bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of current sheets and plasmoids within corotating/stream interaction regions
Authors: Sagitov Timofey , Kislov Roman
Published: March 2020

High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth’s orbit.

Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and  (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids. 

We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.
Improving the forecast skill of El Nino diversity: A nonlinear forcing singular vector approach
Authors: Tao Lingjiang , Duan Wansuo , Vannitsem Stephane
Published: March 2020

Observations indicate that there exist two types of El Niño events: one is the EP-El Niño with a warming center in the eastern tropical Pacific, and the other is the CP-El Niño with large positive SST anomalies in the central tropical Pacific. Most current numerical models show low skills in identifying the El Niño diversity. The present study examines the dynamical properties of the ENSO forecast system NFSV-ICM which combines an intermediate complexity ENSO model (ICM) with a nonlinear forcing singular vector (NFSV)-tendency perturbation forecast model. This system is able to distinguish different types of El Niño in simulations and predictions. It is shown that the NFSV-ICM system is able to capture the horizontal distribution of the SST anomalies and their amplitudes in the mature phase of not only EP-El Niño but also CP-El Niño. At the same time, the NFSV-ICM is able to describe the evolution of SST anomalies associated with the two types of El Niño up to at least two-season lead time, while the corresponding forecasts with the ICM is only limited to at most one-season lead time. These improvements are associated with the modifications of atmospheric and ocean processes described by the ICM through the NFSV-tendency perturbations. In particular, the thermocline and zonal advection feedback are strongly modified and improve the conditions of emergence of both the EP- and CP-El Niño events. The NFSV-ICM therefore provides a useful platform for studying ENSO dynamics and predictability associated with El Niño diversities.
Contemporary Urban Expansion in China and its diverse effects
Authors: Zhao Shuqing
Published: March 2020

The scale of urbanization in China during the past 30 years is unprecedented in human history along with its fast economic growth, presenting profound impacts on socioeconomics, human well-being, and the environment. We quantified spatial patterns and temporal courses of urban land expansion for 32 major cities across China from the late 1970s to 2010 using multitemporal Landsat data of 1978, 1990, 1995, 2000, 2005, and 2010, and further explored the effects of urbanization on climate (i.e., urban heat islands), and vegetation phenology and growth in these 32 cities, together with MODIS Land Surface Temperature (LST) and Enhanced Vegetation Index (EVI) products.

We found that rapid urban expansion was observed in these 32 major cities from 1978 to 2010, with an overall annual expansion rate of 6.8 ± 2.5 %. Chinese urban expansion does not fit urban expansion theory consistently over time and has transitioned from contradicting to conforming to Gibrat’s law, which states that the growth rate is independent of city size. The surface urban heat island intensity (SUHII) differed substantially between day and night and varied greatly with season. Spatial variability of the SUHII is ultimately controlled by background climate. The growing season started 11.9 days earlier and ended 5.4 days later in urban zones compared to rural counterparts. The phenological sensitivity to temperature were 9-11 days SOS advance and 6-10 days EOS delay per 1 °C increase of LST. For the first time, we developed a general conceptual framework for quantifying the impacts of urbanization on vegetation growth and applied it in 32 Chinese cities. Results indicated prevalent vegetation growth enhancement in urban environment and vegetation growth was enhanced at 85% of the places along the intensity gradient. This growth enhancement offset about 40% of direct loss of vegetation productivity caused by replacing productive vegetated surfaces with non-productive impervious surfaces. The urban environments, considered as the "harbingers" of global environmental change and "natural laboratories" for global change studies, shed new insights and approaches into global change science, and the urban-rural gradient provides an excellent experimental manipulations for global change studies.
Distinct particle properties between ultrafine and accumulation modes under clean and polluted urban environments
Authors: Wang Yuying , Li Zhanqing , Zhang Renyi , Jin Xiaoai , Wang Qiuyan
Published: March 2020

In this study, we report a phenomenon of fast changing in aerosol hygroscopicity between clean and pollution periods observed frequently in urban Beijing during winter using a hygroscopicity tandem mobility analyzer (H-TDMA). The cause of this phenomenon and the formation process of particles in different modes are discussed. During clean periods, ultrafine mode particles (Nucleation and Aitken modes) mainly stem from nucleation events with subsequent growth. During heavy pollution periods, they originate chiefly from primary emissions. Coarser-mode particles like accumulation mode particles are mainly from primary emission during clean periods and aqueous reactions during pollution periods. This finding based on H-TDMA measurement can make up the deficiency of mass-dependent instruments in analyzing sources and chemical processes of ultrafine mode particles.
The Unusual Intensity Pattern of OH(6,2) and O(1S) Airglow Observed Over the Andes Lidar Observatory
Authors: Huang Tai-Yin , Amaro-Rivera Yolián , Vargas Fabio , Urbina Julio
Published: March 2020

