bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulated regional dust cycle in the Carpathian Basin and the Adriatic Sea region during the Last Glacial Maximum
Authors: Ludwig Patrick , Gavrilov Milivoj B. , Markovic Slobodan B. , Ujvari Gabor , Lehmkuhl Frank
Published: March 2021

Different climate and environmental conditions dominated in the Carpathian Basin and the adjacent northern Italy/Adriatic region during the Last Glacial Maximum (LGM), as compared to today. For instance, high dust accumulation rates recorded in loess deposits point to an active dust cycle during the LGM. We investigated the climate conditions and regional dust cycle based on high-resolution (grid spacing of ~8.5 km) regional climate simulations for LGM conditions. The model output is in good agreement with proxy data, reproducing cold and dry conditions for the LGM. Highest dust emissions are simulated to the east of the Alpine ice sheet and in the Kvarner Bay region. While simulated dust deposition plumes in the northern Carpathian Basin indicate prevailing northerly (NW, N and NE) winds during dust events, strong Bora winds flowing down the slopes of the Dinaric Alps appear to play a major role in the local to regional dust cycle in the northern Adriatic region. From a seasonal perspective, the simulated dust cycle is most active during late winter and spring. A detailed analysis of climate and environmental conditions at key areas reveals that high wind speeds and low precipitation rates during late winter and spring correlate well with high dust emissions. In contrast, lower wind speeds, increasing precipitation, and the greening of vegetation prevent high dust emissions during summer and autumn. The occurrence of cyclonic circulation patterns in the Adriatic shelf region reveals that individual cyclones played an important role in transporting dust particles from the alluvial Po plain towards the eastern Adriatic loess deposition sites.
Wave-like solutions in Cosserat micropolar elasticity
Authors: Boehmer Christian
Published: March 2021

The Cosserat model generalises an elastic material taking into account the possible microstructure of the elements of the material continuum. In particular, within the Cosserat model the structured material point is rigid and can only experience microrotations, which is also known as micropolar elasticity. The propagation of elastic waves in such a medium is studied and we find two classes of waves, transversal rotational waves and longitudinal rotational waves, both of which are solutions of the nonlinear partial differential equations. For certain parameter choices, the transversal wave velocity can be greater than the longitudinal wave velocity.  We couple the rotational waves to linear elastic waves to study the behaviour of the coupled system and find wave-like solutions with differing wave speeds. In addition we also consider the so-called Cosserat coupling term. In this setting we seek soliton type solutions assuming small elastic displacements, however, we allow the material points to experience full rotations which are not assumed to be small.
Impact of a volcanic eruption on the sediment connectivity of a Chilean river basin: the Calbuco study case
Authors: Andreoli Marco , Martini Lorenzo , Cavalli Marco , Iroumé Andrés , Picco Lorenzo
Published: March 2021

Volcanic eruptions are natural disturbances capable of introducing large quantities of sediment into river systems as to upset the transport regime for several years. Such a disturbance can have a strong impact on the water and sediment flows and consequently on the transport capacity. Moreover, changes in morphological settings and land cover lead to an alteration of the sediment connectivity within the catchment. This study aims to investigate the changes of sediment connectivity in a catchment affected by an explosive volcanic eruption using the Index of Connectivity (IC) with a multi-temporal approach. Potential variations were analyzed at the catchment scale over a period of 6 years, before and after the eruption. The study area, located in southern Chile, is the Blanco Este River basin (39,6 km²), affected by the eruption of the Calbuco volcano (April 2015, total volume of sediment expelled of about 0,28 km³) which profoundly changed its vegetation cover, geomorphology and hydrology. IC analyses were based on low-resolution and freely available data (i.e., GDEM, Landsat 8 satellite images). Through supervised image classification and field data survey, a Manning's n coefficient for overland flow is derived as weighting factor (W) due to its suitability to represent the impedance to sediment flows in catchments characterized by land cover variations. Following the eruption, bare soil cover on the basin doubled (from 5% to 10% of total basin area). Consequently, the multi-temporal analysis results in an overall increase of IC with the median value ranges from -3,58 to -3,26 in pre-eruptive (2015) and first post-eruptive scenario (2016), respectively. The connectivity maps show that the higher IC values (i.e. range from -1,23 to 1,66) are persistently located in three areas: at the base of the volcanic dome, on the steepest slopes near the main channel and in a sub-basin on the right side of the catchment. Moreover, the Difference of IC (DoIC) among different scenarios highlighted the major variations. Such changes are found along the volcano slopes, in a flat area located in the upper part of the basin and along the lower valley of the Rio Blanco Este. The study proposes a useful methodology to evaluate the sediment connectivity, and its evolutionary trends, in environments affected volcanic eruptions starting from low-resolution data and field survey. These results may help to better define types, location and typologies of interventions to improve the river management approaches, considering the ongoing cascading processes. This research is funded by the Fondecyt 1200079 project.
Shannon Information of the geomagnetic field during the excursions
Authors: Campuzano Saioa A. , De Santis Angelo , Orlando Martina , Pavón-Carrasco F. Javier , Molina-Cardín Alberto
Published: March 2021

