bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of ecosystem resilience to drought based on drought intensity and recovery time
Authors: Yao Ying
Published: March 2022

Drought is one of the most complex hydrological and climate disasters, causing damage to ecosystem structure and function. Ecosystem resilience is considered a key concept for understanding and describing the response of ecosystems to drought. Recovery time, as an important measure of resilience, has been widely used to assess ecosystem resilience to drought, but there is a deficiency in distinguishing the difference in recovery time under various drought intensities. On the basis of the existing assessment of drought resilience based on recovery time, we defined a new resilience indicator using an exponentially fitted curve to characterize the relationship between drought intensity and the corresponding recovery time, and the resilience was quantified by the curve area. Resistance represents the capacity of ecosystems to remain stable during droughts, and we quantified the resistance indicator by the ratio of the frequency of no vegetation loss during drought to drought frequencies. Our results showed that the ecosystem resilience to drought increased from arid to sub-humid regions in China’s dryland, and resistance was the lowest in the semiarid region. There was a trade-off between resilience and resistance: grassland had higher resilience and lower resistance than forestland. Drought memory contributed to the high resilience in the case of high drought frequency. These findings enriched the identification of the resilience of ecosystems to drought and the relationship between resilience and resistance and drought frequency in drylands.
The Characteristics and Significance of Hydrodynamical Internal Variability in Modelling Dynamics in Marginal Seas
Authors: Lin Lin , von Storch Hans , Chen Xueen , Tang Shengquan
Published: March 2022

Internal variability, unprovoked by external forcing, emerges in the hydrodynamics of the marginal seas. Ensemble ocean simulations are used to analyze the characteristics, scales, and intensities of such variability in the Bohai, Yellow Sea, and South China Sea. With the signal defined as the covariation in the ensemble, and the noises as the independent variations, a scale dependency of the Signal-to-Noise Ratio (S/N ratio) is found in the Bohai, Yellow Sea, and South China Sea. The external forcing and related signal are dominant for large scales, while most of the internal variability is generated for small scales. The intensities of internal variability of the Bohai and Yellow sea are about half of the intensities of South China Sea, likely because eddies are less energetic in the Bohai and Yellow Sea, which likely is the main source of noise in South China Sea.

In addition, we investigate the effect of tides on internal variability in the Bohai and Yellow Sea by three ensembles of numerical experiments with tidal forcing, with half tidal forcing, and without tidal forcing. When the tides are weakened or turned off, the S/N ratios are reduced in large and medium scales, more so in the Yellow Sea than in the Bohai. The increase in the S/N ratio is largest for large scales and for depth-averaged velocity. The reduction in tidal forcing results in an approximately 30% increase in S/N ratios in the Bohai at large scales. Thus, the absence of tidal forcing favours the emergence of unprovoked variability at large and medium scales but not at small scales. We suggest that the main mechanism for the increase of covarying variability when tides are active, is the additional mixing induced by the tides.
Modelling Abrupt Transitions in Past Ocean Circulation to Constrain Future Tipping Points
Authors: Vettoretti Guido , Jochum Markus , Ditlevsen Peter
Published: March 2022

Recent observationally based studies indicate that the Atlantic Meridional Overturning Circulation (AMOC) and the Greenland Ice Sheet (GIS) may be approaching critical thresholds or tipping points, although the timing is uncertain. The connection between both Greenland meltwater fluxes and anthropogenic greenhouse gas emissions and their impact on the future state of the AMOC is also uncertain. Here we investigate the role of ocean vertical mixing within the interior and surface boundary layer (the K-Profile Parameterization (KPP)) on past millennial scale climate variability in a coupled climate model. Previous studies have demonstrated a sensitivity of the period of millennial scale ice age oscillations to the KPP scheme. Here we show that small changes in the profiles of vertical mixing under ice age boundary conditions can drive the AMOC through a Hopf bifurcation and result in the appearance of millennial-scale AMOC oscillations. This has implications on whether changes in tidal energy dissipation in the coastal and deep ocean are important for modelling past climate variability. More importantly, the same changes in ocean vertical mixing can impact the stability and hysteresis behaviour of the modern AMOC under freshwater input to the North Atlantic as well as leading to abrupt transitions in AMOC strength under a doubling of carbon dioxide concentrations in the atmosphere. We show how understanding the sensitivity of the AMOC to ocean vertical mixing parameterizations used in coupled Earth System models may be important for constraining future climate tipping points.
Understanding sedimentary provenance and sub-surface lithostratigraphy of Central Gangetic Basin
Authors: Bose Oindrila , Mukherjee Abhijit , Sengupta Probal , Shaw Ashok , Das Prerona , Layek Mrinal Kanti , Smith Martin
Published: March 2022

