bluuebunny/crossref_metadata_2025 huggingface dataset:
Subsurface fluid migration associated with feeding systems of mud volcanoes in Northwestern Caucasus, results of passive seismic studies
Authors: Puzich Irina , Sobisevich Alexey , Dudarov Zalim
Published: March 2021

The results of passive seismic studies of subsurface fluid transport systems associated with mud volcanic phenomena in Northwestern Caucasus and the Taman mud-volcanic province are presented. Comparative analysis of results of geophysical cross-sections featuring the deep subsurface structures of several mud volcanoes obtained by means of passive microseismic sounding approach with respect to previous studies has demonstrated advantages of the ambient noise seismic prospecting. It has been shown that subvertical pathways of hydrocarbon migration and so feeding systems of mud volcanoes represent nearly-ideal case of local geological heterogeneities affecting the amplitudes of low-frequency microseismic noise. The analysis of the results was performed with respect to available geological as well as geomorphological data. At the same tine, results of past active seismic experiments with controlled vibroseismic sources were reanalyzed and followed by mathematical modeling of processes of hydrodynamic outflow under various mechanisms of mud volcanic eruptions. For several mud volcanoes there were outlined three-dimensional subvertical feeding structures in sedimentary layers and deeper in the crust, responsible for fluid migration and eruptive activity. Specific features of volcanic products (gas components and mineral inclusions in breccia) were analyzed with respect to the new geophysical data obtained.
Mining Contamination Disrupts Successional Change in Salt Marshes
Authors: Smillie Chris
Published: March 2021

Salt marshes can generally be considered as sinks for metals. Research into salt marshes in Cornwall, UK suggests those estuaries heavily impacted by mining contamination are characterised by a less diverse vegetation compared with a significantly less-polluted site. Assessment using the National Vegetation Classification on the mid-marsh confirmed an Armeria maritima-dominated community was to be found in the most metal-enriched salt marsh of Restronguet Creek. However, this plant was co-dominant with Plantago maritima in the moderately contaminated marsh of Lelant and not present at all in the Camel, which has been subject to limited mining related contamination. Using canonical correspondence analysis, vegetation abundance data was compared with geochemical variables within the sediment. Metals were studied using extractions to signal bioavailability. P. maritima was not associated with the very high metal levels found in Restronguet Creek. A. maritima, had some association with soluble copper and was closer to the bulk of metals than P. maritima. As tolerance to adverse conditions and competitiveness are mutually exclusive, A. maritima, therefore, exists in a successional relationship with P. maritima. A. maritima then appears to be outcompeted by P. maritima in marshes with low metal loadings. Moderately high metal content results in a loss of competitiveness by P. maritima allowing A. maritima to co-dominate. In extremely metal-rich estuaries, however, P. maritima is unable to compete, allowing A. maritima to colonize the mid-marsh. Vegetation community may, therefore, be useful as an indicator of the level of metal contamination.
Terrestrial Middle Miocene (Δ47) temperature record reveals highly dynamic climate for the Central Europe
Authors: Krsnik Emilija , Methner Katharina , Löffler Niklas , Kempf Oliver , Fiebig Jens , Mulch Andreas
Published: March 2021

The Miocene experienced both, ice-house periods with continental ice-sheets covering both poles and warm greenhouse conditions with strongly increased global temperature, glacier retreat and sea-level rise. The Mid-Miocene Climatic Optimum (MMCO) is the most pronounced warming event in the last 24 Ma, standing out in a time of protracted cooling. The MMCO is marked by a period of intensive global warming between ca. 17 and 15 Ma. The subsequent Mid-Miocene Climate Transition (MMCT), in contrast, was affected by global temperature decline, growth of Antarctic ice sheets, sea level fall and marine biota overturn.

Miocene climate conditions were intensely studied on both, global and regional scales, based on i.a. marine isotope records and continental paleobotanical and mammalian fossil data sets. Despite the dense data sets continental Miocene temperature evolution still remains unclear owing to a large range of inferred temperatures and/or poor age constraints of the associated records.

Here, we present a long-term terrestrial climate record that covers the time interval between ~20 and ~13 Ma and is based on stable (δ18O) and clumped isotope (Δ47) geochemical data. We apply Δ47 thermometry on terrestrial foreland basin sediments to reconstruct the Middle Miocene continental temperature evolution for central Europe. Pedogenic carbonates from well dated fossil soils from several sites in the Northern Alpine Foreland Basin (Switzerland) reveal warm and stable temperatures for the early Miocene (20 – 19 Ma), followed by overall strongly enhanced variability in temperatures with maximum values attained between ca. 17 and 14 Ma. We observe a highly dynamic transition to cooler climates at the end of the MMCO and a subsequent rapid temperature decline of approximately 20°C after 14 Ma during the MMCT. The highly variable temperature patterns during the cooling period coincide with phases of high seasonality in the precipitation pattern as derived from oxygen isotope compositions of soil water.
Evaluation of four coupled climate models in the Amundsen Sea, Antarctica
Authors: Lekakou Kyriaki M. , Webber Ben G.M. , Heywood Karen J. , Stevens David P. , Hyder Patrick
Published: March 2021