The Shannon Information or Information Content is a statistical measure of a system characterising its properties of organisation (maximum value) or disorder (minimum value). Once it is introduced the scalar potential of the geomagnetic field in terms of a spherical harmonic expansion, it is straightforward to define the Shannon Information by an expression including the Gauss coefficients [De Santis et al., EPSL, 2004]. Some recent models of the past geomagnetic field, including also the two most recent excursions, i.e. Laschamp (~41 ka) and Mono Lake (~34 ka) events, allow us to calculate the Shannon Information in the periods of those events and compare each other. It is expected that when approaching to excursions, the Shannon Information decreases, i.e. the disorder of the system increases. From the behaviour in time of the Shannon Information calculated from the Gauss coefficients of three geomagnetic field reconstructions that span the last excursions, i.e. IMOLE, GGF100k and LSMOD2, it is observed a decrease of the Shannon Information that seems to anticipate the occurrence of the impending excursions some time in advance. This result must be taken with caution because the reconstructions used are based on sedimentary data, which could present some smoothing effects related to the acquisition of the magnetisation mechanism.
The unidentified volcanic eruption of ~1809: why it remains a climatic cold case
Authors: Timmreck Claudia , Toohey Matthew , Zanchettin Davide , Brönnimann Stefan , Lundstadt Elin , Wilson Robert
Published: March 2021

The  "1809 eruption” is one of the most recent unidentified volcanic eruptions with a global climate impact. Even though the eruption ranks as the 3rd largest since 1500 with an eruption magnitude estimated to be two times that of the 1991 eruption of Pinatubo, not much is known of it from historic sources. Based on a compilation of instrumental and reconstructed temperature time series, we show here that tropical temperatures show a significant drop in response to the ~1809 eruption, similar to that produced by the Mt. Tambora eruption in 1815, while the response of Northern Hemisphere (NH) boreal summer temperature is spatially heterogeneous.  Here, we present the sensitivity of the climate response simulated by the MPI Earth system model to a range of volcanic forcing estimates constructed using estimated volcanic stratospheric sulfur injections (VSSI) and uncertainties from ice core records. Three of the forcing reconstructions represent a tropical eruption with approximately symmetric hemispheric aerosol spread but different forcing magnitudes, while a fourth reflects a hemispherically asymmetric scenario without volcanic forcing in the NH extratropics. Observed and reconstructed post-volcanic surface NH summer temperature anomalies lie within the range of all the scenario simulations. Therefore, assuming the model climate sensitivity is correct, the VSSI estimate is accurate within the uncertainty bounds. Comparison of observed and simulated tropical temperature anomalies suggests that the most likely VSSI for the 1809 eruption would be somewhere between 12 -19 Tg of sulfur. Model results show that NH large-scale climate modes are sensitive to both volcanic forcing strength and its spatial structure.  While spatial correlations between the N-TREND NH temperature reconstruction and the model simulations are weak in terms of the ensemble mean model results, individual model simulations show good correlation over North America and Europe, suggesting the spatial heterogeneity of the 1810 cooling could be due to internal climate variability. 
Deriving centimeter-level coseismic deformations and source parameters of small-to-moderate earthquakes from time-series Sentinel-1 SAR images
Authors: Luo Heng , Wang Teng , Wei Shengji , Liao Mingsheng
Published: March 2021

Small-to-moderate size earthquakes occur much more frequently than large ones but are general less studied by InSAR, despite that they also provide critical information about the physics of faulting and earthquake mechanisms. The weak coseismic deformations contaminated by severe atmosphere turbulences make them difficult to be studied by single interferogram. Since the launchings on April, 2014 and April, 2016, Sentinel-1 A/B satellites began to provide large-coverage SAR images in short revisited period (6 or 12 days) with 250 km frame width. The high-temporal sampling rate of Sentinel-1 data produce sufficient images for the stacking process to greatly reduce the local atmospheric turbulence that is difficult to be handled by numerical weather models. This procedure allows the extraction of very weak coseismic deformation (i.e. sub-centimeter) for small-to-moderate size earthquakes and systematical static slip inversions of the earthquakes in a tectonically active region by InSAR.

 

Here we report this stacking method and a new downsampling strategy based on quadtree mesh obtained from preliminary slip model to efficiently reduce the number of unwanted data points. Applying the proposed methods, we successfully retrieve coseismic deformations for 33 earthquakes (Mw4.1-Mw6.6) occurred in west China from Nov, 2014 to Jul 2020. Among these earthquakes, the smallest peak Line-of-Sight coseismic deformation is only ~6 mm. These InSAR-based earthquake catalogs show robust and precise absolute location (latitude, longitude and depth), therefore can be used as benchmark events to calibrate seismic based catalogues. However, strong trade-offs between earthquake source parameters (e.g. fault size vs slip) exist when the earthquake magnitude is small (in general smaller than Mw5.5). Such trade-offs are rooted due to the smaller deformation gradient in comparison with larger earthquakes. For the moderate size earthquakes (Mw6.0-6.6), the comparison between equivalent moment tensor from InSAR slip models and GCMT/W-phase solutions show that large CLVD components, as shown in the seismic-based moment tensor solutions, are mostly not necessary to explain the InSAR data. We suggest to combine geodetic and seismic datasets for more comprehensive and accurate earthquake source parameter inversions.
An analysis of the meteorological compound hazard of typhoons
Authors: Leckebusch Gregor , Ng Kelvin
Published: March 2021

