bluuebunny/crossref_metadata_2025 huggingface dataset:
Past the climate optimum: Recruitment is declining at the world’s highest juniper shrublines on the Tibetan Plateau
Authors: Liang Eryuan , Lu Xiaoming , Wang Yafeng , Babst Flurin , Leavitt Steven W. , Camarero J. Julio
Published: March 2020

Alpine biomes are climate change hotspots, and treeline dynamics in particular have received much attention as visible evidence of climate-induced shifts in species distributions. Comparatively little is known, however, about the effects of climate change on alpine shrubline dynamics. Here, we reconstruct decadally resolved shrub recruitment history (age structure) through the combination of field surveys and dendroecology methods at the world’s highest juniper (Juniperus pingii var. wilsonii) shrublines on the south-central Tibetan Plateau. A total of 1,899 shrubs were surveyed at 12 plots located in four regions along an east-to-west declining precipitation gradient. We detected synchronous recruitment with 9 out of 12 plots showing a gradual increase from 1600 to 1900, a peak at 1900–1940, and a subsequent decrease from the 1930s onward. Shrub recruitment was significantly and positively correlated with reconstructed summer temperature from 1600 to 1940, whereas it was negatively associated with temperature in recent decades (1930–2000). Recruitment was also positively correlated with precipitation, except in the 1780–1830 period, when a trend toward wetter climate conditions began. This apparent tipping point in recruitment success coincides with a switch from positive to negative impacts of rising temperatures.  Warming-induced drought limitation has likely reduced the recruitment potential of alpine juniper shrubs in recent decades. Continued warming is thus expected to further alter the dynamics of alpine shrublines on the Tibetan Plateau and elsewhere.
Deterministic versus probabilistic seismic hazard assessment for the Shillong Plateau
Authors: Ismail-Zadeh Alik , Baro Olympa , Kumar Abhishek
Published: March 2020

The Shillong Plateau is an earthquake-prone region in the northeastern India. Based on regional seismotectonic studies, we present the results of seismic hazard assessment, both deterministic (DSHA) and probabilistic (PSHA), and map peak horizontal accelerations (PHA) for three largely populated districts within the Shillong Plateau - the East Khasi hills, the Ri-Bhoi, and the West Garo hills. The hazard analysis methodology is based on the analysis of 72 earthquake sources (active faults) located within 500 km seismotectonic region around the plateau. Using an average sample log-likelihood approach, suitable ground motion prediction equations (GMPEs) are identified. As a variation in hypocentral distances can affect the ranks (or weights) of selected GMPEs, DSHA is performed separately for the three selected districts. DSHA shows that the northern part of the East Khasi hills, eastern part of Ri-Bhoi district and the West Garo hills districts exhibit the highest PHA value. DSHA indicates that the Barapani, Oldham, and Dauki faults influence significantly the seismic hazard of the studied region. In the case of PSHA, the annual frequency of exceedance of ground motions for three populated cities (Shillong city, Nongpoh, and Tura), located within above three districts respectively, are determined. Individual hazard curves indicate that the Barapani fault possesses the highest frequency of seismic hazard for Shillong city and Nongpoh. At Tura, both Eocene hinge zone and Dauki faults are responsible for the highest frequency of seismic hazard. The results of the PSHA are compared with those obtained using the DSHA approach indicating a difference between the two approaches for the West Garo hills district. It is shown that this difference is associated with the Oldham fault located near the district. The fault can produce a great earthquake, although with a lower probability of occurrence compared to a few other faults capable of producing smaller events with higher probability of occurrence. Hence, in the PSHA, the effect of the Oldham fault is less pronounced in terms of the design life of a structure, than in the case of the DSHA.
The energy budget of West Siberian wetland in summer
Authors: Repina Irina , Stepanenko Victor , Artamonov Arseniy
Published: March 2020

This observational study reports variations of surface fluxes (turbulent, radiative, and soil heat) and ancillary atmospheric/surface/soil data based on in-situ measurements conducted at Mukhrino ﬁeld station located in the middle taiga zone of the West Siberian Lowland. We estimated carbon dioxide flux and energy budget in a typical wetland of the western Siberian based on July measurements in 2019. Turbulent ﬂuxes of momentum, sensible and latent heat, and CO2 were measured with the eddy covariance technique. The footprint of measured fluxes consisted of a homogeneous surface with tree-covered and smooth moss-covered surface. Measurements in the atmosphere were supplemented by measurements of heat flux through the soil, net radiation components and soil temperature at several depths. Turbulent heat ﬂuxes (sensible and latent) show a diurnal variation typical of land ecosystems, being in phase with net radiation. Most of the available energy is released as latent heat ﬂux, while maximum sensible heat ﬂuxes are more than 3 times lower. Net CO2 sink was high but was typical for a wetland area. The influence of moss cover on the temperature regime of soil is considered. Based on soil temperature and heat flux measurements the thermal conductivity of moss layer was estimated. The thermal and dynamic roughness lengths of the moss-covered surface in the summer were also studied. The dependence of the dynamic roughness length on the atmospheric stability is established, and the coefficients relating the ratio of thermal and dynamic roughness length to the roughness Reynolds number are determined. The parametrizations obtained in this work can be used in Earth System models to represent wetland surfaces. The work was supported by RFBR grant 18-05-60126.
Environmental changes across the onset of the Messinian salinity crisis: insights from the Piedmont Basin (NW Italy).
Authors: Sabino Mathia , Birgel Daniel , Dela Pierre Francesco , Natalicchio Marcello , Peckmann Jörn
Published: March 2020

