bluuebunny/crossref_metadata_2025 huggingface dataset:
Eulerian and Lagrangian perspectives on a Foehn event in the Alpine region
Authors: Jansing Lukas , Sprenger Michael
Published: March 2020

Foehn-related research has a long-standing tradition in mountain meteorology. In this context, the reason for Foehn air warming and the factors determining the descent of the air into the valleys have gained particular interest. Here, we readdress those research questions by combining a COSMO model hindcast at 1 km horizontal and 10 min temporal resolution with air parcel trajectories for a South Foehn case study in November 2016. The sub-synoptic situation in the model is studied using horizonal cross sections at different levels. Vertical cross sections in the Po valley and along the axes of major Foehn valleys complement the Eulerian analysis.

The selected event is characterized by its long duration, a far northern extent and exceptionally strong gusts. A low-level jet is discernible west of the Alps and a pronounced north-south pressure gradient develops. A striking feature is the strong tilt of the isentropes downstream of the Alpine crest. Trajectories reveal the versatile pathways of air parcels over major Alpine passes before they descend into the Foehn valleys. Differences with respect to upstream ascent and descent are observed for the different valleys. By tracing meteorological variables along the trajectories, the relative importance of adiabatic and diabatic processes for the Foehn air warming is quantified. The properties of air parcels that descend into the valleys or stay at higher levels are contrasted in order to identify factors that determine the descent.

The case study will set the scene for a forthcoming detailed analysis of Foehn flows based on online trajectories that make use of the wind fields at every model time step. The analysis will be extended to a number of cases representing the different South Foehn varieties. We will trace the temperature tendencies due to all diabatic processes (cloud processes, radiation, turbulence) along the trajectories in order to quantify their respective importance for Foehn air warming. First results in this extended framework will be presented.
Land use shapes the relationship between tree cover and carbon stocks in the tropics
Authors: Bhan Manan , Fritz Steffen , Gingrich Simone , Erb Karlheinz
Published: March 2020

Tree cover (TC) and biomass carbon stocks (CS) are key parameters for characterizing the states and dynamics of tropical ecosystems. Despite the presence of several datasets with high spatial resolution, differences among data products prevail and systemic inter-relations between TC and CS remain poorly quantified. Further, the role of land use in explaining disagreements among datasets remains largely unexplored. Here, by combining established spatially-explicit estimates of TC and CS over contemporary timescales, we analyse uncertainties between these two ecosystem parameters across the global tropics (~ 23.4°N to 23.4°S). We quantify land use effects by contrasting actual and potential (ie. in the hypothetical absence of land use) states of vegetation and by correlating TC and CS changes with land use intensity. Our results show that land use strongly alters both TC and CS, with disproportionate impacts on CS and large variations across tropical ecozones. Differences between potential and actual vegetation CS remain above 50% across the tropics except for rainforests (34%). Differences within corresponding TC estimates are more variable, and higher among sparsely-vegetated landscapes (81% for shrublands), highlighting the overwhelming extent of land use impacts. Cross-comparisons across available TC and CS datasets reveal large spatial disagreements. More than a third of all identified co-located TC and CS change datasets show disagreements in the direction of change (Gain vs Loss), and these divergences persist as a function of land use intensities. Our results provide a characterization of the prevailing uncertainty structures of input datasets and the spatial patterns of land use-induced disturbances at the pixel and ecozone-levels. This assumes added significance in light of the stock-taking exercises envisaged as part of the Paris Agreement, the advancement of terrestrial carbon modelling initiatives as well as emerging, novel remote sensing products.
Sliding, flowing, rocking and rolling: Sediment and hazard cascades through mountain landscapes
Authors: Bennett Georgina
Published: March 2020

Mountain landscapes are beautiful, yet hazardous, and vulnerable to climate change and population growth. Not only is the study of these landscapes geomorphically captivating, but it is increasingly relevant to society. Three Grand Challenges in the study of processes, landscapes and hazards in mountain regions are (1) Understanding and predicting the response of earth surface processes to climate (2) Monitoring and early warning of extreme events such as landslides and floods and (3) Accounting for connectivity and feedbacks between hillslopes and channels in landscape evolution and hazards. We need a suite of tools and approaches to address these challenges. Harnessing the growing archive of satellite and aerial photography helps us to study landscape dynamics and response to drivers such as climate over large regions. Innovative sensor technology is needed to understand landscape dynamics at a finer scale and to develop real time warning of extreme events. Finally, we need conceptual models that capture the essence of landscape dynamics and help to forecast hazards as they slide, flow, rock and roll through the landscape.
Influence of horizontal resolution and complexity of aerosol-cloud interactions on marine stratocumulus and stratocumulus-to-cumulus transition in HadGEM-GC31
Authors: Ekman Annica M. L. , Nygren Eva , Svensson Gunilla , Bellouin Nicolas
Published: March 2020