An assessment of the compound hazard – extreme wind and extreme precipitation, of tropical cyclones (TCs) is of importance due to the enormous potential impact of TCs to the economic development and societal welfare of coastal regions.  Recently, a new method to construct a large physically consistent TC event set (roughly 10,000 years of events) based on numerical weather prediction models has been developed (Ng & Leckebusch, 2021).  However, a systematic method for the detailed analysis of the compound nature of the TC hazard with respect to damage relevant impacts is not yet available.  In this presentation, we propose a new metric, TC compound meteorological hazard risk index (CMRI) to assess TC compound meteorological hazard risk in terms of potential economic loss for mainland China.  CMRI considers TC-related extreme wind and extreme precipitation which are identified based on an impact-oriented tracking algorithm.  CMRI is closely linked to the normalised economic loss in China between 1979-2014.  We also present preliminary results of the application of CMRI in estimating the return period of the TC-related potential economic loss in mainland China.
Is Deep Learning more effective in detecting natural oil slicks? A comparison of semi-automated and AI techniques
Authors: Vrinceanu Cristina , Grebby Stephen , Marsh Stuart
Published: March 2021

Marine pollution has been traditionally addressed in Earth Observation studies through the use of Synthetic Aperture Radar (SAR) imagery. In operational processes, the contrast between the dark oil surfaces, characterized by a low backscatter return, and the rough, bright sea surface with higher backscatter has been exploited for decades.

Many of the processing techniques involve the use of semi-automatic workflows. Dark spot segmentation and feature classification are, undisputedly, common computational tasks. However, effective discrimination between oil slicks and other ocean phenomena (e.g. biogenic slicks, wind streaks, greasy ice) remains a challenge. To complete this task, a trained human operator is often employed in the final validation step. Thus, the process is time and resource consuming over large expanses, while the results are highly subjective. Automating this process and reducing computation and analysis time is the ultimate goal.

New algorithms based on the use of artificial intelligence for oil slick detection have recently emerged. While there are studies proving their effectiveness in successfully segmenting and classifying oil slicks, questions regarding their operational feasibility remain. Do they improve the quality of the detection? Are they more capable of discriminating between the various dark formations? What are the computational and data resources required for training, validation, and deployment of such an algorithm?

This project focusses on the development of a new customized algorithm for natural oil slicks detection. As part of this development, we analyzed the state-of-the-art methods and performed a comparison of the latest deep learning methods and classic semi-automatic techniques. Here, we present an in-depth analysis of selected segmentation and convolutional neural networks algorithms and various frameworks. The primary objective is to evaluate their effectiveness and expose their deficiencies for the detection and classification of natural oil slicks against anthropogenic pollution and other dark formation caused by ‘look-alikes’.

This presentation centers on the results that have been obtained by utilizing high-resolution open SAR data acquired by the Copernicus Sentinel-1 satellites. The evaluation is based on study sites located in the Black Sea, where two known oil seepage areas are actively generating consistent productive slicks as well as underdeveloped oil traces. 
Forecasting granular flow on steep terrains after interacting with an array of obstacles
Authors: Yang Su , Wang Xiaoliang , Liu Qingquan
Published: March 2021

Natural disasters such as landslides dominated by granular material may cause catastrophic consequences. Therefore, the protection of human-made facilities in mountainous areas is of great significance. An effective protective measure is to install an array of obstacles upstream of the structure that needs to be protected. We need to numerically simulate the interaction between granular flow and obstacle array, and forecast the flow path and stacking position of granular flow after interacting with an array of obstacles. The constitutive behavior and structure-interaction mode of granular material differs substantially from water flow-dominated hazards (e.g., floods). We have developed a depth-averaged model that can accurately simulate the interaction between granular flow and obstacles. Numerical simulations were performed for the case of granular flow facing a large number of different obstacles arrays to produce a dynamical process of granular flow and the depth changes of fixed detection points. We obtain different obstacles arrays by changing, including but not limited to, the type, geometric size of the obstacles, and row spacing of the arrays. We found that obstacles play roles of dissipation, deflection and hindrance, on the granular flow. For some types of obstacles, such as tetrahedron, the previous two mechanisms are dominant. Our research results show that the existence of obstacle arrays can indeed protect specific areas downstream. Furthermore, we can achieve better protection effects by changing the parameters of the array. These research results help us better forecast the result of the interaction between granular flow and an array of obstacles in space, and provide guidance for the structural design and assessment for hazard mitigation in mountainous regions. These findings advance the understanding of flow structures of fast granular flow facing obstacles, which provides guidance for structural design and assessment for hazard mitigation in mountainous.
A new mechanism for spontaneous imbalance exciting large-area gravity waves
Authors: Geldenhuys Markus , Preusse Peter , Krisch Isabell , Zülicke Christoph , Ungermann Jörn , Ern Manfred , Friedl-Vallon Felix , Riese Martin
Published: March 2021