Since the discovery of the late Miocene (Messinian) Mediterranean Salt Giant more than 50 years ago, the environmental conditions that caused its formation have been debated. Such reconstruction suffers from the absence of modern analogues, the lack or scarcity of fossils (calcareous plankton and benthos, but also pollens), and the inaccessibility of the evaporites buried beneath the present-day Mediterranean seafloor. We investigate the palaeoenvironmental changes, which drove the formation of the Mediterranean Salt Giant at the onset of the Messinian salinity crisis (MSC) through high resolution sedimentological, petrographical, and geochemical (lipid biomarkers, major and trace elements) analyses of sedimentary successions of the Piedmont Basin (NW Italy). Shale/marl couplets deposited in intermediate to deep-water settings (200 – 1000 m) are targeted, representing the lateral equivalent of primary sulphate evaporites from shallow-water settings that accumulated between 5.97 and 5.60 Ma. We suggest that climate and hydrological changes affected the northern Mediterranean in the earliest stage of the MSC event, leading to an intensification of water column stratification. An upper water layer of marine water influenced by freshwater input was separated through a pycnocline from more evaporated, denser and oxygen-depleted bottom waters. The water column structure and pycnocline oscillation exerted pivotal control over the sedimentary products pertaining to the first stage of the MSC.
A data mining method to identify field type in global oil and gas field case study
Authors: Zhang Qian , Li Dawei , Niu Min , Wu Zhenzhen
Published: March 2020

Based on the locations and types of past oil and gas field, new discoveries can be predicted from the tectonic setting of the world’s oil and gas field. Geoscientists can characterize a field based on the dominant geological event that influenced the structure’s ability to trap and contain oil and gas in recoverable quantities. But in fact multiple factors affected the type of the oil and gas fields. In this paper, a data mining approach was used to integrated factors of field type. The factors are evaluated by the quantified field data. These data included general field data, location, well statistics, cumulative production data, reserves data and reservoir properties data. The method includes four steps. Firstly, a set of attributes are identified to describe the field characteristics. Secondly, the application of principal component analysis and categorical principal components analysis reduced redundant data and noise by representing the main data variances with a few vector components in a transformed coordinate space. Finally, clustering was done based on a proximity matrix between samples. Euclidean distance definitions were tested in order to build a meaningful cluster tree. By applying this method to the world’s oil and gas field data, we concluded that: (1) the world’s fields can be clusfied in six types according to the quantified field data; (2) over 20% of the world’s fields are clustered at top depth between 2000 and 2500 meters. (3)more attributes can be added to this clustering method, and the influence of the attributes can be evaluated.
Trend analysis of extreme climate indices during winter wheat growth period in China
Authors: Nie Hanjiang , Qin Tianling , Lv Zhenyu , Wang Jianwei
Published: March 2020

In this study, the major winter wheat planting area of China is selected as the study area, with the time scale of the growth period of winter wheat (a total of 56 growth periods during 1961/10-2016/5). The significance, stability, magnitude of the trend and the average trend of the study area with 8 temperature indices and 7 precipitation indices of 453 meteorological stations are tested by Mann–Kendall method and Sen's nonparametric method. The following observation can be made: (1) the cold extreme indices show strong and stable downward trend in most of the stations in the study area, while the hot extreme indices show strong and stable upward trend, especially in the northern winter wheat planting area and the north of the southern winter wheat planting area. (2) The trends of extreme precipitation indices in most of the sites in the study area are insignificant and unstable. Only in R20mm, a significant and stable decreasing trend is showed in some stations, which mainly located in the northern winter wheat planting area and part of the central and western regions in study area. The results in some ways could enrich the references for understanding the climate change in the growth period of winter wheat in the region and help to formulate a better agronomic management practice of winter wheat.
Irrigation detection with Sentinel-1 radar backscatter observations over an agricultural area in the Po River Valley (Italy)
Authors: Modanesi Sara , De Lannoy Gabriëlle J. M. , Gruber Alexander , Massari Christian , Brocca Luca , Lievens Hans , Morbidelli Renato
Published: March 2020

Given the projected decrease in water availability due to climate change and anthropogenic processes, the quantification of water usage for agricultural purposes is of critical importance. However, an accurate quantification of irrigation and groundwater extraction remains a major challenge for the current generation of scientists. For instance, the parameterization of irrigation in large scale Land Surface Models (LSM) is improving, but still suffers from simplified assumptions, such as the mostly unknown timing and quantity of irrigation, often for lack of enough ground-based data. Remote sensing observations offer an opportunity to fill this gap in our knowledge, as they will detect irrigation activities. Earlier studies have used satellite soil moisture products obtained from microwave sensors to detect irrigated areas, but only some studies have dealt with the quantification of irrigation using satellite soil moisture data.

