bluuebunny/crossref_metadata_2025 huggingface dataset:
A new experimental approach to assess the influence of gravity gliding on salt tectonics in rift basins
Authors: Warsitzka Michael , Závada Prokop , Jähne-Klingberg Fabian , Krzywiec Piotr
Published: March 2021

Salt flow in rift basins is mainly driven by sub- and supra-salt extension imposing shear stresses and differential loading on the salt layer. In many rift basins, the graben flanks are tilted as a result of thermal subsidence and sediment load. Such tilt induces additional basin-ward directed stresses potentially causing downward directed salt flow and gravity gliding of the supra-salt overburden. However, sediment loading in extensional basins is usually largest in the basin centre, which would lead to an upward directed salt expulsion and might act as an effective buttress resisting downward gliding.

Our aim is to investigate the opposing influence of sub-salt extension, sedimentary loading and tilting on deformation patterns in the viscous salt and the brittle overburden. We try to assess under which geological configurations (e.g. minimum basin slope or topographic gradient) upward directed salt flow and downward directed gravity gliding are the dominating deformation processes in extensional basins. Therefore, we developed a new analogue modelling apparatus enabling to simulate the processes of tectonic extension of a graben structure and the gradual tilting of the graben flanks, acting either simultaneously or separately. Using digital image correlation technique, temporal and spatial changes of the displacement and strain patterns can be analysed. Cross sections through the final experiments enable to identify structures characteristic for specific driving processes.

Here, we present results of a preliminary experimental study in which the basic influence of flank tilting and syn-kinematic sedimentation on salt tectonics in rift basins is examined. In case that the graben flanks remain flat during extension, widespread extensional fault zones develop on the footwall sides near the graben faults. In case that the flanks are tilted simultaneously with basal extension, additional extensional fault zones evolve at the upslope basin margins resulting from downward gliding of the overburden. In the downslope basin centre, this peripheral extension is balanced by reduced amounts of extension near the graben and later by shortening above the graben bounding faults and the hanging wall graben centre. If syn-kinematic sedimentation is introduced, downslope gravity gliding is significantly reduced and extensional fault zones are rather localized. Peripheral extensional structures observed in the experiments resemble typical thin-skinned extensional structures occurring at the flanks of many salt-bearing rift basins, e.g. the Polish Basin and Norwegian-Danish Basin. Thus, such structures might serve as diagnostic indicators for the occurrence of gravity gliding in rift basins.
The DYAMOND Winter data collection
Authors: Duras Julia , Ziemen Florian , Klocke Daniel
Published: March 2021

The DYAMOND project (DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains) is the first initiative for a model intercomparison of global storm resolving (km-scale) climate simulations. The analysis of these simulations advances the understanding of the climate system and improves the next-generation of weather and climate models. In a first phase, a period of 40 days from 1st of August 2016 was simulated, with all models starting from the same initial conditions. The resulting data set is referred to as ”DYAMOND Summer” data. In its second, currently ongoing phase ”DYAMOND Winter”, participating models simulate 40 days starting on the 20th of January 2020, also covering the period of the EUREC4A field experiment. While the DYAMOND Summer only included atmosphere models, the DYAMOND Winter data set also includes coupled atmosphere-ocean models resolving ocean-eddies, atmospheric storms and their interactions.
The analysis of these simulations allows to identify robust features common to this class of new models, and provides insights into implementation-dependence of the results and a hint of the future of climate modelling (e.g. Arnold et al., 2020 ; Dueben et al., 2020 ; Stevens et al., 2020 ; Wedi et al., 2020 ). 
The Centre of Excellence in Simulation of Weather and Climate in Europe (ESiWACE) and the German Climate computing centre (DKRZ) are making this data available to the research community. For this purpose, a user-friendly central point of access, the so-called “DYAMOND data library” has been developed. It provides access to the Summer and Winter data collections. A growing community with a lively exchange (e.g. during regular Hackathons) further simplifies the usage of these data sets. 

The presentation will introduce the DYAMOND project with a focus on the new DYAMOND Winter data collection. It will present the corresponding experiment protocol and the participating models. To invite scientists to use these data sets, different ways of using the data on the supercomputer of DKRZ will be described in detail.
Analysis of wind resource under heat wave conditions in southern Europe
Authors: Molina María Ofelia , Sánchez Enrique , Gutiérrez Claudia , Ortega María
Published: March 2021

In recent years, renewable energy is gaining importance in the energy mix, increasing the dependence of the energy system on weather. Atmospheric patterns that affect wind energy production focusing on the winter months have been studied in previous works, as wind resource in Europe is higher for this season, but also because it is when there is a greater and more stable heating demand in Europe. Southern European countries, however, present summer demand increases due to the cooling needs of these countries (Spain, Portugal , Italy and Greece). These increases have been seen with real daily demand data from ENTSO-E (the European Network of Transmission System Operators for Electricity). Demand in Spain is even higher on days of heat waves in the 2015-2018 period, reaching in that case the annual maxima. The objective of this work is to study the wind patterns in these episodes of heat waves. Reduced overall summer wind power supply coupled with high energy demand under these conditions could be compromised. We will analyse means of daily wind anomalies on days of heat waves (composites) using data from the ERA5 reanalysis and the E-OBS temperature observations. The study of the wind resource in conditions of high energy demand due to extreme climate events, can help in the energy supply strategic planning and control to minimize the impact of these events on an electricity system with high penetration of renewables.

