bluuebunny/crossref_metadata_2025 huggingface dataset:
Revisiting the storage-reliability-yield concept in hydroelectricity
Authors: Efstratiadis Andreas , Tsoukalas Ioannis , Koutsoyiannis Demetris
Published: March 2021

The storage-reliability-yield (SRY) relationship is a well-established tool for preliminary design of reservoirs fulfilling consumptive water uses, yet rarely employed within hydropower planning studies. Here, we discuss the theoretical basis for representing the trade-offs between reservoir size and expected revenues from hydropower production, under uncertain inflows, by taking advantage of the stochastic simulation-optimization approach. We also demonstrate that under some assumptions, the complex and site-specific problem, mainly induced by the nonlinearity of storage-head-energy conversion, can be significantly simplified and generalized as well. The methodology is tested across varying runoff regimes and under a wide range of potential reservoir geometries, expressed in terms of a generic shape parameter of the head-storage relationship. Based on the outcomes of these analyses we derive empirical expressions that link reliable energy with summary inflow statistics, reservoir capacity and geometry.
High-Altitude Experimental Test of the Wind-Wave Interaction Models
Authors: Babanin Alexander , Palenque Eduardo
Published: March 2021

We present the idea to experimentaly test the empirical models used in fluid mechanics. The models consider that the waves develop due the wind energy trasferred from the air to the urface of the water. However, all of those models were validated considering data at sea level, with effectively fixed air density. Here we propose to test the adjustment of the empirical coefficients studying the waves generated in Lake Titikaka, which is located at an altitute high enough (3800 m) to have a reduced atmospheric pressure. Lake Titikaka is located in the North side of the Altiplano (high plateu) in South America. It is shared between Bolivia and Peru, and it is, by far, the largest water body in the region, and at such altitudes in general. So it becomes a dominant geographical and climatic unit in the South American Altiplano, which has a desert–like climate, with monsoon-type rainy season (November to February) and a long dry season (March to October). During the dry season (local winter) the daily temperature cycle goes from maxima around 15 °C (past noon) to freezing minima near -5 °C (before dawn). This temperature span is larger than the seasonal difference, around 5 °C, between summer and winter. Due to its large water mass, the Lake hampers the temperature variations and avoids the freezing of both the lake itself and its shores. The daily temperature fluctuations cause also a daily wind-intensity cycle, with maxima just before the sunset. Lake Titikaka has an alongated shape with a long axis of 120 km in the NW-SE direction, and its short axis of 50 km in the NE-SW direction; with a large peninsula on the South shore (Copacabana). This size, plus deep waters (in excess of 250 m, pelagic condition) allows development of extnsive waves produced by the surface winds, coming predominantly from the North. The shores of Lake Titikaka have several geographical features, among others: delta rivers, sandy beaches and rock cliffs. The (“main”) study site is located in the large portion of the lake, near a mid-point between Santiago de Huata and the Isla de la Luna (Moon Island) as far possible from the shores.
The three-dimensional density compression ratio of shock fronts observed as halo coronal mass ejections 
Authors: Kwon Ryun Young
Published: March 2021

We present a novel method to derive the shock density compression ratio of coronal shock waves that are occasionally observed as halo coronal mass ejections (CMEs). Our method uses the three-dimensional (3-D) geometry and enables us to access the reliable shock density compression ratio. We show the 3-D properties of coronal shock waves seen from multiple vantage point observations, i.e., geometry, kinematics, and compression ratio (Mach number). The significant findings are as follows: (1) Halo CMEs are the manifestation of spherically shaped fast-mode waves/shocks, rather than a matter of the projection of expanding flux ropes. The footprints of halo CMEs on the coronal base are the so-called EIT/EUV waves. (2) These spherical fronts arise from a driven shock (bow- or piston-type) close to the CME nose, and it is gradually becoming a freely propagating (decaying) fast-mode shock wave at the flank. (3) The shock density compressions peak around the CME nose and decrease at larger position angles (flank). (4) Finally, the supercritical region extends over a large area of the shock and lasts longer than past reports.  These results offer a simple unified picture of the different manifestations for CME-associated (shock) waves, such as EUV waves and SEP events observed in various regimes and heliocentric distances. We conclude that CME shocks can accelerate energetic particles in the corona over extended spatial and temporal scales and are likely responsible for the wide longitudinal distribution of these particles in the inner heliosphere.
Modelling the ascent of picritic lunar magmas
Authors: Lo Marissa , La Spina Giuseppe , Joy Katherine , Polacci Margherita , Burton Mike
Published: March 2021

Quantifying the volatile content of the lunar interior is valuable for understanding the formation, thermal evolution, and magmatic evolution of the Earth and Moon. Petrological modelling and geochemical measurements have been used to study the volatile composition of the lunar interior. Improvements to analytical instruments have facilitated more precise measurements of the volatile content of lunar samples and meteorites, however, several problems remain with these measurements, hence, the volatile content of lunar magmas has yet to be constrained with certainty. We propose a volcanological approach for inferring the volatile contents of different lunar magmas.

