bluuebunny/crossref_metadata_2025 huggingface dataset:
Can we use heat flows to quantify microbial traits in soils?
Authors: Chakrawal Arjun , Herrmann Anke M. , Manzoni Stefano
Published: March 2021

Knowledge of functional traits such as the maximum substrate uptake rate and growth efficiency of microorganisms is crucial in understanding the turnover and storage of soil organic carbon. In addition to CO2 measurements, heat dissipation from organic matter decomposition is also a well-recognized proxy for microbial activity in soils. However, only a few attempts have been made to utilize heat signals for quantifying microbial traits.

To leverage high-resolution heat dissipation data, a coupled mass-energy balance model is proposed and used to estimate microbial traits encoded in model parameters. Our underlying question was whether heat dissipation data alone would be sufficient to quantify key microbial traits, or whether respiration rates were also necessary to constrain the model. To this aim, we parametrized four variants of the model using heat dissipation and respiration rate data at different time scales: during the initial lag-phase (5 hours) and throughout the growth-phase until substrate depletion (48 hours) in an isothermal calorimeter combined with a gas analyzer. The four different variants of the model were: (i) a complex physiological model (including active and inactive biomass), (ii) a simplified physiological model (only active microbial biomass), (iii) a model describing only the lag-phase (no growth, only maintenance), and (iv) a model describing only the growth phase (growth under substrate-abundant conditions). Microbial traits were determined using three combinations of data: A) only the heat dissipation rate, B) only the respiration rate, and C) both heat dissipation and respiration rates. We assumed that the ‘best’ parameter estimates would be obtained when using all the available data (i.e., option C).

Our results show that all model variants were able to fit the observed heat dissipation and respiration rates at the respective time scales. Parameters shared among different model variants were generally comparable, indicating that our model simplifications led to structurally sound models. The parameters estimated using only heat dissipation data were similar to the ‘best’ estimates compared to using only respiration rate data, suggesting that the observed heat dissipation rate can be used to constrain microbial models and estimate microbial traits.
Declining soil-root hydraulic conductance drives stomatal closure of tomato under drought 
Authors: Abdalla Mohanned , Carminati Andrea , Cai Gaochao , Javaux Mathieu , Ahmed Mutez
Published: March 2021

The fundamental question as to what triggers stomatal closure during soil drying remains contentious. Thus, we urgently need to improve our understanding of stomatal response to water deficits in soil and atmosphere. Here, we investigated the role of soil-plant hydraulic conductance (Ksp) on transpiration (E) and stomata regulation. We used a root pressure chamber to measure the relation between E, leaf xylem water potential (ψleaf-x) and soil water potential (ψsoil) in tomato. Additional measurements of ψleaf-x were performed with unpressurized plants. A soil-plant hydraulic model was used to simulate E(ψleaf-x) for decreasing ψsoil. In wet soils, E(ψleaf-x) had a constant slope while in dry soils the slope decreased, with ψleaf-x rapidly and nonlinearly decreasing for moderate increases in E. The ψleaf-x measured in pressurized and unpressurized plants matched well, which indicates that the shoot hydraulic conductance did not decrease during soil drying and that the decrease in Ksp is caused by a decrease in soil-root conductance. The decrease of E matched well the onset of hydraulic nonlinearity. Our findings demonstrate that stomatal closure prevents the drop in ψleaf-x caused by a decrease in Ksp and elucidate a strong correlation between stomatal regulation and belowground hydraulic limitation.
Assessment of Impact of Hydroclimatic Disturbances on Terrestrial GPP Extremes of India Under Land Use and Climate Change
Authors: Chakraborty Abhishek , Muddu Sekhar , Rao Lakshminarayana
Published: March 2021

Gross primary productivity (GPP) plays a vital role in the carbon storage potential of ecosystems. Climate change (CC), land use and cover change (LUCC), elevated CO2 concentrations (eCO2), and Nitrogen deposition (Ndep) are the main driving forces of GPP. Climate extremes are expected to negatively impact ecosystem carbon uptake (Du et al., 2018, Sci. Total Environ.). The knowledge of impacts of hydroclimatic disturbances (temperature, precipitation, soil moisture, drought, fire emission) on the GPP extremes is still limited for the Indian ecosystems. This study aims to quantify the GPP extremes and assess the drivers of these extremes across Indian ecosystems.

