bluuebunny/crossref_metadata_2025 huggingface dataset:
Global scale numerical modelling of the transition to modern day plate tectonics
Authors: Gray Timothy , Tackley Paul , Gerya Taras , Stern Robert J.
Published: March 2022

The Earth’s lithosphere, atmosphere, and biosphere interact with one another primarily at the surface of our planet, with the lithospheric coupling arising primarily from large-scale, long-period topographic evolution driven by deep mantle processes. Global numerical modelling of mantle convection in 3D with mobile continents in a modern plate tectonic regime has been previously demonstrated (Coltice et al., 2019). Improvements on such models can provide a useful tool for investigating the effects of large scale and long term changes in Earth’s tectonic regime on the surface.

We present preliminary results in 2D spherical geometry using newly implemented additions to the existing mantle convection code StagYY (Tackley, 2008). A free surface representation using a marker chain enables higher surface resolution and the possibility of future implementation of surface processes on a global scale (Duretz et al., 2016). Initial conditions based on previous work on self-consistent continent generation enables modelling of continents with realistic rheology and structure (Jain et al., 2019).

The successful development of these tools enables further study of the evolution of the surface as a result of tectonic changes. A key goal is the modelling of the transition from a pre-plate tectonic regime to modern plate tectonics, as may have occurred in the Neoproterozoic (Stern, 2018). The tectonic changes of this period were also associated with other radical changes in the atmosphere and biosphere, such as the Cryogenian glaciations, and the Cambrian explosion. Models of topographic evolution may be used in conjunction with climate models or models of biological evolution to study the coupling between these systems as a part of the emerging field known as Biogeodynamics (Gerya et al., 2020).
Quantifying emerging patterns of greening and browning in the Himalayan region
Authors: Singh Kanwal Nayan , Nocke Thomas , Shukla Roopam , Joshi Pawan Kumar , Agarwal Ankit , Kurths Jürgen
Published: March 2022

Himalayan region is a critical part of the globe. In recent years,  vegetation cover in this region is undergoing considerable changes attributed ongoing to climatic and anthropogenic factors. The present study aims to capture the interannual vegetation changes over 19 years and explore how topographic and climatic variables contribute to the observed changes. Satellite-derived Normalized Difference Vegetation Index (NDVI) dataset (2001–2019) was used to examine the spatio-temporal patterns of vegetation in Uttarakhand state in the Indian western Himalayas. Further analysis explored variation across elevation, temperature, precipitation, and vegetation types. Most parts of the Uttarakhand region experienced increasing NDVI trends, particularly in the Needleleaved Evergreen and Broadleaved Deciduous forest types; however, negative trends were observed in shrublands.
Data-driven modelling of canopy greenness dynamics reveals short- and long-term meteorological effects on phenology
Authors: Liu Guohua , Winkler Alexander J. , Migliavacca Mirco
Published: March 2022

Vegetation phenology, measured as the seasonal canopy greenness signal, is highly sensitive to present as well as past meteorological conditions. However, how these meteorological conditions affect canopy greenness on the short-term and the long-term (memory effects from previous climatic conditions) is still unclear, and modeling these effects on vegetation phenology in particular is a major challenge. In this study, we develop data-driven models to identify the influence of short- and long-term memory effects of temperature, radiation and water availability on the canopy greenness using data-adaptive approaches, such as random forest regression (RF) models and Long Short-Term Memory (LSTM) setups. We use the Green Chromatic Coordinate (GCC) from the PhenoCam network as a proxy for canopy greenness and meteorological observations from the DayMet dataset. We find that the importance of these short-term vs. long-term memory effects on canopy greenness differs across the plant functional types. For deciduous forest, roughly the last 10 days of minimum temperature and the photoperiod are identified to be the key drivers of canopy greenness, while in grasslands also the water availability and its long-term memory are important factors in controlling the seasonal course of canopy greenness. Additionally, our results show that an LSTM approach with embedded predictor memory effects outperforms a model without the memory effect (such as RF) in simulating the canopy greenness, and captured memory length varies across meteorological predictors with short temperature and radiation memory and long water memory. Our findings highlight the importance of memory effects of environmental conditions throughout the season across different time scales for canopy greenness and the fundamental role of water availability, often neglected in phenological models. Accounting for these effects in such data-driven approaches opens up new avenues for improving the representation of phenological processes in models, such as Earth system models.
Asymptotic behavior of the forecast-assimilation process with unstable dynamics
Authors: Crisan Dan , Ghil Michael
Published: March 2022

Extensive numerical evidence for real and/or simulated data shows that the assimilation of observations has a stabilizing effect on unstable dynamics in numerical weather prediction and elsewhere.  In this talk, I will discuss mathematically rigorous considerations showing why this is so. In particular we prove that the expected value of the Wasserstein distance between the forecast-assimilation (FA) process starting from the true initial conditions and FA process wrongly initialized can be controlled uniformly in time. Under suitable circumstances, the number of observations required to achieve this stabilization can be much smaller than the number of model variables. In particular, it suffices to observe the model's unstable degrees of freedom. 
Geological mapping and Active tectonics from UAS-HR-DTM and PSInSAR: Case examples in the Longitudinal Valley and the Coastal Range (E. Taiwan)
Authors: Deffontaines Benoit , Chang Kuo-Jen , Magalhaes Samuel , Serries Gregory , Fortunato Gerardo
Published: March 2022

