bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating global terrestrial water storage components by a physically constrained recurrent neural network
Authors: Kraft Basil , Jung Martin , Körner Marco , Koirala Sujan , Reichstein Markus
Published: March 2022

While deep learning models are capable of representing complex temporal processes in a data-adaptive way, they lack physical consistency and interpretability. Thus, the combination of machine learning and physically-based approaches in so-called hybrid modeling has been proposed recently [1]. Gathering insights into complex Earth system processes in a data-driven way has, arguably, a large potential for hydrology. This is, on the one hand, due to the richness of Earth observations of hydrological quantities, such as terrestrial water storage, runoff, snow cover, or evapotranspiration. On the other hand, the large uncertainties in current global hydrological models across spatial and temporal scales motivate the exploration of alternative, complementary approaches.

In this work [2], we evaluate an experimental approach for the global, data-driven decomposition of terrestrial water storage. Therefore, we developed a dynamic hybrid model which represents the main terrestrial water storage components of groundwater, soil moisture, and snowpack. The model consists of a recurrent neural network that estimates spatiotemporally varying and physically interpretable quantities, which are used as coefficients in a set of hydrological balance equations. The hybrid model is fed with meteorological variables and gridcell-level landscape properties and is optimized end-to-end using gridded evapotranspiration, runoff, terrestrial water storage, and snow water equivalent.

By outsourcing the estimation of coefficients to a neural network, we achieve improved local data adaptivity. The simulated fluxes and storage components are realistic and plausible overall, and our approach yields a larger contribution of soil moisture to the terrestrial water storage variations compared to physically-based hydrological models, especially in tropical savanna regions. The presented approach is a proof of concept of the hybrid modeling approach for the global terrestrial water cycle and we acknowledge uncertainties due to data and physical constraints that can be further improved. The presented work is a first step toward the data-driven yet physically constrained estimation of global water storage components and could find broad application in the Earth sciences.

[1] Reichstein et al. (2019, Nature) https://www.nature.com/articles/s41586-019-0912-1

[2] Kraft et al. (2021, HESSD) https://hess.copernicus.org/preprints/hess-2021-211/
Sea Level Rise Impact on Compound Coastal-river Flood Risk in Klaipeda city (Baltic coast, Lithuania) 
Authors: Čepienė Erika , Dailidytė Lina , Stonevičius Edvinas , Dailidienė Inga
Published: March 2022

Due to climate change, extreme floods are projected to increase in the 21st century in Europe. As a result, flood risk and flood related losses might increase. It is therefore essential to simulate potential floods not only relying on the historical but also include future projecting data. Such simulations can give necessary information for development of flood protection measures and spatial planning. This paper analyzes the risk of compound flooding in the Dane River under different river discharge and Klaipeda Strait water level probabilities. Additionally, we examined how water level rise of 1 meter in the Klaipeda Strait could impacts Dane River floods in Klaipeda City. Flood extent was estimated with Hydrologic Engineering Center's River Analysis System (HEC-RAS) and visualized with ArcGIS Pro. Research results show that the rise of the water level in the Klaipeda Strait has a greater impact on the Central part of Klaipeda City, while the maximum discharge rates of the river—on the Northern upstream part of the analyzed river section. Sea level rise of 1 m could lead to the increase of area affected by Dane floods up to three times. Floods can cause significant damage to the infrastructure of Klaipeda Port City, urbanized territories in the City Center and residential areas in the Northern part of the City. Our results confirm that, in the long run, sea level rise will significantly impact the urban areas of the Klaipeda City situated to Baltic Sea coast.
Recurrent episodes of transient deformation in NW Sulawesi, Indonesia
Authors: Nijholt Nicolai , Simons Wim , Broerse Taco , Efendi Joni , Sarsito Dina , Riva Riccardo
Published: March 2022

The Celebes Sea subducts beneath the North Arm of Sulawesi, Indonesia, at the Minahassa trench. Over the past three decades, only a few Mw>7 earthquakes ruptured this plate interface, despite a 40 mm/yr convergence rate. The left-lateral Palu-Koro fault delineates the extent of the overriding plate at the western termination of the Minahassa subduction zone and hosted a Mw7.5 earthquake in September 2018. Observations of post-seismic surface motion following the 2018 event were interpreted in a previous study to result from afterslip that extended underneath the co-seismic rupture plane. A mismatch between observed post-seismic surface motions and predictions from afterslip distributions remained at the North Arm of Sulawesi.

In this study we revisit and reprocess the GNSS observations in NW Sulawesi. We analyse the post-2018 time series to determine whether the post-seismic signal can be ascribed to a single source. This is not the case, as we detect another, yet smaller amplitude signal. We take a Bayesian approach and find that this smaller magnitude signal corresponds to slow slip on the Minahassa subduction interface. This delayed-triggered, (apparently aseismic) slow slip event occurred just east of the 1996 Mw7.9 megathrust rupture.

The 20-year long time series is characterized by four additional periods of transient surface motion. Three of these periods are likely the result of distinct slow slip events and one is a post-seismic signal from the 2008 subduction Mw7.4 earthquake. The presumed slow slip events generally take more than 300 days to quiet down again with a recurrence interval of about five years.
The role of mechanics in the modelling of common rock microstructures
Authors: Tajcmanova Lucie , Podladchikov Yury , Utkin Ivan
Published: March 2022

Understanding rocks at the microscale is essential to comprehending Earth's history and making reasonable predictions about how planetary processes may change in the future.  

