bluuebunny/crossref_metadata_2025 huggingface dataset:
The Zagros Suture Amphibolites Record the Cretaceous Thermal Evolution of the Closing Tethyan Realm
Authors: Holtmann Regina , Muñoz-Montecinos Jesus , Angiboust Samuel , Cambeses Aitor , Bonnet Guillaume , Glodny Johannes , Gharamohammadi Zeynab , Kananian Ali , Agard Philippe
Published: March 2021

A Cretaceous paleo-accretionary wedge (the Ashin Complex) now exposed along the Zagros suture zone in southern Iran exhibits mafic and metapelitic lithologies. Field, geochemical and petrological observations point to a high-temperature event that gave rise to the formation of peritectic (trondhjemitic) melts associated with restitic garnet-bearing amphibolites in the structurally highest sliver of the Ashin Complex. SHRIMP U-Pb zircon dating of grains crystallized in trondhjemitic leucosomes yields a 206Pb/238U weighted mean age of 104 ±1 Ma, interpreted as the peak temperature event, which occurred in the amphibolite facies (c. 640-650°C at 1.1-1.3 GPa), based on thermodynamic modeling. Rutile crystals from several leucosomes yield Zr-in-rutile temperatures between 580-640°C and LA-ICP-MS U/Pb ages of 87-94 Ma. This rutile generation may be related to the observed static formation of Na-clinopyroxene and Si-rich phengite rims, as well as the growth of lawsonite in late fractures. The latter paragenetic sequence has been previously interpreted as reflecting a long-term isobaric cooling that occurred at least until the end of the Cretaceous (ages in Angiboust et al., 2016).

While the latter observations point to a long-term cooling of the Zagros subduction thermal gradient down to 7°C/km during late Cretaceous times, this first report of an earlier melting event in the Zagros paleo-accretionary wedge indicates an abnormally high thermal gradient of 17-20°C/km. GPLATES paleogeographic reconstructions of the Tethyan realm evolution during Cretaceous times reveal the presence of a spreading ridge jump followed by the subduction of the formerly active ridge-segment between 105-115 Ma, which possibly left an imprint marked by the unusually hot gradient seen in Ashin amphibolites. The model further predicts the subduction of progressively aging oceanic lithosphere, possibly explaining the observed cooling of the subduction thermal regime.
15-year-long Adriatic hindcast: Sensitivity to atmospheric forcing
Authors: Vodopivec Martin , Peliz Álvaro
Published: March 2021

The Adriatic basin is narrow and elongated with numerous islands and surrounded in many parts by steep orography. Therefore ocean models of the Adriatic Sea should benefit from high-resolution atmospheric forcing that could properly account for orographic variations. We compare the results of long-term hindcasts obtained by using three different atmospheric reanalyses with different spatial resolutions. The CROCO ocean model (formerly ROMS_AGRIF) was configured on a relatively coarse 4 km grid, which we consider fine enough to observe the effects of different forcing resolutions, but still coarse enough that we were able to run multiple simulations in a manageable time. Initial and open boundary conditions were provided by CMEMS Mediterranean Sea Physics Reanalysis, and the model includes 36 freshwater sources. A thorough analysis of several run configurations revealed that spatial resolution should not be the primary criteria in choosing the right forcing, as atmospheric models can be subject to significant biases. These tend to strongly influence the results and sometimes even cause circulation reversals. Here we present the main differences between the runs and also evaluate each of them by comparing the results with satellite observations of sea surface temperature.
Measuring snowfall properties with the Video In Situ Snowfall Sensor during MOSAiC
Authors: Maahn Maximilian , Radenz Martin , Cox Christopher , Gallagher Michael , Hutchings Jennifer , Shupe Matthew , Uttal Taneil
Published: March 2021

Snow is an essential component of the climate system impacting surface albedo, glaciers, sea ice, freshwater storage, and cloud lifetime. Even though we do not know the exact pathways through which ice, liquid, cloud dynamics, and aerosols are interacting in clouds while forming snowfall, the involved processes can be identified by their fingerprints on snow particles. The general shape of individual crystals (dendritic, columns, plates) depends on the temperature and moisture conditions during growth from water vapor deposition. Aggregation can be identified when multiple individual particles are combined into a snowflake. Riming describes the freezing of cloud droplets onto the snow particle and can eventually form graupel. In order to exploit these unique fingerprints of cloud microphysical processes, optical observations are required.