Taiwan island is the result of the active rapid collision of both Eurasian and Philippine Sea Plates with an annual average convergence rate close to 10 cm.y-1. The relief of Taiwan is composed of the metamorphic slate belt of the Backbone Range (also called Central Range) and to the east the Coastal Range mainly characterized by volcanic affinity. In between those, lay the Longitudinal Valley (125km long and N020°E trending) which is the active crustal suture zone. The latter presents both inter-seismic creeping displacement (Champenois et al., 2013) and was hit by 7 major earthquakes of magnitudes larger than 5 during the last 70 years. It highliths the geohazards importance of this area for any Taiwan citizens.

 

In order to better constrain the seismic hazards and the earthquake cycles of the place, we settled several years ago numerous UAS surveys above the Coastal Range and the Longitudinal Valley (E. Taiwan) and acquired so many high-resolution photographs using several drones flying at 350 meters above the ground. After photogrammetric processing, we calculate both (1) a high-resolution Digital Elevation Model (UAS-HR-DEM) that takes into account buildings and vegetations, and (2) a Digital Terrain Model (UAS-HR-DTM) corresponding to the ground. Our ground validation (GCP’s) leads us to get 7cm planimetric resolution (X, Y) and below 40cm vertical accuracy. This UAS-HR-DTM combined with field work and a detailed morphostructural analysis permit us to map into much details the structures and consequently to up-date the pre-existing geological mappings (e.g. CGS geological maps, Lin et al., 2009 ; Shyu et al., 2005, 2006, 2007, 2008). Then we combined our new structural scheme with various geodetic data (levelings, GPS…) and PSInSAR results (Champenois 2011, and Champenois et al., 2013) to locate, characterize and quantify the active tectonic structures, taking into account previous works (e.g. Yu et al., 1997; Lee et al., 2008; Hsu et al., 2009; Huang et al., 2010…). We then precise structural geometries and some geological processes as well as the location of active folds and active faults during the PSInSAR monitoring time-period.
Seismic Exploration and monitoring of geothermal reservoirs usiNg distributed fibre optic Sensing - the joint project SENSE
Authors: Krawczyk CharLotte , Ehsaniezhad Leila , Wollin Christopher , Hart Johannes , Lipus Martin
Published: March 2022

For a successful operation of energy or resources use in the subsurface, exploration for potential reservoir or storage horizons, monitoring of structural health and control of induced seismic unrest are essential both from a technical and a socio-economic perspective.  Furthermore, large-scale seismic surveys in densely populated areas are difficult to carry out due to the effort required to install sources and receivers and are associated with high financial and logistical costs.  Within the joint project SENSE*, a seismic exploration and monitoring approach is tested, which is based on fibre-optic sensing in urban areas.

Besides the further development of sensing devices, the monitoring of borehole operations as well as the development of processing workflows form central parts of the joint activities. In addition, the seismic wave field was recorded and the localisation of the cables was tested along existing telecommunication cables in Berlin. Further testing of measuring conditions in an urban environment was also conducted along an optic fibre separately laid out in an accessible heating tunnel.

We suggest a workflow for virtual shot gather extraction (e.g., band pass filtering, tapering, whitening, removal of poor traces before and after cross-correlation, stacking), that is finally including a coherence-based approach.  The picking of dispersion curves in the 1-7 Hz frequency range and inversion yield a shear wave velocity model for the subsurface down to a. 300 m depth.  Several velocity interfaces are evident, and a densely staggered zone appears between 220-270 m depth.  From lab measurements a distributed backscatter measurement in OTDR mode shows that high reflections and moderate loss at connectors can be achieved in a several hundred m distance.  Depending on drilling campaign progress, we will also present first results gained during the borehole experiment running until February 2022.

* The SENSE Research Group includes in addition to the authors of this abstract Andre Kloth and Sascha Liehr (DiGOS), Katerina Krebber and Masoud Zabihi (BAM), Bernd Weber (gempa), and Thomas Reinsch (IEG).
Releasing corona ions into natural fog
Authors: Harrison Giles , Marlton Graeme , Ambaum Maarten , Nicoll Keri
Published: March 2022