The study considers fourteen terrestrial biosphere models (TBMs). These TBMs are DLEM, ISAM, LPJ-wsl, ORCHIDEE-LSCE, BIOME-BGC, CLM4, CLM4VIC, CLASS-CTEM-N, GTEC, Sib3, SibCASA, TEM6, VISIT, and VEGAS2.1, which took part in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP). We consider these models' GPP ensemble values from 1981-2010 for four cases: CC, CC+LUCC, CC+LUCC+eCO2, and CC+LUCC+eCO2+Ndep. This multi-model ensemble approach predicts better estimates as it captures uncertainty better than a single model (Schwalm et al., 2015, Geophys. Res. Lett.). We also consider an observation-based model by Jung et al. (2011) along with these ensembles. We use a 3-D contiguous (Zscheischler et al., 2013, Ecol. Inform)   statistical approach to assess the spatiotemporal pattern of extreme GPPs in India and in its six meteorologically homogeneous regions. We also diagnose the size distribution and attribution of these negative extreme GPP events to each of these drivers individually and multiple drivers in a compounded way.
Global-scale Aircraft Observations and Simulations of Cirrus Clouds and Aerosol Indirect Effects
Authors: Diao Minghui , Patnaude Ryan , Liu Xiaohong , Chu Suqian
Published: March 2021

Cirrus clouds have widespread coverage over Earth's surface area. Cirrus cloud radiative forcings are directly affected by the microphysical properties of cirrus clouds, including ice water content (IWC), ice crystal number concentration (Nice), and mean diameter (Dice). In this work, in-situ observations obtained from seven flight campaigns funded by the U.S. National Science Foundation are used to examine key factors controlling the formation and evolution of cirrus clouds. These key factors include thermodynamic conditions (i.e., temperature and relative humidity), dynamic conditions (i.e., vertical velocity), and aerosol indirect effects from larger and smaller aerosols (> 500 nm and > 100 nm, respectively). After isolating the effects from thermodynamic and dynamic conditions, we found that when aerosol number concentrations (Na500 and Na100) increase, IWC, Nice and Dice all increase. In particular, IWC and Nice increase significantly when Na is about 3 – 10 times larger than the average Na conditions (Patnaude and Diao, GRL, 2020).

Simulations of cirrus clouds by a global climate model – the U.S. National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 6 (CAM6) are evaluated against in-situ observations (Patnaude, Diao, Liu and Chu, ACP, accepted). Observations show higher Nice in the northern hemisphere (NH) midlatitude than southern hemisphere (SH) midlatitude. CAM6 simulations show “too many” and “too small” ice crystals in most of the regions except NH midlatitude, where simulations show lower Nice than the observations. Weaker aerosol indirect effects on cirrus clouds are also seen in the simulations compared with observations.
Predicting Responses of Chemical and Biological Water Quality to Human-induced Environmental Changes: The Case Study of Clariano River, Spain
Authors: Vagheei Hamed , Vezza Paolo , Palau-Salvador Guillermo , Boano Fulvio
Published: March 2021

Abstract

Freshwater ecosystems provide many benefits to a variety of species but, unfortunately, human-caused environmental issues are undermining their ability to provide key functions and services. Changes in climate and land use, for instance, impact the habitat suitability for freshwater organisms by affecting water quantity and quality. Nutrients, pesticides, heavy metals and other contaminants which are released to the environment as a result of anthropogenic activities have the potential to degrade the environment and damage freshwater communities. Hence, the present research activity aims to investigate aquatic ecosystem responses to environmental deterioration using a case study of Clariano River, Spain. The Soil and Water Assessment Tool (SWAT) is used as an eco-hydrological tool to model discharge, sediment and nutrients, and to predict the biological status in Clariano River under different scenarios. As the diversity and presence of species represent the quality of ecosystem, this study focuses on macroinvertebrates as biological indicators of stream health. The SUFI-2 algorithm in the SWAT-CUP program is used for the calibration, validation, sensitivity and uncertainty analysis of the SWAT model. The results from the calibrated model are then coupled to regression equations between measured nutrient concentrations and values of several macrobenthic metrics in six sampling sites along the Clariano River. The coupling of these regression equations with concentrations simulated with SWAT for different scenarios allows to improve the understanding of the relations between environmental changes in watersheds, nutrient concentrations, and the biologic status of stream water.

Keywords: water quality, macroinvertebrates, environmental degradation, eco-hydrological modelling, Clariano River
Estimating mean annual runoff by using a geostatistical spatially varying coefficient model that incorporates process-based simulations and short records
Authors: Roksvåg Thea , Steinsland Ingelin , Engeland Kolbjørn
Published: March 2021

In this work, we suggest a new framework for estimating mean annual runoff, which is a key water balance component.  The framework consists of two steps: 1) A process-based hydrological model is used to simulate mean annual runoff on a grid covering the whole study area. 2) Since the parameters of the process-based model are calibrated globally, there are local biases in the runoff estimates relative to the observed runoff. We therefore correct the gridded simulations based on runoff data. Here, step 2 is done by using a Bayesian geostatistical model that treats the process-based simulations as a covariate. The regression coefficient of the covariate is modelled as a spatial field such that the relationship between the covariate (simulations from the process-based model) and the response variable (the observed mean annual runoff) is allowed to vary within the study area. Hence, it is a spatially varying coefficient model. A preprocessing step for including short records in the modelling is also suggested such that we can exploit as much data as possible in the correction procedure. We use state of the art statistical methods such as SPDE and INLA to ensure fast Bayesian inference.

