bluuebunny/crossref_metadata_2025 huggingface dataset:
The importance of atmospheric acidity for nutrient deposition on global scale
Authors: Kanakidou Maria , Myriokefalitakis Stelios , Nenes Athanasios , Daskalakis Nikos
Published: March 2020

Atmospheric deposition can be an important source of nutrients and trace elements for land and ocean ecosystems. Atmospheric acidity is an important driver of the solubility of nutrients and trace elements present in atmospheric aerosols. Using a global 3-dimensional chemical transport model, we summarize here human driven past and future changes in the aerosol acidity and the resulting changes in the nitrogen, phosphorus and iron atmospheric deposition and solubility. We present and discuss the acidity driven changes in the chemical speciation and geographic patterns of nutrient deposition. Areas of uncertainties and implications for ecosystems functioning are discussed.

This work has been supported 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) and by the University of Bremen Excellence Chair of MK.
High-resolution fully-coupled atmospheric–hydrological modeling: a cross-compartment regional water and energy cycle evaluation
Authors: Fersch Benjamin , Senatore Alfonso , Adler Bianca , Arnault Joël , Mauder Matthias , Schneider Katrin , Völksch Ingo , Kunstmann Harald
Published: March 2020

The land surface and the atmospheric boundary layer are closely intertwined with respect to the exchange of water, trace gases and energy. Nonlinear feedback and scale dependent mechanisms are obvious by observations and theories. Modeling instead is often narrowed to single compartments of the terrestrial system or bound to traditional viewpoints of definite scientific disciplines. Coupled terrestrial hydrometeorological modeling systems attempt to overcome these limitations to achieve a better integration of the processes relevant for regional climate studies and local area weather prediction. We examine the ability of the hydrologically enhanced version of the Weather Research and Forecasting Model (WRF-Hydro) to reproduce the regional water cycle by means of a two-way coupled approach and assess the impact of hydrological coupling with respect to a traditional regional atmospheric model setting. It includes the observation-based calibration of the hydrological model component (offline WRF-Hydro) and a comparison of the classic WRF and the fully coupled WRF-Hydro models both with identical calibrated parameter settings for the land surface model (Noah-MP). The simulations are evaluated based on extensive observations at the pre-Alpine Terrestrial Environmental Observatory (TERENO Pre-Alpine) for the Ammer (600 km²) and Rott (55 km²) river catchments in southern Germany, covering a five month period (Jun–Oct 2016).

The sensitivity of 7 land surface parameters is tested using the Latin-Hypercube One-factor-At-a-Time (LH-OAT) method and 6 sensitive parameters are subsequently optimized for 6 different subcatchments, using the Model-Independent Parameter Estimation and Uncertainty Analysis software (PEST).

The calibration of the offline WRF-Hydro leads to Nash-Sutcliffe efficiencies between 0.56 and 0.64 and volumetric efficiencies between 0.46 and 0.81 for the six subcatchments. The comparison of classic WRF and fully coupled WRF-Hydro shows only tiny alterations for radiation and precipitation but considerable changes for moisture- and energy fluxes. By comparison with TERENO Pre-Alpine observations, the fully coupled model slightly outperforms the classic WRF with respect to evapotranspiration, sensible and ground heat flux, near surface mixing ratio, temperature, and boundary layer profiles of air temperature. The subcatchment-based water budgets show uniformly directed variations for evapotranspiration, infiltration excess and percolation whereas soil moisture and precipitation change randomly.
Numerical experiments with a parameterization of mires in the COSMO-D2 convection permitting limited-area numerical weather prediction framework
Authors: Helmert Jürgen , Yurova Alla , Blinov Denis , Rozinkina Inna , Baldauf Michael , Schättler Ulrich , Bettems Jean-Marie , Mironov Dmitrii
Published: March 2020

Europe - especially the northern and middle latitudes - is one of Earth’s mire-rich regions. Among the main distribution areas for mires in Central Europe the coastal region along the southeastern corner of the North Sea (Frisia) shows the highest density of mires. Despite of the important role of mires acting as a carbon sink and modifying the Bowen ratio with influence on screen level meteorological parameters their adequate representation in land-surface schemes used in numerical weather prediction and climate models is still insufficient.

With the recent version 5.06 the COSMO model (Baldauf et al., 2017) offers a parameterization of mires based on Yurova et al. (2014). In this approach the heat diffusion in the vertical domain of the soil multilayer model TERRA is considered with modified equations describing the thermal conductivity for peat with given water/ice contents. The mire hydrology is parameterized by the solution of the Richard's equation in the vertical domain extended by the formulation of a lower boundary condition as a climatological layer of permanent saturation used to simulate the water table position, in conjunction with a mire‐specific evapotranspiration and runoff parameterization.

The impact of the mire parameterization on screen level meteorological parameters and mesoscale processes was investigated in two numerical experiments with COSMO-D2 in a convection permitting limited-area numerical weather prediction (NWP) framework for summer 2018 and winter 2018/2019.