Charge influences the properties of liquid droplets, such as their evaporation rates, hydrodynamic stability and sticking probabilities in droplet-droplet collisions. Introducing additional charge into an assembly of droplets therefore provides a possible method of influencing the droplet properties, and, in the case of a fog or cloud, a route to weather modification. The effect of charging on natural droplets has been investigated by releasing additional unipolar and bipolar ions into a natural surface fog, from both within the fog at the surface and above the fog, using an Uncrewed Aerial Vehicle (UAV). Droplet properties were monitored before and after the ion release using optical methods, together with the atmospheric electric field using a field mill. The atmospheric electric field measurements robustly demonstrate the present of the additional ions. Further, changes in the fog properties apparent when the additional ions are introduced are discussed.
Subduction hints from the northeastern Mediterranean Sea
Authors: Bertone Nicolò , Bonini Lorenzo , Colin Eugenia , Del Ben Anna , Brancatelli Giuseppe , Camerlenghi Angelo , Forlin Edy , Pini Gian Andrea
Published: March 2022

The eastern Mediterranean is shaped by the interaction between the African, Arabian, and Eurasian plates resulting in a complex tectonic framework. The Hellenic subduction is well documented and studied but, the northeast corner of the eastern Mediterranean Sea remains enigmatic. It is a tectonically active region where different plate boundary conditions coexist (i.e., oceanic subduction, continental collision, extension, and strike-slip movements). An active and tsunamigenic system has been interpreted west and east of Cyprus by using deep seismic reflection lines. Vintage deep-penetrating seismic reflection profiles of the Mediterranean Sea project (MS project) - acquired during the ’70 - were re-analyzed and merged with a synthesis of available subsurface data from the scientific literature. This study focuses on two transects (MS53 and MS56) that cross the major offshore structures (i.e., Florence Rise, Latakia Ridge, and Kyrenia Ridge) from north to south. The western transect (MS53) shows the Herodotus oceanic crust subducting northward beneath the Eurasian plate. The Florence Rise is the leading edge of the system, and the Antalya Basin is its forearc basin. Close to the Turkish coast, a buried block seems to act as a backstop for the offshore system, and north of it, some out-of-sequence thrusts have been interpreted. The strain is partitioned between the Florence Rise and the Taurides front. The eastern transect (MS56) crosses the Latakia Ridge, i.e., the northern boundary of the Levant Basin, where shortening is greater than in the western area. The seismic line continues northward into the Cyprus – Latakia Basin, crossing the Kyrenia Ridge, and reaching the Turkish coast. On the seismic section, we interpreted the Mesozoic subduction front now hindered by strike-slip movements on the Latakia Ridge. Another prominent transpressive structure is the Kyrenia Ridge, which is interpreted as an active structure with a well-imaged thrust system in front of it. The seismic sections were depth converted to provide a regional geologic model for the northeastern Mediterranean Sea. Active subduction fronts, which are only partially imaged, were structurally modeled and then crosschecked with previous studies to better constrain their geometry. In the northeastern Mediterranean Sea, a plate boundary is buried offshore with active subduction west of Cyprus and mainly transpressional tectonics to the east. A better understanding of its nature and kinematics would be useful to assess the tsunami hazard in this area.
Climate change induced impacts on hydrological extremes at the catchment scale: case of Wadi Siliana (North western Tunisia)
Authors: EL Ghoul Imen , Tliha Fatma , Sellami Haykel , Mounir Kaoutar , Khlifi Slaheddine , Vanclooster Marnik
Published: March 2022

High and low flows are hydrological flow extremes threatening human being by causing floods and droughts. They are caused by meteorological extremes and human activities.  Changes in meteorological conditions will inevitably impact the frequency of hydrological extremes and exacerbate their associated hydrological impacts.

This study focuses on modelling projected change in both frequency and magnitude of flow extremes as consequence to change in climate condition in the Siliana catchment in Tunisia. The SWAT and HBV hydrological models were calibrated using historical data and fed with an ensemble of high resolution CORDEX climate models. Results project a warmer and drier hydrometeorological conditions in the Siliana catchment. The precipitation is expected to decrease in the future by an average of 10% in dry season and 12% in wet season. In contrast, temperature is expected to increase by an average of +2°C in dry season and 1.8°C in wet period.

The two models show that while magnitude and frequency of high flows are expected to decrease, low flows frequency is expected to increase which affirms that the Siliana catchment is likely to experience severe hydrological conditions with reduction in water availability and increase in drought frequency.
Recent changes in the probability of agrometeorological risks over the southern Mediterranean region, and potential impacts on crop growth 
Authors: Mirgol Behnam , Dieppois Bastien , Northey Jessica , Eden Jonathan , Jarlan Lionel , Tramblay Yves , Mahé Gil
Published: March 2022