The Video In Situ Snowfall Sensor (VISSS) was specifically developed for the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign to determine particle shape and particle size distributions. Different to other sensors, the VISSS minimizes uncertainties by combining two-dimensional high-resolution images with a large measurement volume and a design limiting the impact of wind. Here, we show first results from the MOSAiC campaign and present examples for synergy effects that can be obtained by combining radar and VISSS measurements.
Tropical Cyclone Potential Intensity during the Record-Breaking 2020 Hurricane Season
Authors: Gilford Daniel
Published: March 2021

The 2020 Atlantic hurricane season broke records, including becoming the most active tropical cyclone season (30 named storms), having the latest-named category five hurricane (Iota), and recording the most hurricane landfalls (twelve) in US history. This extraordinary activity yields an unusually large set of observed tropical cyclone (TC) intensities for a single season, which may be studied with theoretical and statistical analyses---something which is typically untenable for an average season. A tool to analyze these 2020 hurricane intensities is potential intensity (PI), which is the theoretical maximum speed limit of a tropical cyclone found by treating the storm as a thermal heat engine. From this thermodynamic perspective, was the 2020 hurricane season unprecedented? We explore this question using pyPI: a new python package which rapidly and transparently calculates potential intensity given a set of environmental conditions (https://github.com/dgilford/tcpyPI). Using reanalyses data, we rank 2020 potential intensity among all previous hurricane seasons (in the satellite era) and consider what environmental conditions made 2020 unique. The high number of observed storms allows us to build on previous work and perform a statistical analysis, which assesses the viability and value of potential intensity theory during the 2020 hurricane season. In particular, we calculate the normalized wind along the track of each storm (observed maximum intensity divided by potential intensity), which generally shows a uniform probability distribution function. The uniform shape of this distribution suggests that potential intensity theory is viable for seasonal intensity forecasting as long as storm counts are sufficiently high. In seasons with at least 25 storms one may expect that ~10% of the most intense observed hurricanes storms will have observed maximum intensities within 10% of their along-track potential intensity. Finally, we discuss how this approach and software could be improved/adapted for operational applications, and ask for feedback from the broader tropical cyclone community.
Mercury background monitoring in the Lake Baikal region
Authors: Pankratov Fidel , Mahura Alexander , Popov Valentin , Masloboev Vladimir
Published: March 2021

During 2013-2015 the gaseous elemental mercury (thereafter, mercury) measurements were carried out at two weather monitoring stations/sites (Listvyanka – from 25 July until 19 November 2013 and Tankhoj – from 27 July 2014 until 11 January 2015). The mercury analyzer Lumex RA-915AM was used for measurements. Although in the Northern Hemisphere the minimal average mercury concentration is about 1.5 ng m-3, the obtained results indicated that in the southern part of the Lake Baikal the lowest average concentration was about 1.18 ng m-3. Thus, the natural reserve territory of the Lake Baikal can be used as the main region to the background level of especially clean areas for monitoring heavy metals and persistent organic pollutants.

For the Listvyanka measurements, the mercury analyzer was installed at 20 m distance from a shore of the lake. During July-November 2013, the average concentration value was about 1.41±0.37 ng m-3 (with max - 4.81, min - 0.16). For the July-August period, the maximum variance distribution was estimates as 0.62 ng m-3. For the August-November period, the variance did not exceed the value of 0.38 ng m-3. Mercury from the atmosphere is deposited on the underlying surface, and with increasing intensity of total solar radiation the re-emission of mercury occurred resulting in increased concentrations of mercury at Listvyanka. A rather low mercury values were recorded during October-November 2013. Analysis of atmospheric transport during summer showed, that main sources of pollution are situated to the west of the lake, and it is a relatively larger area in the southwestern sector, and therefore, it is complex to identify exact locations of such pollution sources.

For the Tankhoj site, in July 2014 the mercury analyzer was installed at about 100 m distance from a shore of the lake. It was for the first time, when the mercury monitoring was conducted for such long-term period of time in the Lake Baikal region. Note, that short-term measurements of mercury do not provide full understanding of the background level mercury and are insufficient to study dynamics. Analysis of obtained time-series showed that summer is characterized by a high variability of mercury (max - 2.86, min - 0.27, with an average 1.19±0.27 ng m-3). In particular, in July an average value of 1.18 ng m-3 (max - 2.68, min - 0.43) was obtained, which corresponds to concentrations observed in the Northern Hemisphere. In August the average value of 1.22 ng m-3 (max - 2.86, min - 0.27) was obtained.

Moreover, obtained results showed that location of the Tankhoj monitoring site can be used for long-term background monitoring of mercury.
Giving Facts a fighting chance against misinformation
Authors: Winkler Bärbel , Cook John
Published: March 2021

Skeptical Science is a volunteer-run website publishing refutations of climate misinformation. Some members of the Skeptical Science team actively research best-practices refutation techniques while other team members use the provided materials to share debunking techniques effectively either in writing or through presentations. In this submission, we highlight several of our publications and projects, designed to help to give facts a fighting chance against misinformation. While some of the resources are nominally related to climate change, the underlying techniques apply across different topics. Resources include the Massive Open Online Course (MOOC) “Denial101x - Making sense of Climate Science Denial” co-produced with the University of Queensland in 2015, the “FLICC-framework” explaining the taxonomy of science denial with its five main techniques (fake experts, logical fallacies, impossible expectations, cherry picking, and conspiracy theories), the Debunking Handbook 2020 which summarizes research findings and expert advice about debunking misinformation, and the Conspiracy Theory Handbook distilling research findings and expert advice on dealing with conspiracy theories. We will also introduce the Cranky Uncle smartphone game, using critical thinking, gamification, and cartoons to interactively explain science denial techniques and build resilience against misinformation.
Parameters controlling the substorm onset location
Authors: Elhawary Reham , Laundal Karl , Reistad Jone , Ohma Anders , Hatch Spencer , Madelaire Michael
Published: March 2021

