bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences in Nature Based Solutions perception and implementation strategies across academic disciplines, an empirical analysis
Authors: Vicarelli Marta , Nagabhatla Nidhi
Published: March 2021

This study investigates using a survey how disciplinary scholars perceive Nature Based Solutions (NBS) and how they differ in their NBS implementation approach at the local level. Respondents participated in the 2020-2021 , a ten-week course (online from Dec. 3, 2020, to Jan. 26, 2021) with a focus on Disaster Risk Reduction and Water Security. Supported by the United Nations Environmental Program and the Partnership for Environment and Disaster Risk Reduction (PEDRR), a global alliance of UN agencies, NGOs, and institutes, the Winter School Program is delivered via a partnership model between the University of Massachusetts Amherst's School of Public Policy and Department of Economics, McMaster University, and the United Nations University. Aiming to build young professionals' capacity on NBS framing and application potential, the Program focuses on the delivery of conceptual and empirical information on ecosystem-based climate adaptation and disaster risk reduction. The Program represents a knowledge hub and an opportunity to network with scholars, international experts, and practitioners. 40 graduate students from numerous disciplines (e.g. economics, public policy, international affairs, geosciences, engineering, chemistry and physics) have been selected to attend the Program and have participated in a survey to assess how disciplinary scholars perceive NBS and to explore differences in strategies and priorities while implementing NBS within communities. The results of the survey offer lessons about opportunities and possible challenges of interdisciplinary collaborations when implementing NBS.
The propagation dynamics and causes of hydrological drought in response to meteorological drought at seasonal timescale
Authors: Ma Lan , Huang Qiang , Huang Shengzhi , Liu Dengfeng , Leng Guoyong , Wang Lu , Li Pei
Published: March 2021

According to widely accepted definition of drought, meteorological and hydrological droughts originally develop from rainfalls and runoffs deficits, respectively. Runoffs deficit is mainly derived from rainfalls deficit. Therefore, hydrological drought is essentially propagated from meteorological drought, which is critical for agricultural water management. Investigation of the propagation from meteorological to hydrological drought is important for drought early warning, preparedness and mitigation. Nevertheless, the characteristics and dynamic of drought propagation in spatiotemporal scale remain unresolved. To this end, the characteristics and dynamic of drought propagation in different seasons and their linkages with key forcing factors are evaluated. In this study, the meteorological drought and hydrological drought are characterized by Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI), respectively. The propagation time is identified by the corresponding timescale of the maximum correlation coefficient between SPI and SRI. Then, a 20-year sliding window is adopted to explore the propagation dynamic in various seasons. Furthermore, the multiple linear regression model (MLR) is established to quantitatively explore the influence of meteorological factors, underlying surface features and teleconnection factors on the propagation time variations. The Wei River Basin (WRB), which is a typical Loess Plateau watershed in China, is selected as a case study. Results indicate that: (1) the propagation time from meteorological to hydrological drought is shorter in summer (2 months) and autumn (3 months), whilst that is longer in spring (8 months) and winter (13 months). Moreover, the propagation rates exhibit decreasing trend in warm seasons, which however show increasing trend in cold seasons; (2) a significant slowing propagation in autumn is mainly caused by the decreasing soil moisture and precipitation, while the non-significant tendency in summer is generally induced by the offset between insignificant increasing precipitation and significant decreasing soil moisture; (3) the replenishment from streamflow to groundwater in advance prompts the faster propagation from meteorological to hydrological drought in spring and winter; (4) teleconnection factors have strong influences on the propagation in autumn, in which Arctic Oscillation (AO), El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) mainly affect participation, arid index and soil moisture, thereby impacting drought propagation.
Beamforming Reliability of DAS Ambient Noise Data and Wave Modes Identification
Authors: Zhao Yumin , Li Yunyue Elita
Published: March 2021

Ambient noise generated by the anthropological activities in the urban environments may contain both Rayleigh and Love waves. Due to the differences in the physics of Rayleigh and Love waves, a pre-knowledge of the wave modes in the cross-correlogram is essential for an accurate inversion of the subsurface velocity model. Several studies (Martin and Biondi, 2017; Martin et al., 2017; Luo et al., 2020) demonstrated that only Rayleigh waves can be extracted by cross-correlation if the virtual source is colinear with the DAS array based on the assumption that the ambient noise sources are random and uniformly distributed. However, in realistic cases, ambient noise sources may come from a certain direction (e.g., Dou et al., 2017; Zhang et al., 2019). Moreover, the source propagation direction should be resolved and used to correct the apparent dispersion curves. Zhao et al. (2020) and van den Ende et al. (2020) proposed that beamforming results are not always reliable due to the measurements of DAS.