We evaluate the impact of horizontal model resolution (~135, 60 and 25 km, respectively) and different levels of complexity of the aerosol-cloud interaction parameterization (interactive versus non-interactive) on springtime subtropical marine stratocumulus properties and stratocumulus-to-cumulus transition (SCT) using the atmosphere-only version of HadGEM-GC31. Higher resolution and non-interactive aerosols resulted in small, but significantly higher, liquid water contents and lower precipitation rates, in particular over the southern hemisphere. Higher resolution also resulted in a significantly stronger shortwave (SW) cloud radiative effect (CRE). Over the southern hemisphere, non-interactive aerosols also resulted in a stronger SW CRE, but over the northern hemisphere non-significant changes or a weaker SW CRE was obtained compared to the simulation using interactive aerosols. In general, no significant changes in the all-sky SW radiation was obtained. Only the model version with lowest resolution showed a weak tendency of a faster SCT than the other model versions. We conclude that a change in the complexity of the aerosol-cloud parameterization may significantly affect the SW CRE of marine stratocumuli, at least regionally, but the sign and magnitude of the impact will be dependent on the background level as well as the relative change in liquid water and the absolute change in cloud droplet number concentration of the specific model version.
High-resolution simulations over a sub-kilometre scale valley during stable night conditions
Authors: de Bode Michiel , Roubin Pierre , Hedde Thierry , Durand Pierre
Published: March 2020

Complex terrain creates many challenges for modelling aerologic phenomenon. Local variations can have drastic effects on airflows; a good representation of local orography is, therefore, crucial in models. While finer-resolution improves the orographic description in models, it creates a “grey zone” problem for boundary layer schemes. The grey zone, for PBL schemes, is where model-resolution comes close to the size of turbulent structures, leading to the structures being partly resolved and partly sub-grid scale. Research on the grey zone has focused mostly on daytime, neutral-to-unstable conditions. In thinner nocturnal stable layers, local processes become predominant, such as channelling, the simulation of which demands higher resolution in models.

In this research, we run a nested grid version of WRF with a resolution of the innermost domain at 111 m and the coarsest domain at 9 km. We focus on the 1 km wide pre-Alpine valley of Cadarache, a tributary of the Durance River. Previous simulations did not succeed in representing the valley with resolutions of 1 km. We test the indicative value of turbulent length-scales for decisions on the grey zone. Based on the KASCADE 2017 data of several sonic anemometers, placed along the valley thalweg, we determine the turbulent length scales to verify whether the turbulence remains sub-grid or not.

Our first results indicate that turbulent structures in this sub-kilometre scale valley remain well below the model resolution for night time conditions. First runs with 111 m resolution show realistic night time winds and produced the correct overall-structure in the valley. A general under prediction of 2 m-temperatures was found, especially during daytime. Further runs aim to improve forecast precision.  
Effects of changing evapotranspiration and precipitation patterns on Scots pine vitality and mortality
Authors: Hunziker Stefan , Begert Michael , Gessler Arthur
Published: March 2020

Forest decline has been attributed to climatic changes in many parts of the world. Although climate conditions are an undisputed crucial factor affecting tree vitality, open questions remain regarding the relative roles of evaporative demand versus precipitation and the relative importance of individual climate variables.

In recent decades, there was a pronounced decline of Scots pines (Pinus sylvestris) at lower elevations in the inner-alpine Rhône valley in Switzerland. Similar observations were made in other inner-alpine valleys. Tree vitality was not continuously decreasing: single events of strong decrease in tree vitality and high mortality rates were observed in between phases of largely constant vitality levels. However, trees were hardly able to recover from such events in recent decades, resulting in a pronounced decrease in living Scots pines.

Climate-trend signals in the Rhône valley from 1981 to 2018 vary between the seasons. The clearest changes occurred in spring, when a strong climatic shift towards drier conditions was detected with significantly increasing evapotranspiration, decreasing precipitation sums and frequency of precipitation events, increasing duration of dry spells at lower elevations, and increasing diurnal temperature ranges. Relative trends of evapotranspiration are elevation dependent with the highest increase at low elevations. Temperature trends are the main driver towards higher evapotranspiration rates, but humidity and sunshine duration are important drivers too. For seasonal evapotranspiration anomalies, anomalies of temperature, humidity, and sunshine duration are of similar importance.

In previous works on Scots pine mortality in the Rhône valley, mortality events were attributed to prolonged periods of water deficits. However, the occurrence and magnitude of mortality events cannot be explained by droughts only. In case of Scots pines at low elevations in the Rhône valley, factors such as insect infestation and spring frost may strongly impact tree vitality and increase mortality rates.

