bluuebunny/crossref_metadata_2025 huggingface dataset:
Climate dominates changes in flood magnitude and timing across China during 1960-2017
Authors: Yang Yixin , Yang Long
Published: March 2021

Riverine floods are exhibiting temporal shifts in both magnitude and timing under the context of climate change as well as human alternations of the river systems (i.e., construction of reservoirs and land management practices). A nation-wide assessment of changes in riverine floods is still lacking over China, despite the societal perception that recent Chinese flood trends are dictated by drastic environmental changes associated with rapid economic development. Here we examine changes in flood magnitude and timing based on the most comprehensive database of annual maximum flood peak discharge (AMF) over China during the period 1960-2017. We find both increasing and decreasing trends in AMF magnitude and timing. Trends in AMF magnitudes range from -4.29% to 2.86% (per year relative to long-term mean flood peak discharge). Decreased AMF magnitudes are observed in central and northern China, while increased AMF magnitudes mainly in northwestern and southern China. The shifts of AMF timing range from -16 days to +18 days per decade. Changes in AMF timing show less spatial consistency than that in AMF magnitude. We categorize the gauged watersheds into human-modified and natural categories. Flood changes in natural watersheds can only be attributed to climate variability. The spatial pattern of changes in AMF magnitude and timing in human-modified watersheds resembles those in natural watersheds, pointing towards the dominant role of climate in dictating recent flood changes over China. Impacts of reservoirs and land management practices are only isolated cases. We further provide a predictive understanding of climatic controls on flood hazards over China (and East Asian countries) by establishing connections between changes in AMF magnitude/timing and climate indices. Our analyses, together with similar efforts in other continents, contribute to a general understanding of space-time dynamics of riverine floods around the globe.
Impacts of climate and land use changes on water variability, using a Budyko framework: case study in Gansu, China
Authors: He Qing , Chun Kwok Pan , Yetemen Omer , Dieppois Bastien , Chen Liang , Pan Xicai
Published: March 2021

Disentangling the effects of climate and land use changes on regional hydrological conditions is critical for local water and food security. The water variability over climate transition regions at the midlatitudes is sensitive to changes in regional climate and land use. Gansu, located in northwest China, is a midlatitude climate transition region with sharp climate and vegetation gradients. In this study, the effects of climate and land‑use changes on water balances are investigated over Gansu between 1981 and 2015 using a Budyko framework. Results show that there is reduced runoff generation potential over Gansu during 1981 and 2015, especially in the southern part of the region. Based on statistical scaling relationships, local runoff generation potential over Gansu are related to the El Nino-Southern Oscillation (ENSO). Intensified El Nino conditions weaken the Asian monsoons, leading to precipitation deficits over Gansu. Moreover, the regional evapotranspiration (ET) is increasing due to the warming temperature. The decreasing precipitation and increasing ET cause the decline of runoff generation potential over Gansu. Using the dynamical downscaling model outputs, the Budyko analysis indicates that increasing coverage of forests and croplands may lead to higher ET and may reduce runoff generation potential over Gansu. Moreover, the contributions of climate variability and land‑use changes vary spatially. In the southwest part of Gansu, the impacts of climate variability on water variations are larger (around 80%) than that of land‑use changes (around 20%), while land use changes are the dominant drivers of water variability in the southeast part of the region. The decline of runoff generation potential reveals a potential risk for local water and food security over Gansu. The water‑resource assessment approach developed in this study is applicable for collaborative planning at other climate transition regions at the midlatitudes with complex climate and land types for the Belt and Road Initiative.
The Global Impacts of COVID-19 Lockdowns on Short-Lived Climate Forcers: Highlights from a Critical Review
Authors: Gkatzelis Georgios , Gilman Jessica , Brown Steven , Eskes Henk , Gomes Rita , Lange Anne , McDonald Brian , Peischl Jeff , Petzold Andreas , Thompson Chelsea , Kiendler-Scharr Astrid
Published: March 2021

The coronavirus-19 (COVID-19) pandemic led to government interventions to limit the spread of the disease that are unprecedented in the last decades. Stay at home orders and other measures led to sudden decreases in atmospheric emissions, most visibly from the transportation sector. We present a review of the current knowledge and understanding of the influence of these emission reductions on atmospheric pollutants concentration and notably air quality with a focus on NO2, PM2.5, and O3 based on more than 200 papers utilizing observations from ground-based and satellite remote sensing instruments. We use the government stringency index as an indicator for the severity of lockdown measures and show how key air pollutants change as the stringency index increases. Changes in NO2 and PM2.5 mass concentration are well-studied globally. The observed decrease of NO2 with increasing stringency index is in general agreement with emission inventories that account for the lockdown. Due to the important influence of atmospheric chemistry on O3 and PM2.5 concentrations, their responses may not be linear with respect to primary pollutants. At most sites, we found O3 increased, whereas PM2.5 decreased slightly, with increasing stringency index. Changes in the PM2.5 composition are found to be understudied and not well-quantified so far. We highlight future research needs for utilizing the emerging data sets covering a full seasonal cycle as a preview of a future state of the atmosphere in a world with targeted permanent reductions of emissions. Finally, we emphasize the need to account for the effects of meteorology, long-term trends, and atmospheric chemistry when determining the lockdown effects on pollutant concentrations, especially on PM2.5.
Three-dimensional distribution of Mount Etna’s emissions during the EPL-REFLECT campaign in July 2019
Authors: Sannino Alessia , Boselli Antonella , Leto Giuseppe , Scollo Simona , Sanchez Ricardo Zanmar , Amoruso Salvatore , Spampinato Letizia , Sellitto Pasquale
Published: March 2021