Based on the synthetic DAS ambient noise data recorded by a near “L” shape array (Source-West corner of the Stanford DAS-1 array), we prove that beamforming can resolve the source direction when the ambient sources are mainly coming from one direction. Two important processing procedures are that: check the polarity in the data and apply polarity flip on one part of the data; apply amplitude normalization on the data if strong amplitude difference exits in the data. Based on the source direction, the coordinate of the DAS array, and amplitude ratio of the data recorded by the two segments of the DAS array, we propose an inversion method to calculate the amplitude ratio of the Rayleigh and Love waves generated by the ambient sources.

We apply the method to two 100-second DAS ambient noise data recorded by the Stanford DAS-1 array. We first resolve the source propagation direction from the two data. The results indicate that the ambient noise in the data were mainly generated by the motor vehicles running on the Campus Drive in the northwest of the array. Then we invert for the Rayleigh and Love waves amplitude ratio using the proposed method. The ratios for the two data are 0.2 and 0.13, respectively. The results suggest that the ambient noise generated by motor vehicles running on the northwest corner of the Campus Drive mainly contain Love waves.
Modeling the regional dust emissions in central Europe and their contribution to urban PM levels
Authors: Liaskoni Marina , Bartik Lukas , Huszar Peter
Published: March 2021

Windblown dust, emitted from the surface of the earth to the atmosphere as a result of the disintegration of material due to wind drag, can have a significant impact on the atmospheric concentration of PM, especially over (semi-)arid areas. They however may be important occasionally also over non-arid regions with considerable precipitation (e.g. over midlatitudes). Therefore their contribution to the total PM pollution cannot be neglected, especially considering the increasing potential of droughts in a changing climate, when long dry periods occur between precipitation events.

Here, we investigate the regional impact of PM emissions from wind erosion on urban PM levels for a central European domain using a well-established windblown dust module (called ‘‘WBDUST’’) for the 2018-2019 period. As driving meteorological data, we used WRF simulations. Before applying WBDUST, we made some modifications which ensured that the surface heterogeneity for vegetation cover is taken into account. This is important as for grid cells, where the average leaf-area-index (LAI) is higher than a certain threshold, zero emissions would be produced. However, if we take into account the fractional character of LAI, emissions will be more realistic. The obtained emission fluxes were comparable to anthropogenic ones indicating the great importance of windblown dust even over such non-arid areas. WBDUST emissions were implemented into the CAMx chemistry transport model and we performed simulations with and without these emissions. Our results showed that urban PM levels are significantly higher if wind-blown dust is considered and match better with observations.
Modeling ELF waves in the non-uniform Earth-ionosphere cavity
Authors: Bozoki Tamas , Pracser Erno , Satori Gabriella , Kulak Andrzej , Mlynarczyk Janusz , Williams Earle
Published: March 2021

Below 100 Hz, in the lowest part of the extremely low frequency (ELF, 3 Hz - 3 kHz) band lightning-radiated electromagnetic waves propagate with extremely low attenuation (roughly below 1 dB/Mm) within the Earth-ionosphere waveguide which makes possible the formation of global electromagnetic resonances, known as Schumann resonances (SRs). The most commonly used description of this resonance field assumes a uniform Earth-ionosphere cavity, i.e. that the propagation conditions for ELF waves are practically the same on the dayside and nightside hemispheres, which is the most vulnerable simplification of these models. 

In this work we present two different forward models for SRs that take into consideration the day-night asymmetry of the Earth-ionosphere cavity and are based on the analytical and numerical solutions of the two-dimensional telegraph equation (TDTE). We present numerical tests showing that the two models produce practically the same output, i.e. the relative difference between them is less than 0.4%. The conspicuous conformity between the outputs establishes not only the correctness of the formalisms but the correctness of the implementations (the coding) as well. To the best of the authors’ knowledge this is the first work that verifies this conformity between the two independent solutions. 

We also compare our stationary models with time-dependent solutions of the TDTE as the stationarity of the resonance field may represent the next most vulnerable simplification that needs to be dismissed to approach a more realistic theoretical description of SRs. All these steps in model development serve our aim to infer global lightning activity based on multi-station ELF measurements by applying a sophisticated inversion algorithm.
Energy dissipation at the rupture front of laboratory earthquakes
Authors: Kammer David , McLaskey Gregory
Published: March 2021

The energy dissipated during the friction weakening process at the front of an earthquake rupture, which is known as the fracture energy, is a key earthquake property. It directly affects the nucleation, propagation and arrest of earthquake ruptures, and, is therefore related to important questions, including the maximum possible size of earthquakes at a given fault section. However, estimating the fracture energy in the field is a difficult task and current approaches remain limited. In this work, we present near-fault strain measurements of large-scale laboratory earthquakes on a granite fault. The strain measurements present high-frequency fluctuations while the fault is sliding. These strain fluctuations are indicative of rupture fronts that propagate across the entire fault and occasionally reflect at the boundaries. Here, we will characterize these strain fluctuations by applying fracture-mechanics theory. We will demonstrate that the shape and time scales of the strain fluctuations are well described by the proposed analytical solution. We will further show that by fitting the amplitude of the theory to the experimental measurement, we can estimate the local fracture energy. We apply this process to determine the fracture energy for secondary rupture fronts, which appear within the sliding rupture area. The results are consistent with fracture energy estimates from laboratory-earthquake arrest experiments, but are orders of magnitude lower than reported values from small-scale rotary shear friction experiments. We will discuss the implications and potential of these observations.
A new experimental set-up to study the shear strength of snow-mortar interfaces
Authors: Vallero Gianmarco , Barbero Monica , Barpi Fabrizio , Borri-Brunetto Mauro , De Biagi Valerio
Published: March 2021