The aim of this study is to investigate the ability of high-resolution Sentinel-1 observations to detect changes in soil moisture and vegetation caused by irrigation fluxes. The focus area is the Po river Valley, one of the most important agricultural areas in Northern Italy, where in situ data are available for evaluation at four pilot sites. A comparison of Level-2 Sentinel-1 soil moisture retrievals, in situ data and Noah-MP land surface model (LSM) estimates confirms the presence of irrigation at the pilot sites. However, we hypothesize that even more information on both the irrigated soil moisture and vegetation can be extracted from the Level-1 Sentinel-1 signal via backscatter data assimilation. To prepare for such an assimilation system, Level-1 Sentinel-1 backscatter observations, pre-processed to the 1 km EASE-v2 grid, are further compared to the total backscatter simulated by a Water Cloud Model, using the simulated soil moisture obtained by the Noah-MP LSM as part of the NASA Land Information System (LIS). Noah-MP is here selected for its ability to simulate dynamic vegetation. Our results will show that irrigation can indeed also be detected from the mismatch between simulated and observed backscatter values.
A wind-tunnel study on the sorting effects of wind erosion towards the geochemistry and the particle size of the surface samples from the Horqin sandy land
Authors: Zhang Caixia , Wang Xiaobo
Published: March 2020

Samples from the Horqin sandy land were exposed to a series of wind velocities and the sink particles were collected at the end of the diffusion section of a wind tunnel. The resulting grain size was coarser than the original one, and the original samples showed lower average content of the SiO2 and higher average content of Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O than the collected samples did. Comparing with other dust source area in China, the Horqin sandy land had higher content of the Zr, Ba, SiO2, Al2O3 and K2O. Compared with the average upper continental crust (UCC) composition, surface samples were rich in the content of the Y, Zr, Nb, Ba, La, Nd. Geochemistry characteristics of the fine grain components of the Horqin sandy land differ from those from other dust source regions, because the fine-grained particles in the Horqin sandy land were mostly derived from various local deposits formed in its unique depositional environments controlled by several tectonic activities.
Influence of Lithology, Climate and Topography on the duration of flow intermittence in Burkina Faso.
Authors: Belemtougri Axel , Ducharne Agnès , Karambiri Harouna
Published: March 2020

The precise location of river streams and the characterization of their regime (intermittent or permanent) are critical to the quantification and management of water resources. Intermittent rivers are rivers that cease to flow or go completely dry at various times and places. Some studies estimated that intermittent rivers could account for more than 50% of all rivers in the world and are expected to increase in the future. There has been a growing interest in the understanding of these rivers ecosystems and the possible consequences of this increase in intermittency on the availability of water resources. In Burkina Faso in particular, a country located in West Africa and marked by a strong rainfall gradient between North and South (600 to 1200 mm/y), intermittent streams often represent, in some areas, the only significant freshwater source available for irrigation. It is therefore necessary to develop knowledge and understand the factors controlling intermittency in order to define adequate means to preserve and protect rivers. This study aims to identify non-redundant environmental variables that best explain the geographic variations of the hydrological regime of rivers, and in particular the duration of intermittency, and to discuss their interactions. For this purpose, 40 gauging stations are taken into account in the study. The catchments controlled by these stations cover more than 50% of the country territory. The mean number of dry months was used as a predictor to define several classes of intermittence, for which explicit environmental variables were identified through a Principal Component Analysis (PCA). Results suggest that lithology is a crucial and logical control of intermittency in Burkina, with some stations classified as permanent (43%) mostly located on sedimentary and carbonate rocks, whereas the remaining stations classified as intermittent are mostly located on metamorphic rocks. There is also an increasing trend in the number of dry months depending on the aridity index, although contrasted by the underlying lithology and the catchment area. This approach may subsequently be extended to other African countries in order to consolidate our results.
Flood resilience measurement for communities: data for science and practice
Authors: Szoenyi Michael , Laurien Finn , Keating Adriana
Published: March 2020