Mount Etna (Italy) is the most high-impact volcanoes on Mediterranean scale mainly due to its eruptive activity and continuous passive degassing, and the inherent large amount of effluents released into the atmosphere. Mount Etna’s emission mainly originate from the summit craters at an altitude of about 3300 m, feeding frequently volcanic gases and aerosols into the free troposphere. Consequently, their effects on the atmosphere and regional climate system span over relatively long spatiotemporal scales.

In order to better understand the role that Mount Etna’s emissions play on the atmospheric composition and radiative balance in the Mediterranean area, multidisciplinary and multi-scale studies have been carried out since a few years within the different phases of the EtnaPlumeLab (EPL) research cluster. A part of the EPL effort is based on dedicated field campaigns, that aim at the characterization of volcanic sources emissions and nears-source plume dispersion and evolution.

In this work, we investigate the three-dimensional (3D) distribution of the volcanic aerosols from Mount Etna observed during the most recent EPL field campaign, named EPL-REFLECT (near-source estimations of Radiative EFfects of voLcanic aErosols for Climate and air quality sTudies) carried out within the Transnational Access component of the EUROVOLC project. This field campaign completes the previous EPL-RADIO (Radioactive Aerosols and other source parameters for better atmospheric Dispersion and Impact estimatiOns) campaign. Here we discuss the observations of a multiparametric LiDAR system AMPLE. The LiDAR is equipped with a fast scanning, double depolarization (at 532 and 355 nm) and high repetition laser source (1kHz), which is an essential point to derive time series of 3D-resolved aerosol properties near Etna. During the 8-12th of July 2019 period, day/night LiDAR measurements were performed by AMPLE from the astronomical observatory of the INAF-Catania in the location of Serra la Nave at 1725 m a.s.l., pointing towards the summit of Mount Etna. In particular, on the July 11th, the scan was performed with time-steps of 15 minutes at different angles from the top of the volcano to the zenith. These acquisitions highlight the atmospheric evolution of two layers related to two distinct degassing episodes. A comparative analysis with wind speed information and the integration with complementary photometric ground measurements have further constrained this 3D characterization and the evolution of these layers, including those outside the LiDAR field of view.
Metabolic regime shifts and ecosystem state changes are decoupled in a large river
Authors: Diamond Jacob , Moatar Florentina , Cohen Matthew , Poirel Alain , Martinet Cécile , Maire Anthony , Pinay Gilles
Published: March 2021

Aquatic ecosystem recovery from anthropogenic degradation can be hampered by internal feedbacks that stabilize undesirable states. The challenges of managing and predicting alternative states in lakes are well known, but state shifts in rivers and their attendant effects on ecosystem function remain understudied despite strong recent evidence that such shifts can and do occur. Using three decades of measurements of key state variables such as turbidity, nutrient concentrations, Corbicula fluminea clam densities, and chlorophyll a, including hourly dissolved oxygen, we investigated a sudden shift from phytoplankton to macrophyte dominance in the middle Loire River (France), and its associated effects on the rivers metabolic regime. We show, instead, that despite large and synchronous shifts across all state variables, changes in gross primary production and ecosystem respiration were modest (25% and 14% declines, respectively) and that these shifts lagged the ecosystem state changes by a decade or more. The shift to a macrophyte-dominated state reduced the sensitivity of primary production to abiotic drivers, altered element cycling efficiency, flipped the net carbon balance from positive to negative, and, crucially, weakened the temporal coupling between production and respiration. This weakened coupling, detected using Granger causality, increased the temporal autocorrelation of net ecosystem production, yielding a robust early warning indicator of both state- and metabolic-shifts that may provide valuable guidance for river restoration.
Inter-seasonal investigation of coupled C & N greenhouse gas fluxes in pristine northern ecosystems
Authors: van Delden Lona , Boike Julia , Tuittila Eeva-Stiina , Vesala Timo , Treat Claire
Published: March 2021

