bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term soil warming alters fine root dynamics and morphology, and their ectomycorrhizal fungal community in a temperate forest soil
Authors: Kwatcho Kengdo Steve , Peršoh Derek , Schindlbacher Andreas , Heinzle Jakob , Tian Ye , Wanek Wolfgang , Borken Werner
Published: March 2022

Climate warming is predicted to affect temperate forests severely, but the response of fine roots, key to plant nutrition, water uptake, soil carbon and nutrient cycling is unclear. Understanding how fine roots will respond to increasing temperature is a prerequisite for predicting the functioning of forests in a warmer climate. We studied the response of fine roots and their ectomycorrhizal (EcM) fungal and root-associated bacterial communities to soil warming by 4 °C in a mixed spruce-beech forest in the Austrian Limestone Alps after 8 and 14 years of soil warming, respectively. Fine root biomass and fine root production were 17% and 128% higher in the warmed plots, respectively, after 14 years. The increase in fine root biomass (13%) was not significant after 8 years of treatment, whereas specific root length, specific root area, and root tip density were significantly higher in warmed plots at both sampling occasions. Soil warming did not affect EcM exploration types and diversity, but changed their community composition, with an increase in the relative abundance of Cenococcum at 0 – 10 cm soil depth, a drought-stress tolerant genus, and an increase in short and long-distance exploration types like Sebacina and Boletus at 10 – 20 cm soil depth. Warming increased the root-associated bacterial diversity, but did not affect their community composition. Soil warming did not affect nutrient concentrations of fine roots, though we found indications of limited soil phosphorus (P) and potassium (K) availability. Our findings suggest that, in the studied ecosystem, global warming could persistently increase soil carbon inputs due to accelerated fine root growth and turnover, and could simultaneously alter fine root morphology and EcM fungal community composition towards improved nutrient foraging.
Colloid-facilitated transport of hydrolytic enzymes in soils
Authors: Guber Andrey , Kravchenko Alexandra
Published: March 2022

Colloids are known to facilitate transport of a broad variety of chemicals and microorganisms in soils. Extracellular hydrolytic enzymes, produced by many soil microorganisms and plant roots, have high affinity to clay and silt particles constituting soil mineral colloids (SMC). Therefore, those enzymes can be released jointly with colloids from soil matrix during high water flow events and transported convectively attached to the colloids carried by the water flow. At the same time hydrolytic enzymes are often considered as free-mobile proteins with a self-propelled diffusion mechanism. Current literature lacks any information on enzyme transport in soils, and it is not clear whether enzymes are transported and, if so, whether they are transported in free- or colloid-associated form. Studying enzyme transport in soils is challenging due to infeasibility of their enumeration in soil solutions and suspensions, differences in activity of free and colloid-associated enzymes, the influence of colloid size and composition, pH and ionic strength in the colloidal suspensions on the enzyme activity. This study presents the first experimental evidence of enzyme transport in soils facilitated by SMC in sandy, loamy and two sandy-loam soils. Its results suggest from 50 to 80% of transported hydrolytic enzymes are associated with transport of coarse SMC. The remaining 20 to 50% of enzymes are likely transported by organic colloids and fine SMC (Ø < 1 mm). The ionic strength played a dual role in the joined enzyme and colloidal transport: (1) by affecting dispersion and release of SMC colloids from soil; and (2) modifying optimum pH of enzymatic activity in released colloidal suspensions. Our results provided insights into factors governing plant-soil-microbial interactions through the transport and activity of hydrolytic enzymes. Support for this research was provided by the NSF LTER Program (DEB 1027253) at the Kellogg Biological Station, by USDA NC1187 project, by the Great Lakes Bioenergy Research Center, U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under Award Number DE-SC0018409.
GRACE Follow-On Accelerometer Data Recovery by High-Precision Environment Modelling
Authors: Huckfeldt Moritz , Rievers Benny , Wöske Florian , List Meike
Published: March 2022

The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) satellites are equipped with high-precision three-axis accelerometers to measure all non-gravitational accelerations acting on the satellites. The accelerometer data are mainly used to account for the influence of these accelerations in the gravity-field-recovery process. Unfortunately, after only one month in orbit the accelerometer on one of the two satellites produced decreasingly accurate measurements. Due to this, the GRACE-D accelerometer data have to be replaced by artificial data. The procedure for the official GRACE-FO Science Data System (SDS) data products is a so called transplant of GRACE-C data.

As an alternative approach, we present a modelling method, where the GRACE-D accelerometer data are based on high-precision non-gravitational force and disturbance modelling. We compare our modelled data to thruster-free accelerometer data derived from the official SDS data products. With this, we can evaluate the performance and show details of our approach. For example, the influence of an in-situ drag-coefficient estimation based on Sentman’s approach. In contrast to other GRACE-FO accelerometer-data-recovery approaches, no transplant of data is incorporated.

This work is part of the Collaborative Research Center 1464 TerraQ and funded by DFG.