The progressive failure of a snow layer deposited on a stiff substrate is at the base of the comprehension of several physical processes that can be found both in natural and artificial conditions. For instance, glide avalanches often originate from the reduction of the basal friction between the snowpack and the underlying ground due to the presence of liquid water film or depth hoar at the snow-ground interface. Moreover, the interaction between snow and construction materials relates to many other applications such as the study of new and more efficient snow removal techniques, the safety of travelers along snow covered roads, the snow redistribution from roofs and buildings, etc. 

Despite this large number of application fields, laboratory investigations are still limited. We performed cold room tests on artificially made snow-mortar interface specimens through a direct shear test device. The effects of confinement pressure, temperature and dry snow hardness (due to sintering times) were taken into account. The tests were carried out in displacement-controlled conditions in order to study the entire failure process at the interface and the following irreversible sliding. The results show some interesting and encouraging aspects for understanding the shear strength of the interface. From a micromechanical point of view we recorded the tests with a high-definition video camera and analyzed the data with the Particle Image Velocimetry technique to obtain the motion fields on the external side of the specimens. Here, we present and discuss some preliminary results of the experimental activity and suggest some future implementations and further developments of the studied topic.       
A New Optimisation Tool for Automatic InSAR Time Series Processing with MasTer.
Authors: Smittarello Delphine , d'Oreye Nicolas , Derauw Dominique , Samsonov Sergey , Jaspard Maxime
Published: March 2021

The increasing amount of SAR data available opens new challenges in terms of data storage management and processing load. Fully exploit those large databases requires the developement of automatic processing  chains. The InSAR Mass processing Toolbox for Multidimensional time series (MasTer) is able to combine any type of SAR data to produce automatic unsupervised 2D ground deformation time series, from data download up to updated displaying of 2D time series results on a web page, updated incrementally as soon as a new image is available. We present our last methodological improvement based on the computation of a coherence proxy to guide a pair selection optimization, balancing the use of each image as master and slave. Whereas this new tool reduces the number of DInSAR interferograms computed by up to 75%, it also increases the signal to noise ratio of the time series by reducing the influence of DEM errors and atmospheric noise.
Quantitative estimation on contribution of climate changes and watershed characteristic changes to decreasing streamflow in the Huangshui Basin, China
Authors: Lv Xizhi , Li Shaopeng , Ni Yongxin , Zhang Qiufen , Ma Li
Published: March 2021

In the past 60 years, climate changes and underlying surface of the watershed have affected the structure and characteristics of water resources to a different degree It is of great significance to investigate main drivers of streamflow change for development, utilization and planning management of water resources in river basins. In this study, the Huangshui Basin, a typical tributary of the upper Yellow River, is used as the research area. Based on the Budyko hypothesis, streamflow and meteorological data from 1958-2017 are used to quantitatively assess the relative contributions of changes in climate and watershed characteristic to streamflow change in research area. The results show that: the streamflow of Huangshui Basin shows an insignificant decreasing trend; the sensitivity coefficients of streamflow to precipitation, potential evapotranspiration and watershed characteristic parameter are 0.5502, -0.1055, and 183.2007, respectively. That is, an increase in precipitation by 1 unit will induce an increase of 0.5502 units in streamflow, and an increase in potential evapotranspiration by 1 unit will induce a decrease of 0.1055 units in streamflow, and an increase in the watershed characteristic parameter by 1 unit will induce a decrease of 183.2007 units in streamflow. Compared with the reference period (1958-1993), the streamflow decreased by 20.48mm (13.59%) during the change period (1994-2017), which can be attribution to watershed characteristic changes (accounting for 73.64%) and climate change (accounting for 24.48%). Watershed characteristic changes exert a dominant influence upon the reduction of streamflow in the Huangshui Basin.
Probabilistic Temperature Forecasting with a Heteroscedastic Autoregressive Ensemble Postprocessing model
Authors: Möller Annette , Groß Jürgen
Published: March 2021