We will present results from the objective verification system and discuss the impact of geospatial physiographic data for an improved representation of mires in the NWP framework.
Analysis of the space-based surface temperature distribution in Badain Jaran Desert
Authors: Lopez Teodolina , Hu Haijun , Cui Yujun , Antoine Raphaël , An Ni
Published: March 2020

The 49,000-km2 Badain Jaran Desert lies in the centre of Alxa Plateau in the western Inner Mongolian Region [1;2]. The southern part of this desert is characterised by the unique association of lakes with the tallest megadunes of Earth (general height varying between 150 and 350 m). The mean precipitation rate of this region is below 100 mm yr-1 and the evapotranspiration one is ~2600 mm yr-1. Around 140 lakes have been reported, mainly located in the interdunal region and they represent a mean surface of ~23 km2. In order to protect the water resource of this desert, scientific research such as the sources of groundwater and groundwater recharge has been carried out. One of the most interesting resulting hypotheses is the existence of a convective circulation of the groundwater [3;4;1;5]. Indeed, the ascending current of groundwater can 1) supply the lakes and 2) may play role in the cementation of the megadunes, process that is considered as the starting point for their development. Interestingly, at the surface of the megadunes, a dry layer is present and its depth varies between 20 and 50 cm. But below this dry layer, the sand is moistened [6].

Space-based thermal images from MODIS of this region display at first approximation a correlation between the topography and the surface temperature evolution. In order to understand the relationship between the surface temperature, topography and soil moisture, a fully coupled hydro-thermal method was adopted to simulate the interaction between the atmosphere and the first metre below the surface. The analysis process includes the determination of material parameters, initial and boundary conditions, the calculations of net solar radiation, actual evaporation and sensible heat. Our methodology relies on the measured temperature distribution by MODIS and the calculation shows the temperature evolution along with the elevation. The factors including sunshine direction (i.e. sunny or shadowed slope) and evaporation on the surface temperature distribution at Badain Jaran will be discussed.

[1] Dong et al. (2004), Geomorphology, doi: 10.1016/j.geomorph.2003.07.023; [2] Dong et al. (2009), Geomorphology, doi: 10.1016/j.geomorph.2008.10.015; [3] Chen et al. (2004), Nature, doi: 10.1038/432459a; [4] Chen et al. (2012), Geochemistry International, doi: 10.1134/s0016702912030044 ; [5] Gates et al. (2008), Applied Geochemistry, doi: 10.1016/j.apgeochem.2008.07.019; [6]  Chen et al. (2006), Chinese Science Bulletin, doi; 10.1007/s11434-006-2196-8
Causal Discovery as a novel approach for CMIP6 climate model evaluation
Authors: Debeire Kevin , Eyring Veronika , Nowack Peer , Runge Jakob
Published: March 2020

Causal discovery algorithms are machine learning methods that estimate the dependencies between different variables. One of these algorithms, the recently developed PCMCI algorithm (Runge et al., 2019) estimates the time-lagged causal dependency structures from multiple time series and is adapted to common properties of Earth System time series data. The PCMCI algorithm has already been successfully applied in climate science to reveal known interaction pathways between Earth regions commonly referred to as teleconnections, and to explore new teleconnections (Kretschmer et al., 2017). One recent study used this method to evaluate models participating in the Coupled Model Intercomparison Project Phase 5  (CMIP5) (Nowack et al., 2019).

Here, we build on the Nowack et al. study and use PCMCI on dimension-reduced meteorological reanalysis data and the CMIP6 ensembles data. The resulting causal networks represent teleconnections (causal links) in each of the CMIP6 climate models. The models’ performance in representing realistic teleconnections is then assessed by comparing the causal networks of the individual CMIP6 models to the one obtained from meteorological reanalysis. We show that causal discovery is a promising and novel approach that complements existing model evaluation approaches.

 

References:

Runge, J., P. Nowack, M. Kretschmer, S. Flaxman, D. Sejdinovic, Detecting and quantifying causal associations in large nonlinear time series datasets. Sci. Adv. 5, eaau4996, 2019.

Kretschmer, M., J. Runge, and D. Coumou, Early prediction of extreme stratospheric polar vortex states based on causal precursors, Geophysical Research Letters, doi:10.1002/2017GL074696, 2017.