River Ganges, being one of the largest trans-boundary river, flows along the northern part of the Indian subcontinent contributes sediment to, one of the largest alluvial basin in the world, the Indo-Gangetic basin. The basin is composed of sediments sourced from the Himalayas and also from peninsular India. This river has experienced rapid and multiple migrations through its geological history and varied fluvial geomorphic processes, tectonic controls and complex climatic interplay have led to the deposition of different lithofacies within this Central Ganges basin (CGB). A provenance study has been started in the CGB in order to understand its geological evolution and reconstruct the regional paleo-environment through subsurface lithostratigraphy. Initial X-ray diffraction data of borehole sediments in CGB shows dominant presence of quartz, feldspar, mica and heavy minerals in varying proportions at different depths. Substantial amounts of kaolinite, smectite, illite and montmorilonite are found in descending proportions within the upper clay layers, where abundance of kaolinite is significantly higher over the other minerals. The upper layers till ~30m comprises of clay having particle size of 2.42μm- 3.12μm, below which are mostly silt and sand layers ranging from 16.4 μm -1.63mm, with fine intercalations of gravel and clay layers in-between.The upper layers are dominated by muscovite indicating a Himalayan origin of the sediments, which shows a sharp decline in abundance below 100 m bgl. Moreover, presence of only zircon as heavy mineral is noted within 100m bgl. In contrast, beyond 100m bgl, the sediments are represented by very low mica content, abundance of pyroxene, and heavy minerals like zircon, rutile, illmanite, and sphene possibly signifying contribution from cratonic areas. Significant quantities of recrystallized and highly altered quartz-feldspathic mass showing clear evidence of strain, are also observed. The disposition of sediments from multiple provenances confirms significant contribution of sediment load from southern tributaries of the Ganges river system which eventually diminishes with time due to temporal and spatial migration of the river.
Surfactant application via drippers for water repellent soil remediation enhances agrochemicals leaching through preferential flow pathways
Authors: Ogunmokun Felix Abayomi , Wallach Rony
Published: March 2022

Soil water repellency has a substantial effect on soil-water retention and flow. Typically, soils are denoted water repellent when they resist spontaneous wetting by water for more than five seconds. Soil water repellency reduces infiltration capacity, increases surface runoff, soil erosion, and induces uneven distribution of water content, including preferential flow pathways. We describe an in-situ study aiming to remediate these soils by surfactant application using a commercial drip system.

The study was carried out on a commercial citrus orchard irrigated with secondary treated wastewater, which usage has been shown to induce soil water repellency over time. To relieve the adverse effects of soil water repellency, different concentrations of a nonionic surfactant were applied to the soil using a drip system for three years. The spatial variation of the soil's wettability was characterized by the sessile drop method (contact angle) and water drop penetration time (WDPT) test. The spatial soil-water content distributions and flow were monitored undisturbedly by electrical resistivity tomography (ERT) surveys. Spatial soil-agrochemical distributions along transects where the ERT surveys took place were determined by intensive soil sampling at two depths: 0-20 and 20-40 cm.

The ERT results indicated that while the surfactant application via drippers improved the water repellent soil's wettability, it enhanced the development of preferential flow pathways. Although preferential flow pathways associated with treated wastewater irrigation existed in all soil profiles, they were exacerbated by the surfactant application. Additionally, increased leaching of mobile elements, like Cl, N, and EC, was measured for the surfactant-treated plots. Contrarily, P adsorption to the soil particles was increased in the surfactant plots compared to the untreated plots. While the contact angle along the soil surface showed no difference between the untreated and surfactant treated plots, the WDPT decreased in the latter. These findings indicate that aside from the foreknown causes of preferential flow in soils like earthworms, wet and dry cycles, aliphatic hydrocarbons, etc., localized surfactant application by drippers (point sources) for water repellent soils remediation enhances preferential flow and chemicals leaching. Therefore, a different method for surfactant application that remediates soil water repellency without enhancing agrochemicals leaching should be considered and examined.
Preservation of Nummulites tests in shallow-water limestones regarding the Middle Eocene Climate Optimum (Dinaric foreland basin, Croatia)
Authors: Ćosović Vlasta , Aljinović Dunja , Bucković Damir , Čančar Marina , Felja Igor , Galovic Ines , Horvat Marija , Kurtanjek Dražen , Pejnović Igor , Pezelj Đurđica , Tomašić Nenad , Coric Stjepan
Published: March 2022

The Eocene sediments along the eastern Adriatic coast, deposited in the Dinaric foreland basin, are characterized by an abundance of larger benthic foraminifera (LBF). Representatives of the Nummulites are abundant in limestones deposited in oligotrophic, euphotic to mesophotic carbonate ramp settings and in deep basin sediments (being redeposited in mass - transport deposits). Nummulite-rich Lutetian to Bartonian sediments occur in the northwestern part of the basin and Bartonian to Priabonian in the SE part. For this study, nummulite tests from 60 thin sections of shallow-water limestones collected in the northern and southern parts of the foreland basin were examined in detail. The foraminiferal tests from the different areas show signs of mechanical, biological, or chemical degradation, which varies greatly depending on the area. The study of Lutetian carbonates from Istria and Northern Adriatic region has shown that 2 to 5% of all Nummulites tests show boring marks. The A– and B– generation representatives were equally affected by bioerosion. The traces are small and randomly distributed holes near to the outer walls. The Nummulites tests of Bartonian – Priabonian (Hvar Is., Pelješac) are more frequently bioeroded, about 10% of all specimens show boring marks, and preferably B-generation specimens are destroyed. Destruction varies from multiple holes of the same size distributed in a line along the test diameter to complete destruction of the internal test structure. There is a kind of size selection of the bioeroders, because the boring marks in the B-generation tests are larger, than those in the A-generation tests. The more intense bioturbation suggests greater biological competition in the middle to outer ramp settings around the Middle Eocene Climate Optimum in this part of the Neotethys. There are several possible causes for this: (i) a slightly higher seawater temperature around the MECO led to a higher occurrence of bioeroders (even the appearance of some new forms, such as the recorded crabs from the eastern Neotethys, Schweitzer et al., 2007), or (ii) a difference in sedimentation rate (burial history) between the two areas, or (iii) the Lutetian LBF assemblages were more resistant to biological destruction?