To account for uncertainty in numerical weather prediction (NWP) models it has become common practice to employ ensembles of NWP forecasts. However, forecast ensembles often exhibit forecast biases and dispersion errors, thus require statistical postprocessing to improve reliability of the ensemble forecasts.
This work proposes an extension of a recently developed postprocessing model for temperature utilizing autoregressive information present in the forecast error of the raw ensemble members. The original approach is modified to let the variance parameter additionally depend on the ensemble spread, yielding a two-fold heteroscedastic model. Furthermore, a high-resolution forecast is included into the postprocessing model, yielding improved predictive performance. Finally, it is outlined how the autoregressive model can be utilized to postprocess ensemble forecasts with higher forecast horizons, without the necessity of making fundamental changes to the original model. To illustrate the performance of the heteroscedastic extension of the autoregressive model, and its use for higher forecast horizons we present a case study for a data set containing 12 years of temperature forecasts and observations over Germany. The case study indicates that the autoregressive model yields particularly strong improvements for forecast horizons beyond 24 hours ahead.
Rossby wave energy: a local Eulerian isotropic invariant
Authors: Maas Leo , Kloosterziel Rudolf
Published: March 2021

Conservation laws relate the local  time-rate-of-change of the spatial integral of a density function to the divergence of its  flux through the boundaries of the integration domain. These provide integral constraints on the spatio-temporal development  of a field. Here we show  that  a new type of conserved quantity exists, that does not require integration over a particular domain but which holds locally,  at any point in the field.  This is derived for the pseudo-energy density of  nondivergent Rossby waves where  local invariance is obtained for (1) a single plane wave, and (2) waves produced by an impulsive point-source of vorticity. 

The definition of pseudo-energy used here  consists of a conventional kinetic part, as well as an unconventional pseudo-potential part, proposed by  Buchwald (1973).  The anisotropic nature of the nondivergent energy flux that appears in response to the point source further clarifies the role of the beta plane in the  observed western intensification of ocean currents. 
Modification of phytoplankton group diversity over submesoscale fronts
Authors: Haëck Clément , Levy Marina , Bopp Laurent , El Hourany Roy
Published: March 2021

Over large parts of the ocean, submesoscale fronts are known to enhance total phytoplankton abundance because they are the location of intense vertical transport of nutrients. Disparate in situ observations suggest that such frontal dynamics not only affects the total biomass of phytoplankton, but also significantly modifies its composition. Here we make use of a newly developed algorithm able to distinguish a set of phytoplankton-specific pigments to statistically explore the change in phytoplankton community composition over basin-wide regions. We use 15 years of SST and reflectance data from the MODIS sensor on the Aqua satellite, at 1km and daily resolutions and focus on the oligotrophic North Atlantic subtropical gyre and on the more productive gulf stream region. We locate submesoscale fronts by computing an index quantifying SST patchiness. Our results confirm that submesoscale fronts are collocated with elevated Chlorophyll-a concentration and show significant changes in phytoplankton composition. These results underline the influence of submesocale dynamics on phytoplankton diversity, and stress the need to better understand the underlying mechanisms.
Triggering an Unexpected Earthquake in an Uncoupled Subduction Zone
Authors: Furlong Kevin P. , Herman Matthew W.
Published: March 2021

In the 1970’s, the Shumagin Islands region of the Alaska subduction zone was identified as a seismic gap expected to host a future great (Mw >8.0) earthquake. More recent geodetic data indicate this region is poorly coupled, and the geologic record shows little evidence of past large events - leading to current thinking of the “Shumagin Gap” as a region of low seismic hazard. From July to October 2020 (with aftershocks continuing through the time of this abstract submission in January), a series of earthquakes occurred in this region, potentially incompatible with this low-coupling interpretation. The initial Mw 7.8 plate interface thrust faulting earthquake on July 21st straddled the eastern edge of the Shumagin Gap, followed by an Mw 7.6 strike-slip earthquake on October 19th within the slab under the eastern side of the Shumagin Gap. Stress modeling indicates that this strike-slip earthquake is in fact favored if the Shumagin Gap has low coupling, whereas a highly coupled Shumagin Gap would inhibit that type and location of earthquake. The initial thrust earthquake and its afterslip significantly enhanced the strike-slip stress loading within the subducting slab, helping to trigger that event. We find that although regions such as the Shumagin Gap have a low seismogenic potential for plate interface thrusting, the existence of this decoupled region increases the potential for intra-plate strike-slip faulting in association with more typical subduction earthquakes on adjacent coupled segments of the plate boundary. Therefore, the seismic and tsunami potential near these uncoupled regions might be greater than previously thought.
Modifying emissions data and projections to incorporate the effects of lockdown in climate modelling
Authors: Lamboll Robin , Forster Piers , Jones Chris , Skeie Ragnhild , Fiedler Stephanie , Samset Bjørn , Rogelj Joeri
Published: March 2021

Lockdowns to avoid the spread of COVID-19 have created an unprecedented reduction in human emissions, however emissions estimates are typically only available after one or more years, making it hard to incorporate these reductions into emissions projections. In this talk we will outline how mobility data and power usage can nowcast country-and-sector emissions of various gases. In this way we show that the short-term impact of lockdown on emissions data is not expected to be significant for long-term temperature trends.

