bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantification of the cross-helicity cascade with Karman-Howarth-Monin and Spectral transfer equations
Authors: Montagud-Camps Victor , Hellinger Petr , Verdini Andrea , Papini Emanuele , Franci Luca , Matteini Lorenzo , Landi Simone
Published: March 2022

Spectral transfer equations allow to  quantify the value of the energy flux of a turbulent flow across concentric shells in Fourier space. Karman-Howarth-Monin equations serve as a complement to the Spectral Transfer analysis, since they  quantify  as well the energy transfer rate of turbulence across scales via third-order structure functions, but also provide information on the directionality of the flux. We have extended the use of these methods to study the cascade of cross-helicity and compare it to the energy cascade  in 3D compressible MHD simulations. Our results show that the cross-helicity cascade reaches stationarity after the energy cascade, thus indicating a slower turbulence development for this invariant. Once fully developed, the cross-helicity cascade matches the main features of the energy one.
Disentangling soil moisture and vegetation effects on the ASCAT backscatter-incidence angle relationship
Authors: Greimeister-Pfeil Isabella , Wagner Wolfgang , Quast Raphael , Hahn Sebastian , Steele-Dunne Susan , Vreugdenhil Mariette
Published: March 2022

Microwave scatterometers provide global and frequent observations of the Earth’s surface. In particular, C-Band scatterometers are sensitive to the moisture content of the soil and vegetation in the sensor footprint, and can therefore be used for the retrieval of soil moisture (SM) and vegetation optical depth (VOD).

To model the vegetation component in the signal, and subsequently retrieve VOD, the slope (σ’) of the backscatter dependence on the incidence angle of the observation is exploited. This is possible because σ’ is related to the water content and structure of the canopy. Early studies moreover showed that SM effects on σ’ are weak and can, in a first approximation, be neglected. However, short-term dynamics in σ’ have raised questions about the validity of this assumption.

In this study, we investigate a potential SM effect on σ’ time series derived from the Advanced Scatterometer (ASCAT) by exploring relationships between σ’, SM, and leaf area index. We carry out the analysis over six study regions in Portugal, Austria, and Russia with different climate, land cover and vegetation cycles.

Spearman correlations between short-term anomalies of σ’ and SM are stronger than between σ’ and LAI, indicating that SM does have an effect on σ’. The analysis of daily σ’ values, as opposed to the smoothed σ’ that is used in retrieval algorithms, shows SM effects even more clearly: SM increases correspond to decreases of σ’, even during periods of vegetation growth, which are typically characterized by increasing σ’ values. Thus, we conclude that there is a SM signal in σ’ time series on top of the vegetation signal. Over sparse vegetation, the SM effect may be as large as 20% of the seasonal, vegetation-induced variation of σ’, whereas it is smaller over dense vegetation. Moreover, the short-term dynamics in σ’ time series might be caused by water on the canopy, i.e., interception or dew, to some extent. Further work is needed to confirm this hypothesis. For the retrieval of SM from ASCAT observations, these results confirm the use of a long-term average σ’ climatology instead of dynamic σ’ time series to correct for vegetation effects.
Topside Ionosphere Radio Observations from multiple LEO-missions 
Authors: Schreiter Lucas , Kervalishvili Guram , Rauberg Jan , Stolle Claudia , van den Ijssel Jose , Arnold Daniel , Xiong Chao , Callegare Andyara Oliveira
Published: March 2022

Topside Ionosphere Radio Observations from multiple Low Earth Orbiting (LEO)-missions (TIRO) is a project in ESA’s Swarm Data, Innovation, and Science Cluster (DISC) framework. TIRO provides high accuracy Total Electron Content (TEC) from dual-frequency GPS receivers onboard CHAMP (2000-2010), GRACE (2002-2017), and GRACE Follow-On (since 2018) missions. Special emphasis is put to ensure maximum consistency between the previously and operationally derived data sets from GOCE and Swarm to investigate conjunctions and thus ensure the consistency of the entire timeline from as early as CHAMP up to GRACE-FO. The primary science instrument onboard GRACE and GRACE-FO is a K-Band inter-satellite ranging system, which in this study is used to derive an estimate of the in-situ electron density. The derived electron density will be validated using both, the International Reference Ionosphere (IRI) model and radar observations taken at Millstone Hill, Arecibo, EISCAT, Resolute Bay, and Jicamarca. 