Schweitzer, C.E., Shirk, A.M., Ćosović, V., Okan, Y., Feldmann, R.M. and Hosgor; I.: New species of Harpactocarcinus from the Tethys Eocene and their paleoecological settings, Journal of Paleontology, 81/5, 1091-1100, 2007.

This study is conducted within the framework of the scientific project IP-2019-04-5775 BREEMECO, funded by the Croatian Scientific Foundation.
Mediterranean heat injection to the North Atlantic delayed the intensification of Northern Hemisphere glaciations
Authors: Bahr André , Kaboth-Bahr Stefanie , Stepanek Christian , Amorim Catunda Maria Carolina , Karas Cyrus , Ziegler Martin , García-Gallardo Ángela , Grunert Patrick
Published: March 2022

The intensification of the Northern Hemisphere glaciations at the end of the Pliocene epoch represents one of the most substantial climatic shifts during Cenozoic. Paradoxically, sea surface temperatures in the high latitude North Atlantic Ocean increased between 2.9–2.7 Ma, against a background of global cooling and declining atmospheric pCO2. To investigate the origin of this high latitude warming, we obtained sedimentary geochemical proxy data from the Gulf of Cadiz to reconstruct the variability of Mediterranean Outflow Water, an important heat source to the North Atlantic. In fact, we find evidence for enhanced production of Mediterranean Outflow Water during the mid-Pliocene to late Pliocene. We argue that the injection of this warm water on intermediate levels drove a sub-surface heat channel into the high-latitude North Atlantic where it warmed the sea surface. We further used Earth System Models to numerically constrain the impact of enhanced Mediterranean Outflow Water production on the northward heat transport within the North Atlantic. In accord with the proxy evidence, the numerical model results show the formation of a sub-surface channel that funneled heat from the subtropics into the high latitude North Atlantic. We further suggest that warming of the North Atlantic realm by this mechanism might have substantially delayed ice sheet growth at the end of the Pliocene.
Assessment of the impacts on data assimilation performance caused by spatio-temporal gaps in satellite soil moisture data
Authors: Mohammed Khaled , Leconte Robert , Trudel Mélanie
Published: March 2022

Previous studies have shown that assimilating satellite soil moisture data in land surface models can improve the estimations of soil moisture. One of the limitations of these satellite soil moisture products is that there are often spatial gaps (in the horizontal direction) in data availability over certain areas due to issues such as dense vegetation or hilly terrain. These products are also limited in the vertical direction because, for the microwave-based products for example, the microwave radiation captured by the satellite sensors to estimate soil moisture is usually representative of a very thin top layer of soil (up to about 5 cm). Lastly, data over a specific watershed may not be available every day (i.e. temporal gaps) because of the orbital configuration of the satellite in question. From the existing literature, it is not clear what the benefits will be for soil moisture modeling, if these spatio-temporal gaps in satellite soil moisture datasets could somehow be minimized or eliminated. To answer this question, a synthetic assimilation study was carried out on the Noah-MP land surface model within the WRF-Hydro modeling system. The study was conducted with ERA5 forcing data on the Susquehanna River Basin and the Ensemble Kalman Filter was the chosen assimilation algorithm. Multiple scenarios were explored in which spatio-temporal gaps were introduced in the synthetic observations by mimicking the actual spatio-temporal gaps that are present in the SMAP soil moisture product. Results indicate that the model’s ability to accurately simulate soil moisture is much lower when assimilated observations have spatio-temporal gaps, compared to model simulations where there are no gaps in the assimilated observations. However, it was found that this lower model accuracy can be improved if the model grids with missing observations are updated based on the covariance between the soil moisture of those grids and their surrounding grids.
Adiabatic and diabatic signatures of ocean temperature variability
Authors: Holmes Ryan , Sohail Taimoor , Zika Jan
Published: March 2022