Climate change, as one of the most significant challenges that humans currently face, is defined as a shift in climate patterns in response to increasing greenhouse gas emissions in the atmosphere. Notably, climate change has been associated with global warming temperature, regional changes in rainfall patterns and extreme events. Such changes in climate are emerging at a time of rapid growth for many economies in the southern Mediterranean region, stressing the need to understand their impacts on sectors better. In addition, unlike other regions, very little research has been undertaken to understand how climate has changed (and will change) over the area and how such changes may affect the agricultural sector. Here, using trend analysis and the non-stationary generalized extreme value (GEV) model, we examine whether the probability of extreme agrometeorological risks has changed over the last 60 years in response to the globally warming temperature. We then quantify the magnitude of such changes over different phenological stages for wheat, maize and rice, highlighting the most vulnerable areas to extreme conditions in the southern Mediterranean region. Extreme agrometeorological risks are estimated using multiple state-of-the-art observational and reanalyzed daily datasets (REGEN, BERKELEY, CHIRPS, ERA5 and ERA5-land), and using multiple drought indices (standardized precipitation-evapotranspiration index [SPEI], standardized antecedent precipitation-evapotranspiration index [SAPEI], frequency and duration of dry spells) and heat stress indices (wet-bulb globe temperature [WBGT], effective temperature, discomfort index, heat index, frequency and duration of hot and cold spells). As such, this study, identifying areas in which crop growth and productivity are becoming particularly threatened by the increasing frequency and duration of extremes, provides vital evidence for climate change adaptation and mitigation plans in the southern Mediterranean region. 
Conduits feeding new eruptive vents at Fagradajsfjall, Iceland, mapped by high-resolution ICEYE SAR satellite in a daily repeat orbit
Authors: Drouin Vincent , Tolpekin Valentyn , Parks Michelle , Sigmundsson Freysteinn , Leeb Daniel , Strong Shay , Hjartardóttir Ásta Rut , Geirsson Halldór , Einarsson Páll , Ófeigsson Benedikt Gunnar
Published: March 2022

Using ground deformation measurements of high spatial and temporal resolution SAR, the understanding of new vents created during volcanic eruptions can be improved with 3D mapping of the activated shallow magma plumbing system. Interferometric analysis of radar data from ICEYE X-band satellites with daily coherent ground track repeat (GTR) provides unprecedented time series of deformation in relation to the opening of 6 eruptive vents over 26 days in 2021, at Fagradalsfjall, Iceland. Unrest started in this location at the end of February and tens of thousands of earthquakes were recorded during the following four weeks. The seismicity was linked to gradual formation of a magma-filled dike in the crust and triggered seismicity along the plate boundary. On 19 March, an eruptive fissure opened near the center of the dyke. New vents and eruptive fissures opened on the 5th, 7th, 10th, and 13th April. The daily acquisition rate of the ICEYE satellite facilitated the observation of the ground openings associated with each new vents. Each event can be observed individually and with minimal loss of signal caused by new lava emplacement, which would occur if images were acquired at a slower rate. Being able to retrieve deformation near the edge of the fissure ensures that we have the optimal constraints needed for modelling the subsurface magma path. The ICEYE dataset consists of Stripmap acquisitions (30x50km) in the period 3-21 March, and Spotlight acquisitions (5x5 km) from 22 March and onward. Images have a resolution of about 2 m x 3 m, and 0.5 m x 0.25 m, respectively. The descending 1-day interferogram covering each individual event is used to invert for the distributed opening along the dike plane. We find that each fissure was associated with opening of up to 0.5 meters in the topmost 200 m of crust. The conduits propagated vertically at least 50–80 m/h. The new fissure locations were influenced by local conditions and induced stress changes within the shallow crust.
Developing an operational impact-based flood forecasting system for the Greater Horn of Africa region
Authors: Alfieri Lorenzo , Libertino Andrea , Campo Lorenzo , Ghizzoni Tatiana , Masoero Alessandro , Menchise Chiara , Poletti Maria Laura , Gabellani Simone , Rossi Lauro , Rudari Roberto , Rossi Luca , Mouakkid Soltesova Katarina , Gatkuoth Kai , Ouma Jully , Amdihun Ahmed , Nshimirimana Godefroid , Tramblay Yves , Massabò Marco
Published: March 2022

Every year Africa is affected by extreme weather related hazards which, combined with high levels of vulnerability and increasing population exposure, result in considerable impacts to people and assets. Here we present recent activities in the development of an African Multi Hazard Early Warning System for disaster risk reduction, a multi-year project funded by the Italian Government through the United Nations Office for Disaster Risk Reduction. After a brief introduction on the main project goals, the presentation will give insights on one of its key activities, focused on strengthening impact-based flood monitoring and forecasting capabilities for the Greater Horn of Africa region. This ongoing activity foresees the implementation of a probabilistic impact-based flood forecasting system based on the Flood PRObabilistic Operative Forecasting System (Flood-PROOFS) developed by CIMA Foundation and run routinely in several world regions. Flood-PROOFS has as its core the Continuum distributed hydrological model, which takes as input meteorological variables and several other static and dynamic data to simulate the hydrological processes in the focus region. For this application, Continuum was set up at hourly time step on 17 hydrologically consistent domains, with grid resolutions ranging between 250m and 3.3km, ultimately covering a surface of 6.82 million km2. Given the relative scarcity of in situ data, model calibration is based on observed river discharges at 130+ river gauging stations, as well as on GLEAM satellite evaporation and soil moisture products. A 40-year continuous hydrological reanalysis is produced by forcing the model with ERA5 atmospheric reanalysis bias corrected for precipitation and temperature. Daily runs include model updates with satellite precipitation estimates and 5-day forecasts forced by the Global Forecast System. Ongoing activities are expanding the current deterministic setup to ensemble forecasts, as well as coupling hydrological forecasts in real time with state of the art global inundation maps, to estimate impact-based flood warnings by integrating information on exposure, vulnerability and coping capacity. Such information is used in the operational monitoring and early preparedness versus impending disasters, as well as to design prevention and mitigation measures, which is fundamental to prioritize and optimize the use of available resources for disaster response.
Timing of Tectonic and Magmatic Events in the Philippine Sea Plate since 50 Ma from High-Resolution Magnetostratigraphy of IODP Site U1438
Authors: Maffione Marco , Morris Antony
Published: March 2022