 

In combination, these products form long-term series and almost cover two full solar cycles by the continuous TEC data set and electron density either taken by CHAMP, GRACE, Swarm, or GRACE-FO. We will present climatological studies as well as case studies of selected events, such as equatorial plasma depletions, simultaneously observed by GPS and K-Band.  
Relative sea-level rise scenarios for 2100 in the Venice lagoon by integrated geodetic data, high-resolution topography and climate projections. New insights from the SAVEMEDCOASTS-2 Project.
Authors: Anzidei Marco , Crosetto Michele , Josè Navarro , Cristiano Tolomei , Petros Patias , Charalampos Georgiadis , Antonio Vecchio , Fawzi Doumaz , Lucia Trivigno , Antonio Falciano , Michele Greco , Enrico Serpelloni , Silvia Torresan , Qui Gao , Anna Barra , Claudia Ferrari , Chiara Tenderini , Xenia Loizidou , Demetra Orthodoxou
Published: March 2022

Here we show and discuss the results arising from the SAVEMEDCOASTS-2 Project (Sea Level Rise Scenarios along the Mediterranean Coasts - 2, funded by the European Commission ECHO) for the Venice lagoon (northern Italy). We used geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR) from Copernicus Sentinel-1A (S1A) and Sentinel-1B (S1B) sensors and sea-level data from a set of tidal stations, to show subsidence rates and SLR in this area. The lagoon is well known for centuries to be prone to accelerated SLR due to natural and anthropogenic land subsidence that is causing increasing events of flooding and storm surges exacerbated by climate change. We focused on selected zones of the lagoon, characterized by particular heritage, coastal infrastructures and natural areas where the expected RSLR by 2100 is a potential cause of significant land flooding and morphological changes of the land. Results of the multi-temporal flooding scenarios until 2100 are based on the spatially variable rates of vertical land movements (VLM), the topographic features of the area provided by airborne Light Detection And Ranging (LiDAR) data and the Intergovernmental Panel on Climate Change (IPCC AR-5) projections of SLR in the Representative Concentration Pathways RCP2.6 and RCP8.5 emission scenarios. Our results show a diffuse land subsidence locally exceeding 9±2 mm/yr1. A variable RSLR between 0.62±0.12 m and 1.26±0.12 m is expected for 2100 AD in the RCP8.5 scenario. For this reference epoch, most of the investigated areas will be vulnerable to inundation in the next 80 years. A relevant concern is the protection of the historical city of Venice although the MOSE system has recently come into operation to prevent the effects of high tides in the lagoon. The hazard implications for the population living along the shore should push land planners and decision-makers to take into account long-term SLR scenarios in the definition and prioritization of adaptive pathways for a climate-resilient management of the Venice lagoon.
Hierarchical Soil Classification using Gaussian Processes
Authors: Gläßle Thomas , Rau Kerstin , Scholten Thomas , Hennig Philipp
Published: March 2022

The goal of this work is to perform soil classification with uncertainty quantification for a structured treatment of the output classes. Uncertainty can help in this setting to make predictions more informative with regard to class relationships. This is of particular interest due to the often highly related nature of the distinguished soil types. Incorporating knowledge about class structure into the model also provides opportunity for improving the model accuracy. Our main focus, however, is to enable modellers to better understand and work with this structure during analysis.
For example, post-hoc aggregation of class labels into supersets facilitates applications such as letting the model choose an ontological level on which it can confidently distinguish the output class. It can likewise be used to determine the combined probability of specified classes that share a property of interest.
Technically, this works by learning a latent Gaussian distribution, for example using a Gaussian Process model, and mapping it to a distribution over the class probabilities. We demonstrate this approach, explore possible applications for exploiting uncertainty information, in particular with regard to the class hierarchy, and compare the performance of different model variants in terms of accuracy and calibration.
Spatial and temporal variability of inorganic halogen sources and sinks over the marine boundary layer and free troposphere
Authors: Fernandez Rafael Pedro , Reynoso Amelia , Maldonado Alexis , Tomazzeli Orlando , Cremades Pablo , Berná Lucas , Lopez Noreña Ana Isabel , Cuevas Carlos , Li Qinyi , Saiz-Lopez Alfonso
Published: March 2022

Very Short-Lived (VSL) Halogens are primary organic compounds that are mainly emitted to the atmosphere from the biologically productive regions of the oceans, where the rapid and permanent vertical transport can uplift halogen-rich air-masses above the Marine Boundary Layer (MBL) well into the Free Troposphere (FT). Depending on the changes of convection strength, the regional distribution of oceanic sources, and the seasonality of the VSL photochemical losses, the release of inorganic halogen atoms from their initial organic sources due to reaction with OH and/or photolysis, can present a pronounced spatio-temporal variability. In addition, depending on the height and background where the initial inorganic halogen atoms are released, an additional atmospheric halogen source arising from the efficient halide uptake occurring over sea-salt aerosols (the so-called SSA-dehalogenation) enhances the total tropospheric halogen loading. Given the variable solubility and washout efficiency of the different gas-phase halogen species, considering their instantaneous partitioning, as well as their individual sinks for different in-cloud, below-cloud and clear-sky conditions, is of major importance to determine the total inorganic halogen budget within the MBL and FT. In this work, we present a modeling study performed with the state-of-the-art CAM-Chem model, oriented to determine the vertical, geographical and temporal distribution of the inorganic halogen sources and sinks on the global troposphere, distinguishing between the different regimes prevailing between tropical and high-latitude regions, as well as the distinctive behavior controlling the day/night and seasonal variability. A species-by-species inter-comparison for the VSL Chlorine, Bromine, Iodine families is presented, distinguishing the dominant sources, sinks and photochemical channels controlling the halogen burden at different heights, and highlighting the commonalities and differences existing among the chlorine, bromine and iodine families.
Emission of Primary Bioaerosol Particles from Baltic Seawater
Authors: Freitas Gabriel , Stolle Christian , H. Kaye Paul , Stanley Warren , P.R. Herlemann Daniel , Salter Matthew , Zieger Paul
Published: March 2022