The Amundsen Sea glaciers, in West Antarctica, are among the world’s fastest discharges of ice into the ocean. The rapid thinning of these ice shelves can be largely explained by basal melting driven by the ocean. Relatively warm water reaches the continental shelf in the Amundsen Sea and deep bathymetric troughs facilitate warm deep water flow to the base of the ice shelves. However, time sparse observational data, and even poorly known bathymetry, contribute to the difficulty of quantifying the key ocean mechanisms, and their variability, that transport warm water onto the Amundsen Sea continental shelf and guide it southward into the ice shelf cavities. Nonetheless these processes should be represented in the coupled climate models, such as those used for CMIP6, which are being used to project future sea level rise.

Here we leverage recent observational campaigns and gains in process understanding to assess how well four of these models, UKESM1 and the HadGEM-GC3.1 family of models, represent the ocean processes forcing warm water onto the Amundsen Sea continental shelf. The three HadGEM models have the same external forcing but different horizontal resolutions, 1/12, ¼ and 1 degree. The 1 degree resolution UKESM1 is based on HadGEM3.1 but includes atmospheric chemistry, aerosols and marine biogeochemistry. A key finding is the medium resolution (1/4°) HadGEM-GC3.1 model’s inability to allow warm deep water intrusion onto the continental shelf, associated with a strong westward slope current that is not present in the other models. The medium resolution model represents well the annual cycle of sea ice in the Amundsen Sea, but overall has significantly less sea ice around Antarctica, compared with the other models and satellite observations. Despite its low resolution, UKESM1 represents well all the main ocean features, including the shelf-break undercurrent, warm deep water and realistic sea ice. It captures more significant interannual variability, in contrast to the low resolution HadGEM, for which the interannual variability is more suppressed. Of the four models considered here, the best performing models are the 1/12° HadGEM and UKESM1, followed by the low resolution HadGEM model, which reasonably represents warmer deep water on the continental shelf and a shallower mixed layer. The medium resolution HadGEM, despite its better resolution is less realistic than the two low resolution models.
Robustness of projections of European precipitation for seasonal means and seasonal extremes
Authors: Ritzhaupt Nicole , Maraun Douglas
Published: March 2021

We analyze several sets of global and regional climate models (GCMs and RCMs) to investigate how robust climate change signals for seasonal mean and extreme precipitation are. The projections of the regional climate models ENSEMBLES and EURO-CORDEX are used along with projections of their driving global data sets of CMIP3 and CMIP5, respectively. In addition, projections of CMIP6 and the high-resolution HighResMIP global models are used. The projections are used with high emission scenarios (A1B or RCP8.5) depending on availability. To calculate the climate change signals a future period 2071-2100 and a baseline period 1971-2000 is chosen. For comparability and to reduce the uncertainty by the choice of the emission scenario, the climate change signals are normalized by the European mean surface temperature. We make statements of percentage change per degree warming. The analyses are carried out for eight European sub-regions: Alps, British Isles, Iberian Peninsula, France, Mid-Europe, Scandinavia, Mediterranean and Eastern Europe. We define extreme precipitation as the 20-year return values of each season. Regarding mean precipitation the climate change signals are robust across the different data sets. In accordance with previous studies, there is a transition zone between increasing and decreasing signals which is located in southern Europe in winter and more north in summer. This seasonal cycle can be found for all regions. For extreme precipitation, the climate change signals indicating increases in all seasons and regions. Especially in summer, in most regions the RCMs showing a higher increase compared to the GCMs up to a difference of about 5%/K for the ensemble medians. Hence, the signals for extremes are not that robust than for means.

To understand where these differences come from, we are using a precipitation scaling for extremes to investigate the thermodynamic and dynamic contributions. The thermodynamic contribution shows homogeneous increasing signals for Europe. This means the dynamic contribution is the key to understand differences between the model ensembles.

We aim to understand the discrepancy between different lines of evidence and focusing our study in the field of climate information distillation.
Direct Numerical Simulation of  turbulent canopy flow
Authors: Sahoo Ganapati , Bhattacharjee Soumak , Debolsky Andrey , Kadanstev Evgeny , Mortikov Evgeny , Pandit Rahul , Vesala Timo
Published: March 2021

Turbulent flows within and above urban and vegetative canopies in the atmospheric boundary layer have profound implications for a variety of important problems in  agricultural  and urban meteorology, such as the spreading of pollens and pollutants. We study such turbulence via Direct Numerical Simulations (DNSs), by using the code developed in (2019 Mortikov),  in which there is a closed channel between two parallel walls and a canopy of constant areal density profile on the lower wall. We impose periodic boundary conditions in the horizontal directions and a no-slip impenetrable boundary condition in the wall-normal direction. For the canopy, we use different formulations of the Forchheimer drag. We assess the role of the canopy on the turbulent flow. In particular, we show the influence of added drag on the mean profiles, balance equations of the second-order moments, and the local anisotropy of the flow.

