissions, and the evaluation of their success and their perennization depends on the ability to continuously measure and quantify the effects at different spatial and temporal scales.

Using continuous solar absorption Fourier transform Spectroscopy (FTIR) column measurements in both urban and background environments over the Mexico City metropolitan area, together with in situ datasets, we explore the spatial and temporal variability of the CO2 concentration over the 5 last years in the region. Measurements were performed from three permanent stations equipped with high and low spectral resolution FTIR spectrometers since 2012, 2016 and 2018, respectively, the first is part of the NDACC network while the other two contribute to the COCCON international initiative.

In the frame of the Mexico City’s Regional Carbon Impacts (MERCI-CO2) project, 4 complementary sites equipped with EM27/Sun instruments were temporarily implemented within the megacity since autumn 2020. In particular, our time series encompass the COVID shutdown in MCMA. In this contribution we present results of the long term measurements in background and urban environment, intercomparison measurements, and preliminary results of the temporary MERCI-CO2 stations. In addition we report about the obstacles and opportunities of this intensive measurement campaign.
The contribution of föhn winds to northeast Greenland summer melt and their relationship with atmospheric rivers
Authors: Mattingly Kyle , Turton Jenny , Wille Jonathan , Fettweis Xavier , Noël Brice
Published: March 2021

Atmospheric Rivers (ARs), narrow filaments of concentrated water vapor transport, have direct impacts on the surface mass balance (SMB) of the western Greenland Ice Sheet through increased summer melting in the ablation area and increased snowfall in higher altitudes. Here, we show that an additional effect of ARs on SMB comes from the development of föhn winds, whereby the air is adiabatically warmed as it descends. As ARs pass over the ice sheet and deposit precipitation in northwest Greenland, the air subsequently flows down the leeward slope and the warm, dry conditions contribute to increased melting in the northeast, and more specifically on the Nioghalvfjerdsfjorden (or 79N) Glacier.

 

We identify föhn conditions using an automated detection algorithm applied to MAR and RACMO2 regional climate model output. These data are paired with an AR detection algorithm and self-organizing map (SOM) classification applied to MERRA-2 and ERA5 reanalyses, in order to investigate connections between regional circulation patterns, ARs, föhn winds, and ice sheet SMB. We find that föhn conditions and associated surface melt are increased for periods of 1–3 days after anomalous southerly and southwesterly water vapor transport by ARs through Baffin Bay and the Nares Strait. Approximately 70% of the ARs which make landfall in the northwest sector of Greenland lead to the development of föhn winds on the northeast coast. The frequency of AR-induced föhn conditions in the northeast has increased in the last 40 years, in line with an increase in the strongest ARs in the northwest. We also find that anomalous northerly moisture transport from the Lincoln Sea generates enhanced melt in the lowest (0–500m) elevations of northeast Greenland, while below-average surface melt occurs during all other identified moisture transport regimes.
Quantifying errors of multiple gridded soil moisture products in Sweden using triple collocation analysis and traditional evaluation method with ICOS data
Authors: Duan Zheng , del Rosario Nina , Dong Jianzhi , Gao Hongkai , Peng Jian , Lu Yang , Liu Junzhi , Vermeulen Alex
Published: March 2021

Soil moisture is an Essential Climate Variable (ECV) that plays an important role in land surface-atmosphere interactions. Accurate monitoring of soil moisture is essential for many studies in water, energy and carbon cycles. However, soil moisture is characterized with high spatial and temporal variability, making conventional point-based in-situ measurements difficult to sufficiently capture these variabilities given the often lack of dense in-situ network for most regions. Considerable efforts have been made to explore satellite remote sensing, hydrological and land surface models in estimating and mapping soil moisture, leading to increasing availability of different gridded soil moisture products at various spatial and temporal resolutions. The accuracy of an individual product varies between regions and needs to be evaluated in order to guide the selection of the most suitable products for certain applications. Such evaluation will also benefit product development and improvements. The most common (traditional) evaluation method is to calculate error metrics of the evaluated products with in-situ measurements as ground truth. The triple collocation (TC) analysis has been widely used and demonstrated powerful in evaluation of various products for different geophysical variables when ground truth is not available.