 

The framework for estimating mean annual runoff is evaluated by predicting mean annual runoff for 1981-2010 for 127 catchments in Norway based on streamflow observations from 411 catchments. Simulations from the process-based HBV model on a 1 km x 1 km grid for the whole country are used as input. We found that on average the proposed approach outperformed a purely process-based approach (HBV) when predicting runoff for ungauged and partially gauged catchments: The reduction in RMSE compared to the HBV model was 20 % for ungauged catchments and 58 % for partially gauged catchments. For ungauged catchments the proposed framework also outperformed a purely geostatistical method with a 10 % reduction in RMSE compared to the geostatistical method. For partially gauged catchments however, purely geostatistical methods performed equally well or slightly better than the proposed two step procedure. In general, we expect the proposed approach to outperform purely geostatistical models in areas where the data availability is low to moderate.
Forecasting the Preparatory Phase of Induced Earthquakes by Recurrent Neural Network
Authors: Iaccarino Antonio Giovanni , Picozzi Matteo
Published: March 2021

Earthquakes prediction is considered the holy grail of seismology. After almost a century of efforts without convincing results, the recent raise of machine learning (ML) methods in conjunction with the deployment of dense seismic networks has boosted new hope in this field. Even if large earthquakes still occur unanticipated, recent laboratory, field and theoretical studies support the existence of a preparatory phase preceding earthquakes, where small and stable ruptures progressively develop into an unstable and confined zone around the future hypocenter. The problem of recognizing the preparatory phase of earthquakes is of critical importance for mitigating seismic risk for both natural and induced events. Here, we focus on the induced seismicity at The Geysers geothermal field in California. We address the preparatory phase of M~4 earthquakes identification problem by developing a ML approach based on features computed from catalogues, which are used to train a Recurrent Neural Network (RNN). We show that RNN successfully reveal the preparation of M~4 earthquakes. These results confirm the potential of monitoring induced microseismicity and should encourage new research also in predictability of natural earthquakes.
Air temperature controls diel oscillation of the CO2 concentration in a desert soil
Authors: Spohn Marie , Holzheu Stefan
Published: March 2021

The factors that control the soil CO2 concentration are not yet well understood. Therefore, the objective of this study was to explore what factors control the soil CO2 concentration and its dynamic in a desert soil. For this purpose, CO2 concentration and temperature were measured in six soil depths (ranging from 15 to 185 cm) in a deeply weathered, coarse-textured desert soil in the North of Chile at high frequency (every 60 minutes) together with precipitation and air temperature for one year. The mean CO2 concentration calculated across the whole measuring period increased linearly with soil depth from 463 ppm in 15 cm to 1542 ppm in 185 cm soil depth. We observed a diel oscillation of the CO2 concentration that decreased with soil depth and a hysteretic relationship between the topsoil CO2 concentration and both air and soil temperature. A small precipitation event increased the CO2 concentrations in 15, 30, and 50 cm soil depths for several days but did not alter the amplitude of the diel oscillation of the CO2 concentration. The diel oscillation was very likely caused by strong differences between the soil and the air temperature at night, in particular in summer, causing transport of topsoil air to the atmosphere by thermal convection. Our results have important implications as they show that the soil CO2 concentration can be controlled by air temperature through thermal convection, rather than by soil temperature, and that the hysteretic relationship between soil CO2 concentration and temperature can be caused by physical factors alone.

 
The stratospheric Brewer-Dobson circulation inferred from age of air in the ERA5 reanalysis
Authors: Ploeger Felix , Diallo Mohamadou , Charlesworth Edward , Konopka Paul , Legras Bernard , Laube Johannes , Grooß Jens-Uwe , Günther Gebhard , Engel Andreas , Riese Martin
Published: March 2021

This paper investigates the global stratospheric Brewer-Dobson circulation (BDC) in the ERA5 meteorological reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The analysis is based on simulations of stratospheric mean age of air, including the full age spectrum, with the Lagrangian transport model CLaMS, driven by winds and total diabatic heating rates from the reanalysis. ERA5-based results are compared to those of the preceding ERA-Interim reanalysis. Our results show a significantly slower BDC for ERA5 than for ERA-Interim, manifesting in weaker diabatic heating rates and larger age of air. In the tropical lower stratosphere, heating rates are 30-40% weaker in ERA5, likely correcting a known bias in ERA-Interim. Above, ERA5 age of air appears slightly high-biased and the BDC slightly slow compared to tracer observations. The age trend in ERA5 over 1989-2018 is negative throughout the stratosphere, as climate models predict in response to global warming. However, the age decrease is not linear over the period but exhibits steplike changes which could be caused by muti-annual variability or changes in the assimilation system. Over the 2002-2012 period, ERA5 age shows a similar hemispheric dipole trend pattern as ERA-Interim, with age increasing in the NH and decreasing in the SH. Shifts in the age spectrum peak and residual circulation transit times indicate that reanalysis differences in age are likely caused by differences in the residual circulation. In particular, the shallow BDC branch accelerates similarly in both reanalyses while the deep branch accelerates in ERA5 and decelerates in ERA-Interim.
Multiannual study of convective and stratiform situations associated to wet deposition of desert dust in the Sahelian band
Authors: Audoux Thomas , Laurent Benoit , Marticorena Béatrice , Bergametti Gilles , Rajot Jean Louis , Féron Anaïs , Gaimoz Cécile
Published: March 2021