Advanced models for complex rock microstructures, such as symplectites or a development of exsolution lamellae, have been developed (Kuhl & Schmid, 2007; Petrishcheva & Abart, 2009). Despite of this recent valuable progress in our understanding of these microstructures, the mechanisms controlling its evolution especially from slowly cooled rocks are still not complete.

Commonly, such models focus solely on the chemical process. Interestingly, mechanics, i.e. stress and pressure redistribution, may also play an important role on microstructure evolution. In this contribution, we investigate the coupled, chemo-mechanical, effect for representative rock microstructures. We provide a comparison between purely chemical vs. coupled chemo-mechanical systems and provide predictions on the evolution of the given microstructures in 3D.

References:

Kuhl, E., Schmid, D.W. (2007). Computational Modeling of Mineral Unmixing and Growth. Comput Mech 39, 439–451.

Petrishcheva, E., & Abart, R. (2009). Exsolution by Spinodal Decomposition I: Evolution Equation for Binary Mineral Solutions with Anisotropic Interfacial Energy. American Journal of Science, 309(6), 431-449.

 
Mapping stable isotopes of oxygen and hydrogen in precipitation, surface waters and groundwaters of Georgia
Authors: Melikadze George , Holko Ladislav , Todadze Mariam , Tchankvetadze Aleksandre , Gventsadze Aleksandre , Gaphrindashvili Merab , Chitanava Ramaz , Chikadze Tornike
Published: March 2022

We present preliminary results of the monitoring of oxygen and hydrogen isotopes in the water cycle of Georgia. The objective of the monitoring is to create maps of isotopic composition of precipitation over Georgia, estimate seasonal amplitudes in the isotopic composition of precipitation, and relationships with the surface and ground waters. Monthly cumulative precipitation samples have been collected since 2013 at 17 sites over entire Georgia at elevations 14 m a. s. l to 2220 m a. s. l. Local meteoric water lines (LMWLs) indicated differences between western, central, and eastern Georgia. Although the LMWLs slopes were mostly not substantially different, only the highest stations (Bakuriani and Gudauri) exhibited slopes that were slightly greater than 8.  The lowest LMWL slope (7.4) was found for stations Chaladidi and Sabueti located in western and central Georgia. LMWL derived for Gudauri (the Greater Caucasus) had a significantly greater intercept (19.9) than at all other sites. Isotopic gradients in delta 18O and delta 2H calculated between stations Tbilisi (430 m a.s.l.) and Gudauri (2220 m a.s.l.) were -0.26 per mil and -1.8 per mil per 100 m, respectively. Monthly samples were collected in several major rivers (Rioni, Mtkvari, Alazani, Iori). Isotopic composition of the greatest Georgian river Mtkvari was best correlated with precipitation in the central Lesser Caucasus (Bakuriani and Sabueti) and southern slopes of the eastern Greater Caucasus (Lagodekhi). One-fourth of groundwater samples were collected in boreholes between mid-July and mid-August and almost all samples from the second half of September (i.e. in the periods without groundwater replenishment) contained evaporated water. Slopes of the evaporation lines were 5.4 and 4.8, respectively.
Derivation of an alternative GRACE Follow-On LRI1B data product
Authors: Müller Laura , Müller Vitali , Misfeldt Malte , Wegener Henry , Hauk Markus , Heinzel Gerhard
Published: March 2022

The Gravity Recovery and Climate Experiment (GRACE) was a space mission from 2002-2017. While the two identical satellites were orbiting the Earth one after the other, the inter-satellite distance variations caused by the Earth's mass distribution were measured. This data can be used to determine the structure of the Earth's gravity field and observe its time-varying component, such as melting ice caps or water storage on land.  In order to continue these useful data streams, a GRACE Follow-On mission was launched in 2018. This successor hosts a novel instrument called the Laser Ranging Interferometer (LRI) for measuring the distance variations with higher precision than the conventional Microwave Instrument (MWI).

The raw measurements of the LRI need to be converted into an intermediate data product before the gravity field recovery can start. The official LRI1B data product is provided by the Science Data System (SDS) based on multiple processing steps. Here, we present an alternative LRI1B data set, that allows investigating different processing strategies and algorithms which might improve the data quality. For instance, our processing uses a different deglitching algorithm for detecting and removing phase jumps,  which are caused by thruster activation of the satellites. Furthermore, we indicate special events like phase jumps, sun-blindings and momentum-transfer-events likely caused by micrometeorites in the quality flag. Additionally, the light time correction used for conversion of the biased range into an instantaneous range is computed differently for the AEI-LRI1B product. Comparing the versions of SDS and AEI allows us to verify and validate the correctness of the officially provided LRI1B of SDS.
Sounding rocket project PMWE for investigation of polar mesosphere winter echoes
Authors: Strelnikov Boris , Staszak Tristan , Seither Philipp , Friedrich Martin , Rapp Markus , Stude Joan , Latteck Ralph , Renkwitz Toralf , Löhle Stefan , Hörner Igor , Eberhart Martin , Fasoulas Stefanos , Gumbel Jörg , Hedin Jonas , Lübken Franz-Josef , Baumgarten Gerd , Fiedler Jens , Strelnikova Irina , Belova Evgenia , Hörschgen-Eggers Marcus ,   PMWE team
Published: March 2022