 
Microphysical sensitivities in global storm-resolving simulations
Authors: Naumann Ann Kristin , Esch Monika
Published: March 2022

In global storm-resolving models (SRMs), that resolve convection explicitly instead of parameterizing it, microphysical processes are now fundamentally linked to their controlling factors, i.e., the circulation. While in conventional climate models the convective parameterization is one of the main sources of uncertainties (and a popular tuning parameter), this role might be passed on to the microphysical parameterization in global SRMs. In this study, we use a global SRM with two different microphysical schemes. For each scheme we do several sensitivity runs, where in each run we vary one parameter of the applied microphysics scheme in its range of uncertainty. We find that the two microphysics schemes have distinct signatures, e.g., in how condensate is partitioned between ice and snow. In addition, perturbing single parameters of each scheme also affects condensate amounts and hence the heat budget of the tropics. Among the parameters tested, the model is particularly sensitive to the ice fall speed and the width of the raindrop size distribution, which both cause several 10s W/m2 variation in radiative fluxes. Overall, microphysical sensitivities in global SRMs are substantial and resemble inter-model differences such as in the DYAMOND ensemble. 
Monitoring changes in temporary stream networks during rainfall events
Authors: von Freyberg Jana , Bujak Izabela , Rinaldo Andrea , van Meerveld Ilja
Published: March 2022

Stream networks are important flow pathways along which water transports solutes, sediments and affects living communities. Field observations in headwater catchments have shown that the networks of actively flowing channels are not static, but rather expand and contract over time, depending on the intensity and timing of hydro-climatic forcing. Until now, however, flowing stream networks (FSNs) have been mapped only sporadically and environmental tracer data to explore the varying stream-landscape connectivity are lacking. Thus, little is known about how and why these networks change and what the implications are for streamflow, water quality and biodiversity. 

To gain detailed insights into the mechanistic links between FSNs and catchment hydrological processes, we investigated two 4-ha head watersheds in the Alptal valley in central Switzerland. We deployed a wireless sensor network in the field to obtain spatially distributed continuous data of flow occurrence. In addition, we conducted multiple mapping surveys using a self-developed mobile phone application. Our data show that the total flowing stream length increased rapidly by more than a factor of 3 during individual rainfall events. This suggests that different water stores become dynamically connected to the stream network and disconnect again during subsequent dry periods. We test this hypothesis by linking short-term changes in FSN length to variations in subsurface water storage and water chemistry. The results help to broaden our understanding of flow intermittency in pre-Alpine headwater catchments, and thus aids in developing effective strategies to protect ecosystems dependent on temporary flow conditions.
Interannual Variability of Red Sea Overflow Water Pathways in the Western Arabian Sea in an Eddy Rich Ocean Reanalysis 
Authors: Menezes Viviane
Published: March 2022

The present study investigates the interannual variability of the advective pathways of the Red Sea Overflow Water (RSOW) in the western Arabian Sea using Lagrangian particle tracking simulations as a proxy indicator for the poorly understood RSOW spreading. The RSOW, formed in the Red Sea interior, is the primary source of salt for the Indian Ocean intermediate layer and very likely an important source of oxygen for the oxygen-depleted mid-depth water of the Arabian Sea. However, the RSOW pathways and their interannual variability in the open ocean are barely understood. Here, we focus on the western Arabian Sea. The study is based on the Eddy rich Mercator GLORYS12 ocean reanalysis (1/12ohorizontal resolution; ~8 km in the Arabian Sea), which assimilates most satellite and in-situ observations collected between 1993 and 2018 and reproduces relatively well the climatological seasonal cycle of the RSOW to the Gulf of Aden, essential characteristics of the exchange at the Strait of Bab al-Mandab, and the Gulf’s intermediate circulation. For evaluating the pathways interannual variability, tens of thousands of particles were released each year between 1993 and 2013 (every 5-days) in the westernmost part of the Gulf of Aden within the RSOW isopycnic layer (27-27.6 kg/m3; ~600-1000 m). These particles were tracked over five years using the Parcels toolbox. Transit times from the outflow area to the western Arabian Sea are around three years. Statistical analysis of trajectories reveals a strong interannual variability in the RSOW pathways for the first time. The interannual variability of the western boundary undercurrents (Socotra and Somali) is evaluated in characterizing the pathways variability. Impacts on the intermediate-depth salinity are also investigated, although the scarcity of in-situ observations posed a significant limitation for the salinity analysis.
Do Atlantic-European Weather Regimes Physically Exist?
Authors: Hochman Assaf , Messori Gabriele , Quinitng Julian , Pinto Joaquim G. , Grams Christian
Published: March 2022

The subseasonal variability of the extratropical large-scale atmospheric flow is characterized by recurrent or quasi-stationary circulation anomalies, termed weather regimes. Despite the usefulness of these regimes in numerous meteorological and socioeconomic applications, there is an ongoing debate as to whether they represent physical modes of the atmosphere, or are merely useful statistical categorizations. Here, we answer this question for wintertime Atlantic-European regimes. We argue that dynamical systems theory applied to a refined regime definition provides strong evidence in support of most weather regimes being physically meaningful. This finding underpins the broad relevance of weather regimes, for understanding the response of the atmosphere to external forcing, supporting subseasonal weather forecasting, and down scaling of climate projections.