Bioaerosols are particles originating from biological sources. Of these, primary bioaerosol particles (PBAP) are those directly emitted as entities, in parts or as agglomerates of particles such as bacteria, spores or pollen. In the atmosphere, PBAP are important players by acting as cloud condensation nuclei and ice nucleating particles (INP). Their relevance for cloud formation is especially important over pristine marine environments, where PBAP are emitted within sea spray aerosol (SSA) and are expected to contribute significantly to the abundance of INP. However, the emissions and sources of PBAP over oceans remain poorly understood.

Within this work, we performed a controlled sea spray experiment in the Baltic Sea using a novel single-particle fluorescence and scattering instrument, the Multiparameter Bioaerosol Spectrometer (MBS), in combination with bacterial analysis of aerosol and sea water communities. Using this setup, we successfully identified large PBAP (D > 0.8 µm) within SSA and estimated their emissions to be 1 s-1m-2. Moreover, 1 out of every 104 particles (D > 0.8 µm) was classified as PBAP. The morphology of large fluorescent SSA showed a clear transition during the campaign. This change was most likely linked to changes in the seawater biogeochemical properties observed during the ship campaign. This change was also observed in changes of the bacterial population of the aerosol and seawater, as determined by the 16s rRNA analysis. The bacterial populations were significantly distinct from each other, implying a selective transfer of certain species from seawater to the atmosphere.

Our results will help to better constrain the emission of PBAP from marine sources to the atmosphere and will help to understand how biogeochemical processes within the sea water can influence particle properties of SSA (e.g. particle morphology).

The content of this work is currently in review at Environmental Science and Technology (ES&T).
An update on modeled ion sputter yields of planetary bodies in agreement with recent experimental data
Authors: Jäggi Noah , Biber Herbert , Szabo Paul Stefan , Vorburger Audrey , Mutzke Andreas , Aumayr Friedrich , Wurz Peter , Galli André
Published: March 2022

Thin, collisionless atmospheres are created around otherwise atmosphere-free celestial bodies through space weathering processes. Impinging solar wind ions eject highly energetic particles into these atmospheres by sputtering. Some ejected particles escape from the atmosphere, some return to the surface or are ionized and might be caught in a surrounding magnetosphere or the solar wind plasma. This process can be observed far into space through ground based and in-situ observations.

Determining the sputter yield of the various species from a realistic mineral surface is still a work in progress [1]. Modeling of sputtering with commonly used Binary Collision Approximation (BCA) models such as TRIM [2] has been shown to overestimate the sputter yields compared to experimental data [3, 4]. The number of sputter experiments performed on rock forming minerals is growing steadily, however. We apply the latest findings to obtain yields for a range of minerals from the state-of-the-art model SDTrimSP [5], which is based on TRIM. 

To obtain yields of surface compositions of rocky bodies we present an approximation through weighing each mineral’s sputter yield contribution. This improves upon the simplification of assuming a bulk surface composition with TRIM and the resulting overestimated sputter yields. Simulating each mineral separately with SDTrimSP and considering the current knowledge on sputter behavior is tedious and requires extensive computing power. For this reason, we develop a database of sputter yields for important rock-forming minerals allowing easy access for researchers on which we will show our progress.

 

[1] Jäggi, N., et al. (2021). Icarus, 365, 114492. 

[2] Ziegler, J.F., et al. (2010). Nucl. Instrum. Methods Phys. Res. B, 268, 1818–1823. 

[3] Biber H., et al. (2020). Nucl. Instrum. Methods Phys. Res. B, 480, 10. 

[4] Szabo, P.S., et al. (2018). Icarus, 314, 98–105.

[5] Mutzke, A., et al. (2019). SDTrimSP Version 6.00. Max-Planck-Institut für Plasmaphysik.
Exploring the effect of inventory un-completeness in landslide susceptibility assessment: a test for conditional analysis- and regression-based models.
Authors: Martinello Chiara , Mercurio Claudio , Cappadonia Chiara , Mineo Giampiero , Bellomo Viviana , Azzara Grazia , Rotigliano Edoardo
Published: March 2022

Landslide susceptibility can be evaluated by using different statistical approaches. Among these, the methods based on conditional analysis exploit the observed incidence of landslides into homogeneous statistical domains (corresponding to single classes of each geo-environmental variable or to multivariate Unique Condition Units) to estimate their landslide susceptibility. Thus, the results of these types of analysis can be heavily compromised by the completeness or representativeness of the adopted landslide archive. On the other hand, inference-based frequentist methods allow scoring landslide susceptibility by using limited samples of cases, provided the calibration samples are statistically representative of the whole population, assuming that the lacking cases are missing completely at random.

