bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional traits of hydrolytic enzymes and visualized enzymatic activity in the rhizosphere gradients of Zea mays L. 
Authors: Ghaderi Negar , Guber Andrey , Khosrozadeh Sajedeh , Guliyev Vusal , Blagodatskaya Evgenia
Published: March 2021

Alive plants and soil microorganisms are the influential sources of extracellular enzymes facilitating decomposition of polymeric organic compounds. Enzyme activities are especially intensive and spatially heterogeneous in the rhizosphere, where microorganisms are stimulated by rhizodeposition. Two-dimensional activity distribution of hydrolytic enzymes participating in transformation of soil organics in the distance gradients from the root can be visualized under UV light by zymography - by placing a fluorogenic substrate-saturated membrane on the soil surface. Functional traits of enzymes can be co-localized with spatial distribution of enzymatic activity by precise micro-sampling based on zymography. We used rhizobox experiment to visualize activity of β-glucosidase, leucine aminopeptidase, and phosphatase in the rhizosphere of wild type and root hairless mutant of Zea mays L. cultivated for 3 weeks. After precise micro-sampling, we determined kinetic parameters of enzymes: max potential activity and affinity to substrate in the rhizosphere gradients. Finally, we compared the correspondence of enzymatic activity determined by zymography and by kinetic approach. This work was conducted within the framework of the priority program 2089, funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project number: 403664478. Seeds of the maize were provided by Caroline Marcon and Frank Hochholdinger (University of Bonn).

Keywords: zymography, enzyme kinetic, maize, rhizosphere gradients
Defining a cold pool-resolving scale for numerical simulations of convective self-organisation
Authors: Fiévet Romain , Meyer Bettina , Haerter Jan Olaf
Published: March 2021

Spontaneous aggregation of clouds is a puzzling phenomenon observed in field studies [Holloway et al. (2017)] and idealized simulations alike [Held et al. (1993), Bretherton et al. (2005)]. With its relevance to climate sensitivity and extreme events, aggregation continues to be heavily studied, [Wing et al., 2017 for a review], with radiative-convective feedbacks emerging as main drivers of simulated convective self-aggregation (CSA) [Mueller & Bony (2015)].

In state-of-the art cloud-resolving models, CSA finds itself consistently hampered by finer horizontal resolutions [Muller & Held (2012), Yanase et al. (2020)]. This feature was ascribed to the effect of cold pool (CP) gust fronts in opposing the positive moisture feedback underlying CSA [Jeevanjee & Romps (2013)]. In contrast, recent numerical experiments [Haerter et al. (2020)] with diurnally oscillating surface temperature highlights an orthogonal effect: stronger CPs, driven by small-scale density gradients, promote cloud field self-organization into mesoscale convective systems (MCS). Interestingly, this upscale growth, which we here term diurnal self-organisation (DSO), differs from classical CSA as it is driven by CPs rather than large-scale radiative imbalances. In stark contrast to CSA, strengthening CPs promotes this organization effect.

Hence, numerical simulations of CSA and DSO should go beyond the typical cloud-resolving paradigm and achieve cold pool-resolving capabilities. The current study systematically examines the impact of model resolution on CP effects. First, numerical convergence is probed in a 12km x 20km laterally periodic domain where a single CP propagates and self-collides at the domain's edges. As the spatial resolution is stepwise increased from 250 to 25m, it is shown that the initially coarsely resolved density current dissipates and collision and updraft effects are weak. As finer resolution is approached, we identify a cold pool resolving resolution D, which is deemed satisfactory for propagation and collision properties. Second, convergence for a (250km)2 domain under a diurnal radiative cycle is assessed at various spatial resolutions, including the scale D. This mesoscale configuration allows us to quantify the impact of resolution of cold pool dynamics on DSO.

Together, this work systematically lays out the numerical requirements to study mesoscale clustering by means of explicit numerical simulations.
Accretion-controlled forearc deformation pulses recorded by high-pressure paleo-accretionary wedges: the example of the Hellenic subduction zone
Authors: Menant Armel , Oncken Onno , Glodny Johannes , Angiboust Samuel , Jolivet Laurent , Augier Romain , Bessière Eloïse , Gerya Taras
Published: March 2021

Subduction margins are the loci of a wide range of deformation processes occurring at different timescales along the plate interface and in the overriding forearc crust. Whereas long-term deformation is usually considered as stable over Myr-long periods, this vision is challenged by an increasing number of observations suggesting a long-term pulsing evolution of active margins. To appraise this emerging view of a highly dynamic subduction system and identify the driving mechanisms, detailed studies on high pressure-low temperature (HP-LT) exhumed accretionary complexes are crucial as they open a window on the deformation history affecting the whole forearc region.