Referene

Hochman, A., Messori, G., Quinting, J. F., Pinto, J. G., & Grams, C. M. (2021). Do Atlantic-European weather regimes physically exist? Geophysical Research Letters, 48, e2021GL095574. https://doi.org/10.1029/2021GL095574
The weakening of AMOC highly linked to climate warming outside the Arctic
Authors: Chen Jiao , Wang Xidong , Wang Xuezhu
Published: March 2022

Global warming since the industrial revolution has led to a series of changes in the atmosphere and ocean. As a key indicator of global ocean circulation, AMOC has shown a weakening in recent decades from both the observed and simulated results. This process which is not only affected by the local variation of the Arctic, but also by the ocean and atmosphere circulation changes in the middle and lower latitudes, might have important implications for future global climate changes. We employ the Alfred Wegener Institute Climate Model (AWI-CM 1.1 LR) and a method of perturbing coupled models to quantify and understand the impact of anthropogenic warming on the slowdown of AMOC. Conducted one control (CTRL) experiment and three sensitivity experiments (60N, 60NS, and GLOB) in which CO2 concentration were abruptly quadrupled either regionally (60N-north of 60°N, 60NS-south of 60°N) or globally (GLOB). The goal of our research is to identify the response of AMOC weakening to the quadrupling of CO2 concentration in different regions and provide future insight into ocean circulation changes in the context of climate warming. Our results show that CO2 forcing outside the Arctic dominates the weakening of AMOC. In a warming climate, the poleward heat transport increased due to the extra-Arctic CO2 forcing, which enhanced the upper ocean average stratification within the mixed-layer depth over Nordic Seas and Labrador Sea and thus weakens the AMOC to a large extent. The warming in upper-layer also lead to the dominant role of temperature contribution to stratification. However, in both the deep convection regions, the mechanism resulting in the strengthening of stratification might be quite different.
NWM/GNSS tightly coupled tropospheric delay estimation and application on an unmanned aerial vehicle (UAV) platform
Authors: Zhang Zhenyi , Zhang Weixing , Lou Yidong , Zhou Yaozong , Bai Jingna , Zhang Zhixuan
Published: March 2022

Water vapor is of great importance to the atmosphere and weather research. Airborne GNSS-based tropospheric delay estimation can reveal the atmosphere profile information, which is of more importance than site-based products and acts as an independent observation for meteorological application. On the other hand, progress in the meteorological community such as numerical weather models (NWMs) and forecast operations have the potential to augment GNSS. Many studies have investigated methods for applying NWMs in GNSS, mainly considering NWMs as a priori information. However, most methods implemented are merely suitable for static ground stations. They may not be optimal for dynamic platforms like unmanned aerial vehicles (UAVs) since the troposphere condition changes dramatically with vertical velocity and height. Under this background, we propose an NWM/GNSS tightly coupled method to take the best advantage of NWMs into GNSS data processing. The technique utilizes NWMs as a priori and considers the vertical distribution of the atmosphere to adaptively adjust the stochastic model for tropospheric delay estimation depending on the actual circumstance. The proposed method has been evaluated by an experiment using UAV and Global Forecast System (GFS) and found an improvement of precision and stability of tropospheric delay estimates.
Complexity of rainfall dynamics in India in the context of climate change
Authors: Deepthi Bhadran , Sivakumar Bellie
Published: March 2022

Global climate change has become one of the major environmental issues today. Climate change impacts rainfall (and other hydroclimatic processes) in many ways, including its temporal and spatial variability. Hence, understanding the impact of climate change on rainfall is important to devise and undertake more effective and efficient adaptation and management strategies. The present study attempts to determine the temporal dynamic complexity of monthly historical and future rainfall in India at a spatial resolution of 1º × 1º. The historical and future rainfall data are simulated from 27 General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The historical rainfall consists of the rainfall data simulated by GCMs for the period 1961–2014, and the rainfall simulated by the GCMs under shared socio-economic pathway scenarios (SSPs) constitutes the future rainfall. Four scenarios (SSP126, SSP245, SSP370, and SSP585) and two different timeframes (near future (2015–2060) and far future (2061–2099)) are considered to determine how the rainfall and its dynamic complexity vary across the scenarios and timescales. The false nearest neighbor (FNN) algorithm is employed to determine the dimensionality and, hence, the complexity of the rainfall dynamics. The algorithm involves two major steps: (i) reconstruction of the single-variable rainfall time series in a multi-dimensional phase space; and (ii) identification of “false” neighbors in the reconstructed phase space and estimation of the dimension of the rainfall time series. The results suggest that the FNN dimensions of both the historical rainfall and future rainfall simulated by the 27 GCMs across India under all scenarios range from 3 to 20, indicating low to high-level complexity of the rainfall dynamics. However, only less than 1% of the study area shows high-level complexity in historical and future rainfall dynamics. Moreover, around 20 GCMs exhibit low to medium-level complexity of rainfall dynamics in 80% of the study area, with the dimensionality in the range from 3 to 10. Therefore, considering both the historical rainfall and future rainfall under all the four scenarios and the two timeframes considered in this study, the number of GCMs simulating rainfall that exhibits dimensionality in the range 11 to 20 are few. This may be an indication that the complexity of rainfall dynamics in India in the future will be low-to-medium dimensional.
Estimating heavy ions escape rate from Mars using hybrid model and observations from MAVEN
Authors: Zhang Qi , Holmström Mats , Wang Xiaodong , Fatemi Shahab
Published: March 2022