 
Methane exchange in forests
Authors: Ma Ruochan , Stockdale James , P. McNamara Niall , Morison James , Yamulki Sirwan , Toet Sylvia
Published: March 2021

Methane (CH4) is the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2), globally responsible for more than 20% of the additional radiative forcing since 1750. Well-drained forest soils are considered as one of the most important biological CH4 sinks. Net CH4 exchange in forest soils depends on the balance of two contrasting microbial processes, i.e. CH4 production and CH4 oxidation, which are controlled by the population and activity of methanogens and methanotrophs, respectively. Additionally, recent reports have shown that living stems and shoots of trees in forests may produce and emit substantial quantities of CH4, which can offset CH4 consumption by soils; potentially switching the forest from a net CH4 sink to a net source.

Tree-emitted CH4 in forests may result from biological production in soils which is subsequently absorbed by roots and then transported in stems and emitted from stems and leaves. However, there is also evidence that CH4 emissions from living tree stems may be biologically produced in situ within tree stems themselves. Long-term and high-frequency measurements of stem CH4 flux in various individuals, tree species and forest ecosystems are needed to unravel the potential underlying mechanisms and pathways of stem CH4 exchange.

This research compares CH4 exchange from tree stem fluxes and soil in forest stands of English oak (Quercus robur) and Japanese larch (Larix kaempferi) and tries to understand the underlying mechanism of stem CH4 exchange in temperate forests. High-frequency measurements of tree stem CH4 exchange across various individuals were carried out in 2020 and the results will be presented from this study to help inform forest management and how to promote this globally important forest CH4 sink under climate change.
The simulation of groundwater spatiotemporal changes under the uncertainty of hydrogeological conditions
Authors: Lin Huan-Sheng , Lin Yuan-Chien
Published: March 2021

Groundwater is a reliable freshwater resource in many areas, and it is also an important source of backup water during the drought. Therefore, understanding the characteristics of groundwater resources is crucial and can be explored by building correct hydrogeological models for simulation. To build a perfect hydrogeological model, it is necessary to grasp the correct geological conditions and hydrogeological parameters to establish an effective numerical simulation of groundwater flow. However, geological conditions always contain some uncertainties, which may cause a certain impact on the spatiotemporal changes of groundwater.

Therefore, this study uses the groundwater flow numerical model, MODFLOW, to build the groundwater simulation model. The ideal case and real case at Touqiao Minshiung Industrial Zone in Chiayi is built from 2009 to 2013. The results show that under different hydrogeological parameters, geology, and other conditions, groundwater will have different patterns of variation. The Empirical Orthogonal Function (EOF) method is also used to compare the dominated patterns. The simulation results show the R2 can all reach 0.9 compare with the groundwater real observation data. This study can further explore the drought-resistant availability of groundwater in various regions under different geological conditions, it will help relevant agencies and local governments to better manage groundwater resources.

Keywords: groundwater simulation, MODFLOW, uncertainty, hydrogeology, EOF

 

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*Department of Civil Engineering, National Central University
Cyclostratigraphy of a type-Maastrichtian chalk record, based on high-resolution geochemical analysis of the Gulpen Formation, NE Belgium 
Authors: Huygh Jarno , Vellekoop Johan , Sinnesael Matthias , Kaskes Pim , Jagt John , Claeys Philippe
Published: March 2021

Cyclostratigraphic studies on carbonate successions have proved invaluable for understanding palaeoclimate and for constructing improved, high-resolution age models of the Late Cretaceous. Whereas carbonate strata from the type-Maastrichtian from the Netherlands and Belgium have provided a wealth of palaeontological data, so far, dating of these deposits has relied mainly on biostratigraphy and preliminary attempts at cyclostratigraphy. The existing basic cyclostratigraphic framework is based principally on apparent cyclic variations in bioclast composition and suggested Milankovitch-paced flint cycles. Until now, these strata have not yet been examined using a cyclostratigraphic approach based on high-resolution multi-proxy geochemical data sets. Within the scope of the Maastrichtian Geoheritage Project, we attempt to construct an improved astrochronological age model for Maastrichtian chalk deposits of the Gulpen Formation.