We observe that the turbulence transport profile undergoes an abrupt transition at the canopy top and transfer of energy from the roughness sublayer above the canopy to inside the canopy.  
The pressure-strain correlation removes energy from the wall-normal fluctuations, which has the least share of the turbulent kinetic energy and distributes it among the other components in the bulk of the canopy. In the inertial range, within and above the canopy, the energy spectra for the streamwise component is steeper than the spanwise and the wall-normal components and is closer to the Kolmogorov -5/3 spectrum as observed in the eddy covariance measurements in the roughness sublayer (2020 Bhattacharjee).

We thank the DST, CSIR (India), SERC (IISc) for computational resources, the AtMath Collaboration at the University of Helsinki, and ICOS by University of Helsinki for their support. This study was also partially funded by RFBR project number 20-05-00776.

Reference

2019, Mortikov, E. V., Glazunov, A. V., & Lykosov, V. N. Numerical study of plane Couette flow: turbulence statistics and the structure of pressure–strain correlations, Russian Journal of Numerical Analysis and Mathematical Modelling, 34(2), 119-132. doi: https://doi.org/10.1515/rnam-2019-0010.

2020, Bhattacharjee S., Pandit R., Vesala T., Mammarella I., Katul G., and Sahoo G. Anisotropy and multifractal analysis of turbulent velocity and temperature in the roughness sublayer of a forested canopy, arXiv:2010.04194.
Investigating the effects of COVID-19 to crime rates through a geospatial approach: the case of New York, USA
Authors: Tselka Ioanna , Demertzi Isidora Isis , Petropoulos George P.
Published: March 2021

Covid-19 pandemic has led to severe consequences to humanity worldwide. Yet, to our knowledge, little scientific evidence is available exploring the impact of the pandemic on criminality. Thus, it is imperative to examine their relationships spatially to obtain a better understanding of societal characteristics during the pandemic.

This study aims at demonstrating the use of geoinformation in analyzing the spatial patterns between crime properties and Covid-19 spread using as a case study New York City, USA, one of the largest metropolitan cities of the world. To address our objectives, geostatistical analysis and data visualization methods have been implemented in real-world crime data acquired from a web-GIS platform. Our analysis concerns two equal time periods before and after the lockdown implementation.

Results revealed some very interesting patterns spatially between the examined parameters and societal characteristics existing in the study region. The methodological framework presented underlined the added value of geoinformation as a robust and cost-effective approach in examining the impact of the pandemic to the society.

 

Keywords: Covid-19, pandemic, crime rates, geoinformation, New York
Teams Win: The European Datacube Federation
Authors: Baumann Peter
Published: March 2021

Collaboration requires some minimum of common understanding, in the case of Earth data in particular common principles making data interchangeable, comparable, and combinable. Open standards help here; in case of Big Earth Data specifically the OGC/ISO Coverages standard. This unifying framework establishes a common framework in particular for regular and irregular spatio-temporal datacubes. Services grounding on such common understanding have proven more uniform to access and handle, implementing a principle of "minimal surprise" for users visiting different portals while using their favourite clients. Data combination and fusion benefits from canonical metadata allowing automatic alignment, e.g, between 2D DEMs, 3D satellite image time series, 4D atmospheric data, etc.

The EarthServer datacube federation s showing the way towards unleashing in full the potential of pixels for supporting the UN Sustainable Development Goals, local governance, and also businesses. EarthServer is an open, free, transparent, and democratic network of data centers offering dozens of Petabytes of a critical variety, such as radar and optical Copernicus data, atmospheric data, elevation data, and thematic cubes like global sea ice. Data centers like DIASs and CODE-DE, research organizations, companies, and agencies have teamed up in EarthServer. Strictly based on the open OGC standards, an ecosystem of data has been established that is available to users as a single pool, without the need for any coding skills (such as python). A specific unique capability is location-transparency: clients can fire their query against any of the mebers, and the federation nodes will figure out the optimal work distribution irrespective of data location.

The underlying datacube engine, rasdaman, enables all datacube access, analytics, and federation. Query evaluation is optimized automatically applying highly efficient intelligent, rule-based methods in homogeneous and heterogeneous mashups, up to satellite on-board deployments as done in the ORBiDANSe project. Users perceive one single, common information space accessible through a wide spectrum of open-source and proprietary clients.

In our talk we present technology, services, and governance of this unique line-up of data centers. A demo will show distributed datacube fusion live.

 
The Energetic Particle Detector (EPD) Electron-Proton Telescope (EPT) on Solar Orbiter: First Data
Authors: Kollhoff Alexander , Pacheco Daniel , Wimmer-Schweingruber Robert F. , von Forstner Johan , Berger Lars , Eldrum Sandra , Xu Zigong , Heber Bernd , Rodriguez-Pacheco Javier , Ho George ,   EPD team
Published: March 2021

Solar Orbiter’s Energetic Particle Detector (EPD) was commissioned in early 2020 and has since been returning data from the inner heliosphere. Despite the low activity in the current deep and extended solar minimum, EPD has observed a number of solar particle events and numerous other enhancements of energetic particles. As one of the four complementary EPD sensors, the Electron-Proton Telescope (EPT) covers the gap between the high and low particle-energy measurements of HET and STEP. With four double-ended telescopes, EPT is capable of measuring electrons and ions in an energy range of 35-400keV and 45-7000keV respectively, while providing anisotropy information from four different viewing directions.