Accurate annual greenhouse gas (GHG) budgets are the crucial baseline for global climate change forecast scenarios. On the other hand, the parameterization of these forecast models requires more than high-quality GHG datasets, but also the constant improvement of the representation of GHG producing and consuming processes. Extensive research efforts are therefore focusing on increasing our knowledge of the main GHG producing carbon (C) and nitrogen (N) cycles, though surprisingly not so much into their direct interaction. Most annual GHG budgets from pristine northern ecosystems are based on interpolated datasets from sampling campaigns mainly taken during the growing season. Within the ERC funded FluxWIN project, we are investigating how soil and pore water C & N interact and their biogeochemical GHG drivers change over seasons. Freeze-thaw events have previously been identified as significant GHG drivers by rapidly changing moisture and oxygen conditions in the soil matrix, but it remains unclear if and how C & N coupling contributes to these non-growing season emissions. Therefore, a fully automated static chamber system is monitoring GHG fluxes in high frequency at a boreal peatland ecosystem in Siikaneva, Finland. Nutrient stocks and biogeochemical dynamics within the soil matrix are compared to GHG soil-atmosphere exchange in the form of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) all year-round. We control for climatic variability and isolate differences in non-growing season emissions by using a moisture gradient from well-drained upland soils to adjacent wetland ecosystems. The use of these automated high-frequency GHG measurements in combination with year-round biogeochemical monitoring maximizes the likelihood of capturing episodic emissions and their drivers, which are particularly important during fall freeze and spring thaw periods. The gained information on the coupled C & N biogeochemical cycles will improve feedback estimates of climate change by including non-growing season processes in global-scale process-based models.
The open-air laboratory of the Grandes Jorasses glaciers. An opportunity for developing close-range remote sensing monitoring systems
Authors: Giordan Daniele , Fabrizio Troilo
Published: March 2021

Glaciological phenomena can have a strong impact on human activities in terms of hazards and freshwater supply. Therefore, scientific observation and continuous monitoring are fundamental to investigate their current state and recent evolution. Strong efforts in this field have been spent in the Grandes Jorasses massif (Mont Blanc area), where several break-offs and avalanches from the Planpincieux Glacier and the Whymper Serac (Grandes Jorasses Massif) threatened the Planpincieux hamlet in the past. In the last decade, multiple close-range remote sensing surveys have been conducted to study the glaciers.

Two time-lapse cameras monitor the Planpincieux Glacier since 2013. Its surface kinematics is measured with digital image correlation. Image analysis techniques allowed at classifying different instability processes that cause break-offs and at estimating their volume. The investigation revealed possible break-off precursors and a monotonic relationship between glacier velocity and break-off volume, which might help for risk evaluation.

A robotised total station monitors the Whymper Serac since 2009. The extreme high-mountain conditions force to replace periodically the stakes of the prism network that are lost.

In addition to these permanent monitoring systems, five campaigns with different commercial terrestrial interferometric radars have been conducted between 2013 and 2019. In 2020, two terrestrial GBSAR were installed for the improvement of the monitoring network of both glaciers. The adopted monitoring network is also composed by a Doppler radar that controls the potential detachment of ice blocks from the frontal part of the Planpincieux glacier. Besides, helicopter-borne LiDAR, terrestrial laser scanner and structure from motion applied to photo mosaics acquired by helicopter and UAV provided a dense series of high-resolution DTMs. Finally, new helicopter ground-penetrating radar campaigns were conducted in 2020 to evaluate the Planpincieux and Grandes Jorasses glaciers' thickness.

The survey activity conducted in the Grandes Jorasses area in the last decade is probably one of the most variegated in the European Alps. Thereby, this area has become an open-air laboratory for experimenting with new technological or methodological solutions for glaciological close-range remote sensing monitoring which might be applicable in other contexts.
Modeling the Environmental Dynamics of the Northern Adriatic Sea with an explicit benthic-pelagic coupling.
Authors: Zavatarelli Marco , Scroccaro Isabella , Lovato Tomas
Published: March 2021

In the framework of the European Project H2020 "ODYSSEA" (Operating a network of integrated observatory systems in the Mediterranean SEA, http://odysseaplatform.eu/) a forecasting modeling system of the coupled physical and biogeochemical conditions of the Northern Adriatic Sea is under development.

The modeling system consists of the on-line coupling of the European general circulation model - NEMO (Nucleus for European Modeling of the Ocean, https://www.nemo-ocean.eu/), with the marine biogeochemical model - BFM (Biogeochemical Flux Model, bfm-community.eu/).
The biogeochemical component of the model includes the simulation of the biogeochemical processes of both water column and sediments and their coupling. The model is run for the first time in the Northern Adriatic Sea with an explicit benthic-pelagic coupling.

The horizontal spatial discretization is defined by a rectangular grid of 315 × 278 cells, having a horizontal resolution of about 800 m. The vertical resolution is defined at 2 m, with 48 z-levels regularly spaced. Currently the atmospheric forcing are the ECMWF 6hr analysis atmospheric fields. The river supplies of fresh water and nutrient salts consider the daily runoff of the Po river, while the other rivers within the study area are included as climatological values. The open boundary conditions of the modeling system come from the Copernicus Marine Environment Monitoring Service (CMEMS, http://marine.copernicus.eu/).