The Integrated Carbon Observation System (ICOS) is a research infrastructure with aim to quantify the greenhouse gas balance of Europe and adjacent regions. A standardized network of more than 140 research stations in 13 member states has been established and is operated by ICOS to provide direct measurements of climate relevant variables. The ICOS Carbon Portal offers a 'one-stop shop' freely for all ICOS data products at https://www.icos-cp.eu/observations/carbon-portal. This study evaluates for the first time a large number of different satellite-based and reanalysis surface soil moisture products at varying spatial and temporal resolutions using ICOS measurements from 2015 over Sweden. Evaluated products include ESA CCI, ASCAT, SMAP, SMOS, Sentinel-1 derived, ERA5 and GLDAS products. In order to quantify spatial patterns of errors of each individual product, TC analysis is applied to different combinations of gridded products for spatial evaluation across entire Sweden. The performance of products in different seasons and years is evaluated. The similarity and difference among different products for the drought period in the year 2018 is particularly assessed. This study is expected to improve our understanding of the applicability and limitations of various gridded soil moisture products in the Nordic region.
Coupled solid Earth – Antarctic ice sheet simulations with VILMA and PISM
Authors: Albrecht Torsten , Bagge Meike , Winkelmann Ricarda , Klemann Volker
Published: March 2021

The Antarctic Ice Sheet rests on a bed that is characterized by tectonical activity and hence by a heterogeneous rheology. Spots of extremely weak lithosphere structure could have strong impacts on the Glacial Isostatic Adjustment and hence on the stability of the ice sheet, possibly also for confined glacier regions and on timescales of decades down to even years (Barletta et al., 2018).

We coupled the VIscoelastic Lithosphere and MAntle model (VILMA) to the Parallel Ice Sheet Model (PISM) and ran simulations over the last two glacial cycles. In this framework, VILMA considers both viscoelastic deformations of the solid Earth and gravitationally consistent mass redistribution in the ocean by solving for the sea-level equation (Martinec et al., 2018). In turn, PISM interprets this as a vertical shift in bed topography that directly affects the stress balance within the ice sheet and hence the grounding line dynamics at the interface of ice, ocean and bedrock.

Here we present first results of the coupled Antarctic glacial-cycle simulations and investigate technical aspects, such as optimal coupling time steps, iteration schemes and convergence, for both one-dimensional and three-dimensional Earth structures. This project is part of the German Climate Modeling Initiative, PalMod2.

 

References:

Barletta et al., 2018. Observed rapid bedrock uplift in Amundsen Sea Embayment promotes ice-sheet stability. Science, 360, pp.1335-1339. DOI: 10.1126/science.aao1447

Martinec et al., 2018. A benchmark study of numerical implementations of the sea level equation in GIA modelling. Geophysical Journal International, 215(1), pp.389-414. DOI: 10.1093/gji/ggy280

 
Heterogeneous response of ecosystem productivity to anthropogenic modifications in different bioclimatic locations in northern high latitudes.
Authors: Miles Victoria , Ezau Igore
Published: March 2021

Fragile northern high-latitude ecosystems are changing rapidly, driven by a warmer climate and extensive socio-economic development. These pressures lead to disruption of ecosystem functioning. Ecosystem productivity and phenology are indicators of ecosystem functioning. Ecosystem productivity changes such as “greening” or “browning” are highly dependent on local bioclimatic conditions. In this study, we evaluate the response of vegetation productivity in urban, semi-natural (urban–rural), and natural areas located in different bioclimatic conditions. The study is based on remote sensing data, geographic information systems (GIS), and statistical methods. We use moderate-resolution satellite spectroradiometer (MODIS) data from 2000–2019. The results show a high contrast in productivity between urban, semi-natural, and natural vegetation in different bioclimatic zones. The low productivity of urban vegetation contrasts with higher productive semi-natural and natural vegetation in the Atlantic and Middle boreal zones. However, in the Northern boreal zone, urban areas are the greenest and the productivity of urban vegetation corresponds to semi-natural and natural vegetation. The semi-natural vegetation shows similar productivity to natural in the Atlantic, but in the Middle boreal zone, we observe contrasting productivity. In the Northern boreal zone, the semi-natural vegetation more productive than natural. We conclude that in the colder climatic conditions, the anthropogenic impact has a positive effect on ecosystem productivity. The spatial heterogeneity of productivity indicates different reactions of certain types of vegetation, as well as local effects, which are clearly important against the background of the regional climate response. These factors need to be accounted for in developing adaptation strategies for northern urban areas.
Efficacy of struvite as a phosphorus source for alfalfa in organic cropping systems
Authors: Thiessen Martens Joanne , Schneider Kimberley , Zvomuya Francis , Entz Martin
Published: March 2021