            A terrestrial magma ascent model has been modified for lunar applications. Numerous parameters were adjusted for lunar conditions, including: magma major element composition, from low-Ti (green and yellow glasses) to high-Ti (orange, red, and black glasses); H2O content; CO content; gravity; and pressure. The model calculated values for gas exsolution, viscosity, mass flow rate, and several other ascent processes, from a depth of 10 km to the surface. Using these results, we will assess the effect of varying magmatic volatile content on lunar magma ascent processes. We will also compare and contrast our results with existing models for lunar magma ascent, as well as models for magma ascent on other planetary bodies. Future work will involve modelling eruptions, using results from the magma ascent model, and verifying the results of the models using images and digital elevation models of the lunar surface.
Key role of overlooked twilight zone towards climate buffering
Authors: Saxena Himanshu , Sahoo Deepika , Nazirahmed Sipai , Kumar Rai Deepak , Khan Mohammad Atif , Sharma Niharika , Kumar Sanjeev , K Sudheer Athiyarath , Singh Arvind
Published: March 2021

The twilight zone of the oceans layering between the bottom of the sunlit ocean and 1000 m depth, is one of the largest continuous ecosystems on the Earth, yet remains least explored. While the sunlit ocean is well-studied for its major role in sequestering CO2 from the atmosphere, the role of twilight zone in CO2 sequestration remains a mystery. The twilight zone of the Arabian Sea, north-western part of the Indian Ocean inarguably possesses an active nitrogen‐cycle owing to abundant chemoautotrophic (anammox, nitrite oxidising, nitrifying) microorganisms and heterotrophic (denitrifying) microorganisms. However, these microorganisms with ramifications for the nitrogen cycle, incentivize the carbon cycle. Since chemoautotrophy is a light-independent autotrophic process, a significant amount of dissolved CO2 may be assimilated rather than released in the Arabian Sea twilight zone by these organisms. With this supposition, we commenced the expedition in the off-shore and the central Arabian Sea during winter monsoon (Dec-Jan 2019) to measure carbon fixation rates in its sunlit and twilight zone using 13C tracer incubation technique. The sunlit zone and twilight zone carbon fixation rates ranged from 6.8 to 40 mmol C m-2 d-1 and 0.4 to1.6 mmol C m-2 d-1, respectively. The twilight zone carbon fixation did not vary spatially much, unlike sunlit zone which showed a sharp decreasing trend of carbon fixation from northern to the southern Arabian Sea. Notably, the twilight zone contribution to water column carbon fixation ranged from 2 to 10% during the study period. This study corroborates that the twilight zone forms an integral component of the carbon cycle; implying, the overlooked twilight zone can significantly contribute CO2 drawdown. Therefore, the role of twilight zone towards climate buffering is bigger than previously assumed, demanding a review of its role in the current paradigm of the Earth’s climate.
Role of rheology, ascent rate and outgassing on fragmentation: implications for basaltic lava fountains
Authors: La Spina Giuseppe , Arzilli Fabio , Llewellin Ed , Burton Mike , Clarke Amanda , de’ Michieli Vitturi Mattia , Polacci Margherita , Hartley Margaret , Di Genova Danilo , Mader Heidy
Published: March 2021

Basaltic volcanoes exhibit a wide range of eruptive styles, from relatively gentle effusive eruptions (producing lava flows and lava domes) to highly explosive activity (where pyroclastic materials are ejected from the vent as a jet or plume). The difference between explosive and effusive eruptions is dictated by the ability of magma to fragment during ascent. For lava fountains the distinction is unclear, as the liquid phase in the rising magma may remain continuous to the vent, fragment in the fountain, then re-weld on deposition to feed rheomorphic lava flows.

Here we use a magma ascent model to constrain the controls on basaltic eruption style, using Kilauea and Etna as case studies. Following our results, we suggest that lava fountaining is a distinct style, separate from effusive and explosive eruption styles, that is produced when magma ascends quickly and fragments above the vent, rather than within the conduit. Performing sensitivity analyses of Kilauea and Etna case studies we found that high lava fountains (> 50 m high) occur when the Reynolds number of the bubbly magma is greater than ~0.1, the bulk viscosity is less than 106 Pa s, and the gas is well-coupled to the melt. According to our results, explosive eruptions (Plinian and sub-Plinian) are expected over a wide region of parameter space for higher viscosity basalts, typical of Etna, but over a much narrower region of parameter space for lower viscosity basalts, typical of Kilauea. Numerical simulations indicate also that the magma that feeds high lava fountains ascends more quickly than the magma that feeds explosive eruptions, thanks to its lower viscosity. For the Kilauea case study, a decreasing ascent velocity is expected to produce a progressive evolution from high to weak fountaining, to ultimate effusion. For the Etna case study, instead, small changes in parameter values lead to transitions to and from explosive activity, indicating that eruption transitions may occur with little warning.
The sustainability of fresh groundwater resources in major deltas around the world
Authors: van Engelen Joeri , Oude Essink Gualbert , Bierkens Marc
Published: March 2021