Nowack, P. J., J. Runge, V. Eyring, and J. D. Haigh, Causal networks for climate model evaluation and constrained projections, in review, 2019.
Biophysical effects of LULCC in a changing climate
Authors: Duveiller Gregory , Cescatti Alessandro
Published: March 2020

The properties of the type of surface covering the land have a direct effect on their surrounding atmosphere due to biophysical mechanisms. When the land cover type is altered, or when its properties change due to land use management, there can be a repercussion on the climate that goes beyond the associated changes in greenhouse gases. Satellite remote sensing observations have recently been instrumental to quantify and map these biophysical effects across geographical and seasonal gradients. The typical variable that is measured is temperature, as it integrates the combined effects of changes in surface albedo, soil moisture and vegetation state. Up-to-now, studies have generally focused on analyzing the mean response of land use and land cover change (LULCC) assuming a static climate. Here we revisit a proven methodology to infer the potential effects of LULCC on temperature based on a local space-for-time substitution, but we apply it annually across the globe for 15 consecutive years covering changing climate conditions. This opens the possibility to explore the inter-annual variability of the biophysical effects of LULCC, along with changes across climatic gradients. At specific look on extreme events enables us to assess how these dampen or amplify the biophysical effects of different LULCC transitions. Overall, this study establishes a first step towards inferring an observation-driven diagnostic that can provide guidance towards land-based mitigation strategies for a future and changing climate.
Future changes of circulation types associated with extremes over Sweden
Authors: Hansen Felicitas , Belusic Danijel , Wyser Klaus
Published: March 2020

The large-scale atmospheric circulation is one of the most important factors influencing weather and climate conditions on different timescales. Its short- and long-term changes considerably determine both mean and extreme values of surface parameters like temperature or precipitation rates. Future changes of circulation patterns are of particular interest as these may significantly alter or amplify the expected thermodynamic changes due to changing concentrations of greenhouse gases, albedo and land use. We analyse both historical as well as future climate simulations of the SMHI large ensemble (S-LENS) performed with the EC-Earth3 global climate model to examine large-scale circulation situations and their association to extremes in precipitation and temperature over Sweden. Various methods exist to classify mostly sea level pressure or geopotential height fields into characteristic circulation types, and we compare several of these methods for their applicability to represent precipitation and temperature variability over our region of interest. S-LENS consists of a 50-member ensemble for a historical period (1970-2014) and four 50-member climate change scenario ensembles covering the 21st century differing in terms of assumptions made for future radiative forcing development. We study the efficiency of circulation types in the historical period to give rise to extremes, and examine further the frequency and within-type changes of those circulation types associated with extremes by the middle and the end of the 21st century under the different climate change scenarios. S-LENS with its comparatively large number of both multi-decadal scenarios and realizations for each scenario serves as a perfect testbed to study potential changes in events of low frequency within the environment of a single model.
Controlling Effect of Wave Models and Plasma Boundaries on the Dynamic Evolution of Relativistic Radiation Belt Electrons
Authors: Wang Dedong , Shprits Yuri , Zhelavskaya Irina , Drozdov Alexander , Aseev Nikita , Effenberger Frederic , Castillo Angelica , Cervantes Sebastian
Published: March 2020

Modeling and observations have shown that energy diffusion by chorus waves is an important source of acceleration of electrons to relativistic energies. By performing long‐term simulations using the three‐dimensional Versatile Electron Radiation Belt (VERB-3D) code, we test how the latitudinal dependence of chorus waves can affect the dynamics of the radiation belt electrons. Results show that the variability of chorus waves at high latitudes is critical for modeling of megaelectron volt (MeV) electrons. We show that, depending on the latitudinal distribution of chorus waves under different geomagnetic conditions, they cannot only produce a net acceleration but also a net loss of MeV electrons. Decrease in high‐latitude chorus waves can tip the balance between acceleration and loss toward acceleration, or alternatively, the increase in high‐latitude waves can result in a net loss of MeV electrons. Variations in high‐latitude chorus may account for some of the variability of MeV electrons.

Our simulation results also show that the position of the plasmapause plays a significant role in the dynamic evolution of relativistic electrons. The magnetopause shadowing effect is included by using last closed drift shell (LCDS), and it is shown to significantly contribute to the dropouts of relativistic electrons at high L*.
High Arctic Polynyas in a Changing Climate
Authors: Jackson Rebecca , Bang Kvorning Anna , Pearce Christof , Seidenkrantz Marit-Solveig , Ribeiro Sofia
Published: March 2020

Polynyas, areas of open water in the otherwise sea-ice dominated high Arctic, are vital oases for biological productivity, supporting a plethora of marine mammals and birds that in turn sustain indigenous communities. Polynyas are not, however, consistent features. Beyond the observational era, little to nothing is known about their past dynamics and equally, about their resilience to emerging changes in Arctic sea-ice conditions.

Recent paleoceanographic reconstructions of the North Water in northern Baffin Bay, the largest of the high Arctic polynyas, indicate that the polynya contracted in response to warm climatic intervals during the Holocene (e.g. Roman Warm Period). In contrast, the onset of stable North Water polynya formation acted to suppress northward incursion of warm Atlantic-sourced waters. This highlighted not only the sensitivity of polynyas to past climatic changes, but the role their formation plays in mediating water column dynamics and ocean circulation.