In summary, climatic conditions changed markedly in the Swiss Rhône valley within the last approximately 40 years, especially in spring and at lower elevations. Hence, the less favorable climatic background conditions result in decreased resilience and recuperative power of the Scots pines to various disturbances, leading to the observed forest decline.
Different response of sea surface temperature and sea ice to precession and obliquity between the two hemispheres
Authors: Wu Zhipeng , Yin Qiuzhen , Guo Zhengtang , Berger André
Published: March 2020

The response of the climate system to astronomical parameters is an important scientific issue, but the internal processes and feedbacks need to be better understood. This study investigates the differences of the climate response to the astronomical forcing between the Northern (NH) and Southern (SH) hemispheres based on a more than 90,000-year long transient simulation using the model LOVECLIM. Our results show that the response of sea ice and sea surface temperature (SST) to precession and obliquity are different between the two hemispheres. Precession plays a dominant role on the NH sea ice. This is mainly due to its response to the local summer insolation and also, to a less degree, the influence of the northward oceanic heat transports. However, obliquity plays a dominant role on the SH sea ice through its influence on insolation and the westerly winds. As far as the SST is concerned, it shows a strong precession signal at low latitudes in both hemispheres. For the SST in the mid and high latitudes, obliquity plays a dominant role in the SH whereas precession is more important in the NH. This is largely due to the different response to insolation and feedbacks related to the different land-ocean distribution in the two hemispheres. Near the Equator, besides the precessional signal, the SST also shows strong half-precessional signal, which can be explained by the unique characteristics of the insolation variations at the Equator.
The influence of overriding-plate velocity on surface topography in subduction zones
Authors: Cerpa Nestor G. , Arcay Diane
Published: March 2020

Topography at subduction zones is the result of multiple processes operating at various temporal and spatial scales. At intermediate wavelengths (~100 km), the models predict the formation of dynamically-induced flexural topography that affects the overriding plate (OP) from the trench to the back-arc [Davies 1981, Crameri et al., 2017]. In our study, we assess how the velocity of the OP affects such a non-isostatic topography by using numerical mechanical models of subduction. We particularly investigate the effects of changes in OP velocity on the evolution of topography.

Our models consist of two converging visco-elastic plates with free surfaces. Friction is imposed along the planar subduction interface. We consider an isoviscous upper mantle with an impermeable barrier at a 660-km depth. We consider cases where the subducting plate (SP) has reached the bottom of the upper mantle and has a stationary motion. The models are performed with the code ADELIM [Cerpa et al., 2014].

We first characterize the main topographic features at a constant OP velocity, using spatial definitions that are based on estimations of the volcanic arc position. The models exhibit the formation of a bulge in the forearc area followed landwards by a depression and a smaller second bulge, the latter two of which are predicted to bracket the arc region. The steady-state distance to the trench of these three flexural features increase with OP velocity. Their amplitude is more sensitive to kinematics when the interplate friction is high and less when the SP viscosity is low.

We next test the effect of sudden changes in OP velocity. An OP acceleration yields a transient topographic tilt, during which the outer forearc quickly subsides whereas the arc region uplifts. The tilt is followed by reverse slower motions. An OP slowdown induces opposite motions. The rates of elevation during the tilt are approximately proportional to velocity variations and mainly sensitive to the SP strength. They are higher than 0.1 mm/yr for velocity changes higher than 1 cm/yr. We suggest that topographic accommodations of OP velocity changes should be considered when quantifying non-isostatic topography.
3D hotspots of marine litter in the Mediterranean: a modeling study
Authors: Soto-Navarro Javier , Jordá Gabriel , Deudero Salud , Compa Montserrat , Alomar Carme , Amores Ángel
Published: March 2020

The 3D dispersion of marine litter (ML) over the Mediterranean basin has been simulated using the current fields from a very high resolution regional circulation model (RCM) as a base to run a 3D lagrangian model. Three simulations have been carried out to mimic the evolution of ML with density lower, in the range of, or higher than seawater. In all cases a realistic distribution of ML sources has been used. Our results show that the accumulation/dispersion areas of the floating and buoyancy neutral particles are practically the same, although in the latter the particles are distributed in the water column with 90% of the particles inside the photic layer. Regarding to the denser particles, they rapidly sink and reach the seafloor close to their origin. The analysis of the temporal variability of the ML concentration shows that the regions of higher variability mostly coincide with the accumulation regions. Seasonal variability occurs at a sub-basin scale as a result of the particles redistribution induced by the seasonal variability of the current field. The comparison with previous studies suggests that the accuracy of numerical studies is strongly dependent on the quality of the information about ML sources, and to the modelling strategy adopted. Finally, our results can be used to guide the design of effective observational sampling strategies to estimate the actual ML concentrations in the Mediterranean.
Modeling of seismic wave propagation around coal mine roadway with presence of excavation-damaged zone
Authors: Czarny Rafał , Malinowski Michał
Published: March 2020