This research aims to evaluate the effect of incomplete inventories in assessing landslide susceptibility, by using conditional analysis (Weight of Evidence, WoE; Frequency Ratio, FR) and inference-based (Binary Logistic Regression, BLR; Multivariate Adaptive Regression Splines, MARS) methods. In particular, we analysed the effects in terms of prediction skill of each of the four methods by reducing and randomly hiding the training calibration cases (and increasing the related validation cases).

The study was conducted in the Imera Settentrionale river basin (Sicily, Italy), by exploiting two different landslide archives (5134 earth flow and 1608 rotational/translational slides) and a set of 10 physical-environmental predictors. Cutoff-dependent and -independent metrics (ROC-curve analysis and confusion matrixes) were used to estimate the performance of the models.

As general assumptions, MARS and BLR modeling resulted as markedly more performing with moderately and asymptotically AUC improving up to 30-40% of the whole dataset, corresponding to the reaching of the relative optimal performance. A similar asymptotic AUC-increasing trend is described for WoE and FR, but with a lower performance. In particular, the optimal AUC values for rotational/translational slides range between 0.77 and 0.90, for BLR, 0.82 and 0.90, for MARS, 0.78 and 0.80, for FR, 0.76 and 0.78, for WoE. At the same time, a general lower model performance resulted for earth flows, with AUC values ranges of 0.69 and 0.75, for BLR; 0.75 and 0.79 for MARS; 0.67 and 0.70 for FR; 0.56 and 0.6, for WoE. Furthermore, differences in the selected predictors produced by the cases reduction were also explored through the analysis of the variable importance and the response curves.

 
Investigating the 'Hothouse narrative' with dynamical systems
Authors: Couplet Victor , Crucifix Michel
Published: March 2022

The 'hothouse narrative' states that tipping cascades could lead humanity to a binary choice between a 'governed Earth' and a 'hothouse' with no midway alternative. To investigate this scenario, we construct a toy model of interacting tipping elements and ask the following questions: Given a continuous family of emission scenarios, are there discontinuities in the family of responses, as suggested by the 'hothouse narrative'? How realistic is this given knowledge provided by climate simulations and paleo-climate evidence? The relatively low complexity of our model allows us to easily run it for several thousand years and a large range of emissions scenarios, helping us highlight the fundamental role of the different time scales involved in answering our questions. On the one hand, we find that the near-linear relationship predicted by GCMs between global temperature and GHG emissions for the next century can break up at millennial time scales due to cascades involving slower tipping elements such as the ice sheets. This translates as a discontinuity in the family of responses of our model. On the other hand, we find that different emissions scenarios respecting the same carbon budget could potentially lead to different tipping cascades and thus qualitatively different outcomes.
Long-term trend of equatorial Atlantic zonal SST gradient linked to the tropical Pacific cold tongue mode under global warming
Authors: Li Yang , Chen Quanliang , Xing Nan , Cheng Zhigang , Qi Yulei , Feng Fan , Li Minggang
Published: March 2022

The equatorial Atlantic zonal sea surface temperature (SST) gradient, which has significant climatic and biogeochemical effects, is closely associated with the equatorial Pacific zonal SST gradient through Walker circulation on seasonal and interannual time scales. However, discrepancies in current SST datasets mean that its long-term trend is not well understood. Here, using multiple datasets, we find a robust weakening long-term trend (i.e., greater warming in the east than west) in the equatorial Atlantic zonal SST gradient over the period 1900–2010 in all datasets. We also find that this weakening trend is closely linked to the tropical Pacific cold tongue mode (CTM), which corresponds to a strong increasing long-term trend of zonal SST gradient along the equatorial Pacific (i.e., warming in the west and cooling in the east). Specifically, the long-term cooling SST anomalies associated with the CTM modify the Walker circulation, and leads to weaker trade winds over the western equatorial Atlantic. These in turn deepen the thermocline in the eastern equatorial Atlantic, and cause the weakening long-term trend of SST gradient along the equatorial Atlantic. The long-term trend of the CTM is induced by ocean dynamical feedback in response to global warming, suggesting that global warming could affect the equatorial Atlantic zonal SST gradient via the CTM. Our results provide a novel explanation of the linkages between the long-term trend of equatorial Atlantic zonal SST gradient and the CTM under global warming, which carries important implications for the relationship between global warming and the equatorial Atlantic zonal SST gradient.
A hybrid online/on-site field trip: Reconstructing Earth’s Past Climate from the sedimentary record. 
Authors: Hawemann Friedrich , Kirilova Martina , Toy Virginia , Fenske Selina , Seelos Philip
Published: March 2022

The last two years of global pandemic forced many traditional classes to be cancelled and alternative teaching solutions to be sought, which triggered development of substantial virtual resources for training in geological field work. Virtual geology has proven to have significant advantages over traditional field work in aspects such as: 1) ability to include people with physical limitations, 2) reduction of costs for students, 3) flexible working hours, 4) independence of weather conditions. Nevertheless, most geoscience lecturers would agree that virtual classes are unable to entirely replace on-site classes, because they do not allow development of certain observational skills and 3D perception, field hardiness, or in-person team communications. We therefore propose a hybrid course design within the European Universities “FORTHEM” framework, which integrates virtual and on-site teaching techniques. This course not only demonstrates novel teaching methodology but also trains students to integrate variable sources of information; such capabilities are critical to allow graduate geoscientists to thrive in our current information age.

