bluuebunny/crossref_metadata_2025 huggingface dataset:
The stratospheric response and surface influence in a bias-corrected model.
Authors: Tyrrell Nicholas , Karpechko Alexey , Rast Sebastian
Published: March 2020

We investigate the effect of systematic model biases on teleconnections influencing the Northern Hemisphere wintertime circulation. We perform a two-step nudging and bias-correcting scheme for the dynamic variables of the ECHAM6 atmospheric model to reduce errors in the model climatology relative to ERA-Interim. The developed scheme is efficient in removing errors in model’s climatology. In particular, large negative bias in December-February mean zonal stratospheric winds is reduced by up to 75%, significantly increasing the strength of the Northern Hemisphere wintertime stratospheric polar vortex. <!-- I think calling increase in vortex strength ”a result” somewhat shifts the focus. The result is reduced error, not increased strength. I mean technically it is the same, but perception of the result is a bit different. What do you think? -->The bias-corrections are applied to the full atmosphere or stratosphere only.

We compare the response of bias-corrected and control runs to internal stratospheric variability and surface forcings that are important on seasonal timescales: Siberian snow cover in October; the Quasi-Biennial Oscillation (QBO); and ENSO. We find the bias-corrected model has the potential for a strengthened and more realistic response to the teleconnections, either in the stratospheric or surface response. In particular, the bias-corrected model has a strong QBO teleconnection which modulates the extratropical polar vortex and sea level pressure variability in a manner similar to that seen in observations. The Siberian snow forcing with the stratosphere-only bias-corrections also leads to an enhanced surface response relative to the control.<!-- Given considerable remaining biases in tropospheric waves in the stratosphere-only bias corrected run I would not overemphasize the results in this particular run especially because full bias-corrected run does not show large surface response. But it is Ok to mention this result in the abstract. --> The mechanism behind the sensitivity of the teleconnections to model biases is discussed.
Estimation of multi-period glacier mass balance in southeast Tibet using high-resolution remote sensing observations
Authors: Zhou Yushan , Li Zhiwei , Li Xin , Zheng Donghai
Published: March 2020

Glaciers in the southeastern part of the Tibet Plateau (TP) have experienced the most rapid mass loss over the High Mountain Asia. Hence, a multi-period investigation on the mass balance with focus on how glaciers evolve is imperative for better understanding of the glacier dynamics responding to climate change. Taking the Yanong glacier connected with a proglacial lake in the southeast TP as an example, we estimate the glacier mass budget at multiple-year and interannual timescales via reproducing a multiple-period DEM datasets, including KH-9 (1975), SRTM (2000), TanDEM-X (2011−2014) and SPOT-7 (2015) DEMs. We also estimate the penetration depths of both X- and C-band radar using Pléiades stereo images and TanDEM-X data , which are found to be 3.2 m and 4.5 m on average in this area. The results show that the Yanong glacier has been subject to an accelerated mass loss over the past four decades (1975−2015), and the tendency of surface thinning spread from low altitudes to high altitudes. Specifically, the mass balance of the Yanong glacier changes from −0.50 ± 0.13 m w.e./a (1974−2000) to −0.95 ± 0.13 m w.e./a (2000−2012) and to −1.02 ± 0.31 m w.e./a (2012−2015) at the multi-year timescale. A serious surface subsidence event is noted in areas that are about 2 km away from the glacier fronts after 2012, which are possibly caused by the internal/basal melting or collapsing. After further analyzing the evolution process of the proglacial lake, we found that the continuous disintegration of the glacier fronts may be the main reason for the accelerated mass deficit.

 
A decision-theoretic approach to sustain public protection under climate change based on ensembles of future hazard developments
Authors: Enigl Katharina , Matulla Christoph , Frank Fabian , Schlögl Matthias , Schmid Franz , Schnetzer Ingo
Published: March 2020

In large parts of the world, an increasing number of damaging events caused by previously rare extreme weather phenomena is being observed. This poses a challenge to those responsible for civil protection of how to sustain current safety levels under accelerated climate change. The aim of this study is to contribute to meeting these challenges by providing methods to determine anticipatory strategies for decades of sustainable protection. 

This endeavor requires the identification of weather-related hazard processeson on the one, and the establishment of corresponding future hazard development corridors on the other hand. The former, so-called Climate Indices (CIs), are determined by blending damage events and spatiotemporal highly resolved meteorological data for three different regions in the Austrian Alpine region and six different process categories via multivariate statistical analyses.  The derivation of hazard development corridors describing future changes in risk landscapes requires ensembles of regional climate projections, in which the occurrence of corresponding CIs is detected.

Results are incorporated into the decision-making process and processed together with experts in civil protection. The determination of optimal, sustainable protection strategies is based on decision-theoretical techniques and the application of the expected utility theory (Bernoulli principle).