Anthropogenically induced radiative imbalances in the climate system lead to a slow accumulation of heat in the ocean. This warming is often obscured by natural modes of climate variability such as the El Nino-Southern Oscillation (ENSO), which drive substantial ocean temperature changes as a function of depth and latitude. The use of watermass coordinates has been proposed to help isolate forced signals and filter out fast adiabatic processes associated with modes of variability. However, how much natural modes of variability project into these different coordinate systems has not been quantified. Here we apply a rigorous framework to quantify ocean temperature variability using both a quasi-Lagrangian watermass-based temperature coordinate and Eulerian depth and latitude coordinates in a free-running climate model under pre-industrial conditions. The temperature-based coordinate effectively filters out the adiabatic component of ENSO-dominated interannual variability, while a substantial diabatic signal remains. At slower (decadal to centennial) frequencies, variability in the temperature- and depth-based coordinates is comparable. Spectral analysis of temperature tendencies reveals the dominance of advective processes in latitude- and depth-coordinates while the variability in temperature-coordinates is related closely to the surface forcing. Diabatic mixing processes play an important role at slower frequencies where quasi steady-state balances emerge between forcing and mixing in temperature, advection and mixing in depth and forcing and advection in latitude. Our work suggests that watermass based analyses accurately filter out adiabitic variability and highlight diabatic effects, but also that natural variability has a strong diabatic component and can not be ignored in the analysis of long term trends.
Investigations of Particle Accelerations by Turbulent Magnetic Reconnection in Large-Scale CME/Flare Current Sheet: I. Protons and Electrons 
Authors: Zhu Bojing , Li Yan , Lin Jun
Published: March 2022

Turbulence, the self-generated turbulence by plasmas and magnetic field collective interaction, has been found to play an essential role in energizing charged particles in the large-scale reconnecting current sheet in the major solar eruption.

The typical large-scale CME/Flare events involve sudden bursts of particle acceleration from the sudden release of magnetic energy in a few minutes to a few tens of minutes. The X-rays emission and gamma rays burst produced by the combined result from the interactions of electrons, hydrogen, helium, and other heavier ions. Space and laboratory researchers are more inclined to believe that turbulence acceleration is belonged to shock acceleration. Solar and astrophysics researchers are more inclined to believe that turbulence acceleration is an independent acceleration mechanism that belongs to the flare acceleration. The evidence in both theories and observations from solar atmosphere activities shows that the acceleration is related to nonlinear resonant wave-particle interaction (e.g., Landau acceleration). So far, many-particle acceleration models consider turbulence acceleration as an effective way of generating energetic electrons, protons, and heavier ions. However, the detailed role of turbulence in this process remains unclear. More effort needs to invest in looking into particle accelerations by turbulence that occurs over a large range of the scale in space from the inertial scale of individual particles to the MHD scale.

In this work, applying the statistical treatment of plasma physics, combing with filter theory of turbulence, the actual ratio of the proton mass to the electron mass, and mass-to-charge ratios, we investigate the interaction of charged particles with the turbulent electric field and magnetic field in the large-scale CME/flare current sheet by applying the

We found the significant Langmuir turbulence acceleration (LTA) through the nonlinear resonant wave-particle interaction in the diffusion region via tracking the trajectories and analyzing the energy spectrum of energetic protons and electrons. The results show that protons and electrons could be efficiently accelerated simultaneously and that the way of LTA is similar to that of the shock acceleration}} but is much more efficient than the shock acceleration. This indicates that large-scale reconnection is a good candidate for the mechanism for the efficient acceleration of protons and electrons in the major solar eruption.

The acceleration of heavy ion considered Helium (3He/4He) and other heavy elements in 3He-rich flares burst would explore in the follow-up work series.

URL: https://pan.cstcloud.cn/s/drEdcjIaT8E
Spontaneous formation and evolution of a weak hydrous layer at a slab interface: a numerical perspective 
Authors: Lee Changyeol , Kim YoungHee
Published: March 2022

The cold forearc mantle is a universal feature in global subduction zones and attributed to mechanically decoupling by the weak hydrous layer at the sub-forearc slab interface. Understanding the mechanical decoupling by the weak hydrous layer thus provides critical insight into the transition from subduction infancy to mature subduction since subduction initiation. Nevertheless, the formation and evolution of the weak hydrous layer by slab-derived fluids and its role during the transition have not been quantitatively evaluated by previous numerical models as it has been technically challenging to implement the mechanical decoupling at the slab interface without imposing ad hoc weakening mechanism. We here for the first time numerically demonstrate the formation and evolution down-dip growth of the weak hydrous layer without any ad hoc condition using the case of Southwest Japan subduction zone, the only natural laboratory on Earth where both the geological and geophysical features pertained to the transition since subduction initiation at ~17 Ma have been reported. Our model calculations show that mechanical decoupling by the spontaneous down-dip growth of the weak hydrous layer converts hot forearc mantle to cold mantle, explaining the pulsating forearc high-magnesium andesite (HMA) volcanism, scattered monogenetic forearc and arc volcanism, and Quaternary adakite volcanism. Furthermore, the weak hydrous layer providing a pathway for free-water transport toward the tip of the mantle wedge elucidates seismological observations such as large S-wave delay time and nonvolcanic seismic tremors as well as slab/mantle-originating geochemistry in the Southwest Japan forearc mantle.

