bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison between forecasts of reference evapotranspiration and ETo values calculated using data from different climatic conditions
Authors: Ben Hamouda Ghaieth , Ventura Francesca , Zaccaria Daniele , M. Bali Khaled , L. Snyder Richard
Published: March 2020

Evapotranspiration is the transfer of water from the earth's surface to the atmosphere. It comprises the sum of water losses to atmosphere due to the processes of evaporation of moisture from soil, water bodies and wet plant canopies, and the transpiration of water from plants. Forecasts of this crucial component of the hydrologic cycle can be very valuable for growers, farm managers, irrigation practitioners, water resource planners and managers, and reservoir operators for their planning, allocation, delivery and scheduling decisions, as well as to hydrologic scientists for research purposes. Verifying the reliability of models’ forecasts is among the critical tasks for development and performance evaluation of physical models. In fact, the verification allows understanding the models’ behavior, and evaluating their applicability and dependability. The US National Weather Service (NWS) has released a product that provides forecasts of reference evapotranspiration (FRET) at 2.5-km grid resolution for the entire continental US. In this study, a comparison is made between ETo estimates from FRET and ETo values calculated by the California Irrigation Management Information System (CIMIS) for 68 days during summer 2019. Both the FRET forecasts and ETo values were obtained from NWS and CIMIS, respectively, on the basis of 15 CIMIS locations that are representative of different climatic conditions in California. In addition, air temperature, dew point temperature, relative humidity, wind speed, and vapor pressure deficit (VPD) data were also collected/calculated from the NWS and CIMIS websites to analyze the sensitivity of FRET forecasts to predictions of these parameters. All FRET forecasts were performed with timescales of 1, 3, 5 and 7 days. Statistical indices were calculated to assess the dependability of FRET values. They showed a good correlation of the FRET model outputs with CIMIS ETo data, with some differences depending on the climatic characteristics of selected weather stations’ locations, suggesting that FRET data could be valuable for anticipating near-future water demand and improve irrigation management in California.
Dust and biomass burning aerosol transport in South Atlantic during AEROCLO-sA
Authors: Chaboureau Jean-Pierre , Labbouz Laurent , Flamant Cyrille , Hodzic Alma
Published: March 2020

We investigate the transport of dust and biomass burning aerosols in South Atlantic during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign in September 2017. A regional Meso-NH simulation has been run using a 12-km horizontal grid-spacing without deep convection parameterization, an on-line dust emission scheme, a passive tracer of biomass burning aerosol (BBA) emitted using the daily Global Fire Emissions Database and online-computed backward trajectories. The simulation captures both the aerosol optical depth and the vertical distribution of aerosols as observed from airborne and spaceborne lidars. It also reproduces the occurrence of deep convection over Congo and stratocumulus over South Atlantic well. A Lagrangian analysis reveals the origin of aerosols in the South Atlantic. Dust aerosols found just above the stratocumulus were emitted from the coasts and the Ethosha Pan a few days earlier. The BBAs located between 1 and 5 km come mainly from Angola in about 3.5 days. The 8-12 km layer is fed by up to 12 % of the air masses that experienced convection over the Congo Basin in the last 5 days. This amount is much reduced in the sensitivity simulation with a deep convection parameterization.
Electron Bernstein waves Driven by the Parallel Electron Crescent in the Reconnection Exhaust Region
Authors: Dokgo Kyunghwan , Hwang Kyoung-Joo , Burch James L. , Yoon Peter H. , Graham Daniel B. , Li Wenya
Published: March 2020

The recently launched NASA’s Magnetosphere Multiscale (MMS) mission enables investigations of multi-scale phenomena in the reconnection process. Especially, the MMS spacecraft revealed that high-frequency waves of electron time scales exist near the electron diffusion region (EDR) due to complex electron distributions. As such waves are generated near the EDR, they could significantly affect the environment of the EDR via wave-particle interactions.

 We investigated the September 19, 2015 event when the MMS spacecraft crossed the reconnection exhaust region. The MMS spacecraft observed a parallel electron crescent, which is known to be generated by the cyclotron turning due to the normal magnetic field in the reconnection exhaust region. At the same time, highly discrete waves were observed in the power spectrum of the electric field. The wave frequency ranged between 6  ~ 14 Fce (Fce: electron cyclotron frequency), and the power of perpendicular components was larger than the parallel component. Therefore, they featured electron Bernstein waves. By modeling the parallel electron crescent as a sum of 18 ring-shaped electron distributions, we calculate the linear dispersion relation using a numerical solver. The linear growth rates agreed with the power spectrum of the electric field, which means that the parallel electron crescent locally drove the electron Bernstein waves. Together with previous studies of high-frequency waves, our work could provide a diagram of high-frequency wave distributions in the reconnection geometry.
Current sheets, magnetic islands and associated particle acceleration in the solar wind as observed by Ulysses near the ecliptic plane
Authors: Malandraki Olga , Khabarova Olga , Bruno Roberto , Zank Gary , Li and the ISSI-405 team Gang
Published: March 2020

Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energize particles up to several MeV/nuc. Stream-stream interactions as well as the heliospheric current sheet – stream interactions lead to formation of large magnetic cavities, bordered by strong current sheets (CSs), which in turn produce secondary CSs and dynamical small-scale magnetic islands (SMIs) of ~0.01AU or less owing to magnetic reconnection. It has been shown that particle acceleration or re-acceleration occurs via stochastic magnetic reconnection in dynamical SMIs confined inside magnetic cavities observed at 1 AU. The study links the occurrence of CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV-MeV/nuc energies at ~5.3 AU. We analyze selected samples of different plasmas observed by Ulysses during a widely discussed event, which was characterized by a series of high-speed streams of various origins that interacted beyond the Earth’s orbit in January 2005. The interactions formed complex conglomerates of merged interplanetary coronal mass ejections, stream/corotating interaction regions and magnetic cavities. We study properties of turbulence and associated structures of various scales. We confirm the importance of intermittent turbulence and magnetic reconnection in modulating solar energetic particle flux and even local particle acceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondary stochastic particle acceleration, which changes the observed energetic particle flux time-intensity profiles and increases the final energy level to which energetic particles can be accelerated in the solar wind.
Durability of a ventilated stone facade: A case study of a limestone facade affected by the corrosion of the anchorage system
Authors: Pires de Almeida Ribeiro Vera
Published: March 2020

The mechanical behavior of a natural stone ventilated facade is inevitably based on the correct execution of both anchoring elements, stone cladding and enclosure support, either with brick masonry walls or reinforced concrete walls. In the case studied in the present work, the origin of the damages on the facade of a building located in Lisbon has been analyzed, where stone detachments were starting to occur. This enclosure is a ventilated facade cladded with Portuguese limestone Lioz slabs. Non-destructive borescope analysis of the metallic anchoring system employed was performed, as well as X-Ray fluorescence laboratory analysis (FRX) for chemical characterization of the anchoring material. Results obtained demonstrated the problem cause on the stone facade due to incorrect metallic anchoring selection and poor execution combined with stress corrosion effect, especially for slabs with larger dimensions.
The vulnerability of water availability in Peru due to climate change: A probabilistic Budyko analysis
Authors: Huerta Adrian , Lavado Waldo , Rau Pedro
Published: March 2020

This study provides for the-first-time a water availability analysis at drainage and basin-scale in Peru. Using new gridded datasets of precipitation and temperature, along with six global actual evapotranspiration estimations from remote sensing products, the vulnerability of water resources due to climate change is evaluated. This is addressed under a bottom-up approach and probabilistic Budyko framework that enables us to measure the associated uncertainty. First, to select an adequate estimation of long-term actual evapotranspiration, we compared at basin-scale the remote sensing products with long-term actual evapotranspiration inferred from a water-balance (precipitation minus discharge) and deterministic Budyko (aridity and evaporative index relationship). Later, the probabilistic Budyko is calibrated using the adequated remote-sensed actual evapotranspiration and is cross-validated at country, drainage, and basin-scale. Finally, the water availability vulnerability (measured as the relative change of precipitation minus actual evapotranspiration from historical estimates) and associated uncertainty is computed from the probabilistic Budyko along with climate spaces from variations of potential evapotranspiration (from temperature) and precipitation. The main results show that GLEAM, MEAN, and TerraClimate are the highest-ranked products in terms of estimation of long-term mean actual evapotranspiration across basins with low bias, RMSE, and high R. GLEAM and MEAN present lower bias and RMSE, and TerraClimate estimate very well the spatial distribution of actual evapotranspiration (highest-ranked R). On the contrary, Zhang, MODIS16, and SSEBop are less efficient based on most criteria evaluation. Therefore, as reference for actual evapotranspiration, we select MEAN which represents the linear averaging of remotely sensed products. From this perspective, we expect to minimize the negative bias and preserve the spatial resolution from individual actual evapotranspiration products. Achieved the three main long-term variables, we calibrate and cross-validate the probabilistic Budyko in terms of the evaporative index. The evidence suggests that the regional distribution of the Budyko parameter accomplishes errors of +-2% at the country and drainage-scale and +-9% as average at basin-scale. Thus, the probabilistic Budyko framework provides great performance. Based on this evaluation, we figure out that basins located in the Andes, especially in the southern, showed lower critical precipitation change (less than 10%) to increase the vulnerability of water availability by 25%.

This research is part of the multidisciplinary collaboration between British and Peruvian scientists (NERC, COCYTEC).
Strong mitigation of net global warming potential (GWP) via short-term aerobic pre-digestion of green manured soil in rice paddy
Authors: Song Hyeonji , Lee Jin Ho , Cho Songrae , Chae Hogyeong , Kim Pil Joo
Published: March 2020