Increasing population, growth of cities and intensifying irrigated agriculture in the world’s deltas promote the demand for fresh water resources, accelerating groundwater extraction. This, in turn, leads to sea water intrusion and salt water upconing, which threaten near-future water and food security. Proper water management in deltas requires precise knowledge about the current status of the deltas’ fresh groundwater resources, in the form of a groundwater salinity distribution. However, this knowledge is scarcely present, especially at larger depths. In this research, we applied three-dimensional variable-density groundwater model simulations over the last 125 ka to estimate present-day fresh groundwater volumes for several major deltas around the world. We also compared these to current extraction rates and estimated the time until in-situ fresh groundwater resources are completely exhausted (ignoring local-scale problems), partly leading to groundwater level decline and mostly replacement with river water or saline groundwater. In this presentation we will share our findings, for example which deltas’ groundwater reserves presumably are under stress.
The role of available energy in estimating potential evaporation over different soil textures
Authors: Li Wanxin , Hendricks Franssen Harrie-Jan , Brunner Philip , Li Zhi , Wang Wenke
Published: March 2021

The potential evaporation rate (PE) depends on the available energy at the land-atmosphere interface and soil properties. The application of the full-form Penman-Monteith equation (PM) is often simplified. For example, the ground heat flux G is often assumed to be zero for calculating daily evaporation as the value of G is relatively small compared to the net radiation Rn. This and other simplifications consider that the PE value is mainly determined by meteorological variables and independent from soil properties. As the influence of soil textures on PE have so far received little attention, we analyzed data from a lysimeter experiment in the Guanzhong Basin, China. The potential evaporation rate was measured over saturated fine sand (PEfine), coarse sand (PEcoarse) and gravel sand (PEgravel) at a high temporal resolution. Meteorological variables, ground heat flux and soil temperature at different depths were observed from July 2018 to August 2019. The measured PE showed clear differences between the three saturated bare soils especially during spring and summer. Our previous research showed that these PE differences are controlled by differences in the available energy, related to differences in the total ground heat flux G for the three materials and different albedos. Both a detailed energy balance and the full-form PM equation can explain the PE differences between the different soil textures on the basis of hourly data. On the other hand, if the full-form PM equation is applied on daily data only minor differences in PE between the three textures are calculated. Our research suggests that the available energy should be calculated as precisely as possible, considering the soil porosity, thermal conductivity as well as albedo for the different soil textures, in order to estimate evaporation. 
Toward a low-cost disdrometer: simulating the collision of raindrops with a cantilever piezo film
Authors: Wei Chi-Ling , Su Wei-Jiun , Chang Shu-Wei , Wang Li-Pen
Published: March 2021

Raindrop size distribution (DSD) is the key factor to derive reliable rainfall estimates. It is strongly related to a number of integral rainfall parameters, including rain intensity (R), rain water content (W) and radar echo (Z). Disdrometers are the senors commonly used to measure DSD based upon microwave or laser technologies; such as JWD (Joss-Waldvogel Disdrometer), Parsivel and 2DVD (Two-Dimensional Video Disdrometer). These sensors have different strengths and weakness, and they are relatively expensive. This hinders the possibility to have a large-scale and high-density observation of DSD. In this work, our goal is to explore the possibility to develop a lightweight and low-cost disdrometer with high accuracy.

We start with establish a model that can well simulate the signal reaction of a single drop falling on a cantilever piezo film. A series of experiments were conducted to test the reaction of drops with different sizes (diameters ranging from 2 - 4 mm) and as drops falling onto different locations of the film. We then modelled the collision by assuming the piezo film to be a damped cantilever beam and drop force to be a step force; and the drop force is derived based upon the measurement of the deflection of beam end, which is further used to fit the damp ratio. Preliminary results suggest that the signal reaction of a single drop hits can be well simulated based upon the proposed model under current experimental setting. More experiments and simulations are currently undergoing to explore the capacity of the proposed model with different drop falling velocity, size and position, as well as its reaction of multiple drops.  
Coupled earth system modeling on heterogeneous HPC architectures with ParFlow in the Terrestrial Systems Modeling Platform
Authors: Hokkanen Jaro , Kollet Stefan , Kraus Jiri , Herten Andreas , Hrywniak Markus , Pleiter Dirk
Published: March 2021

Rapidly changing heterogeneous supercomputer architectures pose a great challenge to many scientific communities trying to leverage the latest technology in high-performance computing. Implementations that simultaneously result in a good performance and developer productivity while keeping the codebase adaptable and well maintainable in the long-term are of high importance. ParFlow, a widely used hydrologic model, achieves these attributes by hiding the architecture-dependent code in preprocessor macros (ParFlow embedded Domain Specific Language, eDSL) and leveraging NVIDIA's Unified Memory technology for memory management. The implementation results in very good weak scaling with up to 26x speedup when using four NVIDIA A100 GPUs per node compared to using the available 48 CPU cores. Good weak scaling is observed using hundreds of nodes on the new JUWELS Booster system at the Jülich Supercomputing Centre, Germany. Furthermore, it is possible to couple ParFlow with other earth system compartment models such as land surface and atmospheric models using the OASIS-MCT coupler library, which handles the data exchange between the different models. The ParFlow GPU implementation is fully compatible with the coupled implementation with little changes to the source code. Moreover, coupled simulations offer interesting load-balancing opportunities for optimal usage of the existing resources. For example, running ParFlow on GPU nodes, and another application component on CPU-only nodes, or efficiently distributing the CPU and GPU resources of a single node between the different application components may result in the best usage of heterogeneous architectures.
Modeling glacial lake outburst flood process chains in Sikkim Himalaya: Hazard assessment of two potentially dangerous lakes
Authors: Sattar Ashim , Allen Simon , Frey Holger , Huggel Christian , Mergili Martin
Published: March 2021

