bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Evaluation of a New “Snow Water Index (SWI)” for Accurate Snow Cover Delineation
Authors: Dixit Abhilasha , Goswami Ajanta
Published: March 2020

The current study started by examining the three most established snow indices, namely the NDSI (normalized difference snow index), S3, and NDSII-1 (normalized difference snow and ice index), based on their capabilities to differentiate snow pixels from cloud, debris, vegetation, and water pixels. Furthermore, considering the limitations of these indices, a new spectral index called the snow water index (SWI) is proposed. SWI uses spectral characteristics of the visible, SWIR (shortwave infrared), and NIR (near infrared) bands to achieve significant contrast between snow/ice pixels and other pixels including water bodies. A three-step accuracy assessment technique established the dominance of SWI over NDSI, S3, and NDSII-1. In the first step, image thresholding using standard value (>0), individual index theory (fixed threshold), histogram, and GCPs (ground control points) derived threshold were used to assess the performance of the selected indices. In the second step, comparisons of the spectral separation of features in the individual band were made from the field spectral observations collected using a spectroradiometer. In the third step, GCPs collected using field surveys were used to derive the user’s accuracy, producer’s accuracy, overall accuracy, and kappa coefficient for each index. The SWI threshold varied between 0.21 to 0.25 in all of the selected observations from both ablation and accumulation time. Spectral separability plots justify the SWI’s capability of extraction and removal of the most critical water pixels in integration with other impure classes from snow/ice pixels. GCP enabled accuracy assessment resulted in a maximum overall accuracy (0.93) and kappa statistics (0.947) value for the SWI. Thus, the results of the accuracy assessment justified the supremacy of the SWI over other indices. The study revealed that SWI demonstrates a considerably higher correlation with actual snow/ice cover and is prominent for spatio-temporal snow cover studies globally.
Main active structures in the Barbados accretionary wedge of the Lesser Antilles Subduction: implications for slip partitioning
Authors: Bénâtre Gaëlle , Feuillet Nathalie , Carton Hélène , Jacques Eric , Pichot Thibaud
Published: March 2020

At the Lesser Antilles Subduction Zone (LASZ), the American plates subduct under the Caribbean plate at a slow rate of ~2 cm/yr. No major subduction megathrust earthquakes have occurred in the area since the 1839 and 1843 historical events, and the LASZ is typically considered weakly coupled. At the front of the LASZ, the Barbados accretionary wedge (BAW) is one of the largest accretionary wedges in the world. The width of the BAW decreases northward, owing to the increasing distance to the sediment source (Orinoco river) and the presence of several aseismic oceanic ridges, in particular the Tiburon ridge, that stops sediment progression. Marine geophysical studies conducted to date over the northern part of the BAW (Guadeloupe-Martinique sector) have mostly focused on resolving the geometry of the backstop. However, the structure of the wedge and the mechanical behavior of the subduction interface remain poorly known. Our study aims to describe the geometry of the BAW by a detailed morpho-tectonic analysis in order to place constraints on present and past dynamic interactions between the subducting and overriding plates.

New high-resolution bathymetric data (gridded at 50 meters), CHIRP data and 48-channels seismic reflection profiles were acquired over the BAW in the Guadeloupe-Martinique sector during the CASEIS cruise (10.17600/16001800) conducted in 2016 with the IFREMER vessel N/O Pourquoi Pas? We present results from the analysis of these new data, complemented by existing bathymetry and seismic reflection data acquired by several previous cruises, with an emphasis on the inner wedge domain. The data reveal a 180 km-long linear structure between 15°15’N and 16°45’N latitude, imaged as a positive flower structure on several CASEIS seismic reflection profiles. We interpret this structure as a strike-slip fault and name it the Seraphine fault. The identification of a horse-tail structure linked to an eastward bend of the fault trace at its northern end, as well as left-stepping en échelon folds west of the Seraphine fault, allow to determine the kinematics of the fault as left-lateral strike-slip. The Seraphine fault could root at the toe of the backstop (at least in its central portion). CHIRP data show evidence of folding of recent sedimentary units that are linked to the Seraphine fault, supporting the idea of recent activity. While at odds with the low obliquity of the convergence in this area, the Seraphine fault could be the expression of slip partitioning, similarly to the Bunce fault observed father north along the LASZ where obliquity is much stronger.
Stochastic modeling of extreme El-Niño and La Niña events by nonlinearly coupled oscillators
Authors: Pires Carlos , Hannachi Abdel
Published: March 2020