In-seam seismic methods have been widely used in underground coal mine exploitation since early 80’s. They are helpful for identification of stress concentration zones or to locate geological disturbances within the coal seam. Usually, such surveys are optimized to perform seismic tomography. Therefore, sources and receivers are located on the opposite sides of the longwall. Results are produced in form of velocity maps of body-waves for rock-coal-rock medium or maps of group velocity and frequency of Airy-phase of dispersive waves trapped inside the coal seam, so-called channel waves. However, with the above geometry, the high-resolution imaging of the rock mass close to the roadway, including excavation-damaged zone (EDZ), is hampered by the available ray coverage.  In order to overcome this limitation, sources and receivers should be mounted in the same roadway. There is also a fundamental problem contributing to the lack of a robust method to image such area, which is the complexity of the seismic wavefield in the vicinity of the EDZ in a coal seam, where both surface tunnel waves and Rayleigh and Love-type channel waves overlap. We address this problem using numerical simulations. We use finite-difference method and viscoelastic model with petrophysical parameters for coal and host rock layers representative for the Upper Silesia mining district. First, we analyze seismic waves propagation within simple rock-coal-rock model, particularly channel waves dispersion properties. Then, we add a roadway with 3-meter thick EDZ to the model. Velocity and density within the EDZ linearly decrease up to 70% close to the free surface of excavation. By analyzing particle motion close to the free-surface, we observe that for very short wavelengths, the main energy is traveling as a fundamental mode of Rayleigh surface tunnel wave (for horizontal components). However, for longer wavelengths, the main energy is focused around frequency of Airy-phase of fundamental mode of Love-type channel wave. Eventually, we insert 10% Gaussian-shape velocity anomaly with 20 m width in the middle of the roadway to the model and investigate changes in frequency and group velocity of Airy-phase of Love-type channel waves for different offsets. We notice that the group velocity and frequency of maximum energy correspond to the velocity anomaly. For longer offsets, these parameters are approaching theoretical values for undisturbed medium. We conclude that because the group velocity of the Airy-phase is close to the coal S-wave velocity, it can be possible to image the velocity of such wave in the vicinity of the roadway, especially when the thickness of the coal seam is known.  

 

This research is supported by Polish National Science Centre grant no UMO-2018/30/Q/ST10/00680.
Into the soil labyrinth: soil physical structure as a driver of trophic interactions and soil biodiversity
Authors: Erktan Amandine , Or Dani , Scheu Stefan
Published: March 2020

The high diversity of densely packed organisms occurring in small volumes of soils has long been intriguing and we still poorly understand what drives such diversity. Exploring the role of small scale physical structure of the soil, constituting the habitat of these organisms offers unprecedented clues for explaining how organisms interact, notably through trophic interactions and how, in turn, these interactions drive this extraordinary diversity. We review here how restrictions on soil organisms’ ability to sense (e.g. volatiles) and access food resources/prey imposed by the soil physical structure and aqueous habitats within are important drivers for trophic interactions, and consequently, of soil biodiversity. Examples from micro- to macrofauna are presented, focusing on organisms unable to create their own pore space, such as bacteria, fungi, protists, nematodes and microarthropods. Finally, we discuss interdisciplinary challenges to develop research merging soil physics and soil food web ecology.
Graphical models method - implementation to coupling processes in the atmosphere
Authors: Podolská Kateřina , Koucká Knížová Petra , Chum Jaroslav , Kozubek Michal , Burešová Dalia
Published: March 2020

Internal atmospheric waves interact with themselves and/or with the undisturbed atmospheric flow, creating very complicated dynamical system with long-range dependencies. We suspect that regional character of the atmosphere at tropospheric heights may be crucial for explanation of the three different dependencies of foF2 on F10.7cm. We employ multivariate statistic methods applied to daily observational data which were obtained using mid-latitude ionosondes for the investigation of these relationships.

We consider specific and characteristic atmospheric wave generation that correspond to particular climatology of each location “European”, “American” and “Far East”. Specific conditions of each region, involving meteorological phenomena of the location as spectrum of atmospheric wave generation and their propagation. We consider significant difference in low atmosphere climatology as a key explanation of the three classes of ionospheric response to the F10.7cm on long time-scales and suggest that climatology of the troposphere must be taken into account for modelling of the ionospheric response.

Our aim is also to demonstrate that conditional independence graph (CIG) models, representing a robust method of multivariet statistical analysis, are useful for finding a relation between the ionosphere and space weather. This method appears to be more appropriate than correlation analysis between foF2 and geomagnetic and solar indices, especially for longitudinal data for which the characteristics may change over time or time series is interrupted. This method seems more effective to us than correlation analysis or scale analysis.