In this work, the hindcast simulations encompassing the period 2000 – 2009 are validated against available observations from in situ and satellite platforms for sea surface temperature, chlorophyll-a and dissolved inorganic nutrients and, in order to evaluate the impact of a resolved benthic biogeochemical dynamics,  compared against simulations results obtained utilising a simple benthic closure parameterisation.
Geo-environmental analysis of terraced slopes and dry-stone walls in Can Grau area (Garraf Park, Catalunya, Spain): preliminary results from the Stonewalls4life project.
Authors: Mandarino Andrea , Vigo Andrea , Cevasco Andrea , Varona Prellezo Patricia , Valbuena-Ureña Emilio , Guillén-Villar Abraham , Traver-Vives Montserrat , Garcia-Martínez Dolors , Firpo Marco
Published: March 2021

Stonewalls4life is an E.U. Life project started in the second half of 2019 involving many subjects, both public bodies and privates, in a multidisciplinary working group. The main objective of the project is to demonstrate how an ancient technology for land use, drystone walling, can be effectively considered to improve the resilience of the territory to climate change by adopting a socially and technically innovative approach.

The project actions are being performed at Manarola, within the Cinque Terre National Park (eastern Liguria, north-western Italy). The pilot site is a narrow strip of land close to the seaside and characterized by small valleys with steep terraced slopes. This anthropogenic landscape represents a high-value peculiarity attracting more than three million tourists every year.

Three replication sites were identified in order to demonstrate the transferability and replicability of the project actions: two are located within the Cinque Terre Natural Park territory and one is in the Can Grau area (Garraf Park, Catalunya, Spain).

The Spanish site is currently under evaluation. An extensive geological, geomorphological, and land-use-land-cover (LULC) analysis is now being carried out in the Can Grau area to define its environmental features, especially concerning geological aspects and land use, and focusing on terraced areas and their state of conservation. This study aims to identify a specific suitable site for the replication of the project actions that will be carried out in Manarola, namely for dry-stone walls recovery, and is based on a multitemporal analysis of aerial images performed in a GIS environment and a wide collection and review of bibliographic data.

This contribution illustrates the preliminary results of the Can Grau area analysis, focusing in particular on the distribution of terraced areas and the variation of LULC from the 1950s to the present day. From this study emerges a progressive abandonment of terraced areas used for cultivation, although, according to historical sources, this process mostly occurred after the phylloxera appeared in the late 19th century, seriously affecting the most important agricultural activity in the Garraf, namely the viticulture.

The outcomes from this study will be useful in terms of both Stonewalls4life project implementation and overall land management, particularly aiming to restore a man-made geomorphological heritage and mitigate geo-hydrological risk.
Reconciling geodetic and geologic estimates of coastal vertical land motion around the British Isles
Authors: A. Karegar Makan , E. Engelhart Simon , Kusche Jürgen , A. Milne Glenn , L. Bradley Sarah
Published: March 2021

Karegar et al. (2016, GRL) showed that independent estimates of vertical land motion from geodetic and geologic techniques are critical for understanding coastal surface motion caused by geological versus human-induced processes along the Atlantic coast of North America. Motivated by these results, we extend our analysis to the British Isles where good quality and spatially dense constraints are available from a continuous GNSS network and a state-of-the-art Holocene sea-level database. Glacial Isostatic Adjustment (GIA) along the Atlantic coast of North America causes the land surface to sink (up to -1.5 mm/yr), exacerbating tidal-induced flooding effects of sea-level rise. The British Isles are also subjected to proglacial forebulge collapse associated with the GIA response to the ancient Fennoscandian and British-Irish Ice Sheets. Here, we present an up-to-date and precise analysis based on continuous GNSS (combined GPS and GlONASS observations) and geologic records of late Holocene sea-level change to examine residuals between rates on these different timescales to determine if there is a significant residual and, if so, the processes responsible for the rate change.
I spy with my hyperspectral eye: unique reflectance database of plastics and riverbank-harvested litter
Authors: Tasseron Paolo , van Emmerik Tim , Peller Joseph , Schreyers Louise , Biermann Lauren
Published: March 2021