The field area is located in Molinos, Teruel province of eastern Spain, where a fossil-rich Jurassic-Cretaceous sedimentary sequence is exposed. The record mainly comprises marine units, which reveal changes in depositional environment that reflect paleoclimate changes. However, the area is extensively folded and faulted, and thus the tectonic deformation needs to be unraveled in order to determine the original depositional sequences. Students participating on-site will therefore study the fossil record of the rocks, measure faults and folds and create a geological map of the area. A second group of students will work from their home, examining the microfossils in thin section images and use 3D models of outcrops to describe the geometry of folds and faults, and perform digital geological mapping with the aid of satellite images. The two groups of students will be working on the same challenges but on different scales and thus an exchange of field and digital observations between students will be encouraged and required to obtain a holistic understanding of the local geology. As an outcome of this course students will reconstruct a timeline of environmental changes through the Jurassic-Cretaceous period. All data will be collected in database driven applications, allowing swift exchange of data, and its longer term preservation in a uniform format.
Climate change impact on wildfires in the Canary Islands
Authors: Carrillo Judit , Pérez Juan Carlos , Expósito Francisco Javier , Díaz Juan Pedro , González Albano
Published: March 2022

The frequency and intensity of wildfires will be aggravated by climate change. Small islands are more vulnerable to these events due to their greater number of endemic species, little territory, and the isolation of their firefighting systems, among others. Climate projections of Fire Weather Index (FWI) have been accomplished using as boundary conditions the results provided by the CMIP5 initiative, using Weather Research and Forecasting (WRF) model, with a spatial resolution of 3x3km, until the end of the century, and two Representative Concentration Pathways (RCPs), 4.5 and 8.5. The length of the fire season is expected to increase up to 74 days per year and the area with high risk could increase by 43%. In addition, FWI is projected to increase with altitude, mainly due to increasing temperature and decreasing precipitation, which are more pronounced at higher elevations.
Preliminary results from the Second Earth Orientation Parameters Prediction Comparison Campaign of the IERS
Authors: Nastula Jolanta , Dobslaw Henryk , Śliwińska Justyna , Kur Tomasz , Wińska Malgorzata , Partyka Aleksander
Published: March 2022

Precise positioning and navigation on the Earth’s surface and in space require accurate Earth Orientation Parameters (EOP) data and predictions. In the last few decades, the problem of EOP prediction has become a subject of increased attention within the international geodetic community, and many research centres from around the world have developed their own methods of forecasting the EOP. It is not surprising that those various predictions differ in many aspects such as accuracy and the length of the forecast horizon.

A re-assessment of the various EOP prediction capabilities is currently pursued in the frame of the 2nd EOP PCC, which started in September 2021. The new campaign was prepared by the EOP PCC office run by the Space Research Centre of the Polish Academy of Sciences (CBK PAN) in cooperation with GeoForschungsZentrum (GFZ) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS). The campaign will be continued until the end of the year 2022 and all interested scientists are invited to contribute with new predictions at any time.

In this presentation, we provide preliminary results of the 2nd EOP PCC by focusing on the quality of EOP predictions up to 10 days into the future. The quality assessment includes metrics such as mean absolute error (MAE) and root mean square error (RMSE) for the ensemble of all predictions, but also more detailed assessments of individual predictions. The accuracy of EOP forecasts is determined using IERS 14 C04 solution as a reference. We will pay special attention to the impact of input data exploited by participants, including the Effective Angular Momentum functions.
Spatiotemporal variability of CO2, CH4 and N2O fluxes over a soil hydrological gradient reveal soil water-temperature interactions on biogeochemical pathways
Authors: Christiansen Jesper , Steenberg Larsen Klaus
Published: March 2022

Exchange of greenhouse gases (GHG) between soils and the atmosphere are highly dynamic in space and time challenging prediction of how the fluxes from soils respond to environmental change. The soil hydrological and thermal regime are major drivers of the rates of biogeochemical processes producing or consuming GHG's in the soil, but how these factors interact to regulate net GHG fluxes is unclear.

Part of the reason is the lack of high frequency in situ GHG flux measurements in environments with gradients of the hydrological and thermal regimes. Disentangling the interactive effects of soil hydrology and temperature on GHG fluxes based on in situ observations is key for building more accurate biogeochemical models.

Here we present the results from a unique GHG flux observation campaign using the SkyLine2D automated chamber measurement system. Contrary to other automated chamber systems, the SkyLine2D uses one chamber moved along two ropes and lowered on to predefined collars on the ground which is ideal for studying environmental gradients. With the SkyLine2D we can study the complexity of the interactions of GHG fluxes and edaphic and dynamic factors.

We deployed the SkyLine2D with a total of 30 individual flux collars covering a soil hydrological gradient in a reestablished beech forest swap in Denmark, from well-drained upland to waterlogged and occasionally flooded soils. Along the transect automated measurements of groundwater depth (GWD), soil moisture (SM) and temperature (ST) were measured continuously together with climatic parameters (rain, humidity, wind and air temperature). Bulk density, pH and carbon/nitrogen pools were measured as well along the transect. Plants were excluded by clipping above ground parts in the collars to measure net soil GHG fluxes.