In the semi-arid Sahel region, wet deposition can represent more than half of the total annual deposition and are associated to different rainfall types, from stratiform precipitation to convective systems. Surface parameters such as temperature, wind speed, wind direction as well as rainfall rate can be used to distinguish these situations. We investigate the behaviour of dust wet deposition at the event-scale based on a multiannual (2007 to 2016) monitoring of wet deposition fluxes, PM10 concentration, precipitation and meteorological parameters in two Sahelian stations Banizoumbou (Niger, 13.54°N, 2.66 E) and Cinzana (Mali, 13.28°N, 5.93°W) of the INDAAF network. Rainfall events have been classified into three types: (i) stratiform, convective associated with (ii) weak precipitation or (iii) intense precipitation. This classification is based on selected criteria regarding evolutions of surface temperature, of wind speed and direction before and after the rainfall onset as well as on the event rainfall rate. Based on an interpretation of hundreds of single events, almost 25% of wet deposition events are associated with non-convective situation, more than 40% with atmospheric convective situation and weak precipitation, and more than 35% events with atmospheric convective situation combined with intense precipitation. This exhaustive work over a long-time period of measurements illustrates the predominance of convective situations regarding wet deposition in the two Sahelian stations. Washout ratios (WR) have been computed from PM10 concentrations, precipitation and deposition fluxes for each kind of events when data were concomitant. The dependency of WR to precipitation amount is shown to differ depending on the rain types. For instance, the decreasing dependency of WR with the precipitation amount of non-convective events has been quantified and could be explained by a dilution effect of the deposition. On the contrary, no clear dependency of WR with the precipitation has been observed for atmospheric convective conditions associated with intense rainfall rate.
How are the coastal breezes affected by changes in the land surface? Analysis from a case study using WRF
Authors: Mulero-Martinez Roberto , Román-Cascón Carlos , Lothon Marie , Lohou Fabienne , Yagüe Carlos , Álvarez Óscar , Bruno Miguel , Gómez-Enri Jesús , Izquierdo Alfredo , Mañanes Rafael , Adame José Antonio
Published: March 2021

Sea breezes are common and recurrent thermally-driven wind circulations formed in coastal areas under conditions of weak synoptic forcing. The different heat capacity between the land and the sea causes the thermal contrast needed for their formation. Therefore, the temperature changes at the surface of both the sea and the land influence the breezes characteristics. In this work, we investigate how sensitive are the sea breezes to changes in land cover and soil moisture, which may have a direct impact on the surface temperature inland. This is done through the design of different sensitivity experiments performed with the Weather Research and Forecasting (WRF) model, where we tested the effect of the land use and soil moisture modification. This was done through the simulation of a typical sea-breeze case study in the coastal area of the southwest of the Iberian Peninsula (Gulf of Cádiz). The differences among the experiments are compared spatially and confronted with observations from different meteorological towers at the coast and inland. A special emphasis is made on the changes observed in the area of the National Park of Doñana. This area is characterised by large shallow marshes with varying seasonal status and extensive rice crops. Thus, contrasting conditions of the surface are typically observed, which also depend on the previous hydrological conditions. Preliminary results highlight the importance of the correct representation of the surface inland to obtain a proper simulation of the sea-breeze system. Besides, new lines of research emerge to analyse the impacts caused by other potential modifications in the surface conditions of the land and the ocean (e.g., global change, urbanization, crop modification, changes in precipitation regimes or sea surface temperature, etc).
The importance of phase morphology for rheology of ferropericlase-bridgmanite mixtures
Authors: Thielmann Marcel , Golabek Gregor , Marquardt Hauke
Published: March 2021

The rheology of the Earth’s lower mantle is poorly constrained due to a lack of knowledge of the rheological behaviour of its constituent minerals. In addition, the lower mantle does not consist of only a single, but of multiple mineral phases with differing deformation behaviour. The rheology of Earth’s lower mantle is thus not only controlled by the rheology of its individual constituents (bridgmanite and ferropericlase), but also by their interplay during deformation. This is particularly important when the viscosity contrast between the different minerals is large. Experimental studies have shown that ferropericlase may be significantly weaker than bridgmanite and may thus exert a strong control on lower mantle rheology.