We will present a first overview of EPT measurements, exhibiting some of the EPT data products which are made available by the European Space Agency (ESA).

In order to provide the community a deep insight into the data, we will go through different aspects of the measurements, including the current status of the intercalibration with the other EPD instruments.
The use of multi-tracer flask-measurements to understand changes in the land-surface processes.
Authors: Kariyathan Theertha , Peters Wouter , Marshall Julia , Bastos Ana , Reichstein Markus
Published: March 2021

Carbon dioxide (CO2) is an important greenhouse gas, and it accounts for about 20% of the present-day anthropogenic greenhouse effect. Atmospheric CO2 is cycled between the terrestrial biosphere and the atmosphere through various land-surface processes and thus links the atmosphere and terrestrial biosphere through positive and negative feedback. Since multiple trace gas elements are linked by common biogeochemical processes, multi-species analysis is useful for reinforcing our understanding and can help in partitioning CO2 fluxes. For example, in the northern hemisphere, CO2 has a distinct seasonal cycle mainly regulated by plant photosynthesis and respiration and it has a distinct negative correlation with the seasonal cycle of the δ13C isotope of CO2, due to a stronger isotopic fractionation associated with terrestrial photosynthesis. Therefore, multi-species flask-data measurements are useful for the long-term analysis of various green-house gases. Here we try to infer the complex interaction between the atmosphere and the terrestrial biosphere by multi-species analysis using atmospheric flask measurement data from different NOAA flask measurement sites across the northern hemisphere.

This study focuses on the long-term changes in the seasonal cycle of CO2 over the northern hemisphere and tries to attribute the observed changes to driving land-surface processes through a combined analysis of the δ13C seasonal cycle. For this we generate metrics of different parameters of the CO2 and δ13C seasonal cycle like the seasonal cycle amplitude given by the peak-to-peak difference of the cycle (indicative of the amount of CO2 taken up by terrestrial uptake),  the intensity of plant productivity inferred from the slope of the seasonal cycle during the growing season , length of growing season and the start of the growing season. We analyze the inter-relation between these metrics and how they change across latitude and over time. We hypothesize that the CO2 seasonal cycle amplitude is controlled both by the intensity of plant productivity and period of the active growing season and that the timing of the growing season can affect the intensity of plant productivity. We then quantify these relationships, including their variation over time and latitudes and describe the effects of an earlier start of the growing season on the intensity of plant productivity and the CO2 uptake by plants.
Seasonal predictability of Mediterranean Weather Regimes in the Copernicus C3S Systems
Authors: Giuntoli Ignazio , Fabiano Federico , Corti Susanna
Published: March 2021

Seasonal predictions in the Mediterranean region have relevant socio-economic implications, especially in the context of a changing climate. To date, sources of predictability have not been sufficiently investigated at the seasonal scale in this region. To fill this gap, we explore sources of predictability using a weather regimes (WRs) framework. The role of WRs in influencing regional weather patterns in the climate state has generated interest in assessing the ability of climate models to reproduce them.

We identify four Mediterranean WRs for the winter (DJF) season and explore their sources of predictability looking at teleconnections with sea surface
temperature (SST). In particular, we assess how SST anomalies affect the WRs frequencies during winter focussing on the two WRs that are associated with the teleconnections in which the signal is more intense: the Meridional and the Anticyclonic regimes . These sources of predictability are sought in five state-of-the-art seasonal forecasting systems included in the Copernicus Climate Change Services (C3S) suite finding a weaker signal but an overall good agreement with reanalysis data. Finally, we assess the ability of the C3S models in reproducing the reanalysis data WRs frequencies finding that their moderate skill improves during ENSO intense years, indicating that this teleconnection is well reproduced by the models and yields improved predictability in the Mediterranean region.
Chemical-physical constraints of the 2015 eruptive activity of Mt. Etna: new insights from thermo-barometry and geochemistry of olivine-hosted melt inclusions
Authors: Giacomoni Pier Paolo , Casetta Federico , Valenti Virginia , Ferlito Carmelo , Lanzafame Gabriele , Nazzari Manuela
Published: March 2021

The concomitant activation off all four summit craters of Mt. Etna during the December 2015 eruptive event allow us to investigate the chemical-physical crystallization conditions and magma dynamics in the shallower portion of the open-conduit feeding system. In this study, we discuss new petrological, geochemical and thermo-barometric data as well as the composition of major element and volatile content (H2O, CO2, F, Cl and S) of olivine-hosted melt inclusions from the explosive and effusive products emitted during the December 2015 eruptive event.