The feasibility of integrating hazard development corridors into decision-making processes, as well as the satisfactory implementation of established procedures, is demonstrated by the most comprehensive civil protection project in Austria to date. The results are consistent and show significant differences between near (2036-2065) and far future (2071-2100) time periods, as well as between the threat levels corresponding to the "climate-friendly" path of humanity and those associated with the "business as usual" scenario. The results are in line with the European Floods Directive by ranking linear measures behind resettlement and retention measures.
New approaches in tree phenomics using IoT technologies and AI machine learning : the TreeTalker network
Authors: Valentini Riccardo
Published: March 2020

Climate variability and extremes are observed with increasing amplitude and frequency in almost any continent and extensive tree mortality and widespread forest dieback is an increasing and emergent global concern although direct attribution of extensive tree mortality to warming or drying episodes is still under debate (IPCC AR5). Although tree dieback is a combination of causes, including pathogen/pest invasions, genetic responses and management factors, still climate anomalies, even at shorter time scales, can trigger predisposition factors that may lead to irreversible tree decline and dieback.  Despite there are a number of methods for addressing simultaneously tree functions such as photosynthesis and transpiration at leaf level or at canopy scale the same information at high temporal frequency and at individual tree scale is not yet widely diffused. Taking advantage of new technology and latest developments in sensor science, (e.g Internet of Things) we have developed a new device able to measure simultaneously important tree parameters. The parameters are: 1) tree radial growth, as indicator of photosynthetic carbon allocation in biomass; 2) sap flow, as indicator of tree transpiration and functionality of xylem transport; 3) xylem moisture content as indicator of hydraulic functionality 3) light penetration in the canopy in terms of fractional absorbed radiation and 4) light spectral components related to foliage dieback and physiology, 5) tree stability parameters to allow real time forecast of potential tree fallings. We will present a synthesis of data coming from different forest locations including natural, urban and artificial plantations and discuss the capabilities to extend such network at global scale. Examples of AI machine learning application to ecophysiological data will presented. Finally we discuss the possibility of using the TreeTalker network in large scale phenomics applications for individual tree responses to climate change impacts and identification of plant traits.
The impact of two decades of land-use changes in potential ecosystem services supply in a Portuguese municipality - Coimbra
Authors: Amorim Leitão Inês , Santos Ferreira Carla Sofia , Dinis Ferreira António José
Published: March 2020

Land-use changes affect the properties of ecosystems, and are typically associated with decreasing ability to supply services, which in turn causes a decrease in the social well-being. Urbanization is identified as one of the main causes of ecosystem degradation, once it is considered an artificial space that replaces natural areas.This study investigates the impact of land-use changes during 20 years (1995-2015) on the potential supply of ecosystem services in Coimbra municipality, central Portugal. The assessment was based on the evaluation performed by 31 experts familiar with the study area, through questionnaires. The experts ranked the potential supply of 31 ecosystem services, grouped in regulation, provisioning and cultural services, for the several land-uses existent. Experts performed a qualitative evaluation, considering ‘strong adverse potential’, ‘weak adverse potential’, ‘not relevant’, ‘low positive potential’ and ‘strong positive potential’. The qualitative evaluation was converted into a quantitative classification (-2, -1, 0, 1, 2). Quantitative values were then used to develop an ecosystem services quantification matrix and to map the information in the study area, using Geographic Information Systems (GIS). An urban expansion from 14% to 18% was recorded over the last 20 years. Agricultural land decreased 8% due to conversion into forest (4% increase) and urban areas (4% increase). This has led to a decrease in the supply of provision (e.g. food) and regulation services (e.g. flood regulation). In fact, over the last years, recurrent floods have been increasingly noticed in Coimbra city. On the other hand, the growth of forest areas has led to an increase in general ESs supply. The adverse impacts of urbanization were partially compensated by enlarging the benefits provided by forest areas, which is the land-use with greatest ESs potential supply. In order to support urban planning and develop sustainable cities, it is essential to quantify the potential supply of ecosystem services considering local scale and characteristics.
EU COST Action ES1404-HarmoSnow
Authors: Arslan Ali Nadir
Published: March 2020

The European Cooperation in Science and Technology (COST) promoted and funded the Action ES1404 called “A European network for a harmonized monitoring of snow for the benefit of climate change scenarios, hydrology, and numerical weather prediction,” or “HarmoSnow” (2014-2018). With 29 European COST countries and the international partners Andorra and Taiwan (https://www.cost.eu/actions/ES1404/) HarmoSnow coordinated efforts towards harmonized snow data processing and handling practices by promoting new observing strategies. The vision was to connect different communities, facilitating data transfer, upgrading and enlarging knowledge through networking and linking them to activities in international agencies and global networks (www.harmosnow.eu).

The main aim of HarmoSnow was to enhance the capability of the research community and operational services to provide and exploit quality-assured and comparable observation data on the variability of the state and extent of snow. The overall objectives were (1) Establish a European-wide science network on snow measurements for their optimum use with interactions across disciplines and expertise, (2) Assess and harmonise practices, standards and retrieval algorithms applied to snow measurements, (3) Develop a rationale and long term strategy for snow measurements and their dissemination, (4) Advance snow data assimilation in NWP and hydrological models, (5) Establish a validation strategy for climate, NWP and hydrological models against snow observations and foster its implementation, (6) Training of a new generation of scientists on snow science and measuring techniques with a broader and more holistic perspective.