The presence of large and rapidly growing glacial lakes along the Himalayan Arc makes glacial lake outburst floods (GLOFs) a serious mountain hazard. While glacial lakes are mainly located in remote and unsettled mountain valleys, far-reaching GLOFs may claim lives and damage assets tens of kilometers downstream. Evaluating GLOF hazard is therefore of high importance, considering current and potential future climate-driven changes of glaciers and glacial lakes. A major concern in the Northeastern Indian Himalayan state of Sikkim is the damage potential these flood events can cause to hydropower plants and local vulnerable communities. This is particularly true for outburst floods potentially originating from the two lakes in Sikkim that are considered hazardous: the South Lhonak Lake and the Shako Cho Lake. Both lakes have been recognized in previous studies, and by local and state authorities, as being high priority sites for further monitoring and potential risk reduction measures. Recognizing the need for related risk reduction strategies to be based on robust scientific understanding, this study aims to combine remote sensing approaches with hydrodynamic flood modeling to identify key threats to lives and livelihoods.

This study also provides the first implementation of recently developed national guidelines on the management of GLOFs, where a detailed risk assessment including potential GLOF triggers, conditioning factors, and downstream impacts forms the scientific core. First results of only-water flow using HEC-RAS show that a high-potential scenario (dam breach depth = 40 m) produces flow depth and flow velocity up to 25 m and 9-12 m s-1, respectively, at Chungthang, a town located close to a major hydropower station, 62 km downstream of the lake. The fact that GLOF flow rheology is often changing as it propagates downstream, further modeling has been undertaken with r.avaflow, which can simulate the entire process chain from initial avalanche triggering, to dam erosion, and downstream flow propagation with a multi-phase modeling approach. Hence, we can evaluate the potential downstream impact in the case of a GLOF transitioning into a debris flow process. Our results provide flow hydraulics including flow velocities, flow heights, and total downstream inundation. These parameters will provide important insights for risk reduction strategies, such as early warning systems and land-use planning under current and future glacial conditions.

 
Glacial Isostatic Adjustment as a process of deformation but not seismicity in Western Alps: Coupling geodetical strain rate and numerical modeling 
Authors: Grosset Juliette , Mazzotti Stéphane , Vernant Philippe
Published: March 2021

In the last decade, geodetic data has become fundamental in studies of active faults, seismicity and seismic hazard. In particular, GNSS strain rates and velocities are used to constrain fault-slip rates and seismicity parameters, on the premise that these short-term (ca. 10 yr) measurements are representative of long-term (104–106 yr) fault activity. The Western Alps are a good example of such development in a very-low-strain region with a high-density ongoing seismic activity. There, the first-order agreement between GNSS strain rates and earthquake deformation patterns suggest that a large part of the geodetic deformation observed in the area is seismic. This correlation also suggests that geodetic strain rates can provide constraints on seismicity and seismic hazard. With a numerical modeling approach, we point out the similarities between strain rates predicted for Glacial Isostatic Adjustment (GIA) from the Last Glacial Maximum and the geodetic strain rate field, suggesting that a large part of the GNSS signal is related to GIA. However, we show that the apparent compatibility between geodetic strain rates and seismicity hides a strain rate - stress paradox. In fact, stress perturbations due to GIA are not compatible with observed seismicity, and even tend to inhibit fault activity (as observed from focal mechanisms). Thus, the Western Alps present a typical example of a tectonic system where a transient deformation process precludes, or at least strongly complexifies, the use of geodetic strain rates in seismicity and seismic hazard analyses.
EOF Analysis of Green Cumulus Mesoscale Organization
Authors: Dror Tom , Chekroun Mickael D. , Altaratz Orit , Koren Ilan
Published: March 2021

Warm convective clouds play a key role in the Earth’s radiative and water budgets. Nonetheless, they still comprise the largest source of uncertainty in climate model’s prediction of cloud feedback and climate sensitivity. The latter might be affected by the variety of patterns that warm convective clouds form on the mesoscale, an effect which is largely uninvestigated, and even more so over land. A large subset of continental shallow convective cumulus (Cu) fields was shown to have unique spatial properties and to form mostly over forests and vegetated areas thus referred to as green Cu. Green Cu fields form organized mesoscale patterns, yet the underlying mechanisms, as well as the time variability of these patterns, are still lacking understanding.  In this work, we characterize the organization of green Cu in space and time, by using data-driven organization metrics, and by decomposing the high-resolution GOES–16 data using an Empirical Orthogonal Function (EOF) analysis. We extract and quantify modes of organization present in a green Cu field, during the course of a day. The EOF decomposition shows the field's key organization features such as cloud streets, and it also reveals hidden ones, as the propagation of gravity waves (GW), and the development of a highly ordered grid of clouds that extends over hundreds of kilometers, over a time span that scales as the field's lifetime. We then use cloud fields that were reconstructed from different subgroups of modes to quantify the cloud street's wavelength and aspect ratio, as well as the GW dominant period.
Impact of climate change and industrialization on remote Lake Bolshoe Toko, Siberia 
Authors: Biskaborn Boris K. , Narancic Biljana , Stoof-Leichsenring Kathleen R. , Pestryakova Lyudmila A. , Appleby Peter G. , Piliposian Gayane T. , Diekmann Bernhard
Published: March 2021