 Cover crop cultivation is strongly recommended during fallow season to increase soil organic carbon (SOC) stock. However, since its biomass recycling as green manure can dramatically increase greenhouse gas (GHG) emission, in particular, methane (CH4) during rice cropping season, smart cover crop management strategy should be developed. In our previous research, CH4 emission during cropping season was dramatically reduced via short-term aerobic decomposition before irrigation (Lee et al.). However, due to a fast response rate of aerobic decomposition, the effect of mitigating CH4 emission could be offset by SOC depletion which results in accelerating global warming. To evaluate the comprehensive impact of the short-term aerobic decomposition on global warming, net global warming potential (GWP), defined as the difference between GWP and SOC stock change was employed. SOC stock change was estimated using net ecosystem carbon budget (NECB), a balance between soil C input and output. The mixture of barley and hairy vetch cultivated during the dried fallow season, and then its whole biomass was incorporated 0-30 days before irrigation for rice transplanting. The aerobic decomposition of cover crop biomass significantly reduced CH4 emission by 24-85% over control but negligibly influences N2O emission. Total C input and output were unaffected by the aerobic digestion. Although carbon emission before flooding dramatically increased after biomass application in aerobic decomposition treatments, the mineralized C losses exhibited no differences among treatments. Based on these results, NECB values were similar in all treatments. This implies the aerobic decomposition did not stimulate SOC depletion, compared to the control. Finally, the net GWP highly decreased by 30-86% by the aerobic digestion due to the significant reduction of CH4 emission. In conclusion, earlier application of cover crops before irrigation is a smart strategy to decrease methane emission, maintaining soil carbon sequestration effect of cover crop biomasses application.
Environmental burdens of groundwater extraction for irrigation over an agricultural land in Northwest China
Authors: Niu Jun , Kang Shaozhong
Published: March 2020

Crop production in North China largely depends on irrigation, which is mainly from groundwater in Northwest China. Groundwater abstractions are decreasing the groundwater levels, and threatening the fragile ecological systems of arid regions. Here, we examine the dynamic relations between groundwater level and irrigation water for the last three decades in Heihe River basin in China. The average groundwater decline level, attributed to the irrigation water consumption for the farmland area over the past three decades, was calculated. Moreover, the future possible changes are estimated with different RCP senarios. Effective water-saving measures and strategies are expected to adopt to maintain both groundwater levels and agricultural productivity for the coming decades.
Diversity of Global Change Factors and Tipping Points
Authors: Ryo Masahiro , Rillig Matthias
Published: March 2020

Global change is not only about climate change. Several changes in the Earth System occur concurrently and sequentially, and still, novel factors are being identified as emerging problems such as microplastic pollutants. Global change is diverse; nonetheless, little is known about the role of multiple global change co-occurrences. Can we safely anticipate that the effects of multiple global change factors are independent of each other? Or, should we be concerned about the potential of their synergistic interaction, where the joint effect of multiple factors can be larger than the addition of their single effects?

Our talk focuses on ‘the diversity of global change factors’—How the diversity of global change factors can increase, and how the diversity of global change can affect environmental systems in the context of tipping points. We also show empirical evidence that an increasing number of global change factors can cause abrupt shifts in a soil system (cf. Rillig et al. 2019 in Science). We emphasize the urgent need to investigate the expected roles of an increasing diversity of global change factors as an emerging threat to nature and society.
How to improve 3-m resolution land cover mapping from imperfect 10-m resolution land cover mapping product?
Authors: Dong Runmin , Fu Haohuan
Published: March 2020

Land cover mapping has made drastic progress with the improvement of the resolution of remote sensing images in recent research. However, with various limitations of public land cover datasets, human efforts on interpreting and labelling images still account for a significant part of the total cost. For example, it took 10 months and $1.3 million to label about 160,000 square kilometers in the Chesapeake Bay watershed in the northeastern United States. Therefore, it is significant to consider the human interpreting cost of the large-scale land cover mapping.

 

In this work, we explore a possible solution to achieve 3-m resolution land cover mapping without any human interpretation. This is made possible thanks to a 10-m resolution global land cover map developed for the year of 2017. We propose a complete workflow and a novel deep learning based network to transform the imperfect 10-m resolution land cover map to a preferable 3-m resolution land cover map, which is beneficial to reduce the research thresholds in this community and give similar studies as an example. As we use the imperfect training label, a well-designed and robust approach is strongly needed. We integrate a deep high-resolution network with instance normalization, adaptive histogram equalization, and a pruning process for large-scale land cover mapping.

 

Our proposed approach achieves the overall accuracy (OA) of 86.83% on the test data set for China, improving the previous state-of-the-art accuracies of 10-m resolution land cover mapping product by 5.35% in OA. Moreover, we present detailed results obtained over three mega cities in China as example and demonstrate the effectiveness of our proposed approach for 3-m resolution large-scale land cover mapping.
Intercomparison of atmospheric transport models using 1 km grid meteorological data for the Fukushima Daiichi Nuclear Power Plant Accident
Authors: Yamazawa Hiromi , Sato Yousuke , Sekiyama Tsuyoshi , Kajino Mizuo , Goto Daisuke , Morino Yu , Kondo Hiroaki , Quérel Arnaud , Fang Sheng , Takigawa Masayuki , Terada Hiroaki , Kadowaki Masanao , Uchida Junya
Published: March 2020

  Following the previous atmospheric transport model intercomparison project (MIP2: Sato et al, 2018), a new project of model intercomparison (MIP3) has been conducted in which, out of 12 models in MIP2, 9 models are participating. The main aim of MIP3 is to examine the effects of using a refined meteorological data with a finer horizontal resolution of 1 km (Sekiyama et al., 2019). This paper describes outline of the preliminary results of MIP3.