We will also outline how different recovery pathways can be made using basic longer-term emissions projections and how to construct detailed scenarios for non-CO2 emissions, using assumptions about the effects of lockdown on nationally determined contributions and a new software package called Silicone that can infill missing greenhouse gas emissions. Silicone allows the consistent incorporation of tradeoffs between emission species as modelled by IAMs, and as expressed in available greenhouse gas emission scenarios, to be applied to the proposed pathways. We will then show how to make these projections into the more detailed, gridded, CMIP-6 compatible emissions estimates that are required to run General Circulation Models (GCM).
Spatial and vertical determination of chosen potentially toxic metals and soil properties on a former sewage farm near Berlin
Authors: Sut-Lohmann Magdalena , Ramezany Shaghayegh , Klos Friederike , Raab Thomas
Published: March 2021

In the past 150 years, sewage disposal onto agricultural land was a common practice around the world that resulted in accumulation of organic matter, salts, nutrients and heavy metals in the soils and the subsequent percolation into the groundwater. We present a study conducted on a former sewage farm in Germany, state of Brandenburg, were wastewater coming from Berlin was used for more than one century to irrigate the surrounding fields. In the area of a sewage sedimentation basin, 110 soil samples at the depth of 15-20 cm (waste layer) and 4 boreholes (10 samples up to 100 cm depth) were collected in order to determine pH, LOI and concentration of chosen metals. For the elemental analysis, two methods: X-ray fluorescence (XRF) and Atomic Emission Spectroscopy (MP-AES) were used. The analysis confirmed the presence of relatively homogenous sewage waste layer at the 20 cm depth, characterized by slightly acidic to neutral pH (6.3-7.5), high OM accumulation (up to 49%) and elevated concentrations of potentially toxic chosen metals (Cu, Ni, Pb, Cr and Zn). The correlation analysis performed by R software revealed strong between metal distribution and OM content. The XRF elemental analysis performed prior and after LOI, revealed metal concentration increase in mineral samples (up to 50% of the original value). An empirical correlation using a linear regression was found between OM content loss and metal concentration increase. Comparison of the AES and XRF elemental analysis of the mineral samples revealed significantly higher results for the X-ray fluorescence method, except for Cr. A correction factor, based on OM reduction, applied to the values, resulted in better correlation of XRF and AES results, questioning feasibility of this method for samples highly affected by sewage influence.
Disentangling the impact of air-sea interaction and boundary layer cloud formation on stable water isotope signals in the warm sector of a Southern Ocean cyclone 
Authors: Thurnherr Iris , Wernli Heini , Aemisegger Franziska
Published: March 2021

Stable water isotopes in marine boundary layer water vapour are strongly influenced by the strength of air-sea moisture fluxes and are thus tracers of air-sea interaction. Air-sea moisture fluxes in the extratropics are modulated by large-scale air advection, for instance the advection of warm and moist air masses in the warm sector of extratropical cyclones. A distinct isotopic composition of water vapour in the latter environment has been observed in near-surface water vapour over the Southern Ocean during the 2016/17 Antarctic Circumnavigation coordinated by the Swiss Polar Institute. Most prominently, the second-order isotope variable d-excess shows negative values in the cyclones’ warm sector. Here, we present three single-process air parcel models, which simulate the evolution of d-excess and specific humidity in an air parcel induced by dew deposition, decreasing ocean evaporation or upstream cloud formation, respectively. The air-parcel models are combined with simulations with the isotope-enabled numerical weather prediction model COSMOiso (i) to validate the air parcel models, (ii) to study the extent of non-linear interactions between the different processes, and (iii) to quantify the relevance of the three processes for stable water isotopes in the warm sector of the investigated extratropical cyclone. This analysis reveals that dew deposition and decreasing ocean evaporation lead to the strongest d-excess decrease in near-surface water vapour in the warm sector. Furthermore, COSMOiso air parcel trajectories show that the persistent low d-excess observed in the warm sector of extratropical cyclones is not a result of material conservation of low d-excess. Instead the latter feature is sustained by the continuous production of low d-excess values in new air parcels entering the warm sector. We show that with the mechanistic approach of using single-process air parcel models we are able to simulate the evolution of d-excess during the air parcel’s transport. This improves our understanding of the effect of air-sea interaction and boundary layer cloud formation on the stable water isotope variability of marine boundary layer water vapour.
Lagrangian eddy tracking reveals the Eratosthenes anticyclonicattractor in the eastern Levantine basin
Authors: Barboni Alexandre , Lazar Ayah , Stegner Alexandre , Moschos Evangelos
Published: March 2021

