bluuebunny/crossref_metadata_2025 huggingface dataset:
Compound high temperature and low net primary production extremes in the ocean over the satellite period
Authors: Legrix Natacha , Zscheischler Jakob , Laufkötter Charlotte , Rodgers Keith , Rousseaux Cecile , Yamaguchi Ryohei , Frölicher Thomas
Published: March 2022

Extreme events, such as marine heatwaves (MHWs), severely impact marine ecosystems. Of particular concern are compound events, i.e. situations when conditions are extreme for multiple ecosystem stressors, such as temperature and net primary productivity (NPP). In 2013-2015 for example, an extensive MHW, known as the Blob, cooccurred with low NPP and severely impacted marine life in the northeast Pacific, with cascading impacts on fisheries. Yet, little is known about the distribution and drivers of compound MHW and low NPP extreme events. We use satellite-based sea surface temperature and NPP estimates to provide a first assessment of these compound events. We reveal hotspots of compound MHW and low NPP events in the equatorial Pacific, along the boundaries of the subtropical gyres, and in the northern Indian Ocean. In these regions, compound events that typically last one week occur three to seven times more often than expected under the assumption of independence between MHWs and low NPP events. At the seasonal timescale, most compound events occur in summer in both hemispheres. At the interannual time-scale, their frequency is strongly modulated by large-scale modes of climate variability such as the El Niño-Southern Oscillation, whose positive phase is associated with increased compound event occurrence in the eastern equatorial Pacific by a factor of up to four. Using large ensemble simulations of two Earth system models, we then investigate the exact physical and biological drivers of these compound events. We find that both models suggest that MHWs in the low latitudes are often associated with low surface ocean nutrient concentrations due to enhance stratification and/or reduced upwelling, which limits the growth of phytoplankton resulting in extremely low NPP. However, the models show large disparities in simulated compound events and its drivers in the high latitudes. This identifies an important need for improved process understanding for high latitude compound MHW and low NPP events.
Divergent response of plant-derived lipids and fire-derived organic matter to warming and elevated CO2 in a boreal peatland.
Authors: Nicholas Ofiti , Cyrill Zosso , Paul Hanson , Guido Wiesenberg , Michael Schmidt
Published: March 2022

Peatlands occupy ~3% of the land surface, yet they store more than one-third of global terrestrial carbon. However, there is growing concern that the decomposition of this vast carbon bank in the face of climate change could alter peatlands from a carbon sink to a carbon source, but experimental data is scarce. Here, we examine peatland carbon stability after four years of whole-ecosystem warming (+0, +2.25, +4.5, +6.75 and +9 °C) and two years of elevated CO2 manipulation (500 ppm above ambient). We use solvent-extractable (alkanoic acids, alkanols and alkanes) and hydrolysable lipids (cutin and suberin) and benzene polycarboxylic acids (BPCA) as tracers for fire-derived organic matter and investigate their degree of decomposition in a boreal forested peatland.

We found fire-derived organic matter stemming from past fires, either nearby or long-distance atmospheric transport. Warming alone or when combined with elevated CO2 did not affect the quantity and quality of fire-derived organic matter stemming from past fires, as indicate by the molecular markers BPCA. The wet conditions probably helped to preserve these slowly degrading aromatic compounds. Molecular markers for leaf- (cutin) and root‐derived biomass (suberin), showed that with warming more new plant biomass came from roots, at the expense of leaf-derived compounds under both, ambient and elevated CO2 treatments, implying dynamic alterations to leaf and root carbon incorporation and sequestration with environmental changes. These responses were more pronounced in the surface aerobic acrotelm, highlighting that the aerobic layer responded surprisingly fast, within a few seasons to changing environmental conditions.
In-situ observation, modeling and analysis for water and energy parameters over the Tibetan Plateau
Authors: Ma Weiqiang , Ma Yaoming , Han Yizhe , Hu Wei , Zhong Lei , Xie Zhipeng , Hu Zeyong , Su Rongmingzhu , He Jianan , Ma Weiyao , Bai Ling , Sun Fanglin
Published: March 2022