Substorm onset location varies over a range of magnetic local time (MLT) and magnetic latitudes (MLat). It is well known that about 5% of the variation in onset MLT can be explained by variations in interplanetary magnetic field orientation and dipole tilt angle. Both parameters introduce an azimuthal component in the magnetic field in the magnetosphere such that the projection of the onset MLT in the ionosphere is shifted. The MLT of the onset near the magnetopsheric equatorial plane is even less predictable. Recent studies have suggested that gradients in the ionospheric Hall conductance lead to a duskward shift of tail dynamics, which could also influence the location of substorm onset. Our goal is to test these ideas by quantifying the dependence of the spatial variation of the onset location on external and internal conditions. We focus on the correlation between the substorm onset location with conditions prior to the onset, such as the interplanetary magnetic field By component, dipole tilt angle, and estimates of the Hall conductance. Linear regression analysis is used to determine the substorm onset location dependence on the proposed variables.
Uncertainties Analysis of Electrical Resistivity Tomography
Authors: Doyoro Yonatan Garkebo , Ping-Yu Chang , Puntu Jordi Mahardika
Published: March 2021

We examined the uncertainty of the resistivity method in cavity studies using a synthetic cavity model set at six-different depths. Conceptual models were simulated to generate synthetic resistivity data for dipole-dipole, pole-dipole, Wenner-Schlumberger, and pole-pole arrays. The 2D geoelectric models were recovered from the inversion of the synthetically measured resistivity data. The highest anomaly effect (1.46) and variance (24400) in resistivity data were recovered by dipole-dipole array, while the pole-pole array obtained the lowest anomaly effect (0.60) and variance (2401) for the target cavity T1. The anomaly effect and variance were linearly associated with the quality of the inverted models. The steeper anomaly gradient of resistivity indicated more distinct cavity boundaries, while the gentler gradient prevents the inference of the cavity boundaries. The recovered model zone above the depth of investigation index of 0.1 has shown relatively higher sensitivity. Modeling for dipole-dipole array provided the highest model resolution and anomaly gradient that shows a relatively distinct geometry of the cavity anomalies. On the contrary, the pole-dipole and Wenner-Schlumberger arrays recovered good model resolutions and moderate anomaly gradient but determining the anomaly geometries is relatively challenging. Whereas, the pole-pole array depicted the lowest model resolution and anomaly gradient with less clear geometry of the cavity anomalies. At deeper depths, the inverted models showed a reduction in model resolutions, overestimation in anomaly sizes, and deviation in anomaly positions, which can create ambiguity in resistivity model interpretations. Despite these uncertainties, our modeling specified that the 2D resistivity imaging is a potential technique to study subsurface cavities.
Miniature tropics and bi-diurnal oscillations
Authors: Haerter Jan O. , Jensen Gorm Gruner , Fiévet Romain
Published: March 2021

Convective self-aggregation is a well-studied atmospheric state, obtained in typically multi-week idealized numerical experiments, where boundary conditions are constant and spatially homogeneous. As radiative convective equilibrium is approached, the atmosphere develops a heavily precipitating moist patch, which is surrounded by subsiding, cloud-free regions. It was recently shown that a homogeneous, but temporally oscillating surface temperature can quickly lead to the emergence of so-called mesoscale convective systems (MCS, diameters of >100 km) - on temporal scales of only a few days. Furthermore, the patterns formed by these MCS remind of checkerboards, and alternate from day to day [1]. 

We here extend this finding further, to add realism to the otherwise preserved idealization: Mimicking a form of “miniature tropics” we retain a laterally periodic domain (Lx, Ly), but impose spatial variation in mean surface temperature along one dimension - reminiscent of a meridional reduction in mean surface temperature, when moving poleward from the equator. By making the wavelength of spatial variation commensurate with domain size, we retail double-periodic lateral boundary conditions. When the diurnal cycle is set to zero, the system quickly organizes to a forcefully aggregated caricature of the actual tropics - with heavy convection near the equator and pronounced subsidence and enhanced long-wave cooling in the subtropics. When the diurnal cycle is increased, bi-diurnal temporal oscillations appear, which lead to a single precipitation peak centered on the equator on one day, but a bimodal meridional pattern with precipitation away from the equator on the next.

Our findings, obtained for a still idealized numerical experiment, may have implications for “edge intensifications” suggested from observations and numerical modeling of tropical precipitation patterns near the ITCZ [2,3].