Statistics of anticyclone activity and trajectories in the southeastern Mediterranean sea over the period 2000-2018
is created using the DYNED atlas, which links the automated mesoscale eddy detection by the AMEDA algorithm with in
situ oceanographic observations. This easternmost region of the Mediterranean sea, delimited by the Levantine coast and
Cyprus, has a complex eddying activity, which has not yet been fully characterized. Using Lagrangian tracking
to investigate the eddy fluxes and interactions between different subregions in this area, we find that the southeastern Levantine
area is isolated, with no anticyclone exchanges with the western part of the basin. Moreover the anticyclonic structure above
the Eratosthenes seamount is identified as being an anticyclone attractor, differentiated from other anticyclones and staying
around this preferred position up to four years with successive mergings. Colocalized in situ profiles inside eddies provide
quantitative information on their subsurface structure and show that similar surface signatures correspond to very different
physical properties. Despite interannual variability, the so-called "Eratosthenes attractor" stores a larger amount of heat and
salt than neighboring anticyclones, in a deeper subsurface anomaly that usually extend down to 500 m. This suggests that this
attractor could concentrate heat and salt from this sub-basin, which will impact the properties of intermediate water masses
created there.
Smaller average stratospheric aerosol sizes after volcanic eruptions in 2018 and 2019
Authors: Wrana Felix , von Savigny Christian , Thomason Larry W.
Published: March 2021

We present surprising results of our stratospheric aerosol size retrieval which is using the SAGE III/ISS solar occultation measurements, that started in 2017. Due to the broad wavelength spectrum covered by the instrument a robust retrieval of the median radius, mode width and number density of monomodal lognormal size distributions is possible.

In the timeframe of SAGE III’s operation so far three small to mid intensity volcanic eruptions that reached and perturbed the stratospheric aerosol layer were observed by the instrument: The Ambae eruptions (15.3°S) in spring of 2018 and the Raikoke (48.3°N) and Ulawun (5.05°S) eruptions, both in June 2019. While the Raikoke eruption led to an increase in the median radius of the stratospheric aerosols, which was to be expected and is in line with previous observations, the Ambae and Ulawun eruption had a different effect. After both eruptions the average aerosol size decreased, with lower median radii and narrower size distributions, while the number density increased strongly. The observation, that volcanic eruptions may lead to smaller average stratospheric aerosol sizes is a novel one and should be of great interest to the modeling as well as remote sensing community.

We will present the temporal and spatial evolution of the stratospheric perturbations and discuss what may distinguish those three eruptions from each other.
Comparing a new paleomap of European loess landscapes to an atmospheric dust circulation model
Authors: Nett Janina J. (Bösken) , Lehmkuhl Frank , Schaffernicht Erik J. , Pötter Stephan , Schulte Philipp , Ludwig Patrick , Sprafke Tobias , Hambach Ulrich
Published: March 2021

Loess is an important archive of environmental change covering approximately 10% of the Earth’s terrestrial surface. Numerous studies have analyzed loess deposits and in particular loess-paleosol sequences. To analyze these sequences, it is important to know the spatial distribution of aeolian sediments, their location relative to potential source areas, and the geomorphology of the sink area. We investigated these aspects by compiling a new map of aeolian sediments in Europe using highly resolved geodata from 27 countries (Lehmkuhl et al., in press). To determine the most relevant factors for the European loess distribution, we further mapped potential source areas and divided the map into different facies domains. We analyzed the geomorphological and paleoenvironmental effects on the deposition and preservation of Late Pleistocene loess. Finally, the geodata-based results were compared with results obtained from high-resolved regional numerical climate-dust experiments for the Last Glacial Maximum (LGM) in Europe, which were performed with the LGM-adapted Weather Research and Forecasting model coupled with Chemistry (WRF-Chem-LGM; Schaffernicht et al., 2020).  Complementing the mapping-based findings with the WRF-Chem-LGM experiments results in an improved understanding of the Late Pleistocene loess landscape in Europe.

 

References:

Lehmkuhl, F., Nett, J.J., Pötter, S., Schulte, P., Sprafke, T., Jary, Z., Antoine, P., Wacha, L., Wolf, D., Zerboni, A., Hošek, J., Marković, S.B., Obreht, I., Sümegi, P., Veres, D., Zeeden, C., Boemke, B., Schaubert, V., Viehweger, J., Hambach, U. (in press). Loess landscapes of Europe – Mapping, geomorphology, and zonal differentiation. Earth-Science Reviews. Doi: https://doi.org/10.1016/j.earscirev.2020.103496

Schaffernicht, E.J., Ludwig, P., Shao, Y., 2020. Linkage between dust cycle and loess of the last Glacial Maximum in Europe. Atmospheric Chemistry and Physics 20, 4969–4986. Doi:10.5194/acp-20-4969-2020.
Evaluating a method for reconstruction of global, zonal and regional mean temperatures from sparse proxy data
Authors: May Maximilian , Weitzel Nils , Jonkers Lukas , Rehfeld Kira
Published: March 2021