The campaign covered a 2-year period (2019 – 2021) with simultaneous measurements of net CO2, CH4 and N2O fluxes. With these data we will explore spatiotemporal patterns in GHG fluxes and relation of these to soil hydrology and temperature. We seek to present multi-factorial GWD/SM/ST -  GHG flux response functions nested within a soil type gradient (carbon/nitrogen pools, pH).
SIMULATION  on the Gully Erosion Reduction Ability of Check Dam—A Case Study of Xiliugou Basin
Authors: Feng Yangfan
Published: March 2022

 In order to scientifically understand the effect of the construction of check dams on the erosion dynamic process and the ability to reduce gully erosion in the wind-water cross erosion area, in this study, the Xiliugou Basin, one of the ten tributaries, was taken as the research area, and the differences of flood process, erosion dynamics and energy in gully after the construction of check dams were simulated and quantitatively calculated by coupling the distributed hydrological model MIKE SHE and the one-dimensional hydrodynamic model MIKE 11. The reduction of gully erosion by check dams was also estimated. The results showed that: (1) The check dams decreased the flood peak and flood volume of the outlet section by 40.90% and 35.85%, respectively. (2) The average flow velocity, runoff shear force and runoff power along the main gully of the watershed were dropped by 21.66%, 22.02% and 34.31%, respectively. (3) During the planned operation period of the project, the check dams reduced the amount of gully erosion by 3.31 million tons under the condition of multi-year average precipitation. The construction of check dams has significantly changed the flooding process of Xiliugou Basin, which alleviated the erosion dynamic along the main channel as well as provided effective erosion mitigation effects.
Controls on the deposition of extremely large post-earthquake debris flows in Wenchuan
Authors: Harvey Erin , Hales Tristram , Hobley Daniel , Horton Alexander , Liu Jie , Fan Xuanmei
Published: March 2022

Debris flows are the dominant process delivering sediment from hillslopes into channels following the 2008 Wenchuan earthquake. Post-earthquake debris flows continue to pose a significant hazard to the recovering local communities. In 2019, a period of intense rainfall triggered several extremely large debris flows. The flows bulked to volumes in excess of 100 000 m3,  much larger than their initiation volumes, and transited catchments to be deposited in the Min Jiang river. The scale of these flows highlights our limited understanding of why and where large debris flows deposit. Previous studies have shown that topography (notably bed slope and channel width), flow composition (grain size), and flow characteristics (velocity and depth) can all control debris flow runout. Yet, there is limited understanding of how these interrelate. For example, whether abrupt changes in topography, such as increased channel width, lead to the deposition of certain grain size fractions and subsequently encourage further deposition. Alternatively, whether changes in bed slope affect flow velocity and this results in the entrainment of specific grain size fractions by the flow. An understanding of these relationships will help to better constrain where and how post-earthquake debris flows are more likely to deposit.

In this study, we determine how debris flow characteristics (velocity and depth) and the grain size distribution (GSD) deposited by the debris flow evolve with changes in topography and distance from the initial debris flow source. To achieve this, we simulated two post-earthquake debris flow events in the Liusha and Luoquan catchments, China, using the 2D dynamic debris flow model, Massflow. GSDs were collected by sampling and sieving pits located equidistantly along the centre of each 2019 debris flow deposit. Bed topography data was recorded both in the field and using a 30 m resolution DEM. We compared changes in the flow characteristics and GSDs deposited for each debris flow with the data for bed topography to explore how controls on debris flow runout interrelate. Preliminary findings for the Luoquan debris flow suggest a relationship between negative changes in curvature and the deposition of fine-grained material. This work will help to better understand controls on debris flow runout, subsequently aiding future studies of post-earthquake debris flow hazard prediction.
Characterizing ferrofluid properties for a more reliable and quantitative interpretation of magnetic pore fabric studies
Authors: Biedermann Andrea Regina , Pugnetti Michele , Zhou Yi , Parés Josep M
Published: March 2022

Magnetic anisotropy is a time-efficient and powerful tool to characterize the anisotropy of pore space in ferrofluid-impregnated rocks. Empirical correlations exist between magnetic pore fabrics and the shape preferred orientation of pores, as well as between magnetic pore fabrics and permeability anisotropy. Up to now, quantitative interpretation has been challenging, and one reason is the variability of ferrofluids and their properties that have been used in different studies. Namely, the susceptibility of the ferrofluid largely controls the degree of measured magnetic anisotropy. Being a colloidal solution of superparamagnetic particles, ferrofluid displays magnetic properties that are both frequency- and time-dependent. This in turn affects the quantitative interpretation of magnetic pore fabrics. This study sheds light on the magnetic properties of the ferrofluids used in pore fabric studies, with a particular focus on processes such as particle aggregation and sedimentation, and how these affect ferrofluid impregnation as well as the measured pore fabrics. Further, interactions between the ferrofluid and the rock that lead to changes in magnetic properties are studied. These results will form the basis for future quantitative interpretation of magnetic pore fabric studies in groundwater, CO2 or hydrocarbon applications.   
Interactions of asperities controlling on fault stability: An experimental approach
Authors: Shu Weiwei , Lengliné Olivier , Schmittbuhl Jean
Published: March 2022