In this study, we combine structural and petrological observations, Raman spectroscopy on carbonaceous material, Rb/Sr multi-mineral geochronology and thermo-mechanical numerical models to unravel with an unprecedented resolution the tectono-metamorphic evolution of the Late-Cenozoic HP-LT nappe stack cropping out in western Crete (Hellenic subduction zone). A consistent decrease of peak temperatures and deformation ages toward the base of the nappe pile allows us to identify a minimum of three basal accretion episodes between ca. 24 Ma and ca. 15 Ma. On the basis of structural evidences and pressure-temperature-time-strain predictions from numerical modeling, we argue that each of these mass-flux events triggered a pulse in the strain rate, sometimes associated with a switch of the stress regime (i.e., compressional/extensional). Such accretion-controlled transient deformation episodes last at most ca. 1-2 Myr and may explain the poly-phased structural records of exhumed rocks without involving changes in far-field stress conditions. This long-term background tectonic signal controlled by deep accretionary processes plays a part in active deformations monitored at subduction margins, though it may remain blind to most of geodetic methods because of superimposed shorter-timescale transients, such as seismic-cycle-related events.
Eclogite xenoliths document water cycling at the lithosphere-asthenosphere boundary
Authors: Reynes Julien , Hermann Jörg
Published: March 2021

The amount of water stored as OH-defects in nominally anhydrous minerals in the deep mantle is poorly constrained and its direct quantification can only be accessed by the analysis of mantle xenoliths. While the vast majority of xenoliths are peridotites and minor pyroxenites, some very rare xenoliths found in kimberlite pipes display an eclogitic mineral assemblage. We investigated three eclogite xenoliths from the 128 m.y. old Robert Victor kimberlite from South Africa that display an assemblage of garnet and omphacite with two samples showing additional kyanite, suggesting low-pressure gabbroic rock as protolith. Thermobarometry estimations based on Fe-Mg partitioning between garnet and pyroxene gives temperatures of 1100-1250 °C. When projected on the cratonic geotherm (Griffin & O’Reilly 2007) an equilibrium depth of 200-210 km is obtained, confirming that these rocks come from the lithosphere-asthenosphere boundary. Therefore these fragments might be key witnesses to understand the deep cycling of water in the mantle.

This study focuses on the H2O quantification in the three rock-forming minerals using Fourier transform infrared spectroscopy (FTIR). Omphacite contains 50-250 ppm H2O, kyanite contains 40-60 ppm H2O and garnet of only one eclogite contains 40 ppm H2O. Garnet and omphacite with the highest OH content are enriched in Ca.

The use of advanced mapping and profiling techniques enabled the investigation of the spatial repartition of the OH component in these minerals. High-resolution mapping (5.6 µm) of kyanite reveals diffusive gain of OH at the rim of the crystal that is interpreted as hydration during interaction with the kimberlitic melt. The OH plateau in the core of kyanite must therefore have been acquired previously, suggesting that this is residual OH that has been transported by subduction to the lithosphere-asthenosphere boundary by a once hydrated gabbroic protolith. Our results have implications for the retention of hydrogen over long timescale at the lithosphere-asthenosphere boundary and suggest that the deep cycling of water has been running since Archean times.

 

Griffin, W. L., & O'Reilly, S. Y. (2007). Cratonic lithospheric mantle: is anything subducted?. Episodes, 30(1), 43-53.
Cloud regime analysis over Central Europe based on 14 years of satellite data
Authors: Tzallas Vasileios , Hünerbein Anja , Deneke Hartwig , Stengel Martin , Meirink Jan Fokke , Benas Nikos , Trentmann Jörg
Published: March 2021

The improvement of our understanding of the spatiotemporal variability of cloud properties and their governing processes is of high importance, given the crucial role of clouds in the climate system. The availability of long-term and high-quality satellite observations together with mature remote sensing techniques has made feasible the creation of multi-decadal climate data records for this purpose.

Various cloud classification techniques have been developed and applied in the past, each with distinct advantages and disadvantages, allowing studying clouds from different perspectives. One of these techniques is the creation of cloud regimes which provides information on the prevalence of simultaneously occurring cloud types over a region. This study uses the k-means clustering method, applied to 2-dimensional histograms of cloud top pressure and optical thickness, in order to derive and analyze cloud regimes over Europe during the last decade. Europe is selected for this work because it is an appropriate region for studying cloud regimes since the prevailing atmospheric circulation patterns and its diverse geomorphology, result in a mixture of diverse cloud types. In order to achieve that, the CLoud property dAtAset using Spinning Enhanced Visible and Infrared (SEVIRI) edition 2.1 (CLAAS-2.1) data record, which is produced by the EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF), is used as basis for the derivation of the cloud regimes. In particular, pixel-level Cloud Optical Thickness (COT) and Cloud Top Pressure (CTP) products of CLAAS-2.1, from 2004 to 2017, are used in order to compute 2D histograms on a 1°×1° spatial resolution. Then the k-means clustering algorithm is applied, treating each 2D COT-CTP histogram of each grid point and time step as an individual data point. Various sensitivity studies on the subsampling of the data and the selection of the cloud regimes were carried out, in order to test the robustness of the method and of the results.