We apply a new method, coupling a hybrid plasma model (ions as particles, electrons as a fluid) and measurements from the Mars Atmosphere and Volatile Evolution (MAVEN) mission, to calculate heavy ion escape rates from Mars. With this method, we acquire estimates of the escape rate orbit by orbit in different upstream conditions. We have investigated how the estimated ion escape depends on the assumed composition of heavy ions, the solar wind velocity aberration and the amount of alpha particles in the solar wind. We also estimate the amount of tail escape and radial escape and compare the model results with  recent Mars Express and MAVEN studies.
Changes in soil aggregate fractions, stability and associated organic carbon and nitrogen in different land use types in the Loess Plateau, China
Authors: wu heng
Published: March 2022

Rational land use can enhance soil nutrient sequestration and control erosion, but the mechanisms of the ecological restoration on soil aggregate-associated carbon and nitrogen are still not well understood. A large-scale ecological restoration program was launched in the Loess Plateau during 1990s. The ecological restoration programs involved converting slope farmland to forest, grassland, shrub land and terrace. We studied their effects in relation to slope land as control on soil aggregate structure and stability, and their associated organic carbon and total nitrogen contents to 60 cm soil depth in the Loess Plateau. Our results indicate that the restoration practices reduced soil aggregate fragmentation, increased soil structure stability and transformed micro-aggregates into small and large aggregates. Comparing with the soil aggregate >0.25mm in slope land, the amount of that in forest, grass land, shrub land and terrace increased by 71%, 66%, 46%, and 35%, respectively, which improved soil health overall. The mean weight diameter (MWD) of aggregate indicated that soil aggregate stability (SAS) increased and soil hydraulic erosion resistance improved. In conclusion, ecological restoration directly or indirectly affected SAS through the influence of soil organic carbon (SOC) and total nitrogen (TN) in different soil layers. The results would provide a scientific basis for soil quality control and rational use of land resources.
Remotely sensed dune movement rates in desert margins of Central Asia over five decades using satellite imagery
Authors: Dörwald Lukas , Walk Janek , Lehmkuhl Frank , Stauch Georg
Published: March 2022

Remote sensing is being used widely to detect, map, and monitor environmental changes and remains a rapidly developing field. The detection of dune movement rates is carried out in field since the 20th century and through remote sensing, once the technical requirements were met in the 1970th (Hugenholtz et al. 2011). A wide variety of imagery from the last four decades is freely available in the archives of Sentinel-2 and Landsat 5 to 8 satellite images with spatial resolutions ranging between 10 and 25 meters. Complementing these data sources, in this study, we additionally used CORONA KH-4B images from the 1960s and 1970s. Despite its age, the KH-4B satellite delivered a considerably high spatial resolution of up to 1.8 m, thus bridging a considerable time gap of high resolution imagery and enabling the detection and mapping of singular dunes and dune fields. These satellites were originally used to record military intelligence images before being declassified for scientific use in 1995. After georeferencing, these images were utilized to detect and quantify the rates and directions of sand dune movement as well as for the estimation of dune height through a simple trigonometric approach.

We focus on single dunes and their movement rates in the high-altitude intramontane Gonghe Basin in Central Asia. The location of the study area at the north-eastern edge of the Asian summer monsoon and the mid-latitude Westerlies makes it especially sensitive to climatic variability (Vimpere et al. 2020). The dominant south easterly dune migration directions are in good agreement with the prevailing wind patterns. Dune heights of ~8–28 meters and ~3-31 meters for the late 1960s and 2020s, respectively, were calculated. Also, movement rates of under one meter up to ~24 meters per year were assessed for the time range of the late 1960s and 2020s.References:

Hugenholtz, C., H., Levin, N., Barchyn, T.E., Baddock, M., C. (2012): Remote sensing and spatial analysis of Aeolian sand dunes: A review and outlook. Earth-Science Reviews 111, 319–334, https://doi.org/10.1016/j.earscirev.2011.11.006