  The horizontal distribution Cs-137 deposition in the eastern part of Honshu Island (the main island of Japan) calculated by the models were compared with the aerial survey results to find that the simple ensemble average of the 9 models was a little worse than that of the 12-model ensemble in MIP2 in terms of the statistical index RANK, which is the combination of the correlation coefficient, the fractional bias, the figure of merit in space and KPS. This slightly poorer performance is tentatively considered to be caused partially by the absence of three models which showed rather broad deposition patterns and by the underestimation in the Nakadori area (the middle part of Fukushima Pref.). However, in the sector in the northwestern direction from the accidental site which had the largest deposition, the deposition pattern simulated by the MIP3 ensemble, if compared with that of MIP2, is more consistent with the survey result. As for the atmospheric concentrations, although the model performance for the plumes that traveled over wider areas was found to be slightly poorer for MIP3 than MIP2, it was found that the MIP3 ensemble generally showed better performance for the plumes that affected the near area in the Hamadori area (the coastal part of Fukushima Pref.). The better performance of the MIP3 in this area can be attributed to the better representation of topography in the meteorological simulation.
Burrowing fauna mediate alternative stable states in the redox cycling of salt marsh sediments
Authors: van de Velde Sebastiaan , Antler Gilad , Meysman Filip
Published: March 2020

The East Anglian salt marsh system (UK) has recently generated intriguing data with respect to sediment biogeochemistry. Neighbouring ponds in these salt marshes show two distinct regimes of redox cycling: the sediments are either iron-rich and bioturbated, or they are sulphide-rich and unbioturbated. No conclusive explanation has yet been given for this remarkable spatial co-occurrence.  Using pore-water analysis and solid-phase speciation, I will demonstrate that differences in solid-phase carbon and iron inputs are likely small between pond types, so these cannot act as the direct driver of the observed redox dichotomy. Instead, the results suggest that the presence of bioturbation is the driving force behind the transition from sulphur-dominated to iron-dominated sediments. The presence of burrowing fauna in marine sediments stimulates the mineralisation of organic matter, increases the iron cycling and limits the build-up of free sulphide. Subsequent early diagenetic modelling confirms that the observed regimes in pond geochemistry are caused by negligible differences in solid-phase inputs, which are amplified by positive feedbacks resulting from the impact of bioturbation on iron and sulphur cycling.
Electron- and proton-scale nested magnetic cavities: Manifestation of kinetic theta-pinch equilibrium in space plasmas
Authors: Li Jinghuan , Yang Fan , Zhou Xu-Zhi , Zong Qiu-Gang , Artemyev Anton V. , Rankin Robert , Shi Quanqi , Yao Shutao , Liu Han , He Jiansen , Pu Zuyin , Xiao Chijie
Published: March 2020

Magnetic cavities, sometimes referred to as magnetic holes, are ubiquitous in space and astrophysical plasmas characterized by localized regions with depressed magnetic field strength, strongly anisotropic particle distributions, and enhanced plasma pressure. Typical cavity sizes range from fluid to ion and sub-ion kinetic scales, with recent observations also identifying nested cavities that may indicate cross-scale energy cascades. Although heavily investigated in space, magnetic cavities have analogs in laboratory plasmas, the classical theta-pinches. Here, we develop an equilibrium solution of the Vlasov-Maxwell equations in cylindrical coordinates (in similar format to theta-pinch models), to reconstruct the cross-scale profiles of magnetic cavities observed by the four-spacecraft MMS mission. The kinetic model uses input parameters derived from single-spacecraft measurements to successfully reproduce signatures of magnetic cavities from all observing spacecraft. The reconstructed profiles demonstrate that near the electron-scale cavity boundary, the decoupled electron and proton motions generate a radial electric field that contributes to electron vortex formation that has been previously attributed mostly to diamagnetic effects. At larger scales, the diminishing electric field implies that diamagnetic motion is solely responsible for proton vortices.
N2O emission and governing factors on arable fields
Authors: Dencső Márton , Baklanov Szandra , Horel Ágota , Gelybó Györgyi , Tóth Eszter
Published: March 2020

This study focuses on the soil N2O emission of arable fields. We initially set up several soil column experiments in laboratory and based on these findings we started field measurements in a long term tillage experiment at Józsefmajor Experimental and Training Farm, Hungary. For the column experiments we collected undisturbed soil columns (d=10 cm, h=10 cm) from mouldboard ploughing (P) and no-till (NT) treatments.  We investigated the effect of different fertilizer doses (40, 80, 160, 240 kg h-1 N), soil water content (SWC) and different tillage methods on soil N2O emission.