We have carried out a high-resolution elemental composition analysis of the Lower to Middle Maastrichtian chalk succession exposed at the Hallembaye (Kreco) quarry, NE Belgium. Approximately 460 chalk samples were collected every 5 cm over a 23-metre-thick stratigraphic interval and analysed as homogenised powders using micro X-ray fluorescence. This extensive elemental data set is used to evaluate (regular) changes in palaeoenvironmental conditions over time. Additionally, stratigraphic comparison of variations in elemental concentrations in the chalk with the occurrence of flint layers provides insights into potential diagenetic alterations. 

Preliminary results display promising trends with potential for the development of a cyclostratigraphic age model for the Gulpen Formation. Significant correlation between the main matrix elements calcium and silica might suggest a relationship between silica-depleted chalk and occurring flint layers throughout the chalk succession. Additionally, observed rhythmic variations in elements including - but not limited to - titanium, aluminium and potassium might exemplify changing palaeoenvironmental conditions. This improved astrochronological age model can be compared with age-equivalent astrochronologies and will, in combination with ongoing carbon isotope stratigraphy work, enable a better dating of the geological and biological records from the type-Maastrichtian. 
Parallel or not? Quantitative and qualitative methods to identify dissimilarities between sub-conformable contacts
Authors: Michalak Michał , Teper Lesław
Published: March 2021

In geological modelling it is often assumed that sub-conformable contacts are parallel. Here, we challenged this assumption by comparing conformable and unconformable horizons within Kraków-Silesian Homocline, Poland. The study objective was to provide both quantitative and qualitative analyses of dissimilarities between contacts of interest. The quantitative portion of the research involved geostatistical modelling of angular distance between contacts subdivided by Delaunay triangulation. We confirmed that in general the angular distances within conformable contacts are smaller than these between genetically unrelated horizons. However, there are exceptions from this rule related mainly to elongated zones of unknown origin in which angular distances are greater for sub-conformable contacts. The qualitative portion of the research was based on a specific variant of spatial clustering method based on Delaunay triangulation. Using this method, we aimed to identify geological differences underlying the increased values of angular distances in specific places. We identified convex forms that are developed only in some of the analysed contacts. These convex forms may be due to differences in the competence of tectonically deformed rocks. In such a case, discrete displacements of brittle sandstones are replaced by continuous deformation of claystones in the cover, represented by fault-related flexures or drape folds, which results in sharp changes in the angular distances observed. Acknowledgements: The project is funded by National Science Centre Poland, 2020/37/N/ST10/02504
Impact of different attitude modes on Jason-3 precise orbit determination and antenna phase center modeling
Authors: Kobel Cyril , Arnold Daniel , Jäggi Adrian
Published: March 2021

Global Navigation Satellite Systems such as the Global Positioning System (GPS) are a unique tool for deriving very precise orbits of Low Earth orbiting (LEO) satellites equipped with onboard GPS receivers. LEO precise orbit determination (POD) requires the proper modeling of antenna phase center variations (PCVs) for both the GPS transmitter and the LEO receiver antennas. While for the GPS antennas the nadir-dependent values from the official absolute antenna phase center model igs14.atx of the International GNSS Service (IGS), consistent with the underlying GPS orbit and clock products, are used, official PCV maps are usually not available for the LEO receiver antennas. If these variations are not considered, however, this may result in systematic errors in the derived LEO orbits. LEO PCV maps can be determined and exploited in different ways. One possibility is to use the PCV maps from ground calibrations provided by the manufacturer, which usually do not reflect, however, the influence of error sources which are additionally encountered in the actual spacecraft environment, e.g., near-field multipath. Alternatively, one can make use of GPS measurements and POD results to estimate the PCV map empirically, as it is done in this study.

In this study, the influence of different attitude modes on Jason-3 POD using GPS observations and PCV map estimation is investigated. As Jason-3 in an altimetry satellite, its main objective is to measure global sea-level rise. Therefore, it is of particular importance to precisely determine the radial component of the orbit and proper PCV modeling is of high importance. As Jason-3 is experiencing different attitude modes, yaw-steering and fixed-yaw attitude with either the positive or negative x-axis pointing in the direction of flight, PCV maps are expected to be better disentangled from other error sources. In this study, we are analyzing PCV maps determined from residual stacking using GPS data from the different attitude modes and from different orbit parametrizations. First results indicate that PCV maps estimated from time spans of different attitude modes differ and systematic orbit differences are occurring in a reduced-dynamic POD.
Multi-proxy studies of the Late Glacial fluvio-aeolian succession in the type site Mierzyn, central Poland 
Authors: Piotr Moska , Robert Sokołowski , Zdzisław Jary , Paweł Zieliński , Jerzy Raczyk , Marcin Krawczyk , Jacek Skurzyński , Grzegorz Poręba , Michał Łopuch , Agnieszka Szymak , Konrad Tudyka
Published: March 2021

Multi-proxy studies (including sedimentological, pedological, radiocarbon and optically stimulated luminescence dating methods) were used to establish origin and chronology of depositional processes in the type section Mierzyn, central Poland. The investigated key site is located in the extraglacial zone of the Last Glaciation, ca. 130 km to the south from the Last Glacial Maximum in the Luciąża river valley area. In the studied profile (16 m thick) two lithofacial complexes were identified. The lower, fluvio-aeolian complex consists of silty-sandy sediments (1.6 m) deposited. The final phase of fluvio-aeolian deposition is expressed by initial pedogenic processes. Above is located aeolian complex (13 m of thickness). Three aeolian units are separated by two palaeosols.