Airborne and spaceborne remote sensing (RS) collecting hyperspectral imagery provides a promising way forward for detection and monitoring of riverine and marine plastic pollution. However, a major challenge in the application of RS techniques is the lack of fundamental understanding of spectral signatures of floating plastic debris at multiple scales. Recent work emphasised the case for open-access hyperspectral reflectance reference libraries of commonly used polymer items. In this paper, we present a high-resolution hyperspectral image database of a unique mix of (i) 40 virgin macroplastic items, (ii) organic material of plant leaves, tree leaves and riparian vegetation, and (iii) 50 items of riverbank-harvested macrolitter including plastics and other anthropogenic debris. We used a double camera setup that covered the VIS-SWIR range from 400-1700 nm in a dark room experiment with controlled illumination. The cameras scanned the samples floating in water and captured high-resolution images in 336 spectral bands. From these images we identified diagnostic absorption features for different materials, item categories, and plastic polymers. The identification was done by applying a linear discriminant analysis to the spectra, allowing the creation of combined band indices distinguishing between the different item types and polymer categories. We present reflectance spectra of all items in our image dataset, complemented by easy-to-interpret visual representations of derived indices. We demonstrate the importance of high-resolution reference reflectance libraries, to (i) further optimise existing remote sensing monitoring techniques, and (ii) contribute towards the development of future plastic monitoring and classification missions.
Analysis of spatial dimensions and explicit multifractal modelling for the deployment of green areas in an urban agglomeration.
Authors: Castellanos Diaz Leydy Alejandra , Bonin Olivier , Versini Pierre Antoine , Tchiguirinskaia Ioulia
Published: March 2021

The need to adapt and increase the resilience of urban areas regarding the issues induced by urbanization and climate change effects (e.g. floods, Urban Heat Island, pandemics, etc.), has led to propose several strategies as the Natural-Based Solutions (NBS), which are focus on restoring natural processes such as infiltration and evapotranspiration (ET) in urban areas. In consequence, the increasing interest on NBS installation (highly supported by the H2020 program of the European Commission) by urban planners, decision-makers, researchers and the residing population has conducted to question the most efficient ways of NBS deployment. In this context, the urban dynamics (e.g. population density, land use patterns, transport network, etc.) and the distribution of green areas at different spatial scales play a key role that characterise the urban development in the territory.

Based on the study of an urban agglomeration named Est-Ensemble, located at the east of Paris (France), this research aims to: i) determinate the fractal dimension of the built-up and green areas by using 2 different box-counting methods; ii) set the potential areas to install NBS, through the development of an iterative downscaling scheme over the built-up structure with the software Fractalopolis, and following a polycentric approach inspired on the urban form of Ile de France Region, and iii) assess the population access to the nearest green spaces and deficit of green spaces.

Further, from local scale measurements of ET made close to Est-Ensemble agglomeration, the authors carried out a multifractal analysis of the ET data to better evaluate the observed scaling behaviour. This will be coupled with spatial approach developed above to evaluate the impact of temperature reduction of different land use scenarios. This research is partly supported by the French ANR EVNATURB project.
Quantification of aerosol effects on marine boundary layer clouds with machine learning
Authors: Zipfel Lukas , Andersen Hendrik , Cermak Jan
Published: March 2021

Satellite observations are used in regional machine learning models to quantify sensitivities of marine boundary-layer clouds (MBLC) to aerosol changes.

MBLCs make up a large part of the global cloud coverage as they are persistently present over more than 20% of the Earth’s oceans in the annual mean.They play an important role in Earth’s energy budget by reflecting solar radiation and interacting with thermal radiation from the surface, leading to a net cooling effect. Cloud properties and their radiative characteristics such as cloud albedo, horizontal and vertical extent, lifetime and precipitation susceptibility are dependent on environmental conditions. Aerosols in their role as condensation nuclei affect these cloud radiative properties through changes in the cloud droplet number concentration and subsequent cloud adjustments to this perturbation. However, the magnitude and sign of these effects remain among the largest uncertainties in future climate predictions.

In an effort to help improve these predictions a machine learning approach in combination with observational data is pursued:

Satellite observations from the collocated A-Train dataset (C3M) for 2006-2011 are used in combination with ECMWF atmospheric reanalysis data (ERA5) to train regional Gradient Boosting Regression Tree (GBRT) models to predict changes in key physical and radiative properties of MBLCs. The cloud droplet number concentration (Nd) and the liquid water path (LWP) are simulated for the eastern subtropical oceans, which are characterised by a high annual coverage of MBLC due to the occurrence of semi-permanent stratocumulus sheets. Relative humidity above cloud, cloud top height and temperature below the cloud base and at the surface are identified as important predictors for both Nd and LWP.  The impact of each predictor variable on the GBRT model's output is analysed using Shapley values as a method of explainable machine learning, providing novel sensitivity estimates that will improve process understanding and help constrain the parameterization of MBLC processes in Global Climate Models.
The Impact of Solar Activity on Forecasting the Upper Atmosphere via Assimilation of Electron Density Data
Authors: Kodikara Timothy , Zhang Kefei , Pedatella Nicholas M. , Borries Claudia
Published: March 2021

We present a comprehensive comparison of the impact of solar activity on forecasting the ionosphere and thermosphere. Here we investigate the response of physics-based TIE-GCM (thermosphere-ionosphere-electrodynamics general circulation model) in a data assimilation scheme through assimilating radio occultation (RO)-derived electron density (Ne) using an ensemble Kalman filter (KF). Constellation observations of Ne profiles offer opportunities to assess the accuracy of the model forecasted state on a global scale. In this study, we emphasise the importance of understanding how the assimilation results vary with solar activity, which is one of the primary drivers of thermosphere-ionosphere dynamics.