These new findings provided the rationale for the MSCA project ‘POLARC: High Arctic Polynyas in a Changing Climate’, to investigate the Holocene dynamics of other high Arctic polynyas forming off the east Greenland coast. New marine sedimentary archives and a multiproxy approach will be used to reconstruct productivity, sea-ice conditions and bottom water conditions, capturing a holistic view of these systems and their interaction with climatic and oceanographic variation during the Holocene (11,700 years BP to present). We present here preliminary paleoceanographic reconstructions of the Sirius Water, the first Holocene record from this polynya region, as well as plans for model-data comparisons in key polynya regions with the aim of constraining the past and better predicting the future of these phenomena.
Greenland’s supraglacial lakes increase by a quarter in the last 20 years
Authors: Lea James , Brough Stephen
Published: March 2020

Supraglacial lakes represent a fundamental component of the surface hydrology of the Greenland ice sheet. Understanding the relationship of these lakes with ice sheet surface mass balance, geometry, location, and how this has changed through time also informs how their drainage can impact ice sheet subglacial hydrology and seasonal flow dynamics. However, previous studies of supraglacial lakes have been limited in spatial and/or temporal scale relative to the entire ice sheet.

Here we use the entire MODIS Terra archive within Google Earth Engine to derive maps of supraglacial lake cover every day of every melt season for the last 20 years for the entire Greenland ice sheet. Through generating annual composites of where lakes are observed, we identify that the frequency of lakes has on average increased by 27% from 2000-2019. Lakes are observed to be occurring at higher elevations in all sectors of the ice sheet for 2010-2019 compared to 2000-2009. Output from the regional climate model MAR suggests that in the most recent decade higher numbers of lakes are being formed for a given volume of runoff.

The observation of lakes that can form more easily, further inland and at higher elevations have significant implications for future surface mass balance, and potentially the dynamics of inland regions of the Greenland ice sheet.
Constructing gridded hourly air temperature dataset
Authors: Dumitrescu Alexandru , Cheval Sorin
Published: March 2020

Air temperature is one of the most important meteorological element, with major impact on the earth-atmosphere energy balance. The characteristics of the surface air temperature in locations without surface meteorological measurements are usually acquired by employing spatial statistics methods. Gridded surface meteorological data are essential for evaluating the performance of climatological models, for applying statistical downscaling methods and as input data for hydrological and agrometeorological models.

In this work, we tested two categories of statistical methods (spatial and spatio-temporal) used for interpolating ground-based hourly air temperature data. The main input dataset used in this work was the quality controlled and homogenized hourly air temperatures measured between 2016 and 2017, obtained from four networks: Romanian National Meteorological Administration (ANM), National Network for Monitoring Air Quality (RNMCA), Regional Basic Synoptic Network (RBSN), and Meteorological Terminal Aviation Routine Weather Report network (METAR). 

The principal covariate used in the spatial interpolation procedures was the gap filled hourly LST data over Romania, available between 2016 to 2017, based on MSG-Seviri satellite images, which is an operational product of the Land Surface Analysis – Satellite Application Facility (LSA-SAF).  The other predictors were derived from SRTM (Shuttle Radar Topography Mission) data and from CORINE Land Cover 2018 product. The gridding was performed in a Romanian National Grid (Stereo 70), at 1000 m × 1000 m spatial resolution.

The results of the tested methods show that the mean absolute errors (MAE) and root mean square errors (RMSE) of space–time predictions are considerably lower than those of the pure spatial estimation.

This work was supported by a grant of Ministry of Research and Innovation, Romania, CNCS - UEFISCDI, project number PN-III-P1-1.1-PD-2016-1579, within PNCDI III.
Fine root production along a 40-year chronosequence of restored mangroves in Vietnam
Authors: Arnaud Marie , Morris Paul J. , Baird Andy J. , Dang Thuong Huyen , Nguyen Tai Tue
Published: March 2020

Mangroves are hotspots of carbon sequestration, providing ecosystem services worth US$194 000 per hectare per year. In response to widespread mangrove losses, reforestation projects have been promoted. Monitoring and assessment of those projects have mainly focused on aboveground carbon stocks, but most of the carbon is found underground (as soil carbon and roots) and little is known about belowground carbon dynamics in mangroves. In particular, it is unknown how fine root production develops during the period following reforestation. A better understanding of fine root production is important, since fine root production is a major driver of soil organic matter accumulation, which allows mangroves to occupy vertical accommodation space to withstand sea-level rise. Using minirhizotrons, we characterised the variation of fine root production along a chronosequence of mangroves in the Mekong Delta in Vietnam replanted in 1978, 1986 and 1991. We found that fine root production declines with: i) mangrove age, as a result of the self-thinning processes associated with mangrove ageing; and ii) soil depth, likely due to a vertical gradient in soil nutrient availability. Our findings have important implications for understanding belowground carbon dynamics, and highlight the need to account for mangrove age when forecasting mangrove carbon dynamics and resistance to sea-level rise.
High Andean Soil Landscapes Shaped by Interactions between Geomorphology, Vegetation, and Hydrology
Authors: Vanacker Veerle , Molina Armando , Zhiminaicela Santiago , Corre Marife , Veldkamp Edzo
Published: March 2020

Physical and chemical weathering processes fulfil a crucial function in the biogeochemistry of terrestrial ecosystems. Rock‐derived weathering products provide essential plant nutrients, and regulate the chemical composition of soil, surface, and groundwater. The rate and extent of chemical weathering are influenced by the combined effects of climate, parent material, topography, and vegetation, and ultimately determine the mineral composition and element ratios of soil material. Understanding the spatial variation of rock‐derived weathering products across heterogeneous landscapes not only relies on knowledge of the environmental controls but also of their interactions.