Results and rhyolite-MELTS thermodynamic modelling of mineral phase stability highlight the relatively shallow crystal equilibrium depth prior to the eruption ranging from 400-500 MPa for Central Crater and North East Crater, up to 200 MPa below the New South East Crater. The study of high-pressure and high-temperature homogenized olivine-hosted melt inclusions allowed us to identify the composition of the almost primary alkali-basalt magma (11.8 wt% MgO) containing up to 4.9 wt% and 8151 ppm of H2O and CO2 respectively. The results, together with those already reported for the previous paroxystic events of the 2011-2012 (Giacomoni et al., 2018), reinforce the model of a vertically extended feeding system and highlight that the activity at the New South East Crater was fed by a magma residing at significant shallower depth with respect to Central Craters and North East Crater, although all conduits are fed by a common deep (P = 530-440 MPa) basic magmatic refilling. Plagioclase stability model and dissolution and resorption textures confirm its dependence on H2O content, thus suggesting that further studies on the effect that flushing from fluids with different H2O/CO2 ratio are needed in order to understand the eruption triggering mechanisms of paroxystic fountaining.

 

References

Giacomoni P., Coltorti M., Mollo S., Ferlito C., Braiato M., Scarlato P. 2018. The 2011-2012 paroxysmal eruptions at Mt. Etna volcano: Insights on the vertically zoned plumbing system. JVGR 349, 370-391.
Holocene vegetation, climate and human impact in steppes around Lake Sevan (Armenia) based on a multiproxy approach: Pollen, NPPs and brGDGTs
Authors: Robles Mary , Peyron Odile , Brugiapaglia Elisabetta , Ménot Guillemette , Dugerdil Lucas , Ollivier Vincent , Develle Anne-Lise , Tozalakyan Petros , Meliksetian Khachatur , Sahakyan Kristina , Sahakyan Lilit , Perello Bérengère , Badalyan Ruben , Colombié Claude , Sébastien Joannin
Published: March 2021

In the Caucasus Mountains, the role of human influences and climate changes on steppes expansion over the Holocene is still discussed because this region is poorly documented. This study investigates (1) modern pollen-vegetation relationships in Armenia and (2) changes in vegetation, human activity and climate in the Holocene record of Vanevan peat (south-eastern shore of Lake Sevan) located in Armenia. The last 9700 years are recorded in the Vanevan core. We used a multiproxy approach including XRF, Pollen, Non-Pollen Palynomorphs (NPPs) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct changes in vegetation, human impact and climate. The combination of these proxies is innovative and aims to distinguish the impact of human activities and climate change on vegetation. Modern pollen assemblages from semi-desert/steppe regions of Armenia show an abundance of Chenopodiaceae while meadows steppes, subalpine and alpine meadows are dominated by Poaceae. The Holocene vegetation at Vanevan is characterized by steppes dominated by Poaceae, Artemisia and Chenopodiaceae. However, several arboreal taxa, such as Quercus, Betula, Carpinus betulus and Ulmus, are more developed on slopes between 8600 and 5100 cal BP. Regarding the human impact, the presence of agriculture is attested since 5200 cal BP, largely increases during the last 2000 years cal BP (high percentages of Cerealia-type pollen) and correlates with the occupation periods reported in archeological studies. Palaeoclimate changes at Vanevan are estimated from (1) water level changes (2) temperature reconstructions based on brGDGTs (3) climate reconstructions based on pollen (through a multi-method approach: Modern Analogue Technique, Weighted Averaging Partial Least Squares regression, Random Forest, and Boosted Regression Trees). Climate reconstructions based on pollen and brGDGTs are rare and the multi-method approach using pollen data is innovative in the region. The results of Vanevan give evidence of high temperatures from 7900 to 5100 cal BP and arid events at 6000, 5000-4500 and 4200 cal BP, in agreement with other regional records.
Spatial and temporal assessment of Snow drought characteristic for 1981 to 2020 on Urmia lake catchment scale
Authors: Habibi Maral , Schöner Wolfgang , Babaeian Iman
Published: March 2021

Snow plays a significant role in surface runoff, groundwater resources, and as an important temporary reservoir for winter precipitation. On the other hand, extreme floods can arise when high melt rates in catchments zone combine with torrential rain at the same time, therefore snowmelt quantities are important for the management of lakes.

This study aims at investigating snow drought characteristics in the catchment area of Lake Urmia, which has recently been faced with the issue of drought and declining water levels. To provide an overview of drought intensity for the last 40 years 1981-2020, the Standardized Snow Melt and Rain Index (SMRI), which accounts for rain and snowmelt deficits, was applied and spatial variations of snow drought were assessed. The index was used in drought analysis based on the ERA5 dataset for the whole study area under three-time scales including the 3-, 6- and 12-month. After determining the dry and wet periods, historical characteristics of droughts were identified, and spatial distribution maps of droughts were plotted.

Results show that during the last years, snow drought events were more frequent, severe, and affected a larger area which shows a spatial spread of drought events. According to the snow index results, most extreme events have happened in the Zarine Rud and Simine Rud sub-catchments which play a key role in increasing the groundwater resources of the Basin. With proper management, these resources can be properly used for lake revitalization.