The El-Niño index behaves as a nonlinear and non-Gaussian stochastic process. A well-known characteristic is its positive skewness coming from the occurrence of stronger episodes of El-Niño than of La Niña. Here, we use the period 1870-2018 of the standardized El-Niño index x(t), sampled in trimesters to analyze the spectral origin of the bicorrelation: sk(t1,t2)=E[x(t)x(t+t1)x(t+t2)] and skewness sk(0,0). For that, we estimate the two-dimensional Fourier transform of sk(t1,t2) or bispectrum B(f1,f2). Its sum over bi-frequencies (f1,f2) equals the skewness (0.45 in our case). Positive and negative bispectrum peaks are due to phase locking of frequency triplets: (f1,f2,f1+f2), contributing to extreme El-Niños and La Niñas respectively. Moreover, the most significant positive and/or negative bispectrum regions are rather well localized in the bispectrum domain. Here, we propose a partition of the El Niño signal into a set of band-pass spectrally separated components whose self and cross interactions can explain the broad structure of bispectrum. In the simplest case where the signal is decomposed into a fast and a slow component (with a cutoff frequency of (1/2.56) cycles/yr.), we verifty that slow-slow interactions (or phase locking) explain most of La-Niñas, particularly at the frequency triplet (1/4.9, 1/15 and 1/3.7 cycles/yr) whereas the fast-slow interactions explain most of El Niños, particularly at the frequency triplet (1/4.9, 1/4.9 and 1/2.5 cycles/yr). In order to simulate this stochastic behavior, we calibrate a set of nonlinearly coupled oscillators (Auto-regressive processes, forced by self and cross quadratic component terms), one for each component. In the case of weak cross-component interactions, and thus weak nonlinearity, the coupling coefficients between spectral-band components are proportional to the corresponding cross-skewnesses, which represent good first guesses in the calibration of the model parameters. The predictability of the model is then assessed, in particular for the anticipation of big El Niños and la Niñas. The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL.
Fiber Optics foR Environmental SEnsE-ing (FORESEE) at Pennsylvania State University
Authors: Martin Eileen , Zhu Tieyuan , Shen Junzhu , Jakkampudi Srikanth , Li Weichen , Dev Ayush
Published: March 2020

The FORESEE Distributed Acoustic Sensing (DAS) Array records roughly 1/3 terabyte of data per day along 5 kilometers of dark fiber optic telecommunications cable underneath the Pennsylvania State University campus. The campus sits in the Allegheny Mountain region of the US, and our aim is to understand urban hydrology and detection of geohazards (particularly karst features). We have verified a number of features of these data similar to prior urban seismic studies, both in ambient noise and in distant earthquake records, which builds further evidence that dark fiber can be a useful tool for seismology in cities.

These data also contain a number of new signals not observed on previous dark fiber arrays. We see a stronger response to air waves than prior experiments. For instance, musical bass lines are clearly observed in the 30-100 Hz range during a concert, and we can see the spatial decay of higher versus lower frequencies throughout the array. This is the first dark fiber array in the eastern US, where thunderstorms occur with some frequency, and we have observed clear recordings of ground motion due to thunder. Source inversion of the waveforms throughout the array leads to locations that show reasonable agreement compared to the National Lightning Detection Network. These thunderquake signals could be an important source of broadband energy for seismic imaging in an area with little earthquake seismicity.

We have performed ambient noise interferometry throughout the array with a variety of pre-processing workflows, but some subsets of the array are strongly affected by nearby sources. With the wide variety of natural and manmade signals in these data, we are working towards further efficient automation to detect repeatable signals that could be used for targeted interferometry, and methods to automate filtering of non-ideal noise sources. As one example of filtering a specific noise, we were surprised the array is able detect the paths of individuals walking along a sidewalk by the fiber. While this array records data on a public college campus, a likely future area of research may include urban areas with a mix of commercial and residential purposes, so we desire tools to remove individual signals as they are recorded. Thus, we have developed a neural network to detect and remove footsteps from data before those data are shared with researchers. To encourage others working on urban seismic acquisition to remove similar signals, we are generalizing these methods for footstep removal to different scales.
Assessing future uncertainties: earthquake tsunami hazard in the Java trench, Indonesia.
Authors: Salmanidou Dimitra , Heidarzadeh Mohammad , Guillas Serge
Published: March 2020

Historical earthquakes in the Java subduction zone have given genesis to tsunami affecting the southwest coasts of the island of Java, in Indonesia. The most recent earthquake on the 17th of July 2006, has given rise to a tsunami that killed more than 600 people. The tsunami was difficult to escape due to the small amount of ground shaking, which could have acted as an early warning, and due to the epicentre being very close to the shorelines, giving insufficient time for response. Historical data and scientific studies give little evidence for mega-thrust events in the Java trench, however such possibilities are not excluded and could have a devastating impact in the region. This work aims to assess the tsunami hazard occurring from a range of earthquake scenarios in the subduction zone. Taking as a benchmark the 2006 event, we initially validate our modelling approach against the wave observations recorded at three tide gauges. We then expand our work to account for future earthquake scenarios and their tsunamigenic consequences in the southern coasts of Java island. Bathymetry displacement is computed using the Okada elastic dislocation model. The nonlinear shallow water equation solver JAGURS is employed for the modelling of wave propagation. Our objective is to quantify the uncertainty of such events by using statistical surrogates: fast stochastic approximations of the model that can explore the likelihood of thousands of tsunami scenarios in a few moments of time. Gaussian process emulators are utilised to predict maximum wave amplification occurring from varying parameter distributions such as the moment magnitude of an earthquake. The resulting tsunami hazard footprints can be used in conjunction with existing socio-demographic information to assess tsunami risk in vulnerable areas. The end-data can eventually be used to inform policy making for better disaster mitigation planning.
Revealing small scale dynamics at the altitude of noctilucent clouds
Authors: Baumgarten Gerd , Chau Jorge , Fiedler Jens , Gerding Michael , Lübken Franz-Josef , Schäfer Britta
Published: March 2020