The transition between seismic slip and aseismic creep of faults in the Earth crust suggests a strong time-dependent mechanism for the underlying physics and corresponding mechanical response of fault slip. Asperities establish the real contact on the slipping interface of a fault and serve as stress concentrators that control the initiation of earthquakes. Investigating the interactions between individual asperities and how the global stability of a fault is controlled by the collective effects of their local behaviors are essential for understanding the intrinsic relationships between earthquake swarms and faulting. Here we design a novel direct-shear experimental setup, which allows a thick PMMA (poly-methyl-methacrylate) plate to slide slowly on a customized surface, on which asperities are modeled by spherical PMMA beads and embedded in a softer polymer base, for analogizing tectonic faults. We perform various experiments by applying multiple normal loads and loading rates, with a high-resolution camera employed to capture the detailed activities of asperities. We demonstrate the global stability of a fault could be described by the synthesized behaviors of local asperities. We also prove, for the same asperity, it can experience different slip modes at different time periods. We generate a catalog of fault slip events defined by the slipping velocity of each asperity derived from the image correlation technology, and then we determine slip episodes based on time and space successively. Furthermore, we investigate the distributions of various parameters of the determined slip episodes, including the number of slipping asperities, as well as the duration, mean slip displacement, and moment of slip episodes. We explore the spatiotemporal variations of b-value within one analog seismic cycle and under different normal loads and loading rates. We link the findings at local scales with the bulk mechanical response of the whole fault. Our results bring new insights into the physics and mechanics of seismic and aseismic faulting.
Venusian Thermosphere variability by IPSL Venus GCM
Authors: Martinez Antoine , Lebonnois Sebastien , Millour Ehouarn , Pierron Thomas , Moisan Enora , Gilli Gabriella , Lefevre Franck
Published: March 2022

For fifteen years, a Global Climate Model (GCM) has been developed for the Venus atmosphere at “Institut Pierre-Simon Laplace” (IPSL), in collaboration between LMD and LATMOS, from the surface up to 150 km altitude (Lebonnois et al., 2010; 2016). Recently, the vertical grid was extended from 10-5 Pa to 10-8 Pa (~180-250 km) and allows us to simulate the Venusian upper thermosphere. At the same time, improvements were made on the parameterization of non-LTE CO2 near infrared heating rates, on the parameterization of non-orographic gravity waves and a tuning was performed on atomic oxygen production to improve the thermospheric densities and their effects (heating and cooling; Martinez et al., 2022; submitted).

This work focuses on validating the modeled thermospheric structure by comparison using data from the Pioneer Venus, Magellan and Venus Express missions which cover similar and complementary (equator and pole) regions at different periods of solar activity, typically above 130 km in altitude. In particular, we will discuss the importance of atomic oxygen in regulating the thermospheric temperature, the effect of the solar cycle on the upper thermosphere and the effect of non-orographic gravity waves on the diurnal temperature profile.

 

References:

Lebonnois, S., Hourdin, F., Eymet, V., Crespin, A., Fournier, R., Forget, F., 2010. Superrotation of Venus’ atmosphere analyzed with a full general circulation model. J. Geophys. Res. (Planets) 115, 6006. https://doi.org/10.1029/2009JE003458.

Lebonnois, S., Sugimoto, N., Gilli, G., 2016. Wave analysis in the atmosphere of Venus below 100-km altitude, simulated by the LMD Venus GCM. Icarus 278, 38–51. https://doi.org/10.1016/j.icarus.2016.06.004.

Martinez et al. 2022, submitted to Icarus
Source-to-front mixing in a tidally pulsed river plume: mechanisms and evolution
Authors: Spicer Preston , Huguenard Kimberly , Cole Kelly , MacDonald Daniel , Whitney Michael
Published: March 2022