In contrast to the previous studies and taking advantage of the geostationary orbit of Meteosat Second Generation (MSG), on which SEVIRI is aboard, a better sampling of the diurnal cycle of clouds is thus included in the derivation process of cloud regimes. Furthermore, the annual cycle of the produced cloud regimes is examined. In addition, for each regime, the time step with its highest spatial frequency of occurrence is selected for a visual comparison with the corresponding RGB image. Finally, a comparison of the cloud regimes against the synoptic large scale weather pattern classification is investigated. The weather pattern classification consists of 29 typical defined patterns of the daily synoptic circulation and it is produced by the German Weather Service (DWD).
On the effect of ULF waves on the outer radiation belt during geomagnetic storms
Authors: Lara Christopher , Moya Pablo S. , Pinto Victor , Silva Javier , Zenteno Beatriz
Published: March 2021

The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.
The material point method for simulating dense snow avalanches over complex real terrain
Authors: Li Xingyue , Sovilla Betty , Jiang Chenfanfu , Gaume Johan
Published: March 2021

Various dynamics models can reproduce the motion of avalanches from release to deposition. These models often simulate a conceptual avalanche, adopt depth-averaged approaches and do not resolve variations along flow depth direction, and thus have clear limitations. This study presents three-dimensional, full-scale modeling of dense snow avalanches performed using the complex real terrain of the Vallée de la Sionne avalanche test site in Switzerland. We use the material point method (MPM) and a large-strain elastoplastic constitutive law for snow based on a Modified Cam Clay model. In our simulations, various and transient avalanche flow regimes are simulated by setting distinct snow properties. Snow avalanches are investigated from release to deposition. Detailed simulation results include the initial failure patterns, the mechanical behavior during the flow, and the characteristics of the final avalanche deposits. More specifically in the release zone, we can observe brittle and ductile fractures depending on the defined snow properties. During the flow phase, we monitor the temporal and spatial variations of snow density in the avalanche. In particular, cohesionless granular flows, cohesive granular flows, and plug flows are associated with snow fracture, compaction, and expansion. Finally, we can observe the structure of the avalanche deposit surfaces which show distinguishable differences in terms of smoothness, granulation, and compacting shear planes. This new model can offer a quantitative analysis for studying avalanches in different regimes and provide a powerful tool for exploring the dynamics of full-scale avalanches on complex real terrain, with high physical detail.
Classifying large strains from digital imagery: application to analogue models of lithosphere deformation
Authors: Broerse Taco , Krstekanic Nemanja , Kasbergen Cor , Willingshofer Ernst
Published: March 2021

We are interested in reconstructing the time evolution of 2D plane deformation of analogue models of tectonic processes. Under relevant forcings, these models develop internal deformation, such as faults, and broader zones of deformation. We use Particle Image Velocimetry (PIV) to derive incremental displacements from top-view images that we use in subsequent steps to calculate the shape changes that come with large deformation. Because PIV describes displacement in a spatial reference, and material moves through the area in view, displacements at any given time refer to fixed locations in space, and not to specific material points. By reconstructing the path of material, we can follow small regions of material while they translate, rotate and change shape.

To aid the qualitative interpretation of this deformation, we have developed a novel method that can qualitatively describe shape changes coming from extensional, shortening and horizontal shearing (strike-slip) deformation or combinations of these. This method is based on a logarithmic measure of stretch and results agree well with the visual interpretation of structures that we observe in our models. Thus, we provide tools with which the evolution of 2D tectonic deformation can be interpreted in a physically meaningful manner, but our method may be useful outside the realm of tectonics. Our software to compute deformation is freely available and can be used to post-process incremental displacements from PIV or similar autocorrelation methods.
The effect of magma poor and magma rich rifted margins on continental collision dynamics
Authors: Turino Valeria , Magni Valentina , Kjøll Hans Jørgen , Jakob Johannes
Published: March 2021

The transition between continental and oceanic lithosphere in rifted margins can display a wide range of characteristics, which primarily depend on the regional tectonic evolution. Rifted margins form when continents rift apart and are commonly characterized by a thinned transition zone between the continental crust and the oceanic crust. The velocity and duration of the rifting process influence the dimensions and geometry of the passive margin. Rifted (or passive) margins are often subdivided in a magma-rich type and a magma-poor type, where the magma-rich are characterized by large input of mafic melt, derived from the mantle, into the crust. Magma-poor rifted margins on the other hand are characterized by much less magma production during the rifting process. This causes high variability in the geometry and rheology of passive margins.