Tibetan Plateau Observation Platform (TORP), Third Pole Environment (TPE) observation and research Platform (TPEORP) and new stations were set up in recently years.
Firstly, based on the difference of model and in-situ observations, a serious of sensitive experiments were done by using numerical model, Such as Noah-MP and WRF. Better schemes in ground temperature and soil water content at shallow layer simulation were selected by comparing with Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature and Soil Moisture Active Passive (SMAP) soil moisture data. In order to use remote sensing products, a land-atmosphere model was initialized by ingesting land surface parameters, such as AMSR-E RS products, and the results were compared with the default model configuration and with in-situ long-term CAMP/Tibet observations. 
Secondly, we analyzed the spatiotemporal variation characteristics of the heating field in the Tibetan Plateau through the observation data and reanalysis data and then revealed the influencing factors and potential effects of the changes of atmospheric heat sources on the Tibetan Plateau in summer and winter. Finally, the relationship between the change of spring AHS in the Tibetan Plateau and the change of summer precipitation in Northeast China was also analyzed from the level of mathematical statistics.
Thirdly, based on historical observations daily data for 1981-2016 from 130 meteorological stations over and around the Tibetan Plateau , the trends of sensible heat flux (SH) and their elevation-dependence were investigated. Results indicate that the SH over and around the Tibetan Plateau experienced apparent trends’ shift in approximate 2000, demonstrating noticeable reductions during 1981-2000 and pronounced recovery during 2001-2016 for the four seasons.
All of the different methods will clarify the water and energy parameters in complex plateau, it also can affect atmospheric cycle over the Tibetan Plateau even all of the global atmospheric cycle pattern.
Confirmation of the probabilistic seismic hazard assessment by the Taiwan Earthquake Model through comparison with strong ground motion observations
Authors: Chan Chung-Han , Gao Jia-Cian , Tseng Yi-Hsuan
Published: March 2022

To confirm the probabilistic hazard assessment proposed by the Taiwan Earthquake Model (TEM), we compared it with the strong ground motion observations. We accessed the Taiwan Strong Motion Instrumentation Program (TSMIP) database and reported the maximum ground shaking of each strong-motion station. Comparing the TSMIP observations and the TEM hazard model reveals similar spatial patterns. However, some records indicate significantly higher shaking levels than the model does due to the occurrence of some large events, for example, the 1999 Mw7.6 Chi-Chi earthquake. Such discrepancies cannot be explained by model parameter uncertainties but by unexpected events in the given short observation period. We have confirmed that although each seismogenic structure in Taiwan is unlikely to rupture within a short period, the summarized earthquake potentials from all the structures are significant. Additionally, we discuss the impacts of some model parameters, including epistemic uncertainties of source parameters, truncation of standard deviation for ground motion prediction equations, the Gutenberg-Richter law for area source, and the time-dependent seismicity rate model. The outcomes of this study provide not only crucial information for urban planning on a city scale and building code legislation on a national scale, but also suggestions for the next generation of probabilistic seismic hazard assessment for Taiwan as well as other regions.
How does dry air influence the precipitation of landfalling tropical cyclones
Authors: Shu Shoujuan
Published: March 2022

The vertical structure of precipitation and its evolution during mid-level dry-air intrusion (DAI) for landfalling tropical cyclones (LTCs) over China in the past 10 years were examined using several observed TRMM PR products and a reanalysis dataset. We show that in the outer region where the environmental mid-level dry air intrudes more easily, the process of environmental DAI has an important effect on the vertical structure and precipitation of LTCs through promoting substantially stratiform precipitation while inhibiting infrequent intense convective precipitation. Although the total mean rain rate does not change much during the DAI period, both the mean rain rate and area of stratiform precipitation are almost doubled, while the convective precipitation halves compared to the situation prior to the DAI period. Also, the vertical structure of precipitation relative to the vertical wind shear (VWS) is modulated by the dry air, with a clear stratiform precipitation structure in the DAI region, though the dry-air distribution of LTCs does not depend on the direction of the VWS but rather on the synoptic environmental collocation. Further analysis shows that the mid-level DAI is favorable to the generation of stratiform precipitation through producing moderate mid-level convergence and less intense low-level subsidence, which contribute to the mid-level spin-up without spinning down the low-level circulation. At the same time, it helps maintaining the uniform stratiform precipitation above the melting layer and homogenizing the low-level circulation, and thus boosts the development of stratiform precipitation in intensity and area in the outer region.
Modelling magneto-hydro-static equilibria in quiet Sun regions
Authors: Wiegelmann Thomas , Madjarska Maria
Published: March 2022

The solar magnetic field is measured routinely only
in the solar photosphere. While reliable measurements
of the photospheric magnetic field vector are only available
in active regions, in the quiet Sun at present only
 the vertical component of the magnetic field can be obtained accurately.
 To derive magnetic field structures throughout the solar atmosphere, from
 the chromosphere to the corona, we extrapolate these photospheric measurements
into the upper photosphere, chromosphere and corona with a magneto-hydro-static
model. We optimize free model parameters by comparing the modelled magnetic
field lines with structures observed in solar images. The comparison is
done automatically with a number of quantitative measurements and
the optimal model parameters are found with the help of
a downhill simplex minimization. This newly developed modelling approach can
provide an accurate and deep understanding of the magnetic field structures
that extend to any height in the solar atmosphere.
Machine learning based multipath mitigation for high-precision GNSS data processing
Authors: Pan Yuanxin , Möller Gregor , Hohensinn Roland , Soja Benedikt
Published: March 2022