The final results of our analysis by CIG show that the dependence time shifts were clearly identified, namely +0 day shift in all cases, and +3 / +4 / +5 day shift in the dependence on the solar cycle phase and geographical longitude. Here, we would like to point out that we have analyzed data from ionospheric stations in a rather short span of latitudes, all stations belong to midlatitudes (41.4° N – 54° N) and one would expect either practically same response/dependence of foF2 to F10.7 cm for longitudes and/or geomagnetic dependence as solar and geomagnetic forcing is considered as the most important. However, we have not identified any significant geomagnetically dependence with respect to selected stations and their geomagnetic location. Knowing that ionosphere is strongly coupled with lower-laying atmosphere, we come to the conclusion that climatology of the troposphere may come into play and be responsible for the difference in time-dependencies and time-lags in ionospheric response  to the external solar forcing.
Altitude dependent empirical modeling of the topside ionosphere and plasmasphere using GPS- TEC from Swarm, GRACE-FO and the Sentinel satellites.
Authors: Schreiter Lucas , Stolle Claudia , Arnold Daniel , Jäggi Adrian
Published: March 2020

Slant Total Electron Content (sTEC) measurements can be obtained by dual-frequency GPS
onboard Low Earth Orbiting (LEO) satellites. Within the last few years, a fleet of LEO Satellites at
altitudes ranging from 450 km (Swarm A/C) to 815 km (Sentinel 3) became operational. With
Swarm B, the recently launched GRACE-FO, and the Sentinel 1 and 2 satellites orbiting at
intermediate altitudes, we gain insight into the altitude dependent profile of the topside ionosphere
and plasmasphere.
We make use of this constellation to estimate a global three dimensional model of the electron
density distribution and will also carefully asses the impact of different profile functions, geometry-
free phase center variation maps and the P1-P2 receiver biases. Since the absolute value of the P1-
P2 biases are generally unknown, we focus on a consistent estimation for the whole LEO
constellation.
We will present first results for selected months in 2019 and investigate the day to day variability of
the topside ionosphere and plasmasphere. We also intend to make use of COSMIC-2 data to
improve local time coverage in equatorial regions.
Quantifying burning efficiency in Megacities using NO2/CO ratio from the Tropospheric Monitoring Instrument (TROPOMI)
Authors: Lama Srijana , Houweling Sander , Boersma Folkert , Aben Ilse , Denier van der Gon Hugo , Krol Maarten , Dolman A.J.(Han) , Borsdorff Tobias , Lorente Alba
Published: March 2020

Economic development and rapid urbanization have increased the consumption of fossil fuel in megacities degrading the local air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. It varies with environmental conditions and influences the ratio at which pollutants are emitted, as expressed by the emission factor. Emission factors are an important source of uncertainty in global emission inventories.

To improve the quantification of burning efficiency and emission factors, this study investigates co-located NO2 and CO satellite retrievals from TROPOMI over the megacities of Tehran, Mexico City, Cairo, Riyadh, Lahore and Los Angeles. The TROPOMI instrument was successfully launched by the European Space Agency on 13 October, 2017. It measures atmospheric trace gases with daily coverage and a spatial resolution of 7x7 km2. At this resolution, TROPOMI detects hotspots of CO and NO2 pollution over megacities in single satellite overpasses. The Upwind Background and Plume rotation methods are applied to quantify and evaluate TROPOMI derived ∆NO2/∆CO ratios. TROPOMI derived ∆NO2/∆CO ratios show a strong correlation (r = 0.85 and 0.7) with emission ratios from the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) and Monitoring Atmospheric Chemistry and Climate and CityZen (MACCity) 2018, with the highest ratio for Riyadh and lowest for Lahore. Inventory-derived emission ratios are larger than TROPOMI-derived total column ratios by 60 to 80%. As we will show, this can largely be explained by the limited lifetime of NO2 and the different vertical sensitivity of the TROPOMI NO2 and CO column retrievals. Taking this into account, TROPOMI retrieved emission ratios are generally within 10 to 25% of MACCity. However, larger differences, up to 80%, are found with EDGAR. For Los Angeles, both inventories overestimate NO2/CO ratios compared with TROPOMI. Validation using the air quality monitoring network of Los Angeles supports the lower ∆NO2/∆CO ratios inferred from TROPOMI, indicating that burning efficiencies in Los Angeles are indeed poorer than indicated by the inventories.

 
Mapping of the Gessoso-Solfifera layer and Messinian Erosional Surface in the Northern and Central Adriatic Sea
Authors: Lanzoni Alessandra , Del Ben Anna , Edy Forlin , Martina Busetti
Published: March 2020