Simultaneous observations of OH(6,2) and O(1S) nightglow at the Andes Lidar Observatory (ALO) from September 2011 to April 2018 have been analyzed to investigate an unusual intensity pattern showing an O(1S) nightglow intensity enhancement concurrent with an OH(6,2) nightglow intensity weakening. About 142 nights have been identified in the time period showing a remarkable biannual occurrence rate with maxima during the equinoxes. A semidiurnal (12-h) tide fitting applied to the 30-min bin size monthly averaged data shows that the largest amplitudes of the semidiurnal tide were observed for the months of April and August-October in the OH(6,2) data and April and September in the O(1S) data. It was also found that SABER’s atomic oxygen at the O(1S) peak height is 1.3-2.5 times higher during the nights that displayed the unusual intensity pattern. Simulations using the nonlinear, time-dependent, OH Chemistry Dynamics (OHCD) and Multiple Airglow Chemistry Dynamics (MACD) models have also been used to investigate the effect of a long-period wave on the OH(6,2) and O(1S) airglow intensities. The simulation results are in good agreement with the observations and replicate the unusual intensity pattern observed in the OH(6,2) and O(1S) airglow data.
Rapid fluid-driven transformation of lower continental crust associated with thrust-induced shear heating
Authors: Jamtveit Bjørn , Dunkel Kristina G. , Petley-Ragan Arianne , Corfu Fernando , Schmid Dani W.
Published: March 2020

Caledonian eclogite- and amphibolite-facies metamorphism of initially dry Proterozoic granulites in the Lindås Nappe of the Bergen Arcs, Western Norway, is driven by fluid infiltration along faults and shear zones. The granulites are also cut by numerous dykes and pegmatites that are spatially associated with metamorphosed host rocks. U-Pb geochronology was performed to constrain the age of fluid infiltration and metamorphism. The ages obtained demonstrate that eclogite- and amphibolite-facies metamorphism were synchronous within the uncertainties of our results and occurred within a maximum time interval of 5 Myr, with a mean age of ca. 426 Ma.  Caledonian dykes and pegmatites are granitic rocks characterised by a high Na/K-ration, low REE-abundance and positive anomalies of Eu, Ba, Pb, and Sr. The most REE-poor compositions show HREE-enrichment. Melt compositions are consistent with wet melting of plagioclase- and garnet-bearing source rocks. The most likely fluid source is dehydration of Paleozoic metapelites, located immediately below the Lindås part of the Jotun-Lindås microcontinent, during eastward thrusting over the extended margin of Baltica. Melt compositions and thermal modelling suggest that short-lived fluid-driven metamorphism of the Lindås Nappe granulites was related to shear heating at lithostatic pressures in the range 1.0-1.5 GPa. High-P (≈2 GPa) metamorphism within the Nappe was related to weakening-induced pressure perturbations, not to deep burial. Our results emphasize that both prograde and retrograde metamorphism may proceed rapidly during regional metamorphism and that their time-scales may be coupled through local production and consumption of fluids.
Modelling runoff generation of a small catchment in the context of climate change by using an ensemble of different climate model outputs and bias correction methods
Authors: Sonntag Kai , Gassmann Matthias
Published: March 2020

Due to climate change, meteorological extremes affect the environment and our society in the past decades. But not only the extremes are piling up, the average temperatures and the precipitation regimes have changed in recent decades. The change in meteorological conditions also affects the water balance and thus also the generation processes of runoff. The aim of this work is to estimate this future change for a small low-mountain catchment in central Germany using climate projections and hydrological modelling.

As input to the hydrological model HBV Light, climate data from seven different combinations of global and regional climate models are used. However, due to their substantial bias it is necessary to apply bias correction. For each of the three climate input time series used by HBV Light, different bias correction methods are tested: Precipitation (Linear Scaling Multiplication, Quantile Mapping, Power Transformation, Distribution Mapping Gamma), Temperature (Linear Scaling Addition, Quantile Mapping, Variance Scaling, Distribution Mapping Normal) and Potential Evapotranspiration (Linear Scaling Multiplication, Linear Scaling Addition, Quantile Mapping). The corrected climate model outputs are compared to the observed timeseries and rated based on three different efficiency criteria. Overall, the combination of different climate models and bias correction methods generates 63 future hydrological projections. Based on this ensemble, the future water balance of the catchment is assessed. The results show that (1) the biggest uncertainties in the hydrological simulation were generated by uncorrected climate model outputs; (2) the uncertainties in hydrological simulations increase till the end of the century; (3) Power Transformation and Quantile Mapping perform best for precipitation, Linear Scaling Addition and Quantile Mapping for temperature, Linear Scaling Addition and Quantile Mapping for potential evapotranspiration; (4) the total annual outflow increases till 2070 because of an increase of the outflow in winter and spring; (5) in the future, interflow will increase in spring and winter and reduce in summer and autumn; (6) till the end of the century the baseflow will rise in spring and in the rest of year the baseflow will decrease. This study shows that even if changes in the annual total discharge for small catchments have no significant trend, the generation processes and the seasonal values may change in the future.
Changes of groundwater recharge at different global warming levels: A global-scale multi-model ensemble approach
Authors: Reinecke Robert , Müller Schmied Hannes , Döll Petra
Published: March 2020