We validate the assimilation results with independent RO-derived GRACE (Gravity Recovery and Climate Experiment mission) Ne data. The main result is that the forecast Ne agree best with data during the solar minimum compared to solar maximum. The results also show that the assimilation scheme significantly adjusts both the nowcast and forecast states during the two solar activity periods. The results show that TIE-GCM significantly underestimate Ne in low altitudes below 250 km and the assimilation of Ne is not as effective in these lower altitudes compared to higher altitudes. The results demonstrate that assimilation of Ne significantly impacts the neutral mass density estimates via the KF state vector. This impact is larger during solar maximum than solar minimum relative to a control run. The results also demonstrate that the impact of assimilation of Ne on neutral mass density state persists through to forecast state better during solar minimum compared to solar maximum. The results are useful to explain the inherent model bias, to understand the limitations of the data, and to demonstrate the capability of the assimilation technique.
The 4.2 ka event and the end of the ‘Temple Period’ in Malta
Authors: Groucutt Huw S.
Published: March 2021

The compact size of the semi-isolated Maltese archipelago and its relatively challenging environmental conditions, with limited soil cover and variable precipitation averaging around 600 mm a year, mean that the area offers an important case study of human-environment interactions. Following an initial phase of Neolithic settlement, the ‘Temple Period’ in Malta began from around 5.8 ka and within a few hundred years the spectacular ‘temples’ which characterize the period and are among the oldest buildings in the world began to be constructed. After over a thousand years this long-lived culture came to a seemingly abrupt end at ca. 4.4 to 4.2 ka, and was followed by Bronze Age societies with radically different material culture, funerary behaviour, and architecture. Various ideas concerning the reasons for the end of the Temple Period have been expressed. These range from climate change, to invasion, to social conflict resulting from the development of a powerful ‘priesthood’. Here, the idea that the end of the Temple Period was caused by aridity induced by the 4.2 ka event is tested. The 4.2 ka event is a classic example of an abrupt climate episode, and while it has been linked with several examples of significant societal change, such as the end of the Old Kingdom in Egypt, its details and relevance have been debated. To evaluate the Maltese example, archaeological data is fused with an understanding of the geology and palaeoenvironment of Malta, as well as consideration of the wider regional situation at this time in terms of demography and material culture, as well as the possible role of factors such as disease epidemics. The Maltese example forms a fascinating case study for understanding issues such as chronological uncertainty, disentangling cause and effect when several different processes are involved, and the role of abrupt environmental change in impacting human societies. Ultimately, it is suggested that the 4.2 ka event played a significant role in the end of the Temple Period, but this has to be understood within the specific geological and societal circumstances of the Maltese islands.
Role of inherited structures and magmatism in North Tanzania from high resolution teleseismic P and S body-wave tomographies.
Authors: Gautier Stéphanie , Clutier Adeline , Tiberi Christel , Parat Fleurice , Gibert Benoit , Gregoire Michel
Published: March 2021

The North Tanzanian Divergence (NTD) is a zone of rift initiation. Its surface expression results from interactions between deep-mantle (mantle plume), lithospheric (inherited rheology and stratification, melting...) and crustal (dyke propagation, fault activation...) processes. However, the role of each process on the observed surface activity is still debated, because highly difficult to decorrelate.

We recently carried out a study to obtain enhanced P and S-wave tomography, from the surface down to 150-200 km depth. The particularity of our method consists in its initial velocity model. It is composed of a 1D IASP91 regional velocity model in which we inserted an a priori 3D crustal velocity model with a fine grid. This crustal model was deduced from an independent local tomography inversion.

The P and S images obtained, resulting from the teleseismic inversion of this hybrid method, show strong contrasted velocity anomalies: from 10 % of P (Vp) and S velocity (Vs) variation on the craton, to -17 % below the rift axis. The anomalies locations are consistent with the surface geology (rifting basin, border faults, volcanoes). At a regional scale, the strongest velocity contrasts correspond to the lithospheric inherited structure (Tanzanian craton and Proterozoic belts) boundaries, which control the propagation of the rift. In particular, the Masai cratonic block, south of the NTD, is inferred to have a strong influence in the rift evolution. The transition from the North-South axial valley into three diverging rift arms (Eyasi, Natron-Manyara and Pangani) is likely due to the change in rheology and to the presence of magma along inherited sutures between the craton and the mobile belts.