The aim of this work is to understand how different types of passive margins can influence the dynamics of continental collision. We modelled subduction using the finite element code Citcom and to describe the dynamics of continental collision we mainly focused on the time and position of the slab break-off after the collision and on the fate of the passive margin material.

We compared these models as a function of various parameters (e.g., margin length, density, and viscosity), in order to understand how the architecture of a passive margin affects the dynamics of continental collision. We find that passive margins have a noticeable impact on subduction, as we observe a large variability in slab break-off times (about 10–70 Myr after continental collision) and depth (about 200–450 km). Furthermore, the factor that shows the largest impact on subduction dynamics is the rheology of the passive margin. Our results show that for both magma-poor and magma-rich margins, part of the margin does not subduct but, instead, exhumes and accretes to the overriding plate. Importantly, the amount of accreted material to the overriding plate is much larger when the passive margin is magma-poor compared to the magma-rich case. This is consistent with geological observations that fossil magma-poor passive margins are preserved in many mountain ranges, such as the Alps and the Scandinavian Caledonides, whereas remnants of magma-rich rifted margins are scarce. Because, in our models, the slab break-off occurs inboard of the LCB, magma-rich rifted margin may only be preserved when the density of the LCB is similar to that of the rest of the continental plate. Therefore magma-rich rifted margins are prone to be subducted and recycled into the mantle. Importantly, our results show that rifted margin type controls the architecture of the subsequent collisional phase of the Wilson cycle.
A laboratory study of the effect of soil-water dynamics on the migration of gases from subsurface sources
Authors: Ilie Ana M. C. , Illangasekare Tissa H. , Soga Kenichi , Whalley William R.
Published: March 2021

Understanding the soil-gas migration in unsaturated soil is important in a number of problems that include carbon loading to the atmosphere from the bio-geochemical activity and leakage of gases from subsurface sources from carbon storage unconventional energy development. The soil water dynamics in the vadose zone control the soil-gas pathway development and, hence, the gas flux's spatial and temporal distribution at the soil surface. The spatial distribution of soil-water content depends on soil water characteristics. The dynamics are controlled by the water flux at the land surface and water table fluctuations. Physical properties of soil give a better understanding of the soil gas dynamics and migration from greater soil depths. The fundamental process of soil gas migration under dynamic water content was investigated in the laboratory using an intermediate-scale test system under controlled conditions that is not possible in the field. The experiments focus on observing the methane gas migration in relation to the physical properties of soil and the soil moisture patterns. A 2D soil tank with dimensions of 60 cm × 90 cm × 5.6 cm (height × length × width) was used.  The tank was heterogeneously packed with sandy soil along with a distributed network of soil moisture, temperature, and electrical conductivity sensors. The heterogeneous soil configuration was designed using nine uniform silica sands with the effective sieve numbers #16, #70, #8, #40/50, #110, #30/40, #50, and #20/30 (Accusands, Unimin Corp., Ottawa, MN), and a porosity ranging in values from 0.31 to 0.42. Four methane infrared gas sensors and a Flame Ionization detector (HFR400 Fast FID) were used for the soil gas sampling at different depths within the soil profiles and at the land surface.  A complex transient soil moisture distribution and soil gas migration patterns were observed in the 2D tank. These processes were successfully captured by the sensors. These preliminary experiments helped us to understand the mechanism of soil moisture sensor response and methane gas migration into a heterogeneous sandy soil with a view to developing a large-scale test in a 3D tank (4.87 m × 2.44 m × 0.40 m) and finally transition to field deployment.
Effect of aerosol vertical distribution on the transfer of solar radiation through the atmosphere
Authors: Fountoulakis Ilias , Papachristopoulou Kyriakoula , Proestakis Emmanouil , Gkikas Antonis , Raptis Panagiotis Ioannis , Siomos Nikolaos , Kontoes Charalampos , Kazadzis Stelios
Published: March 2021

Aerosols play a key role in radiative transfer processes at the Earth’s atmosphere. The complex interactions between aerosols and solar radiation cannot be easily modeled, and thus, aerosols constitute a major uncertainty factor in radiative transfer simulations. Radiative effects of aerosols depend not only on their physical and chemical properties, but also on their distribution in the atmosphere. Despite the important role of the vertical distribution of aerosols in the atmosphere, default climatological profiles are commonly used in modeling studies. Uncertainties related with the use of default profiles have been roughly analyzed and discussed in the existing bibliography.