We will present outcomes from the HarmoSnow activities and discuss how to move forward.
Passive seismic interferometry in XSoDEx experiment in northern Finland
Authors: Kozlovskaya Elena , Afonin Nikita , Karjalainen Jari , Heinonen Suvi , Buske Stefan
Published: March 2020

There is the problem that application of controlled-source seismic exploration is not always possible in nature protected areas. As an alternative, application of passive seismic techniques in such areas can be proposed. In our study we show results of application of passive seismic interferometry for mapping the uppermost crust in the area of active mineral exploration in northern Finland using the data recorded during XSoDEx (eXperiment of SOdankylä Deep Exploration) project. The objectives of the project were to obtain a structural image of the upper crust in the Sodankylä area of Northern Finland in order to achieve a better understanding of the mineral system at depth. Within XSoDEx, a combined seismic reflection and refraction survey was organised by Geological Survey of Finland, University of Oulu, Finland (Oulu Mining School and Sodankylä Geophysical Observatory) and TU Bergakademie Freiberg, Germany. The vibrotrack of TU BAF was used as a source. The experiment was performed during July and August 2017 resulting in an approximately 80 km long seismic profile line. The seismic refraction data were simultaneously recorded by 60 vertical- and 40 three-component wireless autonomous receivers along an extended line around the reflection spread with maximum offsets of around 10 km. During night time, the receivers were recording passive seismic data. Thus the XSoDEx experiment provided a good opportunity to verify results of passive seismic interferometry with controlled-source seismic data, to identify limitations of this technique in areas of generally low level of high-frequency anthropogenic noise and to propose possible improvements of known techniques. Analysis of the data and theoretical modelling demonstrated that the dominating sources of ambient noise are non-stationary and have different origin in different parts of XSoDEx lines. In addition, the length of passive data for cross-correlation was limited to several hours and the long data recording period is usually considered as one of the main conditions for seismic interferometry applications. In order to obtain reliable Empirical Green Functions (EGF) from such short-term and non-stationary data, we applied a special technique (signal-to-noise ratio stacking). The calculated EGFs were inverted in order to obtain S-wave velocity models along XSodEx lines down to a depth of several hundreds metres. The obtained results are S-wave seismic velocity models of the upper crust in Northern Finland that agree well with geological data and complement the results of reflection seismic data interpretation.
Metamorphic differentiation via enhanced dissolution along high strain pathways
Authors: Moore Jo , Beinlich Andreas , Piazolo Sandra , Austrheim Håkon , Putnis Andrew
Published: March 2020

Metamorphic differentiation, resulting in the segregation of minerals into compositional bands, is a common feature of metamorphic rocks. Considering the ubiquitous nature of compositionally layered metamorphic rocks, the processes that are responsible for metamorphic differentiation have received very little attention. The studied outcrop, located within the Bergen arcs of southwestern Norway, preserves the hydration of an anorthositic granulite at amphibolite-facies conditions. The amphibolite-facies hydration is expressed as both a statically hydrated amphibolite and a shear zone rock, defined by the interlayering of amphibolite with leucocratic domains. Detailed petrography, quantitative mineral chemistry and bulk rock analyses are applied to investigate compositional variation with assemblage microstructure. Within the outcrop, quartz-filled fractures and their associated amphibolite alteration haloes, are observed crosscutting the granulite. These fractures are demonstrated to be relict of the initial fluid infiltration event. The fracture assemblage (quartz + plagioclase + zoisite + kyanite ± muscovite ± biotite) is equivalent to that occurring locally within leucocratic domains of the shear zone. Due to the textural and compositional similarities between quartz-filled fractures and leucocratic domains, the compositional layering of the shear zone rock may be directly linked to fracturing during initial fluid infiltration.

            Mass-balance and thermodynamic calculations indicate quartz-filled fractures and compositional differentiation of the shear zone form by internal fractionation rather than partial melting or precipitation of minerals from an eternally derived fluid. The process of internal fractionation within the shear zone is attributed to enhanced dissolution along fracture pathways, resulting in the loss of MgO, Fe2O3 and K2O within leucocratic domains. These elements, being more mobile in the fluid, are then transported and ultimately either precipitated in amphibolite lithologies or escape with the fluid, resulting in an overall volume loss in the shear zone. This inferred fluid connectivity combined with the enhanced local dissolution indicates the presence of a continuously replenished fluid along fracture pathways, leading to the overall conclusion that the mass transfer processes that result in metamorphic differentiation of the shear zone lithologies are dependent on both continuous fluid flux and heterogeneous strain distribution.
On the separation of co- and post-seismic signals due to large earthquakes from GRACE observations
Authors: Li Jin , Chen Jianli , Wang Song-Yun , Tang Lu , Hu Xiaogong
Published: March 2020