The Izu-Bonin-Mariana (IBM) subduction system is a key natural laboratory providing fundamental insights into subduction dynamics and the evolution of associated upper plate magmatism. To investigate the processes associated with subduction initiation and the subsequent evolution of the Philippine Sea plate, International Ocean Discovery Program (IODP) Expedition 351 recovered a complete sedimentary sequence and the top of the underlying volcanic basement at Site U1438 located in a rear-arc position. This offers a unique opportunity to study for the first time and in extreme detail the styles, products, and timing of the volcanic events that marked the emplacement, growth, and demise of the Kyushu-Palau volcanic arc within the IBM system. Here we report a magnetostratigraphy for Site U1438 based on ~60,000 remanence directions isolated from 1063 archive half-core sections and 429 discrete specimens. This identified 112 well-constrained magnetic reversals that may be correlated with the geomagnetic polarity timescale. When combined with additional biostratigraphic and geochronological constraints, this allows construction of a high-resolution age model for Site U1438 and the determination of changes in sedimentation rates during the evolution of the Kyushu-Palau arc. These age constraints show that following subduction initiation at ~52 Ma, diffuse volcanism in both the forearc and rear-arc preceded the initial emplacement of the Kyushu-Palau arc at 44.2 Ma, which then grew through four compositionally distinct eruptive phases until 29.2 Ma. Rollback of the Pacific slab then triggered rifting of the arc (29.2-24.3 Ma), leading to back-arc spreading in the Shikoku and Parece-Vela basins.
Footprint of large scale expansion of wind power in productive boreal forests – forests under a zero-emission strategy
Authors: Neumann Wiebke , Bjärstig Therese , Thellbro Camilla , Svensson Johan
Published: March 2022

The increasing demand of emission-free energy enhances the footprint of wind power on landscapes worldwide. Wind power establishments claim considerable areas given their establishment sites and connected infrastructure. Being a major (but late arriving) land-use actor, onshore wind power expands in a landscape context already shaped by other land uses, thereby becoming directly a competitor for area. Being at forefront within the European Union, Sweden in northern Europe has ratified ambitious environmental goals to meet net zero emissions of greenhouse gases by 2045. This asks for substantial expansion in renewable energy sources nationwide, particularly of wind power. In practice, suggested future wind power establishments claim about 3.5% of the total national land surface in Sweden but higher shares in forest-dominated regions. Within the Swedish environmental strategy, forests, however, are key players to provide also other products and services to mitigate impacts of climate change as well as to preserve biodiversity. Notably, a land demand of about 3.5% by wind power is comparable to the share of all formally protected Swedish forestlands below the mountain forest border, which currently is heavily debated due to the experienced loss of forestland for wood biomass production. This makes wind power establishment in forest landscape a serious competitor for space and for meeting different forest goals.

Using Sweden as a case, we quantify the amount of forests in relation to their productivity, landownership (state, company or private) and nature conservation value that we expect to convert into wind power land following the recent national strategy for wind power expansion based on current wind power distribution in Sweden. Our preliminary results suggest a considerable conversion of productive forestland into wind power land, particularly in the southern boreal landscape. Preliminary findings also indicate landowner differ to which degree their productive forestland without conservational value likely become wind power land.  

Our results emphasized the need for regional context-specific landscape planning in order to allow for both forests development and utilization meeting different environmental goals, including wind power and other interests.
Net water-mass transport through the Strait of Gibraltar and the Turkish Strait 
Authors: Garcia-Garcia David , Vigo Isabel , Trottini Mario , Vargas Juan , Sayol Juan Manuel
Published: March 2022

The Mediterranean is connected to the Black Sea through the Turkish Straits, and to the Atlantic Ocean through the Strait of Gibraltar. The hydrological cycle of the Mediterranean-Black Sea system is driven by fresh water exchanges between the atmosphere, continents and oceans, and by salty water mass exchange among the ocean basins. In this study, we estimate the water-mass fluxes through these straits as  residuals in the water balance equation. To do so, the freshwater fluxes are estimated from the time-variable gravity fields inferred from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On satellites, and precipitation and evaporation data from ERA5 atmospheric reanalysis products. This study covers the 18 years period from 2002 to 2020. In the Black Sea, rivers introduce an average water volume of 391 ± 12 km3/year, one third of which escape through the atmosphere and two thirds go to the Mediterranean Sea. In the latter, 1787 ± 23 km3/year are lost via net evaporation. The rivers runoff (502 ± 27 km3/year), and the inflow of Atlantic waters (1020 ± 56 km3/year; 0.0323 ± 0.0018 Sv), finally restore the Mediterranean water budget. The balance is not reached instantaneously, and this delay introduces a seasonal variability in all the fluxes. In particular, the net water flux from the Atlantic Ocean increases up to 2660 ± 111 km3/year in August/September, and reverses to –407 ± 140 km3/year in April/May. On top of the climatology, the mean annual Atlantic water flux varies significantly in time ranging from 706 to 1262 km3/year.