Multipath is the main unmodeled error source hindering high-precision GNSS (Global Navigation Satellite System) data processing. Classical multipath mitigation methods, such as sidereal filtering (SF) and multipath hemispherical map (MHM), have certain disadvantages: they are either too complicated for implementation or not effective enough for multipath mitigation. In this study, we demonstrate that machine learning (ML) based models, such as random forest, can overcome these drawbacks by spatial interpolation over sky map and thus mitigate multipath effectively. 30 days of 1 Hz geodetic grade GPS data as well as 6 days of low-cost data are used to train and test the ML models. Based on a series of test cases, the best number of days for model training and the validity period for the models are discussed in this contribution. For quantification, the multipath reduction rate and kinematic positioning precision are computed using different ML models and compared to those derived from SF and MHM. The statistical results show that the XGBoost ML model can achieve higher multipath reduction rates compared to SF and MHM, especially for pseudorange measurements, which is important for low-cost devices. It reduces the multipath by 48% and 55% for pseudorange and carrier phase measurements, respectively, and outperforms SF (40% and 52%) and MHM (37% and 49%). The positioning precision when using different multipath models is similar, with differences of less than 1 mm. We conclude that the ML based multipath mitigation method is effective and easy-to-use, which can be applied under real-time scenarios.
Communicating about wetlands to the audiences: what do the experts think?
Authors: Matias Ana , Pinto Bruno , Carrasco Ana Rita
Published: March 2022

Understanding and managing wetlands is a matter of great importance, given the fragile nature of its habitats, survival issues under perturbation, and the need for sustainable use of its resources when competing with human print. These are environments particularly sensitive to a number of physical factors and they’re particularly suited to engage with climate change (e.g. sea-level rise and rising temperature), conservation (e.g., biodiversity, land-use management), and ecosystem services (e.g., carbon storage and water purification). Wetlands deserved raising interest in the last two decades by the scientific community, such as the ecogeomorphologic nature of its dynamics, value and resilience to natural and human drivers, and timescales of change. This interest is reflected in the existence of four EGU Assembly 2022 proposed sessions (BG2.3, GM6.2, GM6.3, GM6.4) particularly devoted to wetlands, where both natural and social perspectives can fit. Given both the scientific and the societal relevance of wetlands, how does communication between both spheres is or should be made? What do the experts think about this? Are they aligned with the deficit model and/or the dialogue model of science communication? This is the underlaying rationale for this study.

We propose to enquire the dozens of coastal experts attending EGU 2022 conference about the science communication of wetlands. Questions about wetland communication include, for example (not comprehensively): 1) What are the key topics to communicate about wetland for audiences; with questions discriminating adult, children (8-12 y) and teenagers (13-17y)? 2) Choose the two most important wetlands threatening factors to communicate; And the two least important factors. 3) Is knowing about coastal evolution more relevant than knowing the names of the most emblematic vegetation species? 4) What is the most usual way that you use to communicate about wetlands to the public?

We will collect data on wetland communication via an online questionnaire, with mostly closed-ended questions to allow a quicker analysis. We propose that a group of EGU attendees fill in the online questionnaire two days before and the first two days of the conference. The completion of the questionnaire allows anonymity. Fresh results from the survey will be presented and used as a base ground starting point for a discussion with conference participants about their own opinions.
Improved models, improved information? Exploring how climate change impacts pollen, influenza, and mold in Berlin and its surroundings
Authors: Langendijk Gaby , Rechid Diana , Jacob Daniela
Published: March 2022

Urban decision makers rely on evidence-based climate information tailored to their needs to adequately adapt and prepare for future climate change impacts. Regional climate models, with grid sizes between 50-10 km, are a useful outset to understand potential future climate change impacts in urban regions. The recently developed convection-permitting models have grid sizes less than 5 km, and better resolve smaller scale atmospheric processes such as convection, and its interactions with the land surface, by also better representing complex terrain, for instance cities. This study investigates how the convection-permitting resolution affects the simulation of climate change conditions in the urban-rural context, demonstrated through three impact cases: influenza spread and survival; ragweed pollen dispersion, and in-door mold growth. Simulations by the regional climate model REMO are analyzed for the near future (2041-2050) under emission scenario RCP8.5. Taking the Berlin region as a testbed, the findings show that the change signal reverses for the 3 km compared to the 12.5 km grid resolution for the impact cases pollen, and mold, which indicates an added value. More pollen days are projected in Berlin under future climate conditions. Less mold days can be expected, but longer consecutive periods, under future climate conditions. For influenza, the convection-permitting resolution intensifies the decrease of influenza days, nevertheless longer periods of consecutive influenza days are found under near-term climate change. The results show the potential of convection-permitting simulations to generate improved information about climate change impacts for urban regions to support decision makers, and in order to build the resilient cities of tomorrow. 