To establish stratigraphic framework of depositional and pedogenic processes, four samples for radiocarbon dating from palaeosols and twelve samples for OSL dating from sandy units were collected. The obtained results reveal very good agreement of both absolute dating methods. It led to reconstruct chronology of main palaeoenvironmental changes. The fluvio-aeolian complex and the lowermost part of aeolian complex (below the lower palaeosol) were deposited in the Oldest Dryas in relatively cool and dry climate conditions. The amelioration of climate in the Bølling interstadial caused development of pedogenic processes expressed by 0.3 m thick palaeosol. Main part of aeolian complex (10 m of thickness) was deposited in the Older Dryas. The upper palaeosol developed in the Allerød interstadial as a result of the next amelioration of the climate. During the Younger Dryas was deposited the uppermost part of aeolian complex.

Classic development of fluvial to- aeolian succession in the Mierzyn site as well as detailed chronology based on two independent absolute age methods reveal that it can be treated as stratotype for the Late Glacial and correlated with other type sections in the Central and Western Europe.

Ackowledgments

Presented results were obtained with support of Polish National Science Centre, contract number 2018/30/E/ST10/00616.

 
Locomotion of juvenile silver carp (Hypophthalmichthys molitrix) near the separation zone at the channel confluence
Authors: Xu Lei , Yuan Saiyu , Zheng Yuchen , Chen Yihong
Published: March 2021

Knowledge of locomotion of fish with significant rheotaxis at river confluences is critical for prediction of fish distribution at a river network. Recently, less silver carps observed in the Poyang Lake should be related to the hydrodynamic change at the confluence of the lake outlet and the Yangtze River. The operation of the Three Gorges Dam has largely changed the hydrodynamics at this confluence. Silver carp is one of the four major Chinese carps, and has significant rheotaxis. In this study, a series of laboratory experiments were conducted to figure out the behavioral responses of juvenile silver carps to hydrodynamics near the separation zone at the channel confluence. The separation zone at a river confluence is one of the main zones for carp habitat and feeding. The locomotion and trajectory of juvenile silver carps were recorded through infrared thermal imaging at the confluence flume. Flow velocity field near the separation zone was measured by a Particle Image Velocimetry (PIV) system. A total of 40 juvenile silver carps were released from the separation zone and swam to the upstream, among which 24 carps swam to the tributary and the other to the main channel. Almost all 24 carps moved along the beginning of the boundary of the separation zone near the corner where the flow shear was strong. It seems that instead of avoiding places with great vorticity, they preferentially chose the trajectory where the flow vorticity was large continuously. They increased the tail-beat frequency and decreased the tail-beat amplitude to maintain body stability when they encountered the flow with large vorticity. These results are beneficial for the regulation of upstream dams to adjust the hydrodynamics at the confluence and improve local ecology.
Novel assessment of model relative humidity with satellite probabilistic estimates
Authors: Radice Chloé , Brogniez Hélène , Kirstetter Pierre-Emmanuel , Chambon Philippe
Published: March 2021

Remote sensing data are often used to assess model forecasts on multiple scales, generally by confronting past simulations to observations. This paper introduces a novel probabilistic  method that evaluates  tropical atmospheric relative humidity (RH) profiles simulated by the global numerical model for weather forecasting ARPEGE  with respect to probability distributions of finer scale satellite observations.   

The reference RH is taken from the SAPHIR microwave sounder onboard the Megha-Tropiques satellite in operations since 2011. ARPEGE simulates the RH field every 6h hours on a 0.25° grid over 18 vertical levels ranging between 950hPa and 100hPa. The reference probabilistic RH field is retrieved from brightness temperatures measured by SAPHIR with a footprint resolution ranging from 10 km (nadir) to 23 km (edge of swath) on 6 vertical layers, ranging from 950hPa to 100hPa. Footprint scale RH are aggregated (convoluted) over the spatial and temporal scale of comparison to match the model resolution and summarize the patterns over a significant period. Comparison  results will be shown over the April-May-June 2018 period for two configurations of the ARPEGE model (two parametrization schemes for convection). The probabilistic comparison is discussed with respect to a classical deterministic comparison of RH values.