Since the discovery of widespread Salt and Gypsum deposits of the Mediterranean Sea in the early ’50s, a large number of scientists tried to unravel the mystery related to this huge deposition of evaporites. Evidence of the later so-called “Messinian Salinity Crisis” (MSC) are largely distributed all around the Mediterranean Basin and widely studied. Although gypsum deposits were recognized in some peripheral or marginal basins (e.g. Sorbas Basin in Spain, Northern Apennines in Italy), mechanism of their deposition and formation are still uncertain. Particularly, the so-called Gessoso-Solfifera formation (GS Fm) was recognized in the ’50s by Selli in several outcrops in Northern Apennines and it is nowadays well known and mapped in the on-shore outcrops.  A regional analysis in the Adriatic Sea is still incomplete, even though a large amount of data is available (2D multichannel seismic lines, boreholes, exploration reports). In the Adriatic Sea, the MSC event can be recognized in the 2D seismic lines as actual thin deposit (maximum GS Fm thickness of about 120 ms TWT) or Messinian erosional surface (MES). In both cases, a strong and clear reflector at the Pliocene base is picked and calibrated by the boreholes reaching its depth. Along the main part of the available seismic profiles it is sometimes very hard to ascribe this strong reflector to the MES or to the presence of a thin gypsum layer.
Calibration of 2D seismic lines with boreholes, also integrated by physical properties derived from geophysical well logs and core data) of the Plio-Quaternary sediments, allowed a detailed seismic facies analysis useful for this purpose. A structural map of the Plio-Quaternary base describes the Plio-Quaternary deformation that affected the study area mainly as Apennine foreland. The thickness map of the GS Fm describes the subsidence and the erosional effect occurred during the MSC. Both these maps are here presented as a first result of a regional study, that intends cover the whole Adria offshore.
Development of Heavy Rain Damage Risk Class and Prediction Function
Authors: Kim DongHyun , Kim Jongsung , Kim Hung Soo
Published: March 2020

This study conducted risk assessment and risk classification on heavy rain damage in the region, then developed the prediction function for heavy rain damage by the risk class. That is to say, the risk index of heavy rain damage by using PSR and DPSIR models was developed for the risk assessment and the risk classes (Red Zone, Orange Zone, Yellow Zone, Green Zone) obtained according to the index. Multiple regression analysis, principal component regression analysis, and artificial neural network(ANN) were applied to develop the prediction function of heavy rain damage. In order to evaluate the prediction performance of the prediction function, we divided heavy rain damage data into the learning section from 2005 to 2012 and the evaluation section from 2013 to 2016. As the results, the ANN using the DPSIR model showed the best prediction performance which has NRMSE of 8.65%. Therefore, the ANN model using the DPSIR was selected as the prediction function in this study. If we can predict the heavy rain damage based on the prediction function, it could be very helpful for disaster preparedness and management.

This research was supported by a grant(2018-MOIS31-009) from Fundamental Technology Development Program for Extreme Disaster Response funded by Korean Ministry of Interior and Safety(MOIS).

 
Potassium application to alleviate drought stress in cassava production: A growth chamber based carbon-13 pulse labelling experiment
Authors: Van Laere Jonas , Willemen Annemie , Ding Yang , Said Hami , Resch Christian , Hood-Nowotny Rebecca , Merckx Roel , Dercon Gerd
Published: March 2020

It is predicted that climate change will cause an increase in frequency and duration of dry spells in Central Africa. This will lower yields of cassava (Manihot esculenta Crantz), a starchy root crop consumed daily by almost 800 million people in the tropics. Potassium has been considered as an important plant nutrient in mitigating the impact of drought stress because of its critical role in stomatal regulation, as an osmolyte, as well as in starch synthesis and assimilate translocation. This study aims to quantify the effects of potassium fertilizer on water use efficiency and translocation speed of new assimilates in water-stressed cassava plants at early bulking stage.

Cassava cuttings (Bailo variety), originating from the Eastern Democratic Republic of Congo, were grown in pots filled with 5 kg of calcium carbonate free sand substrate and fertilized with a complete nutrient solution either high (+K; 1.437 mM K+) or low (-K; 0.359 mM K+) in potassium. All pots were weighed every other to each day to monitor water use and were watered to field capacity. A drought treatment was imposed on half of the plants two months after planting by reducing irrigation amounts by half. Plants were put in an airtight walk-in growth chamber enriched with 13C-CO2 (for 8 h) to trace the translocation of new assimilates. One, nine and twenty-four days after labelling, plants were harvested and δ13C values for different plant organs were analysed.

Plant water use was higher in plants under low potassium nutrition (-K) in the period prior to imposition of drought. Data on biomass production and δ13C and δ18O values of these plants will further help understand whether the observed difference in water use also leads to a difference in water use efficiency. Further, a 13C mass balance will be composed. These data, to be presented at EGU 2020, will provide information on the translocation speed of new assimilates from shoot to root and confirm whether potassium positively affects this process under dry conditions.
Characterize the catchment regime by applying optimal monitoring strategies
Authors: Gonzalez-Nicolas Alvarez Ana , Nowak Wolfgang , Sinsbeck Michael , Schwientek Marc
Published: March 2020