In the context of the present study we simulated the downwelling and upwelling irradiance, heating rates, and the actinic flux at different altitudes, from 0 to 8 km, in the atmosphere. Simulations were performed for four different European sites – where aerosol mixtures constitute from quite different aerosol species – using a default climatological aerosol extinction profile, and the seasonally and annually averaged extinction profiles for each site from the LIdar climatology of Vertical Aerosol Structure for space-based lidar simulation studies (LIVAS). By comparing the results, the effect of using a more representative profile of the aerosol extinction coefficient for each of the sites, instead of a default climatological profile, was estimated. In addition to the aerosol profiles, climatological values of aerosol optical properties and water vapor from the AErosol RObotic NETwork (AERONET), the  version 2 Max-Planck-Institute Aerosol Climatologyand (MACv2), the Modis Dust AeroSol (MIDAS) climatology, and atmospheric and land-surface variables from the Copernicus Atmospheric Monitoring System (CAMS), were used as inputs to the libRadtran radiative transfer model. Spectra in the range 280 – 3000 nm were simulated for different solar zenith angles, and the integrals of the spectra, as well as the integrals in the ultraviolet and visible spectral regions were analyzed.

Results of the analyses are presented and discussed in order to study the sensitivity of the radiometric quantities simulated by the model to the used aerosol extinction profile, for each of the four sites. Differences between the products of the simulations when the used aerosol optical depth (AOD) comes from different sources (LIVAS, AERONET, MIDAS, CAMS) have been also investigated. 

Acknowledgements

This study was funded by the EuroGEO e-shape (grant agreement No 820852).
The Importance of Radiative Feedbacks in Tropical Cyclogenesis in Idealized Simulations
Authors: Wing Allison
Published: March 2021

Interactions between clouds, radiation, and circulations are fundamental to tropical climate, but until recently, the impact of these interactions on tropical cyclones (TCs) has been relatively unexplored. Simulations of rotating radiative-convective equilibrium confirm that radiative feedbacks are important for spontaneous TC genesis (in which a TC is allowed to form from random noise). While not strictly necessary, radiative feedbacks significantly accelerate TC genesis and especially contribute in the early stages of genesis. These radiative feedbacks arise from interactions between spatially and temporally varying radiative cooling (driven by the dependence of radiative cooling rate on clouds and water vapor) and the developing tropical cyclone (the circulation of which shapes the structure of clouds and water vapor).  However, TCs in nature are generally observed to form from pre-existing disturbances, calling into question whether radiative feedbacks play a significant role.

Here, I investigate the importance of radiative feedbacks in TC genesis and the mechanisms underlying their influence in a set of idealized cloud-resolving simulations in which a TC is allowed to develop after initialization from a mesoscale warm, saturated bubble on an f-plane, in an otherwise quiescent and moist neutral environment. TC genesis is delayed by a factor of two or three when radiative feedbacks are removed by prescribing a fixed cooling profile or spatially homogenizing the model-calculated cooling profiles. Further analysis and additional mechanism denial experiments pinpoint the longwave radiative feedback contributed by ice clouds as the strongest influence. These results are consistent with recently published case study simulations in which cloud-radiative effects accelerate TC formation and intensification in realistic scenarios. The important takeaway from the results presented here is that that cloud-longwave radiative feedbacks have a profound impact on TC genesis in a hierarchy of model simulations. Improving the representation of cloud-radiative feedbacks in forecast models therefore has the potential to yield critical advancements in TC prediction.
An application of field-based photogrammetry as a virtual outcrop building target: a key example from Santorini’s northern caldera wall, Greece
Authors: Bonali Fabio Luca , Fallati Luca , Antoniou Varvara , Drymoni Kyriaki , Pasquaré Mariotto Federico , Corti Noemi , Tibaldi Alessandro , Gudmundsson Agust , Nomikou Paraskevi
Published: March 2021

The application of photogrammetry to volcanic areas is usually made using UAVs for collecting pictures aimed at producing high-resolution orthomosaic and digital surface models. In the present work, instead, we use a boat-camera-based photogrammetry approach, as a tool for orthomosaic, digital surface modelling and virtual outcrop production at an almost vertical 300-m-high geological feature: the northern caldera wall of Santorini. This is a geological structure of great interest, where many tens of dykes crop out within a heterogeneous host rock made of sequences of effusive and explosive volcanic deposits. Some active and inactive faults also dissect the caldera wall. Thus, the study area is almost inaccessible for classic field surveys due to challenging logistic conditions and landslide hazard.