 
Geomorphic Heterogeneity in River Corridors as a Source of Resilience to Changing Climate
Authors: Wohl Ellen
Published: March 2022

A river corridor includes the active channel(s), floodplain, and underlying hyporheic zone. Geomorphic heterogeneity refers to the spatial distribution of geomorphic units within the river corridor. Heterogeneity can be conceptualized at different spatial scales, from bedforms such as pools and riffles in the active channel, to the distribution of subsurface paleochannels across the entire floodplain. Essentially, geomorphic heterogeneity describes the extent to which the river corridor is spatially non-uniform in the three dimensions of vertical, lateral, and longitudinal. Heterogeneity results from erosion and deposition caused by temporal and spatial variations in both inputs and boundary resistance, as well as modifications created by biota such as riparian vegetation or beavers (Castor spp.). In many river corridors, these variations and biotic influences reduce longitudinal connectivity but enhance lateral and vertical connectivity within the river corridor. Resilience is the ability to absorb disturbances without diminishing or changing river corridor function. Resilience can be conceptualized as occurring along a continuum dependent on time and space scales, especially when applied to a system such as a river corridor that includes individual components with different levels of resilience. Changing climate will affect averages and extremes such as floods and wildfires. I use case studies from mountain streams in Colorado, USA to illustrate how a geomorphically heterogeneous river corridor is more resilient to extremes of high and low flow and large inputs of either sediment or solutes. Geomorphic heterogeneity promotes resilience because the spatial non-uniformity of the river corridor provides more opportunities for transient storage over diverse timespans, which attenuates downstream fluxes, and diffuses the energy inputs resulting from a disturbance.
Drivers of Dense Shelf water formation in East Antarctic polynyas
Authors: Portela Rodriguez Esther , Rintoul Stephen R. , Herraiz-Borreguero Laura , Roquet Fabien , Tamura Takeshi , van Wijk Esmee , Bestley Sophie , McMahon Clive , Hindell Mark
Published: March 2022

Coastal polynyas are key regions of Dense Shelf Water (DSW) formation that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. In this study, we analyse the main drivers of DSW formation in four East Antarctic polynyas: Mackenzie, Barrier, Shackelton and Vincennes Bay from west to east. Mackenzie and Barrier (in lesser extent) were the only two polynyas where DSW formation was observed while it is absent in Shackelton and Vincennes Bay in the particular years when they were best sampled. We analysed the role of Bathymetry, water-mass distribution and transformation, stratification of the water column, sea-ice production rate and associated salt advection. We found that sea ice production was highest in Mackenzie, particularly in early winter, which likely contributed to reach higher salinity than the other polynyas at the beginning of the sea ice formation season. From April to September, the total salinity change in Mackenzie polynya was lower than in the other polynyas, and the strong contribution of the brine rejection was partly offset by freshwater advection. Overall, the preconditioning in early winter in Mackenzie polynya, likely due to strong SIP in February and March was the main driver determining DSW formation in MAckenzie in contrast with the other East Antarctic polynyas.
The abnormal 1/f2 spectral falloff caused by asymmetric friction
Authors: Wong Rui Xiang , Pasternak Elena , Dyskin Arcady
Published: March 2022

Asymmetric friction refers to different friction forces that resist sliding in opposing directions. Asymmetric friction can for instance be induced by an anisotropic block with an anisotropy axis inclined to the direction of sliding progressing in a constraint environment, (Bafekrpour et al., 2015). This study examines a Burridge-Knopoff-type model of multiple blocks connected through springs. Each block is connected to an external oscillating surface through a leaf spring; some blocks slide with asymmetric friction, while others experience conventional symmetric friction. Asymmetric friction favours slip in the direction of low friction. This increases spring forces to counteract the slip within the assembly, creating regions of tension and compression. When this model represents geological faults, regions of tension and compression can produce fractures oriented normal (in the tensile phase) or parallel (in the compressive phase) to the sliding surface.

Velocity spectra produced by the model excited by an external oscillating surface reveal that the presence of asymmetric friction creates spectra with a frequency falloff of 1/f2, where f is the frequency. This is in contrast with the case of only symmetric friction blocks where oscillations result in velocity spectra with a frequency falloff of 1/f.

Recent triaxial compression of rock samples have shown slip events over shear fracture produce velocity spectra with frequency falloff that approximates 1/f2(Beeler et al., 2020). Using the results found from the model, a hypothesis on the mechanism that produces the 1/f2falloff is proposed: the shear fracture in the compression test is produced by formation of vertical micro-cracks within the rock samples. This effectively creates an anisotropic material with axes of symmetry inclined to the shear fracture, which explains the 1/f2spectra.

Acknowledgement. EP and AVD acknowledge support from the Australian Research Council through project DP210102224.

References

BAFEKRPOUR, E., DYSKIN, A., PASTERNAK, E., MOLOTNIKOV, A. & ESTRIN, Y. 2015. Internally architectured materials with directionally asymmetric friction. Scientific reports, 5, 10732-10732.