Billions of people rely on groundwater that is an accessible source for drinking water and irrigation especially in times of drought. This importance will likely increase with a changing climate. It is still unclear, however, to what extent climate change will globally impact groundwater systems and thus the availability of this important resource. Groundwater recharge is a central indicator for groundwater availability but projections vary. In this talk we will present global-scale results of a multi-model ensemble approach incorporating eight global hydrological models and four global circulation models to show the impact of global warming (GW) on global groundwater recharge. Preindustrial and current (at 1 °C GW) groundwater recharge is compared with recharge for different GW levels as a result of different representative concentration pathways (RCPs). Results suggest that the uncertainty range is large and predictions with confidence can be only made for specific regions worldwide. Furthermore, because most hydrological models do not include CO2 driven vegetation processes we investigate how including the effect of changing CO2 into the calculation of future groundwater recharge impacts the results. In some regions, inclusion of these processes leads to differences in groundwater recharge changes of up to 100 mm/yr in case of 3 °C GW.
Full paleostress tensor determination: case of the Panasqueira Mine, Portugal.
Authors: Pascal Christophe , Jaques Luís , Yamaji Atsushi
Published: March 2020

The quantification of tectonic forces or, alternatively, stresses represents a significant step towards the understanding of the natural processes governing plate tectonics and deformation at all scales. However, paleostress reconstructions based on the observation and measurement of natural fractures are traditionally limited to the determination of four out of the six parameters of the stress tensor. In the present study, we attempt to reconstruct full paleostress tensors by extending the methodologies advanced by previous authors. We selected Panasqueira Mine, Central Portugal, as natural laboratory, and focused on the measurement of sub-horizontal quartz veins, which are favorably exposed in three dimensions in the underground galleries of the mine. Inversion of the vein data allowed for quantifying the respective orientations of the stress axes and the shape ratio of the stress ellipsoid. In order to reconstruct an additional stress parameter, namely pressure, we extensively sampled vein material and combined fluid inclusion analyses on quartz samples with geothermometric analyses on sulphide minerals. Finally, we adjusted the radius of the obtained Mohr circle with the help of rupture laws, and obtained the six parameters of the paleostress tensor that prevailed during vein formation. Our results suggests a NW-SE reverse stress regime with a shape ratio equal to ~0.6, lithostatic pore pressures of ~300 MPa and differential stress lower than ~20 MPa.
Soil copper contamination effect on carbon mineralisation: evidence of a soil CO2 emission decrease from literature review
Authors: Laura Sereni , Bertrand Guenet , Olivier Crouzet , Isabelle Lamy
Published: March 2020

Among all pollutants, copper (Cu) is of major environmental and toxicological concern with contamination from various origins. Moreover as a cation, Cu is easily complexed by the negatively charged soil organic matter (OM) inducing high concentrations in upper layers of soils where OM dominates. Due to its biotic and abiotic interactions with soil constituents Cu is expected to affect several soil processes among them the soil respiration, but studies provided contrasting results as soil respiration have been shown to decrease or increase with soil contamination depending on the studies.

In this study, we aimed at assessing how soil respiration is affected by Cu contamination in order to quantifying as a first approach the GHG emissions for a contaminated soil. We performed a quantitative review of literature focusing on soil heterotrophic respiration (thus excluding autotrophic respiration from plants) which aimed at 1) assessing the impact of a copper contamination on soil carbon (C) mineralisation and thus CO2 emissions, and 2) hierarchizing the determinants of such an impact on C mineralisation compare to the influence of pedo-climatic soil parameters such as pH, clay percentage or the type of climate.

On the basis of a selection of roughly 390 literature data, global main results showed a decrease in soil CO2 emission with an increase in soil Cu contamination. Data from ex situ spiking experiments could be easily differentiated from the ones originated from in situ natural contamination due to their sharper decrease in soil organic carbon mineralisation. Interestingly, ex situ spikes data on the short term provided a threshold: an increase in soil CO2 emissions was noticed for data below total soil Cu content of 180 mg kg-1 while a decrease was observed above this concentration. On the contrary, long-term in situ contamination due to anthropogenic activities (urbanisation, agriculture …) did not significantly impact soil carbon mineralisation except when we focused on the high inputs of industrial contamination (smelter, composted plant…). Soil pH was found as a variable of interest as acidic soils were more sensitive to Cu contamination for C mineralisation than neutral or alkaline soils, while the % of clay and the type of climate did not add explanation to the variation in C mineralisation. These results are discussed and the collected data allowed us to propose a general equation quantifying how soil respiration can be affected by a Cu contamination.
Rupture speed of supershear slip instabilities
Authors: Kammer David , Svetlizky Ilya , Fineberg Jay
Published: March 2020