We used a 20 MPX camera run by an operator who collected a total of 887 pictures almost continuously, orthogonal to the ground and opposite to the target, during a 5.5-km-long boat survey. We performed the study along the northern caldera wall, at a constant boat velocity and at a distance from the coast/caldera wall that varied between 35.8 m and 296.5 m. The outcomes of the photogrammetry application include: 1) a high-resolution 3D model of the study area, 2) a high-resolution virtual outcrop for two selected parts of the caldera, 3) qualitative and quantitative structural data (dyke attitude, thickness, cross-cutting relationships, host rock lithology) along the vertical caldera cliff. Our method represents a new approach for 3D outcrop building for research under extreme logistic conditions.
The City Pack - the co-production of an urban climate service providing local summaries of a city's future climate 
Authors: Fuller Elizabeth , Scannell Claire , Ramsey Victoria , Parfitt Rebecca , Golding Nicola
Published: March 2021

In 2018, the UN estimated that around 55% of the world’s population currently live within urban areas, with this value projected to rise to 60% by 2030 (United Nations, 2018). High levels of urbanisation, coupled with an increasing trend in extreme weather under future climate change scenarios, combine to create significant challenges to increasing urban resilience for the future (Masson et al., 2020).

Urban climate services provide tools to support decision making at a range of scales across the city, from day-to-day operations to informing urban design over longer timescales (Grimmond et al., 2015). Whilst urban climate services may be developed at a range of scales (Grimmond et al., 2020), this presentation looks at a prototype climate service which provides long-term climate change projections at the city-specific scale. The ‘City Pack’ was developed through a process of co-production, in which project development aims to move away from a one-way push of scientific information, to a two-way collaborative process of knowledge construction and sharing (Vincent et al., 2019).

This ‘City Pack’ service was co-developed by the Met Office and Bristol City Council following an assessment of the Council’s climate information needs. The City Pack comprises of three non-technical factsheets which explain how the climate of Bristol has changed and will continue to change into the 21st Century based on the UKCP climate projections. The City Pack’s primary aims are to raise awareness of how a cities climate may change in the future and to inform the development of city resilience whilst also providing a tool to be used by city stakeholders to raise awareness of climate change across the council. The audience for the City Pack therefore includes city officials, city planners and the general public. The Bristol City Pack has since provided an evidence base for the Bristol City Council Climate Change Risk Assessment and informed Bristol’s Climate Strategy. In addition, the City Pack has been used to engage with the council’s wider stakeholders and also as a communication and training tool. As such, whilst the co-production of a climate service may be time and resource intensive, the process may also be rewarded with the production of a highly tailored and user-relevant tool.

Following the success of the prototype ‘City Pack’ service for Bristol City Council, the Met Office are continuing to produce City Packs for additional cities across the UK, and also in China. The project is seeking to ascertain if services which are co-produced with and bespoke to one set of stakeholders, may provide an equally valuable service for other cities and if so, how can we make these services scalable.
Attenuated carbon sequestration by Weddell Sea dense waters over the 21st century – an assessment with FESOM-REcoM
Authors: Nissen Cara , Timmermann Ralph , Hoppema Mario , Hauck Judith
Published: March 2021

Deep and bottom water formation regions have long been recognized to be efficient vectors for carbon transfer to depth, leading to carbon sequestration on time scales of centuries or more. Precursors of Antarctic Bottom Water (AABW) are formed on the Weddell Sea continental shelf as a consequence of buoyancy loss of surface waters at the ice-ocean or atmosphere-ocean interface, which suggests that any change in water mass transformation rates in this area affects global carbon cycling and hence climate. Many of the models previously used to assess AABW formation in present and future climates contained only crude representations of ocean-ice shelf interaction. Numerical simulations often featured spurious deep convection in the open ocean, and changes in carbon sequestration have not yet been assessed at all. Here, we present results from the global model FESOM-REcoM, which was run on a mesh with elevated grid resolution in the Weddell Sea and which includes an explicit representation of sea ice and ice shelves. Forcing this model with ssp585 scenario output from the AWI Climate Model, we assess changes over the 21st century in the formation and northward export of dense waters and the associated carbon fluxes within and out of the Weddell Sea. We find that the northward transport of dense deep waters (σ2>37.2 kg m-3 below 2000 m) across the SR4 transect, which connects the tip of the Antarctic Peninsula with the eastern Weddell Sea, declines from 4 Sv to 2.9 Sv by the year 2100. Concurrently, despite the simulated continuous increase in surface ocean CO2 uptake in the Weddell Sea over the 21st century, the carbon transported northward with dense deep waters declines from 3.5 Pg C yr-1 to 2.5 Pg C yr-1, demonstrating the dominant role of dense water formation rates for carbon sequestration. Using the water mass transformation framework, we find that south of SR4, the formation of downwelling dense waters declines from 3.5 Sv in the 1990s to 1.6 Sv in the 2090s, a direct result of the 18% lower sea-ice formation in the area, the increased presence of modified Warm Deep Water on the continental shelf, and 50% higher ice shelf basal melt rates. Given that the reduced formation of downwelling water masses additionally occurs at lighter densities in FESOM-REcoM in the 2090s, this will directly impact the depth at which any additional oceanic carbon uptake is stored, with consequences for long-term carbon sequestration.
Nano-HTDMA for investigating hygroscopic properties of sub-10 nm aerosol nanoparticles
Authors: Lei Ting , Ma Nan , Hong Juan , Tuch Thomas , Wang Xin , Wang Zhibin , Pöhlker Mira , Ge Maofa , Wang Weigang , Mikhailov Eugene , Hoffmann Thorsten , Pöschl Ulrich , Su Hang , Wiedensohler Alfred , Cheng Yafang
Published: March 2021