Observing noctilucent clouds (NLC) by lidar and camera from ground reveals smallest scale structures of tens of meters and their evolution in the vertical and horizontal direction.
At the altitude of nocltilucent clouds (approx. 83 km) these structures are generated by microphysical processes affecting the ice particles, pure fluid dynamics, or a combination of both. On centennial time scales the NLC are linked to microphysical changes, mostly induced by changes of the available water vapor. On scales of hours to days the clouds are linked to temperature or the large scale flow. On scales of minutes the structures are often wave-like and associated with gravity waves and turbulence. 
For timescales below a few minutes only sparse observations were previously available. To systematically investigate the structure of NLC on such scales we make use of the ALOMAR RMR-lidar, located in Northern Norway at 69°N, that is detecting NLC with sub-second resolution since 2011. We have developed a classification scheme to identify the most important features on timescales of a few seconds. 
Furthermore we use a combination of lidar, radar and camera that allows studying simultaneously the horizontal and vertical scales. We will present new results from lidars and cameras that look at noctilucent clouds above ALOMAR and Kühlungsborn (54°N) with different scattering angles. The observations are used to investigate the mechanisms that generate the extraordinary appearance of NLC when observed by naked eye. 
Relevance of the magnetic field model for studying the beaming cone of the Jovian decameter emission
Authors: Galopeau Patrick , Boudjada Mohammed
Published: March 2020

We use five different Jupiter’s magnetic field models (O6, VIP4, VIT4, VIPAL and JRM09) to investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field B and its gradient ∇B in the source region. The most recent model JRM09, proposed by Connerney et al. [Geophys. Res. Lett., 45, 2590-2596, 2018], was derived from Juno’s first nine orbits observations. The JRM09 model confirms the results obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL): the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. The same assumptions were made as in the previous studies: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where B and ∇B are not parallel. As a consequence, the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of B and ∇B is greater in the North (~10°) than in the South (~4°).
Simulation of frictional heat generation due to underground motion
Authors: Uslar Andreas
Published: March 2020

Frictional energy generating during an earthquake has been well studied in the last decades and quite a few laboratory experiments have been carried out recently with the objective to quantify and describe this type of energy in a better way.  In our research we modelled the temperature rise during a simulated seismic event and the consequent equivalent heat released using the ANSYS® Mechanical software. Our approach is using the Finite Element Method to model a symmetrical fault plane where several parameters such as density, pressure, structural and thermal material characteristics are set according the conditions of a compressional tri-axial test. Natural and forced models were explored applying the Mohr-Coulomb failure criteria. Using a temporal window similar to a realistic situation, we are capable to observe the differences that occur during the stick-slip behavior in the co-seismic rupture process. On the other hand, the time lapse allows us to observe model and infer how the heat is generated and transferred around the fault plane. As a preliminary result, a variation of approximately 1.5°C was obtained simulating the conditions for a laboratory induced micro-seismic event modelled as a tri-axial test under 10 MPa of confining pressure and 20 MPa as vertical pressure, with velocities in the order of 1.5 mm/s.
On the initial conditions of the ICON-D2-EPS ensemble: An analysis in terms of spread and skill.
Authors: Marsigli Chiara
Published: March 2020

The COSMO-D2-EPS ensemble is running operationally at DWD at a resolution of 2.2 km. In the framework of the transition from the COSMO to the ICON model for the limited-area applications, the ICON-D2-EPS ensemble is starting its pre-operational phase. Therefore, the perturbation strategy developed for COSMO-D2-EPS is adapted to the new ensemble.
In this work, the focus is on the initial conditions, which are provided by the first 20 analyses generated by a LETKF ensemble data assimilation system (KENDA).
The KENDA analyses present the advantage of providing perturbed initial conditions to the convection-permitting ensemble, where the perturbations contain also the information on the convection-permitting scale uncertainties. On the other hand, the KENDA analyses are optimised for the purpose of data assimilation. The ensemble of analyses which is the most suitable for initialising the next data assimilation cycle may not be the same which is the most suitable for initialising the weather forecast ensemble, e.g. in terms of spread.

The analyses generated by the KENDA cycle are evaluated from the point of view of their usage for ensemble forecasting initialisation. Their spread is computed for different variables, assessing also how it varies with the spatial scale and with the weather situation. Furthermore, the spread is compared to the error of the analyses and of the forecasts, in order to assess the ability of the analyses to describe the initial condition uncertainty. 
The growth of the differences between the members during the first hours of the forecasts is studied as well, in dependence on the weather situation.