Polar mesosphere winter echoes (PMWE) are relatively strong radar returns which are regularly observed by mesosphere/stratosphere/troposphere (MST) radars at high latitudes in winter. A sounding rocket project PMWE aimed at investigation of this phenomenon by means of high resolution in situ measurements of all the relevant parameters inside and around the volume probed by the MAARSY radar. Two sounding rocket campaigns were conducted at the Andøya Space (AS, 69 °N, 16 °E) in April 2018 and October 2021, respectively. Two instrumented sounding rockets were launched during each rocket campaing. Both EISCAT in Tromsø and SAURA radar located near the launch site were running throughout the campaign periods. RMR-lidar successfully measured temperature and wind fields on the day of rocket launches in October 2021. In this paper we give an overview and some details of the measurements conducted during the two rocket campaigns and discuss first results.
Modeling Reconnection and Turbulence in the Magnetosphere on Kinetic Scales 
Authors: Macek Wieslaw M. , Gorka Szymon
Published: March 2022

We consider magnetic turbulence using observations from the Magnetospheric Multiscale (MMS) mission on kinetic (ions and electron) scales, which are far shorter than the scales characteristic for description of plasma by magnetohydrodynamic (MHD) theory. We have shown that a break of the magnetic spectral exponent to about -5.5 agrees with the predictions of kinetic theory (-16/3), see Ref. [1]. It is worth noting that the unprecedented very high (millisecond) resolution of the magnetic field instrument allowed to grasp the mechanism of reconnection in the magnetotail on kinetic scales, Ref. [2]. As expected from numerical simulations, we have verified that when the field lines and plasma become decoupled a large reconnecting electric field related to the Hall current (1–10 mV/m) is responsible for fast reconnection in the ion diffusion region both at the magnetopause and in the magnetotail regions. Although inertial accelerating forces remain moderate (1–2 mV/m), the electric fields resulting from the divergence of the full electron pressure tensor provide the main contribution to the generalized Ohm’s law at the neutral sheet (of the order of 10 mV/m), cf. [3]. This illustrates that when ions decouple electron physics dominates. The results obtained on kinetic scales may be useful for better understanding the physical mechanisms governing reconnection processes in various magnetized space and laboratory plasmas.

Acknowledgments. This work has been supported by the National Science Center, Poland (NCN), through grant No. 2021/41/B/ST10/00823.

References

1. Macek, W. M., Krasinska, A., Silveira, M. V. D., Sibeck, D. G., Wawrzaszek, A., Burch, J. L., & Russell, C. T. 2018, Magnetospheric Multiscale observations of turbulence in the magnetosheath on kinetic scales, Astrophys. J. Lett., 864, L29, https://doi.org/10.3847/2041-8213/aad9a8.

2. Macek, W. M., Silveira, M. V. D., Sibeck, D. G., Giles, B.L., & Burch, J. L. 2019a, Magnetospheric Multiscale mission observations of reconnecting electric fields in the magnetotail on kinetic scales, Geophys. Res. Lett., 46, 10,295—10,302, https://doi.org/10.1029/2019GL083782.

3. Macek, W. M., Silveira, M. V. D., Sibeck, D. G., Giles, B.L., & Burch, J. L. 2019, Mechanism of reconnection on kinetic scales based on Magnetospheric Multiscale mission observations, Astrophys. J. Lett., 885, L26, https://doi.org/10.3847/2041-8213/ab4b5a.

 
Modelling the influence of fluvial and glacial erosion on mountain range relief using a stream-power approach
Authors: Liebl Moritz , Robl Jörg , Hergarten Stefan , Stüwe Kurt , Gradwohl Gerit
Published: March 2022

A common issue in geomorphology is to understand how tectonically induced uplift and climatically driven erosion control the height and steepness of entire mountain ranges. The evolution of characteristic landforms towards a hypothetical steady state topography is well studied for mountain ranges eroded by rivers, but a counterpart for glacial conditions is lacking.

Numerical models of landform evolution are increasingly used to determine the topographic imprint of various processes. However, the complexity arising from multiple processes and possible feedbacks between climate, tectonics and topography leads to process-based but computationally intensive numerical models (e.g., iSOSIA), which have limited applicability on large scales. The open source 2D landform evolution model OpenLEM allows seamless coupling of fluvial and glacial erosion with sediment transport, with almost the same computational efficiency as under purely fluvial conditions (Hergarten, 2021). The calculation of water and ice flow dynamics is not required, as the erosion rate is calculated directly from the properties of the topography (i.e., contributing drainage area and local gradient in the flow direction).