Shear ruptures propagating along natural faults or simulated faults in analog laboratory experiments present a wide range of rupture velocities. Most ruptures propagate at velocities below the Rayleigh wave speed and Linear Elastic Fracture Mechanics (LEFM) theory has been shown to predict quantitatively well the observed propagation speed. However, early theoretical and numerical work suggested that ruptures may surpass the shear wave speed and propagate at velocities that can reach the longitudinal wave speed. This was later confirmed in laboratory experiments and observed as supershear earthquakes in nature. While the transition from sub-Rayleigh to supershear propagation has been studied extensively, current knowledge of propagation speed in the supershear regime is limited to a couple of idealistic set-ups. Here, we analyse the propagation speed of supershear ruptures along various nonuniform interfaces using simulations and experiments. We show that an approximate fracture mechanics theory describes well supershear rupture speeds as observed in our experiments and simulations. Furthermore, the theory uncovers a critical rupture length below which supershear propagation is impossible. Beyond this critical length, a rupture can sustain supershear propagation for arbitrarily low prestress levels if local non-uniformities cause transition. The presented theory provides a tool to better understand the potential for supershear ruptures in more realistic heterogeneous systems.
GRACE-like gridded reconstructions of total water storage change from SLR and statistical techniques
Authors: Kusche Juergen , Löcher Anno , Fupeng Li , Rietbroek Roelof
Published: March 2020

The total water storage change (TWSC) data record from the GRACE mission has found numerous applications in hydrology, oceanography, cryosphere, solid Earth and sea level research, and climate sciences. However, GRACE was only launched in 2002 and it lasted until 2017 with an increasing number of missing data, while GRACE-FO continued in May 2018. There will be no TWSC data within a gap of at least 11 months, and no GRACE-like data exists prior to 2002. As a result the current data record is not sufficiently long to for validating climate model predictions even for the long-term mean of TWSC, let alone for the probability of extreme events.

In this contribution we will discuss ways to reconstruct terrestrial TWSC from either geodetic or hydrometeorological data, or possibly from a combination. We will present new reconstructions of TWSC from 1992 onwards from satellite laser ranging (SLR) and from statistical learning methods, discuss various approaches, and compare to conventional SLR solutions, the Humphrey (2019) statistical reconstruction, and to GRACE in the more recent time frame. We show that both geodetic SLR analysis and/or multilinear regression or machine learning approaches can be successfully applied in a regularized framework where spatial modes from a GRACE-era TWSC decomposition inform the reconstructions. We show that these reconstructions reproduce many phenomena seen in modelling studies beyond the seasonal cycle; e.g. the suspected gradual onset of Greenland mass loss around 1998-2000, increase ocean mass rate since about 2011, or the presence of ENSO events.
Synergistic Probe-Orbiter Science and Measurements for Understanding the Formation and Evolution of the Icy Giant Planets
Authors: Atreya Sushil K. , Mousis Olivier , Reh Kim R.
Published: March 2020

The Galileo Probe was designed to measure the abundances of the heavy elements (mass >helium) and helium in Jupiter since they are key to understanding the planet’s formation and heat balance. Broadly speaking, the same formation scenarios presumably apply also to the Icy Giant Planets (IGP), Uranus and Neptune, so the determination of their heavy elements and He is equally important. We will show that the bulk of C, N, S, and O are sequestered in condensible volatiles whose well-mixed regions in the atmospheres of the IGP’s are extremely deep compared to Jupiter. That poses formidable challenges to their direct in situ measurements. On the other hand, being non-condensible and chemically inert, the noble gases − He, Ne, Ar, Kr and Xe – are expected to be uniformly mixed all over the planet, unlike the condensibles whose distribution is governed by dynamics, convection and purported deep oceans. Thus the noble gases would provide the most critical set of data for constraining the IGP formation models. Although the noble gases should be well-mixed everywhere below the homopause, measurements at and below the 1-bar level are needed considering their low mixing ratios, except for He. That depth also gets around any potential cold trapping of the heavy noble gases at the tropopause or adsorption on methane ice aerosols. Entry probes deployed to relatively shallow pressure levels of 5-10 bars would allow a robust determination of the abundances and isotopic ratios of the noble gases, amongst other things. A measurement of CO from orbit, along with other disequilibrium species has the potential of estimating the O/H ratio. Microwave radiometry from orbiter and the Earth have the potential of measuring the depth profiles of NH3 and H2O, which would be important for understanding the atmospheric dynamics and weather in the deep atmosphere. Combined with the above data and the data on the interior and the magnetic field, the probe results on the noble gases would provide essential constraints to the formation, migration and evolution models of the Icy Giant Planets. 
Study on Deformation and Force Characteristics of Deep-buried Large Section Expansive Red Clay Tunnel
Authors: Xie Zhuowu , Wu Xiyong
Published: March 2020