Soil phosphorus (P) deficiency is common in organic cropping systems in which access to manure or other suitable P sources is limited. Insufficient P supply may be particularly detrimental to crop yields in systems relying on biological nitrogen fixation by legumes. High-purity struvite (magnesium ammonium phosphate hexahydrate) recovered from wastewater is gaining attention as a potential P source for organic crops, but little is known about the soil-crop dynamics associated with struvite application to legumes in organic cropping systems. Our objective was to assess the effect of struvite application on alfalfa productivity, P uptake, and apparent fertilizer recovery efficiency in soils with low soil test P (STP) under both field and controlled conditions. A field experiment was conducted in Manitoba, Canada (clay soil, pH 8, Olsen-P 2-3 mg kg-1), in which an existing alfalfa-grass forage stand was amended with differential rates of granular struvite and monitored over three growing seasons. A complementary pot experiment compared alfalfa response to differing rates of struvite application, relative to a soluble P fertilizer (monoammonium phosphate, MAP), in two low-STP but otherwise contrasting soils (clay texture, pH 8.0, organic matter 5.6%, Olsen-P 6 mg kg-1; sandy loam texture, pH 7.1, organic matter 3.2%, Olsen-P 10 mg kg-1). Struvite application increased forage shoot biomass yield and P concentration in the field experiment, with larger yield gains relative to the control in the second and third growing seasons. Apparent fertilizer P recovery was 26-27% over three growing seasons, regardless of struvite application rate. In the pot experiment, alfalfa yield was similar for plants fertilized with struvite or MAP but differed with soil type. Overall, our results indicate that struvite is an effective P source for organically grown alfalfa and can help to alleviate P deficiency in organic cropping systems.
Role of fluid on earthquake occurrence: Example of the 2019 Ridgecrest and the 1997-2016 Central Apennines sequences 
Authors: Jugurtha Kariche
Published: March 2021

This paper focuses on the study of the temporal evolution of seismicity and related fluid migration following major earthquake sequences occurred in the central Apennines and Eastern California Shear Zone over the last two decades: The 1997 Colfiorito sequence, the 2009 L’Aquila sequence, the 2016 Amatrice-Norcia sequence and the 2019 Ridgecrest sequence. The availability of different high-quality seismic catalogs offers the opportunity to evaluate in detail the temporal evolution of the earthquake's size distribution (or b value) and estimate the effect of the fluid flow process in triggering seismicity. For all seismic sequences, the b value time series show a gradual decrease from a few months to one year before mainshocks. The gradual decrease in the b value is interpreted in terms of coupled fluid-stress intensity as a gradual increase in earthquake activity due essentially to the short-term to intermediate-term pore-fluid fluctuations. Based on laboratory experiments results, the observed short–term fluctuation of b value is presented here as an accelerating cracks growth due essentially to the fluid flow instability.  Despite that the occurrence of seismic precursors could have been predictable in areas with high dense seismic networks, the different b value time series show a difficulty to establish a correspondence between the duration of the foreshock activity and the magnitude of the next largest expected earthquake. This may explain that the spatial and temporal evolution of fluid migration controls the size of the ruptures.
Sub-seasonal forecast capability for Arabian Peninsula convective extremes using convective-permitting regional climate modeling
Authors: Chang Hsin-I , Castro Christopher L , Risanto Christoforus Bayu , Luong Thang , Hoteit Ibrahim
Published: March 2021

Severe weather associated with convective thunderstorms is becoming more intense globally and is also observed in the Arabian Peninsula (AP). AP convective extremes are often observed during winter season (October to March). Improvements in extreme weather forecast for sub-seasonal to seasonal forecast increase the preparedness of convective extremes and related hazards. We designed a series of ensemble forecast downscaling using the Weather Research and Forecasting model (WRF) at convective-permitting spatial scale. The driving global sub-seasonal to seasonal reforecast is provided by the European Centre for Medium-Range Weather Forecasts (ECMWF).