BEELER, N. M., MCLASKEY, G. C., LOCKNER, D. & KILGORE, B. 2020. Near‐Fault Velocity Spectra From Laboratory Failures and Their Relation to Natural Ground Motion. Journal of geophysical research. Solid earth, 125, n/a.
Coastal flooding and mean sea-level rise allowances in atoll island
Authors: Amores Angel , Marcos Marta , Le Cozannet Gonéri , Hinkel Jochen
Published: March 2022

Atoll islands are among the places most vulnerable to climate change due to their low elevation above mean sea level. Even today, some of these islands suffer from severe flooding generated by wind-waves, that will be exacerbated with mean sea-level rise. Wave-induced flooding is a complex physical process that requires computationally-expensive numerical models to be reliably estimated, thus limiting its application to single island case studies. Here we present a new model-based parameterisation for wave setup and a set of numerical simulations for the wave-induced flooding in coral reef islands as a function of their morphology, the Manning friction coefficient, wave characteristics and projected mean sea level that can be used for rapid, broad scale flood risk assessments. We apply this new approach to the Maldives to compute the increase in wave hazard due to mean sea-level rise, as well as the change in island elevation or coastal protection required to keep wave-induced flooding constant. While future flooding in the Maldives is projected to increase drastically due to sea-level rise, we show that similar impacts in nearby islands can occur decades apart depending on the exposure to waves and the topobathymetry of each island. Such assessment can be useful to determine on which islands adaptation is most urgently needed.
Treatment of Noise in GRACE Gravity Field Recovery: A Comparison between Empirical Parameterization and Stochastic Modelling
Authors: Nie Yufeng , Shen Yunzhong , Pail Roland , Chen Qiujie
Published: March 2022

Continuous efforts have been made by different GRACE data analysis centers to improve the quality of monthly gravity field solutions, where one of the key issues concerns the treatment of noise in the parameter estimation process. In the broader context, the noise is not limited to the imperfection of sensor measurements only but also includes unmodelled and/or mismodelled parts of the satellite dynamics. In this contribution, we revisit four widely used strategies to reduce the influence of noise in GRACE gravity field recovery, which are: the estimation of high-frequency (constrained) empirical accelerations (ACC for short); the estimation of K-band range-rate empirical parameters (KBR); the utilization of fully populated covariance matrix for data weighting (COV), and the time series model-based filtering technique (FILT). In their ways to deal with the noise, the ACC and KBR strategies can be grouped into the method of empirical parameterization, while the COV and FILT strategies belong to the treatment of stochastic modelling. From a theoretical aspect, we regard the ACC and COV strategies as special cases of the least-squares collocation (LSC); the ACC and KBR strategies can be directly linked by the linear perturbation theory, while the COV and FILT strategies resemble different spectral estimation methods. Furthermore, we use numerical simulations to evaluate the performances of the four strategies, which show that the ACC, COV and FILT are more effective in mitigating noise than the KBR strategy. In the spectral domain, the stochastic modelling-based strategies (COV and FILT) have the full-spectrum capability to treat noise, while empirical parameters adopted in the ACC and KBR strategies work as high-pass filters. Consequently, stochastic modelling can lead to more consistent formal error estimates than empirical parameterization, especially for high-degree spherical harmonic coefficients.
Study on the Influence of Slope Shape on the Development of Ephemeral Gully Based on UAV
Authors: Wang Haiyu , Pang Guowei , Wang Chunmei , Wang Lei , Long Yongqing
Published: March 2022

In order to explore the influence of slope shape on the development of ephemeral gully, 225 ephemeral gullies were obtained by visual interpretation based on the unmanned aerial photography of Langerzigou in Jingbian County, Shaanxi Province. The number and length of ephemeral gullies, the distance from the gully head to the watershed and the gully density were calculated. The original slope DEM was obtained by interpolating the elevation points on the ephemeral gully watershed, and the DEM was used to extract the terrain curvature to describe the hillslope shape, and then analyze the relationship between the slope shape and the ephemeral gully index. The results showed that: (1) the DEM after the elevation point interpolation on the ephemeral gully watershed was used to synthesize the ephemeral gully, which can well describe the original slope topographic features before the development of the ephemeral gully. (2) From the point of view of single slope shape, the gully density of the transverse concave slope was the highest, and the number of ephemeral gullies, the average distance from the gully head to the watershed of the longitudinal concave slope were the largest. the average length of the ephemeral gully and the number of the longitudinal convex slope were the largest. From the point of view of the combined slope shape, the average length of the ephemeral gully and the average distance from the gully head to the watershed on the biconvex slope and the convex slope were larger than those on the biconvex slope and the concave-convex slope. The ephemeral gully length of double concave slope was significantly different from that of double convex slope and convex concave slope (P<0.05); The ephemeral gully length of concave convex slope was significantly different from that of double convex slope and convex concave slope (P<0.05); There was a significant difference in the distance from the trench head to the watershed between the concave convex slope and the concave convex slope (P<0.1). (3) The curvature distribution characteristics of different forms of slope shallow ditch development were analyzed.
How does lithospheric strength, mantle hydration and slab flexure relate to seismicity in the southern Central Andes?
Authors: Rodriguez Piceda Constanza , Scheck-Wenderoth Magdalena , Cacace Mauro , Bott Judith , Gao Ya-Jian , Tilmann Frederik , Strecker Manfred
Published: March 2022