Global mean surface temperature is a fundamental measure for climate evolution in both past and present and a key quantity to evaluate climate simulations. However, for paleoclimate periods, its calculation hinges on proxy data distributed sparsely and inhomogeneously in both space and time. Thus, large sets of different proxy records need to be combined in order to obtain global mean temperature reconstructions, but there is no widely accepted method to perform this task. Building on the work of [1], we suggest and evaluate an algorithm to reconstruct spatially averaged surface temperatures on centennial to orbital timescales. As the most abundant archive for continuous temperature reconstructions, we focus on marine sediment records as input data. Our implementation is applicable to any compilation of sea-surface temperature reconstructions and capable of calculating global, hemispherical and regional temperature. Major steps of the reconstruction algorithm are interpolation to a common timescale, zonal normalization and calculation of spatially weighted sums, including uncertainty propagation via Monte Carlo methods. We assess the applicability of the algorithm by employing it to the PalMod130k marine palaeoclimate data synthesis [2] and to pseudo-proxy data generated from transient simulations of the last glacial cycle. Our results suggest that the algorithm is capable of calculating average temperatures mostly consistent with expectations, however capturing centennial-scale variability is limited due to the low spatio-temporal distribution of the input data. This underlines the importance of both increasing the amount, resolution and age control of proxy data as well as extending the algorithm such that it also incorporates other types of paleoclimate archives.

 

References:

[1]  C. W. Snyder, “Evolution of global temperature over the past two million years,” Nature, vol. 538, no. 7624, pp. 226–228, 2016

[2]  L. Jonkers, O. Cartapanis, M. Langner, N. McKay, S. Mulitza, A. Strack, and M. Kucera, “Integrating palaeoclimate time series with rich metadata for uncertainty modelling:  Strategy and documentation of the PALMOD 130k marine palaeoclimate data synthesis,” Earth System Science Data, vol. 12, no. 2, pp. 1053–1081, 2020
Using satellite data to decipher geodynamics of the northeast Atlantic
Authors: Minakov Alexander , Gaina Carmen
Published: March 2021

We explore the mantle density structure of the northeast Atlantic region by performing constrained linear inversion of the satellite gravity gradient tensor data using statistical prior information. The residual gravity gradient signal and the prior covariance matrix are obtained using a crustal model constrained by updated database of seismic reflection and refraction profiles. We construct a 3D reference density distribution in the upper mantle assuming a pure shear model for lithospheric rifting. The mantle reference density model is consistent with mineral phase equilibria assuming a pyrolitic bulk composition. The forward modeling of the gravity gradients in the 3D reference model is performed on a global scale using a spherical harmonics approach. The northeast Atlantic model is represented using a spherical shell covering the study region down the depth of 410 km. We use tesseroids as mass elements for solving the forward and inverse gravity problem at the regional scale. The relationship between the seismic velocity and density anomalies in the Iceland-Jan Mayen region and the low-density corridor across central Greenland are discussed for understanding the origin of heterogeneities in the upper mantle of the northeast Atlantic region and their possible connections with the Cenozoic Iceland plume activity.
High trace gas concentrations during lowered boundary layer heights at a Swiss tall tower site
Authors: Plach Andreas , Stohl Andreas , Leuenberger Markus
Published: March 2021

Measurements of trace gas concentrations and their fluxes are essential to investigate source regions of greenhouse gases (GHGs) and other pollutants. Most flux towers provide observations at heights of several meters to tens of meters and therefore provide information about possible flux sources on a local spatial scale. Here we present an analysis of trace gas concentration and flux measurements from one of the few European tall towers located close to Beromünster, Switzerland. The tower was initially set up as a CarboCount CH site — a dense GHG observation network run for four years (2012 - 2015) — and is continued since by the University of Bern. The presented measurements are taken at an altitude of 212m above ground. This relatively high observation height results in a flux footprint of the tower of many kilometers and therefore the tower observations are predestined for a source analysis on a much larger scale than typical for flux towers. We analyze subsets of the available time series selected by season, time of day, wind direction, and other criteria. In a first step, the field of view of the tower for these subsets is estimated with a flux footprint parameterization. This is followed by a correlation analysis between various observations. Results indicate particularly high trace gas concentrations during periods of lowered planetary boundary layer heights and wind coming from the Zurich metropolitan area. In a next step we intend to perform a field of view analysis with a Lagrangian atmospheric transport model (Flexpart).
Analysis of the anthropogenic and biogenic NOx emissions over 2008-2017: assessment of the trends in the 30 most populated urban areas in Europe
Authors: Fortems-Cheiney Audrey , Broquet Gregoire , Pison Isabelle , Saunois Marielle , Potier Elise , Berchet Antoine , Dufour Gaelle , Siour Guillaume , Denier van der Gon Hugo , Dellaert Stijn , Boersma Folkert
Published: March 2021