In order to improve global atmospheric modelling, the trend is towards including source-specific gravity waves (GWs) in general circulation models. In a case study, we search for the source of a GW observed over Greenland on 10 March 2016 using the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) onboard the German research aircraft HALO. GLORIA is a remote sensing instrument where the measured infrared radiances are converted into a 3D temperature field through tomography. 
We observe a GW packet between 10 and 13km that covers ∼1/3 of the Greenland mainland. GLORIA observations indicate a horizontal (vertical) wavelength of 330km (2km) and a temperature amplitude of 4.5K. Slanted phase fronts indicate intrinsic propagation against the jet but the GW packet propagates (ground-based) with the wind. To find the GW source, 3D GLORIA observations, GROGRAT raytracer, ERA5 data, and an ECMWF numerical experiment are used. The numerical experiment with a smoothed topography indicates virtually no GWs suggesting that the GW field in the full model is caused by the orography. However, these are not mountain waves. A favourable area for spontaneous GW emission is identified within the jet exit region by the cross-stream ageostrophic wind speed, which indicates when the flow is not in geostrophic balance. Backtracing experiments (using GROGRAT) trace into the jet and imbalance regions. The difference between the full and the smooth-topography experiment is the change in wind components by the compression of air above Greenland. These accelerations and decelerations in the jet cause the jet to become out of geostrophic balance, which excites GWs by spontaneous adjustment. We present, to the best of our knowledge, the first observational evidence of GWs by this topography-jet mechanism.
Spatial evolution of turbulent regions associated with stream interaction regions in the solar wind
Authors: Kislov Roman , Sagitov Timothy , Malova Helmi
Published: March 2021

High-speed flows from coronal holes are separated from the surrounding solar wind by stream or corotating interaction regions (SIRs/CIRs). The latter have a complex dynamic structure, which is determined by turbulence, the presence of current sheets and magnetic islands/flux ropes/blobs/plasmoids. As the Sun rotates, SIRs along with high-speed flows propagate in the heliosphere. A SIR can be considered as a single large-scale object resembling a magnetic tube with walls of varying thickness. In this case, one can think not only about the speed of the plasma flow inside and near the given object, but also about its movement around the Sun as a whole. Because of this rotation, SIRs can cross the orbits of two separated spacecraft, which may allow one to study the spatial evolution of their structure. We have chosen the events when SIRs were sequentially detected by ACE and one of the STEREO spacecraft. In each case, a position of the Stream Interface (SI) was found, relative to which the position of other structures within the SIR was determined. Using a newly developed method for identifying current sheets [Khabarova et al. 2021], the SIR fine structure and the properties of turbulent plasma flow were studied. The estimates of the angular velocity of rotation SIR around the Sun are given. A model is constructed that describes the motion of SIRs in the heliosphere and their main large-scale properties.

Khabarova O., Sagitov T., Kislov R., Li G. (2021), http://arxiv.org/abs/2101.02804
Modeling of SEP induced auroral emission at Mars: Contribution of precipitating protons and effects of crustal fields
Authors: Nakamura Yuki , Terada Naoki , Nakagawa Hiromu , Sakai Shotaro , Hiruba Sayano , Kataoka Ryuho , Murase Kiyoka , Leblanc François
Published: March 2021

Solar Energetic Particle (SEP) and the Imaging UltraViolet Spectrograph (IUVS) instruments on board the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft have discovered diffuse aurora that spans across nightside Mars, which resulted from the interaction of Solar Energetic Particles (SEPs) with Martian atmosphere [Schneider et al., 2015]. Previous models showed that 100 keV monoenergetic electron precipitation should have been at the origin of the low altitude (~60 km) peak of the limb emission, however, no models were able to reproduce the observed emission profiles by using the observed electron energy population [e.g. Haider et al., 2019]. Previous auroral emission models did not take into account the contribution of MeV proton precipitation, although MeV proton can penetrate down to ~60 km altitude as well [e.g., Jolitz et al., 2017]. This study aims to model SEP induced diffuse auroral emission by both electrons and protons.

We have developed a Monte-Carlo collision and transport model of SEP electrons and protons with magnetic fields on Mars. We calculated limb intensity profile of CO2+ ultraviolet doublet (UVD) due to precipitation of electrons and protons with energy ranging 100eV-100keV and 100eV-5MeV, respectively, during December 2014 SEP event and September 2017 SEP event by using electron and ion fluxes observed by MAVEN/SEP, SWEA and SWIA.