The southern Central Andes (SCA, 29°S—39°S) orogen is one of the seismically most active regions along the length of the South-American convergent margin, where past earthquakes (e.g., San Juan in 1944, Valdivia M9.5 in 1960 and M8.8 Maule in 2010) have had devastating effects on the population. Past research has extensively focused on linking the occurrence of seismic activity with the stress regime on individual faults at a local scale.  In order to more systematically address the relationship between the long-term rheological configuration of the whole lithosphere and the spatial patterns of seismic deformation in the SCA, we computed a 3D model of the expected mechanical strength and rheology (brittle, ductile) of the SCA and adjacent forearc and foreland regions based on an existing 3D model describing the first-order variations of thickness, composition and temperature of geological units forming the upper and subducting plates. We found that the spatial variation in the predicted rheology correlates well with the distribution of seismic deformation in the upper plate, with seismicity bounded to the modelled brittle deformation domain. Moreover, seismic events localize at the transition between mechanically strong and weak domains. This ultimately indicates that the strength of the lithosphere exerts a first-order control on the mechanical stability of the region.

In contrast, the results from the rheological model fail to reconcile the observed slab seismicity at depths > 50—70 km, where ductile rheological conditions are expected. In this case, we evaluated possible additional mechanisms triggering these earthquakes, including compaction of sediments at the interface, metamorphic reactions within the oceanic crust and mantle, and slab flexural stresses. To characterize the state of hydration of the mantle related to dehydration reactions and/or sediment compaction, we made use of the Vp/Vs ratio from a seismic tomography model. The majority of the slab seismicity was found to spatially correlate with hydrated areas of the slab and overlying continental mantle, apart from a cluster where the slab attains a sub-horizontal angle. In this region, the correlation between the focal mechanisms of these earthquakes and the slab orientation, suggests that seismicity here is driven by enhanced flexural stresses within the oceanic plate.

This contribution showcases the importance of a quantitative characterization of the rheological state of the lithosphere to elucidate the causative dynamics of the spatial distribution of seismicity in the area.
Infrasound thunder detections across 15 years over Ivory Coast: localization, propagation, and link with the stratospheric semi-annual oscillation
Authors: Farges Thomas , Hupe Patrick , Le Pichon Alexis , Ceranna Lars , Diawara Adama
Published: March 2022

Every day, around one thousand thunderstorms occur around the world producing about 45 lightning flashes per second. One prominent infrasound station of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization for studying lightning activity is IS17 in Ivory Coast where the lightning rate is relatively high. Infrasound is defined as acoustic waves with frequencies below 20 Hz, the lower limit of human hearing. Statistical results are presented in this paper based on infrasound measurements from 2004 to 2019. One-to-one association between infrasound detections from 0.5 to 5 Hz and lightning flashes detected by the World Wide Lightning Location Network within 500 km from the infrasound station is systematically investigated. Most of the infrasound signals detected at IS17 in this frequency band are due to thunder, even if the thunderstorms are located up to 500 km away from the station. A decay of the thunder amplitude with the flash distance, d, is found to scale as d to the power of -0.717 for flashes within 100 km from the station, which holds for direct and tropospheric waveguide propagation. Interestingly, the stratospheric detections reflect a pattern in the annual azimuth variation, which is consistent with the equatorial stratospheric Semi-Annual Oscillation.
Electromagnetic Ion Cyclotron Harmonic Waves Generated via Nonlinear Wave-Wave couplings
Authors: Deng Dan , Yuan Zhigang , Huang Shiyong , Xue Zuxiang , Huang Zheng , Yu Xiongdong
Published: March 2022

 In this letter, we report an electromagnetic ion cyclotron (EMIC) harmonic event observed by the Van Allen Probe B, whose generation is demonstrated to result from nonlinear wave-wave resonances through the bicoherence analysis. Hybrid simulation shows that the second to sixth harmonics could be excited in sequence after a pump EMIC wave is initially injected, which is in consistent with the observations of EMIC harmonic. It indicates the important role of the second harmonic in the generation of higher harmonics. Finally, the statistical distribution for the amplitude of EMIC second harmonic waves indicates that the energy transfer rate from the fundamental wave to the second harmonic is mainly less than 2%, which might be too low to result in third and other higher harmonics above the observational level. Our results will give some new insights into the excitation of EMIC harmonic waves in the inner magnetosphere.
Ventilation controls of ocean heat and carbon uptake: similarities and differences in the response to carbon emissions
Authors: Katavouta Anna , Williams Richard
Published: March 2022