[1] Haerter, J.O., Meyer, B. & Nissen, S.B. Diurnal self-aggregation. npj Clim Atmos Sci 3, 30 (2020). https://doi.org/10.1038/s41612-020-00132-z

[2] Mapes, B. E., E.-S. Chung, W. M. Hannah, H. Masunaga, A. J. Wimmers and C. S. Velden, 2018: The meandering margin of the meteorological moist Tropics, Geophys. Res. Lett., 45, 1177-1184. doi:10.1002/2017GL076440

[3] Windmiller, J. M., & Hohenegger, C. 2019: Convection on the edge. J. Adv. Model. Earth Syst., 11, 3959-3972, 10.1029/2019MS001820
Climate change attribution with large ensembles
Authors: Kirchmeier-Young Megan , Zhang Xuebin , Wan Hui
Published: March 2021

The large sample sizes from single-model large ensembles are beneficial for a robust attribution of climate changes to anthropogenic forcing. This presentation will review examples using large ensembles in two types of attribution:  standard detection and attribution of spatio-temporal changes and extreme event attribution. First, increases in extreme precipitation have been attributed to anthropogenic forcing at large scales (global and hemispheric). We present results from a study that used three large ensembles, including two Earth System Models and one Regional Climate Model, to find a robust detection of a combined anthropogenic and natural forcing signal in the intensification of extreme precipitation at the continental scale and some regional scales in North America. Second, we use six large ensembles to assess the robustness of the attribution of extreme temperature and precipitation events. An event attribution framework is used and each large ensemble is treated as a perfect model. Robustness of the attribution is defined based on consistent agreement between the different models on a significant change in the probability of an event with the inclusion of anthropogenic forcing. We demonstrate that the attribution of extreme temperature events is robust. Meanwhile, the attribution of extreme precipitation events becomes robust in many regions under additional warming, but uncertainties pertaining to changes in atmospheric dynamics hinder attribution confidence in other regions. We also demonstrate that smaller ensembles bring larger uncertainty to event attribution.
RHEA: A verified simulator for hydro-geomechanical heterogeneity
Authors: Bastias Jose , Rau Gabriel , Wilkins Andy , Blum Philipp
Published: March 2021

Realistic modelling of tightly coupled hydro-geomechanical processes is relevant for the assessment of many hydrological and geotechnical applications. Such processes occur in geological formations and are influenced by natural heterogeneities. Current numerical libraries offer capabilities and physics coupling, that have proven to be valuable in simulating various applications in geotechnical fields such as underground gas storage, rock fracturing, land subsidence and Earth resources extraction. However, implementation and verification of full heterogeneity of subsurface properties using high resolution field data in coupled simulations has not been done yet. Hence, we develop, verify and document RHEA (Real HEterogeneity App), an open-source fully coupled finite element application capable of including node-resolution hydro-geomechanical properties in coupled simulations. We propose a simple, yet powerful workflow to allow the integration of fully distributed hydro-geomechanical properties. We then verify the code with analytical solutions in one and two dimensions and propose a benchmark semi-analytical problem to verify heterogeneous systems with sharp gradients. Finally, we exemplify RHEA's capabilities with a comprehensive example integrating realistic properties. With this we demonstrate that RHEA is a verified open-source application able to integrate complex geology to perform scalable fully coupled hydro-geomechanical simulations. Our work is a valuable tool to assess real world hydro-geomechanical challenging systems that may include different levels of complexity like heterogeneous geology with several time and spatial scales and sharp gradients produced by contrasting subsurface properties.
Stability of the global climate system against strong perturbations
Authors: Loskutov Evgeny , Vdovin Valery , Gavrilov Andrey , Mukhin Dmitry , Feigin Alexander
Published: March 2021

The global climate system is an aggregate of a huge number of interacting components, each having an intrinsic time scale. Such a complex dynamical system demonstrates nontrivial behavior and can exhibit a variety of possible modes of evolution. Gradual change of the parameters of the global climate system can lead to transitions (e.g., the Mid-Pleistocene Transition or to abrupt climate changes) from the observed to a new mode.
In this work, we investigate the stability of the global climate system against strong sudden perturbations in the last 2.5 million years. This case is fundamentally different from the small perturbations case: in particularly, the system response cannot be described by a linearized evolution operator. To estimate the climate system’s nonlinear stability during the last 2.5 million years, we use a nonlinear data-driven model of climate dynamics in Pleistocene [1] and basin stability criterion [2]. Our results indicate that the stabilityof the Pleistocene climate to large perturbations decreases with time: past climates being much more stable compared to the present one.
This work was supported by RFBR grant 19-02-00502.

1. D. Mukhin, A. Gavrilov, E. Loskutov, J. Kurths, A. Feigin. “Bayesian Data Analysis for Revealing Causes of the Middle Pleistocene Transition”. ScientificReports, 9 7328 (2019).
2. V. Klinshov, S. Kirillov, J. Kurths, V. Nekorkin. “Interval stability for complex systems”. New Journal of Physics, v. 20, p. 043040.
Subsurface heterogeneity patterns that emerge from interacting depositional processes
Authors: Willis Brian , Sun Tao
Published: March 2021

Emergent structures define organizational patterns that spontaneously develop due to interactions between component properties or behaviors of complex dynamic systems, rather than being a simple compilation of the individual parts observed within the system at any one time. Traditional facies models used to predict subsurface lithic variations focus on defining the distribution of depositional environments on Earth’s surface and relating the hierarchy of preserved bedding units to different scales of surficial bedforms. It is increasingly recognized that such static models fail to predict the geometry and character of many types of preserved lithic bodies and discontinuity surfaces unless these observations are placed within the context of the overall evolving system. Numerical depositional process models are presented to show links between evolving depositional patterns and preserved facies patterns within different settings.