The calculated peak limb intensity of CO2+ UVD due to precipitation of protons is 3-5 times larger than that due to precipitation of electrons during both December 2014 and September 2017 SEP events, which suggests that protons can make brighter CO2+ UVD emission than electrons. Peak altitude of limb intensity profiles of CO2+ UVD due to precipitation of electrons and protons are both 10 - 20 km higher than the observation, a discrepancy could be explained by the uncertainty in the electron and proton fluxes that precipitate into the nightside Mars.

We have tested an effect of crustal field on the emission of CO2+ UVD. CO2+ UVD emission due to the precipitating electrons are depleted by a factor of 10 in the region of open crustal field and disappeared in the region of closed and parallel crustal field, whereas emission due to the precipitating protons does not change significantly. Further observations of diffuse aurora in the crustal field region should be needed to constrain the origin of diffuse aurora on Mars.
A full decade (2009-2019) of continuous nightglow observations from the NUV to the NIR
Authors: Kausch Wolfgang , Noll Stefan , Kimeswenger Stefan , Moehler Sabine
Published: March 2021

The airglow emission of the mesopause region comprises molecular bands and atomic lines in the near-ultraviolet to the near-infrared wavelength range, e.g. the prominent roto-vibrational OH bands, a weak FeO/NiO continuum, the green OI line, the NaD doublet and some others. Since ground-based astronomical facilites observe through the Earth's atmosphere, the fingerprint of these emissions is visible in astronomical spectra taken with a telescope.
We have assembled a comprehensive data set of about 100,000 spectra in total taken between 1st of October 2009 and 30th of September 2019 with the X-shooter spectrograph, which is mounted at the Very Large Telescope in the Chilean Atacama desert (24.6°S, 70.4°W). This instrument provides medium-resolution spectra covering the entire wavelength range from 0.3 to 2.5μm simultaneously by incorporating three spectral subranges (UVB: 0.3-0.56μm; VIS: 0.56-1.02μm; NIR: 1.02-2.5μm).

The X-shooter instrument was continuously in operation during the covered period and frequently used by astronomers. Thus, the temporal coverage of the available observations is very dense for astronomical data allowing various airglow studies on time scales from minutes to a full decade. Due to the simultaneously observed wide wavelength range, individual airglow emitters as well as correlations between them can be investigated in detail (cf. Noll et al. 2021, this session, for more information).

In this presentation we describe the properties and the calibration of this unique data set.
Near crater observations of gas and aerosols variability at Mount Etna during the EPL-RADIO and EPL-REFLECT measurement campaigns.
Authors: Crumeyrolle Suzanne , Ranaivombola Marion , Roberts Tjarda , Giorio Chiara , Salerno Giusseppe , Giammanco Salvatore , Laspina Alessandro , Disarra Alcide , Spampinato Letizia , sellitto Pasquale
Published: March 2021

During the EPL (Etna Plume Lab) campaigns occurring in 2017 (EPL-RADIO) and 2019 (EPL-REFLECT),  gas  and aerosol measurements were performed  at Mount Etna (Sicily, Italy) to better assess the role of volcanic aerosols on both regional climate system and local health hazard. Gas related to volcanic emissions (such as SO2, H2S and others) were measured with low cost sensors (Alphasense) and HCl/SO2 ratio was validated in comparison to FTIR measurements. Aerosol physical and chemical properties were measured using low-cost Optical Particle Counters (OPCN2 from Alphasense) and filter measurements dedicated to organic acids, inorganic ions, soluble metals and total metals. During the EPL-REFLECT campaign, in-situ measurements were performed during: 1) the hike up, 2) a 2-hours period in the close vicinity of the Bocca Nuova crater, 3) the hike down and 4) in Milo (city on the flank of the Etna). Moreover, few OPCs were left unattended at the Bocca Nuova crater for two full days. 

 

Gas abundances at the crater-rim ranged from a few to 10’s ppmv SO2, with correlation to PM. The analysis of the 2 days measurements highlights a clear diurnal variation of aerosol size distributions. Indeed, at sunrise the total number and mass concentration is rapidly increasing from 15mg/m3 to 125mg/m3 in less than 2 hours. The variation of PM1/PM10 ratio shows a constant trend throughout the day except during a short period of time associated with high wind speeds. These results suggest that most aerosols are emitted through degassing and conversion of precursor gases to particles.

Moreover, analysis of aerosol samples collected on filters showed a change in metal solubility from the samples collected at the crater and the samples collected after atmospheric transport in Milo. This may indicate that the volcanic plume underwent processing in the aqueous phase during transport.
Power spectrum of hydraulic fractures with constricted opening
Authors: Dyskin Arcady , Pasternak Elena
Published: March 2021

Propagation of hydraulic fractures in rocks is often a non-smooth process, which leaves behind a number of rock bridges distributed all over the fracture. The bridges constrict the fracture opening and thus affect the determination of hydraulic fracture dimensions from the volume of pump-in fracturing fluid. This makes it necessary to detect the emergence of bridges and their concentration over the fracture surface.