Here, we thus explore the impact of phase morphology on the rheology of a ferropericlase-bridgmanite mixture using numerical models. We find that elongated ferropericlase structures within the bridgmanite matrix significantly lower the effective viscosity, even in cases where no interconnected network of weak ferropericlase layers has been formed. In addition to the weakening, elongated ferropericlase layers result in a strong viscous anisotropy. Both of these effects may have a strong impact on lower mantle dynamics, which makes is necessary to develop upscaling methods to include them in large-scale mantle convection models. We develop a numerical-statistial approach to link the statistical properties of a ferropericlase-bridgmanite mixture to its effective viscosity tensor. With this approach, both effects are captured by analytical approximations that have been derived to describe the evolution of the effective viscosity (and its anisotropy) of a two-phase medium with aligned elliptical inclusions, thus allowing to include these microscale processes in large-scale mantle convection models.
Managing hydrology can reduce methane emissions of high-emitting freshwater marshes by half making them present-day net greenhouse gas sinks
Authors: Valach Alex , Eichelmann Elke , Hemes Kyle , Kasak Kuno , Knox Sara , Oikawa Patty , Szutu Daphne , Verfaillie Joseph , Baldocchi Dennis
Published: March 2021

Restoring wetlands for climate mitigation purposes could provide an effective method to protect existing soil carbon stocks, as well as act as a negative emission technology by sequestering atmospheric carbon for 100-1000s of years. However, many peatlands have low productivity limiting carbon sequestration, while high productivity marshes often emit large amounts of methane. Studies on water level management to control methane emissions have shown differing results depending on wetland type, climate, as well as measurement method and duration. Here we show with multi-year flux measurements that water level changes were likely responsible for significantly reducing annual methane emissions. To assess management impacts on annual greenhouse gas budgets, continuous high frequency measurements of fluxes are needed, such as by eddy covariance. However, this method is less suited to monitor concurrent manipulation experiments to compare treatments.  We compared the impact of water level fluctuations by creating a second timeseries where water drawdown events were removed, which was then gap-filled by a random forest model trained only on measurements from periods when the water table was above the surface. These estimates were used to compare the annual budgets with the complete data and showed that annual methane emissions were up to 50% lower in years where water levels went sufficiently below the peat surface. This threshold was key, as only reductions in water depth above the surface were related to temporary increases in emissions. We further show that in some cases the drawdowns tipped the greenhouse gas budgets so that marshes were net greenhouse gas sinks, as long as the drawdown did not also reduce plant productivity through drought stress. In comparison, wetlands with average annual fluxes would require between approx. 50 and 200 years given current levels of net carbon uptake to offset high methane emissions and become cumulative greenhouse gas sinks. 
Effects of hydric and light combined stresses on the morphological and plastic responses of Aspidosperma polyneuron Müll. Arg. Seedlings (Apocynaceae)
Authors: Pájaro-Esquivia Yelena S. , Domínguez-Haydar Yamileth , Tinoco-Ojanguren Clara , Lozano-Baez Sergio E. , Castellini Mirko , Di Prima Simone
Published: March 2021

There is a lack of knowledge on the grow requirements for most endangered plant species in tropical ecosystems. The interdisciplinary field of the “critical zone” provides an opportunity to understand the plant-soil interactions, allowing the development of strategies for species propagation and restoration. Aspidosperma polyneuron is a Tropical Dry Forest native species, currently categorized as “endangered” in Colombia and the neotropics.  In this study, we evaluated the intrapopulation differences in the morphological and plastic responses of A. polyneuron seedlings along an experimental gradient of light and water. We collected seedlings from two locations of the same population at the department of Atlántico (Colombia) and exposed them to three levels of light (100, 55 and 10%) and two different levels of water (field capacity, 60% and dry conditions, 20%). We allowed these seeds to grow for six months in an experimental 3 x 2 x 2 m random factorial design. In addition, we measured 16 morphological and growth traits associated to their performance. Results showed that medium-light treatment produced the most favorable outcome when facing drought conditions, while low light aggravated negative performance effects when facing drought conditions. The seedlings origin was a significant factor influencing the morphological responses of most traits. Regarding plasticity, there were differences in the pattern and magnitude of the traits according to the locality they were collected from. The influence of water gradient prevailed over the light gradient in the phenotypic responses. The results showed differences in the response mechanism of the two groups of seedlings, indicating intrapopulation differentiation processes between both groups.
Constraining a lumped rainfall-runoff model with piezometry to improve low-flow simulation
Authors: Pelletier Antoine , Andréassian Vakzen
Published: March 2021

Most lumped hydrological models are focused on the rainfall-runoff relationship, since climatic conditions are the driving force of the hydrological behaviour of a catchment. Many hydrological models, like the ones used by the French national PREMHYCE platform, only take climatic variables as inputs – daily rainfall and potential evaporation – to simulate and forecast low-flows. Yet, a hydrological drought is generally a medium- to long-term phenomenon, which is the consequence of long records of dry climatic conditions. Daily lumped hydrological models often struggle to integrate these records to reproduce catchment memory.

In many French catchments, it was observed that this memory of past hydroclimatic conditions is well represented in piezometric signals that are broadly available over the national territory. Indeed, aquifers, especially the large ones, do store water on the long, feeding rivers during droughts: aquifers are not only water carriers – the etymology for the word aquifer – they are also memory carriers. A dataset of 108 catchments, each of them being associated with one or several piezometers, was used to investigate whether the GR6J daily lumped rainfall-runoff model could be constrained by piezometric time series to improve low-flow simulations. We found that a particular state of the model, the exponential store, is particularly well correlated with piezometry in most studied catchments.