To test if recent climate change and pollution affected remote lake ecosystems without direct human influence, we used paleolimnological methods on lake sediments from a large, prestine, and deep lake in Yakutia, Russia. We compared diatoms and sediment-geochemistry from before and after the onset of industrialization in the mid-nineteenth century, at water depths between 12.1 and 68.3 m in Lake Bolshoe Toko. We analyzed diatom species changes and geochemical changes including mercury concentrations. Chronologies were established using 210Pb and 137Cs revealing sedimentation rates between 0.018 and 0.033 cm y-1 at shallow- and deep-water sites, respectively. Increase in light planktonic diatoms (Cyclotella) and decrease in heavily silicified euplanktonic Aulacoseira through time at deep-water sites can be related to warming air temperatures and shorter periods of lake-ice cover, causing pronounced thermal stratification. Diatom beta diversity changed only significantly in shallow-water communities which can be related to the development of new habitats with macrophyte growth. Mercury concentrations increased by a factor of 1.6 as a result of atmospheric fallout. Increases in the chrysophyte Mallomonas indicates a trend towards acidification. We conclude that also remote boreal lakes are susceptible to human-induced long-distance pollution and recent climate change.
Can we reach a sensible balance between generality of model parameters and accuracy of simulations?
Authors: Merganicova Katarina , Dobor Laura , Hollos Roland , Merganič Ján , Barcza Zoltán , Kurjak Daniel , Novák Jiri , Sitková Zuzana , Fleischer Peter , Marjanovic Hrvoje , Hidy Dóra , Střelcová Katarína , Hlásny Tomáš
Published: March 2021

Process-based ecosystem models are versatile tools providing profound insights into ecosystem processes and interactions between vegetation and environment. The ongoing development of the Biome-BGCMuSo model has delivered multiple improvements in model structure and parameters, and subsequently in simulated ecosystem dynamics. Since the number of parameters has increased during the model development, model parametrisation for biomes or tree species of interest is required to enable reliable model usage in the future.

Here we explore the issue of site-specific versus multi-site calibration of model parameters for the European beech (Fagus sylvatica L.) along an extended environmental gradient across Central Europe, covering Croatia, Hungary, Slovakia, Poland and the Czech Republic. First, thorough literature search for the plausible ranges of individual model parameters was conducted. This was followed by the sensitivity analysis to identify the most influential model parameters. Finally, model calibration was performed based on the generalised likelihood uncertainty estimation method and the data from long-term research plots located in the five countries. The calibration was conducted at levels of individual sites and the region as a whole to evaluate different aspects of site-specific and multi-site calibration approaches and to develop a generalised parameter set for the European beech in Central Europe.
Spatiotemporal tomography based on scattered multiangular signals and its use for resolving evolving clouds using moving platforms
Authors: Ronen Roi , Schechner Yoav Y. , Eytan Eshkol
Published: March 2021

The climate is strongly affected by interaction with clouds. To reduce major errors in climate predictions, this interaction requires a much finer understanding of cloud physics than current knowledge. Current knowledge is based on empirical remote sensing data that is analyzed under the assumption that the atmosphere and clouds are made of very broad and uniform layers. To help to overcome this problem, 3D scattering computed tomography (CT) has been suggested as a way to study clouds. 

CT is a powerful way to recover the inner structure of three dimensional (3D) volumetric heterogeneous objects. CT has extensive use in many research and operational domains. Aside from its common usage in medicine, CT is used for sensing geophysical terrestrial structures, atmospheric pollution and fluid dynamics. CT requires imaging from multiple directions and in nearly all CT approaches, the object is considered static during image acquisition. However, in many cases, the object changes while multi-view images are acquired sequentially. Thus, an effort has been invested to expand 3D CT to four-dimensional (4D) spatiotemporal CT. This effort has been directed at linear CT modalities. Since linear CT is computationally easier to handle, it has been a popular method for medical imaging. However, these linear CT modalities do not apply to clouds: clouds constitute a scattering medium, and therefore radiative transfer is non-linear in the clouds’ content.

This work focuses on the challenge of 4D scattering CT of clouds. Scattering CT of clouds requires high-resolution multi-view images from space. There are spaceborne and high-altitude systems that may provide such data, for example AirMSPI, MAIA, HARP and AirHARP. An additional planned system is the CloudCT formation, funded by the ERC. However, these systems are costly. Deploying them in large numbers to simultaneously acquire images of the same clouds from many angles can be impractical. Therefore, the platforms are planned to move above the clouds: a sequence of images is taken, in order to span and sample a wide angular breadth. However, the clouds evolve while the angular span is sampled.