Opening of hydraulic fractures in rocks is determined by a balance of pressure from the fracturing fluid and the normal component of the in-situ compressive stress. If an external excitation is applied (e.g. by a seismic wave), closure of the fracture is additionally resisted by the stiffness of fracturing fluid. Subsequently, a simple model of hydraulic fracture is presented by a bilinear spring with a certain stiffness in tension and a very high stiffness in compression. This constitutes so-called bilinear oscillator [1, 2] in which the compressive stiffness considerably exceeds the tensile one. The presence of bridges increases stiffness in tension thus reducing bilinearity of the modelling spring. Therefore the determination of the bilinearity is a first step in the reconstructing the effective stiffness of the bridges.  

We use the model of bilinear oscillator, identify multiple resonances and determine the first two harmonics (or first two peaks of in the power spectrum). The ratio of their amplitudes directly depends upon the bilinearity (ratio of compressive to tensile stiffnesses), hence the bilinearity is determinable from the amplitude ratio. Then the effective bridge stiffness can be estimated.

1. Dyskin, A.V., E. Pasternak and E. Pelinovsky, 2012. Periodic motions and resonances of impact oscillators. Journal of Sound and Vibration 331(12) 2856-2873. ISBN/ISSN 0022-460X, 04/06/2012.

2. Pasternak, E., A. Dyskinand Ch. Qi, 2020. Impact oscillator with non-zero bouncing point. International Journal of Engineering Science, 103203.

Acknowledgement. The authors acknowledge support from the Australian Research Council through project DP190103260.
Nordic Bioeconomic Pathways - catchment scale water quality impacts of various scenarios and projections 
Authors: Bhattacharjee Joy , Marttila Hannu , Juutinen Artti , Tolvanen Anne , Haara Arto , Karhu Jouni , Klöve Björn
Published: March 2021

The development, the alternative pathways for use of bioresources, can lead to plausible stressors in the future on forestry dominated catchments. It is needed to analyse the impact of regional future projections on different land system management (LSM) attributes. The catchment scale projections are downscaled from Nordic Bioeconomic Pathways (NBPs), the subsets of Shared Socioeconomic Pathways (SSPs). As a case study, the Simojoki catchment (3160 km2) in northern Finland has been considered where drained peatlands and forests dominate (53%) in the catchment. We integrated stakeholder-driven input, Finnish forest inventory model pathways (MELA) and hydrological catchment model (SWAT) to explore the future consequences of forest management practices for different NBP scenarios. We calibrated and validated water quality parameters in SWAT for the Simojoki catchment. Then, based on the output of MELA model of LSM attributes including stand management, catchment management strategy and fertilizer use, we used NBP scenario projections in SWAT model. We also included stakeholders’ evaluations of biomass removal at the time of harvesting at the Simojoki catchment. Additionally, climate imposing emission scenarios have been integrated into SWAT model to analyse longer perception of climate change (CC). The final outcomes of the proposed scenarios (NBP and/or CC) will portray the probable impacts on each LSM attribute in the Simojoki catchment, to adapt to the future forest management consequences.
Barriers and levers for implementing sustainable Nature-Based Solutions in cities
Authors: Duffaut Chloé , Frascaria-Lacoste Nathalie , Versini Pierre-Antoine
Published: March 2021

Hydro-meteorological risks are increasing and this could be due to global changes. These risks are particularly important in the urban context where most human beings live. Indeed, the impervious surfaces present in cities increase the risk of flooding, for example. Nature-Based Solutions can help to reduce these risks by creating permeable soils or storing water while promoting biodiversity. In this context, it is essential to understand what hinders the development and sustainability of these Nature-based Solutions in the city and what could help to deploy them on a large scale. For this purpose, various professionals working on Nature-Based Solutions in the city in France, were interviewed between 2020 and 2021, both in the academic and operational sectors, or even at the interface between the two: researchers in ecology or hydrology, IUCN (International Union for Conservation of Nature) project manager, project managers at the Regional Biodiversity Agency, director and natural environment manager of a watershed union, agro-economists engineer among others. They were asked what are the barriers and potential opportunities for Nature-Based Solutions implementation and sustainability in city. By analysing their answers, it emerges that the obstacles are more often cultural, political or financial than technical. The potential levers often mentioned are education and awareness-raising at all levels, especially for elected officials and the general public. Regulations such as the PLU (Local Urban Plan) and new funding for more natural spaces in the city also seem to be means of promoting Nature-based Solutions in urban areas. These interviews with diverse professionals directly involved in Nature-Based Solutions in cities allow to give real courses of action to be taken to democratize these Solutions throughout the French territory, or even internationally, and therefore ultimately reduce the risks of hydro-meteorology. This is one of the objectives of the French ANR project EVNATURB (Assessment of ecosystem performance of a renaturation of the urban environment), in which this study has been carried out.
Laboratory experiments on secondary ice production upon free falling drizzle droplets observed by high speed video and thermal imaging
Authors: Keinert Alice , Kleinheins Judith , Kiselev Alexei , Leisner Thomas
Published: March 2021

During the freezing of supercooled drizzle droplets, the ice shell forms at the droplet surface and propagates inwards, causing a pressure rise in the droplet core. If the pressure exceeds the mechanical stability of the ice shell, the shell can crack open and eject secondary ice particles or cause the full disintegration of the ice shell leading to droplet shattering. Recent in-cloud observations and modeling studies have suggested the importance of secondary ice production upon shattering of freezing drizzle droplets. The details of this process are poorly understood and the number of secondary ice particles produced during freezing remains to be quantified.