We use the OMI-QA4ECV-v1.1 NO2 tropospheric columns over the 10-yr 2008-2017 period to confront satellite-based trends in NO2 concentrations to those from the state-of-the-art regional chemistry-transport model CHIMERE and to evaluate the bottom-up anthropogenic and biogenic NOx emissions in Europe. A focus is made for the 30 most populated urban areas in Europe. Over urban areas in Western Europe, except for coastal cities, OMI confirm the drop in the simulated CHIMERE NO2 tropospheric columns based on the latest country emission official reporting. OMI does not show significant decreasing trends over Central and Eastern Europe urban areas. Increasing biogenic emissions helps reconciling CHIMERE and OMI trends over urban areas in Central Europe and over rural areas, confirming the importance of accounting for non-anthropogenic emissions to assess long-term trends. Over Eastern Europe, our results question emission reductions estimated for particular sectors and in particular the road transport, public power and industrial emissions.
Network-based approach to unravel sea-surface temperature and streamflow connectivity at different timescales
Authors: Ganapathy Abinesh , Guntu Ravi Kumar , Ozturk Ugur , Merz Bruno , Agarwal Ankit
Published: March 2021

Understanding the interactions between oceanic conditions and streamflow can deepen our knowledge on hydrological aspects. Most studies exploring this relationship only focus on seasonal or annual scales. However, various atmospheric and oceanic phenomena occur at different timescales and need to be accounted to attribute connectivity between sea-surface temperature and streamflow to specific oceanic and climate processes. In this study, we have investigated the influence of sea-surface temperature (SST) on German streamflow at timescales ranging from sub-seasonal to decadal. We apply wavelets' concepts to decompose the time series into multiple frequency signals and fed into complex networks to identify spatial connections. We employ degree centrality metric and average link distance concepts to interpret the outcomes of coupled SST-Streamflow networks. Our results indicate that the SST anomaly at North Atlantic Ocean region has a stable connection with German streamflow at shorter timescales up to annual scale. We also noticed scale-specific connections in the Pacific, Indian and Southern ocean regions at different timescales ranging from seasonal to decadal scale. Scale-specific connections exhibited by the streamflow stations at all timescales makes it difficult to cluster based on degree centrality. We observed that streamflow stations are influenced by short-range local connections at lower timescales and long-range teleconnections at higher time scale. Our preliminary analysis highlight that the low frequent streamflow extremes have long-range connections, usually not captured at the original scale, and geographical proximity plays a role in high-frequency streamflow signals, according to Tobler’s first law of geography. The results obtained from this study reconfirms reported existing streamflow influences and helped gain insights over other possible large-scale climatic influences.
Fennoscandian Ice Sheet glaciation in northwest Arctic Russia during the Last Glacial-Interglacial Transition
Authors: Boyes Benjamin , Pearce Danni , Linch Lorna
Published: March 2021

Previous attempts to reconstruct the glacial history of the last Fennoscandian Ice sheet (FIS) in northwest Arctic Russia have resulted in various Last Glacial-Interglacial Transition (c. 20-10 ka) scenarios, suggesting that the Kola Peninsula was glaciated by the FIS, the Ponoy Ice Cap, or the Kara Sea Ice Sheet. The conflicting glacial interpretations have stemmed, in part, from the use of low-resolution geomorphological and geological maps. The advent of high-resolution remotely-sensed imagery warrants a new glacial reconstruction of ice sheet dynamics in northwest Arctic Russia: we therefore present initial glacial interpretations based on new high-resolution geomorphological mapping.

Geomorphological mapping using high-resolution ArcticDEM and PlanetScope imagery has identified >245,000 glacial landforms, significantly increasing the volume and detail of geomorphological data in the region. Over 66,000 subglacial bedforms (subglacial lineations and subglacial ribs) are used to construct flowsets, which demonstrate that ice flowed from the Scandinavian mountains in the west and across the shield terrain of the Kola Peninsula. Moreover, four possible palaeo-ice streams are identified in the region. Mapping individual moraine hummocks, rather than hummocky moraine spreads as in previous mapping attempts, reveals multiple ice margins across the Kola Peninsula. A noteworthy ~25 km wide belt of hummocky moraines aligned north-south across the Kola Peninsula is tentatively attributed to the Younger Dryas (c. 12.8-11.9 ka) ice marginal zone. The so-called “ring-and-ridge” hummock moraines that are predominantly observed within this ice marginal zone suggest down-wasting and stagnant ice margins. The meltwater landform record also reveals subglacial channel networks along the northern coastline that suggest warm-based conditions of the ice sheet may have been induced by warm currents in the Barents Sea during the last glacial-interglacial transition.

This research will provide crucial empirical data for validating numerical model simulations of the FIS, which in turn will further our understanding of ice sheet dynamics in other Arctic, Antarctic, and Alpine regions.