The final aim of this work is to identify possible improvements for deriving the ensemble initial conditions from the KENDA analyses.
Transport of planktic foraminifera by ocean currents in the Uruguayan margin
Authors: Kruijt Anne , Mair Andrew , Nooteboom Peter , von der Heydt Anna S. , Ziegler Martin , Aze Tracy
Published: March 2020

Fossils of planktic foraminifera are found in marine sediments and are widely used as a proxy for past ocean conditions. The habitat of these unicellular marine zooplankton ranges from tropical to polar regions and is mostly located in the upper mixed layer of the ocean. The foraminifera form a calcium carbonate ’shell’ around their cell during their lifespan. When they die, foraminifera lose their ability to control their buoyancy and their shells sink to the ocean floor. It is often assumed that the proxies which are derived from the shells in sediment cores represent ocean conditions above the location of deposition. However, foraminifera are transported by ocean currents, both during and after their lifespan. Hence, the paleoclimatic conditions recorded from their shells may originate far from the core site, generating large footprints in foraminifera-based paleoclimatic proxies. 

In this project, we quantify the influence of the transport by ocean currents on the proxy signal of foraminifera found at core sites in the Uruguayan margin of the Punta del Este basin. This is a region where two western boundary currents meet: The southward flowing Brazil current and the northward flowing Malvinas current. We use a high resolution (0.1° horizontally) ocean general circulation model to track virtual sinking particles and the local oceanic conditions along their pathways. These model results are compared to proxy- and species analysis from the core sites. We found that offsets in modelled proxy signals due to transport in the Uruguayan margin are strongly linked to the relative position of the core site to the Brazil-Malvinas confluence. These offsets are most pronounced in the tails of the temperature distributions where they can reach up to +/- 7°C at sites located in the confluence zone. Species analysis from core tops taken slightly north of this region show more cold water species than reflected by the modelled temperature distributions, suggesting biological activity and nutrient availability not taken into account in the model play an important additional role in the relative abundances of species.
Our model simulations have provided both a first order insight into the potential proxy-signal offsets in highly dynamic ocean regions and show that understanding of the interplay between transportation effects and the biological activity of foraminifera is crucial for the interpretation of these proxies.

 
Southern Hemisphere jet stream: emergent constraints on future shift in zonally varying framework
Authors: Li Camille , Ogawa Fumiaki , King Martin , Tjiputra Jerry , Jensen Bjørnar , Johannsen Klaus
Published: March 2020

IPCC climate models (CMIP3/5) predict a poleward shift of the Southern Hemisphere (SH) jet stream under global warming, with a large spread across the models. Efforts to find emergent constraints for the future jet shift (response) have relied on the simulated present-day jet position (observable). However, this has been investigated primarily in a zonal-mean framework, which averages out important zonal asymmetries. In this study, we revisit the problem allowing for variations in the longitude, height and season of the response to gain a better physical understanding of the nature of the future jet shift in individual models. Results from a manual data analysis will help guide an exploration of the problem using a big data approach, in particular, the application of a genetic algorithm that finds optimal solutions based on iterative random selection within large sample data spaces.
Coupling bottom-up process modeling to atmospheric inversions to constrain the Siberian methane budget
Authors: Goeckede Mathias , de Vrese Philipp , Brovkin Victor , Koch Frank-Thomas , Roedenbeck Christian
Published: March 2020

Methane (CH4) is one of the most important greenhouse gases, but unexpected changes in atmospheric CH4 budgets over the past decades emphasize that many aspects regarding the role of this gas in the global climate system remain unexplained to date. With emissions and concentrations likely to continue increasing in the future, quantitative and qualitative insights into processes governing CH4 sources and sinks need to be improved in order to better predict feedbacks with a changing climate. Particularly the high northern latitudes have been identified as a potential future hotspot for global CH4 emissions, but the effective impact of rapid climate change on the mobilization of the enormous carbon reservoir currently stored in northern soils remains unclear.

 

Process-based modelling frameworks are the most promising tool for predicting CH4 emission trajectories under future climate scenarios. In order to improve the insights into CH4 emissions and their controls, the land-surface component of the Max Planck Earth System model, JSBACH, has been upgraded in recent years. In this context, a particular focus has been placed on refining important processes in permafrost landscapes, including freeze-thaw processes, high-resolution vertical gradients in transport and transformation of carbon in soils, and a dynamic coupling between carbon, water and energy cycles. Evaluating the performance of this model, however, remains a challenge because of the limited observational database for high Northern latitude regions.