High Andean tropical ecosystems provide a good opportunity to study the association between chemical weathering, local topography and vegetation patterns: the climate, parent material and soil age can be held constant at the landscape scale, while the vegetation and slope morphology can vary greatly from the hilltops to the valley bottoms. In this study, we selected 10 soil toposequences on andesitic flows: 5 under tussock grasses, 3 under cushion forming plants and 2 under native forest. A marginally significant increase in base cation depletion is observed along topographic gradients that can be associated with physical transport of weathered soil particles downslope or subsurface water fluxes. Beyond the hillslope-scale topographic control on chemical weathering extent, we observed highly significant differences in chemical weathering extent between vegetation communities with total mass losses in forest soils being respectively 19% and 22% higher than in grasslands and cushion forming plants. Although biotic factors can play a role in creating the observed patterns in soil development, the vegetation communities can also hint to the existence of hillslope micro-topography and subsurface hydrological patterns that are challenging to map in the field.
Pitfalls on the path to success… what did we learn after introducing tablets for digital mapping and field tectonic analyses into Nice’s Geology Master program?
Authors: Duclaux Guillaume , Petit Carole , Ratzov Gueorgui , Corsini Michel , Verati Chrystele , Scalabrino Bruno
Published: March 2020

Structural geologists love their compass and cherish their maps and field book more than anything, don’t they? And they are absolutely right to do so! Now, technical evolutions and the increasing availability and use by geology professionals of digital devices for structural and geological mapping means that our teaching curriculum also has to evolve and engage in these new ways of doing geology. Nevertheless, introducing tablets as field tools in the curriculum has not been so easy… If we had received one euro every time we heard that our students need to learn how to measure geological structures with a compass and maintain a proper field book rather than use a tablet for geological mapping we would be rich! We heard complaints from colleagues because students were getting too excited about using tablets… We argue that the issue with digital mapping and the use of tablets as field tools does not lie in the tools themselves, but in the overall methodology that is simply not properly mastered by the students, and that introducing exciting new tools helps overcoming the lack of interest of some and better engage them in the field in general.

The Earth Sciences Department at the Université Côte d’Azur purchased a pool of 15 iPad-mini units (3G models, as only those are equipped with GPS) protected in water-resistant and dust-proof cases. Students are given the tablet along with a battery pack, so they can charge their devices in remote locations and keep using them for mapping for at least three days. We have used a range of free apps for mapping, depending on the objectives of the field campaigns. For brittle deformation and fault slip data analysis students have access to Rick Allmendinger’s free app: FaultKin. We have been using for digital mapping in various terrains, the free Field Move app developed by Petroleum Experts Limited. Data acquired in the field (including georeferenced pictures, structural measurements, units contacts, and faults traces) have been seamlessly imported in GIS tools like Google Earth or QGIS, and been used for generating maps and field reports. We made mistakes assuming that some mapping techniques were already understood, and we are trying to improve our teaching content both in the field and in class to better prepare our students in using digital technology. Finally, we want to emphasize that the tablets are not replacing but complementing traditional mapping techniques. After a year using these tablets we have had a great engagement from our Master students and aim to introduce these tools progressively as part of the undergraduate curriculum, still insuring that correct observations are done in the field and detailed descriptions are properly entered on the tablets.
Big commercial microwave link data: Detecting rain events with deep learning
Authors: Polz Julius , Chwala Christian , Graf Maximilian , Kunstmann Harald
Published: March 2020

Commercial microwave links (CMLs) can be used for quantitative precipitation estimation. The measurement technique is based on the exploitation of the close to linear relationship between the attenuation of the signal level by rainfall and the path averaged rain rate. At a temporal resolution of one minute, the signal level of almost 4000 CMLs distributed all over Germany is being recorded since August 2017, resulting in one of the biggest CML data sets available for scientific purposes. A crucial step for retrieving rainfall information from this large CML data set is to accurately detect rainy periods in the time-series, a process which is hampered by strong signal fluctuations, occasionally occurring even when there is no rain. In our study, we evaluate the performance of convolutional neural networks (CNNs) to distinguish between rainy and non-rainy signal fluctuations by recognizing their specific patterns. CNNs make use of many layers and local connections of neurons to recognize patterns independent of their location in the time-series. We designed a custom CNN architecture consisting of a feature extraction and classification part with 20 layers of neurons and 1.4 x 105 trainable parameters. To train the model and validate the results we refer to the gauge-adjusted radar product RADOLAN-RW, provided by the German meteorological service. Despite not being an absolute truth, it provides robust information about rain events at the CML locations at an hourly time resolution. With only 400 CMLs used for training and 3504 for validation, we find that CNNs can learn to recognize different signal fluctuation patterns and generalize well to sensors and time periods not used for training. Overall we find a good agreement between the CML and weather radar derived rainfall information by detecting on average 87 % of all rainy and 91 % of all non-rainy periods.
Assessing Global Ocean and Continental Mass Change from 17 years of GRACE/-FO: the role of coastal buffer zones
Authors: Gutknecht Benjamin D. , Groh Andreas , Cáceres Denise , Horwath Martin
Published: March 2020