Sub-seasonal WRF simulations are performed on the AP’s top 20 extreme precipitation events reported in the last 20 years, downscaling from the 11 ECMWF hindcast ensemble members. Each of the events recorded at least 20 mm/day rainfall in the Jeddah station. Several aspects of the simulated events are evaluated: (1) Precipitation forecast capability: determine forecast window of opportunity in the regional climate model at 1-week, 2-week and 3-week lead time, identify the value added using convective-permitting type modeling; (2) Teleconnection pattern forecast capability: determine forecast skill for the dominant large scale pattern related to the convective extremes in the driving ECMWF reforecasts and ERA-Interim reanalysis data; (3) Dominant synoptic patterns associated with the AP’s top 20 extreme events: identify forecast capability for different synoptic-driven extreme events. Historic data analysis identified 3 general synoptic patterns that lead to precipitation extreme. The top 20 extreme events are parsed into the 3 synoptic groups. Sub-seasonal forecast evaluations are then performed with statistical analysis tools commonly used in operational forecast evaluation, such as Probability of Detection (POD), False Alarm Rate (FAR) and Relative Operating Characteristics (ROC); (4) Mesoscale convective system (MCS) tracking: objectively tracking the MCS clouds in satellite observation and WRF downscaled reforecasts using cloud top temperature and precipitation. Through the designed analyses, we can collectively show the ensemble forecast skills for the largest convective events in the AP and advancement in forecast capability at sub-seasonal time scale.
A regularized continuum model for fault zones with rate and state friction
Authors: Goudarzi Mohsen , de Borst René , Gerya Taras , Li Meng , Ylona van Dinther
Published: March 2021

Accurate representation of fault zones is important in many applications in Earth sciences, including natural and induced seismicity. The framework developed here can efficiently model fault zone localization, evolution, and spontaneous fully dynamic earthquake sequences in a continuum plasticity framework. The geometrical features of the faults are incorporated into a regularized continuum framework, while the response of the fault zone is governed by a rate and state-dependent friction. Although a continuum plasticity model is advantageous to discrete approaches in representing evolving, unknown, or arbitrarily positioned faults, it is known that either non-associated plasticity or strain-softening can lead to mesh sensitivity of the numerical results in absence of an internal length scale. A common way to regularize the numerical model and introduce an internal length scale is by the adoption of a Kelvin-type visco-plasticity element. The visco-plastic rheological behavior for the bulk material is implemented along with a return-mapping algorithm for accurate stress and strain evolution. High slip rates (in the order of 1 m/s) are captured through numerical examples of a predefined strike-slip fault zone, where a detailed comparison with a reference discrete fault model is presented. Additionally, the regularization effect of the Kelvin viscosity parameter is studied on the fault slip velocity for a growing fault zone due to an initial material imperfection.  The model is consistently linearized leading to quadratic convergence of the Newton solver. Although the proposed framework is a step towards the modeling of earthquake sequences for induced seismicity applications, the numerical model is general and can be applied to all tectonic settings including subduction zones.