 

In the presented study, we couple methane flux fields simulated by JSBACH to an atmospheric inversion scheme to evaluate model performance within the Siberian domain. Optimization of the surface-atmosphere exchange processes against an atmospheric methane mixing-ratio database will allow to identify the large-scale representativeness of JSBACH simulations, including its spatio-temporal variability in the chosen domain. We will test the impact of selected model parameter settings on the agreement between bottom-up and top-down techniques, therefore highlighting how sensitive regional scale methane budgets are to dominant processes and controls within this region.
Contrasting responses of soil fungal communities and soil respiration to the above‐ and below‐ground plant C inputs in a subtropical forest
Authors: Shi Lingling , Feng Wenting , Jing Xin , Zang Huadong , Mortimer Peter Edward , Zhou Xiaoming
Published: March 2020

The roles of soil fungal diversity and community composition in regulating soil respiration when above‐ and below‐ground plant carbon (C) inputs are excluded remain unclear. In the present study, we aimed to examine: (i) how does the exclusion of above‐ and below‐ground plant C inputs affect soil respiration and soil fungi singly and in combination? and (ii) are changes in soil fungal diversity aligned with changes in soil respiration? A field experiment with manipulation of plant C inputs was established in a subtropical forest in southwest China in 2004 with litter removal and tree stem‐girdling to exclude inputs of the above‐ and below‐ground plant C, respectively. In 2009, we measured the rates of soil respiration with an infrared gas analyser and soil fungal community structure using Illumina sequencing. We found that the rates of soil respiration were reduced significantly by litter removal and girdling, by similar magnitudes. However, they were not decreased further by the combination of these two treatments compared to either treatment alone. In contrast, litter removal increased the diversity of soil fungal communities, whereas girdling decreased the abundance of symbiotrophic fungi but increased the abundance of saptrotrophic and pathotrophic fungi. These changes in soil fungal community might initiate CO2 emission from soil C decomposition, offsetting further decline in soil respiration when plant C inputs are excluded. These results revealed that the exclusion of the above‐ and below‐ground plant C inputs led to contrasting soil fungal communities but similar soil function. Our findings suggest that both above‐ and below‐ground plant C are important in regulating soil respiration in subtropical forests, by limiting substrates for soil fungal growth and altering the diversity and composition of soil fungal community.
Simulation of soil organic carbon stock and greenhouse gases emission from Perennial Energy Crops cultivation cycle in Italy with ECOSSE model: from establishment to removal
Authors: Martani Enrico , Pilla Marcello , Ferrarini Andrea , Amaducci Stefano , Hastings Astley
Published: March 2020

Soil organic carbon (SOC) is an important carbon pool sensitive to land use change (LUC). There are concerns that at the end of PECs cultivation cycle, the re-conversion of these crops back to arable land could negatively impact the SOC stock. However, a positive effect of reconversion on SOC is possible, due to the high amount of C added to the soil with the disruption of belowground biomass (BGB) during re-conversion process. In this study, C storage potential in SOC and BGB of six perennial energy crops (PECs) was measured in a 11 years old field trial in Italy before its reconversion to arable land. SOC dynamics and greenhouse gases (GHGs) emission were measured in the first two years after the reconversion. SOC and GHG measurements were compared to ECOSSE soil carbon model predictions (run for a LUC from arable land to PECs and re-conversion to arable land) to understand SOC dynamics. After 11 years of cultivation, PECs significantly increased SOC stock respect to arable land. In average, BGB accounted for the 68% of total carbon stocked by PECs. The ECOSSE soil carbon model successfully simulated the dynamics of SOC pool and the GHGs emissions from soil after the re-conversion of PECs.
Mitigating climate change effects on forest growth using planting stock with high adaptive genetic capacity: results from Abies alba (Mill.) provenance trials at the southeastern distribution limit
Authors: Mihai Georgeta , Alexandru Alin-Madalin , Birsan Marius-Victor , Mirancea Ionel , Garbacea Paula , Stoica Emanuel
Published: March 2020

European silver fir (Abies alba Mill.) is among the most important forestry species in Europe. In Romanian Carpathians, it covers about 5% of the forests area and almost two-thirds of its distribution is located in Eastern Carpathians, which is the southeastern edge of its distribution in Europe.
The most recent climate change scenarios for Europe suggest increases in mean annual temperature of 1-4 °C by the end of this century (Meinshausen et al. 2011). In the context of global warming, the populations living at the edge of the species distribution will be the first facing the climate change effects. In these regions, as the southeastern Europe, the main constrains are increasing the temperature, extended drought events and water availability. Forest species are particularly sensitive to climate change because the long life-span of trees does not allow for rapid adaptation to environmental changes (Lindner et al. 2010). 
In this context, the aim of this study was to analyze the drought response of 51 European silver fir populations from: Romanian Carpathians (26), Austria (4), Germany (3), France (3), Italy (4), Slovakia (3), Czech Republic (3), Poland (1) and Bulgaria (4)  to strong drought events which have occurred in this region, in the last 30 years. The populations are tested in three provenances trials established in Romania, in 1980; two of them being located outside and one within the optimum climatic of species. The most drought years, with severe or extreme drought periods, have been identified based on the standardized precipitation index (McKee et al. 1993). The growth response of the silver fir populations to the drought events was evaluated by calculating four parameters, namely: resistance, recovery, resilience, relative resilience (Lloret et al. 2011). Results reveled that the general trend was towards decrease the stem radial growth of silver fir during the last 30 years. The provenance x year interaction was not significant which means high provenances stability over time. Significant differences were found among silver fir provenances in terms of ring width, latewood proportion, resistance, recovery and resilience in drought years. There are provenances which have highlighted high productivity and high tolerance to drought, which could be used in reforestation work, breeding and conservation programs. The radial growth of silver fir provenances was negative affected by the temperature increase during vegetation period and positive by previous autumn-spring precipitations. Therefore, the forest management strategy to mitigate negative impacts of climate change should be based on the knowledge of the intraspecific genetic variation and selection of the best performing and adapted planting stock for each region.
Inter-Calibration of nine UV sensing instruments over Antarctica and Greenland since 1980: impact on global UV cloud albedo trends
Authors: Weaver Clark , Labow Gordon , Wu Dong , Bhartia Pawan K. , Haffner David
Published: March 2020