Satellite gravimetry observations from GRACE (Gravity Recovery and Climate Experiment) and GRACE Follow-On are widely used to study the co-seismic and post-seismic deformations caused by large earthquakes. Temporal gravity changes from GRACE provide good constraints to investigate the fault slips of large earthquakes especially for oceanic areas. However, reliable retrieval of seismic signals is still challenging due to large uncertainties and limited spatial and temporal resolutions of GRACE observations. To extract the co- and post-seismic signals from GRACE, the time series fitting method based on least squares is commonly used. In the time series fitting, the earthquake occurrence time parameter (t0) is usually set at the mid-month point, since most available GRACE time-variable data are monthly solutions. Nevertheless, a lot of large earthquakes did not occur exactly at mid-month. By simulative tests, we demonstrate that the commonly used mid-month approximation for the fitting parameter t0 can cause noticeable bias for the seismic signal extraction. The several-days deviation in the parameter t0 leads to obvious difference for the time series fitting of seismic signals, since the post-seismic changes are rapid and significant within a short period after the earthquake. With the case study of the 2004 Mw9.1 Sumatra-Andaman earthquake (which occurred on December 26), we indicate that the bias due to the commonly used mid-month t0 approximation reaches above 10 percent amplitude of the extracted co-seismic signals. Thus the exact date for the fitting parameter t0 should be used for more reliable separation of the co- and post-seismic signals from GRACE observations.
Significant production of ClNO2 and possible source of Cl2 from N2O5 uptake at a suburban site in eastern China
Authors: Xia Men , Wang Tao , Peng Xiang , Wang Weihao , Yu Chuan , Sun Peng , Li Yuanyuan , Liu Yuliang , Xu Zhengning , Wang Zhe , Xu Zheng , Nie Wei , Ding Aijun
Published: March 2020

ClNO2 and Cl2 can affect atmospheric oxidation and thereby the formation of ozone and secondary aerosols, yet their sources and production mechanisms are not well understood or quantified. In this study we present field observations of ClNO2 and Cl2 at a suburban site in eastern China during April 2018. Persistent high levels of ClNO2 (maximum ~3.7 ppbv; 1 min average) were frequently observed at night, due to the high ClNO2 yield (φ(ClNO2), 0.56 ± 0.20) inferred from the measurements. The φ(ClNO2) value showed a positive correlation with the [Cl-]/[H2O] ratio, and its parameterization was improved by the incorporation of [Cl-]/[H2O] and the suppression effect of aerosol organics. ClNO2 and Cl2 showed a significant correlation on most nights. We show that the Cl2 at our site was likely a co-product with ClNO2 from N2O5 uptake on aerosols that contain acidic chloride, rather than being produced by ClNO2 uptake, as previously suggested. The Cl2 yield (φ(Cl2)) derived from the N2O5 uptake hypothesis exhibited significant correlations with [Cl-] and [H+], based on which a parameterization of φ(Cl2) was developed. The derived parameterizations of φ(ClNO2) and φ(Cl2) can be used in models to quantify the nighttime production of ClNO2 and Cl2 and their impact on the next day’s photochemistry.
Redox state affects methane flux in a northern boreal flark fen
Authors: Koskinen Markku , Finné Hanna , Virtanen Tarmo , Lohila Annalea , Laiho Raija , Laurila Tuomas , Aurela Mika
Published: March 2020

Long-term continuous measurement of reduction-oxidation (redox) potential is an emerging tool for analysing ecosystem status. Redox processes are intrinsically linked to methane (CH4) production and consumption in soils. Under highly reducing conditions, acetate and carbon dioxide (CO2) are reduced into CH4, while at less reducing conditions, CH4 is readily oxidised into CO2. These oxidation processes do not necessarily require oxygen; other electron acceptors such as nitrate (NO3-) and iron can also be used by microbes. The prevalence of different electron acceptors and donors is reflected in the redox potential of the soil solution which can be measured. Thus measurements of soil redox potential could in principle be used for predicting CH4 flux.

We measured soil redox potential at 4 depths between 5 and 40 cm continuously over one growing season on nine measurement plots on three different microsites (flark, lawn and string), in a north boreal flark fen, while concurrently measuring CO2 and CH4 flux of the same plots using the manual chamber method. Flux measurements were conducted five to seven times per week from late June to late September, 2019. Along with the redox potential, water table level (WTL), air and soil temperature (Tair, Tsoil) and several vegetation characteristics were also measured.

Tsoil was found to be the major control of the momentary CH4 flux, but after standardizing the flux to 10 C using the Lloyd-Taylor equation, including the soil redox potential was found to significantly (p < 0.001) improve the prediction of the flux over a model incorporating only WTL and momentary Tsoil.