 

Keywords: Snow droughts, SMRI, Drought characteristics, Urmia lake, Climate extreme

 
Urban-PLUMBER model evaluation project: initial results
Authors: Lipson Mathew , Grimmond Sue , Best Martin ,   Urban-PLUMBER team
Published: March 2021

We present initial results of the Urban-PLUMBER international model evaluation project. This project assesses the performance of land surface models used in meteorological simulations of urban areas. Phase 1 included 24 models of varying complexity, from simple slab models through to multi-layer urban canopy models.

54 model output variables are requested, including primary surface energy fluxes, anthropogenic heat and moisture fluxes, soil variables, albedo, canopy and building air temperatures. This rich dataset is used to both compare model outputs with observations and to understand factors contributing to model performance.

The project involved a number of other innovations including:

An online portal (modelevaluation.org) is used to distribute site data and accept submissions.

Upon submission to the portal participants are provided with variable near-instant compliance checks and analyses allowing participants to make corrections if required.

A ten-year ERA5-derived spin up which overcomes the typically short period of urban flux tower observations and allows the entire observed period to be used in analyses.

Testing models alongside simple empirical benchmarks (e.g. out-of-sample linear regression of turbulent fluxes on shortwave radiation) to assess if input information is used effectively.

We also discuss the initial stages of Phase 2 which involves testing models at many urban sites. From the known global urban flux tower observations, following assessment, 25 are selected to capture a range of urban characteristics and climates. Surface characteristics are gathered, observations quality controlled and prepended with ten years of bias corrected ERA5 meteorological data for spinup. This new standardised urban flux tower dataset will become a valuable tool in future urban modelling projects.
Characterization of the resilience and variability of vegetation during the Holocene using a large database of pollen data
Authors: Hébert Raphael , Li Chenzhi , Laepple Thomas , Herzschuh Ulrike
Published: March 2021

Global climatic changes which are expected in the 21st century are likely to create unparalleled disturbances on vegetation. In addition, human activities also increase the risk of fire disturbances and insect epidemies. We investigate the resilience of different biomes by examining their behaviour during the Holocene using a taxonomically harmonized and temporally standardized global fossil pollen datasets,synthesized from 2821 palynological records from the Neotoma Paleoecology Database and additional literature. Specifically, we study the composition variability on millennial time-scale and timescale-dependant scaling of variability from centennial to multi-millennial timescales. A principal component analysis was performed in order to characterize the principal modes of variability of the pollen assemblages. We find coherent regional signals of vegetation variability and scaling of variability from the pollen assemblages, indicating significant millennial scale variability which can be related to vegetation taxa and climates. Particularly, we observe more stability in North America and Northern Europe in areas dominated by boreal forest and deciduous forests. This may be linked to the greater stability of forest ecosystems and also a more stable climate over these areas which may be the result of stabilizing feedbacks. We find that diversity plays a key role in vegetation composition and that more diverse regions allow for greater variability. 

 

 
Robust extreme value analysis by semiparametric modelling of the entire distribution range
Authors: Kwasniok Frank
Published: March 2021

Traditional extreme value analysis based on the generalised extreme value (GEV) or the generalised Pareto distribution (GPD) suffers from two drawbacks: (i) Both methods are wasteful of data as only block maxima or exceedances over a high threshold are used and the bulk of the data is disregarded, resulting in a large uncertainty in the tail inference. (ii) In the peak-over-threshold approach the choice of the threshold is often difficult in practice as there are no really objective underlying criteria.
Here, two approaches based on maximum likelihood estimation are introduced which simultaneously model the whole distribution range and thus constrain the tail inference by information from the bulk data. Firstly, the bulk matching method models the bulk of the distribution with a flexible exponential family model and the tail with a GPD. The two distributions are linked together at the threshold with appropriate matching conditions. The threshold can be estimated in an outer loop also based on the likelihood function. Secondly, in the extended generalised Pareto distribution (EGPD) model for non-negative variables the whole distribution is modelled with a GPD overlaid with a transition probability density which is again represented by an exponential family. Appropriate conditions ensure that the model is in accordance with extreme value theory both for the lower and upper tail of the distribution. The methods are successfully exemplified on simulated data as well as wind speed and precipitation data.
Assessing the impact of cover crop as a GHG mitigation solution at intra-field scale using the AgriCarbon-EO tool
Authors: Wijmer Taeken , Al Bitar Ahmad , Fieuzal Remy , Arnaud Ludovic , Pique Gaetan , Ceschia Eric
Published: March 2021