Due to the large burial depth of the Pliocene Red Layer in Qingyang, Gansu and its special historical causes, its engineering mechanical characteristics are quite different from those of the southern red clay. Lack of systematic data on the internal forces of the lining structure through the stratum tunnel. Therefore, this paper takes the Yinchuan-Xian High-speed Railway Qingyang Tunnel as the research object, through field measurement and finite element simulation to obtain the space-time distribution characteristics of the internal force of the lining structure, the surrounding rock pressure, the deep displacement of the surrounding rock from 5 to 10 m, and the convergent deformation of the support. The reasons for the stress state of the lining-surrounding rock composite structure reflected in the results are analyzed, and the ABAQUS software is used to simulate the tunnel excavation process to compare and verify the lining structure stressing law. Internal force characteristics. The results show that: 1) The physical and mechanical indicators of the Pliocene red layer in the Neogene in Qingyang, Gansu belong to the extremely hard soil-very soft rock critical category. Due to the long consolidation pressure and long consolidation history, it can be obvious on the saturated flooding fault surface. Observation of the characteristics of layered joints proves that this layer of red clay has a tendency of sedimentary diagenesis. 2) The quality of the surrounding rock of the stratum lining structure is good. The horizontal in-situ stress is twice that of the vertical in-situ stress. It can be optimized for the design of III-IV surrounding rock while increasing the side pressure coefficient. 3) The unclosed initial support cannot effectively limit the deformation of the surrounding rock, and the temporary stress can be used to improve the state of stress. The numerical simulation results are consistent with the field measurement laws. 4) This stratum with severe deformation is the cave diameter range of the excavation boundary to the surrounding rock. The deformation area is mainly concentrated in the vault. Delayed excavation of the inverted arch can effectively reduce the stress on the internal lining structure of the inverted arch.
Extension discrepancy distribution of the hyper-thinned continental crust in the Baiyun Rift, northern margin of the South China Sea
Authors: Zhao Yanghui , Ding Weiwei , Ren Jianye , Li Jiabiao , Tong Dianjun , Zhang Jiangyang
Published: March 2020

It has been widely reported that extension of the upper crust measured from faulting is far less than the lower crustal thinning at rifted continental margins. This phenomenon is referred to as “extension discrepancy”. However, recent studies found out not all rifted margins had experienced a crustal thinning increasing with depth. Here, we use observations from 3D seismic reflection data that cover the Baiyun Rift, to explore the extension discrepancy between the brittle extension and crustal thinning when the crust of the Northern South China Sea margin thinned from 30km to <12km. To achieve this, first, we restored the rift system of the Baiyun Rift in the absence of post-rift sediments and water loading. Subsequently, we applied alternative methods based on the fault geometries and the crustal thickness ratios to compare the deformation of the brittle crust and the whole crust. Results show (1) the upper crustal faulting was sufficient to explain the whole crust thinning in the basin center, indicating no extension discrepancy; (2) near the rift flanks, the upper crustal faulting is greater than the whole crustal thinning, indicating inverse discrepancy. In the northeast of the Baiyun Rift where detachment faulting occurred, magmas passively upwelled and thickened the crust due to isostasy. Consequently, the lower crust was exhumed locally during the detachment faulting. These results indicate the hyper-thinning process of the continental crust in the Northern South China Sea was substantially dominated by tectonic extension rather than thermal thinning.
Impact of Surface Waves on Wind Stress under Low to Moderate Wind Conditions
Authors: Chen Sheng , Qiao Fangli , Jiang Wenzheng , Guo Jingsong , Dai Dejun
Published: March 2020

The impact of ocean surface waves on wind stress at the air–sea interface under low to moderate wind
conditions was systematically investigated based on a simple constant flux model and flux measurements
obtained from two coastal towers in the East China Sea and South China Sea. It is first revealed that the
swell-induced perturbations can reach a height of nearly 30m above the mean sea surface, and these perturbations
disturb the overlying airflow under low wind and strong swell conditions. The wind profiles severely
depart from the classical logarithmic profiles, and the deviations increase with the peak wave phase speeds. At
wind speeds of less than 4 m/s, an upward momentumtransfer from the wave to the atmosphere is predicted,
which is consistent with previous studies. A comparison between the observations and model indicates that
the wind stress calculated by the model is largely consistent with the observational wind stress when considering
the effects of surface waves, which provides a solution for accurately calculating wind stress in ocean
and climate models. Furthermore, the surface waves at the air–sea interface invalidate the traditional
Monin–Obukhov similarity theory (MOST), and this invalidity decreases as observational height increases.
The Lagrangian ice microphysics code LCM: Introduction, current developments and benefits
Authors: Unterstrasser Simon
Published: March 2020

The Lagrangian Cirrus Module (LCM) is a Lagrangian (also known as particle-based) ice microphysics code that is fully coupled to the large-eddy simulation (LES) code EULAG. The ice phase is described by a large number of simulation particles (order 106 to109) which act as surrogates for the real ice crystals. The simulation particles (SIPs) are advected and microphysical processes like deposition/sublimation and sedimentation are solved for each individual SIP. More specifically, LCM treats ice nucleation, crystal growth, sedimentation, aggregation, latent heat release, radiative impact on crystal growth, and turbulent dispersion. The aerosol module comprises an explicit representation of size-resolved non-equilibrium aerosol microphysical processes for supercooled solution droplets and insoluble ice nuclei.