 
Bounce Resonance Scattering of Radiation Belt Energetic Electrons by Extremely Low-Frequency Chorus Waves
Authors: Guo Deyu , Xiang Zheng , Ni Binbin , Cao Xing , Fu Song , Zhou Ruoxian , Gu Xudong , Yi Juan , Guo Yingjie , Jiao Luhuai
Published: March 2022

Bounce-resonant diffusion coefficients of radiation belt energetic electrons induced by extremely low-frequency (ELF) chorus waves are comprehensively evaluated using Van Allen Probes observations on 22 December 2014. ELF chorus waves can efficiently scatter 85° < eq < 89° electrons with bounce resonance pitch angle scattering rates above 10-4/s and energy scattering rates above 10-7/s. By comparing diffusion coefficients due to bounce resonance with those due to cyclotron and Landau resonances, we found that bounce resonance diffusion rates have slight energy dependence for >100 keV electrons while Landau-resonant scattering rates decrease significantly in the MeV energy range. These findings suggest that bounce resonances by ELF chorus waves have potentially significant contributions to the dynamics of energetic electrons and should be considered in the further modeling of Earth’s radiation belts.
Clumped isotope analyses on biogenic aragonites and their use in paleoclimate reconstructions
Authors: de Winter Niels J. , Witbaard Rob , Kocken Ilja , Müller Inigo A. , Ziegler Martin
Published: March 2022

Understanding the response of Earth’s climate to perturbations requires accurate and detailed reconstructions of past climate states (e.g. Tierney et al., 2020). The clumped isotope thermometer has the potential to constrain the formation temperatures of carbonates independent from the (isotopic) composition of the precipitation fluid and regardless of the origin (e.g. taxonomy) of the carbonate producer (e.g. Anderson et al., 2020), making it an ideal tool for paleoclimate reconstructions. Unfortunately, it is still not fully certain whether the clumped isotope composition of different carbonate minerals (e.g. calcite, aragonite, dolomite) responds similarly to changes in formation temperatures or variations in the temperature at which the acid reaction takes place during analyses (e.g. Guo et al., 2009; Müller et al., 2017). This uncertainty complicates the application of clumped isotope thermometry to biogenic aragonite shells of bivalves and gastropods, as well as to chemically precipitated travertines and speleothems.

To solve part of these issues, we present a new dataset consisting of clumped isotope measurements on aragonitic Arctica islandica bivalves grown at precisely controlled temperatures (1.1±0.2°C - 18±0.3°C). We compare our data with preexisting clumped isotope calibration datasets spanning a wide temperature range and containing both aragonite and calcite samples. Our clumped isotope data with well-defined formation temperatures allows us to constrain small but important differences between previously published calibration datasets and sheds light on the temperature dependence of clumped isotope composition of aragonites. We use these new insights into the clumped isotope thermometer at low temperatures to produce seasonally resolved paleotemperature reconstructions from excellently preserved aragonitic bivalves from the Pliocene Warm Period, a valuable analogue for future climate under intermediate greenhouse gas emission scenarios (SSP2-4.5; Meinshausen et al., 2020).

References

Anderson et al. GRL 48, e2020GL092069, https://doi.org/10.1029/2020GL092069, 2021.

Guo et al. GCA, 73, 7203–7225, https://doi.org/10.1016/j.gca.2009.05.071, 2009.

Meinshausen et al. GMD 13, 3571–3605, https://doi.org/10.5194/gmd-13-3571-2020, 2020.

Müller et al. Chem. Geol., 449, 1–14, https://doi.org/10.1016/j.chemgeo.2016.11.030, 2017.

Tierney et al. Science 370, https://doi.org/10.1126/science.aay3701, 2020.
Distribution law and development trend forecast of geological hazards in Qilian Mountain
Authors: Zeng Cheng , Hu Sheng
Published: March 2022

Geological hazards occur frequently in Qilian Mountain, causing economic losses and casualties, therefore, this scientific expedition mainly investigates the geological hazards in the Qilian Mountain where the distribution of hazards is uneven, mainly concentrating in the southeast. Due to the inaccuracy of remote sensing interpretation of hazard sites, it is necessary to combine field investigations to calibrate hazard distribution and development trend forecast. Through on-site survey and investigation of each hazard sites, field survey forms and hazard plane sketches should be finished on site. Through unmanned air vehicle survey and on-site sampling, the specific situation of the hazard sites can be acquired, and we can summarize the hazard data to obtain the distribution of hazard sites. We studied the damage forms and characteristics of engineering structures within the influence range of typical disaster chains, and analyzed the combined damage characteristics of different disaster chains and different engineering structures. We researched the possible development trends of potential disaster chains, and predicted their impact and damage on engineering structures. On-site investigation of hazard sites is of great significance in exploring the key links of disaster chain control and proposing monitoring measures for engineering hazard prevention and mitigation.
Resonance widening effect for electron scattering by electromagnetic ion cyclotron waves
Authors: Tonoian David , Artemyev Anton , Shevelev Mark
Published: March 2022

Resonant electron interaction with electromagnetic coherent waves in inhomogeneous magnetic fields is traditionally described by quasi-linear theory. The basic element of such a description are the diffusion coefficients evaluated for resonant energies and pitch-angles. High amplitude waves, however, may resonate with electrons nonlinearly, and such nonlinear resonance interaction would wider the energy and pitch-angle range of electrons scattered by waves. This study is devoted to investigation of the effect of a finite resonance width in energy/pitch-angle space for electrons interacting with electromagnetic ion cyclotron waves. We evaluate the resonance width for a realistic wave amplitudes and background magnetic field inhomogeneity, and then generalize the diffusion coefficients by including the resonance widening. Comparison of original and generalized diffusion rates reveals the wave parameters’ range and energy/pitch-angle range where the finite resonance width effect may be important for electron scattering.
Causal attribution of low AMOC strengths to anthropogenic influence
Authors: Alastrué de Asenjo Eduardo , Barkhordarian Armineh , Brune Sebastian , Baehr Johanna
Published: March 2022

The Atlantic Meridional Overturning Circulation (AMOC) is a crucial feature of Earth’s climate, and the possible recent AMOC weakening in association with anthropogenic emissions is a topic of current scientific discussion. To assess whether anthropogenic emissions affect the circulation, we examine low AMOC strengths with the framework of the causal counterfactual theory.  