Interactions between water and nanoparticles are of great significance for atmospheric multiphase processes, physical chemistry, and materials science. Current knowledge of the hygroscopic and related physicochemical properties of nanoparticles, however, is insufficient due to limitations of the available measurement techniques. Here, we present the design and performance of a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) apparatus. To enable high accuracy and precision in hygroscopicity measurements of sub-10 nm aerosol nanoparticles, systematic and comprehensive calibration criteria of nano-HTDMA have been developed and applied, including sheath/aerosol flow rates, DMA voltage, relative humidity (RH) sensor, temperature sensor, and particle sizing. After calibration, the nano-HTDMA system has been shown to have an accurate sizing and a small sizing offsets between the two DMAs (<1.4%) for aerosol nanoparticles with diameters down to 6 nm. Moreover, to maintain the RH-uniformities that prevent the pre-deliquescence and non-prompt phase transition of nanoparticles within DMA2, the RH of sheath flow is kept as same as that of aerosol flow at inlet of DMA2, and the humidification system and the DMA2 system are placed in a well-insulated and air conditioner housing (±0.1K). Using nano-HTDMA system. We investigate the hygroscopic behavior of aerosol nanoparticles of two inorganic substances (e.g., ammonium sulfate and sodium sulfate). A strong size dependence of the hygroscopic growth factor is observed for ammonium sulfate and sodium sulfate nanoparticles with diameters down to 6 nm, respectively. For size dependence of phase transition, we find a weak size dependence of DRH and ERH of ammonium sulfate nanoparticles with diameters from 6 to 100 nm but a pronounced size dependence of DRH and ERH between 20 and  6 nm for sodium sulfate nanoparticles.
Unperturbed root fungal communities in a temperate forest recovering from five years of reoccurring droughts 
Authors: Danzberger Jasmin , Werner Ramona , Weikl Fabian , Pritsch Karin
Published: March 2021

Since industrialization, the global average temperature increases with far reaching consequences for the world climate. One phenomenon is the current occurrence of more heavy and long droughts in Middle Europe, which lead to extensive tree die-off and shows that we need a better understanding of the forest-soil ecosystem in times of climate change.

Within the interdisciplinary Kranzberg Roof Experiment, we study the drought resistance and drought recovery of mature Norway spruce (Picea abies) and European beech (Fagus sylvatica). The trees experienced a rainfall exclusion for five years during the vegetation period and were rewetted by drip irrigation in summer 2019. Our interest focuses in the functional role of ectomycorrhizal and overall fungal communities on tree drought resistance and recovery. Particularly, we hypothesized the rewetting event will lead to a shift in community structure because of steeply rising water and nutrient availabilities.

To get insights to the development of the fungal communities right after the rewetting period, we sequenced the fungal ITS2 region of fine root DNA extracts. The roots were taken from soil cores before and at several time-points after irrigation.

We found that the fungal communities stayed quite similar to each other during the time-frame of recovery we investigated (84 days), while the amount of new root tips strongly increased directly after the rewetting. Surprisingly, the organic material which had accumulated as it was not degraded during the years of drought, did not lead to a shift in community composition. In particular, there were no changes in the relative amounts of saprotroph fungi in the phase after the rewetting.

Therefore, root fungal communities – the interface between trees and soil – seemingly did not experience a strong pressure to adapt their composition to the new condition, which matches their resistant behavior during the long drought phase before (cf. abstract 2937).
South American fires and their impacts on ecosystems increase with continued emissions
Authors: Burton Chantelle , Kelley Douglas , Jones Chris , Betts Richard , Cardoso Manoel , Anderson Liana
Published: March 2021