This probabilistic approach allows to keep all the sub-grid information and, by looking at the distribution as a whole, avoids the classical determinist simplification that consists of working with a simple “best” estimate. This method allows a finer assessment by working on a case-by-case basis and allowing a characterisation of specific situations. It provides an added-value by accounting for  additional information in the evaluation of the simulated field, especially for model simulations that are close to the traditional mean.
Breaking The Silos: an online and narrator-led role-playing game for multi-risk DRR management
Authors: de Ruiter Marleen , Couasnon Anaïs , Ward Philip
Published: March 2021

The increased complexity of disaster risk due to climate change, expected population growth and the increasing interconnectedness of disaster impacts across communities and economic sectors, require Disaster Risk Reduction (DRR) measures and practitioners that are better able to address these complexities. Nonetheless, in the traditional risk paradigm, there is a strong focus on single-hazards and the risk faced by individual communities and sectors.

Breaking the Silos is a narrator-led, role-playing game designed to support decision makers and stakeholders in understanding and managing the complexities of implementing DRR measures in a multi-(hazard) risk setting. The game starts in de aftermath of a (randomly selected) disaster. The different roles include key decision-makers and stakeholders of a country. The team is responsible for the post-disaster recovery process and can decide to implement DRR measures. However, while some of these DRR measures can decrease risk of one hazard, they can increase the risk of another hazard. In each subsequent round, the team faces another (randomly selected) disaster. Unlike many other risk serious games, Breaking the Silos includes many random factors to better simulate reality. The roles are designed such that expert knowledge and objectives are spread throughout the participants and they can even be conflicting at times.

The game was successfully launched during the World Bank’s 2020 Understanding Risk conference. Before and after playing the game, participants were asked to complete surveys asking them about their perception of the challenges of Disaster Risk Management and whether the game raised their awareness of these challenges. The preliminary findings indicate that Breaking the Silos is a useful tool in supporting decision makers and practitioners to become aware of (the risks of) hazard-silo thinking and possible (a)synergies of DRR measures.
In-situ estimates of the role of radiative cooling for shallow convective organization
Authors: Fildier Benjamin , Muller Caroline , Touze-Peiffer Ludovic , Albright Anna Lea
Published: March 2021

This study investigates the role of radiative processes in shaping the spatial distribution of shallow clouds, using in-situ measurements retrieved during the EUREC4A field campaign. Horizontal gradients in atmospheric radiative cooling above the boundary layer had been advanced as important drivers of shallow circulation and low-level winds, through their effect on surface pressure gradients. Modeling studies first recognized their importance in idealized simulations of deep convection in radiative-convective equilibrium, then found a weaker role for idealized cases of very shallow convection; but recent work using remote-sensing data argued for their importance in strengthening the circulation close to the margin between dry and moist regions, on synoptic scales, arguing for a possible significance for these radiative effects on observed cloud structures.

Here we investigate cases of intermediate scale, observed during the EUREC4A field campaign, where shallow convection extends vertically up to 4 km, and whose spatial organization can be described on mesoscales as “fish” or “flower” patterns. We perform careful radiative transfer calculations, using state-of-the-art spectroscopic data and over two thousand of dropsondes and radiosondes launched, to capture the fine details of radiative cooling profiles usually missed by satellite measurements. The large number of sondes allows us to sample radiative cooling information for the organization pattern of interest and analyze it in conjunction with the direct wind and humidity measurements. We also use geostationary estimates of precipitable water in clear-sky in order to cross-check the sonde data, and connect them to the organization pattern and to the position of the moist margin.

Our results target the following relationships previously identified in idealized simulations: (a) between horizontal gradients in moisture and in top-of-the-boundary-layer radiative cooling, (b) between these radiative cooling gradients and surface wind anomalies across the moist margin, and (c) between the strength of surface winds as a function of the distance from the moist margin. These results will allow us to test the importance of radiative transfer processes in a real case of shallow convective organization.
Memory Properties in Cloud‐Resolving Simulations of the Diurnal Cycle of Deep Convection.
Authors: Daleu Chimene Laure
Published: March 2021

A series of high‐resolution three‐dimensional simulations of the diurnal cycle of deep convection over land are performed using the new Met Office NERC cloud‐resolving model. This study features scattered convection. A memory function is defined to identify the effects of previous convection in modifying current convection. It is based on the probability of finding rain at time t0 and at an earlier time t0−Δt compared to the expected probability given no memory. The memory is examined as a function of the lag time Δt. It is strongest at gray‐zone scales of 4–10 km, there is a change of behavior for spatial scales between 10 and 15 km, and it is reduced substantially for spatial scales larger than 25 km. At gray‐zone scales, there is a first phase of the memory function which represents the persistence of convection and it is maintained for about an hour. There is a second phase which represents the suppression of convection in regions which were raining 1 to 3 hr previously, and subsequently a third phase which represents a secondary enhancement of precipitation. The second and third phases of the memory function develop earlier for weaker forcing. When thermodynamic fluctuations resulting from the previous day are allowed to influence the development of convection on the next day, there are fewer rainfall events with relatively large sizes, which are more intense, and thus decay and recover more slowly, in comparison to the simulations where feedback from previous days is removed. Further sensitivity experiments reveal that convective memory attributed to these thermodynamic fluctuations resides in the lower troposphere.
A global decadal mode in a high-end climate model and in observations: Any connection to the solar cycle?
Authors: Ghil Michael , Feliks Yizhak , Small Justin
Published: March 2021