 

 

 

 
Linking stakeholder scenarios and shared socioeconomic pathways for policy making in human-water systems
Authors: Alizadeh Mohammadreza , Adamowski Jan , Inam Azhar
Published: March 2021

Climate change has caused many environmental problems, as well as water and food insecurity, and health and social impacts in many parts of the world, and especially in the world’s vulnerable regions such as developing countries. Studies have demonstrated the impacts of socio-economic and climate changes and how they result in water and environmental problems at global and regional scales. Socio-economic variation and climatic change influence the dynamic interaction of human and water systems, and our ability to address environmental problems at sub-regional scales. From this perspective, the Shared Socio-economic Pathways (SSPs), as a form of alternative development scenarios, were recently introduced to help decision-makers to cope with uncertain futures and improve their policies for mitigation and adaptation to climate change. To take advantage of SSP scenarios for policy guidance at regional and national scales, it is necessary to explore the socio-economic feedbacks and water management policies informed by different sub-regional knowledge sharing through stakeholders’ narratives. In this study, we link SSP scenarios developed with regional stakeholders using a coupled socio-economic and environmental model, in conjunction with stakeholder-generated narrative storylines for a sub-region of Pakistan. The framework allows for linking corresponding scenarios across different uncertainty levels to improve regional scale policy making, while providing knowledge regarding the future of human-water systems under a range of plausible future climate and socio-economic scenarios.
How strongly are mean and extreme precipitation coupled?
Authors: Nishant Nidhi , Sherwood Steven
Published: March 2021

Changes in mean and extreme precipitation are among the most important consequences of climate change. Here we examine the relationship between the mean and three different measures of extreme precipitation over the Australian continent, from a regional climate projection ensemble. We show that model uncertainty in mean and extreme precipitation are tightly coupled for both the present-day climate and future changes. On the continental scale the differences in mean precipitation explain 80-99% of the variance in the extremes. We also find that in most regions except along the coasts, precipitation statistics projected by regional modelling system (RCM) are highly predictable from the mean precipitation of the global model (GCM) providing the boundary conditions. In coastal regions RCMs are more accurate than GCMs and they also have more impact on present-day statistics, however, this impact disappears for future changes, suggesting that improved present-day accuracy will not carry over to future changes.
Collisional Langevin approach to bed load sediment velocity distributions
Authors: Pierce Kevin , Hassan Marwan
Published: March 2021

Bed load experiments reveal a range of possibilities for the downstream velocity distributions of moving particles, including normal, exponential, and gamma distributions. Although bed load velocities are key for understanding fluctuations in transport rates, existing models have not accounted for the full range of observations. Here, we present a generalized Langevin model of particle transport that includes turbulent drag and episodic particle-bed collisions. By means of analytical calculations, we demonstrate that momentum dissipation by particle-bed collisions controls the form of the bed load velocity distribution. As collisions vary between elastic and inelastic, the velocity distribution interpolates between normal and exponential. These results add context to conflicting experiments on bed load velocities and suggest that granular interactions regulate sediment dynamics and transport rate fluctuations.
Global 6-dimensional hybrid-Vlasov modelling of the magnetosphere: First Vlasiator results
Authors: Palmroth Minna , Ganse Urs , Battarbee Markus , Turc Lucile , Pfau-Kempf Yann , Bussov Maarja , Grandin Maxime , Johlander Andreas , Suni Jonas , Dubart Maxime , Papadakis Kostis , Alho Markku
Published: March 2021

Numerical simulations are key in modern space physics, as they can be used as 1) context to data, 2) predict future behaviour of the system, 3) understand the system using unforeseen boundary conditions, and increasingly also in 4) discovering new phenomena that are hard to be observed using point-wise satellite measurements. Especially, the discovery of new phenomena pertains to global systems, where phenomena of interest may be initiated far away from the point of observations. The most typical method of simulating the global solar wind - magnetosphere - ionosphere system is based on magnetohydrodynamics (MHD), which is however not representing the actual plasma behaviour in locations where kinetic physics becomes important. Such regions are e.g., the foreshock - magnetosheath interaction, reconnection, and the inner magnetosphere.

Vlasiator is the world’s first and so far the only global simulation based on the hybrid-Vlasov approach that simulates the ion distributions accurately without noise. The simulation has, for computational reasons, been so far executed in 2D real space. Even so, the global 5D Vlasiator results have shown without a doubt that ion-kinetic effects cannot be neglected from the large scales, as small-scale phenomena affect large scales and vice versa. This scale coupling leads to phenomena that are not predicted using local simulations without proper boundary conditions, or with spacecraft measurements lacking the global context.