Ocean ventilation provides the primary control of how the ocean takes up  excess carbon and heat supplied to the earth system due to carbon emissions. Ventilation involves an atmospheric source supplying a tracer to the mixed layer, which is then physically transported into the thermocline and deep ocean by the ocean circulation. For this physical transfer of tracer, there are two characteristic timescales: (i) a fast adjustment controlled by the depth of the mixed layer and (ii) a slow adjustment controlled by the rate of mass transfer to the ocean interior. However, this physical transfer is modified for heat and carbon by climate feedbacks and carbonate chemistry respectively. Here, we use a conceptual 2-dimensional ocean model that is designed to address the ocean adjustment to carbon emissions on yearly to multi-centennial timescales. The model includes  a source, an ocean mixed-layer and interior adjustments, and a feedback mechanism that includes a surface temperature feedback  (such as from clouds) and the effects of carbonate chemistry; the model ignores any seasonality, biological processes and chemical weathering. Using this conceptual model, we reveal  the similarities and differences in how ventilation controls the uptake of heat and carbon involving changes in how the fast and slow adjustments are controlled.  In summary, despite the physical transfer of fluid being determined by ocean ventilation, the effects of climate feedbacks and carbonate chemistry lead to differences in the ocean thermal and carbon adjustments to an increase in atmospheric CO2.
Measurements of PG during rain, hail, snow and lightning
Authors: Kourtidis Konstantinos , Misios Stergios , Karagioras Athanasios , Kosmadakis Ioannis
Published: March 2022

We present an analysis of the evolution of PG during the course of rain, hail and snow events at the Xanthi site, N. Greece. In particular, using data from eight rain events in 2021, four hail events in the period 2018-2021 and four snow events during the same period, we examine how the PG frequency distribution changes during the progression of these events and discuss potential implications for the charge of the hydrometeors and the clouds that produce them. We also present some first results from recently started measurements of PG and lightning at the high altitude (2340 m ASL) site of Helmos Observatory, Peloponnese, Greece.
A Path to Quantitative Interpretation of Antarctic Sediment Provenance Records
Authors: Marschalek Jim , Gasson Edward , van de Flierdt Tina , Hillenbrand Claus-Dieter , Siegert Marin
Published: March 2022

Tracing the provenance of Antarctic sediments yields unique insights into the form and flow of past ice sheets. However, sediment provenance studies are typically limited to qualitative interpretations by uncertainties regarding subglacial geology, glacial erosion, and transport of sediment both subglacially and beyond the ice sheet margin. Here, we forward model marine geochemical sediment provenance data, in particular neodymium isotope ratios. Numerical ice-sheet modelling predicts the spatial pattern of subglacial erosion rates for a given ice sheet configuration, then ice flow paths are traced to the ice sheet margin. For the modern ice sheet, simple approximations of glacimarine sediment transport processes produce a good agreement with Holocene surface sediments in many areas of glaciological interest. Calibrating our model to the modern setting permits application of the approach to past ice sheet configurations, which show that large changes to sediment provenance over time can be reconstructed around the West Antarctic margin. This first step towards greater integration of Antarctic sediment provenance data with numerical modelling offers the potential for advances in both fields.
Representing socio-economic factors in INFERNO using the Human Development Index
Authors: Teixeira Joao , Burton Chantelle , Kelley Douglas I. , Folberth Gerd , O'Connor Fiona M. , Betts Richard , Voulgarakis Apostolos
Published: March 2022

INFERNO human fire ignitions and fire suppression functions excluded the representation of socio-economic factors (aside population density) that can affect anthropogenic behaviour regarding fire ignitions. To address this, we implement a socio-economic factor in the fire ignition and suppression parametrisation in INFERNO based on an Human Development Index (HDI) term. The HDI is calculated based on three indicators designed to capture the income, health, and education dimensions of human development. Therefore, we assume this leads to a representation where if there is more effort in improving human development, there is also investment on higher fire suppression by the population. Including this representation of socio-economic factors in INFERNO we were able to reduce large positive biases that were found for the regions of Temperate North America, Central America, Europe and Southern Hemisphere South America without significant impact to other regions, improving the model performance at a regional level and better representing processes that drive fire behaviour in the Earth System.
Wildfire Emissions and Air Quality: A Case Study on Forest Fires in Southern Orléans, France
Authors: Xue Chaoyang , Krysztofiak Gisèle , Ren Yangang , Cai Min , Grosselin Benoit , Daële Véronique , Mellouki Abdelwahid , Catoire Valéry
Published: March 2022