     Channel deposit internal variations tend not to be channel shaped, but rather sweet spots within the deposit resemble a string of beads, each formed as individual channel segments meander. Mouth bar deposits generally do not to have the circular to elliptical shape of a modern channel-mouth bedform, but rather tend to be more elongate fingers cut by a diachronous channel filled as river flows are choked off by loss of gradient during progradation. Although the final channel basal erosion surface appears continuous, timelines cross this surface along the length of the deposit. Deltaic shorelines that look identical at a given time preserve very different deposits when the feeding river avulses at different frequency, a condition that can change within an individual deposit formed alternately during periods of sea level rise and fall. Even major stratigraphic surfaces, like lowstand fluvial incision surfaces and wave-ravined falling stage and transgressive surfaces, are likely to gradually emerge from the migration of localized areas of erosion that were never as extensive at any one time as the preserved surface. Such surfaces may be regionally diachronous, with deposits of the same age locally preserved variably above and below the surface. Understanding emergent lithic bodies and internal heterogeneity patterns are fundamental to understanding how deposition is recorded in the rock record and for facies models used to predict how subsurface fluids move through shallow marine deposits.
Recent developments on the Earth System Model Evaluation Tool
Authors: Andela Bouwe , Alidoost Fakhereh , Brunner Lukas , Camphuijsen Jaro , Crezee Bas , Drost Niels , Gier Bettina , Hassler Birgit , Kalverla Peter , Lauer Axel , Loosveldt-Tomas Saskia , Lorenz Ruth , Predoi Valeriu , Righi Mattia , Schlund Manuel , Smeets Stef , Vegas-Regidor Javier , Von Hardenberg Jost , Weigel Katja , Zimmermann Klaus
Published: March 2021

The Earth System Model Evaluation Tool (ESMValTool) is a free and open-source community diagnostic and performance metrics tool for the evaluation of Earth system models such as those participating in the Coupled Model Intercomparison Project (CMIP). Version 2 of the tool (Righi et al. 2020, www.esmvaltool.org) features a brand new design composed of a core that finds and processes data according to a ‘recipe’ and an extensive collection of ready-to-use recipes and associated diagnostic codes for reproducing results from published papers. Development and discussion of the tool (mostly) takes place in public on https://github.com/esmvalgroup and anyone with an interest in climate model evaluation is welcome to join there.

 

Since the initial release of version 2 in the summer of 2020, many improvements have been made to the tool. It is now more user friendly with extensive documentation available on docs.esmvaltool.org and a step by step online tutorial. Regular releases, currently planned three times a year, ensure that recent contributions become available quickly while still ensuring a high level of quality control. The tool can be installed from conda, but portable docker and singularity containers are also available.

 

Recent new features include a more user-friendly command-line interface, citation information per figure including CMIP6 data citation using ES-DOC, more and faster preprocessor functions that require less memory, automatic corrections for a larger number of CMIP6 datasets, support for more observational and reanalysis datasets, and more recipes and diagnostics.

 

The tool is now also more reliable, with improved automated testing through more unit tests for the core, as well as a recipe testing service running at DKRZ for testing the scientific recipes and diagnostics that are bundled into the tool. The community maintaining and developing the tool is growing, making the project less dependent on individual contributors. There are now technical and scientific review teams that review new contributions for technical quality and scientific correctness and relevance respectively, two new principal investigators for generating a larger support base in the community, and a newly created user engagement team that is taking care of improving the overall user experience.
Deep Learning for Autonomous Extraction of Millimeter-scale Deformation in InSAR Time Series
Authors: Rouet-Leduc Bertrand , Jolivet Romain , Dalaison Manon , Johnson Paul , Hulbert Claudia
Published: March 2021

Systematically characterizing slip behaviours on active faults is key to unraveling the physics of tectonic faulting and the interplay between slow and fast earthquakes. Interferometric Synthetic Aperture Radar (InSAR), by enabling measurement of ground deformation at a global scale every few days, may hold the key to those interactions. 
However, atmospheric propagation delays often exceed ground deformation of interest despite state-of-the art processing, and thus InSAR analysis requires expert interpretation and a priori knowledge of fault systems, precluding global investigations of deformation dynamics. 
We show that a deep auto-encoder architecture tailored to untangle ground deformation from noise in InSAR time series autonomously extracts deformation signals, without prior knowledge of a fault's location or slip behaviour.
Applied to InSAR data over the North Anatolian Fault, our method reaches  2 mm detection, revealing a slow earthquake twice as extensive as previously recognized.
We further explore the generalization of our approach to inflation/deflation-induced deformation, applying the same methodology to the geothermal field of Coso, California. 
Development and Validation of CME Arrival-Time Forecasting System by MHD Simulations based on Interplanetary Scintillation Observations
Authors: Iwai Kazumasa , Shiota Daikou , Tokumaru Munetoshi , Fujiki Ken’ichi , Den Mitsue , Kubo Yûki
Published: March 2021