In order to get a univocal relationship between the exponential store and piezometry, a multi-objective calibration approach was implemented, optimising both (i) flow simulation with a criterion focused on low-flows and (ii) affine correspondence between the exponential store level and piezometry. For that purpose, a new parameter was added to the model. The modified calibration was then evaluated through a split-sample test and the performance in simulating particular drought events. The calibrated store-piezometry relationship can now be used for data assimilation to improve low-flow forecasting.
The seismic structure of the lithosphere in the greater Alpine area from S-to-P converted waves
Authors: Kind Rainer , Schmid Stefan , Yuan Xiaohui , Heit Ben
Published: March 2021

In the frame of the AlpArray project we analyse teleseismic data from permanent and temporary stations of the greater Alpine region to study seismic discontinuities in the entire lithosphere. We use broadband S-to-P converted signals from below the seismic stations. In order to avoid sidelobes, no deconvolution or filtering is applied and S arrival times are used as reference. We show a number of north-south and east-west profiles through the greater Alpine area. The Moho signals are always seen very clearly, and also negative velocity gradients below the Moho are visible in a number of profiles. The subducting European Moho is visible in the Eastern Alps west of 13.5°E (the eastern edge of the Tauern Window) and reaches there about 60km depth at 47°N. East of about 13.5°E, the image of the Moho changes completely. No south dipping European Moho is found anymore, instead the Moho is shallowing towards the Pannonian Basin. This suggests severe post-nappe emplacement modifications east of about 13.5°E, most probably associated with delamination of the mantle lithosphere within the formerly subducting European slab, i.e. mantle that separated from the crustal parts of the Alpine-West Carpathian orogen during the last ca. 20 Ma when the Pannonian basin formed and the ALCAPA block underwent its E-directed lateral extrusion.

Ratschbacher, L., Frisch, W., Linzer, H.-G. and Merle, O. (1991) Lateral extrusion in the Eastern Alps, Part 2: Structural analysis. Tectonics, vol.10, No.2, 257-271.
Improving Precipitation Retrieval by Brightness Temperature Temporal Variation (ΔTB): Definition, Computation, and Application
Authors: You Yalei , Peters-Lidard Christa , Munchak Stephen , Ringerud Sarah
Published: March 2021

Current microwave precipitation retrieval algorithms utilize the instantaneous brightness temperature (TB) from a single satellite to estimate the precipitation rate. This study proposed to add the time-dimension into the precipitation estimation process by using the TB (or emissivity) temporal variation (ΔTB or Δe) derived from the Global Precipitation Measurement (GPM) microwave radiometer constellation.  Results showed that (1) ΔTB can improve the precipitation estimation over the cold surfaces (i.e., snow-covered region) through minimizing the microwave land surface emissivity’s influence; (2) Δe under the clear-sky conditions can accurately estimate the daily rainfall accumulation; and (3) ΔTB can be used to identify the liquid raindrop signature over the low surface emissivity areas. This study highlights the importance of maintaining the current passive microwave satellite constellation.
Impacts of wildfire and post-fire land management on hydrological and sediment processes in a humid Mediterranean headwater catchment
Authors: Nunes Joao Pedro , Bernard-Jannin Léonard , Rodríguez-Blanco María Luz , Boulet Anne-Karine , Santos Juliana Marisa , Keizer Jan Jacob
Published: March 2021

The extensive afforestation of the Mediterranean rim of Europe in recent decades has increased the number of wildfire disturbances on hydrological and sediment processes, but the impacts on headwater catchments is still poorly understood, especially when compared with the previous agricultural landscape. This work monitored an agroforestry catchment in the north-western Iberian Peninsula, with plantation forests mixed with traditional agriculture using soil conservation practices, for one year before the fire and for three years afterwards, during which period the burnt area was plowed and reforested. During this period, continuous data was collected for meteorology, streamflow and sediment concentration at the outlet, erosion features were mapped and measured after major rainfall events, and channel sediment dynamics were monitored downstream from the agricultural and the burnt forest area. Data from 202 rainfall events with over 10 mm was analysed in detail.

Results show that the fire led to a notable impact on sediment processes during the first two post-fire years, but not on streamflow processes; this despite the small size of the burnt area (10% of the catchment) and the occurrence of a severe drought in the first year after the fire. During this period, soil loss at the burnt forest slopes was much larger than that at most traditionally managed fields, and, ultimately, led to sediment exhaustion. At the catchment scale, storm characteristics were the dominant factor behind streamflow and sediment yield both before and after the fire. However, the data indicated a shift from detachment-limited sediment yield before the fire, to transport-limited sediment yield afterwards, with important increases in streamflow sediment concentration. This indicates that even small fires can temporarily change sediment processes in agroforestry catchments, with potential negative consequences for downstream water quality.
Comparison of Q-bursts detected near the Earth’s surface and 140 m below ground level
Authors: Bór József , Lemperger István , Szabóné André Karolina , Bozóki Tamás , Mlynarczyk Janusz , Steinbach Péter , Lévai Péter , Ván Péter
Published: March 2021

Q-bursts are signatures of exceptionally powerful lightning strokes which produce intense radio waves typically in the extremely low frequency band (ELF, 3Hz-3kHz). Due to the finite conductivity of the Earth’s surface, radio waves in this frequency range can be also detected in greater depths. While the penetration of electromagnetic (EM) waves in a conducting half space has been investigated and utilized, e.g., under water for submarine radio communication, very few field measurements consider the subsurface detection of ELF waves in the continental crust.