Unprecedented fire events in recent years are leading to a demand for improved understanding of how climate change is already affecting fires, and how this could change in the future. Increased fire activity in South America is one of the most concerning of all the recent events, given the potential impacts on local health and the global climate from loss of large carbon stores under future environmental change. However, due to the complexity of interactions and feedbacks, and lack of complete representation of fire biogeochemistry in many climate models, there is currently low agreement on whether climate change will cause fires to become more or less frequent in the future, and what impact this will have on ecosystems. Here we use the latest climate simulations from the UK Earth System Model UKESM1 to understand feedbacks in fire, dynamic vegetation, and terrestrial carbon stores using the fire-enabled land surface model JULES-INFERNO, taking into account future scenarios of change in emissions and land use. Based on evaluation of the modelling framework performance for the present day, we address the specific policy-relevant question: how much fire-induced carbon loss will there be over South America at different global warming levels in the future? We find that burned area and fire emissions are projected to increase in the future due to hotter and drier conditions, which leads to large reductions in carbon storage especially when combined with increasing land-use conversion. The model simulates a 38% loss of carbon at 4°C under the highest emission scenario, which could be reduced to 8% if temperature rise is limited to 1.5°C. Our results provide a critical assessment of ecosystem resilience under future climate change, and could inform the way fire and land-use is managed in the future to reduce the most deleterious impacts of climate change.
Reciprocal Interaction between Waves and Turbulence within the Nocturnal Boundary-Layer
Authors: Barbano Francesco , Brogno Luigi , Tampieri Francesco , Di Sabatino Silvana
Published: March 2021

The presence of waves in the nocturnal boundary layer has proven to generate complex interaction with turbulence. On complex terrain environments, where turbulence is observed in a weak but continuous state of activity, waves can be a vehicle of additional production/loss of turbulence energy. The common approach based on the Reynolds decomposition is unable to disaggregate turbulence and wave motion, thus revealing impaired to explicit the terms of this additional interaction. In the current investigation, we adopt a triple-decomposition approach to separate mean, wave, and turbulence motions within near-surface boundary-layer flows, with the aim of unveiling the role of wave motion as source and/or sink of turbulence kinetic and potential energies in the respective explicit budgets. This investigation reveals that the waves contribute to the kinetic energy budget where the production is not shear-dominated and the budget equation does not reduce to a shear-dissipation balance (e.g., as it occurs close to a surface). Away from the surface, the buoyancy effects associated with the wave motion become a significant factor in generating a three-terms balance (shear-buoyancy-dissipation). Similar effects can be found in the potential energy budget, as the waves affect for instance the production associated with the vertical heat flux. On this basis, we develop a simple interpretation paradigm to distinguish two layers, namely near-ground and far-ground sublayer, estimating where the turbulence kinetic energy can significantly feed or be fed by the wave. To prove this paradigm and evaluate the explicit contributions of the wave motion on the turbulence kinetic and potential energies, we investigate a nocturnal valley flow observed under weak synoptic forcing in the Dugway Valley (Utah) during the MATERHORN Program. From this dataset, the explicit kinetic and potential energy budgets are calculated, relying on a variance-covariance analysis to further comprehend the balance of energy production/loss in each sublayer. With this investigation, we propose a simple interpretation scheme to capture and interpret the extent of the complex interaction between waves and turbulence in nocturnal stable boundary layers.
Train Deep Learning Models using subsurface geological images datasets
Authors: Abdallah Ramy , Bond Clare E. , Butler Robert W.H.
Published: March 2021

Machine learning is being presented as a new solution for a wide range of geoscience problems. Primarily machine learning has been used for 3D seismic data processing, seismic facies analysis and well log data correlation. The rapid development in technology with open-source artificial intelligence libraries and the accessibility of affordable computer graphics processing units (GPU) makes the application of machine learning in geosciences increasingly tractable. However, the application of artificial intelligence in structural interpretation workflows of subsurface datasets is still ambiguous. This study aims to use machine learning techniques to classify images of folds and fold-thrust structures. Here we show that convolutional neural networks (CNNs) as supervised deep learning techniques provide excellent algorithms to discriminate between geological image datasets. Four different datasets of images have been used to train and test the machine learning models. These four datasets are a seismic character dataset with five classes (faults, folds, salt, flat layers and basement), folds types with three classes (buckle, chevron and conjugate), fault types with three classes (normal, reverse and thrust) and fold-thrust geometries with three classes (fault bend fold, fault propagation fold and detachment fold). These image datasets are used to investigate three machine learning models. One Feedforward linear neural network model and two convolutional neural networks models (Convolution 2d layer transforms sequential model and Residual block model (ResNet with 9, 34, and 50 layers)). Validation and testing datasets forms a critical part of testing the model’s performance accuracy. The ResNet model records the highest performance accuracy score, of the machine learning models tested. Our CNN image classification model analysis provides a framework for applying machine learning to increase structural interpretation efficiency, and shows that CNN classification models can be applied effectively to geoscience problems. The study provides a starting point to apply unsupervised machine learning approaches to sub-surface structural interpretation workflows.