Coronal mass ejections (CMEs) cause various disturbances of the space environment; therefore, forecasting their arrival time is very important. However, forecasting accuracy is hindered by limited CME observations in interplanetary space. This study developed a CME arrival-time forecasting system using a three-dimensional (3D) magnetohydrodynamic (MHD) simulations based on interplanetary scintillation (IPS) observations. The base MHD simulation is SUSANO-CME (Shiota and Kataoka 2016), in which CMEs are approximated as spheromaks. In the developed forecasting system, many MHD simulations with different CME initial speed are tested. The IPS responses of each MHD simulation run is calculated from the density distributions derived from the MHD simulation, and compared with IPS data observed by the Institute for Space-Earth Environmental Research (ISEE), Nagoya University. The CME arrival time of the simulation run that most closely agrees with the IPS data is automatically selected as the forecasted time.

We then validate the accuracy of this forecast using 12 halo CME events. The average absolute arrival-time error of the IPS-based MHD forecast is approximately 5.0 h, which is one of the most accurate predictions that ever been validated, whereas that of MHD simulations without IPS data, in which the initial CME speed is derived from white-light coronagraph images, is approximately 6.7 h. This suggests that the assimilation of IPS data into MHD simulations can improve the accuracy of CME arrival-time forecasts. The average predicted arrival times are earlier than the actual arrival times. These early predictions may be due to overestimation of the magnetic field included in the spheromak and/or underestimation of the drag force from the background solar wind, the latter of which could be related to underestimation of CME size or background solar wind density.
FSAT - An Open-Source Fracture Surface Analysis Toolbox
Authors: Heinze Thomas , Frank Sascha , Wohnlich Stefan
Published: March 2021

Fracture morphology influences various physical processes within a fracture, such as fluid flow, contaminant, and heat transport as well as mechanical shearing. Through the increasing availability of affordable high-precision scanning technology of open surfaces, drill cores, and broken rock samples, digital rock surfaces are easy to obtain and become a common tool to study hydraulic and mechanical processes inside fractures. Through statistical fracture generation and 3D printing technology, even custom-made fracture surfaces have been applied in numerous studies.

However, the complexity to describe and quantify fracture surface morphology is a major obstacle in evaluating and comparing results from laboratory and numerical experiments across studies and rock samples. While many so-called roughness parameters exist, there is no single parameter representing all features of a fracture surface. Only through a combination of parameters, which often is problem depending, a fracture surface can be suitably characterized to enable reproducibility of experiments and analysis across samples and studies. The effort of calculating various parameters is impeding scientists to sufficiently and quantitatively describe fracture surfaces.

We introduce an open-source MATLAB toolbox that allows the determination of over 25 different roughness parameters for height profiles as well as full 3D fracture surfaces. The selection of parameters includes statistical parameters, amplitude and spatial metrics, joint roughness coefficients, and fractal parameters. Variation of those parameters across as fracture surface as well as anisotropy is also calculated. For three-dimensional profiles, also surface measures are determined. If the top and bottom surfaces of a fracture are provided, even an estimated aperture distribution can be obtained, which is analyzed as well as provided for subsequent calculations, e.g., regarding the flow field. Further, the toolbox includes pre-processing routines for digital fracture surfaces of different sizes, shapes, and orientations. The toolbox is validated with standard profiles and synthetically generated fractures with known characteristics.

The toolbox massively simplifies the quantitative description of fracture surfaces, unifies the methodology of determining roughness parameters, and allows an easy generation of digital fractures with known characteristics. On the other hand, the toolbox enables easy customization for advanced users with specific demands. The toolbox consists of well-documented MATLAB scripts and functions that require a minimum of user-defined metadata. Extensive examples are also provided. The source code is freely available for download at https://gitlab.com/thomhGeoCode/fsat
GO-SHIP Easy Ocean: Formatted and gridded ship-based hydrographic section data
Authors: Katsumata Katsuro , Purkey Sarah , Cowley Rebecca , Sloyan Bernadette , Stephen Diggs , Moore Thomas , Talley Lynne , Swift James
Published: March 2021

Despite numerous technological advances over the last several decades, ship-based hydrography remains the only method for obtaining high-quality, high spatial and vertical resolution measurements of a suite of physical, chemical, and biological parameters over the full water column essential for physical, chemical, and biological oceanography and climate science. The Global Ocean Ship-based Hydrographic Investigations Program (GO-SHIP) coordinates a network of globally sustained hydrographic sections as part of the global ocean observing system, building on previous programs. These data provide a unique data set that spans four decades, comprised of  more than 40 cross-ocean transects, many with multiple repeats. The section data are, however, difficult to use owing to inhomogeneous format. The purpose of this data product is to increase the value of these data by better combining, reformatting and gridding in order to facilitate their use with less effort by a wider audience. The product is machine readable and readily accessible by many existing visualisation and analysis software packages. The data processing can be repeated with modifications to suit various applications such as analysis of deep ocean , validation of numerical simulation output, and calibration of autonomous platforms. This initial release includes temperature, salinity, and dissolved oxygen data from Conductivity-Temperature-Depth profiles, but the product will include other properties in future releases.
Atmospheric general circulation and waves simulated by a Venus AORI GCM with topographical and radiative forcings
Authors: Yamamoto Masaru , Hirose Takumi , Ikeda Kohei , Takahashi Masaaki
Published: March 2021