The present work addresses two persistent quandaries of the climate sciences: (i) the existence of global oscillatory modes in the coupled ocean–atmosphere system; and (ii) solar effects on this coupled system. Interannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here interannual-to-decadal variability over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR reanalysis, and apply multichannel singular spectrum analysis (MSSA) to these two datasets.

In the fully coupled CESM1.1 model, with its resolution of 0.1 × 0.1 degrees in the ocean and 0.25 × 0.25 degrees in the atmosphere, the ﬁelds analyzed are surface temperatures, sea level pressures and  the 200-hPa geopotential. The simulation is 100-yr long and the last 66 yr are used in the analysis. The two statistically signiﬁcant periodicities in this IPCC-class model are 11 and 3.4 yr.

In the reanalysis, the ﬁelds of sea level pressure and of 200-hPa geopotential are analyzed at its resolution of 2.5 × 2.5 degrees over the 68-yr interval 1949–2016. Oscillations with periods of 12 and 3.6 yr are found to be statistically signiﬁcant in this dataset. The spatio-temporal patterns  of the oscillations in the two datasets are quite similar. The spatial pattern of these  global oscillations over the North Paciﬁc and North Atlantic resemble the Paciﬁc Decadal Oscillation and the interannual variability found in the western North Atlantic, respectively.

The two global modes, with their 11–12-yr and 3.4–3.6-yr periodicities, are quite robust, suggesting potential contributions of both to predictability at 1–3-yr horizons. On the other hand, the CESM run has no year-to-year changes in the prescribed insolation, excluding any role of the solar cycle in the model’s 11-yr mode. The solar cycle is present, however, in the reanalysis, since it is present in nature and hence it does affect the observations. We speculate, therefore, that regional oscillations — with their distinct near-periodicities and spatial patterns — are synchronized  over the globe, thus yielding both the global oscillatory modes found in CESM. In nature, the decadal mode could be further synchronized with the solar cycle, but that does not seem to be the case, given the slight difference in period — 12 yr for the reanalysis and 11 yr for the solar cycle, which makes them drift in and out of phase.

The work’s tentative conclusion is, therefore: (i) yes, there are global oscillatory modes in the climate system, especially a decadal mode; but (ii) no, this mode has little or nothing to do with the solar cycle.
Numerical simulation of coupled processes in a single fracture employing a continuum approach
Authors: Vaezi Iman , Vilarrasa Víctor , Parisio Francesco , Yoshioka Keita
Published: March 2021

Fractures control fluid flow and the coupled geomechanical response of geological media in many geo-engineering applications. For instance, fractures dominate fluid flow and deformation in enhanced geothermal systems, underground radioactive waste repositories, and CO2 storage. Coupled thermo-hydro-mechanical processes in rock masses are a result of perturbations in the pore pressure, as in fluid injection and/or production, and/or temperature, as in cold fluid injection and disposal of radioactive waste. For example, fractures open as a result of pore pressure increase, which simultaneously increases permeability and reduces overpressure.

Geo-engineering and geo-energy applications involve a large portion of rock masses that include several fractures. Numerical computations of coupled processes occurring in rock masses while considering a large number of fractures pose several challenges. In this study, we firstly focus on a simple problem to fully understand the hydro-mechanical behavior of a single fracture subjected to a constant injection flow rate. We use the FEM software CODE_BRIGHT, which solves the thermo-hydro-mechanical governing equations in a fully coupled way. Since standard FEM can solve equations in continuum media, we investigate the behavior of a single fracture by analyzing the hydro-mechanical parameters that control the fracture response in a continuum fashion. However, simulating fractures with the real aperture is not simply feasible, hence, we search the equivalent properties of thicker fractures that are more feasible to be discretized in large-scale models with several fractures.