Increasing soil carbon stocks has been identified as a major climate change mitigation solution. As a consequence, an objective of 4/1000 yearly increment in soil carbon stocks has been proposed at the COP21.  Sustainable agriculture provides several solutions to meet this objective and among those solutions, the implementation of cover crops has been identified as most efficient. Currently, a comprehensive modeling tool that takes into account the major bio-geophysical processes with associated uncertainties, while assimilating frequent high-resolution observations at large scale could allow accounting for the effect of cover crops on the carbon budget in a realistic way. In this study, we quantify the components of the carbon budget at high resolution and we analyse the effect of cover crops. Computations are based on the newly developed AgriCarbon-EO tool which assimilates full resolution (10-20m) Sentinel-2 optical data into a radiative transfer model (PROSAIL), and a crop model (SAFYE-CO2). The assimilation scheme is based on a Bayesian approach which provides the retrieved biogeophysical variables with their associated uncertainties. Uncertainties are essential when determining the carbon stocks. For instance, the future European Common Agricultural Practice (CAP) may take into consideration the uncertainty of the determination of the soil carbon stocks changes in the evaluation of the subsidies. The main inputs of the computations are weather data, soil texture maps, crop maps and surface reflectances. The Sentinel-2 Leaf Area Index (LAI) are obtained from those Sentinel-2 surface reflectance by inverting the PROSAIL model. These are then assimilated into the SAFY_CO2 model to determine the carbon budget components. To validate our approach, we implemented the AgriCarbon-EO tool over a set of plots in south-western France over which we dispose of biomass measurements for cover crops in wheat/cover crop/maize rotations for 2017-2018 and 2019-2020 agricultural seasons. Also, the CO2 fluxes are validated against eddy covariance flux measurements in the same context. Our study shows that the cover crops allow on average 250gC/m² of organic carbon with a high spatial heterogeneity. This has important implications regarding the dynamic of carbon storage in agronomic soils and demonstrates the importance of high-resolution agronomic modeling.
Elemental concentrations in two stalagmites from B7-Cave indicating environmental changes during the Holocene
Authors: Riechelmann Dana Felicitas Christine , Jochum Klaus Peter , Scholz Denis
Published: March 2021

Two stalagmites (B7-1 and B7-7) were sampled from B7-Cave in western Germany. B7-Cave is located very closely (100 m) to the extensively investigated Bunker Cave. Both B7-Cave stalagmites were previously dated and analysed for stable carbon and oxygen isotope composition at low resolution by Niggemann et al. (2003). Both stalagmites were now redated more precisely using the MC-ICP-MS methodology at the Max Planck Institute for Chemistry, Mainz, and Mainz University. Furthermore, the elemental concentrations of Mg, Sr, Ba, Al, P, Y, Zn, Th, and U were determined by laser ablation ICP-MS (MPIC Mainz) at high resolution. Additionally, thin sections of both stalagmites were anaylsed for their calcite fabrics and detection of detrital layers.

The dating showed a growth phase from 10.9 to 6.6 ka BP for stalagmite B7-1 and three growth phases for stalagmite B7-7 from 11.2 to 6.3 ka BP, 3.2 to 2.9 ka BP, and 1.3 to 1.2 ka BP. This is improved to the dating from Niggemmann et al. (2003), who only detected one hiatus in stalagmite B7-7. Stalagmites B7-1 and B7-7 have a substantial overlapping period. During this period, both stalagmites contain frequent detrital layers, which probably represent short growth stops. However, these growth stops are too short and contain too much detrital material to resolve their timing and duration by 230Th/U dating.

Phosphorus, Y, and Zn are correlated in both stalagmites and during all growth phases. These three elements are interpreted as proxies for vegetation activity. Magnesium, Sr, and Ba are difficult to interpret due to several factors potentially influencing them, such as prior calcite precipitation, growth rate, and soil processes. Furthermore, the detrital layers in stalagmite B7-1 and the oldest growth phase of B7-7 are indicated by high Al concentrations.

 

 

Niggemann, S., Mangini, A., Richter, D. K., Wurth, G., 2003. A paleoclimate record of the last 17,600 years in stalagmites from the B7 cave, Sauerland, Germany. Quaternary Science Reviews 22, 555-567.
MMS observations of explosive filamentary current within two adjacent ion scale flux ropes
Authors: Xiao Yuchen , Yao Shutao , Guo Ruilong , Shi Quanqi , Tian Anmin , Bai Shichen , Liu Ji
Published: March 2021

Flux ropes have attracted extensive attention due to their importance in studying instantaneous magnetic reconnection over the past years. Recently, with the improvement of high spatio-temporal resolution measurements, kinetic-scale flux ropes have been detected. However, their generation and energy energization are still unclear. In this study, electron-scale filamentary currents within two adjacent ion scale flux ropes are observed using MMS data. We find that:

1. Intense and explosive filamentary currents in parallel and perpendicular directions are found inside the flux ropes.

2. The electron pitch angle distribution appears "X" like shape, and could be caused by the electron acceleration.

3. The filamentary current appears in the center of the "X" distribution.

The filamentary currents are important and are considered to be the evidence of secondary reconnection [Wang et al., 2020]. The observations in our study are important to reveal the particle acceleration and energy dissipation in magnetic reconnection.
Late Quaternary Climate Variability Constrains River Incision and Aggradation in the Spiti Valley, Western Himalaya
Authors: Bookhagen Bodo , Strecker Manfred , Niedermann Samuel , Thiede Rasmus
Published: March 2021

The intensity of the Asian summer-monsoon circulation varies over decadal to millennial timescales and impacts surface processes, terrestrial environments, and marine sediment records. The duration and magnitude of this climatic forcing on erosion processes varies, depending on duration and intensity of the climatic events, as well as on the tectonic and geomorphologic preconditioning of the landscape. In this study, we focus on a region in the transition zone between continuous and episodic monsoon impacts: the Spiti River, the largest tributary (12x103 km2 ) to the Sutlej River in the western Himalaya. The river valley is located in the northern lee of the Himalayan orographic barrier in a presently arid environment. The Spiti Valley has received significant precipitation during intensified monsoon periods during the late Pleistocene and Holocene and thus constitutes an ideal location to evaluate effects of episodic moisture transport into an arid, high-relief mountainous region.