This is an initial step towards inclusion of redox potential as a continuous variable describing the processes active in the soil into CH4 production/consumption models.
Automatic Flood Monitoring based on SAR Intensity and Interferometric Coherence using Machine Learning
Authors: Ghosh Binayak , Motagh Mahdi , Haghshenas Haghighi Mahmud , Maghsudi Setareh
Published: March 2020

Synthetic Aperture Radar (SAR) observations are widely used in emergency response for flood mapping and monitoring. Emergency responders frequently request satellite-based crisis information for flood monitoring to target the often-limited resources and to prioritize response actions throughout a disaster situation. Flood mapping algorithms are usually based on automatic thresholding algorithms for the initialization of the classification process in SAR amplitude data. These thresholding processes like Otsu thresholding, histogram leveling etc., are followed by clustering techniques like K-means, ISODATA for segmentation of water and non-water areas. These methods are capable of extracting the flood extent if there is a significant contrast between water and non-water areas in the SAR data. However, the classification result may be related to overestimations if non-water areas have a similar low backscatter as open water surfaces and also, these backscatter values differentiate from VV and VH polarizations. Our method aims at improving existing satellite-based emergency mapping methods by incorporating systematically acquired Sentinel-1A/B SAR data at high spatial (20m) and temporal (3-5 days) resolution. Our method involves a supervised learning method for flood detection by leveraging SAR intensity and interferometric coherence as well as polarimetry information. It uses multi-temporal intensity and coherence conjunctively to extract flood information of varying flooded landscapes. By incorporating multitemporal satellite imagery, our method allows for rapid and accurate post-disaster damage assessment and can be used for better coordination of medium- and long-term financial assistance programs for affected areas. In this paper, we present a strategy using machine learning for semantic segmentation of the flood map, which extracts the spatio-temporal information from the SAR images having both intensity as well coherence bands. The flood maps produced by the fusion of intensity and coherence are validated against state-of-the art methods for producing flood maps. 
The study of the valence and distribution of radiogenic Pb in monazite by using XPS and TEM
Authors: Tang Xu , Li Qiu-li , Gu Lin-xin
Published: March 2020

Monazite((Ce,Y,La,Th)PO4) is an important phosphate mineral and is one of the widely used minerals for U-Th-Pb dating in geochronology. In this study, we have examined the crystallinity, the valence and coordination of radiogenic Pb in a natural RW-1 monazite standard (ThO2 up to13.5 wt% and Pb up to ~5000 ppm) with a 207Pb/235U age of 904.15 ± 0.26 Ma from a Norwegian pegmatite by using laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy (TEM). The Raman spectrum analysis revealed that this monazite is well crystalline and is not damaged by α-particles. The results of XPS and TEM suggest that the radiogenic Pb produced by the α-decay of U and Th is divalent and radiogenic Pb atom substitutes the Ce-site within the monazite crystal lattice. The qualitative analyses conducted on the HAADF-STEM data reveal heterogeneous distribution of radiogenic Pb within the monazite crystal lattice. This is the first work on the determination of the oxidation state, the atomic location and distribution of radiogenic Pb in a natural monazite (CePO4). The deeply study of radiogenic Pb in monazite at the nanoscale and atomic scale provides a good insight for us to understand the mechanisms of nano-isotopic mobility and the nano-geochronology  that has been poorly understood so far.
The effects of solar activity on the Global Atmospheric Electrical Circuit
Authors: Khansari Marzieh , Tanskanen Eija , Nikbakhsh Shabnam
Published: March 2020

The global electric circuit (GEC) links the electric field and current flowing in the lower atmosphere, ionosphere and magnetosphere forming a giant spherical condenser, which is charged by the thunderstorms to a potential of several hundred thousand volts (Roble and Tzur, 1986) and drives vertical current through the atmosphere’s columnar resistance. Monitoring and researching the global electric circuit (GEC) are crucially important due to its links with climate change. Those two phenomena are connected by lightning activity, which itself is a measure of the GEC. It is known that space weather affects the Earth’s lightning activity, therefore the GEC might prove to be a critical tool in examining changing climate in terms of solar and lightning activity.

The possible relation between solar activity and lightning activity has been studied for a long period of time. The relation between sunspot number and lightning activity has been investigated, although the results still remain inconclusive across regions and time. At some regions a positive correlation is found, at others a negative one. Thus, it is important to explore other solar-geomagnetic variables possibly influencing lightning activity, such as geomagnetic index or fast solar wind streams, which were found to correlate well with lightning activity (Scott et al, 2014). Another increasingly important question is whether or not aerosols will contribute significantly to the Earth’s radiation budget, whether it be cooling or warming the climate. In a warming climate aerosol loading could alter and increase lightning activity, which in turn can lead to a positive feedback due to generation of NOx and thus O3 in the troposphere, a potent greenhouse gas.

In this project we will look at the connection between solar activity, aerosol loading, and thunderstorm activity in different types of regions such as coastal, boreal forest and urban area first in Finland and later on globally.