Vimpere, L., Watkins, S., E., Castelltort, S. (2021): Continental interior parabolic dunes as a potential proxy for past climates. Global and Planetary Change, 206: 103622, https://doi.org/10.1016/j.gloplacha.2021.103622
Let’s talk: incorporating stakeholder needs in climate-science based wind resource assessments
Authors: Schaffer Laura , Borowski Johanna , Dörenkämper Martin , Jacob Daniela , Keup-Thiel Elke , Sieck Kevin , Wohland Jan
Published: March 2022

The variable nature of wind power generation poses many challenges. The scientific community has addressed many of these challenges and made much progress in the recent years. These include, for example, quantifying resource variability, constraining future climate change impacts on wind energy, and suggesting robust system designs. Much of this research, however, has been academic in nature and lacks bi-directional interactions with stakeholders who make real world decisions. As an attempt to facilitate more exchange with industry partners, we present first results of a stakeholder workshop. The workshop theme is the role of climate in wind energy site assessments, including aspects related to climate variability and climate change. In addition to direct yield related parameters, such as capacity factors and their variability, we also plan to address relevant indirect effects that are less extensive researched, such as climate-induced changes in bat activity that trigger generation interruptions and blade icing. We report on the workshop design, highlight lessons learned and illustrate how the stakeholder feedback is used in shaping the precise research questions to be addressed in the course of the KliWiSt project [1]. KliWiSt is a German acronym that stands for the impact of climate change on wind energy site assessments. The general transdisciplinary approach can be adapted and used in other stakeholder-oriented research projects.

[1] https://www.climate-service-center.de/science/projects/detail/103308/index.php.en; https://www.iwes.fraunhofer.de/de/forschungsprojekte/aktuelle-projekte/kliwist.html
The effect of uncertain historical ice information on GIA modelling
Authors: Schachtschneider Reyko , Saynisch-Wagner Jan , Klemann Volker , Bagge Meike , Thomas Maik
Published: March 2022

When inferring mantle viscosity by modelling the effects of glacial isostatic adjustment (GIA) a necessary constraint is the external forcing by surface loading. Such forcing is usually provided by a glaciation history, where the mass-conserving sea-level changes are considered solving the sea-level equation. The uncertainties of glaciation history reconstructions are quite large and the choice of a specific history strongly influences the deformation response obtained by GIA modelling. The reason is that any history is usually based on a certain Earth rheology, and mantle viscosity inversions using such models tend to resemble the viscosity structure used for the glaciation history (Schachtschneider et al., 2022, in press). Furthermore, uncertainties of glaciation histories propagate into the respective GIA modelling results. However, to quantify the impact of glaciation history on GIA modelling remains a challenge.

In this study we investigate the effect of uncertainties in glaciation histories on GIA modelling. Using a particle-filter approach we study the effect of spatial and temporal variations in ice distribution as well as the effect of total ice mass. We quantify the effects on a one-dimensional viscosity stratification and derive measures to which extent changes in sea-level pattern and surface deformation depend on variations in ice loading.

 

References:

Schachtschneider, R., Saynisch-Wagner, J., Klemann, V., Bagge, M., Thomas, M. 2021. Nonlin. Proc. Geophys., https://doi.org/10.5194/npg-2021-22
Optimal resolution tomography with error tracking and the structure of the crust and upper mantle beneath Ireland and Britain
Authors: Bonadio Raffaele , Lebedev Sergei , Meier Thomas , Arroucau Pierre , Schaeffer Andrew J. , Licciardi Andrea , Agius Matthew R. , Horan Clare , Collins Louise , O'Really Brian M. , Readman Peter W. , Working Group Ireland Array
Published: March 2022

The maximum achievable resolution of a tomographic model varies spatially and depends on the data sampling and errors in the data. The significant and continual measurement-error decreases in seismology and data-redundancy increases have reduced the impact of random errors on tomographic models. Systematic errors, however, are resistant to data redundancy and their effect on the model is difficult to predict; often this results in models dominated by noise if the target resolution is too high. Here, we develop a method for finding the optimal resolving length at every point, implementing it for surface-wave tomography. As in the Backus-Gilbert method, every solution at a point results from an entire-system inversion, and the model error is reduced by increasing the model-parameter averaging. The key advantage of our method consists in its direct, empirical evaluation of the posterior model error at a point.

We first measure interstation phase velocities at simultaneously recording station pairs and compute phase-velocity maps at densely, logarithmically spaced periods. Numerous versions of the maps with varying smoothness are then computed, ranging from very rough to very smooth. Phase-velocity curves extracted from the maps at every point can be inverted for shear-velocity (VS) profiles. As we show, errors in these phase-velocity curves increase nearly monotonically with the map roughness. We evaluate the error by isolating the roughness of the phase-velocity curve that cannot be explained by any Earth structure and determine the optimal resolving length at a point such that the error of the local phase-velocity curve is below a threshold.