First, an general introduction to particle-based microphysics coupled to a grid-based (Eulerian) LES model is given.
In the following, emphasis is put on highlighting the benefits of the Lagrangian approach by presenting a variety of simulation examples.
The Alteration of Reservoir-Cap’s System During CO2 Charging in Huangqiao Region, China
Authors: Zhou Bing , Lun Zengmin
Published: March 2020

Revealing the alteration mechanism of reservoir-cap rock system during CO2-rich fluid charging is meaningful to the study of CO2 geological storage, as well as when CO2 enhance oil recovery. The study is taking the Permian Longtan reservoir formation and Dalong cap layer of Huangqiao and Jurong region in Lower Yangtze area in China as comparative study objects, in order to understand the differences between presence and absence of CO2 in the similar geological background. The samples of reservoirs and cap rock in both regions are analysized through petrological and geochemistry method. The authigenic minerals in the reservoirs of Huangqiao region are mainly overgrowth quartz and kaolinite. A small amount of dawsonite is developed in Huangqiao, while undeveloped in Jurong region due to the absent of CO2. The content of secondary quartz is lower in Jurong than in Huangqiao. The reservoir’s average porosity in Huangqiao is obviously higher than in Jurong, because of the feldspar’s dissolution during CO2 charging. The cap rocks in the two areas are both black block mudstones. There were micro-cracks developed in the cap rocks of Huangqiao region, in which have been refilled with calcite veins. Carbon isotope data shows that calcite was formed from CO2-water-rock interaction. The result indicates that CO2 charging could cause a major dissolution of feldspar in reservoir, and precipitate a typical authigenic mineral assemblage of dawsonite, secondary quartz and kaolinite. The continuous activity of the CO2-rich fluid leads to re-precipitation of carbonate minerals in cap rock, which is improving its sealing ability.
Experimental study of dispersion and modulational instability of surface gravity waves on constant vorticity currents
Authors: van den Bremer Ton , Steer James , Stagonas Dimitris , Buldakov Eugeny , Borthwick Alistair
Published: March 2020

We examine experimentally the dispersion and stability of weakly nonlinear waves on opposing linearly vertically sheared current profiles (with constant vorticity). Measurements are compared against predictions from the unidirectional  1D+1 constant vorticity nonlinear Schrödinger equation (the vor-NLSE) derived by Thomas et al. (Phys. Fluids, vol. 24, no. 12, 2012, 127102). The shear rate is negative in opposing currents when the magnitude of the current in the laboratory reference frame is negative (i.e. opposing the direction of wave propagation) and reduces with depth, as is most commonly encountered in nature. Compared to a uniform current with the same surface velocity, negative shear has the effect of increasing wavelength and enhancing stability. In experiments with a regular low-steepness wave, the dispersion relationship between wavelength and frequency is examined on five opposing current profiles with shear rates from 0 to -0,87 s-1 For all current profiles, the linear constant vorticity dispersion relation predicts the wavenumber to within the 95% confidence bounds associated with estimates of shear rate and surface current velocity. The effect of shear on modulational instability was determined by the spectral evolution of a carrier wave seeded with spectral sidebands on opposing current profiles with shear rates between 0 and -0.48 s-1. Numerical solutions of the vor-NLSE are consistently found to predict sideband growth to within two standard deviations across repeated experiments, performing considerably better than its uniform-current NLSE counterpart. Similarly, the amplification of experimental wave envelopes is predicted well by numerical solutions of the vor-NLSE, and significantly over-predicted by the uniform-current NLSE.
Upper-Ocean Circulation Anomalies of the Western Equatorial Pacific Observed in 2016 Summer
Authors: Lyu Yilong
Published: March 2020