As the pore pressure increases inside a fracture, the fracture aperture increases and enhances its transmissivity. The embedded model uses variable permeability as a function of the cubic law. The simulation results show that a continuum approach can represent a fracture with a relatively large thickness (in the cm order) instead of the real aperture dimension (in the order of the micron).
The role of aerosol spatial inhomogeneity in mixed-phase deep convective clouds and torrential rain in urban areas
Authors: Lee Seoung Soo , Kim Byung-Gon , Li Zhanqing
Published: March 2021

This study examines the role played by aerosol in mixed-phase deep convective clouds and torrential rain that occurred in the Seoul area, which is a conurbation area where urbanization has been rapid in the last few decades, using cloud-system resolving model (CSRM) simulations. The model results show that the spatial variability of aerosol concentrations causes the inhomogeneity of the spatial distribution of evaporative cooling and the intensity of associated outflow around the surface. This inhomogeneity generates a strong convergence field and the associated spatial inhomogeneity of condensation, deposition and associated cloud mass, leading to the formation of torrential rain.  With the increases in the variability of aerosol concentrations, the occurrence of torrential rain increases. This study finds that the effects of the increases in the variability play a much more important role in the increases in the intensity of mixed-phase clouds and torrential rain than the much-studied effects of the increases in aerosol loading. Results in this study demonstrate that for a better understanding of extreme weather events such as torrential rain in urban areas, not only changing aerosol loading but also changing aerosol spatial distribution since industrialization should be considered in aerosol-precipitation interactions. 
Quantifying the interplay of clouds and their environment through an energetic lens during EUREC4A
Authors: Albright Anna Lea , Bony Sandrine , Stevens Bjorn , Vogel Raphaela
Published: March 2021

The trades form an important link in the atmospheric energy supply, transporting moisture and momentum to the deep tropics and influencing the global hydrological cycle. Trade-wind cumuli are the most ubiquitous cloud type over tropical oceans, yet models disagree in simulating their response to warming. Our study takes advantage of extensive in-situ soundings performed during the EUREC4A campaign, which took place in the downstream trades of the North Atlantic in winter 2020. We employ 1068 dropsondes made in a ca. 2deg x 2deg area to close the moisture and energy budgets of the subcloud layer and atmospheric column. Our motivation for closing moisture and energy budgets using EUREC4A data is two-fold. First, we try to understand which large-scale environmental factors control variability in subcloud layer moisture and moist static energy, given their influence on setting convective potential. Second, we quantify the interplay between clouds and their environment through an energetic lens. The cloud radiative effect emerges as a residual from the total column moist static energy budget, yielding an energetic estimate of clouds. We quantify how this cloud radiative effect compares with coincident satellite and geometric (i.e. cloud fraction) estimates of cloudiness, varies on different scales, and relates to large-scale environmental conditions.
Thermal simulation of cavity shape and its impact on solar and terrestrial radiation measurement in space
Authors: Tang Xiao , Zhu Ping , Goli Marta
Published: March 2021

In order to upgrade the technology readiness lever of the solar and terrestrial radiation measurement from space, in this paper, we started detailed thermal analysis and modeling of the Bolometric Oscillation Sensor (BOS) using the finite element method (FEM) [1]. Four cavity shapes (cylindrical, conical, inverted conical and hemispherical) are tested to compare their thermal and optical characteristics under different radiation and thermal environment, which helps to gain a better understanding of the mechanisms of BOS. We examined the absorptivity and emissivity of each cavity shape by applying the same amount of radiation power. Especially, when the ambient temperature maintains at a stable and low value, such as 20K, it produces the most accurate reconstruction of the input power. In this presentation, we will introduce the detailed simulation result and how to apply it to correct the ambient thermal radiation on each type of detector.

Reference:

[1] P. Zhu, M. Wild, M. van Ruymbeke, G. Thuillier, M. Meftah, and O. Karatekin. Interannual variation of globe net radiation flux as measured from space. J. Geophys. Res. doi:10.1002/2015JD024112, 121:6877-6891, 2016.

Acknowledgement: This work has been supported by the National Natural Science Foundation of China (NO. 41904163, 41974207), Natural Science Foundation of Hunan Province (NO. 2020JJ5483), and Research Foundation of Education Bureau of Hunan Province (NO. 18C0416). We also thank the financial support from China Scholarship Council (No. 201908430058).
Characterizing hydro-meteorological extremes from a societal perspective
Authors: Bogdanovich Ekaterina , Guenther Lars , Reichstein Markus , Ruhrmann Georg , Orth René
Published: March 2021

Extreme hydro-meteorological events often affect the economy, social life, health, and well-being. One indicator for the impact of extreme events on society is the concurrently increased societal attention. Such increases can help to measure and understand the vulnerability of the society to extreme events, and to evaluate the relevance of an event, which is important for disaster research and risk management. In this study, we analyzed and characterized hydro-meteorological extreme events from a societal impact perspective. In particular, we investigated the impact of heat waves on societal attention in European countries with contrasting climate (Germany, Spain, and Sweden) using Google trends data during 2010–2019. Thus, we seek to answer two general research questions: (i) how and when do extreme events trigger societal attention, (ii) are there temperature thresholds at which societal attention increases? 