The work of DGG, IV, MT and JV was partially supported by Spanish Project RTI2018-093874-B-100 funded by MCIN/AEI/10.13039/501100011033,  DGG and IV were partially supported by Grant PROMETEO/2021/030 (Generalitat Valenciana) and JMS was supported by the Generalitat Valenciana  and the European Social Fund under Grant APOSTD/2020/254.
Quality assessment of the different Possible Source Region (PSR) algorithms
Authors: Kusmierczyk-Michulec Jolanta , Tipka Anne , Schoemaker Robin , Kalinowski Martin
Published: March 2022

The operational Atmospheric Transport Modelling (ATM) system deployed and used at CTBTO produces source receptor sensitivity (SRS) fields, which specify the location of the air masses prior to their arrival at any radionuclide station of the International Monitoring System (IMS) network. The ATM computations support the radionuclide technology by providing a link between radionuclide detections and the regions of their possible source. If an IMS station detects an elevated level of radionuclide, the ATM in a backward mode is used to identify the origin of air masses. In the case of a single detection, the FOR (Field of Regard) is computed, which denotes the possible source region for a material detected within one single sample. On some occasions, multiple detections occur at one or more IMS stations. Depending on the nature of these detections and on prevailing meteorological conditions, it is possible that all these detections may come from a unique source. For this case, the PSR (Possible Source Region) is computed for each grid point in space and time by calculating the correlation coefficients between the measured and simulated activity concentration values (SRS fields). Obviously, the result will depend on the algorithms used for that purpose. Currently, in the WEB-connected GRAPhics Engine (WEB-GRAPE) software, designed and developed by the International Data Centre (IDC) to visualize and post-process of the ATM results, three different PSR algorithms are implemented: two based on the Pearson’s correlation coefficient and one based on the Spearman’s rank correlation coefficient. 

 

For the quality assessment of these PSR algorithms, subsets of datasets developed in the framework of the 2nd and 3rd ATM Challenge will be used, which satisfy the condition that the agreement between Xe-133 measured and simulated values is very good. In this sense, the selected samples will represent “ground truth” data, where the contribution from all dominated sources (e.g. Isotope Production Facilities or Nuclear Power Plants) is included. For these selected samples, the results produced by the different PSRs algorithms will be assessed, taking into account both spatial and temporal variations.  

 
A new compositional estimate for refractory lower continental crust
Authors: Emo Robert , Kamber Balz , Downes Hilary , Caulfield John
Published: March 2022

Compared to the well-studied upper continental crust, the composition of the lower crust is much more poorly constrained. Geophysical constraints and geochemical data from granulite xenoliths indicate that the lower crust is, on average, mafic and depleted in most incompatible elements, including the heat-producing elements (HPE). However, the extent of this depletion is not well known. The large uncertainties associated with lower crustal estimates have important implications for the Earth’s evolution, as the lower crust is often proposed to be a “hidden reservoir” (e.g., for unradiogenic Pb) needed to close mass balance discrepancies for the Bulk Silicate Earth.

In this study, we analysed granulite xenoliths from Queensland, eastern Australia, and the Kola Peninsula, northwest Russia, using a reconstitution approach that corrects for host magma contamination. This method also provides detailed insight into which minerals control elemental distribution and concentrations of the xenoliths. The major element compositions of both suites of granulite xenoliths highlight their mafic nature, with SiO2 contents similar to previously published estimates. However, the concentrations of the most incompatible elements, including the large ion lithophile elements (LILE) and HPE, are very low. Some elements are more depleted by an order of magnitude than the most popular composites used in the literature. Zircon and monazite are rare in these mafic granulites, while apatite and rutile have relatively low Th and U concentrations. The absence of hydrous silicates (e.g., mica and amphibole) and the relatively high anorthite contents of feldspar in the xenoliths is a controlling factor in the low LILE concentrations, particularly for Rb and Cs. If this composition is representative of typical lower continental crust, then such highly refractory compositions limit the ability of the lower crust to act as a significant contributor for planetary mass balance considerations because it does not contain enough Pb, Nb, Ta, Cs and Rb to balance other inventories of the differentiated bulk silicate Earth.
Testing effects of deviations from theory for beerkan infiltration experiments
Authors: Iovino Massimo , Bagarello Vincenzo , Dohnal Michal , Lai Jianbin
Published: March 2022