However, interrogations about the role of the thermal changes, the melt/fluid presence and the mantle composition in the NTD on these velocity anomalies still remain. To distinguish which parameters are acting in the rift, we realize a Vp/Vs ratio map. With this new data, and in the light of parallel petrological studies, we interpret the Vp/Vs anomalies in term of gas and/or melt concentration zones.
Tools and technologies for NEMO models: the case of the Generic Interfaces developed in the framework of IMMERSE
Authors: Stefanizzi Laura , Ciliberti Stefania , Ilicak Mehmet , Coppini Giovanni
Published: March 2021

Setting new model configurations based on NEMO requires the definition of initial/boundary condition and the validation of numerical solutions. In the framework of IMMERSE H2020 project, CMCC is developing new tools and technological capacities for handling in easy and reliable way external products, such CMEMS or coastal ocean data, for research-to-operations applications. Generic Interfaces for NEMO (InterNEMO) allow for 3 main scopes: 1) to access and discover the CMEMS catalogue, including both model and observational data; 2) to manipulate accessed datasets, including coastal ocean data, to extract relevant physical information to use for setting initial/boundary conditions for a new NEMO-based configurations; 3) to prepare NEMO set of upstream files and to validate NEMO solution by using CMEMS observational datasets. InterNEMO implements also technologies to connect a NEMO user to Wekeo DIAS (https://www.wekeo.eu/) for the interoperable accessing and processing of CMEMS data. In this contribution, we present the InterNEMO architecture developed in Python via Jupyter Notebooks, to support the user/researcher to easily discover, design and configure modeling components required by the new NEMO-based configuration. InterNEMO is tested for the Black Sea hydrodynamical model configuration, developed by CMCC in the framework of the Black Sea Monitoring and Forecasting Centre (BS-MFC) for CMEMS a) to show how to access CMEMS observations through Wekeo DIAS and use them to validate numerical solutions and b) to define open boundary conditions from an unstructured grid model configuration based on Shyfem, developed for the Marmara Sea.
A combined model approach for debris-flow impact forces
Authors: Reider Lukas , Fuchs Anna-Lisa , Dankwerth Lisa , Wernhart Susanna , Kaitna Roland , Nagl Georg , Proske Dirk , Scheidl Christian
Published: March 2021

For the design of mitigation measures knowledge of debris-flow impact forces, usually estimated based on hydrostatic, hydrodynamic, or combined approaches, is essential. As these approaches are based on Newtonian fluids, they must be adjusted by empirical correction factors to account for the solid-fluid nature of debris flows. The values for the correction factors shown in the literature vary over a wide range and several studies showed a clear dependence with the Froude regime of debris flows.

To better understand the correction factors and to be able to calculate them using parameters that describe the flow behaviour a total of 32 experiments were conducted in the course of the project “Debris flow impact forces on bridge super structures (DEFSUP)”, funded by the Austrian Science Fund (FWF). Two different material compositions, different water contents as well as a total impact and a bypassing of the measuring block were tested.

The experimental setup designed within the project consists of a 4 m long semi-circular channel with a diameter of 300 mm and an inclination of 20°. The material is released from a rectangular reservoir in a dam-break scenario and accelerated with zero roughness on a length of 1.2 m and transferred to the semi-circle profile. The subsequently introduced roughness with a grain diameter of 1-2 mm generates a stationary phenomenological debris flow until it hits the measuring setup. With a starting volume of 50 kg, flow heights between 8 and 12 cm and velocities from 0.8 to 2.2 m/s were achieved according to the material composition and different water content. With these different mixtures a Froude-range from 0.6 to 3.6 was covered. In addition, normal stresses and pore water pressures were measured at the exact same point.

A detailed analysis of the measured impact forces together with the above mentioned measured parameters showed that the hydrodynamic correction factor is a constant mainly corresponding to the liquification ratio of the debris-flow mixture. Hence, the hydrodynamic correction factor can be regarded as a drag coefficient and seems to depend mainly on the internal friction of the flowing medium. At low Froude numbers measured impact forces exceed even a full momentum transfer if the mean bulk density is used for the calculation. This indicates that the impact forces can no longer be described by the hydrodynamic approach alone. For this reason, an additional pressure term based on a hydrostatic approach is considered in the combined concept. This additional pressure term depends on the dynamics of flow (Froude number) and can be modelled via a dynamic earth pressure coefficient.

The findings from these experiments contribute to a better prediction of debris-flows impact forces in terms of their material composition and flow behaviour.
Methods of modeling the polar low development 
Authors: Kuznetsova Alexandra , Dosaev Alexander , Rusakov Nikita , Poplavsky Evgeny , Troitskaya Yuliya
Published: March 2021

The ice cover decrease in the Arctic in the past decade has led to polar hurricanes (polar lows) occurring along the entire Northern Sea Route. Wind speeds of these hurricanes reach 35-40 m / s. Over the past 20 years, significant progress in predicting storm trajectories has been achieved, while the quality of forecasting their intensity is still poor. This is due to the fact that the intensity (maximum wind speed and minimum pressure) is determined by the interaction of the atmosphere and the ocean, and at high wind speeds it has significant uncertainty, especially for the smallest-scale processes: splashes, wave collapses and foam bubbles [1].