General circulation and waves are investigated using a T63 Venus general circulation model (GCM) with solar and thermal radiative transfer in the presence of high-resolution surface topography. This model has been developed by Ikeda (2011) at the Atmosphere and Ocean Research Institute (AORI), the University of Tokyo, and was used in Yamamoto et al. (2019, 2021). In the wind and static stability structures similar to the observed ones, the waves are investigated. Around the cloud-heating maximum (~65 km), the simulated thermal tides accelerate an equatorial superrotational flow with a speed of ~90 m/swith rates of 0.2–0.5 m/s/(Earth day) via both horizontal and vertical momentum fluxes at low latitudes. Over the high mountains at low latitudes, the vertical wind variance at the cloud top is produced by topographically-fixed, short-period eddies, indicating penetrative plumes and gravity waves. In the solar-fixed coordinate system, the variances (i.e., the activity of waves other than thermal tides) of flow are relatively higher on the night-side than on the dayside at the cloud top. The local-time variation of the vertical eddy momentum flux is produced by both thermal tides and solar-related, small-scale gravity waves. Around the cloud bottom, the 9-day super-rotation of the zonal mean flow has a weak equatorial maximum and the 7.5-day Kelvin-like wave has an equatorial jet-like wind of 60-70 m/s. Because we discussed the thermal tide and topographically stationary wave in Yamamoto et al. (2021), we focus on the short-period eddies in the presentation.
Impacts of convectively coupled equatorial waves on rainfall extremes in Java, Indonesia
Authors: Respati Muhamad Reyhan , Lubis Sandro W.
Published: March 2021

Rainfall extremes cause significant socioeconomic impacts in Indonesia, as they are often followed by disastrous events, such as floods and landslides. Of particular interest is Java Island, the most populated region in Indonesia, which is prone to damaging flooding as a result of heavy rainfall. The prediction of rainfall extremes in this region has mainly been focused on the effects of seasonal and intraseasonal variability, such as monsoons and the Madden–Julian Oscillation. Here, using an extensive station database from 1987 to 2017 and the gridded Asian Precipitation‐Highly Resolved Observational Data Integration Toward Evaluation of Water Resources (APHRODITE) product from 1980 to 2007, we show that severe weather conditions associated with rainfall extremes in Java during the rainy season (November to April) can also be attributed to convectively coupled equatorial waves (CCEWs) that occur on a shorter time scale.

Evidence is presented that CCEWs, including Kelvin, equatorial Rossby (ER), and mixed Rossby‐gravity (MRG) waves, significantly modulate daily rainfall extremes over Java Island. Of these three types, the Kelvin waves have the greatest influence on heavy rainfall over Java Island. The convectively active (suppressed) phases of Kelvin waves increase (decrease) the probability of extreme rain events over land regions by up to 60% (50%) of the baseline probability. On the other hand, the convectively active phases of ER (MRG) waves increase the probability by up to 45% (40%), while the suppressed phases decrease this by up to 40% (30%). In terms of the mechanism of rainfall extremes, CCEWs modulate moisture flux convergence, leading to the enhancement of local convection over the region. In addition, the analysis of multiple wave events indicates that positive (negative) interferences of the CCEWs lead to an amplification (suppression) of extreme rainfall probability. Overall, the results suggest that equatorial waves provide an important source of the predictability for daily extreme rainfall events over Java Island.

Reference:

Lubis, SW, Respati, MR. Impacts of convectively coupled equatorial waves on rainfall extremes in Java, Indonesia. Int J Climatol. 2020; 1– 23. 

 
Dynamics and physics-based rainfall thresholds for a deep-seated landslide
Authors: Xu Yuankun , Lu Zhong , Kim Jinwoo
Published: March 2021