In this work, Q-bursts recorded in near surface and corresponding underground ELF band observations are compared in order to characterize the frequency dependent effect of the upper section of the Earth’s crust on the spectrum of the Q-burst signals.

Practically co-located, but not simultaneous quasi-surface and underground temporal ELF band magnetic field measurements were made near Mátraszentimre, in the Mátra Mountains, Hungary. The underground measurement was carried out inside a mine shaft in the Matra Gravitational and Geophysical Laboratory (MGGL) at a depth of 140 m. ELF observations from two permanent recording stations in the Széchenyi István Geophysical Observatory (NCK, Hungary) and in Hylaty (HYL, Poland), less than 250 km away from MGGL, were involved in the analysis to deduce the transfer function between the unsynchronized quasi-surface and underground measurements in the Mátra.

The set of Q-bursts, which were parallelly detected at all three locations, was identified using GPS synchronized time stamps. Natural origin of the signals was confirmed by identifying the parent lightning strokes in the database of the World Wide Lightning Location Network (WWLLN) via matching the detection times and the corresponding source directions calculated at NCK station.

The good agreement of the results from independent Matra-NCK (5-30 Hz) and Matra-HYL (5-140 Hz) station-pairwise analyses confirm that the frequency dependence of the wave attenuation due to overlying rocks is exponential. The deduced integrated local conductivity, 30-40 S/m, of the upper section of the Earth’s crust suggests that probably the soil has prominent role in attenuating ground penetrating EM waves in the ELF band.
Mobilization of aged carbon via meltwater floods and coastal erosion in the Canadian Arctic during the last deglaciation
Authors: Wu Junjie , Mollenhauer Gesine , Stein Ruediger , Hefter Jens , Fahl Kirsten , Grotheer Hendrik , Wei Bingbing , Nam Seung-Il
Published: March 2021

It is consensus that the deglacial changes in ocean carbon storage and circulation play a role in regulating atmospheric CO2. However, emerging evidence suggests that the rapid deglacial CO2 rises can in part be attributed to large quantities of pre-aged carbon being released from degrading permafrost. In this study, we apply a radiocarbon approach on both terrestrial compounds (high molecular weight fatty acids; HWM-FA) and bulk organic carbon from a well-studied core ARA04C/37 from the Canadian Beaufort Sea. Based on our records, substantial amounts of ancient carbon were supplied from land to the ocean during the mid-late deglaciation (14.5-10 cal. kyr BP) by frequent high sediment flux events. Because the core location is strongly influenced by the Mackenzie River discharge, sediments only contain minor contributions from marine organic matter, allowing to consider mainly two terrestrial sources to explain the characteristics of bulk sedimentary organic matter. The terrestrial HMW-FA are taken to represent the biospheric carbon, and their age differences from the bulk organic carbon are explained by petrogenic carbon input. During the Younger Dryas, ice-sheet melting and meltwater outbursts enhanced petrogenic carbon contributions, suggesting a major source in the hinterland drainage system. During the rapid sea-level rise (meltwater pulses 1a and 1b), the very old organic carbon and comparable ages between biospheric carbon and bulk organic carbon indicate the occurrence of permafrost carbon remobilization primarily via coastal erosion while petrogenic carbon from the drainage system was found negligible. Remobilized ancient permafrost carbon is commonly regarded to be highly bioavailable, while petrogenic carbon is likely more recalcitrant to biological degradation. Our records thus suggest that the release of ancient carbon to the Beaufort Sea had the strongest impact on the atmospheric CO2 level and contributed to its rapid increases during the B/A and Pre-Boreal when permafrost deposits along the coast were eroded.
The role of energetic electron precipitation and background dynamics on the seasonal NO variability in the MLT region
Authors: Smith-Johnsen Christine , Nesse Tyssøy Hilde , Marsh Daniel Robert , Smith Anne , Maliniemi Ville
Published: March 2021

Energetic electron precipitation (EEP) ionizes the Earth's atmosphere and leads to production of nitric oxide (NO) throughout the polar Mesosphere and Lower Thermosphere (MLT). In this study we investigate the direct and indirect NO response to the EEP using the Whole Atmosphere Community Climate Model (WACCM) version 6. In comparison to observations from SOFIE / AIM (Solar Occultation For Ice Experiment / Aeronomy of Ice in the Mesosphere), we find that EEP production of NO in the D-region is well simulated when both medium energy electron precipitation and negative and cluster ion chemistry are included in the model. However, the main EEP production of NO occurs in the E-region, and there the observed and modeled production differ. This discrepancy impacts also the D-region due to downward transport of long lived NO. The transport across the mesopause is seasonally dependent, and WACCM’s underestimate of D-region NO is highest during winter when downwelling from above is strong. The drivers of this transport are further investigated by a sensitivity study of WACCM’s gravity wave forcing.
Local tie survey of the SLR and GNSS stations at the Shimosato Hydrographic Observatory
Authors: Watanabe Shun-ichi , Nakamura Yuto , Yokota Yusuke , Suzuki Akira , Ueshiba Haruka , Seo Noritsune
Published: March 2021