Here, we present the world’s first global 6-dimensional ion-kinetic global magnetospheric simulation run, accurate both locally and globally. The simulation box extends from the dayside to the nightside, and includes global dynamics and both dayside and nightside reconnection regions. We will investigate unambiguously for the first time the dayside magnetopause reconnection as driven by the kinetic variations in the magnetosheath, and tail reconnection as driven by magnetic flux from the dayside.
Optimization of Low Impact Development Based on SWMM and Genetic Algorithm: Case Study in Tianjin, China
Authors: Xiao Meng , Li Yu , Huang Jinhui Jeanne
Published: March 2021

Low impact development (LID) is an important measure to control the total amount of rainwater runoff from the source and solve the problem of non-point source pollution. However, there are many kinds of LID facilities, and the selection and layout of these facilities are restricted by the local physical and geographical conditions, hydrogeological characteristics, water resources, rainfall patterns and other factors. Therefore, the selection of LID facilities and the determination of optimization scheme are the main challenges for the construction of LID rainwater system. In this study, SWMM model and genetic algorithm (GA) are used to optimize the layout of LID. The multiple objectives include runoff reduction, occupied area and lifecycle cost. The results show that the combined LID facility scheme has obvious control effect on runoff reduction in the 10-year rainfall process.
A novel method to diagnose factors influencing in leakage in water distribution systems including extreme weather events
Authors: Yan Ran , Li Yu , Huang Jinhui Jeanne
Published: March 2021

During January 2016 and December 2020, eastern and southern China including Shanghai experienced a rapid drop in temperatures along with snow. This cold wave which also had a severe impact on water distribution networks. Leakage of pipe network causes serious economic loss and waste of water resources. Nonetheless, cold wave is not the only factor affecting leakage from a pipe network. There are also other factors including the burial depth of pipes, the materials of pipes, the diameters of pipes, break history and so on. In this work, we use machine learning method and Bayesian distribution regression to explore the relationship between pipe leaks and impact factors. Based on results, risk maps of water distribution networks are generated. This research indicated that which risk factors is important for leakage detection and water loss management of urban water supply network, which can be promising for wide practical applications due to rapid expansion of data.
Response of stemflow as a function of various characteristics of the precipitation event
Authors: Zabret Katarina , Šraj Mojca
Published: March 2021

The amount of rainfall intercepted by vegetation is usually estimated by considering the amounts of precipitation, throughfall and stemflow. As stemflow values most often present only a minor fraction of the partitioned rainfall, they are frequently neglected. In addition, stemflow development during the event and under different conditions is also rarely analysed. At the study plot in Ljubljana, Slovenia, rainfall partitioning components and rainfall event characteristics have been measured since 2014. This database with high frequency measured data was used to analyse how different rainfall event properties influence the development of stemflow measured under the birch tree (Betula pendula Roth.).

156 rainfall events with observed stemflow were selected. For each event a figure showing increase of rainfall and stemflow during the event was prepared. The figures were grouped according to their similarity using a hierarchical clustering approach. For each group the significant event characteristics were analysed. Certain influence on the response of the stemflow was observed for rainfall amount and its intensity, duration of dry period before the event, as well as for average air temperature and air humidity during the event. The figures showing the situation for rainfall events with the smallest rainfall amounts and the lowest intensities were grouped in the cluster 1. The cluster 2 combined stemflow events with negligible response to rainfall development. These events delivered less than 20 mm of rainfall, while their duration was on average 5 hours, which is significantly less than duration of the events, grouped in the clusters 3 and 4. The average air temperature for events, grouped in cluster 2, was quite high as 65% of the events were observed during leafed phenophase. These events were also characterised with generally quite long dry periods before the event. The events merged in the cluster 3 showed noticeable response to rainfall development as the stemflow dynamics followed the increase of the rainfall. These events were characterized by an average of 30 mm of rainfall, reaching up to 102 mm per event. Also rainfall intensity was quite high and similar to rainfall intensities, significant for events grouped in cluster 4. It consisted of events with the strongest stemflow response, which coincide also with the largest amounts of rainfall on average per event. However, air temperature was the lowest and air humidity was the highest during the events, grouped in the cluster 4, which corresponds to mainly leafless phenophase.