Benchmarking against a process-based landform evolution model (iSOSIA, Egholm et al., 2011) shows that the conversion from fluvial to glacial landscapes produces a consistent glacial signal in the topography, despite local differences in the erosion pattern of both models. Starting from an initial fluvial steady-state mountain range, we investigate the evolution of channel networks with progressive glacial landscape transformation over large time scales where the interaction of earth surface processes with tectonics become relevant. The model shows that both the uplift rates and the parameters of glacial and fluvial erosion control the relief and average slope of the glaciated mountain range. This reflects a situation that is not fundamentally different to fluvial landscapes. Different scenarios are investigated under which conditions a glacial topographic signal accumulates over several glacial cycles or whether the glacial imprint is predominantly removed in interglacial periods.

 

Egholm, D. L., Knudsen, M. F., Clark, C. D., and Lesemann, J. E. (2011): Modeling the flow of glaciers in steep terrains: The integrated second-order shallow ice approximation (iSOSIA), J. Geophys. Res., 116, F02012, doi:10.1029/2010JF001900.

Hergarten, S. (2021): Modeling glacial and fluvial landform evolution at large scales using a stream-power approach, Earth Surf. Dynam., 9, 937–952, https://doi.org/10.5194/esurf-9-937-2021.
Variability of Airborne Ultrafine Particles in Number and Size at two Urban Monitoring Stations within Close Proximity to Munich Airport
Authors: Seidler Julius , Nölscher Anke , Friedrich Markus
Published: March 2022

Airports and air traffic can be major sources of ultrafine particles (UFP), next to other anthropogenic and natural sources. UFP are in the size range of 100 nm or less and can be either liquid or solid. When airborne, UFP can have multiple effects on climate, weather and air quality i.e. when impacting cloud formation as condensation nuclei, altering chemical processes in the atmosphere, or being aspirated or taken up.

This project investigates to what extent a large airport and the respective near-ground air traffic contribute to the overall atmospheric UFP mixture. Furthermore, we aim to elucidate the conditions that favour the accumulation of these UFP due to atmospheric transport into adjacent urban areas.

Therefore, we designed and established two monitoring stations around Munich Airport on a North-South axis. Both stations are equipped for continuously measuring UFP by means of a mobility particle size spectrometer (MPSS, 8...800 nm) and a total condensation particle counter (CPC, 8...3000 nm). The setup is completed by meteorological measurements (wind speed and direction, precipitation, solar radiation, humidity, pressure and temperature) which are crucial parameters for exploring transport and mixing of detected UFP in the lowermost atmosphere in exchange with the Earth’s surface and the multiple particle sources in the urban environment.

Officially launched in May 2021, we will present first results showing diurnal and weekly time series of UFP measurements and how they are connected to atmospheric conditions, wind speed and direction in particular as well as airport operation and other emission sectors in the surroundings.

This project is funded by the Bavarian State Ministry of the Environment and Consumer Protection (TLK01U-76519).
Shape Preferred Orientation at scale. From grain-scale aggregates to global mantle convection
Authors: de Montserrat Albert , Faccenda Manuele , Pennacchioni Giorgio
Published: March 2022

Earth's mantle rocks are poly-aggregates where different mineral phases coexist. These rocks may often be approximated as two-phase composites with a dominant phase and less abundant one (e.g. bridgmanite-ferropericlase composites in the lower mantle). Severe shearing of these rocks leads to a non-homogeneous partitioning of the strain between the different phases, with the composite developing a laminar fabric of weak and thin material where strain localizes. The resulting bulk rock is a mechanically anisotropic media that is hardened against normal stress, while significantly weakened against fabric-parallel shear stress.

Due to the large scale difference between the laminar gran-scale fabrics and regional-to-global geological processes, Earth’s rocks are idealised as homogeneous materials instead of multi-phase bodies in numerical models. Thus, a characterization of the rheology evolution of the bulk composite is necessary to better understand large-scale geological processes in which anisotropy may play a fundamental role. Recent three-dimensional numerical (de Montserrat et al. 2021) studies have shown that the degree of lateral interconnectivity of the weak and thin layers is rather limited, thus estimating the rheology of a composite with laminar fabrics by the idealized Voigt and Reuss averages for fibres yield a strong underestimation of the strength of the composite. Instead, we use a combination of numerical results and micro-mechanics to develop an empirical framework to estimate the evolution of the (anisotropic) rheology of such composites.

We apply this rheology framework to study the effects of fabric-induced directional-weakening/hardening on global mantle convective patterns. First order effects of extrinsic anisotropy of lower mantle material observed in our two-dimensional models are a decrease of the wavelength of convective cells, and up to a ~50% increase in the average mantle flow velocity caused by the weakening of the flow-parallel component of the viscosity tensor. The latter is particularly evident in mantle plumes, where the ascent and transfer of hot lower mantle material to lower depths is enhanced by the near-alignment of the weak  fabrics with the plume channel.  
In situ estimation of effective rock elastic moduli by seismic ambient vibrations
Authors: Müller Jozef , Burjánek Jan
Published: March 2022