Here we present 21 new surface-exposure ages of fluvial-fill terraces combined with previously published data to quantify temporal patterns in river incision and erosion rates. Our data include catchment-wide erosion rates and in-situ cosmogenic nuclide ages derived from 10Be, 26Al, and 21Ne and document that terrace formation (i.e., terrace abandonment) occurred during intensified monsoon phases at ∼100 ka, ∼65 ka, ∼43 ka, and ∼12 ka, although dating uncertainties prevent the calculation of exact correlation between monsoonal strength and terrace formation. We show that incision into Late Pleistocene valley fills that integrate over several cut-and-fill cycles at 105 y are comparable to exhumation rates determined from thermochronology studies averaging over 10^6 y in that area. We argue that the limiting factor for sediment removal and river incision on shorter, millennial timescales is due to large bedrock landslides that impounded the river network and formed transient sedimentary basins lasting for 103 -104 years. We suggest a feedback process between sediment removal and landsliding, where large landsliding predominantly occurs when the transiently-stored valley fills have been carved out, leading to exposed valley bottoms, bedrock erosion, lateral scouring of rivers, and ultimately to the over-steepening of hillslopes. We suggest that Late Quaternary climatic variability is the main forcing factor in filling and evacuating transiently stored sediments in high mountain ranges and thus plays a direct role in controlling bedrock incision.
Innovative on-site infrasound metrology conducted in 2019 and 2020
Authors: denis stephane , vincent paul , Guillaume Rouille
Published: March 2021

In order to improve the confidence in the results of measurements carried out in the field, on-site metrology is a key step. With the medium-term objective of being able to deploy a portable metrology system on different infrasound stations, CEA-DAM has tested an innovative system for calibrating its infrasound sensors. The first tests were conducted in November 2019 and September 2020 as part of the installation and certification of the IMS IS25 infrasound station in Guadeloupe. A total of 20 microbarometers were qualified on site.
We present the equipments deployed, the methods used and the results of the measurements carried out. It appears that the preliminary results show a very good correspondence between the measurements performed in the field, under particular environmental conditions, and the measurements performed in the metrology laboratory. The method will be confronted to the metrology community within the framework of the European Infra-AUV project in 2022.
Use of Sentinel-2A/B satellites and Google Earth Engine for monitoring estuarine systems: a study case in the Western Mediterranean
Authors: Roca Mora Mar , Navarro Almendros Gabriel , García Sanabria Javier , Caballero de Frutos Isabel
Published: March 2021

Coastal areas are being rapidly transformed in the last 50 years due to anthropogenic causes. New infrastructures and intensive activities have changed the natural behaviour of coastal ecosystems, promoting problems related to water quality, eutrophication and coastal erosion. This situation increases the vulnerability to climate change, requiring important efforts in monitoring and defining protocols for optimizing operational decision-making and strategic management. Remote sensing techniques are becoming a key tool for coastal mapping in terms of resolution, effectiveness and cost reduction. In the last decade, the European Commission launched the Copernicus programme for Earth Observation as a way of improving coastal monitoring with higher resolution. Sentinel-2A/B twin satellites are part of this free and open policy programme available since 2015, but atmospheric corrections or cloud cover are still challenges to face. In order to process this data, cloud computing platforms such as Google Earth Engine (GEE) have revolutionized the way satellite images are processed, without the need to download and store local data. The present study aimed at developing a GEE-based technique for selecting cloud-free Sentinel-2 Level-2A images in the Guadiaro estuary in the Western Mediterranean (Spain) during the last four years (2017-2020).  It has been used to analyse the evolution of the sand bar and to identify hotspots in its sedimentary variation along the coast, at 10 m and 5 days spatial and temporal resolution respectively. NDWI index was evaluated using 0.05 to 0.15 threshold, revealing 0.1 as the best threshold to be used for land/water mapping, easily incorporated in the GEE platform. In addition to Sentinel-2 potential, this study also demonstrates the power of GEE, computing more than 400 images for statistical analysis in terms of seconds, which enabled the automatic filtering method developed for cloud-free images selection with a 95% of effectiveness. Moreover, ACOLITE processor has been used on Sentinel-2 L1A images for atmospheric and sunglint correction to generate Level-2 data and for analysing turbidity and water quality patterns during extreme rainfall events, providing key information as early-warning indicators development. This improvement will be useful for near future implementation of remote sensing applications for coastal managers, ensuring a continuous and detailed monitoring and helping to support an ecosystem-based approach for coastal areas.