Following the ESA CCI Sea Level Budget Closure (SLBC) project's work of 2017–2019, we present updated time-series of

Global Ocean Mass Change (OMC) and

Continental Mass Change (CMC),

both including continuous measurements by GRACE-FO. By least-squares adjusting a multi-parameter fit to monthly resolved OMC, we estimate the linear trend of Global Ocean mass change over all presently available GRACE/-FO months since April 2002 to be 2.41 ± 0.22 mm/a, with an acceleration of 0.10 mm a-2 over the same period.

A systematic analysis of the computed ocean response ("monthly fingerprints") to on-shore mass changes by means of solving the sea level equation implies that the common method of re-scaling the 'inner' buffered ocean may lead to OMC overestimations up to 10 per cent. We present this effect as a function of coastal buffer width for a global and for a 'truncated' global ocean (Lat ≤ ±65°), since the latter case, as seen e.g. in conjunction with radar altimetry, can lead to more than five per cent overestimated OMC. Furthermore, the use of coastal buffers seems to induce phase bias in the annual oscillation, which may explain the observed phase shift in the monthly budget between GRACE OMC and the sum of contributing continental components (i.e. ice sheets, glaciers, land water storage).

As a supplementary product of the SLBC project, we present GRACE/-FO derived mass change series 2002-04/present for continents (excluding Greenland and Antarctica). Consistent integration of out-leaking signal over coastal buffer zones, and subtraction of GAD-corrected mean OMC therein, leads to agreement with independently-assessed joint land water and glacier mass change data, well within uncertainty bounds.
The contribution of fire to a global increase in forest loss
Authors: van Wees Dave , van der Werf Guido
Published: March 2020

Fire is one of the main drivers of forest loss worldwide and its role varies depending on natural and anthropogenic drivers, ranging from large boreal wildfires to smallholder shifting agriculture. The emergence of higher resolution satellite data creates new opportunities for studying the spatial and temporal relatedness of fires and forest loss. We have quantified this relatedness by overlapping global forest loss for 2001-2018 with fire detections from burned area and active fire satellite products at 500 m resolution. Previous studies have shown that global burned area is decreasing, mostly caused by increased human influence in savanna ecosystems. However, the opposite is true for forests: our study of trends and variability shows that forest loss has increased substantially over the last two decades in many parts of the world and that its dynamics are strongly linked to fire. Striking increases in forest loss were found for rapidly developing regions such as Africa and Southeast Asia, where commodity-driven deforestation and shifting agriculture have led to increased land clearing, often with the use of fire. Besides, stand-replacing wildfire activity has increased in boreal, temperate and tropical forests. The increase in fire activity in forests and decrease in savannas shows that the global balance is shifting because of both natural and anthropogenic factors, with important consequences for the future carbon cycle.
Embracing dynamic complexity in climate economics: The DSK Agent-based Integrated Assessment Modelling
Authors: Wieners Claudia , Lamperti Francesco , Roventini Andrea , Buizza Roberto
Published: March 2020

Integrated Assessment Models are a key tool to search and evaluate climate policies - i.e. a set of measures best suited to avoid the worst of climate change without “harming the economy” too much. 
Climate action µ(t) is typically portrayed as coming at a cost (relative to a no-policy case) C(µ), where C is a positive, monotonously increasing function. 
However, this representation ignores economic dynamics. For instance, it assumes that CO2 abatement costs today are independent from efforts done last year, whereas in reality, previous investments in infrastructure or knowledge will have effects on abatement and abatement costs in the future. More generally speaking, the economy is a complex system of interacting players, capable of path-dependent behaviour, multiple equilibria or out-of-equilibrium dynamics, and transitions between states, and climate policy measures (or climate impacts) targeting some actors can affect the whole system. 

Agent-based modelling has in recent years emerged as a tool to break the constraints imposed by generalised equilibrium models underlying most IAMs. Agent-based models directly simulate the activities of diverse interacting agents, rather than making assumptions of the aggregate behaviour of groups of agents. 