A suite of NASA/NOAA UV (340nm) sensing satellite instruments, starting with Nimbus-7 SBUV in 1980, provides a global long-term record of cloud trends and cloud response from ENSO events. We present new method to inter-calibrate the radiances of all the SBUV instruments and the Suomi NPP OMPS mapper over both the East Antarctic Plateau and Greenland ice sheets during summer. First, the strong solar zenith angle dependence from the intensities are removed using an empirical approach rather than a radiative transfer model. Then small multiplicative adjustments are made to these solar zenith angle normalized intensities in order to minimize differences when two or more instruments temporally overlap. While the calibrated intensities show a negligible long-term trend over Antarctica, and a statistically insignificant UV albedo trend of -0.05 % per decade over the interior of Greenland, there are small episodic reductions in intensities which are often seen by multiple instruments. Three of these darkening events are explained by boreal forest fires using trajectory modeling analysis. Other events are caused by surface melting or volcanoes. We estimate a 2-sigma uncertainty of 0.35% for the calibrated radiances. Finally, we connect the estimated radiance uncertainties, derived from our calibration approach, to the tropical and midlatitude UV cloud albedo trends.
Juno’s Microwave Imaging of Jupiter’s Atmosphere at Multiple Depths
Authors: Bolton Scott , Levin Steve , Janssen Michael , Ovafuso Fabiano , Zhang Zhimeng , Arballo John , Li Cheng , Wong Michael , Orton Glenn
Published: March 2020

The Juno mission has revolutionized our view of Jupiter's atmosphere, interior and magnetosphere. The Juno Microwave Radiometer (MWR) explores the dynamics and composition of Jupiter's atmosphere, probing deeper than possible from Earth-based telescopes or any previous spacecraft. Typically, observations cover a full range of latitude for each specific longitude the spacecraft passes over during each orbit. During the 19th perijove pass, the spin of spacecraft was oriented perpendicular to the orbital plane providing the first time the capability of mapping a wide range of longitudes using the MWR instrument. These observations are the first time a simultaneous map of Jupiter's deep atmosphere has been created at multiple levels of pressure ranging from 1 to >100 bars. The resulting 3-dimensional map uniquely reveals formation, evolution, and roots of storms and atmospheric features. The data will be presented and compared with visible light and infrared maps for context.
Recurrence Plot based entropies and their ability to detect transitions
Authors: Kraemer K. Hauke , Marwan Norbert , Wiesner Karoline , Kurths Jürgen
Published: March 2020

Many dynamical processes in Earth Sciences are the product of many interacting components and have often limited predictability, not least because they can exhibit regime transitions (e.g. tipping points).To quantify complexity, entropy measures such as the Shannon entropy of the value distribution are widely used. Amongst other more sophisticated ideas, a number of entropy measures based on recurrence plots have been suggested. Because different structures, e.g. diagonal lines, of the recurrence plot are used for the estimation of probabilities, these entropy measures represent different aspects of the analyzed system and, thus, behave differently. In the past, this fact has led to difficulties in interpreting and understanding those measures. We review the definitions, the motivation and interpretation of these entropy measures, compare their differences and discuss some of the pitfalls when using them.

Finally, we illustrate their potential in an application on paleoclimate time series. Using the presented entropy measures, changes and transitions in the climate dynamics in the past can be identified and interpreted.
Complementing urban rainfall/flood monitoring using low-cost citizen observatories: first result and challenges
Authors: Verbeiren Boud , Tondeur Kim , Seyoum Solomon , Pireaux David
Published: March 2020