Mooring measurements at ~140°E in the western equatorial Pacific documented greatly intensified eastward subsurface currents, which largely represents the nascent Equatorial Undercurrent (EUC), to ~67 cm s-1 in boreal summer of 2016. The eastward currents occupied the entire upper 500 m, with the westward surface currents nearly diminished. Similar variations were also observed during previous El Niño events, as suggested by historical in-situ data. Further analysis combining satellite and reanalysis data reveals that the eastward currents observed at ~140°E are a component of an anomalous counterclockwise circulation straddling the equator, with westward current anomalies retroflecting near the western boundary and feeding southeastward current anomalies along New Guinea coast. A 1.5-layer reduced-gravity ocean (RGO) model is able to crudely reproduce these variations, and a hierarchy of sensitivity experiments are performed to understand the underlying dynamics. The observed circulation anomalies are largely the delayed ocean response to the strong equatorial wind anomalies over the central-to-eastern Pacific basin emerging in the mature stage of El Niño (September-April). Downwelling equatorial Rossby waves are generated by the reflection of equatorial Kelvin waves and easterly wind anomalies in the eastern Pacific. Upon reaching western Pacific, the Southern Hemisphere lobe of Rossby waves encounter the slanted New Guinea island and deflects equatorward, establishing a local sea surface height maximum near the equator and leading to the detour of westward currents flowing from the Pacific interior. Additional experiments with edited western boundary geometry confirm the importance of topography in regulating the structure of this cross-equatorial anomalous circulation.
Upper Carboniferous-Permian tectonics in Central Mediterranean: an updated revision
Authors: Molli Giancarlo , Brogi Andrea , Caggianelli Alfredo , Capezzuoli Enrico , Liotta Domenico , Spina Amalia , Zibra Ivan
Published: March 2020

An updated revision of the upper Carboniferous-Permian tectonics recorded in Corsica, Calabria and Tuscany is here proposed. We combine our and literature data to document how the sedimentary, tectono-metamorphic and magmatic upper Carboniferous-Permian record fits with a regional-scale tectonic scenario characterized by trascurrent fault systems associated with stretched crustal domains in which extensional regional structures, magmatism and transtensional basins developed. In Corsica, altogether with well-known effusive and intrusive Permian magmatism, the alpine S.Lucia nappe exposes a kilometer-scale portion of the Permian lower to mid-crust, with many similarities to the Ivrea-Verbano zone. The two distinct Mafic and Leucogranitic complexes, which characterize this crustal domain are juxtposed by an oblique-slip shear zone named as S.Lucia Shear Zone. Structural and petrological data document interaction between magmatism, metamorphism and shearing during Permian in the c. 800-400 °C temperature range. In Calabria (Sila, Serre and Aspromonte), a continuous pre-Mesozoic crustal section is exposed. The lower crust portion of such section is mainly made up of granulites and migmatitic paragneisses with subordinate marbles and metabasites. The mid-crustal section includes an up to 13 km thick sequence of granitoids of tonalitic to granitic composition, emplaced between 306 and 295 Ma and progressively deformed during retrograde extensional shearing to end with a final magmatic activity between 295 and 277 Ma, consisting in the injection of shallower dykes in a transtensional regime. The section is completed by an upper crustal portion mainly formed by a Paleozoic succession deformed as a low-grade fold and thrust belt, locally overlaying medium-grade paragneiss units, and therefore as a whole reminiscent of the external/nappe zone domains of Sardinia Hercynian orogen. In Tuscany we document, how late Carboniferous/Permian shallow marine to continental sedimentary basins characterized by unconformity and abrupt change in sedimentary facies (coal-measures, red fanglomerate deposits) and acid magmatism well fit a transtensional setting with a mid-crustal shear zone linked with a system of E-W trending (in present orientation) upper crust splay faults. We will frame the whole dataset in a regional framework of first-order transcurrent shear zones network which includes a westernmost S.Lucia Shear Zone and an easternmost East Tuscan Shear Zone, with intervening crustal domains in which extensional to transtensional shearing occured.
Enhanced storm activities triggered the North Pacific deep convection during the Younger Dryas event
Authors: lin Xiaopei , Zhang Cunjie
Published: March 2020

The occurrence of deep convection could redistribute ocean heat and materials, and induce robust climate and biogeochemical changes. The convection in the North Pacific is quite shallow now (typically 300-m), but paleo records and model simulations suggest that it might reach 2000-3000 m during stadials in the last deglaciation, such as the Heinrich event 1 (H1: ~17.5-15 ka) and Younger Dryas event (YD: ~12.8-11.5 ka). The deep convection during H1 has been explained by increased North Pacific surface salinity due to evaporation and precipitation changes, but this explanation conflicts with many paleo records for YD. Here we collected published paleo records in the northwest Pacific and carried out simulations for the YD period. We show that due to the weakened Atlantic Meridional Overturning Circulation (MOC) during YD, the oceanic Meridional Heat Transport (MHT) weakened. According to the Bjerknes compensation, the atmospheric MHT strengthened. Because atmospheric MHT mainly occurs through baroclinic eddies in extratropics, storm activities strengthened. The strengthened wintertime storm activities induced more oceanic turbulent heat loss and triggered deep convections in the North Pacific, and further contributed to a seesaw pattern of MOC strengths between the North Pacific and North Atlantic. Our result not only provides a new explanation for the North Pacific deep convection during YD but also suggest that synoptic-scale atmospheric variations are capable of influencing low-frequency paleoclimate changes.
Indian Monsoon Rainfall Amount Forecast: Network-based Approach and Climate Change Benefits
Authors: Fan Jingfang , Meng Jun , Ludescher Josef , Li Zhaoyuan , Surovyatkina Elena , Chen Xiaosong , Kurths Juergen , Schellnhuber Hans Joachim
Published: March 2020