Here we present insight into experiments with freezing drizzle droplets levitated in electrodynamic balance under controlled conditions with respect to temperature, humidity and airflow velocity. Individual droplets are exposed to a flow of cold air from below, simulating free fall conditions. The freezing process is observed with high-speed video microscopy and a high-resolution infrared thermal measuring system. We show the observed frequencies for various events associated with the production of secondary ice particles during freezing for pure water droplets and aqueous solution of analogue sea salt droplets (300 µm in diameter) and report a strong enhancement of the shattering probability as compared to our previous study (Lauber et al., 2018) conducted in stagnant air. Analysis of pressure release events recorded by high-resolution infrared thermography suggest that pressure release events associated with the possible ejection of secondary ice particles occur far more frequent than previously quantified with observations by high speed video microscopy only.

 

Lauber, A., A. Kiselev, T. Pander, P. Handmann, and T Leisner (2018). “Secondary Ice Formation during Freezing of Levitated Droplets”, Journal of the Atmospheric Sciences 75, pp. 2815–2826.
Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) Mission: Advanced Hyperspectral and Multi-Angular Polarimetric Satellite Observations for Science-driven Applications
Authors: Scott Joel , Urquhart Erin
Published: March 2021

The next great contribution from NASA to study the Earth’s ecosystems, including the open ocean and coastal and inland waters, is the PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) mission. PACE will build upon the remote sensing legacy that NASA earth science has established with over four decades of satellite instruments beginning with CZCS (Coastal Zone Color Scanner) launched in 1978 and following with SeaWiFS (Sea-viewing Wide Field-of-view Sensor), MODIS (Moderate Resolution Imaging Spectroradiometer), and VIIRS (Visible Infrared Radiometer Suite). PACE is expected to launch in 2023 and will carry the hyperspectral Ocean Color Instrument (OCI), as well as two multi-angle polarimeters (SPEXone and HARP-2). OCI will provide an unprecedented view of the entire earth every two days.

This presentation will highlight the capabilities of the novel hyperspectral and multi-angular polarimetric instruments on onboard the PACE observatory, showcasing PACE’s ability to fill societal needs and enable decision-making, in support of advanced climate observations, optimized biothreat assessment, food security support and assurance, and sustainable fishery and aquaculture monitoring and prediction for the benefit of humanity and its next generations. PACE will continue heritage MODIS and VIIRS visible, near-infrared, and shortwave-infrared data products at 1 km resolution, as well as produce new hyperspectral and multi-angular polarimetric advanced data products, not possible with MODIS and VIIRS due to their design and technological limits. PACE will leverage emerging remote sensing technologies to advance aquatic and atmospheric remote sensing in ways that fulfill real-world needs.
China's Carbon Budget
Authors: Ke Piyu , Liu Zhu , Li Wei , Guo Xianghui , Dai Minhan , Deng Zhu , Zhu Biqing , Guo Rui , Tan Jianguang
Published: March 2021

Combining updated methodology and data from different sources, we reported the estimates of China's carbon budget, including carbon sources from fossil fuel combustion and industrial process, and carbon sinks from terrestrial and marine systems. China's carbon budgets provide insights on the temporal and spatial distribution of the uptake of atmospheric carbon dioxide, and can be used to evaluate carbon cycle models and to define baselines for supporting China's climate policies and mitigation efforts. So far, we have found that terrestrial carbon sinks of China have increased significantly in the past 70 years with the development of afforestation projects in China. Seas of China have gradually transformed from carbon sources to carbon sinks.
Towards an ocean biogeochemical modelling framework for long-term transient simulations with a focus on the Eastern Mediterranean Sea 
Authors: Six Katharina , Mikolajewicz Uwe
Published: March 2021

Sediment archives of the Eastern Mediterranean Sea (EMed) indicate very different physical and biogeochemical conditions during the LGM and the early Holocene than for present day. The ultimate goal of the here presented project is to disentangle the controlling processes of the circulation in the EMed over the last deglacial period by applying a regional ocean model including biogeochemistry covering the entire Mediterranean Sea. This model setup will be driven by downscaled forcing fields from a simulation with the paleo version of Max Planck Institute Earth System Model (pMPI-ESM) spanning from 26 to 0 kaBP.  pMPI-ESM has unique features like automatic bathymetry adjustment due to sea level rise and transient river routing. Despite its coarse model resolution, pMPI-ESM simulations catch the humid period of the early Holocene with corresponding increased Nile river discharge, a relevant driver for the conditions in the EMed. Thus, we are convinced that pMPI-ESM can provide a long-term transient and consistent forcing which is appropriate for our aims.