We pose conditions under which this task can be performed. These regard temporal sampling and angular breadth, in relation to the correlation time of the evolving cloud. Then, we generalize scattering CT. The generalization seeks spatiotemporal recovery of the cloud extinction field in high resolution (10m), using data taken by a small number of moving cameras. We present an optimization-based method to reach this, and then demonstrate the method both in rigorous simulations and on real data.
Global differences in the energy balance and melt rates of debris-covered glacier surfaces
Authors: Miles Evan , Steiner Jakob , Buri Pascal , Immerzeel Walter , Pellicciotti Francesca
Published: March 2021

Supraglacial debris covers 4% of mountain glacier area globally and generally reduces glacier surface melt. Studies have identified enhanced energy absorption at ice cliffs and supraglacial ponds scattered across the debris surface. Although these features generally cover a small portion of glacier surface area (5-10%) they contribute disproportionately to mass loss at the local glacier scales (20-40%). While past studies have identified their melt-enhancing role in High Mountain Asia, Alaska, and the Alps, it is not clear to what degree they enhance mass loss in other areas of the globe.

We model the surface energy balance for debris-covered ice, ice cliffs, and supraglacial ponds using meteorological records (4 radiative fluxes, wind speed, air temperature, humidity) from a set of on-glacier automated weather stations representing the global prevalence of debris covered glaciers. We generate 5000 random sets of values for physical parameters using probability distributions derived from literature. We also model the hypothetical energy balance of a debris-free glacier surface at each site, which we use to investigate the melt rates of distinct surface types relative to that of a clean ice glacier. This approach allows us to isolate the melt responses of debris, cliffs and ponds to the site specific meteorological forcing.

For each site we determine an Østrem curve for sub-debris melt as a function of debris thickness and a probabilistic understanding of surface energy absorption for ice cliffs, supraglacial ponds, and debris-covered ice. While debris leads to strong reductions in melt at all sites, we find an order-of-magnitude spread in sub-debris melt rates due solely to climatic differences between sites. The melt enhancement of ice cliffs relative to debris-covered ice is starkly apparent at all sites, and ice cliffs melt rates are generally 1.5-2.5 times the ablation rate for a clean ice surface. The supraglacial pond energy balance varies regionally, and is sensitive to wind speed and relative humidity, leading to energy absorption 0.4-1.2 times that of clean ice, but 5-10 times higher than debris-covered ice. Our results support the few past assessments of melt rates for cliffs and ponds, and indicate sub-regional coherence in the energy balance response of these features to climate.
Travel-time tomography imaging the Ecuadorian subduction, north of the Mw 7.8 Pedernales earthquake
Authors: Skrubej Alexandra , Galve Audrey , Laigle Mireille , Rietbrock Andreas , Charvis Philippe , Vaca Sandro , Agurto-Detzel Hans , Schenini Laure , Bogelspacher Felix , Oregioni Davide , Vignon Damien , Brotzer Andreas , Muñoz Muñoz Maria , Moreno Piña Mayra
Published: March 2021

The Ecuadorian subduction regularly hosts large earthquakes. Among them, the Mw 8.8 1906 earthquake is the 7th biggest known event. Following the recent 2016 Mw 7.8 Pedernales earthquake, a large deployment of onshore/offshore seismological stations, in addition to the permanent seismological/geodetical network, revealed a complex slip behavior including the presence  of  seismic and aseismic slip.

During the geophysical experiment HIPER, in march 2020, 47 Ocean Bottom Seismometers (OBS), were densely deployed along a 93-km-long trench-perpendicular profile, recording airgun shots (4990 cu.inch.) performed by R/V Atalante to obtain a high-resolution P-wave velocity image. The profile was located north of the 2016 Pedernales rupture zone passing through an area experiencing aseismic slip and a region of contrasted geodetic interseismic coupling.    

We used the traveltime tomography code « tomo2d » (Korenaga et al., 2000) to invert first arrivals and reflected phases recorded by our OBS.  A joint 2D-seismic-reflection profile was acquired (abstract by L. Schenini) and provides details on the oceanic basement topography and on Vp velocities in shallow sedimentary layers.

Regarding the structural complexity in the region, we decided to start the inversion  using an a priori 2D velocity model. Several geophysical experiments have already been conducted offshore-onshore Ecuador (SISTEUR, 2000 ; SALIERI, 2001 and ESMERALDAS, 2005). Compilation of velocity models from tomographic images were used to build two a priori 1D Vp velocity models for both the Nazca oceanic crust and the forearc seismic structure. A 2D a priori Vp velocity model was built by merging the results of the two localized inversions using a selection of OBS on each side of the trench.

We obtain the crustal structure of the upper and subducting plates down to 20 km depth. Beneath the trench, a ~30-km-wide low-Vp anomaly is observed at lithospheric scale. This velocity is 10% lower than the typical Vp values observed for hydrated Pacific-type oceanic crust near the trench (Grevemeyer et al., 2018). Recorded PmP phases will allow us to further constrain the crustal thickness. While we observe PmP phases in areas of low-Vp, the Moho reflectivity weakens and even disappears from the coincident MCS line. This intriguing observation could highlight processes, such as the presence of fluids or serpentinization, that need to be identified and better understood.
Types of heterogeneities and deformation mechanisms in blueschist rocks: an example from an exhumed subduction complex in Ishigaki Island, Ryukyu Arc
Authors: De Caroli Sara , Fagereng Ake , Ujiie Kohtaro , Meneghini Francesca
Published: March 2021

The geological properties of the subduction interface, such as stable metamorphic assemblages and the rheology of shear zone rocks, change with depth. Studies based on seismic and geodetic observations suggest that these changes can be accompanied by differences in seismic styles. In this realm, slow slip events (SSEs) and related tremor signals, grouped as episodic tremor and slip (ETS) events, have been detected down-dip of the subduction megathrust seismogenic zone. A wide range of mechanisms, some invoking rheological heterogeneity, has been proposed to explain ETS occurrence. Given that ETS events accommodate most of the plate interface displacement in a depth range below the seismogenic zone, it is of great interest to understand the rheology of the rock lithologies that are likely to host ETS along the deep subduction interface.