The beerkan infiltration experiment is carried out by inserting the ring a short depth into the soil and establishing a positive head of water on the infiltration surface for at least a part of the run. Nevertheless, the data are analyzed by assuming a fully unconfined infiltration process (ring insertion depth, d = 0) and a null ponded depth of water (H = 0). The influence of ring insertion and ponded water on an infiltration process of 2 hours sampled every minute was tested in this numerical investigation. Five soils varying from sand to silt loam, three ring radii (5 - 15 cm) and the beerkan specific range of values for both d and H, that is between 0 and 1 cm were considered. The differences between the theoretical (d = H = 0) and the practical (d = H = 1 cm) setups varied from -10.4% and +8.6% for the mean infiltration rate and from -10.2% to +8.3% for the final cumulative infiltration. These differences were small and they decreased by considering a soil dependent ring radius. In particular, nearly negligible differences were detected using a small ring in coarse-textured soils and a large ring in fine-textured soils. In the coarser soils, inserting the ring and establishing a ponded depth of water did not alter appreciably the estimated coefficients of the two-parameter infiltration model with the Cumulative Linearization method since these coefficients differed between the theoretical and practical setups by no more than 9.2%; while in fine soils, linearization could not be possible regardless of the considered setup or it was the use of d = H = 1 cm instead of d = H = 0 that impeded a convincing linearization of the data. In conclusion, the satisfactory correspondence, in many circumstances, between the theoretical and the practical beerkan infiltration experiment reinforced the interest for this simple experiment as a practical means to collect infiltration data in the field. Other numerical tests should be carried out to reach more general conclusions, also considering heterogeneous soil conditions. The numerical results should represent the first step of a wider investigation that also includes laboratory and field experiments.
Systematic Validation of Ensemble Cloud-Process Simulations using Polarimetric Radar Observations and Simulator over the NASA Wallops Flight Facility
Authors: Matsui Toshi , Wolff David , Lang Stephen , Mohr Karen
Published: March 2022

The BiLateral Operational Storm-Scale Observation and Modeling (BLOSSOM) project was initiated in order to establish routine storm-scale polarimetric radar observations and cloud-process modeling at NASA GSFC Wallops Flight Facility (WFF), where various continental and maritime convective systems are being observed. The ultimate goals of BLOSSOM include:

Establish a long-term super site to improve understanding of cloud physical states and processes over the WFF site through bilateral storm-scale observations and modeling.

Provide routine meteorological large-scale forcing input to support cloud-resolving models (CRMs), large-eddy simulation (LES) models, and single-column models (SCMs) for the improvement of cloud microphysics and convection parameterizations.

Provide routine storm-scale cloud-precipitation simulations as well as storm-scale measurements using ground-based polarimetric Doppler radar and in-situ data.

Collect and organize value-added data from the cloud-process simulations, ground-based polarimetric radar, and NASA satellite observations for the community.

 

This presentation will highlights a few case studies to test the concept of BLOSSOM, including the creation of ensemble large-scale forcing, configuring and performing cloud-process simulations with different bulk microphysics using the Goddard Cumulus Ensemble (GCE) model, organizing and streaming NASA S-band dual-POLarimetric radar (NPOL) and other WFF instrument data, and validating the ensemble GCE simulations through formulating statistical composites by comparing observed and simulated polarimetric radar signals using the POLArimetric Radar Retrieval and Instrument Simulator (POLARRIS). Different spatial grid spacing (1km vs 250m) of the GCE simulations will be also evaluated to examine resolution impact on representing time-series as well as time-integrated composites of polarimetric radar signals.
Estimation of point spread function for unmixing geological spectral mixtures
Authors: Sahoo Maitreya Mohan , Pattathal Vijayakumar Arun , Herrmann Ittai , Mathew Shibu K. , Porwal Alok
Published: March 2022

Geological materials are mixtures of different endmember constituents with most of them having particles smaller in size than the path length of incident light. The obtained spectral response (reflectance) from such mixtures is nonlinear which can be attributed to multiple scattering of light and the receiver sensor’s height from the incident surface. Assuming a sensor’s fixed instantaneous field of view (IFOV), variation in its field of view (FOV) by shifting its height affects the spatial resolution of acquired spectra. We propose to estimate the point spread function (PSF) for which the spectral responses of fine-resolution pixels acquired by a sensor are mixed to produce a coarse-resolution pixel obtained by the same. Our approach is based on the sensor’s unchanged IFOV obtaining spectral information from a smaller ground resolution cell (GRC) at a lower FOV and a larger GRC with an increased sensor’s FOV. The larger GRC producing a coarse resolution pixel can be modeled as a gaussian PSF of its corresponding center and neighboring fine-resolution subpixels with the center exerting the maximum influence. Extensive experiments performed using a point-based sensor and a push broom scanner revealed such variational effects in PSF that are dependent on the sensor’s FOV, the spatial interval of acquisition, and optical properties. The coarse-resolution pixels’ spectra were regressed with their corresponding fine-resolution subpixels to provide estimates of the PSF values that assumed the shape of a two-dimensional Gaussian function. Constraining these values as sum-to-one introduced sparsity and explained variability in the spectral acquisition by different sensors.  The estimated PSFs were further validated through the linear spectral unmixing technique. It was observed that the fractional abundances obtained for the fine-resolution subpixels convolved with our estimated PSF to produce its corresponding coarse-resolution counterpart with minimal error. The obtained PSFs using different sensors also explained spectral mixing at different scales of observation and provided a basis for nonlinear unmixing integrating spatial as well as spectral effects and addressing endmember variability. We performed our experiments with various coarse-grained and fine-grained igneous and sedimentary rocks under laboratory conditions to validate our results which were compared with available literature. 
Blowing in the wind: a review of wind and air- pressure-related effects on soil gas transport 
Authors: Maier Martin , Osterholt Laurin , Schindler Dirk
Published: March 2022