 

Aniol, R., 1952. Schwankungen der Gewitterha
A study of the effects of hail, snow and PM on Potential Gradient
Authors: Kourtidis Konstantinos , Karagioras Athanassios , Papadopoulou Eleni , Mihalopoulos Nikos , Stavroulas Iasonas
Published: March 2020

We present here the study of six hail events and five snow events in Xanthi, N. Greece, on Potential Gradient (PG). All hail events occurred in the spring-summer season of the years 2011-2018. A decrease in PG has been observed which has been around 2000-3000 V/m during the three hail events which occurred concurrently with rain. In three events with no rain, the decrease has been varying between 60 and 6000 V/m. In the case of only 60 V/m drop, no concurrent drop in temperature has been observed, while for the other cases it appears that for each degree drop in temperature the drop in PG is 1000 V/m, hence it appears that the intensity of the hail event regulates the drop in PG, although we do not have hail amount measurements to validate this. Regarding snow events,  the situation is more complicated, with PG fluctuating rapidly between high positive and high negative values. We present also a preliminary study of the impact of PM1.0 and PM2.5 on PG from measurements performed during 2019. We acknowledge support of this work by the project “PANhellenic infrastructure for Atmospheric Composition and climatE change” (MIS 5021516) which is implemented under the Action “Reinforcement of the Research and Innovation Infrastructure”, funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).
Soil organic carbon stocks in tropical soil systems under rainforests controlled by geochemistry
Authors: Reichenbach Mario , Fiener Peter , Wilken Florian , Six Johan , Kidinda Laurent , Mujinya Basile , Dötterl Sebastian
Published: March 2020

Soil mineralogy plays an important role in stabilizing soil organic carbon (SOC) against decomposition by forming organo-mineral complexes with reactive mineral surfaces. However, few studies take the influence of parent material geochemistry on the development of C stabilization mechanisms into account. In addition, studies evaluating C stabilization in soil are often limited to temperate climate zones with young to intermediate aged soils. This is not representative for older, deeply weathered and leached tropical systems and limits our understanding of the relationship between geology, soil formation and their effect on C stabilization.

Here, we study the relationship between soil carbon stabilization and the geochemical properties of soils developed on different parent material along geomorphic transects in pristine tropical forest systems under comparable climate. Our study is located in the eastern part of the Congo basin along the East African Rift Mountain System where we sampled 36 one meter soil cores along nine geomorphic transects on geologies ranging from mafic to felsic geochemistry.

Carbon stocks ranged between 2.67 tC ha-1 to 85.75 tC ha-1 and were on average composed of 4.5% (±5.3% SD) coarse particulate organic matter, 46.0% (±10.3% SD) (micro)aggregates associated C and 49.6% (±11.2% SD) free silt and clay associated C. Our analysis shows that the topographic position of the investigated soils had no effect on SOC stocks and the distribution of soil C fractions. Regression models and partial correlation analysis reveal that strong correlations of SOC stocks exists to geochemical properties of the solid phase of soil but not to the distribution of soil C fractions. SOC decreased strongly with soil depth on soils developed on felsic parent material, but less so on mafic or intermediate parent material. In addition, mafic geochemistry shows significantly higher SOC stocks compared to their felsic counterparts.

We conclude that despite long-lasting weathering, the contrasting geochemistry of the underlying parent material leaves a footprint in soil geochemistry that affects C stocks but less so on stabilization mechanisms. We hypothesis that carbon dynamics in these undisturbed tropical forest systems are more driven by C input and nutrient recycling than by variation in C stabilization potential.  
To slide or not to slide: explicit integration of landslides and sediment dynamics in a landscape evolution model
Authors: Campforts Benjamin , Shobe Charles M. , Steer Philippe , Lague Dimitri , Vanmaercke Matthias , Braun Jean
Published: March 2020

Landslides are key agents of sediment production and transport. Ongoing efforts to map and simulate landslides continuously improve our knowledge of landslide mechanisms. However, understanding sediment dynamics following landslide events is equally crucial for developing hazard mitigation strategies. An outstanding research challenge is to better constrain the dynamic feedbacks between landslides and fluvial processes.  Fluvial processes simultaneously (i) act as conveyor belts evacuating landslide-derived sediment and (ii) lower the hillslope’s base level triggering further landsliding. Landslides in turn can choke river channels with sediment, thereby critically altering fluvial responses to external tectonic or climatic perturbations.

Here, we present HYLANDS, a hybrid landscape evolution model, which is designed to numerically simulate both landslide activity and sediment dynamics following mass failure. The hybrid nature of the model is in its capacity to simulate both erosion and deposition at any place in the landscape. This is achieved by coupling the existing SPACE (Stream Power with Alluvium Conservation and Entrainment) model for channel incision with a new module simulating rapid, stochastic mass wasting (landsliding). 

In this contribution, we first illustrate the functionality of HYLANDS to capture river dynamics ranging from detachment-limited to transport-limited configurations. Subsequently, we apply the model to a portion of the Namche-Barwa massive in Eastern Tibet and compare simulated and observed landslide magnitude-frequency and area-volume scaling relationships. Finally, we illustrate the relevance of explicitly simulating stochastic landsliding and sediment dynamics over longer timescales on landscape evolution in general and river dynamics in particular under varying climatologic and tectonic configurations.