A 3-D VS model is then computed by the inversion of the composite phase-velocity maps with an optimal resolution at every point. Importantly, the optimal resolving length does not scale with the density of the data coverage: some of the best-sampled locations display relatively low lateral resolution, due to systematic errors in the data.

We apply this method to image the lithosphere and underlying mantle beneath Ireland and Britain. Our very large data produces a total of 11238 inter-station dispersion curves, spanning a very broad total period range (4–500 s), yielding unprecedented data coverage of the area and providing state-of-the-art regional resolution from the crust to the deep asthenosphere. Our tomography reveals pronounced, previously unknown variations in the lithospheric thickness beneath Ireland and Britain, with implications for their Caledonian assembly and for the mechanisms of the British Tertiary Igneous Province magmatism.
Extratropical high-wind feature identification using a probabilistic random forest
Authors: Eisenstein Lea , Schulz Benedikt , Knippertz Peter , Pinto Joaquim G.
Published: March 2022

Strong winds associated with extratropical cyclones are one of the most dangerous natural hazards in Europe. These high winds are mostly connected with four mesoscale dynamical features: the warm (conveyor belt) jet (WJ), the cold (conveyor belt) jet (CJ), (post) cold-frontal convective features (CFC) and the sting jet (SJ). While all four have high wind gust speeds in common, the timing, location and some further characteristics typically differ and hence likely also the forecast errors occurring in association with them.

Here we present an objective identification approach for the four features listed above, based on a probabilistic random forest using each feature’s most important characteristics in wind, rainfall, pressure and temperature evolution. The main motivations for this are to generate a climatology for Central Europe, to analyse forecast errors specific to individual features, and to ultimately improve forecasts of high wind events through feature-dependent statistical post-processing. To achieve this, we strive to identify the features in irregularly spaced surface observations and in gridded analyses and forecasts in a consistent way.

To train the probabilistic random forest, we subjectively identify the four storm features – as well as high cold sector winds – in ten winterstorm cases between 2017 and 2020 in both hourly surface observations and high-resolution reanalyses of the German COSMO model over Europe, using an interactive data analysis and visualisation tool. Results show that mean sea-level pressure (tendency), potential temperature, precipitation amount and wind direction are most important for the distinction between the features. From the random forest we get probabilities of each feature occurring at the single stations, which can be interpolated into areal information using kriging. While the observational data are limited to surface measurements, the gridded data includes further useful parameters and the possibility to consider vertical structures.

The results show a good identification of CJ, CFC and WJ, while a distinction between SJ and CJ is difficult using surface observations alone, such that the two features are considered together at this stage. A climatology is currently being compiled for both surface observations and the reanalyses over a period of around 20 years using the respective trained probabilistic random forests and further for high-resolution COSMO ensemble forecasts, for which we want to analyse forecast errors and develop feature-dependent postprocessing procedures.
How weather and climate affect renewable electricity sources in Norway
Authors: Haddeland Ingjerd , Sidelnikova Maria
Published: March 2022

European electricity production is increasingly based on renewable energy sources, inspired by ambitious climate politics. Hence, the power system must adapt to larger shares of less flexible electricity sources like wind and solar, which depend on fluctuating weather. Here, hydro power inflow, wind power, solar power and electricity demand in Norway are estimated based on meteorological data for the period 1961-2020. The installed capacity of the production technologies is kept constant at 2020 levels throughout the analyses. Mean annual power production is higher than mean annual electricity demand. However, the variability in production potentials is large for all renewable energy sources at time scales ranging from hourly to annual, and power deficits occur occasionally even at the annual scale. Hydro power inflow shows an increasing trend during the period studied, and the relative increase is largest during the winter season. Wind and solar power production are only marginally affected by climate differences in the study period. Electricity consumption decreases somewhat during the 60-year period, due to increasing average temperatures. The combined effect of production and consumption changes is an increase in mean annual surplus of electricity during the period studied. However, although a surplus of electricity exists at the mean annual level, additional available electricity in the form of reservoir storage or import is needed to maintain security of supply within the country.
Decadal change of the Apulia microplate motion preceding the Mw 6.4, 26 November 2019 Durres (Albania) earthquake 
Authors: Í Dali Udbø Bjartur , Iaffaldano Giampiero , Martin de Blas Juan
Published: March 2022

Contemporary rigid motions of tectonic plates, which are inferred from geodetic data collected over several years, are commonly assumed to remain steady over the earthquake cycle. Such a tenet is predicated on the notion that stresses associated with the earthquake cycle might not be sufficient to overcome the asthenosphere viscous resistance at the lithosphere base, which counters plate--motion changes. This, however, has never been verified against observations. Here we focus on the Apulia microplate, a rigid tectonic unit located in the buffer zone between the Eurasia and Nubia plates, to show that its rigid motion constrained by Global Positioning System time series has changed in the decade preceding the Mw 6.4, 26 November 2019 Durres (Albania) earthquake. Furthermore, we investigate whether such a change could be the result of the interseismic stress buildup associated with the Durres earthquake cycle. 