We found a nonlinear response of N2O emission on the applied fertilizer doses. The moderately fertilized (80-160 kg ha-1 N) samples had the highest N2O emissions. Samples from NT had higher N2O emission than samples from P. We found better correlation between N2O emission and SWC in NT (R2 is between 0.47 and 0.62) than in the P (R2 is between 0.01 and 0.35).  The N2O emission values showed high spatial variability. The field measurements showed similar findings of N2O emission compared to the column experiments. In 2020 we intend to continue the field measurements and include further investigations of governing factors of soil N2O emission.
A forensic hydrometeorological and geomorphological reconstruction of the catastrophic flash flood occurred in Mallorca (Spain) on October 9th, 2018
Authors: Amengual Arnau , Lorenzo-Lacruz Jorge , Garcia Celso , Morán Tejeda Enrique , Homar Víctor , Maimó-Far Aina , Hermoso Alejandro , Ramis Climent , Romero Romu
Published: March 2020

An extraordinary convective rainfall event –unforeseen by most numerical weather prediction models– led to a devastating flash flood in the town of Sant Llorenç des Cardassar, eastern Mallorca, on 9th October 2018. Four people died inside the village, while the total death toll was of 13 and economic damages amounted to 91 M€. The observed flooded extension inside the town by the Copernicus Emergency Management Service –based on Sentinel-1 imagery– far exceeded the extension for a 500-year return period flood. This extreme event has been reconstructed by implementing an integrated flood modelling approach over the semi-arid and small-sized Ses Planes basin up to Sant Llorenç (23.4 km²). This procedure is based on three components: (i) generation of high spatial and temporal resolution radar-derived precipitation estimates; (ii) modelling of the hydrologic response based on post-flood peak discharge estimates; and (iii) hydraulic simulation and mapping of the affected areas based on high water marks. Radar-derived rainfall estimates and the simulated flooding extent and water depths highly correlate with observations. The hydraulic simulation has revealed that water reached a depth of 3 m at some points inside Sant Llorenç and that water velocity greatly increased at bridges’ locations close to the town centre. Even if the catastrophic flash flood was not a debris flow, the flood bore eroded enough material to change channel geomorphology. This study also highlights how the concurrence of the very low predictability of this type of extreme convective rainfall events and the very short hydrological response times typical of small Mediterranean catchments still challenges the implementation of early warning systems, which effectively reduce people’s exposure to flash flood risk in the region.
A 3-D geological modeling method and its application to petroleum migration and accumulation simulation
Authors: Guo Qiulin , Wu Na , Liu Jifeng , Chen Ningsheng
Published: March 2020

Besides the carrier bed, faults and unconformities are important migration pathways for the 3-D petroleum migration and accumulation simulation. The fault is often ignored or used only as simulated grid boundaries in the traditional 3-D geological modeling, so that the transport function of faults is neglected or weakened.

In view of the fact that the traditional geological modeling method cannot establish the interrelation of carrier-system (the carrier bed, fault, unconformity, etc.), we propose a hybrid-dimensional mesh modeling technology consisting of body (stratum), surfaces (faults and unconformities), lines and points. The stratum mesh cut by a fault consists of stratum body A, stratum body B and fault surface C. There are two methods: (1) The fault is neglected in the modeling of the geological body, in other words, the mesh form and volume remain unchanged; and (2) The fault is considered in the modeling of the geological body, and the geological body on the two sides of the fault are divided into two parts for modeling. We propose the third processing method. The fault is considered in the modeling of the geological body, and the geological bodies on the two sides of the fault are divided into two parts for modeling, forming stratum meshes. In addition, the fault surface is taken as the third mesh, i.e. surface mesh. At this point, the mesh system is not the original single stratum mesh (3D body mesh) any more, and it also contains the surface mesh (2D surface mesh), therefore it is called a hybrid-dimensional mesh system (hybrid mesh system).

Based on new hybrid-dimensional mesh of the carrier-system, a special 3-D invasion percolation model (3-DIP) is proposed. The fault transport ability can also be determined by shale gouge ratio (SGR) in the 3-DIP model.

The new method is applied to the Luliang uplift in Junggar Basin, China, with an area of 3502 km2. The strata are composed of Permian - Cretaceous, which are divided into 15 simulated layers. Key simulation parameters of the study area include 2884 plane simulation meshes, 59 faults and 1 unconformity. The total number of formed meshes is 54406, including 45972 body meshes, 7884 surface meshes, 549 line meshes and 1 point mesh.

The migration pathway of oil is traced by 3-DIP, and the oil accumulation and wax content of crude oil are simulated. By comparing the simulated wax content with the measured wax content, the results are consistent with each other. It is shown that the model is reliable and the results are credible.