With HYLANDS we provide a hybrid tool to understand both the long and short-term coupling between stochastic hillslope processes, river incision and source-to-sink sediment dynamics. We further highlight its unique potential of bridging those timescales to generate better assessments of both on-site and downstream landslide risks.
Modelling future glacier evolution: Which feedbacks are relevant?
Authors: Huss Matthias , Mattea Enrico , Linsbauer Andreas , Hoelzle Martin
Published: March 2020

Numerous models to project the future evolution of mountain glaciers in response to ongoing climate change are available, both at the local and the global scale. However, a suite of partly major simplifications is necessary in these models given the restrictions in data availability. Whereas most models account for the primary feedbacks, such as the snow-ice albedo feedback and the dynamic glacier response in some way, a considerable number of yet poorly understood or less investigated feedbacks is present that might significantly hamper the reliability of current glaciological projections.

 

Here, we present results of a detailed modelling study for the example of Vadret da Morteratsch, Swiss Alps. A surface mass balance model accounting for ice dynamics is forced with downscaled regional climate model output (68 scenarios, CH2018) for the period 2015 to 2100. Various processes are either parameterized or explicitly accounted for. We focus on the use of a fully distributed surface energy-balance approach in comparison to simplified degree-day methods. The relevance of projected changes in different components of the energy balance is assessed using model experiments. In particular, the importance of feedback effects due to (1) the spatio-temporal evolution of supraglacial debris, (2) the formation of new proglacial lakes, and (3) changes in bare-ice albedo and local direct solar irradiance is investigated.

 

We find that the above feedback effects all have a rather small potential to substantially impact on the rates of expected glacier retreat. In some cases, this is unexpected (e.g. for debris coverage and proglacial lakes) but can be explained by compensating processes. We also discuss and visualize the future wastage of Vadret da Morteratsch under the newest generation of climate scenarios, and put these results into context with previous studies, as well as with plans to artificially reduce the rate of glacier mass loss.
Atmospheric Carbon Dioxide and Methane measurements at Sodankylä, Finland
Authors: Kivi Rigel , Chen Huilin , Hatakka Juha , Heikkinen Pauli , Laurila Tuomas , Lindqvist Hannakaisa
Published: March 2020

Carbon dioxide and methane column measurement at the Finnish Meteorological Institute’s Sodankylä facility in northern Finland started in early 2009. The measurements have been taken by a Fourier Transform Spectrometer (FTS) in the near-infrared spectral region. From the spectra column-averaged abundances of CO2, CH4 and other gases are derived. The instrument participates in the Total Carbon Column Observing Network (TCCON).  Here we present long-term ground based FTS measurements of carbon dioxide and methane and comparisons with satellite borne observations. We find that CO2 column amounts have increased by 2.2 ± 0.1 ppm/year since the start of the measurements in 2009 and CH4 column amounts have increased by 7 ± 0.4 ppb/year. The measurements are in good agreement with multi-year measurements by the Greenhouse Gases Observing Satellite (GOSAT): the relative difference in XCH4 has been -0.07 ± 0.02 % and the relative difference in XCO2 has been 0.04 ± 0.02 %. Finally we use balloon borne AirCore observations at the Sodankylä site to provide comparisons between FTS and in situ observations during all seasons.
Effects of sub-daily internal and external canopy water fluctuations on radar backscatter
Authors: Vermunt Paul , Steele-Dunne Susan , Khabbazan Saeed , Judge Jasmeet , Guerriero Leila
Published: March 2020

Radar observations of vegetated surfaces are highly affected by water in the soil and canopy. Consequently, radar has been used to monitor surface soil moisture for decades now. In addition, radar has been proven a useful tool for monitoring agricultural crop growth and development and forest fuel load estimation, as a result of the sensitivity of backscatter to vegetation water content (VWC). These current applications are based on satellite revisit periods of days to weeks. However, with future satellite constellations and geosynchronous radar missions, such as ESA’s Earth Explorer candidate mission HydroTerra, we will be able to monitor soil and vegetation multiple times per day. This opens up opportunities for new applications.

Examples could be (1) early detection of water stress in vegetation through anomalies in daily cycles of VWC, and (2) spatio-temporal estimations of rainfall interception, an important part of the water balance. However, currently, we lack the knowledge to physically understand sub-daily patterns in backscatter. Hence, the aim of our research is to understand the effect of water-related factors on sub-daily patterns of radar backscatter of a growing corn canopy.

Two intensive field campaigns were conducted in Florida (2018) and The Netherlands (2019). During both campaigns, soil moisture, external canopy water (dew, interception), soil water potential, and weather conditions were monitored every 15 minutes for the entire growing season. In addition, regular destructive sampling was performed to measure seasonal and sub-daily variations of vegetation water content. In Florida, hourly field scans were made with a truck-mounted polarimetric L-band scatterometer. In The Netherlands, these measurements were extended with X- and C-band frequencies.