Commonly, chemical catchment regimes are described by a simple regression slope of log-concentrations versus log-discharges measured in the catchment outlet river. The slope value of these plots defines the chemical regime of a catchment. A slope=-1 corresponds to a constant contaminant release subject to dilution by rainfall (an unrealistic extreme but needed as a base flow); whereas a slope=0 means that there are chemostatic effects in the catchment or a washout of contaminants at a constant concentration. However, reality shows that actual time-series measurements of discharge and concentrations conflict with this naive representation since the measurements show temporal hysteresis that defies regression assumptions (i.e. that regression residuals must be uncorrelated). To represent this time interaction beyond regression, we design a simple stochastic time-series model that accounts for fluctuating concentration release and transport with memory. In this work, we also establish how to get the observation data required for a robust estimation of the slope with the least effort. To show the capability of our proposed model and method, we apply a retrospective optimal design of experiments to a high-frequency data series of nitrate concentration (collected by online probes) and discharge of a real catchment in Germany. We thin out the data by applying frequency and event-based monitoring strategies to find out the key components of the strategies that best predict the catchment behavior. Results indicate that our catchment under study (the Ammer catchment in southwestern Germany) is relatively close to a chemostatic type catchment and that our stochastic model, in fact, provides more accurate results for small data sets. Also, optimal data collection schemes for this purpose should be event-based, considering both high and low extremes of discharge that are spread out over time.
Getting it Together: Combining plant and mammal DNA with Lipid Biomarkers from Irish and Scottish Lakes
Authors: Brown Tony , Fonville Thierry , Mackay Helen , van Hardenbroek Maarten , Alsos Inger
Published: March 2020

Lowland lakes in Scotland and Ireland have been heavily impacted by human activity since the Neolithic due to forest clearance, agriculture and lakeside settlement. Whilst plant macrofossils, pollen and other microfossils, especially diatoms, have been able to outline these changes many uncertainties remain about the origin and exact nature of these impacts. Obtaining independent measures of both vascular plants and mammals (and other animals) allows for more taxonomically precise reconstructions and the study of long-term biotic interactions. Lipid biomarkers, such as faecal steroids and bile acids, can both validate the mammal DNA, and also indicate the magnitude of agricultural and human lake inputs into the lake ecosystem. Our initial work focused on small artificial islands (crannogs) common in the Celtic parts of the UK. Unusually strong sedaDNA and lipid biomarker results from both plants and animals are believed to result from the creation of a biogeochemical halo around the crannogs due to the direct input of bone and viscera, rapid organic and clastic sedimentation, and a lack of disturbance. The human activities on the artificial islands, such as slaughter, butchery and feasting, caused severe eutrophication of the smaller lakes, which only partially recovered after the abandonment of the sites. Similar but less pronounced effects can be seen at lake-side settlement sites in larger lakes and away from archaeological sites which reflect catchment-wide influences. This paper will present data from crannogs, lake-side sites and from a new study of lakes on small islands on the Celtic Seaboard. These island sites are being studied to test the narrative of ‘marginality’ and a perceived lack of resilience in small islands during the last two thousand years. Overall our sedaDNA and steroid results complement data from both archaeological excavation, survey and traditional palaeoenvironmental proxies to provide a more detailed and comprehensive image of the environment in which our ancestors were operating, the changes they had on their ecosystems and our inheritance of this today.
In situ geophysical monitoring of liquid water movement in an Alpine snowpack from self potential signals
Authors: Priestley Alex
Published: March 2020

Modelling and monitoring seasonal snow is critical for water resource management, flood forecasting and avalanche risk prediction. Snowmelt processes are of particular importance. The behaviour of liquid water in snow has a big influence on melting processes, but is difficult to measure and monitor non-invasively. Recent work has shown the promise of using electrical self potential measurements as a snow hydrology sensor. Self potential magnitudes can be used to infer both liquid water content of snow and bulk meltwater runoff. In autumn 2018, a prototype self potential monitoring array was installed at Col de Porte in the French Alps, alongside full hydrological and meteorological measurements made routinely at the site. Self potential measurements were taken throughout the following winter, with manual snow pit data obtained in spring 2019. A physically-based snow hydrology model was run for the winter, and an electrical model was coupled to the snow model to create a synthetic set of self potential observations. These synthetic observations were compared to the observed self potential magnitudes to evaluate the effectiveness of the snow model, and to investigate the potential for using the self potential array as part of a coupled geophysical monitoring and modelling system.
Multistage adaptive spectral subtraction of seismic signals
Authors: Rajaeitabrizi Yousef , Salehiozoumchelouei Robabeh , D'Auria Luca , Sánchez de la Rosa José Luis
Published: March 2020

The detection of microearthquakes is an important task in various seismological applications as volcano seismology, induced seismicity, and mining safety. In this work we have developed a novel technique in order to improve the quality and efficiency of STA/LTA based detection of microearthquakes. This technique consists of different stages of filtering employing an adaptive spectral subtraction method, which allows greatly improving the signal/noise ratio.

The implemented technique consists in a preliminary band-pass filtering of the signal followed by different stages of an adaptive spectral subtraction. The spectral subtraction technique is a non-linear filtering which allows taking into account the actual noise spectrum shape. It allows achieving a good filtering even in cases where the signal and noise spectrum overlaps. In order to take into account of the temporal variation in the background noise spectrum, we designed an adaptive technique. We first divide the incoming signals into short temporal windows. Each window is classified as “noise only” or “meaningful signal” (which can be either a microearthquake or any other relevant transient signal) using different features as the signal energy and the zero-crossing rate. Windows classified as “noise only” are continuously accumulated in a dynamic buffer which allows the average noise spectrum to be estimated and updated in an adaptive manner. This technique can be applied on subsequent stages to further improve the signal/noise ratio. This technique has been implemented in Python for the automatic detection of the microearthquakes on both off-line and near-real time data.