In this study, we performed a non-invasive ambient noise investigation of unsaturated rock structures in the Bohemian Paradise (Bohemian Cretaceous Basin, Czech Republic). Our study focused on two key topics: 1) An in situ elastic moduli estimate of competent, horizontally deposited sandstone layers using ambient noise array measurements. Recordings were processed using an f-k array analysis, from which frequency-dependent Love and Rayleigh wave dispersion curves, as well as Rayleigh wave ellipticity, were retrieved. Data were inverted for the P- and S-wave velocity profiles, from which Young’s and shear moduli were successfully estimated. 2) A study of the local response of the Kapelník rock tower. We analysed a dataset of ambient noise recordings obtained from the top of the tower and its foot. Information regarding tower oscillation frequencies and directions, together with amplification ratios, were retrieved from a particle motion polarisation analysis and from site-to-reference spectral ratios. Euler-Bernoulli beam theory was also employed for interpreting measured data using elastic moduli estimated from noise array measurements.
Water status monitoring in almond and walnut orchards using random forest and remote sensing
Authors: Kisekka Isaya , Peddinti Srinivasa
Published: March 2022

Water status in almond and walnut orchards is critical in optimizing irrigation management practices since it affects productivity, nut quality, and composition. Water status is frequently determined by the midday stem water potential (SWP) of almond and walnut orchards. Using SWP, allows for determination of the water status of almond and walnut trees, as well as to compare stress between days. SWP measurements are collected on a tree-by-tree basis and do not provide information on spatial variability or the comparison of different time periods because the recorded value is affected by both soil water content and the weather conditions on the day of the measurement, which makes comparisons between different time periods impracticable unless SWP readings are normalized by a baseline (non -water stressed tree under similar environmental conditions). The utilization of a very high-resolution manned and unmanned aerial vehicles equipped with multispectral cameras is being used to record the variability of different spectral features from the plant to the field-scale.

With this research, we aimed to construct a data-driven model based on the Random Forest (RF) ensemble technique to predict SWP spatial variability in drip and sprinkler irrigated almond and walnut orchards in the Central Valley of California, USA. For the training of the RF model, SWP data from three crop seasons from 2019 to 2021 were used along with Landsat-derived evaporation fraction, normalized vegetation index, soil water content from neutron probe, meteorological parameters, and soil properties as covariates. The results demonstrate that the trained model was capable of predicting the SWP at higher spatial resolutions when aerial imagery data were used in conjunction with the trained model. The R2 values for training and validation for almond and walnut orchards were 0.92 and 0.84, respectively. Using the results of the comparison between the pressure chamber measurements and the RF model predictions, we were able to estimate SWP with root mean square errors (RMSE) of 2 and 1.2 bars, mean absolute errors (MAE) of 1.2 and 0.96 bars, and mean bias of 0.62 and 0.48 bars in almond and walnut orchards, respectively. These results demonstrate the capabilities of a machine learning-based RF algorithm for predicting the SWP at higher spatial resolutions by using satellite, aerial imagery, and other meteorological variables as covariates. Spatial maps of SWP can be used by growers to optimize precision irrigation management in orchards characterized by water induced spatial variability.
A High Resolution Topography (HRT) based stochastic model for  multi-year river adjustment post restoration
Authors: Maniatis Georgios , Williams Richard , Hoey Trevor
Published: March 2022

Recent developments in generating High Resolution Topography (HRT), such as UAV photogrammetry, LiDAR and dGPS, have been extensively used in fluvial settings. Most data generation methods are based on commercial sensing and pre-processing tools that are tested by geoscientists in a trial-and-error manner for clarifying: a) their accuracy; and b) their applicability in field settings that are generally outside the range of their factory calibration. For many applications, this involves the concurrent deployment and the cross comparison of more than one sensing techniques. Despite the above, HRT techniques reduce surveying time and costs significantly. The frequency of surveying has increased to a point where it is now common to monitor the development and survival of in-stream bed forms with high resolution Digital Elevation Models (DEMs) on a monthly to annual basis.

In parallel, river scientists have developed dedicated GIS workflows for: a) parameterising the errors during DEM differentiation, thus producing better constrained DEMs of Difference (DoDs); and b) delineating automatically (or semi-automatically) DEMs for the coherent identification of Geomorphic Units (GUs), a term used to distinguish in-stream bed forms and morphological features within the 3 Tier Classification of Wheaton et al., (2015, https://doi.org/10.1016/j.geomorph.2015.07.010).

Here, we use the outputs from the GUT (Geomorphic Unit Tool, Riverscapes consortium) GU delineation as a proxy to predict the change of in-stream geomorphic variability. More specifically, we present a Markov-Chain (MC) model with a state incorporating all the observed GUs and transition matrices built using observed GU changes. The models are then left to converge to a set of probabilities that demonstrates what would happen to the stream if subjected to the observed hydrological forcing for a period that exceeds the surveying plan. To validate the model, we apply it for three successive post-restoration surveys (between 2012-2017) of a 700 m long reach of the Allt Lorgy restoration scheme (Scotland). The first two surveys are used to parametrise the MC transition matrix and the initial states and the third to test the predictions. The results show that the observed GU probabilities are within the predicted uncertainty ranges when the MC chain is modified and a proxy for sediment input is introduced as an additive term.