Gas transport in the soil is dominated by molecular diffusion in the air-filled pore network. A study in the 1970s could show that Radon emissions from soil increased during the passage of a low-pressure system which temporarily enhanced soil gas transport rates (Clements & Wilkening, 1974). Enhanced wind speed near the soil surface was also found to speed up gas transport rates in the soil (Kimball & Lemon, 1971). Further studies followed confirming the observations that wind and substantial atmospheric pressure changes have the potential to affect soil gas transport, including studies conducted in snow and firn, deserts, forest soil, arid systems, and soils near water saturation. Especially during recent years, wind and air- pressure-related effects on soil gas transport received increasing attention, with diverse concepts and methodologies, and also a wider ecological relevance.

While the slow (hours) and relatively large atmospheric pressure changes (up to 50 hPa) reported in Clements & Wilkening (1974) cause a kind of steady piston flow in the soil, the effect in Kimball & Lemon, (1971) was explained as the result of dynamic wind-induced pressure fluctuations, which are much smaller in amplitude (2-20 Pa) and occur at higher frequencies (0.1-1.0 Hz). Although the effect of wind-induced pressure fluctuations on gas transport in the soil has been confirmed by a few studies, there is still only little knowledge about the underlying processes. Additional effects between the pure “static piston flow “and the dynamic pressure fluctuations certainly occur. Different approaches and methodologies were used to derive estimates for the impact (if quantified) of air pressure fluctuations on soil gas transport, which makes inter-study comparisons complicated and limits further progress.

We overview relevant studies, their methods, concepts and explanations to identify research gaps and develop a plan for further research concepts.

Clements, W. E., & Wilkening, M. H. (1974). Atmospheric pressure effects on 222 Rn transport across the Earth-air interface. Journal of Geophysical Research, 79(33), 5025–5029. https://doi.org/10.1029/jc079i033p05025

Kimball, B., & Lemon, E. (1971). Air Turbulence Effects Upon Soil Gas Exchange. Soil Science Societyof America Journal 35(1), 16–21. https://doi.org/10.2136/sssaj1971.03615995003500010013x

 
Capturing future soil-moisture droughts from irregularly distributed ground observations
Authors: Bessenbacher Verena , Gudmundsson Lukas , Seneviratne Sonia I.
Published: March 2022

With a rapidly warming climate, future droughts are predicted to increase in frequency, duration, extent, and severity for many regions, whilst uncertainty of drought predictions in CMIP6 ensembles remains high. Monitoring the occurrence of agricultural and ecological droughts (i.e. soil moisture droughts), in present and future climate is therefore vital. However, available drought monitoring products do not use information from soil moisture ground observations, although those are the only observations available that extend into the vegetation-relevant root zone.

A central challenge of these ground observations (included in the international soil moisture network ISMN) is that they are not evenly distributed across the globe, favoring Europe and the US. Upscaling these observations to global soil moisture estimates for drought monitoring can lead to underrepresented areas suffering from misrepresentation of drought occurrences. Installing new measurement stations is costly, therefore placing them should focus on alleviating the problem of these underrepresented regions and ecosystems. 

We apply a statistical learning method to identify under-represented ecosystems and environmental conditions to inform future station placement. We overlay these maps with future drought occurrence maps and drought uncertainty maps to scan for regions that are especially vulnerable in the future given the current station net. The analysis is built around an up-scaling approach where the model is trained to predict station-level soil moisture as a function of gridded atmospheric precipitation and temperature. The resulting model can be used to estimate soil moisture at locations without observations. For doing so we rely on the CMIP6 ensemble as a laboratory, which enables us to create virtual soil moisture stations based on continuously available soil moisture simulations. 

The first results show that strategically placing new soil moisture observation stations where the climate space is most under-sampled leads to an increase of drought estimation accuracy. We are planning to further investigate hypothetical station configurations and follow up with the question of where future “station measurement years” should optimally be distributed around the globe to increase drought monitoring from ground observation in areas with low station coverage but high drought risk and high uncertainty in future projections. 