Key words: geological modeling, migration pathway, hybrid mesh, invasion percolation model, petroleum migration and accumulation simulation, Junggar Basin.
Emplacement dynamics of supraglacial rock avalanches: details from the 2016 Lamplugh event, Alaska
Authors: Dufresne Anja , Wolken Gabriel , Hibert Clément , Bessette-Kirton Erin , Coe Jeffrey , Geertsema Marten , Ekström Göran
Published: March 2020

In Glacier Bay Park and Preserve, Alaska, at least 25 rock avalanches occurred since the mid-1980s. The 2016 Lamplugh rock avalanche, with roughly 70 Mm3 deposit volume, is one of the larger events within the park. It originated from a north-facing bedrock ridge without any obvious trigger, and spread 10 km down Lamplugh Glacier. Based on field surveys, high-resolution digital elevation models, and continuous seismic data, we show that the emplacement dynamics of this supraglacial rock avalanche can be described by two distinct stages. Clear long-period seismic signals during Stage-1 record strong interactions of the rock avalanche debris with the ground, suggesting dynamic processes such as grain collisions and fragmentation ('active or dynamic emplacement' of a granular flow). During this first stage, the debris traveled about 5 km from the base of the slope; its deposit is thin and stretched with a dominant dry and flat area in the center, and has narrow raised margins. Stage-2 was essentially aseismic at long periods and dominated by low-friction sliding at slow deceleration rates ('passive sliding'). This sliding produced the distal roughly third of the total runout length where the deposit has a higher density of flowbands and more prominent, raised margins from entrainment and bulldozing of snow. The higher apparent mobility of supraglacial landslides (relative to their counterparts in other runout environments) may be explained by this two-stage model.
On the Origin of Ultramylonites
Authors: Précigout Jacques
Published: March 2020

Deformation of lithospheric rocks regularly localizes into high-strain shear zones that include fine-grained ultramylonites. Occurring as quasi-straight layers of intimately mixed phases that often describe sharp transitions with the host rock, these structures may channelize fluid flow[1,2] and could serve as precursors for deep earthquakes[3]. However, although intensively documented, ultramylonites originate from still unknown processes. Here I focus on a mylonitic complex that includes numerous mantle ultramylonites in the Ronda peridotite (Spain). Among them, I was able to highlight one of their precursors that I better describe as a long and straight grain boundary, along which four-grain junctions are observed with randomly oriented grains of olivine and pyroxenes. This precursor starts from a pyroxene porphyroclast and extends to an incipient, weakly undulated ultramylonite, where intimate phase mixing arises with asymmetrical grain size distribution. While the finer grain size locates on one side, describing a sharp – but continuous – transition with the host rock, the grain size gradually increases towards the other side, giving rise to a smooth transition. All phases have a very weak lattice preferred orientation (LPO) in the ultramylonite, which strongly differs from the host rock where olivine is highly deformed with evidence of high dislocation densities and a strong LPO. Altogether, these features shed light on the origin of mantle ultramylonites that I attribute to a migrating grain boundary, the sliding of which continuously produces new grains by phase nucleation, probably at the favor of transient four-grain junctions. Nucleated grains then grow and progressively detach from the precursor as it keeps on migrating depending on the dislocation densities in the host rock. Although such an unusual grain boundary remains to be understood in terms of source mechanism, these findings provide new constraints on the appearing and development of ultramylonites.

 

[1] Fusseis, F., Regenauer-Lieb, K., Liu, J., Hough, R. M. & De Carlo, F. Creep cavitation can establish a dynamic granular fluid pump in ductile shear zones. Nature 459: 974–977 (2009)

[2] Précigout, J., Prigent, C., Palasse, L. & Pochon, A. Water pumping in mantle shear zones. Nat. commun. 8: 15736, https://doi.org/10.1038/ncomms15736 (2017)

[3] White, J. C. Paradoxical pseudotachylyte – Fault melt outside the seismogenic zone. J. Struct. Geol. 38: 11-20 (2012)
An updated view of Hadley cell expansion from CMIP6 models
Authors: Grise Kevin , Davis Sean
Published: March 2020

            One of the most robust aspects of the atmospheric circulation response to increasing greenhouse gases is the poleward shift in the subsiding branches of the Hadley circulation, potentially pushing subtropical dry zones poleward toward midlatitudes.  Numerous lines of observational evidence suggest that this tropical expansion may have already begun.  Yet, the degree to which the observed tropical widening is anthropogenically forced has remained a topic of great debate, as previous studies have attributed the recent circulation trends to some combination of increasing greenhouse gases, stratospheric ozone depletion, anthropogenic aerosols, and natural variability.  During the past few years, two international working groups have synthesized recent findings about the magnitude and causes of the observed tropical widening, primarily using output from global climate models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5).  In this presentation, we update those findings using the recently released CMIP6 global climate models.

            Over recent decades, the poleward expansion of the Hadley circulation estimated from modern reanalyses is relatively modest (< 0.5 degrees latitude per decade).  The reanalysis trends have similar magnitudes in the annual mean in the Northern Hemisphere (NH) and Southern Hemisphere (SH), but both CMIP5 and CMIP6 models suggest that increasing greenhouse gases should drive 2–3 times larger circulation shifts in the SH.  The reanalysis trends fall within the bounds of the models’ simulations of the late 20th century and early 21st century, although prescribing observed coupled atmosphere-ocean variability allows the models to better capture the observed trends in the NH.  We find two notable differences between CMIP5 and CMIP6 models.  First, both CMIP5 and CMIP6 models contract the NH summertime Hadley circulation equatorward (particularly over the Pacific sector) in response to increasing greenhouse gases, but this contraction is larger in CMIP6 models due to their higher average climate sensitivity.  Second, in recent decades, the poleward shift of the NH annual-mean Hadley cell edge is slightly larger in the historical runs of CMIP6 models.  Increasing greenhouse gases drive similar trends in CMIP5 and CMIP6 models, so CMIP6 models imply a stronger role for other forcings (such as aerosols) in recent circulation trends than CMIP5 models.
The architecture and the multi-stage evolution of the North Iberian margin (Bay of Biscay)
Authors: Cadenas Patricia , Manatschal Gianreto , Fernández-Viejo Gabriela
Published: March 2020