The Japan Coast Guard (JCG) operates Satellite Laser Ranging (SLR) and GNSS observation at the Shimosato Hydrographic Observatory (SHO) in Wakayama Prefecture, Japan. The SLR and GNSS observation results obtained at the SHO are submitted to the ILRS and the IGS, respectively, and have contributed to the development of the International Terrestrial Reference Frame (ITRF). The SHO, operating two types of global geodetic observation, is now one of the sites of the Global Geodetic Observing System (GGOS).

Observation sites such as the SHO that operate multiple geodetic techniques function as co-location sites, where the different geodetic techniques can be linked together by precisely determining the local tie between these techniques. In November 2020, the JCG and the Geospatial Information Authority of Japan (GSI) have performed a local tie survey at the SHO to determine the local tie between the SLR telescope and the GNSS station. In our survey, we mounted several targets on the SLR telescope, which we observed from four survey sites that were temporarily set in the SHO. During the survey, we rotated the telescope along the azimuth and the elevation axes at fixed intervals, observing the target positions for each rotation angle. The measured target positions form arcs, from which we can estimate the rotation axes of the telescope; the origin of the axes was determined as the center of the SLR telescope. For the calculation of the local tie, we used the software pyaxis, developed by Land Information New Zealand (LINZ).

In our presentation, we will show the methods of our survey and calculation described above, and the estimated local tie vector. As of January 2021, we are preparing to submit the co-location SINEX file to the IERS, to contribute to the construction of the upcoming ITRF2020.
Assessment of seismic ambient noise parameter estimation and wavefield decomposition in WaveDec
Authors: Fotouhimehr Mehrdad , Shabani Elham
Published: March 2021

Knowledge about seismic ambient noise wavefield through decomposition into different participant waves is of special importance in geophysical studies. In this study, WaveDec technique (Maranò et al., 2012) as an array statistical signal processing technique was used to decompose seismic ambient noise wavefield and to estimate wavefield parameters. In this method, the measurements from all components of stations and parameters of interest are modeled jointly which leads to significant improvement in extracting characteristics of surface waves. Considering the contribution of both Love and Rayleigh waves in the wavefield, the method estimates the desired parameters including amplitude, phase, azimuth, wave number and the ellipticity angle (for the Rayleigh wave only) based on the Maximum Likelihood Estimation method. One of the main characteristic of WaveDec is estimating the ellipticity angle of Rayleigh waves. This is very beneficial in determining retrograde and prograde particle motion and also in mode distinction.

In the WaveDec algorithm, the Truncated Newton method is used to optimize likelihood functions with respect to wavefield parameters. Furthermore, Bayesian Information Criterion (BIC) is used to select the best model and wave type determination (Rayleigh, Love, body wave or noise). Regarding a group of generated models for different wave types, the one with the smallest BIC is chosen.

We examined consistency of WaveDec algorithm by applying different numerical optimization methods; Truncated Newton, L-BFGS-B quasi-Newton and simplex-based Nelder-Mead methods. Furthermore, different model selection criteria; BIC, Akaike Information Criterion (AIC) and Hannan–Quinn Information Criterion (HQC) were examined to study the quality of generated models. They possess different penalty terms to avoid overfitting the models on data. All possible pairs of optimization methods and model selection criteria were utilized and replaced in WaveDec algorithm. In order to compare the resultant dispersion curves of surface waves and ellipticity angle curves of Rayleigh waves, SESAME model M2.1 synthetic data and some seismic ambient noise measurements in Colfiorito basin in Italy (Array B) were analyzed.
From field to stream: Tracing streambed organic carbon origins at a catchment scale
Authors: Wiltshire Katy , Glendell Miriam , Waine Toby , Grabowski Robert , Thornton Barry , Meersmans Jeroen
Published: March 2021

Quantifying organic carbon (OC) levels and the processes altering them is key in unlocking soils potential as a mediator of climate change through sequestration of atmospheric CO2. In areas of high soil erosion increased fluxes of OC across the terrestrial-aquatic interface are likely and understanding these fluxes is crucial in integrating lateral OC fluxes within the carbon cycle. For this study of a small UK catchment, OC mapping and Revised Universal Soil Loss Equation (RUSLE) based erosion modelling provided estimates of proportional soil OC loss coming from each land use. Sediment fingerprinting using n-alkane biomarkers and a Bayesian unmixing model provided a comparison of streambed OC proportions by land use to assess which processes were dominating OC input to streams. Results showed that RUSLE-based soil OC loss proportions exhibited disconnect with sediment fingerprinting OC composition and the river corridor and riparian environment were key zones in regulating terrestrial to aquatic fluxes of OC.