 
Monitoring wood formation dynamics of Pinus pinaster Aiton in a burned area of Vesuvio National Park
Authors: Niccoli Francesco , Pacheco-Solana Arturo , De Micco Veronica , Battipaglia Giovanna
Published: March 2022

Forest fires are becoming more intense and recurring due to climate change and are increasingly threatening the integrity and functionality of forests worldwide. Trees’ resilience is closely influenced not only by direct fire damages, but also by pre-existing climate stress conditions, such as high temperatures and water deficit. Fire wounds and extreme climate events can impair plant physiology triggering tree mortality in the medium and long term. Therefore, understanding the links between fire, climate and tree health is essential to anticipate the impacts of global warming and to plan climate-adapted forest management strategies. In this context, our research aims to study the post-fire effects on a Pinus pinaster Aiton forest growing in Vesuvius National Park, a particularly drought prone area in Southern Italy, comparing plants with severe damage to the canopy with non-defoliated trees. We combined inter-annual analyses of dendrochronology, carbon and oxygen isotope composition in tree rings, and intra-annual monitoring of xylogenesis to explore the effects on tree-growth, ecophysiological processes and wood formation dynamics. The tree-ring approach showed that crown damage compromised the photosynthetic activity of burned trees, with a decrease in tree-growth in the medium term compared to control trees. Moreover, the xylogenesis analysis demonstrated a delay in phenology and a lower xylem productivity and plasticity of the defoliated trees, as well as the negative influence of hot and dry months on cambial production. Our findings suggested that although maritime pine can survive severe forest fires in the short term, a severe crown defoliation and prolonged drought conditions can compromise the species' eco-physiological functions reducing the chances to regain the pre-disturbance productivity rates.
High-resolution deformation maps from the Southern-Eastern Alps compiled from 5-yr-long radar interferometric time-series
Authors: Metzger Sabrina , Lacecký Milan , Kakar Najibullah
Published: March 2022

Entering the terminal phase of continental collision, the European Alps exhibit surface deformation rates at the mm-level. Uplift peaks in the Central Alps at 2-3 mm/yr as a result of the post-glacial isostatic rebound, slab tearing, and erosion. Horizontal rate changes of <2 mm/yr are observed in the Southern-Eastern Alps due to the anticlockwise rotation of the Adriatic lithosphere. Here, N–S shortening is primarily accommodated at the densely-populated foothills of the Southern Alps, where seismicity is abundant and includes M6+ earthquakes like the devastating Mw6.5 Friuli earthquake in 1975. Further north and beyond the ESE-trending, dextral Periadriatic fault, the Eastern Alps extrude into the Pannonian basin. Today’s fault slip rates are constrained by Global Navigation Satellite System (GNSS) data with an inter-station distance too sparse to provide a detailed insight into plate locking—a vital component of estimating the fault’s seismic potential.

We present 4D-deformation data of the SE-Alps in unprecedented resolution (~400 m, 6 days). The rate maps were derived from radar-interferometric time-series collected since 2017 by the European Sentinel-1 satellites. Each of the assembled 240-km-wide radar tiles consists of 300+ images. The interferograms were automatically generated, phase-unwrapped, and corrected for atmospheric and topographic signal contributions. We estimated the deformation rates using the LiCSBAS time-series analysis software that involves a small-baseline approach and accounts for spatio-temporal coherence and seasonality. By tying the individual, relative InSAR rates—observed in two look directions—into a Eurasian reference frame based on by published GNSS rates we decompose them into east and vertical rates.

Our results illuminate the extreme, to which we can push the InSAR signal-detection threshold if the signal-backscatter properties are as challenging as in the vegetated SE-Alps: The predominant, vertical rates result from a mixture of isostatic, tectonic and anthropogenic processes, overlaid by a soil-moisture bias; the horizontal shortening rates align northwards, to which the radar satellites is least sensitive. Nevertheless, our rates provide new, dense deformation data and highlight processes yet undetected by the GNSS monitoring network.
Port Alfred upwelling: A numerical modelling approach
Authors: Taukoor Sheveenah , Penven Pierrick , Ansorge Isabelle , Mashifane Thulwaneng , Lamont Tarron
Published: March 2022

Port Alfred upwelling, located on the southeast African shelf, lies on the inshore edge of a western boundary current, the Agulhas Current. It is a semi-permanent upwelling covering a width of 15-100 km. The mechanisms responsible for these cold water events have not been studied in depth due to the poor sampling of Port Alfred. Previous studies have relied on in situ measurements and remote sensing datasets and suggested that this upwelling was current-driven while other studies claimed that it could be wind-driven. Recently, it was also argued that it could be due to a combination of the current and wind forcing.