The MC model is intended to describe post-restoration morphological evolution, and subsequently to provide a tool for predicting morphological change and the end state, assuming constant hydrological forcing.
Evaluation of WRF model PBL schemes in simulating temperature extremes over the Middle-East – North Africa (MENA) region
Authors: Ntoumos Athanasios , Hadjinicolaou Panos , Zittis George , Lelieveld Jos
Published: March 2022

A correct representation of the planetary boundary layer (PBL) is critical to achieve realistic simulations, especially regarding surface variables for regional climate simulations. In this study we examine the sensitivity of the performance of the Weather Research and Forecast (WRF) model to the use of three widely used PBL schemes with emphasis on heat extremes. This study aims (i) to explore the differences among the WRF simulated air temperature and heat extremes resulting from the choice of PBL schemes, (ii) to investigate the physical causes of model biases via the analysis of different variables and, finally, (iii) to reveal the most suitable scheme for application in the Middle-East - North Africa (MENA) domain. The schemes under evaluation are the Mellor–Yamada–Janjic (MYJ), Yonsei University (YSU), and the asymmetric convective model, version 2 (ACM2). We performed 11-year (2000-2010) simulations over the MENA region at 24km resolution. The simulations have been compared with the ERA5 reanalyses for several variables, including maximum and minimum 2-meter air temperature and indices of extremes. Results indicate that model biases strongly vary according to geographic area, with simulations showing good performance in some regions and substantial biases in others. Analysis of different variables like PBL height, moisture and heat fluxes show that differences among the schemes can be linked to differences in vertical mixing strength and entrainment of air from above the PBL.
How long do initial conditions prevail over boundary conditions in streamflow forecasting in South America?
Authors: Petry Ingrid , Fan Fernando , Crochemore Louise
Published: March 2022

In the model-based streamflow forecasting context, initial conditions (ICs) and meteorological forcings (boundary conditions) are two important drivers of predictability. While the meteorological forcings increasingly influence forecasts at long time horizons, ICs’ influence tends to decrease, being nonetheless the predominant source of predictability at short time horizons. Quantifying the period of time when the ICs contribute to streamflow predictability can help researchers and water managers to choose the best forecasting method for each study area and horizon, balancing computational effort and streamflow forecast accuracy. In this work we quantify IC's prevalence time over boundary conditions in natural river flow forecasts in large basins (>1000km²) in South America (SA) from the MGB-SA model, a continental and hydrodynamic version of the MGB conceptual semi-distributed hydrological model. The methodology consisted of forcing MGB-SA with null precipitation as meteorological forcing, so that all the predictability obtained from the experiments was due to ICs. Streamflow experiments had a 215-day horizon, monthly initialization, daily timestep and comprehended the period of 1990 to 2010. The results were compared to the MGB-SA streamflow simulations with MSWEP as observed rainfall. Errors from the hydrological model were thus not considered in this analysis. The prevalence (T50) was estimated by the horizon (from 1 to 215 days) when streamflow predictability was degraded by 50%, i.e. when meteorological forcings start prevailing over ICs. Predictability was estimated by the performance indicator KGE, and the T50 for each of the river reaches of MGB-SA was presented in a map. The T50 map shows that the shortest IC’s prevalence on streamflow predictability is observed on riverheads, ranging from 1 to 3 days. IC's influence increases near the main reaches of the great rivers of SA, reaching up to 10 days on the Iguaçu River and up to 20 days on the Oricono River and Araguaia River. T50 is up to 40 and 90 days on reaches of the Amazon River, Atlantic coast of North Argentina and Pantanal plains. In general, IC’s influence is higher in the main river reaches of basins with flat relief, due to their greater drainage area and the slow response time of the basin.
Improving decadal flood prediction in northern Europe by selecting ensemble members based on North Atlantic Oscillation skill
Authors: Moulds Simon , Slater Louise , Dunstone Nick
Published: March 2022

The ability to predict the frequency and magnitude of flooding at lead times of 1 to 10 years is of great interest to governments and institutions responsible for flood risk management. However, at these lead times there is significant uncertainty about dynamical changes in atmospheric circulation. The current generation of models underestimate the predictable signal of the North Atlantic Oscillation (NAO), the principal mode of variability in North Atlantic atmospheric circulation, leading to low confidence in predictions of regional precipitation and flooding. Recent work has shown that by post-processing a sufficiently large model ensemble, decadal variations in North Atlantic winter climate can become highly predictable (Smith et al., 2020). Here, we investigate whether this NAO-matching technique can be used to improve the skill of flood forecasts at decadal lead times in the United Kingdom. We use a large ensemble of decadal hindcasts consisting of 169 members drawn from CMIP phases 5 and 6, and observed flood records for the period 1960-2015. Following Smith et al. (2020), we adjust the variance of the raw ensemble mean NAO to match that of the observed predictable signal, then select the ensemble members showing the lowest absolute difference with the variance-adjusted ensemble mean. Working only with the selected members (n=20), we supply the ensemble mean precipitation and temperature to a distributional regression model to predict the occurrence and magnitude of winter floods at lead times of 1 to 10 years. We compare these predictions with those from an equivalent model which uses predictors drawn from the full ensemble (n=169) to assess the improvement in predictive skill. Our preliminary results suggest that NAO-matching shows promise at improving decadal flood predictions in northern Europe.