In this work, we address the problem of the formation and reactivation of multi-stage rifting based on the study of the central North Iberian margin, located at the southern Bay of Biscay triangular oceanic domain. This magma-poor rifted margin registered three major Mesozoic rift events and a subsequent Alpine compressional reactivation, representing a unique setting to study the architecture of a multi-stage rift system and its control on subsequent reactivation. Based on a dense dataset of high quality 2D seismic reflection profiles, boreholes and published velocity models, we define, describe and map structural domains, major extensional and compressional structures, and the depth and thickness of syn-rift units. We provide new structural maps showing the geometry and spatial distribution of major rift basins and bounding structures.

The analysis of the tectono-stratigraphic architecture led us to define three rift systems. A diffuse and widespread of Triassic age, with classical fault-bounded half-graben basins, a second, narrow, deep and localised Late Jurassic to Barremian transtensional system, and a third, widely distributed Aptian to Cenomanian hyperextended system, including two distinctive domains. Our results show that each rift system controlled successive rift events, and that the stacking and overlap of the three rift systems resulted in a complex and segmented 3D template that guided subsequent compressional reactivation. Compression affected on a distinctive way the three rift systems, leading to an amplification of the margin segmentation.

This work shows that unravelling the tectono-stratigraphic architecture and evolution of multi-stage rift systems can provide key insights not only to decipher the spatial and temporal evolution of divergent plate boundaries, but also to set up present-day kinematic templates to test dynamic plate deformable models of conjugate rifted margins. It will also be a keystone to constrain early stages of margin reactivation and the architecture of reactivated rifted margins now incorporated in orogenic systems.
Conservation tillage positively influences soil organic carbon through earthworm excrement physical structure stability in a Chinese Mollisoil
Authors: Chen Xuewen , Liang Aizhen , Wu Donghui , Jia Shuxia , Zhang Yan
Published: March 2020

Identifying the relationship between earthworm activity and soil organic carbon is vital for both planning and performing farming operations. Numerous studies have emphasized that earthworms affect soil organic carbon greatly. However, the extent of this effect is still somewhat vague, and very little is known, not to mention the role of earthworm excrement. The objective for this study is to determine the effect of earthworm excrement on soil organic carbon following different tillage practices based on physical structure stability parameters. Both no tillage (NT) and ridge tillage (RT) led to significant total pore surface area, permeability, fluid conductivity, water resistance index and tensile strength increment than moldboard plow (MP) (p<0.05), whereas water repellency significant decrement (p<0.05). Similar to soil organic carbon, NT and RT significantly increase organic carbon in earthworm excrement than MP (p<0.05). A significant positive correlation (p<0.05) was found between organic carbon in earthworm excrement and total pore surface area, water repellency, tensile strength, respectively. This finding demonstrates that conservation tillage increase organic carbon in earthworm excrement through physical structure stability namely aggregation effect of earthworm excrement on soil water movement and gas diffusion, potentially important for the soil organic carbon increment.
The influence of synoptic weather patterns in supercell formation in Spain
Authors: Calvo-Sancho Carlos , Martín Yago
Published: March 2020

Supercells are the most organized and complex type of thunderstorms. Their formation, among other factors, is greatly influenced by general synoptic weather conditions. The goal of the study is to analyze the effect of different circulation weather types (CWT) in supercell formation and their spatiotemporal patterns in Spain. We use 2014-2018 data from the Spanish Supercell Database from the weather online network Tiempo.com (Martín et al., 2019) and compute 12 different CWTs through a Principal Component Analysis (PCA) of the 6-hour average of the 500hPa atmospheric pressure variable from the National Center for Environmental Prediction (NCEP) Reanalysis database. Results indicate that supercells are more common in three CWTs related with short-wave troughs over the Iberian Peninsula, particularly in the period from May to September. In these three CWTs the spatial distribution mainly concentrates in northeastern Spain, particularly in the Middle Ebro Valley (MEV) and the easternmost part of the Iberian System.
Evaluation of WRF coupled with Noah using an improved albedo parameterization scheme during a severe snow event over the Tibetan Plateau
Authors: Liu Lian , Menenti Massimo , Ma Yaoming , Ma Weiqiang
Published: March 2020