The Indian summer monsoon rainfall (ISMR) has decisive influence on India's agricultural output and economy. Extreme departures from the normal seasonal amount of rainfall can cause severe droughts or floods, affecting Indian food production and security.  Despite the development of sophisticated statistical and dynamical climate models, a long-term and reliable prediction of ISMR has remained a challenging problem.  Towards achieving this goal, here we construct a series of dynamical and physical climate networks based on the global near surface air temperature field. We uncover that some characteristics of the directed and weighted climate networks can serve as good early warning signals for ISMR forecasting. The developed prediction method can produce a forecast skill of 0.5, by using the previous calendar year's data (5-month lead-time). The skill of our ISMR forecast is comparable to the best statistical and dynamical forecast models, which start in May or June. We reveal that global warming  affects climate network, by enchanting cross-equatorial teleconnections between Southwest Atlantic and North Asia-Pacific, which significantly impacts on  global precipitation. Remarkably, the consequences of climate change lead to improving the prediction skills. We discuss the underlying mechanism of our predictor and associate it with network--delayed--ENSO and ENSO--monsoon connections. Moreover, we find out that this approach is not limited to prediction of all India rainfall but also can be applied to forecast the Indian homogeneous regions rainfall. Our network-based approach developed in the present work provides a new perspective on the regional forecasting of the ISMR, and can potentially be used as a prototype for other monsoon systems.

 
Complexity-based approach for El Niño magnitude forecasting before the spring predictability barrier
Authors: Meng Jun , Fan Jingfang , Ludescher Josef , Agarwala Ankit , Chen Xiaosong , Bunde Armin , Kurths Juergen , Schellnhuber Hans Joachim
Published: March 2020

The El Niño Southern Oscillation (ENSO) is one of the most prominent interannual climate phenomena. An early and reliable ENSO forecasting remains a crucial goal, due to its serious implications for economy, society, and ecosystem. Despite the development of various dynamical and statistical prediction models in the recent decades, the “spring predictability barrier” (SPB) remains a great challenge for long (over 6-month) lead-time forecasting. To overcome this barrier, here we develop an analysis tool, the System Sample Entropy (SysSampEn), to measure the complexity (disorder) of the system composed of temperature anomaly time series in the Niño 3.4 region. When applying this tool to several near surface air temperature and sea surface temperature datasets, we find that in all datasets a strong positive correlation exists between the magnitude of El Niño and the previous calendar year’s SysSampEn (complexity). We show that this correlation allows to forecast the magnitude of an El Niño with a prediction horizon of 1 year and high accuracy (i.e., Root Mean Square Error = 0.23°C for the average of the individual datasets forecasts). For the 2018 El Niño event, our method forecasts a weak El Niño with a magnitude of 1.11±0.23°C.  Our framework presented here not only facilitates a long–term forecasting of the El Niño magnitude but can potentially also be used as a measure for the complexity of other natural or engineering complex systems.
Stable thallium isotope fractionation in soils as affected by pedogenesis
Authors: Vanek Ales , Voegelin Andreas , Mihaljevic Martin , Ettler Vojtech , Trubac Jakub , Drahota Petr , Vankova Maria , Oborna Vendula , Penizek Vit , Pavlu Lenka , Drabek Ondrej , Vokurkova Petra , Zadorova Tereza , Holubik Ondrej
Published: March 2020

In this study, we investigated if variations in the stable Tl isotope ratios in soil samples from different profiles can be linked to data on the extractability and speciation of soil Tl and whether the isotopic data allow drawing conclusions on the geochemical processes linked with soil formation/rock weathering. We observed a significant accumulation of the heavy 205Tl isotope in the B horizons, with ε205Tl values that were up to 7 higher than in the underlying bedrock. This 205Tl enrichment, however, was neither reflected in the speciation of Tl nor its chemical fractionation. Furthermore, exchangeable soil Tl in the B horizons was found to be much isotopically lighter than the bulk soil Tl. Our findings suggest that the observed isotopic shift may be linked to cyclic Tl mobilization and immobilization processes over the period of rock weathering and soil formation. Oxidative Tl uptake by Mn-oxides associated with a 205Tl enrichment, continuous weathering of the Tl(III)-containing phases, followed by a Tl(I) remobilization (leading to enrichment in 205Tl) are suggested to be responsible for the binding of the heavy Tl isotope fraction into other phases, mainly illite (a dominant Tl host), which is not normally expected. We therefore conclude that the use of the Tl isotopic data for phase or sorption mechanism identification in a dynamic multi-phase (soil) system can be very complicated, but, in contrast, suggesting their efficient use as a proxy for redox-controlled processes.