Internet-of-Things (IoT) technology is evolving rapidly and within the frame of the FloodCitiSense.eu project we are exploring the potential of low-cost citizen observatories for the monitoring of intense rainfall and pluvial flooding in three pilot cities: Brussels, Rotterdam and Birmingham. In this presentation we focus on the Brussels pilot in which we evaluate the added value of low-cost rainfall sensors (developed by Disdrometrics, Delft – The Netherlands) to complement the existing network with 16 professional rain gauge (Flowbru.be – Open data). The main objective is to obtain a higher density of rainfall measurements enabling to capture, in near real-time, intense rainfall events. Due to the high degree of imperviousness of the city landscape intense rainfall is often the trigger for a fast hydrological response, sometimes causing pluvial flooding in Brussels. The low-cost rainfall sensors are disdrometers, counting the number and estimating the size of raindrops. The low-cost sensors make use of LoRa technology to send their data in near real-time to the central database. In Brussels 20 low-cost sensors were installed with help of citizens, mainly aiming at filling the “gaps” of the existing rain gauge network. To enable direct evaluation some of the low-cost sensors where installed next to professional rain gauges. We evaluate the performance of the low-cost sensor by (1) direct comparison (intensity and volumes) with the professional rain gauges of the Flowbru.be network, (2) comparing the spatial pattern of measured rainfall intensities, with and without low-cost sensors, to radar rainfall maps and (3) the reliability of the low-cost measurements. In this contribution we will focus on the first results from the test phase (October 2019 – January 2020). Next we also elaborate on the challenges involved in the deployment of a network of low-cost sensors. The FloodCitiSense.eu project is a close collaboration with TU Delft, Imperial College London, IIASA, Disdrometrics, VUB SMIT-imec, LGiU, EGEB and is funded within the ERA-NET Smart Urban Future programme (Urban Europe ENSUF).
On the accumulation of enhanced vertical shear of the horizontal wind in the upper troposphere / lower stratosphere
Authors: Kaluza Thorsten , Kunkel Daniel , Hoor Peter
Published: March 2020

The extratropical transition or mixing layer indicates the chemical transition from well mixed troposphere to the stably stratified stratosphere . It is located around the classical defitinition of the tropopause and is defined by a set of unique tracer-tracer correlations. Physically, it is the result of cross-tropopause transport, however, many processes associated with the formation and maintenance of the extratropical transition layer with its very distinct features as well as the importance of its overlap with the tropopause inversion layer (TIL) are still a subject of research. In particular, turbulent motions in the UTLS and their relative importance for the ExTL are still unknown.

 

We analyse the top end of the spectrum of vertical shear of the horizontal wind, S2, in the troposphere and stratosphere as a proxy for turbulent motions. For this we use 10 years of ECMWF (European Centre for Medium-Range Weather Forecasts) ERA5 reanalysis data. We focus our analysis on the Northern Hemisphere extratropical UTLS, and more specifically on the Northern Pacific and Atlantic sectors. We find strong signatures of high S² just above the tropopause in both region. However, differences between the two regions are evident due to difference in the jet stream characteristics in these two regions . The areas of strong vertical wind gradients appear as regions of reduced Richardson numbers in the elsewhere highly dynamically stable lowermost stratosphere. We compare features of these regions in the model output with known characteristics of the extratropical transition layer to see if they are linked.

 

This work was supported by DFG grant no. KU 3524/1-1.
On the modeling of thermohydrodynamic and biogeochemical processes in the inland water objects
Authors: Gladskikh Daria , Mortikov Evgeny , Stepanenko Victor
Published: March 2020

Currently, one-dimensional and three-dimensional models are widely used to model thermohydrodynamic and biochemical processes in lakes and water rеreservoirs. One-dimensional models are highly computationally efficient and are used to parameterize land water bodies in climate models, however, when calculating large lakes and reservoirs with complex geometry, such models may incorrectly reproduce processes associated with horizontal heterogeneity. This becomes especially important for the prediction of water quality and euthrophication.

A three-dimensional model of thermohydrodynamics and biochemistry of an inland water obect is presented, which is based on the hydrostatic RANS model [1-3], and the parameterization of biochemical processes is implemented by analogy with the scheme for calculating biochemistry in the one-dimensional LAKE model [4]. Thus, the three-dimensional model is supplemented by a description of the transport of substances such as oxygen (O2), carbon dioxide (CO2), methane (CH4), as well as phyto- and zooplankton. The effect of turbulent diffusion and large-scale water movements on the distribution of a methane concentration field is studied.

To verify the calculation results, idealized numerical experiments and comparison with the measurement data on Lake Kuivajärvi (Finland) were used.

The work was supported by grants of the RF President’s Grant for Young Scientists (MK-1867.2020.5, MD-1850.2020.5) and by the RFBR (18-05-00292, 18-35-00602, 20-05-00776). 

References:
[1] Mortikov E.V. Numerical simulation of the motion of an ice keel in stratified flow // Izv. Atmos. Ocean. Phys. 2016. 52. P. 108-115.
[2] Mortikov E.V., Glazunov A.V., Lykosov V.N. Numerical study of plane Couette flow: turbulence statistics and the structure of pressure-strain correlations // Russian Journal of Numerical Analysis and Mathematical Modelling. 2019. V. 34, N 2. P. 119-132.
[3] D.S. Gladskikh, V.M. Stepanenko, E.V. Mortikov, On the influence of the horizontal dimensions of inland waters on the thickness of the upper mixed layer. // Water Resourses. 2019. 18 pages. (submitted)
[4] Victor Stepanenko, Ivan Mammarella, Anne Ojala, Heli Miettinen, Vasily Lykosov, and Vesala Timo. LAKE 2.0: a model for temperature, methane, carbon dioxide and oxygen dynamics in lakes. Geoscientific Model Development, 9(5): 1977–2006, 2016.
Hierarchical Bayesian modelling of hydrological extremes
Authors: Zorzetto Enrico , Canale Antonio , Marani Marco
Published: March 2020