Snow falls frequently over the Tibetan Plateau, and is a vital component of the widespread cryosphere which has vital feedback to climate change. Snowfall and the subsequent evolution of the snowpack have a large effect on surface energy balance and water cycle. Albedo, the main determinant of net radiation flux, is a major driver of land surface processes. However, the current widely used Noah land surface model does not describe snow albedo correctly, although it keeps snow-related variables i.e. snow cover and age into account. In our study, the impact of an improved albedo parameterization scheme in WRF coupled with Noah was investigated. In the improved albedo scheme, albedo was parameterized as functions of snow depth and age which was developed using remote sensing retrievals of albedo. Numerical experiments were conducted to model a severe snow event in March 2017. The performance of WRF coupled with Noah applying the improved albedo scheme was compared with that of applying the default albedo scheme and with that of WRF coupled with CLM applying CLM’s complex albedo scheme. First, the improved albedo scheme largely reduces the WRF coupled with Noah albedo overestimation in the southeastern Tibetan Plateau, remarkably reducing the large cold bias estimates by 0.7 ℃ air temperature RMSE. Second, the improved albedo scheme gives the highest correlationship between the satellite-derived and the model estimated albedo, contributing to achieve the SWE spatial pattern, heavy snow belt and maximum SWE estimates in eastern Tibetan Plateau. Remarkable underestimation of albedo in WRF coupled with CLM contributes to regional maximum SWE underestimation and failure in heavy snow belt estimates.

In addition, WRF default land cover and green vegetation fraction were out of date but played a large impact on estimates of air temperature, albedo and SWE. Updated land parameters led to improve the model performance in simulating the severe snow event, by reducing albedo RMSE by 1%-4%. The choice of the algorithm to retrieve green vegetation fraction had a large impact on the accuracy of green vegetation fraction retrievals. It remains open to debate the optimal algorithm to estimate land surface properties in the complex topographic Tibetan Plateau.
Roles of electrons and ions in formation of the current in mirror mode structures in the terrestrial plasma sheet: MMS observations
Authors: Wang Guoqiang , Zhang Tielong , Wu Mingyu , Schmid Daniel , Hao Yufei , Pan Zonghao , Volwerk Martin
Published: March 2020

Currents are believed to exist in mirror mode structures and to be self-consistent with the magnetic field depression. Here, we investigate a train of mirror mode structures in the terrestrial plasma sheet on 11 August 2017 measured by the Magnetospheric Multiscale mission. We find that bipolar current densities exist in the cross-section of two hole-like mirror mode structures, referred to as magnetic dips. The bipolar current in the magnetic dip with a size of ~2.2 ρi (the ion gyro radius) is mainly contributed by variations of the electron velocity, which is mainly formed by the magnetic gradient-curvature drift. For another magnetic dip with a size of ~6.6 ρi, the bipolar current is mainly caused by an ion bipolar velocity, which can be explained by the collective behaviors of the ion drift motions. These observations suggest that the electrons and ions play different roles in the formation of currents in magnetic dips with different sizes.
Radial Evolution of Coronal Mass Ejections in the Inner Heliosphere: Catalog and Analysis
Authors: Salman Tarik , Winslow Reka , Lugaz Noé
Published: March 2020

Our knowledge of the properties of Coronal Mass Ejections (CMEs) in the inner heliosphere is constrained by the relative lack of plasma observations between the Sun and 1 AU. In this work, we present a comprehensive catalog of 47 CMEs measured in situ measurements by two or more radially aligned spacecraft (MESSENGER, Venus Express, STEREO, and Wind/ACE). We estimate the CME impact speeds at Mercury and Venus using a drag-based model and present an average propagation profile of CMEs (speed and deceleration/acceleration) in the inner heliosphere. We find that CME deceleration continues past Mercury's orbit but most of the deceleration occurs between the Sun and Mercury. We examine the exponential decrease of the maximum magnetic field strength in the CME with heliocentric distance using two approaches: a modified statistical method and analysis from individual conjunction events. Findings from both the approaches are on average consistent with previous studies but show significant event-to-event variability. We also find the expansion of the CME sheath to be well fit by a linear function. However, we observe the average sheath duration and its increase to be fairly independent of the initial CME speed, contradicting commonly held knowledge that slower CMEs drive larger sheaths. We also present an analysis of the 3 November 2011 CME observed in a longitudinal conjunction between MESSENGER, Venus Express, and STEREO-B focusing on the expansion of the CME and its correlation with the exponential fall-off of the maximum magnetic field strength in the ejecta.
An improved extraction method of 3-oh fatty acids for environmental reconstruction
Authors: Panbut Chanamon
Published: March 2020

3-hydroxy or beta-hydroxy fatty acids produced by Gram-negative bacteria are a novel proxy for assessment of the environmental changes. These compounds composed of lipopolysaccharide (LPS) of Lipid A, a core polysaccharide region, and an O-antigen polysaccharide chain. The improved method for the 3-hydroxy fatty acids extraction was proposed in this study. The 12 soil samples collected from the eastern US border along the coastline from Maine to Florida were generally processed by acid hydrolysis, methylation, total lipid extraction, and solid-phase chromatography, respectively. Fatty acids eventually can be separated from the main part of LPS and combined with a methyl group. However, in the stage of acid hydrolysis, the temperature was decreased to 55 °C, and heating time was extended in order to prevent the broken of volatile compounds and diminish the relative abundance of 3-OH fatty acids. The higher abundance of interested 3-OH fatty acids for the environmental reconstruction can potentially be extracted by this improvement than the classical protocol. This research will be further compared in terms of cost, experimental time and completeness of data between these two methods.