Reference

Smith, D.M., Scaife, A.A., Eade, R. et al. North Atlantic climate far more predictable than models imply. Nature 583, 796–800 (2020). https://doi.org/10.1038/s41586-020-2525-0.
Raman identification of epidote-group minerals in turbiditic sediments from the Bengal Fan (IODP Exp. 354): a complementary tool to better constrain metamorphic grade of source rocks.
Authors: Limonta Mara , Andò Sergio , Bersani Danilo , France-Lanord Christian , Garzanti Eduardo
Published: March 2022

Together with amphibole and garnet, epidote-group minerals are one of the three most important heavy minerals found in orogenic sediments (Garzanti and Andò, 2007). Their chemical composition and optical properties vary markedly with temperature and pressure conditions, and thus provide useful information in provenance analysis on the metamorphic grade of source rocks.

The aim of this study is to devise an efficient and quick method, with micrometric resolution to distinguish among the different species of the epidote group during routine point-counting of heavy-mineral slides, which can be applied on a vast ranges of grain-sizes from fine silt to medium sand.

The geochemical variability of epidote-supergroup minerals from different source rock collected in different sectors of the Alpine orogenic belt was first investigated by coupling Raman Spectroscopy, Scanning Electron Microscopy, and Energy-dispersed X-ray Spectroscopy (SEM-EDS). The geochemical composition, optical properties, and Raman fingerprints of these standard epidote grains were described and in-house database of Raman spectra was created, combining geochemical data and Raman response in the low wavenumbers region and OH stretching bands. A program, written in Matlab® language, has been established which allows to obtain a quick estimate of the amount of iron from the Raman spectra in the clinozoisite-epidote series.

Raman spectra of detrital epidotes contained in turbiditic sediments of the Bengal Fan (IODP Expedition 354) were next compared with Raman spectra of epidote-group standards to determine their composition. The identification and relative amount of detrital epidote, clinozoisite and zoisite in silt- and sand-sized deep-sea sediments contribute to constrain the metamorphic grade of Himalayan source rocks, reconstruct the erosional evolution of the Himalayan orogen, and provide information on climate change and strengthening of the Indian Ocean monsoon throughout the Neogene and Quaternary.

Key words: epidote, provenance, Himalaya, Raman spectroscopy, Microprobe analyses, optical microscope.

Garzanti, E., Andò S., 2007. Plate tectonics and heavy-mineral suites of modern sands. In: Mange, M.A., Wright, D.T. (Eds.), Heavy Minerals in Use, Developments in Sedimentology Series, 58. Elsevier, Amsterdam, pp. 741-763.
Submesoscale dynamics in the central Arctic Ocean during MOSAiC: optimising the use of observations and high-resolution modelling.
Authors: Kuznetsov Ivan , Rabe Benjamin , Fang Ying-Chih , Androsov Alexey , Zurita Alejandra Quintanilla , Hoppmann Mario , Mohrholz Volker , Tippenhauer Sandra , Schulz Kirstin , Fofonova Vera , Janout Markus , Fer Ilker , Baumann Till , Liu Hailong , Mallet Maria Patricia
Published: March 2022

Submesoscale features with profound impact on ocean dynamics and climate-relevant fluxes are frequently observed in the upper ocean including Arctic region. Yet, modelling these features remains a challenge due to the difficulties in the parameterization of submesoscale processes and high resolution required, in particular, in the polar regions. The most effective way to study such phenomena is joint modelling and observational work. Several autonomous observation platforms have been deployed as part of Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) experiment within an approximately 50 km radius around the central observatory. Data from these buoys in combination with data from the central observatory provide a unique opportunity to reconstruct 3D water properties and velocity by constraining a numerical model that resolves the dynamics of the (sub-)mesoscale. It turns out that a minimum root mean square error between results of an optimal interpolation and observations indicates a characteristic length scale of about 7.5 km, corresponding approximately the first-mode barolinic Rossby radius in the area of investigation. However, results of the interpolation are questionable at the sub-mesoscale due to the distribution of the buoy observations in time and horizontal space. In order to describe the in-situ data to achieve a better characterization and understanding of (sub-)mesoscale dynamics we developed and applied a modification of the 3D regional model FESOM-C. The observed temperature and salinity were used to nudge the model to obtain an optimized solution at the resolution of the models. A series of simulations with different horizontal resolutions and model parameters make it possible to analyze the ability of models of this type to reproduce the observed dynamics, to estimate eddy kinetic energy and power spectra, and to compare findings with the observations used to nudge the model. We will show the eddy-induced fluxes and characteristics of eddies along the track of the beginning winter MOSAiC drift.
Assessing damage pattern at depth near the Alpine Fault, New Zealand
Authors: Doan Mai-Linh , Toy Virginia , Sutherland Rupert , Townend John
Published: March 2022

 

The Alpine Fault is the principal component of the plate boundary through the South Island of New Zealand, separating the Pacific and Indo-Australian Plates. It is recognised internationally as an important site for studying earthquake physics and tectonic deformation, as it produces large (M7-8) earthquakes approximately every 330 years and last ruptured in 1717. Therefore, the fault is considered to be late in its seismic cycle. It accommodates dextral-slip at a rate of 26 mm/yr with reverse slip at a maximum rate of 10 mm/yr in its central part, thus exhumed a fossil ductile shear zone, that was damaged brittlely during its exhumation.