Here we present first results to evaluate the performance of our regional model driven by the downscaled forcing from pMPI-ESM. Main characteristics of the present day Mediterranean circulation are well captured such as locations of deep water formation, Mediterranean and Black Sea fresh water budgets, and the baroclinic transports through the Strait of Gibraltar.  We test our model framework for different time slices of deglaciation.
A new ice core from the Eastern Summit of Mt. Elbrus, Caucasus, Russia
Authors: Kutuzov Stanislav , Mikhalenko Vladimir , Lavrantiev Ivan , Toropov Pavel , Vladimirova Diana , Abramov Andrey , Matskovsky Vladimir
Published: March 2021

Meteorological regime and glacier surface heat balance, GPR measurements of the ice thickness and seasonal snow cover were investigated in the crater of the Eastern Summit of Mt. Elbrus In the period from 18 to 30 August 2020 at 560 m a.s.l. On the base of preliminary data analysis, the predominance of fluctuations in the synoptic scale over the diurnal ones was revealed; high values of the average and maximum wind speed associated with the influence of jet currents and with the effects of leeward storms were identified; extremely high temporal variability of relative humidity and its very high deficit in cloudless conditions, which contributes to intensive evaporation and sublimation from the snow surface, were explored. The maximum ice thickness in the crater reaches 100 m, with an average of 45 m. A new 96.01 m ice core from glacier surface to bedrock has been recovered. The drilling speed varied from 11 to 1 m / h, decreasing on average with depth from 4.5 to 4.0 m / h. The thickness of the snow-firn strata is about 20 m, which is three times less than on the Western Plateau. The borehole temperature was measured. The temperature on the glacier bedrock was -0.6 °С. The calculated heat flux was 0.39 W/m2. Air sampling was carried out in the crater of the Eastern Summit of Elbrus and on the Garabashi glacier. The repeated measurement of the soil temperature in the fumarole field on the Elbrus Eastern Summit outer crater rim suggests that the temperature regime is stable.

The research was carried out on the territory of the Elbrus National Park with the financial support of the Russian Science Foundation (project 17-17-01270).
A seasonal assessment of urban outdoor thermal exposure in a humid continental climate using the MaRTy observational platform
Authors: Aiello Tim , Krayenhoff Scott , Middel Ariane , Warland Jon
Published: March 2021

Many cities in the northern hemisphere experience both extreme heat and extreme cold weather. Pedestrians are exposed to these thermal extremes, causing bodily stress. With a growing and ageing urban population, city design that contributes to the mitigation of summer heat exposure while also reducing winter cold exposure is of increasing importance. Pedestrian thermal exposure depends on several microclimatic factors in addition to air temperature, including wind speed, humidity, as well as shortwave and longwave radiation, which can be quantified by the mean radiant temperature (Tmrt). There has been little study of the impacts on pedestrian thermal exposure in climates with high humidity during summer and snow cover in the winter. We gathered seasonal radiation data from varied urban microclimates using the six-directional Tmrt method in a Canadian city. We deployed a mobile human-biometeorological weather station (MaRTy cart), which has previously been used primarily in hot, dry climates. Tmrt profiles are decomposed into their directional components, and they demonstrate substantial differences in the drivers of thermal exposure between seasons and locations within the city.
Ten years of the Wind Atlas of South Africa: Final results from WASA 3
Authors: Hahmann Andrea , Lennard Chris , Floors Rogier , Cavar Dalibor , Mortensen Niels G. , Olsen Bjarke T. , Prinsloo Leon , Bechmann Andreas , Davis Neil , Hansen Jens Carsten
Published: March 2021

We present the evolution of the methods used to create and validate the various numerical wind atlases during the past ten years of the Wind Atlas for South Africa (WASA) project. In WASA 3, we improved on the previous numerical wind atlases by:

Creating an ensemble of 2-year simulations to find the optimal set of parameterisations and surface conditions for the wind climate of South Africa.

Using a new method of generalisation and downscaling of the WRF-derived wind climate using the PyWAsP engine.

Producing the most extensive to date wind climatology for South Africa, 30 years (1990–2019) simulation covering all South Africa at 3.33 km × 3.33 km spatial resolution and 30 minutes time output.

We will discuss these three areas and their improvements to the wind atlas' quality. The WASA 3 wind atlas' final error statistics show that the new WRF + PyWAsP method has a MAPE of 11.8% and 3.5% for the long-term mean power density and mean wind speed, respectively. These statistics are improved from those in WASA 1 and WASA 2.

When disregarding the two masts (WM09 and WM11) located in highly complex terrain, where the methodology was never designed, the use of the WRF and WRF + PyWAsP downscaling narrows the error distributions for both long-term wind speed and power density compared to the global reanalysis, ERA5.

The validated numerical wind atlas has further been used to model the wind resources of the entire land area of South Africa using the microscale WAsP model. Raster data exist with a horizontal resolution of 250 meters and three levels of 50, 100 and 150 meters a.g.l. of mean wind speed, power density, air density, Weibull A and k parameters, and ruggedness index.  These data sets and the WRF dataset will be made available in the public domain at the end of the project. Data sets for other heights above the ground and offshore can easily be added later.