Here, we present data from an exhumed subduction complex in Ishigaki Island, Ryukyu Arc. In particular, we analyse the Triassic high pressure-low temperature Tomuru metamorphic rocks, which comprise blueschist and greenschist facies metabasites that underwent subduction-related deformation. These rocks offer an important natural laboratory in which to study the characteristics of blueschist deformation structures to infer rheology and, in particular, the role played by heterogeneities in an environment comparable to modern ETS down-dip of the seismogenic zone.

Through multiscale and multidisciplinary, field- and laboratory-based studies, including quantitative microstructural and image analyses, we focus on two main topics. Firstly, we aim to understand blueschist rheology, by documenting the deformation mechanisms active in blueschist rocks through electron backscatter diffraction (EBSD), in order to quantify intracrystalline deformation and lattice preferred orientation (LPO) development. Secondly, we study the effect of grain size on blueschist foliation development and, ultimately, on blueschist deformation.  Through these analyses, we hope to constrain both subduction interface strength and dominant mineral- scale deformation mechanisms at blueschist conditions.
Silicon‐mediated manganese tolerance of cucumber: the apoplastic modulation
Authors: Dragisic Maksimovic Jelena , Mojovic Milos , Maksimovic Vuk
Published: March 2021

An impressive body of Si research could be found in the literature despite the fact that, from a biochemical perspective, Si is a “monotonous” element largely uncharged and unreactive at physiological pH (forming mostly silicates and SiO2 polymers). However, the detailed role of Si in plants remains unexploited, particularly the potential for its practical application. One of the main properties of Si intensively explored is the protection mechanism(s) against biotic and abiotic stresses, especially heavy metal stress. To investigate the effect of Si application on the Mn binding potential of the leaf apoplast, cucumber plants were grown in nutrient solutions with optimal (0.5 µM) or excessive (100 µM) Mn concentrations with or without Si supply to roots. Leaves were subjected to fractionated extraction of Mn revealing a relative distribution of Mn fractions in cucumber leaves: water-extractable (WE) Mn represents the soluble fraction in the cell walls; the protein-bound (PB) Mn fraction originates mostly from the symplast; while the cell wall-bound (CWB) Mn fraction represents Mn which is fixed to the wall structure. After the high Mn supply (100 µM), the concentration of WE Mn was 10-fold higher compared to control, while the relative proportion of the WE Mn fraction decreased from 56% in control to 23% in high Mn treatment. Si application did not affect WE and PB Mn fractions in the control treatment but significantly decreased these fractions in the high Mn treatment. On the other hand, the CWB Mn significantly increased in the leaves of Si-fed plants. Data obtained by fractionated Mn extraction are consistent with the relative proportion of free and bound Mn, estimated from the recorded electron paramagnetic resonance (EPR) signals of Mn2+. The EPR spectrum of a high spin Mn2+ showed the characteristic six hyperfine lines whose intensity correlated with Mn treatments and, consequently, leaf concentrations of Mn. The results presented here demonstrated that Si supply increased the Mn binding properties of leaf cell walls in cucumber plants with simultaneously decreasing of the free apoplastic Mn2+, indicating the protective role of Si in smothering harmful (inter)actions of free Mn2+ within plant tissue. Taken together, the leaf apoplast plays the central role in modulation of Mn toxicity and Si enhanced Mn tolerance in cucumber.

This work was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Contract No. 451-03-68/2020-14/200053).
Petrography and phase equilibrium modeling of Paleoproterozoic metapelite in the Kuluktag area of Tarim Craton
Authors: Guo Yu
Published: March 2021

  The Kuruqtag area, located at the northeastern margin of the Tarim Craton, where the Precambrian metamorphic basement exposed, is ideal for studying the Precambrian geological evolution of the Tarim Craton. Previous zircon U-Pb chronology studies revealed that the metamorphic basement recorded a Paleoproterozoic tectonothermal event and suggested it associates with the Paleoproterozoic Nuna/Columbian supercontinent convergence event. However, the extensive range of metamorphic ages obtained from different studies (ranging from 1750-2000 Ma) and the lack of detailed P-T path corresponding to different metamorphic ages make it difficult to constrain the evolutionary framework of the Tarim craton during the Paleoproterozoic, which in turn affects future comparative regional studies.

  To constrain the P-T path, in this study, we performed detailed petrography, mineral chemical, and phase equilibrium modeling of metapelite collected from the khondalite series in the western part of the Kuruqtag (a garnet-sillimanite-cordierite-biotite gneiss with metamorphic age ~1850 Ma) and obtained the following results.