Here, results will be presented from both campaigns. Different periods in the growing season will be highlighted. In particular, we will elaborate on the effects of variations in internal and external canopy water, and soil moisture on diurnal backscatter patterns.
Applicability of MODIS lake surface temperature depends on season and lake size on the Tibetan Plateau
Authors: La Zhu , Yang Kun , Qin Jun , Hou Juzhi , Lei Yanbin , Wang Junbo , Huang Anning , Chen Yingying , Ding Baohong , Li Xin
Published: March 2020

Lake surface temperature is a key parameter in understanding the variability of lake thermal condition and evaporation. MODIS-derived LST is widely used as a reference for lake-model validations and process studies in data-scarce regions. In this study, the accuracy and limitation of MODIS LST were examined on the Tibetan Plateau, where there are thousands of lakes. It is found that agreement between MODIS LST and in-situ subsurface (~1 m depth) temperature collected at six large lakes depends on the thermal phases. During lake turnover period (nighttime or from October to freeze-up date), the sink of surface water causes mixed with subsurface water. The MODIS LST was consistent with the in-situ data, indicating its high accuracy. During stratification period (from May to September), the lakes were thermally stratified due to intense solar heating and high salinity in some lakes; the daytime MODIS LST is systematically higher than the in-situ subsurface temperature, indicating it is credible. However, the MODIS LST has two limitations in this region. First, nighttime retrievals during monsoon season have considerable cold biases in monsoon-controlled region. This can be associated with shallow clouds or fog near the lake surface that occur frequently at night but are not well detected by MODIS. Second, the retrievals for narrow and small lakes have warm (cold) biases in the daytime (at night), perhaps due to proximity effect of mountains and land. The two situations are common across the Tibetan Plateau and thus severely restrict the applications of MODIS LST in lake studies.
Explosive mud volcano eruptions and rafting of mud breccia blocks
Authors: Mazzini Adriano , Akhmanov Grigorii , Michael Manga , Sciarra Alessandra , Khasayeva Ayten , Guliyev Ibrahim
Published: March 2020

Azerbaijan hosts the highest concentration of mud volcanoes (MVs) on Earth with structures that may reach several kilometres in diameter and the height up to 600 m. Many of these structures alternate between periods of dormancy with vigorous eruptions. The frequency of the eruptive activity varies between MVs, and is typically related to the time required to build sufficient overpressure able to drive the extrusion of fluids and mud breccia at the surface.

Lokbatan is possibly the most active MV on Earth exhibiting powerful eruptions occurring every 3-5 years. These phenomena manifest with spectacular gas flares that reach several tens of meters in height and the bursting of thousands of m3 of mud breccia resulting in spectacular mud flows that extend for more than 1.5 kilometres. Unlike other active MVs, Lokbatan does not show any visual evidence of diffuse degassing (e.g. active pools of gryphons) in the crater zone. Gas flux measurements completed with closed-chamber technique sensitive to ppmv, reveal extremely low values throughout the structure around the crater with average CH4=0.13 g/m2day and CO2=4.53 g/m2day. We suggest that after eruptive events, the mud breccia is able to seal the structure preventing the gas release and therefore promoting the overpressure build-up in the subsurface. This self-sealing mechanism allows a fast recharge of the MV resulting in more frequent and powerful eruptions. These spectacular phenomena are able to release in short time intervals massive amounts of gas, erupted mud breccia and energy due to the sudden overpressure release. Our field observations reveal the presence of large (up to ~50,000 m3) stratified blocks that were originally part of a large crater cone. These blocks were rafted > 1 km from the vent on top of mud breccia flows. We use a lubrication theory model to show that it is reasonable to transport blocks this large and this far provided the underlying mud flow was thick enough. The presence of large rafted blocks is not a unique phenomena observed at Lokbatan MV and is documented also at other large-scale structures.
Bench-scale studies of a permeable reactive barrier system for radiocesium removal
Authors: Cevikbilen Gokhan , Camtakan Zeyneb
Published: March 2020

Permeable reactive barrier (PRB) technology is being introduced as an alternative method for controlling and treating the groundwater, contaminated with heavy metals, chlorinated organics and radionuclides, etc. To regulate the cost of PRB technology to minimum in line with regulatory decontamination requirements for the contaminants, reactive media should be readily available at a low level of moderate cost. The proposed media included Zeolite (Clinoptilolite) and Sepiolite both as natural raw materials. In this work, we propose to investigate an alternative permeable barrier system for controlling and preventing the migration of radio cesium into the groundwater. It is understood that the falling head type vertical permeability tests performed on the reconstituted raw materials in a special odeometer test device under several vertical pressures might be inadequate to model the natural horizontal flow without mechanical assistance through the barrier in the aquifer. The bench- scale PRB demonstration system were also designed to investigate the horizontal 2D flow of groundwater by supplying a constant difference in between total heads of upstream and downstream. The hydraulic conductivity of the saturated media was studied by a flow net analysis. The effect of the simulated continuous release of contaminant solution in the upstream was observed in the soil media not only at the downstream both also in the upstream and PRBs. Remediation process over time can lead to changes in the hydraulic conductivity of a PRB. The bench-scale PRB system will be used to approximate the operating conditions for the information on the transport behavior of the radio cesium andchange in the hydraulic conductivity in PRB system.