Wildfire events are increasing globally due to climate change, with significant adverse impacts on regional air quality and global climate. In the middle of September 2020, a wildfire event occurred in Souesmes (Loir-et-Cher, France), and its plume spread out to 200 km around in the following day as observed by the MODIS satellite. Based on comprehensive field measurements at a suburban atmospheric observation site (~50 km northwest from the wildfire location) in Orléans, young fire plumes were identified. Significant increases in trace gases (CO, CH4, N2O, VOCs, etc.) and particles (including black carbon) were found within the BB plumes. Molar enhancement ratios, defined as EF (X) = ∆X/∆CO (where X represents the target species), of various trace gases and black carbon within young plumes were determined accordingly and compared with previous studies. Changes in the ambient ions (ammonium, sulfate, nitrate, chloride, nitrite, etc. in the particle- and gas-phase) and aerosol properties (e.g., aerosol water content, pH) were also quantified and discussed. Furthermore, along with trajectory model (FLEXPART) simulations, we found that the Global Fire Assimilation System (GFAS) may underestimate emissions (e.g., CO) of this small wildfire while other inventories (GFED, FINN) showed significant overestimation. Estimation of emissions of this fire event was conducted and compared with GFAS emissions. Related atmospheric implications are also presented and discussed.
Cultivation of fiber hemp using solid and liquid residues from municipal composting in a closed system
Authors: Sut-Lohmann Magdalena , Matvejeva Agne , Dietrich Nils , Heinrich Martina , Raab Thomas
Published: March 2022

Progressing degradation of agricultural soil demands a change to more sustainable cropping systems accounting for crops that can sustain the soil health. Hemp is known for the improvement of soil physical, chemical and biological properties. The objective of the research is to analyze the hemp plant capability to grow under nutrient poor soil conditions and dense canopy and to assess hemp’s ability to uptake plant nutrients applied with/by soil amendments produced from biowaste. Additionally, the research aims to analyze how the hemp nutrition affects its morphogenesis, thus the fiber content.

In the greenhouse set up, Cannabis Sativa L. was grown in sandy substrate, with limited water supply that corresponded to the common drought periods in Brandenburg (Germany) and with addition of soil amendments in form of pellets from organic waste (OW) digestives. The treatments included: 5 control pots, 10 pots with pellets (19 kg soil / 230 g pellets according to the allowed application of 13 t/ha) and 10 pots with 19 kg soil / 3 kg pellets. When needed, a universal liquid fertilizer was applied which contained water soluble minerals like N, P2O5 and K2O. After 92 days, the plants were harvested, dried and weighted. The root structure was examined visually. The stems were decorticated using BMS-FLAKSY® (Rossmanith GmbH) to analyze the fiber content. The Elementar vario MAX cube analyzer device was used to analyse C and N contents.

The results showed that hemp could still flourish in water and nutrient limited environment. A deeper and denser rooting was observed in the treatments with pellets. It was observed that fine roots were encircled and attached to the pellets to access the nutrients stored there. The highest C:N ratio in soil and in leaves was found in treatments that contained the most pellets. The option to apply pellets produced from OW in larger quantities instead of a fertilizer application had a striking effect on hemp growth and biomass accumulation hence, increased dry matter amount and fiber yield.
Continental rifts and mantle convection: Insights from the East African Rift and a new model of the West European Rift System
Authors: Jolivet Laurent , Allanic Cécile , Becker Thorsten , Bellahsen Nicolas , Briais Justine , Davaille Anne , Faccenna Claudio , Lasseur Eric , Romanowicz Barbara
Published: March 2022

The origin of the Eocene-Oligocene European Cenozoic Rift System (ECRIS) is debated in terms of driving forces, far-field or near field, Alpine slab-pull or active plume. An analysis of residual (non-isostatic) topography over Africa and Europe reveals domains elongated parallel to the absolute motion of plates in a hot-spot reference frame. The East African Rift (EAR) and the ECRIS sit on top of such positive anomalies. A recent whole mantle tomographic model (French et al., 2013; French & Romanowicz, 2015; Davaille & Romanowicz, 2020) shows in addition that the low shear-wave velocity zones of the lower and upper mantle are organized with a bundle of vertical plumes and horizontal fingers pointing in the same direction parallel to the absolute motion of Africa and Eurasia, thus parallel to the main rifts. The case of the EAR and its magmatic extension toward the north across the Arabian Plate is particularly clear with several levels of such fingers. The northward migration of the first volcanism from Ethiopia to Armenia between the Eocene and the Late Miocene suggests that the asthenosphere moves faster than the plates and thus drives plate motion (Faccenna et al., 2013). We propose a simple model where plates are driven by basal drag, following an upwelling from the low-velocity anomalies below Africa and toward subduction zones. The EAR develops as lithospheric weak zones on top of the positive anomalies of residual topography due to the underlying low velocity anomalies elongated parallel to the absolute motion. This indicates an interplay between large-scale convection, a small-scale fingering instability, and lithospheric deformation. The development of the Eocene-Oligocene short-lived ECRIS and its interference with Mediterranean slab dynamics are then discussed in the framework of this simple model.