Here, we present an agent-based Integrating Assessment Model, the Dystopian Schumpter-Keynes (DSK) model. It contains an industrial sector with interacting machine and consumption good firms, a banking sector, a government, and an electricity supplier, coupled to a climate module. The model has been used, among other things, to investigate how different types of climate impacts propagate through the economy. In this presentation, we focus on climate policy. In particular, we investigate
1.  which policy tools, or combination of tools, are effective at bringing about a sufficiently rapid decarbonisation. Is a uniform carbon tax really sufficient to cause a green transition? 
2.  what will be the side effects on the economy. Will there be ongoing strain on the economy, or will costs be transitional - potentially even with long-term benefits? 
Garabashi glacier (Caucasus) mass changes estimated from glaciological and geodetic mass balance measurements
Authors: Kutuzov Stanislav , Smirnov Andrey , Nosenko Gennady , Lavrentiev Ivan , Poliukhov Aleksei , Elagina Nelly , Nikitin Stanislav
Published: March 2020

The ice-covered Europe's largest volcanic massif Elbrus (5,642 m) is a unique object for studying the reaction of mountain glaciers to climate changes. Elbrus glacial system contains more than 10% of the total ice volume in the Greater Caucasus. Elbrus glaciers influence on the recreation development. The rivers runoff from the Elbrus glaciers irrigates agricultural lands on steppe plains of the North Caucasus.

The rate of glacier reduction in the late XX - early XXI centuries has increased significantly and in 1997-2017 Elbrus have lost 23% of its volume. Despite a number of glacier studies the mechanisms and quantitative characteristics surface mass exchange on Elbrus are still uncertain. Mass balance calculations were based on limited data. In particular, amount and distribution of snow accumulation, mass balance sensitivity to meteorological parameters under dramatic climate changes and other parameters remained unknown.

Here we present the results of the detailed analysis of Garabashi glacier mass changes in 1982-2019 using glaciological and geodetic methods. Based on the new data of snow and ablation distribution the mass balance measurement system of Garabashi glacier was improved in 2018-2019. The mass balance over the studied period was also modelled using both temperature-index and distributed energy mass balance models calibrated by in situ measurements and albedo estimates from the remote sensing.

The mass balance of the Garabashi glacier was close to zero or slightly positive in 1982-1997 and the cumulative mass balance was 1 m w.e. in this period. In 1997-2017 Garabashi glacier lost 12.58 m w.e. and 12.92 ± 0.95 m w.e. (−0.63 and −0.65 ± 0.05 m w.e. a−1) estimated by glaciological and geodetic method, respectively. Additional -1.7 m w.e. were lost in 2018-2019. This resulted in an area reduction by 14% and a loss of 27% of glacier volume. The observed glacier recession is driven by the pronounced increase in summer temperatures, especially since 1995, which is accompanied by nearly consistent precipitation rates The increase in incoming shortwave radiation, also played a significant role in the accelerated mass loss of glaciers in Caucasus. This study was supported by the RFBR grant 18-05-00838 a
First steps towards deriving rock magnetic and paleomagnetic data from subsets of magnetic grains in lavas using Micromagnetic Tomography
Authors: de Groot Lennart , Fabian Karl , Béguin Annemarieke , Kosters Martha , Fu Roger , Harrison Richard , Barnhoorn Auke , van Leeuwen Tristan
Published: March 2020

Our understanding of the behavior of the geomagnetic field arises from magnetic signals stored in geological materials, e.g. lavas. Almost all experiments to determine the past state of the Earth’s magnetic field use bulk samples (typically 1 - 10 cc) and measure their magnetic moment after series of laboratory treatments. Lavas, however, consist of mixtures of different iron-oxide grains that vary in size, shape, and chemistry. Some of these grains are good recorders of the Earth’s magnetic field; others are not. Only a small amount of adverse behaved magnetic grains in a sample already hampers all classical experiments to obtain paleointensities; success rates as low as 10-20% are common, i.e. for 80-90% of all lavas vital information on paleointensities is lost before it can be uncovered.

Recently, we showed that it is possible to determine the magnetization of individual grains inside a synthetic sample using a new technique: Micromagnetic Tomography. The individual magnetizations of grains are determined by inverting scanning magnetometry data from the surface on the sample onto the known locations, sizes and shapes of the magnetic grains that are obtained from a microCT scan of the sample. The synthetic sample used for our proof-of-concept, however, was optimized for success: the dispersion of magnetic markers was low, and the magnetite grains had a well-defined grain size range. Furthermore, the scanning SQUID microscope used requires the sample to be at 4 K, below the Verweij transition of the magnetite grains.

Here we present the first Micromagnetic Tomography results from natural samples. We used two magnetic scanning techniques that operate at room temperature, a Magnetic Tunneling Junction set-up and a Quantum Diamond Magnetometer, to acquire the magnetic surface scans from a Hawaiian lava and calculated magnetic moments of individual grains present. We show that it is possible to acquire rock magnetic information as function of grain size from these natural samples and reveal the first results of interpreting a paleomagnetic direction from selected subsets of grains in our samples. These are the first steps towards deriving rock magnetic and paleomagnetic information from subsets of known good recorders inside lava samples, a technique that will revolutionize our field of research.
Debris flow interaction with structures: challenges to traditional load models
Authors: Leonardi Alessandro , Pasqua Andrea , Pirulli Marina
Published: March 2020

Debris flow barriers often feature one or more filter elements, i.e. narrow outlets that induce deposition of the coarsest sediments, while allowing water and fines to filter through. Slit dams and steel nets are examples of this type of barriers. The design of the filter elements must balance the need to trap boulders and to dissipate the flow energy, while keeping maintenance work as low as possible.