We compare the occurrence of low strengths in a factual world with all forcings present against a counterfactual world, equivalent except for anthropogenic forcings. To represent these two worlds, we use past and future 30-member ensembles of simulations from the Max Planck Institute Earth System Model (MPI-ESM1.2-LR), whose AMOC characteristics at 26.5°N are in overall agreement with observations from the RAPID program.

Considering the whole historical period (1850-2020), our results show that causation probabilities for anthropogenic forcings on low AMOC strengths at 26.5 °N are generally low. However, within future projections, we find that anthropogenic forcings will very likely be a necessary cause of any AMOC strength below 16.0 Sv by about 2040. These results are sensitive to the choice of attribution window: if the starting year is chosen closer to the present, all probabilities substantially increase. Within the analyzed simulations, the main attribution results found at 26.5°N are confirmed for other latitudes in the North Atlantic.
Attenuation-compensated reverse-time migration of waterborne GPR based on attenuation coefficient estimation
Authors: Shen Ruiqing , Zhao Yonghui , Cheng Hui , Ge Shuangcheng
Published: March 2022

To the waterborne ground-penetrating radar detection, reverse-time migration (RTM) method can image the structure of the bottom of the water and locate the buried bodies. However, the image quality is limited by the attenuation of electromagnetic waves. How to compensate the attenuation becomes a critical problem. Some RTM methods related to the attenuation-compensated have been developed in recent years. We use the attenuation-compensated RTM based on the minus conductivity. However, the method is limited by the estimation of the attenuation coefficient. Here, we propose an attenuation-coefficient estimation method based on the centroid frequency downshift method (CFDS). In EM attenuation tomography, the centroid frequency downshift method works for attenuation estimation. Compared with the CFDS method in tomography, our proposal is based on the centroid frequency of the bottom-interface of water instead of the source wavelet. Thus, we can avoid the problem of the unknown source wavelet. The method is based on two assumptions: 1) GPR data can be regarded as zero-offset records. 2) Reflections from underwater interfaces are independent of frequency. In addition, the formula about the attenuation coefficient shows when the ratio between the conductivity and the product of the dielectric constant and the angular frequency is greater than one, the attenuation coefficient tends to be a constant. This does not meet the assumption that the attenuation coefficient is linearly related to frequency. We will select a proper frequency range to meet the linear relation by the spectral ratio method. Because the ratio of the signal spectrum of the bottom interface to the spectrum of the underwater interface is consistent with the change of the attenuation coefficient with frequency. Then, the CFDS method will acquire a linear attenuation coefficient with the frequency. Finally, we choose half of the central frequency to acquire the estimated attenuation coefficient. We design a layered waterborne GPR detection model, the conductivity of the silt layer varies between 0.1 and 0.01. The error of the conductivity estimation is below 10%. After acquiring the attenuation coefficient, the attenuation-compensated RTM works correctly and effectively.
Probabilistic power ramp forecasts using multivariate Gaussian regression
Authors: Muschinski Thomas , Lang Moritz N. , Mayr Georg J. , Messner Jakob W. , Simon Thorsten , Zeileis Achim
Published: March 2022

Efficient wind farm operation requires reliable probabilistic forecasts of power ramps. These are sudden fluctuations in power production which, if unanticipated, can lead to significant imbalances in the electrical grid.  The power produced by a turbine strongly depends on the wind speed at hub-height, making it is useful to base these forecasts on calibrated wind speed scenarios generated by statistically postprocessing numerical weather predictions (NWPs). Since the probability of a ramp event depends jointly on the wind speed distributions forecasted at multiple future times, postprocessing methods must not only calibrate the marginal forecasts for each lead time, but also estimate temporal dependencies among their errors.

We use new multivariate Gaussian regression (MGR) models to postprocess all next-day hourly 100m wind speeds near offshore wind farms in one step. The postprocessed forecast is a multivariate Gaussian distribution with mean vector μ — containing the 24 forecasted hourly mean wind speeds — and Σ — the 24 × 24 covariance matrix containing uncertainties of the individual forecasts as well as their temporal error correlations.  Joint distributions are estimated conditionally by flexibly linking the components of μ and parameters specifying Σ to predictors derived from an ECMWF ensemble using generalized additive models for each distributional parameter.