To describe heat waves, we used maximum, minimum, average, and apparent temperature, aggregated to a weekly time scale. We analyzed the relationship between temperature and societal attention using piecewise regression to identify potential temperature-related thresholds in societal attention. The threshold is determined as the breaking point between two linear models fitted to data. We determined the corresponding goodness of fit by computing R2 for each temperature variable. The variable with the highest R2 is considered as the most influential one.

The overall relationship between temperature and Google attention to heat waves is significant in all countries and reveals clear temperature thresholds. The variable with the highest explanatory power is the weekly average of the daily maximum temperatures, which accounts for 71% of google attention in Germany, 51 % in Sweden, and 38 % in Spain. For Germany, similar results are found with media attention. In Sweden, with its colder climate, a lower temperature threshold is identified, indicating higher heat vulnerability. No significant impact of temperatures from the previous weeks is found. While further work is needed to improve the understanding of the attention-heat coupling, the demonstrated significant societal attention response to heat waves offers the opportunity to characterize heat waves from an impact perspective using the identified temperature variables, time scales, and thresholds.
Probabilistic Forecasts of Sea Ice Trajectories in the Arctic: Impact of Uncertainties in Surface Wind and Ice Cohesion
Authors: Cheng Sukun , Aydoğdu Ali , Rampal Pierre , Carrassi Alberto , Bertino Laurent
Published: March 2021

We evaluate the impact of uncertainties in surface wind and sea ice cohesion on sea ice forecasts by the neXtSIM sea ice model. neXtSIM includes the Maxwell-elasto-brittle rheology describing the ice dynamics. Ensemble forecasts are done every 10 days from January to April 2008. The ensembles are generated by perturbing the wind forcing and ice cohesion field both separately and jointly. The wind forcing, an external forcing of the model, is perturbed continuously during the forecast. While the sea-ice cohesion, an internal parameter of the model, is randomized on the initial field of each sea ice forecast. The model uncertainties are assessed statistically using ensemble forecasts, in which virtual drifters are seeded over the Arctic Ocean. We analyze the spread of Lagrangian sea ice trajectories of the ensemble of virtual drifters and compare them with the IABP buoys. We demonstrate that the wind perturbations usually contribute more to the forecast uncertainty, but the ice cohesion perturbations significantly increase the degree of anisotropy in the spread and become occasionally important during strong wind events.
Effects of energetic particles on the potential gradient measurements at different latitudes
Authors: Tacza José , Odzimek Anna , Kubicki Marek , Raulin Jean-Pierre
Published: March 2021

Energetic particles are potential candidates to affect the Global Electrical Circuit. This is supported by theoretical models that propose that these events can modify the conductivity profile above thunderstorms. If very strong, they can change the conductivity at low altitudes. We can study these effects through potential gradient measurements in fair weather regions. In this study, we investigate the potential gradient daily curve departures from the standard curve (mean curve in fair weather conditions) during very intense solar proton events and Forbush decrease. The superposed epoch analysis was utilized in order to enhance weak effects. Potential gradient data corresponds to the period between January 2008 and July 2019, and were recorded at two different stations located in different latitudes: CASLEO (Argentina, South Hemisphere) and Swider (Poland, North Hemisphere).
Implications of thermal disequilibrium during channelized melt-transport for the evolution of the lithosphere-asthenosphere boundary in intraplate settings
Authors: Roy Mousumi , Farmer Lang
Published: March 2021

This study explores how thermal disequilibrium during channelized melt-infiltration modifies the continental lithosphere from beneath. For this purpose, a 1D model of thermal disequilibrium between melt-rich channels and surrounding melt-poor material was developed, allowing us to estimate heat exchange across channel walls during melt transport at the lithosphere-asthenosphere boundary (LAB).  For geologically-reasonable values of volume fraction of channels (φ), relative velocity across channel walls (v), channel spacing (d), and timescale of episodic melt-infiltration (τ), disequilibrium heating may contribute >10-3 W/m3 to the LAB heat budget. During episodic melt-infiltration, a thermal reworking zone (TRZ) associated with spatio-temporally varying disequilibrium heat exchange forms at the LAB. The TRZ grows by the transient migration of a disequilibrium-heating front at material-dependent velocity, reaching a maximum steady-state width δ∼[φvd-2τ2]. The model results have implications for the Cenozoic evolution of the western US, specifically during the time period following the middle-Cenozoic ignimbrite flareup, and can be used to interpret a disparate set of previously published geophysical and geologic observations from the western US. The spatio-temporal scales associated with establishment of the TRZ in the models are found to be comparable with those inferred for the migration of the LAB based on geologic and petrologic observations within the Basin and Range province. More generally, the geochemistry of Cenozoic basalts across the region indicate a process in which melt-infiltration may have hastened the thinning and weakening of the lithosphere during and following the mid-Cenozoic ignimbrite flare-up, prior to Neogene extension.