River plumes can form where rivers discharge into the ocean and create transport and mixing pathways which ultimately blend freshwater with salty. Biogeochemical processes such as hypoxia, algal blooms, and primary productivity can be influenced by physical plume processes, making the topic important to study. Mixing, which we define as fluxes of buoyancy across isopycnals (vertical turbulent buoyancy flux, B), has historically been difficult to characterize in river plumes due to limited spatial and temporal resolution of measurements. Former work has generally focused on one plume region (i.e., the front, source, or nearfield) at a static point in time. In this presentation, we present novel CTD (conductivity, temperature, depth), turbulence, and current measurements in the tidally pulsed Merrimack River plume over an ebb tidal pulse (~7 hours) from plume source to front. Data was collected during calm conditions with negligible influence from wind and waves. Measurements allow for the quantification of B at multiple stations along three source-front transects, providing refined spatiotemporal mixing estimates in a tidal plume. Results indicate plume mixing is maximized (B ~ 10-4–10-5 m2s-3) in the nearfield plume, just seaward of the mouth, over the entire ebb pulse. Mixing then generally decays approaching the plume front, where it then exhibits a local maximum (B ~ 10-5–10-6 m2s-3) which is lesser in magnitude than the nearfield location but larger than in the transitional region between nearfield and front (B ~ 10-6–10-7 m2s-3). Two mixing regimes are evident over the tidal pulse: interfacial mixing which entrains relatively salty, cold water from the ambient shelf into the plume layer, and plume-layer shear mixing which mixes different plume density classes but does not entrain ambient water into the plume. Interfacial mixing dominates everywhere in the plume during the initial ebb, jet-like discharge and throughout the tidal pulse in the nearfield. Plume-layer mixing develops near the time of maximum ebb discharge in the region between nearfield and front and sustains to the end of the tidal pulse. These observations are the first to characterize the development of mixing throughout the interior plume over a tidal pulse.
Quasi-geostrophic coupled model under location uncertainty
Authors: Li Long , Mémin Etienne , Chapron Bertrand , Lahaye Noé
Published: March 2022

In this work, we aim to describe atmosphere-ocean coupling through a physically-based stochastic formulation. We adopt the framework of modelling under Location Uncertainty (LU) [Bauer2020a], which is based on a temporal-scale separation and a stochastic transport principle. One important characteristic of such random model is that it conserves the total energy of the resolved flow. This representation has been successfully tested for ocean-only models, such as the barotropic quasi-geostrophic (QG) model [Bauer2020b], the multi-layered QG model [Li2021], as well as the rotating shallow-water model [Brecht2021]. Here, we consider the ocean-atmosphere coupled QG model [Hogg2003]. The LU scheme has been tested for coarse-grid simulations, in which the spatial structure of ocean uncertainty is calibrated from eddy-resolving simulation data while the atmosphere component is parameterized from the ongoing simulation. In other words, the ocean dynamics has a data-driven stochastic component whereas the large-scale atmosphere dynamics is fully parameterized. Two major benefits of the resulting random model are provided on the coarse mesh: it enables us to reproduce the ocean eastward jet and its adjacent recirculation zones; it improves the prediction of intrinsic variability for both ocean and atmosphere components. These capabilities of the proposed stochastic coupled QG model are demonstrated through several statistical criteria and an energy transfers analysis.

References:

[Bauer2020a] W. Bauer, P. Chandramouli, B. Chapron, L. Li, and E. Mémin. Deciphering the role of small-scale inhomogeneity on geophysical flow structuration: a stochastic approach. Journal of Physical Oceanography, 50(4):983-1003, 2020.

[Bauer2020b] W. Bauer, P. Chandramouli, L. Li, and E. Mémin. Stochastic representation of mesoscale eddy effects in coarse-resolution barotropic models. Ocean Modelling, 151:101646, 2020.

[Li2021] Li, L., 2021. Stochastic modelling and numerical simulation of ocean dynamics. PhD Thesis. Université Rennes 1.

[Brecht2021] Rüdiger Brecht, Long Li, Werner Bauer and Etienne Mémin. Rotating Shallow Water Flow Under Location Uncertainty With a Structure-Preserving Discretization. Journal of Advances in Modeling Earth Systems, 13, 2021MS002492.

[Hogg2003] A.M. Hogg, W.K. Dewar, P.D. Killworth, J.R. Blundell. A quasi-geostrophic coupled model (Q-GCM). Monthly Weather Review, 131:2261-2278, 2003.

 
Detecting most effective coastal plastic clean-up hubs using network theory: a case study in the Galapagos Marine Reserve 
Authors: Ypma Stefanie , Bohte Quinten , Jones Jen , Donnelly Andy , van Sebille Erik
Published: March 2022

Over 8 tonnes of plastic are removed from the coastlines of the Galapagos Islands each year. Although the Galapagos Marine Reserve is expanding to ensure an even larger protection of its unique biodiversity, the island authorities face the challenge to effectively remove plastic from its shorelines due to limited resources. We are developing a clean-up efficacy model that will optimize for most cost-effective and least-invasive clean-up locations. Network (connectivity) theory is widely applied in ecology to study the interaction of species between spatially separated habitats. Here, we use a similar approach to discern the most effective removal hubs on the Galapagos Islands. A connectivity matrix is constructed from a Lagrangian simulation describing the flow of macroplastic between the various islands within the Galapagos Marine Reserve, where the nodes represent locations along the coastline and the edges the likelihood that plastic travels from one location and beaches at another. To measure the impact of removal, various centralities are determined, such as degree centrality, betweenness centrality (using the most likely path) and eigenvector centrality. Combining the results with other metrics such as the distance to the nearest port or tourist attractions, recommendations are made for

most effective intervention removal hubs that would prevent further spread of plastic throughout the marine reserve

most effective accumulation removal hubs that would negate the impact of plastic on wildlife

most suited regions for protection resulting from the existence of clusters (e.g. regions of limited connectivity)

Though we focus on the Galapagos Islands, the methods we present are directly applicable to archipelagos worldwide that face marine plastic pollution issues.