Filter barriers elude the traditional load model prescribed by guidelines. Under some conditions, the outlets can clog with large boulders. The time necessary for this to happen mainly depends on the relative size between boulder and outlet, and is a nonlinear function of the flow composition. In any case, the main clogging mechanism is the formation of granular arches. These can induce significant load also in directions different from the main direction of the incoming flow.

Unless the barrier is specifically designed to withstand this type of load, granular arches, but also prolonged flow through the outlet, can induce deterioration and loss of functionality of the structure. In this work, we estimate these effects employing a combination of discrete- and continuum-based numerical methods. We evaluate the performance of two types of debris-resisting barriers, comparing the results with laboratory measurements and with the outcome of a monitoring campaign on a real barrier located in the Italian alps.

 

 

References:

Leonardi, A., Goodwin, G. R., & Pirulli, M. (2019). The force exerted by granular flows on slit dams. Acta Geotechnica, 14(6), 1949–1963.

Leonardi, A., & Pirulli, M. (2020). Analysis of the load exerted by debris flows on filter barriers : Comparison between numerical results and field measurements. Computer & Geotechnics, 118, 103311.
Model resolution dependence of convection initiation by orographically-induced thermal circulations
Authors: Göbel Matthias , Serafin Stefano , Rotach Mathias
Published: March 2020

Thermally-driven circulations in mountainous terrain can play an essential role in the initiation of deep moist convection: They advect moisture at low levels and provide the necessary trigger mechanism to lift air parcels above the level of free convection.
Current limited-area numerical weather prediction models with a horizontal grid spacing of around 1 km may adequately resolve the larger-scale thermal circulations, namely, valley winds and plain-to-mountain winds, but not the small-scale slope winds. In addition, the planetary boundary-layer parametrizations typically employed in these models are based on the assumption of horizontally homogeneous and flat terrain and assume none of the turbulent boundary-layer eddies are explicitly resolved.
In this contribution, we investigate the problems that arise due to these deficiencies in the given context using idealized numerical simulations with the WRF model. We compare simulations at different horizontal resolutions in the turbulence gray zone with LES simulations. Previous idealized modeling studies have shown that simulations at kilometer-scale resolution may produce stronger moisture convergence due to thermally-driven circulations and thus earlier and more vigorous convection over the mountain ridges compared with an LES model.
We focus on strongly-inhibited initial conditions that lead to deep moist convection with a kilometer-scale but not with an LES model and investigate the reasons for the different convective behavior. The benefits of scale-adaptive boundary-layer schemes for the studied process are evaluated.
10 years of Polar Stratospheric Clouds lidar measurements at the French antarctic station Dumont d’Urville
Authors: Tencé Florent , Jumelet Julien , Sarkissian Alain , Bekki Slimane , Keckhut Philippe
Published: March 2020

Polar Stratospheric Clouds (PSCs) play a primary role in polar stratospheric ozone depletion processes. Aside from recent improvements in both spaceborne PSCs monitoring as well as investigations on PSCs microphysics and modeling, there are still uncertainties associated to solid particle formation and their denitrification potential. In that regard, groundbased instruments deliver detailed and valuable measurements that complement the global spaceborne coverage.

Operated since 1989 at the French antarctic station Dumont d’Urville (DDU) in the frame of the international Network for the Detection of Atmospheric Composition Change (NDACC), the Rayleigh/Mie/Raman lidar provides over the years a solid dataset to feed both process and classification studies, by monitoring cloud and aerosol occurrences in the upper troposphere and lower stratosphere. Located on antarctic shore (66°S - 140°E), the station has a privileged access to polar vortex dynamics. Measurements are weather-dependent with a yearly average of 130 nights of monitoring. Expected PSC formation temperatures are used to evaluate the whole PSC season occurrences.

We hereby present a consolidated dataset from 10 years of lidar measurements using the 532nm backscatter ratio, the aerosol depolarisation and local atmospheric conditions to help in building an aerosol/cloud classification. Using the different PSC classes and associated optical properties thresholds established in the recent PSC CALIOP classification, we build a picture of the 2007-2019 events, from march to october.

Overall, the DDU PSC pattern is very consistent with expected typical temperature controlled microphysical calculations. Outside of background sulfate aerosols and anomalies related to volcanic activity (like in 2015), Supercooled Ternary Solution (STS) particles are the most observed particle type, closely followed by Nitric Acid Trihydrate (NAT). ICE clouds are less but regularly observed. ICE clouds also have to be cleary separated from cirrus clouds, raising the issue of accurate dynamics tropopause calculations.

Validation of the spaceborne measurements as well as multiple signatures of volcanic or even biomass originated aerosol plumes strengthens the need for groundbased monitoring especially in polar regions where instrumental facilities remain sparse.