Hydrological time series are characterized by variability over a wide range of temporal scales. While lower frequency variability has been widely studied in hydrology, it is seldom explicitly accounted for in extreme value models. This limitation arises as a consequence of the limited data available for inference on extremes, and especially in the case of hydrological processes exhibiting relevant variability over yearly or longer time scales. Motivated by the statistical analysis of extreme rainfall, here we present a Bayesian hierarchical model developed for estimating the probability distribution of extreme values of intermittent random sequences. This method relaxes the asymptotic assumptions ordinarily employed in extreme value theory, and models the entire underlying parent distribution of the events. The hierarchical structure of the model explicitly separates the ‘fast’ time scale of event occurrence from a lower-frequency variability component, which is modeled through latent-level variables. In the case of rainfall, this latent level represents the inter-annual variability in the distributions of both of event magnitudes and in the frequency of their occurrence. Inference is conducted numerically by means of a Bayesian approach, thus allowing for the inclusion of relevant prior information, and leading to a fully probabilistic description for the quantities of practical interest, such as high return times quantiles. Here we test the proposed model by means of a simulation study, and include an application to rainfall data obtained from long instrumental records. Our results show that this approach I) leads to improved inference in the case of relatively short datasets, and II) can benefit from prior information on the physical processes involved in order to reduce estimation uncertainty. Moreover, we show that the presence of low frequency variability leads to statistical models characterized by heavier tails, thus underlining the importance of low frequency variability in determining the extreme-value statistical properties even in the case of stationary models. While the focus of our application in on rainfall extremes, the structure of the model is quite general and applications to other environmental variables are discussed.
Tsunami Observer: automatic system for estimate of tsunamigenicity of an earthquake
Authors: Karpov Viacheslav , Kolesov Sergey , Nosov Mikhail , Bolshakova Anna , Nurislamova Gulnaz , Sementsov Kirill
Published: March 2020

In this talk the fully automatic system for estimate of tsunamigenicity of an earthquake is presented. The system is focused on simplicity and speed with usage of minimum of input data. The input dataset for the system includes (1) earthquake coordinates, (2) earthquake depth, (3) seismic moment, (4) focal mechanism. We use datasets provided by USGS and GEOFON. Upon receiving earthquake data the system performs the following consecutive actions. At first, the vector field of co-seismic bottom deformation is obtained using earthquake fault parameters and empirical relationships. Then the initial elevation in tsunami source is calculated and estimation of Soloviev-Imamura tsunami intensity is performed. Initial elevation is calculated taking into account vertical and horizontal components of bottom deformation, local bathymetry (GEBCO) and smoothing effect of water layer. An auxiliary study was conducted to obtain relationship between potential energy of initial elevation of water in tsunami source and intensity of resulting tsunami. More than 200 historical events from HTDB/WLD and NGDC/WDS databases was statistically processed. The obtained relationship is used to assess the intensity of tsunami generated by earthquake under consideration. Finally, if event is considered significant (energy > 109 J), the numerical simulation of propagation of tsunami waves is performed. As a result of numerical simulation, animations of wave propagation, distribution of maximum tsunami heights, and water surface time-histories in a number of given points are produced. Details of implementation, physical constraints, future development of system as well as 2-years experience of the system operation will be discussed during the talk.

Acknowledgements

This work was supported by the Russian Foundation for Basic Research, projects 20-07-01098, 20-35-70038, 19-05-00351.
Tipping Points in Antarctic Climate Components (TiPACCs)
Authors: Langebroek Petra , Østerhus Svein , Consortium TiPACCs
Published: March 2020

Recently, several of the West Antarctic ice shelves have experienced thinning driven by ocean-induced basal melting. The consequent reduction in buttressing of the Antarctic ice sheet causes an increase in the discharge of the grounded ice into the ocean.

In our new Horizon 2020 project “Tipping Points in Antarctic Climate Components” (TiPACCs) we address these processes by assessing the possible switch from “cold” to “warm” Antarctic continental shelf seas (tipping point 1) and the possible shift in the stability regime of the Antarctic ice sheet from a stable to an unstable configuration (tipping point 2). Investigating the coupled ocean-ice system, the tipping points and their feedbacks, will provide insight into the threat of abrupt and large sea-level rise. In TiPACCs we use a suite of state-of-the-art ocean circulation and ice sheet models, in stand-alone and coupled set-up. The proximity of the simulated tipping points will be determined by existing remote sensing and in-situ observations. The possibility that the tipping points were crossed during the Last Interglacial will be investigated and allow for a better understanding of how the ocean-ice system works during warmer than present-day conditions.

This EGU contribution will present the ideas, the planned work, and the consortium of TiPACCs.