Numerical modeling of the polar low development was carried out within the framework of the WRF model [2] in order to develop methods for modeling such extreme events. The water area of the Barents Sea was considered, where a large number of polar hurricanes were observed. Among the identified polar hurricanes [3], a hurricane that took place on 02/05/2009 and was observed at coordinates 69º N, 40º E was chosen. Several approaches were considered to simulate the weather conditions in the studied area of the Barents Sea in the presence of a polar hurricane. The WRF model simulation with the CFSR reanalysis was carried out. The configuration of the model consisted in using, first, the well-proven technique of Large Eddy Simulation (LES) modeling of the planetary boundary layer (PBL). Secondly, the simulation was performed using the WRF add-in for the polar region, Polar WRF [4]. The comparison of the approaches is made. The mechanism of intensification of the atmospheric vortex is considered whether it is baroclinic shear, heat fluxes on the surface or outcome of latent heat during condensation.

This work was supported by a RFBR grant № 18-05-60299.

References

1. Troitskaya, Yu, et al. "Bag-breakup fragmentation as the dominant mechanism of sea-spray production in high winds." Scientific reports7.1 (2017): 1-4.
2. A Description of the Advanced Research WRF Version 3 / W. C. Skamarock, J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, M. G. Duda, X.-Y. Huang, W. Wang, J. G. Powers // NCAR TECHNICAL NOTE. - 2008. - №NCAR/TN–475+STR. - С. 113 pp.
3. Noer, G., & Lien, T. (2010). Dates and Positions of Polar lows over the Nordic Seas between 2000 and 2010. Norwegian Meteorological Institute Rep.
4. Hines, Keith M., et al. "Development and testing of Polar WRF. Part III: Arctic land." Journal of Climate24.1 (2011): 26-48.
A Dilatant, Two-Phase Debris Flow Model for Hazard Mitigation
Authors: Meyrat Guillaume
Published: March 2021

Guillaume Meyrat, Brian McArdell, Ksenyia Ivanova, Perry Bartelt

WSL Institute for Forest, Snow and Landscape Research, 8903 Birmensdorf, Switzerland

 

Keywords: Debris flows, multi-phase models, dilatancy, shear stress, density distribution

 

To implement an accurate numerical tool to simulate debris flow hazard is a longstanding goal of natural hazard research and engineering. In Switzerland the application of numerical debris flow models has, however, been hampered by many practical and theoretical difficulties. One practical problem is to define realistic initial conditions for hazard scenarios that involve both the rocky (granular solid) and muddy (fluid) material. Still another practical problem is to model debris flow growth by entrainment [1]. These problems are compounded by theoretical uncertainties regarding the rheological behavior of multi-phase flows. Recent analysis of debris flow measurements at the Swiss Illgraben test-site [2] (shear and normal stresses, debris flow height) show that the shear force, and therefore the entire debris flow behavior, is largely influenced by the debris flow composition, i.e. the amount of solid particle and muddy fluid at any specific location within the debris flow body (front, tail, etc.). The debris flow composition is, in turn, determined by the initial and entrainment conditions for a specific event. As a consequence, we have concluded that the very first step to construct a robust numerical model is to accurately predict the space and time evolution of the solid/fluid flow composition for any set of initial and boundary conditions. To this aim, we have developed a two-phase dilatant debris flow model [3, 4, 5] that is based on the idea that the dispersion of solid material in fluid phase can change over time. The model is thus able to predict different flow compositions (rocky fronts, watery tails), using shallow-water type mass, momentum and energy conservation equations. This helps to predict when the solid phase deposits, and when muddy fluid washes and channel outbreaks in the runout zone can occur. The parameters controlling the evolution of debris flow density and saturation have been derived by direct comparison to the full-scale measurements performed at the Illgraben test site.

 

References

 

 
Chemical interactions between ship-originated air pollutants and ocean-emitted halogens
Authors: Li Qinyi , Badia Alba , Fernandez Rafael P. , Mahajan Anoop S. , López-Noreña Ana Isabel , Zhang Yan , Wang Shanshan , Puliafito Enrique , Cuevas Carlos A. , Saiz-Lopez Alfonso
Published: March 2021

Ocean-going ships supply products from one region to another and contribute to the world’s economy. Ship exhaust contains many air pollutants and results in significant changes in marine atmospheric composition. The role of Reactive Halogen Species (RHS) in the troposphere has received increasing recognition and oceans are the largest contributors to their atmospheric burden. However, the impact of shipping emissions on RHS and that of RHS on ship-originated air pollutants have not been studied in detail. Here, an updated WRF-Chem model is utilized to explore the chemical interactions between ship emissions and oceanic RHS over the East Asia seas in summer. The emissions and resulting chemical transformations from shipping activities increase the level of NO and NO2 at the surface, increase O3 in the South China Sea, but decrease O3 in the East China Sea. Such changes in pollutants result in remarkable changes in the levels of RHS as well as in their partitioning. The abundant RHS, in turn, reshape the loadings of air pollutants and those of the oxidants with marked patterns along the ship tracks. We, therefore, suggest that these important chemical interactions of ship-originated emissions with RHS should be considered in the environmental policy assessments of the role of shipping emissions in air quality and climate.