 

The central Alpine Fault is the focus of the Deep Fault Drilling Project (DFDP), sponsored by the International Continental Drilling Project, which takes advantage of its globally rare tectonic situation to determine what temperatures, fluid pressures, and stresses exist within a plate-boundary fault in advance of an expected large earthquake. During DFDP phase II in 2014, an ~ 900 m drilled well that encountered an exceptionally high geothermal gradient (120 °C/km was measured in the borehole), was extensively characterized by repeated electric and sonic logs. These logs enable detailed study of fracture patterns near a major fault. The more than 19 km of logs run within the borehole gathered datasets covering, among others, thermal resistivity, sonic velocities, acoustic borehole imaging, and electrical resistivity. They show that the hanging wall is extensively fractured, explaining the high geothermal gradient measured in the borehole by lateral flow of hot water deep seated in the mountains.

 

We particularly focus on seven dual laterolog logs that provide a robust and reproducible dataset from which to determine the positions and orientations of conductive fractures. From these, different patterns of damage could be identified within the well. A first pattern consists of an extensive and dense pattern of isolated fractures that could be identified throughout the borehole. A second pattern suggests that decametric  zones of low resistivity localize damage and focus thermal anomalies. This suggests hierarchy of damage zone evolution of the damage zone of the Alpine Fault. A possible explanation is an initial phase of diffuse fracturing (pattern 1) that is followed by subsequent alteration of the major shear zone, which focuses fluid and heat flow (pattern 2).
Quantifying rainfall forecast uncertainty and error propagation in flash flood and landslide prediction models
Authors: Winkels Bastian , Hofmann Julian , Yildiz Anil , Edrich Ann-Kathrin , Schüttrumpf Holger , Kowalski Julia
Published: March 2022

Extreme weather situations are becoming increasingly frequent with devastating consequences worldwide. Heavy rainfall events in July 2021 caused severe flash floods in western Germany, Belgium and the Netherlands, resulting in a high number of casualties and material damage. The high hazard potential combined with the low reaction times, associated with these events, make it necessary to develop efficient and reliable early warning systems (EWSs) to facilitate the preparation of response strategies. As nowcast precipitation forecasts are continuously improving in both quality and spatial resolution, they become an essential input for flash flood and landslide prediction models and therefore an important component in EWSs. However, the inherent uncertainty of radar-based nowcasting systems are carried over to the output of those prediction models. Therefore, this study aims to analyze the uncertainty sources of nowcasting products of the German weather service (DWD) using the July flood Event 2021 as a case study. More specifically, the objective is to determine whether the quality of precipitation nowcast products is sufficient for usage in physics-based flood or landslide prediction models. Due to the complex nature of weather and rainfall structures as well as their spatio-temporal variability, traditional cell-by-cell comparison of predictions and ground truth is insufficient to quantify forecast quality. To overcome this issue, uncertainties in magnitude, time and space and their respective sources are identified, using techniques from various fields of science. Subsequently, error propagation in flash flood prediction models is analyzed by applying the previously determined uncertainty ranges to a hydrological model.
Impact features on Venus: Modeling craters and splotches
Authors: Ivanov Boris
Published: March 2022

Our team has discovered first impact craters under the thick Venusian atmosphere with radar images during the Venera 15/16 mission. Later Magellan radar images of a better quality allowed us to count all impact craters and to find amazing features, splotches, resulted most probably from “airbursts” - total explosive disruption in flight of small celestial bodies. Splotches could have a central feature (possibly caused by terminal impacts of fragments), or could be diffusive patches of increased (bright) or decreased (dark) areas of changed radar reflectivity. The main explanation so far is that atmospheric shock waves, generated by airbursts, somehow change the surface radar reflectivity, e.g. creating smoother (radar dark) or more rough (radar bright) zones due to reflection of shocks. Size of splotches vary from ~10 km to ~200 km, being comparable with the characteristic atmosphere thickness. The exact mechanisms of air shock wave interaction with the surface is still under debates, but promises to help us better understand the presence of dust/sand/pebbles/boulders at the surface of Venus as well as to estimate mechanical properties of surface rocks. We start a small project to support the issue. The project includes the numerical modeling of atmospheric shock waves on Venus due to cratering impacts and due to airbursts. Our modeling is compared with results published in 1990s-2000s. Airbursts are modeled as a hot spheric volume gas explosion 10 to 40 km above the surface in the Venusian stratified atmosphere. In addition to trivial parameters like maximum pressure, dynamic pressure and the wind speed behind the shock front, necessary for the following analysis of a possible “aeolian” motion of surface’s fines, we try to formulate a general picture of shock wave propagation in the atmosphere after an airburst. We find that the large-scale hot gas bubble from the source zone creates a n x 10 km plume (a kind of a classical “mushroom”), which effectively expands laterally at high altitudes, pushing forward an enhanced shock wave. This wave is looking like a gradual conversion of the main shock wave from a hemispheric one to a conic front, returning back to surface. The other trivial (but not discussed quantitatively) phenomenon is the seismic wave, created by an air shock, but finally overrun the atmospheric shock front. It means that the surface air shock front at large distances arrive after the seismic wave shakes the surface. We plan to investigates all these phenomena and compare models with observations. An interesting possibility seems to be satellite observation of rare meteoroid entry to the Venusian atmosphere, as it now available for terrestrial bolides.