The joint distribution — predicted uniquely for each ECMWF initialization — can simulate postprocessed wind speed ensembles with any number of members. Subsequently, the forecasted ensembles are transformed into power space using an idealized turbine power curve and probabilities computed for different ramp events. Ramp forecasts from MGR outperform those obtained using reference methods which postprocess wind speed forecasts in two-steps: (i) first calibrating the marginal distributions with nonhomogeneous Gaussian regression before (ii) constructing temporal error dependencies using either the order statistics of the NWP ensemble (ensemble copula coupling, ECC) or those of raw observations (Schaake Shuffle).
A synthetic representative tidal signal for long-term morphological modelling
Authors: Schrijvershof Reinier , van Maren Bas , Hoitink Ton
Published: March 2022

Current tidal input reduction approaches applied for accelerated morphological simulations aim at capturing the dominant tidal forces in a single or double representative tidal cycle, often referred to as a "morphological tide''. The existing methods may provide appropriate boundary conditions to simulate representative residual transport fluxes and the resulting morphological changes of the tidal channels. However, heavily simplified tidal signals fail to represent the tidal extremes. They poorly represent intertidal areas, which exert a major impact on the development of tidal asymmetry and the associated residual transport fluxes.

Here, we aim to develop a generic method to construct a synthetic representative tidal signal that incorporates tidal extremes. Such a synthetic cycle should adhere to several criteria to make it applicable for long-term (i.e. subdecadal) accelerated simulations. The synthetic signal should: (1) represent the original signal, particularly preserving asymmetries present in the original signal; (2) be exactly periodic, to ensure coherency between consecutive cycles and to control the relative phasing with other types of forcings (e.g. wind, waves, discharge); and (3) remain valid during the long-term simulations in which the bathymetry in the modelling domain changes shape.

The starting point for the construction of the synthetic signal is a fortnightly modulation of the semi-diurnal tide to represent spring-neap variations, while conserving periodicity. Diurnal tides and higher harmonics of the semi-diurnal tide are included to represent the asymmetry of the tide. The amplitudes are then scaled to give a best fit to the full tidal signal. Statistical measures of the synthetic signal show that it gives a better representation of the amplitude variation and asymmetries present in the original signal, compared to existing approaches of tidal input reduction. A hydrodynamically validated depth-averaged model of the Ems estuary (The Netherlands) demonstrates the effects of different tidal input reduction techniques on residual sediment transport patterns. Adopting the new approach, the shape of the tidal wave is better represented over the entire length of the estuary, and inundation of shallow parts of the basin is modelled in closer resemblance to the real-world intertidal dynamics.
On the magnetosphere-ionosphere coupling during the May 2021 Geomagnetic storm.
Authors: Diego Piero , Piersanti Mirko , Del Moro Dario , Parmentier Alexandra , Martucci Matteo , Palma Farnacesco , Sotgiu Alessandro , Plainaki Christina , D'Angelo Giulia , Berrilli Francesco , Recchiuti Dario , Papini Emanuele , Napoletano Gianluca , Cicone Antonio , Iuppa Roberto , Sparvoli Roberta , Ubertini Pietro , Battiston Roberto , Picozza Piergiorgio
Published: March 2022

On May 12,  2021 the interplanetary counterpart of the May 9,  2021 coronal mass ejection impacted the Earth’s magnetosphere, giving rise to a strong geomagnetic storm.  This work discusses the evolution of the various events linking the solar activity to the Earth’s ionosphere with special focus on the effects observed in the circumterrestrial environment. We investigate the propagation of the interplanetary coronal mass ejection and its interaction with the magnetosphere - ionosphere system in terms of both magnetospheric current systems and particle redistribution, by jointly analysing data from interplanetary, magnetospheric, and low Earth orbiting satellites. The principal magnetospheric current system activated during the different phases of the geomagnetic storm is correctly identified through the  direct  comparison  between  geosynchronous  orbit  observations  and  model  predictions. From the particle point of view, we have found that the primary impact of the storm development is a net and rapid loss of relativistic electrons from the entire outer radiation belt. Our analysis shows no evidence for any short-term recovery to pre-storm levels during the days following the main phase.  Storm effects also included a small Forbush decrease driven by the interplay between the interplanetary shock and subsequent magnetic cloud arrival.
The impact of urban areas on various meteorological variables: The “urban meteorology island”
Authors: Karlický Jan , Huszár Peter , Belda Michal , Halenka Tomáš
Published: March 2022

The urban heat island (UHI) is well-known phenomenon, however, also other meteorological field are significantly affected by urban environment. The WRF and RegCM regional climate models with various setting were used to determine overall weather and climate alteration due to urban surfaces. Simulations were run on 9 km domain covering the center of Europe and time area of years 2015 and 2016. Validation of results was performed by E-OBS, ECAD and MODIS data. The urban effects were studied for 10 chosen big cities across domain, nearly all studied variables manifest statistically significant differences in urban areas. Cloud cover is increased in cities mainly in summer afternoons, together with sub-grid-scale precipitation. Specific humidity is decreased during day-time in summer and also in winter. In view of differences between models, the urban effects are more pronounced in WRF than in RegCM model. Finally, as a generalization of UHI and similar phenomena defined already, we can define urban meteorology island (UMI) as a single phenomenon covering all specific features as UHI as components of UMI.
Thermohaline structure and dynamic parameters of mesoscale eddies of South Kuril region
Authors: Lebedeva Maria , Tatiana Belonenko
Published: March 2022

The South Kuril region belongs to the Northwestern part of the Pacific Ocean and is characterized by a complex system of interactions between two large currents: the Kuroshio, which carries warmer waters from the southwest, and the Oyashio, which carries colder waters from the northeast. As a result of the currents’ interaction, the frontal zones arise; they are characterized by active vortex formation. The cyclonic and anticyclonic eddies may occur due to the separation of meanders from the Kuroshio current or can be formed in the process of collision of eddies already existing in this system. Dynamic parameters and thermohaline structure of eddies affect the fishing of saury and squid in the area of the southern Kuril Islands.