 

In this study we aimed at identifying the dominant forcing drivers triggering this upwelling. Using the daily simulations of a CROCO model of a horizontal spatial resolution of ~2.5km, we explored its spatial and temporal characteristics. Building up from previous studies, we investigated several potential hypotheses from a modelling perspective. Some of these forcing mechanisms included the strength of the current, wind, the meandering of the current and the eddy. By performing a combined principal component analysis, we tested each hypothesis and found that a combination of current strength, meander and wind would lead to a stronger upwelling event, while some of the forcing mechanisms could trigger a weaker cold event individually.

 

This phenomenon is known to cause an increase of nutrients at the surface, setting the ideal conditions for primary production, a significant oceanographic process for biodiversity. Shedding more light on these cold water events and the main drivers allows oceanographers to focus more attention on Port Alfred in the future. It will also reinforce policymakers to consider Port Alfred as a marine protected zone.
Slope instabilities and gas hydrates dissociation in the western Black Sea since the last glacial maximum
Authors: Fabre Maud , Loncke Lies , Riboulot Vincent , Sultan Nabil , Ker Stephan
Published: March 2022

Marine landslides, which are observed worldwide along continental slopes, constitute the most important processes reworking sedimentary deposits and a major geohazard for marine and coastal domains. They can generate potentially the destruction of marine infrastructures through the formation of turbidity currents and/or hazardous tsunamis. In the Romanian sector of the Black Sea, high amounts of methane are detected in the sediments and at the seafloor through the identification of gas seeps in the water column. They occur on the upper slope, mostly outside the large gas hydrates system occurring in the sediment below -660 m water depth, where methane is trapped in ice cages that act as a buffer zone hampering methane to reach the water column. New geophysical and geotechnical dataset acquired along the Romanian margin reveals that the active seepage zone is associated with numerous slope failures, which incised the continental upper slope. Is there a possible relationship between gas hydrate system and recent slope instabilities? Could intense free gas emissions and/or gas hydrates dissociation have triggered such geohazards? To answer these questions, we present (1) an high resolution mapping and, more important, dating of landslides since the last glacial maximum (35 ka), (2) results of numerical modelling showing the evolution of gas hydrates stability zone inside the sediments since the last 35 ka taking into account the environmental variations that occurred during this time lapse (geothermic gradient, temperature, salinity and sea level).

The models highlight the major effect of environmental changes and particularly the glacial/interglacial cycles and salinity variations on the extent of the gas hydrates. The confrontation of those models with slide extensions, depths and ages allows to better discuss the respective influences of gas hydrates dissociation, stratigraphic overpressure and seepage on slope instability since the last glacial maximum.
Experimental and numerical study of heat and mass transport in snow in case of strong temperature gradient conditions.
Authors: Bouvet Lisa , Calonne Neige , Geindreau Christian , Flin Frédéric
Published: March 2022

A new experiment has been conducted to characterize experimentally heat and mass transport as well as metamorphism evolution during temperature gradient conditions. To be able to appreciate fine scale as well as larger scale processes, the experimentation lasted 3 weeks with a strong gradient of 100 K m-1 and a mean temperature of -9.5°C. The studied snow layer was 12 cm thick and had a horizontal surface of 0.5 m2. Temporal monitoring of the snow was made through 17 micro-tomographies at specific spots with a resolution of 8 μm and 9 micro-tomographies on full vertical profiles at 21 μm. The layer was also instrumented using 10 temperature and humidity sensors and 7 precise temperature sensors recording at different locations during the whole process. This experiment showed precisely the development of facets and depth hoar in the snow matrix, and leads to interesting results concerning the evolution of heat and mass fields during a strong temperature gradient. The results of this experiment are finally compared to numerical results predicted by coupled heat and mass transport models such as the one of Calonne et al., 2015.
Markovian features of the Super-MAG Auroral Electrojet Index
Authors: Benella Simone , Consolini Giuseppe , Stumpo Mirko , Alberti Tommaso
Published: March 2022

Earth's magnetospheric dynamics displays dynamical complexity during magnetic substorms and storms. This complex dynamics includes both  stochastic and deterministic features, which manifest at different timescales. In this work, we investigate the stochastic properties of the  magnetospheric substorm dynamics by analysing the Markovian character of the SuperMAG SME time series, which is used as a proxy of the energy  deposition rate in the auroral regions. In detail, performing the Chapman-Kolmogorov test, the SME dynamics appears to satisfy the Markov condition  below 100 minutes. Moreover, the Kramer-Moyal analysis allows to highlight that a purely diffusive process is not representative of the magnetospheric  dynamics, as the fourth order Kramers-Moyal coefficient does not vanish. As a consequence, we show that a model comprising both diffusion and  Poisson-jump processes is more suitable to reproduce the SME dynamical features at small scales. A discussion of the similarities and differences  between this model and the actual SME properties is provided with a special emphasis on the metastability of the Earth’s magnetospheric dynamics.  Finally, the relevance of our results in the framework of Space Weather is also addressed.