  Through petrographic studies, at least three phases of mineral assemblages can be used to invert the P-T path experienced by the metapelite. They are    M1 (peak metamorphic stage):represented by fine-grained biotite remnant (Bi Ⅰ) + fine-grained plagioclase(Pl Ⅰ) and quartz+ Ilmenite + , occurring as inclusions within the metamorphic garnet, and equilibrated mineral assemblages is: Grt(core) + Bi Ⅰ + Sill + Kfs + Pl Ⅰ + Qz + Ilm. M2 (isothermal depression stage), represented by cordierite occurring in the garnet rim or with spinel in the matrix, inferred equilibrated mineral assemblages is Grt(rim)+Bi Ⅰ +Cd+Kfs+Pl ⅠⅠ+Ilm+Sp.M3 (isothermal depression stage), is marked by the appearance of new growth of biotite(Bi ⅠⅠ) and the conversion of Sill to And. 

The P-T conditions for the mineral assemblage evolution (M1 → M3) are constrained by a P-T pseudosection constructed in the Na2O -CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O- TiO2-O2 chemical system. The resulting P-T path is clockwise from the M1 stage (840°C, 4 Kbar) through the isothermal depression path to M2 (840-850°C,5 Kbar) and then through the near-isobaric cooling path to the M3 stage (650°C, 3.5-4 Kbar).
Parametrizing wind farms in mesoscale models: review of existing approaches, applications and future advancements
Authors: Fischereit Jana , Brown Roy , Guo Larsén Xiaoli , Badger Jake , Hawkes Graham
Published: March 2021

With the expansion of wind energy on- and offshore, large-scale wind farm flow effects in a temporal and spatially heterogeneous atmosphere become increasingly relevant. Mesoscale models equipped with a Wind Farm Parametrization (WFP) can be used to study these effects. In the past, different WFPs have been developed and were applied with different aims. The aim of this study is to provide a better overview on existing WFPs, their development stage and application areas. 

Through a systematic literature review based approach, 617 potentially relevant publications were identified, out of which 59 were reviewed in detail. From these studies, 10 different explicit WFPs have been identified along with three main application areas: (1) the characterizations of wind farm flow effects, (2) the environmental impact of wind farms and (3) the implication for wind energy planning.

In this presentation, we will review differences between the identified WFPs including their description of the turbine-induced forces and turbulent kinetic energy production as well as their treatment of sub-grid scale effects. In addition, we will summarize the literature findings on existing validation of the WFPs and on the sensitivity of the WFPs to the mesoscale model set-up. Reviewing the results for the different application areas indicated that wind farm wakes can last for several 10s of kilometers downstream depending on stability, surface roughness and terrain. Therefore, neighbouring wind farms need to be taken into account for regional planning of wind energy. Yet, their environmental impact, in terms of other reviewed parameters than wind, is mostly confined to areas close to the farm.

Based on these findings, we suggest that future work should include, among other things, benchmark-type validation studies with long-term measurements for different WFPs, further developments of WFPs and mesoscale model physics and more interactions between the mesoscale and microscale community.
Snow Water Equivalent retrieval using L- & C-band InSAR.
Authors: Jorge Ruiz Jorge , Lemmetyinen Juha , Kontu Anna , Pulliainen Jouni
Published: March 2021

Interferometric Synthetic Aperture Radar (InSAR) imagery is a promising technique for retrieving Snow Water Equivalent (SWE). It exploits the relation of the interferometric phase to the amount and density of the snow in the radar signal path, leading to a quasi-linear relation with SWE (Guneriussen et al., 2001; Leinss et al., 2015). Here, we analyze timeseries of Sentinel-1 and ALOS-2 interferometric image pairs, collected over a test site in Sodankylä, Northern Finland, during the winter of 2019-2020. The satellite imagery is complemented by tower-based SAR observations using SodSAR (Sodankylä SAR) a 1-10GHz fully polarimetric SAR instrument. Typical satellite visit times (7 and 14 days) are compared with the 12-hour temporal resolution provided by SodSAR. Interferometric pairs from the three sensors are generated, and the interferograms are used to estimate the increase in SWE between the image acquisitions. Retrieved SWE is compared with measurements of an in-situ SWE scale, as well as manual ground observations made in the area. Coherence conservation and its relation with various meteorological events are also analyzed.
Raman Spectroscopy as a potential strain gauge
Authors: Bond Clare , Kedar Lauren , Muirhead David
Published: March 2021

Raman Spectroscopy is increasingly being used to better understand a range of Earth Science processes. Notable recently is the application of Raman Spectroscopy to carbonaceous material in strained rocks. Here we investigate the changes in Raman Spectral response in strained material relative to an unstrained equivalent, drawing on examples from the published literature and our own work. We consider inconsistencies in the relative changes in Raman Spectral parameters of strained material and their potential causes. In doing so we look at some of the current methods for determining Raman Spectral parameters in rocks and what they might tell us about the strain state of carbon in a single rock sample. Finally, we consider the implications for use of Raman Spectroscopy of carbonaceous material as a geothermometer as well as a future potential strain gauge. 