In this work, dynamic parameters and thermohaline structure of certain eddies based on data from daily reanalysis GLORYS12V1 are analyzed. The GLORYS12V1 product is the CMEMS global ocean eddy-resolving reanalysis. It covers the altimetry from 1993 to 2019, has a horizontal resolution of 1/12° and 50 vertical levels. It is based on the current real-time global forecasting CMEMS system. The model component is the NEMO driven at the surface by ECMWF ERA-Interim. Observations are assimilated using a reduced-order Kalman filter. Along track altimeter data (Sea Level Anomaly), Satellite Sea Surface Temperature, Sea Ice Concentration and In situ Temperature and Salinity vertical Profiles are jointly assimilated. In this work, the data «GLOBAL_REANALYSIS_PHY_001_030» available at https://resources.marine.copernicus.eu/product-detail/GLOBAL_MULTIYEAR_PHY_001_030 is used.

This work aims to study the dynamic parameters and thermohaline structure of several eddies formed in the South Kuril region. We detect and monitor the eddies and investigate hydrological conditions in them favorable for fishing.
EasyGeoModels: a New Tool to Investigate Seismic and Volcanic Deformations Retrieved through Geodetic Data. Software Implementation and Examples on the Campi Flegrei Caldera and the 2016 Amatrice Earthquake 
Authors: Solaro Giuseppe , Buonanno Sabatino , Castaldo Raffaele , De Luca Claudio , Fusco Adele , Manzo Mariarosaria , Pepe Susi , Tizzani Pietro , Valerio Emanuela , Zeni Giovanni , Atzori Simone , Lanari Riccardo
Published: March 2022

The increasingly widespread use of space geodesy has resulted in numerous, high-quality surface deformation data sets. DInSAR, for instance, is a well-established satellite technique for investigating tectonically active and volcanic areas characterized by a wide spatial extent of the inherent deformation. These geodetic data can provide important constraints on the involved fault geometry and on its slip distribution as well as on the type and position of an active magmatic source. For this reason, over last years, many researchers have developed robust and semiautomatic methods for inverting suitable models to infer the source type and geometry characteristics from the retrieved surface deformations.

In this work we will present a new software we have implemented, named easyGeoModels, that can be used by geophysicists but also by less skilled users who are interested in sources modeling to determine ground deformation in both seismo-tectonic and volcanic contexts. This software is characterized by some innovative aspects compared to existing similar tools, such as (i) the presence of an easy-to-use graphic interface that allows the user, even if not particularly expert, to manage the data to be inverted, the input parameters of one or more sources, the choice of the deformation source (s), effective and simple way; (ii) the possibility of selecting the GPS data to be inverted, simply by selecting the area of interest: in this case the software will automatically consider for the inversion only the GPS stations present in the selected area and will download the relative data from the Nevada Geodetic Laboratory site; (iii) the generation of output files in Geotiff, KMZ and Shapefile format, which allow a faster and more immediate visualization through GIS tools or Google Earth.

Finally, as applications, we will show some preliminary results obtained through the easyGeoModels software on areas characterized by huge deformation both in a volcanic context, such as that of the Campi Flegrei caldera, and a seismo-tectonic one, as for the case of the Amatrice earthquake (central Italy) which occurred on 24 August 2016.
Sheath characteristics of interplanetary coronal mass ejections derived from Helios and PSP data
Authors: Temmer Manuela , Bothmer Volker
Published: March 2022

Helios 1 and 2 data, covering the distance range from 0.3-1au, have been analysed to derive the characteristics of various substructures of interplanetary coronal mass ejections (ICMEs). We have investigated a data sample of 40 events observed by the Helios 1/2 spacecraft during the time period 1974-1981 with respect to the characteristics of different ICME features, such as sheath regions, leading edges and the magnetic ejecta (ME) themselves. For comparison and to investigate events at distances even closer to the Sun, we add a sample of 5 ICMEs observed with Parker Solar Probe during 2018-2021. We study the sheath density variations over distance and relate those to the ambient solar wind speed. The results show that the sheath region is moderately anti-correlated with the solar wind speed ahead of the disturbance. We further find that the sheath density becomes dominant over the ME density beyond about 0.2au and that its spatial extent constantly increases with distance. The results are important for better understanding the CME mass evolution due to sheath enlargements. Based on these analyses we derive an empirical relation between the sheath density and the local solar wind plasma speed upstream of the ICME shock. The empirical results can be used to model the sheath structure and help improve our understanding about CME propagation in the inner heliosphere.