The Hooskanaden landslide is a large (~600 m wide × 1,300 m long), deep (~30 – 45 m) slide located in southwestern Oregon, United States. Since 1958, it has had five moderate/major movements that catastrophically damaged the intersecting U.S. Highway 101, along with persistent slow wet‐season movements and a long‐term accelerating trend due to coastal erosion. Multiple remote sensing approaches, borehole measurements, and hydrological observations were integrated to interpret the motion behaviors of the slide. Pixel offset tracking of both Sentinel‐1 and Sentinel‐2 images was carried out to reconstruct the 3D displacement field of the 2019 major event, and the results agree well with field measurements. A 12‐year displacement history of the landslide from 2007 to 2019 was retrieved by incorporating offsets from LiDAR DEM gradients and InSAR (Interferometric Synthetic Aperture Radar) processing of ALOS and Sentinel‐1 images. Comparisons with daily/hourly ground precipitation reveal that the motion dynamics are predominantly controlled by intensity and temporal pattern of rainfall. A new empirical threefold rainfall threshold was therefore proposed to forecast the dates for the moderate/major movements. This threshold relies upon antecedent water‐year and previous 3‐day and daily precipitation, and was able to represent observed movement periods well. Adaptation of our threshold methodology could prove useful for other large, deep landslides for which temporal forecasting has long been generally intractable. The averaged characteristic hydraulic conductivity and diffusivity were estimated as 6.6 × 10−6 m/s and 6.6 × 10−4 m2/s, respectively, based on the time lags between rainfall pulses and slide accelerations. Hydrologic modeling using these parameters helps to explain the ability of the new rainfall threshold.
The effect of prevailing wind on shoreline landform evolution - Illustrated by the case of Buha River Delta and Hargai River Delta in the Qinghai Lake, western China
Authors: Liu Chao , Jiang Zaixing
Published: March 2021

Lacustrine sedimentation, which is considered to be relatively simple, can be dominated by high-energy wind-driven process. Qinghai Lake, located at the northeastern margin of the Qinghai-Tibet Plateau, western China, is a typical “wind-driven lake”, of which the sedimentation and evolution of shorelines are impacted by prevailing wind. In this research, Buha River Delta and Hargai River Delta, located at the northwestern and northeastern of the lake respectively, are studied through field investigation and remote sensing images analysis. The outcrop section of Buha River Delta is characterized by channel lag deposits, planar cross-beds, and trough cross-beds, indicating a dominant effect of river. However, the section of Hargai River Delta displays planar cross-beds, as well as swash cross-beds (beach deposits) and high-angle cross-beds dip to land (washover deposits), revealing a combined effect of river and waves. Remote sensing images in recent 40 years showed that Buha River Delta remained a stable shape except for the migration of mouth bars, which may be caused by lake level fluctuation. Nevertheless, Hargai River Delta has recorded a noteworthy change in its appearance, which was characterized by the formation of a barrier bar outside the estuary. Meteorological Data reveals that the Qinghai Lake is mainly affected by north-west wind and north wind, thus Buha River Delta is located at the leeward side, while Hargai River Delta is situated at the windward side and significantly influenced by high-energy wind-driven lake currents and waves. When the prevailing wind direction is oblique to the lake shoreline, the coastal current parallel to the shoreline formed by the decomposition of wind-driven waves would transport the clastic materials provided by Hargai River and then deposit them along the lake bank, finally forming a barrier bar parallel to the shoreline. This study reveals that wind-driven process could have totally different effects on either side of a “wind-driven lake”, thus can help us anticipate the evolution of shoreline landform of a “wind-driven lake” in the near future.
Impact of vegetation control measures on the bedform of braided gravel-bed river
Authors: Zhu Runye , Tsubaki Ryota
Published: March 2021

Braiding is among the most dynamic landscape on Earth. It provides diverse habitats for freshwater creatures. Unfortunately, the number of braided rivers is reducing affected by human activities in the Anthropic period. The increase of the vegetation cover within the river corridor is one important factor, which is induced by flow regime change, land-use change, or alien vegetation invasion. Vegetation clearance could be a promising measure to mitigate vegetation overexpansion. Several previous research suggested vegetation clearance may induce geomorphological metamorphosis. However, quantitative prediction of the morphological change resulted from the vegetation clearance is still an open question to date. We simulated the river morphological response of vegetated braided river with gravel bed to the vegetation clearance using the Nays2DH model combined with a vegetation module. Except for vegetation removal, the developed conceptual model considered vegetation colonization and the destruction induced by floods. Multiple scenarios have been tested, considering two vegetation types (strong and weak vegetation), two clearance methods (full clearance and partial clearance), and two maximum discharge. The full clearance scenario stood for the removal of above-ground and underground biomass simultaneously, and the partial clearance scenario stood for the removal of above-ground biomass. Braided rivers had developed for both no vegetation and river with weak vegetation cover. The bedform affected by strong vegetation coverage consisted of a main channel and small channels on the floodplain, which was consistent with previous experimental results. The distinctive morphology of developed bed form depended on the dominant factor in the vegetation-geomorphology interaction: vegetation dominant or physical process dominant. River morphology responded differently to the vegetation control measure based on the dominating factor. For the vegetation dominated river, the developed main channel tended to be braiding after the vegetation removal, and the river morphology change was sensitive to the vegetation clearance method. By contrast, river morphology changed insignificantly by vegetation colonization and after vegetation removal if the river physical process was dominant. We also found that the small channels on the floodplain promoted sediment transport from the floodplain to the main channel after the vegetation clearance. Thus, the morphological response to the vegetation clearance method was also affected by the reduction of maximum discharge because the connectivity between floodplain and channel was reduced. To improve vegetation clearance effectiveness, we recommend increasing the connectivity between the floodplain and the main channel, such as excavating small channels on the floodplain.