In order to check the efficiency of the results, we compared the results of an STA/LTA based automatic detection on the initial band-pass filtered signal and on the spectral subtracted signals after different stages of filtering. A notable improvement of the quality of the detection process is observed when repeated spectral subtraction stages are applied. 

We applied this procedure to seismic data recorded by Red Sísmica Canaria, managed by Instituto Volcanológico de Canarias (INVOLCAN), on Tenerife (Canary Islands), comparing results from the proposed detection algorithm with standard approaches as well as with manual detections. We present an extensive statistical analysis of the results, determining the percentage of correct detections, novel detections, false positives and false negatives after each stage of filtering. First results have shown that this technique is also able to detect automatically microearthquakes which went undetected after a manual analysis.
Understanding the 2017 warm event in North Tropical Atlantic
Authors: Trindade Ana , Matín-Rey Marta , Portabella Marcos , Exarchou Eleftheria , Ortega Pablo , Gómara Iñigo
Published: March 2020

The Atlantic Ocean has suffered tremendous warming during recent decades as a consequence of anthropogenic forcing, modulated by the natural low frequency variability. Special attention should be paid to the high temporal frequency of warm interannual events in the North Tropical Atlantic (NTA) since the early 2000s, resulting in the most intense hurricane seasons on record (Hallam et al., 2017; Lim et al., 2018; Murakami et al., 2018; Klotzbach et al., 2018; Camp et al., 2018). Moreover, NTA sea surface temperature anomalies during boreal spring have been suggested as a potential precursor to the Equatorial Mode (Foltz and McPhaden, 2010ab; Burmeister et al., 2016; Martín-Rey and Lazar, 2019; Martín-Rey et al., 2019). 

This study aims to investigate the development of the 2017 NTA spring-summer warming event, which was the strongest of the last decade, as well as the importance of an accurate ocean forcingin the simulation of this event. For such purpose, a set of four simulations using distinct ocean wind forcing products, namely from the EC-Earth model, ERA-Interim (ERAi) reanalysis and a new ERAi-corrected ocean wind product (ERAstar), have been performed and analysed.The latter consists of average geolocated scatterometer-based corrections applied to ERAi output (Trindade et al., 2019).In this sense, ERAstar includes some of the physical processes missing or misrepresented by ERA-i, and corrects for large-scale NWP parameterization and dynamical errors.

The air-sea processes underlying the onset and development of the warm 2017 NTA event and the wave activity present in the equatorial Atlantic will be explored to determine their possible connection with the equatorial sea surface temperature variability. Furthermore, the comparison between the different experiments allows us to validate the new surface wind dataset and evaluate the importance of accurate, high-resolution ocean forcing in the representation of tropical Atlantic variability.
On the straight and narrow: extreme localization of brittle fault damage and displacement along the Glade Fault Zone, Eastern Fiordland, New Zealand
Authors: Ofman Michael , Smith Steven
Published: March 2020

The southern Glade Fault Zone is a crustal-scale, subvertical dextral strike-slip fault zone on the eastern margin of Fiordland, New Zealand. For a distance of c. 40 km between Lake Te Anau and the Hollyford Valley, the fault cuts plutonic host rocks and has an estimated total dextral separation of c. 6-8 km. We report previously unidentified mylonites, cataclasites, pseudotachylites and fault gouge subparallel to pervasive sets of planar cooling joints in the Hut Creek-Mistake Creek area plutonic suites. The outcropping assemblage of joints and fault rocks record thermal, seismic and rheological conditions in the southern Glade Fault. Here we integrate methods to characterise the fault rocks and fracture damage zone of the southern Glade Fault from Glade Pass to Mt Aragorn. We use (i) EDS (Energy Dispersive x-ray Spectroscopy), XRD (X-Ray Diffraction) and EBSD (Electron Backscatter Diffraction) analysis to describe the mineralogy, kinematics and microstructures of fault rocks and, (ii) drone orthophotography and traditional structural measurements to detail geometrical relationships between structural features. Field mapping of glacially polished outcrops identifies the zone of brittle fault-related damage (i.e. damage zone + fault rock sequence) is up to one order of magnitude narrower than documented along other strike-slip faults with similar displacements, suggesting that the Glade Fault Zone represents an “end-member” of extreme localization of brittle deformation and fault displacement. This is interpreted to result from linkage of pre-existing cooling joints (and mylonitic shear zones), which allowed the younger brittle fault zone to establish its length and planarity relatively efficiently compared to the case of fault nucleation and growth in more isotropic host rocks.