Given the increased attention put on strengthening disaster resilience, there is a growing need to invest in its measurement and the overall accountability of resilience strengthening initiatives. There is a major gap in evidence about what actually makes communities more resilient when an event occurs, because there are no empirically validated measures of disaster resilience. Similarly, an effort to identify operational indicators has gained some traction only more recently. The Flood Resilience Measurement for Communities (FRMC) framework and associated, fully operational, integrated tool takes a systems-thinking, holistic approach to serve the dual goals of generating data on the determinants of community flood resilience, and providing decision-support for on-the-ground investment. The FRMC framework measures “sources of resilience” before a flood happens and looks at the post-flood impacts afterwards. It is built around the notion of five types of capital (the 5Cs: human, social, physical, natural, and financial) and the 4Rs of a resilient system (robustness, redundancy, resourcefulness, and rapidity). The sources of resilience are graded based on Zurich’s Risk Engineering Technical Grading Standard. Results are displayed according to the 5Cs and 4Rs, the disaster risk management (DRM) cycle, themes and context level, to give the approach further flexibility and accessibility.

The Zurich Flood Resilience Alliance (ZFRA) has identified the measurement of resilience as a valuable ingredient in building community flood resilience. In the first application phase (2013-2018), we measured flood resilience in 118 communities across nine countries, building on responses at household and community levels. Continuing this endeavor in the second phase (2018 – 2023) will allow us to enrich the understanding of community flood resilience and to extend this unique data set.

We find that at the community level, the FRMC enables users to track community progress on resilience over time in a standardized way. It thus provides vital information for the decision-making process in terms of prioritizing the resilience-building measures most needed by the community. At community and higher decision-making levels, measuring resilience also provides a basis for improving the design of innovative investment programs to strengthen disaster resilience.

By exploring data across multiple communities (facing different flood types and with very different socioeconomic and political contexts), we can generate evidence with respect to which characteristics contribute most to community disaster resilience before an event strikes. This contributes to meeting the challenge of demonstrating that the work we do has the desired impact – that it actually builds resilience. Our findings suggest that stronger interactions between community functions induce co-benefits for community development.
PySDM: Pythonic particle-based cloud microphysics package
Authors: Bartman Piotr , Olesik Michael , Arabas Sylwester , Shima Shin-ichiro
Published: March 2020

In the poster, we will present a new open-source cloud microphysics simulation package PySDM (https://github.com/atmos-cloud-sim-uj/PySDM). The package core is a Pythonic implementation of the Super-Droplet Method (SDM) Monte-Carlo algorithm for representing aerosol/cloud/rain collisional growth.

PySDM design features separation of a backend layer responsible for number-crunching tasks. The developed backend implementations based on Numba, Pythran and ThrustRTC leverage three different Python acceleration techniques dubbed just-in-time, ahead-of-time and runtime compilation, respectively. As a result, PySDM offers high performance with little trade-offs with respect to such advantages of the Python language as succinct and readable source code and portability (seamless interoperability between Windows, OSX and Linux). We will exemplify further advantages that result from embracement of the Jupyter platform which allowed us to equip PySDM with interactive examples and tutorials swiftly executable via web browser through cloud-computing platforms.

Example simulations of the warm-rain process in a kinematic two-dimensional framework mimicking stratoculumus deck will be presented and used as a basis for scalability analysis and discussion of parallelisation nuances of the SDM algorithm.
Soil erosion and sediment transport in South Africa: an overview
Authors: Boardman John , Foster Ian
Published: March 2020

We have few direct measurements of erosion in the country and those that we have are for relatively small areas (badlands) or for experimental plots. We therefore have to rely on sediment yields from rivers and reservoirs, mapping based on remote sensing (gullies) and some modelling. All methods have their disadvantages. With sediment yields the problem of scale is acute and estimates range from <5 to > 11,000 t km-2 yr-1. The great range of estimates partly reflects rainfall/runoff variability but it also strongly reflects the intensity of land use and connectivity or dis-connectivity within catchments.  Elements in the landscape such as gullies (dongas) were initiated under conditions in the past of intense land-use (overstocking) and perhaps climatic pressure. Many gullies are inactive at the present day but have been shown to improve landscape connectivity. However, overgrazed land continues to contribute large quantities of sediment to freshwater systems and to the infilling of reservoirs. The protection of inadequate water resources, threatened by erosion, is a currently urgent problem. More information is needed about the origin of sediments using techniques such as fingerprinting.
Exploring the Affinity and Selectivity of Sedimentary Mackinawite (FeS) Towards Natural Organic Matter
Authors: Tétrault Alexandre , Gélinas Yves
Published: March 2020

if any significant changes occur to the mineral-ligand bonds
Earthquake-induced site effect in the oil field deposit of Absheron peninsula (Azerbaijan)
Authors: Babayev Gulam , Kadirov (Gadirov) Fakhraddin
Published: March 2020

Absheron peninsula (Azerbaijan) area was hit by the strong Caspian earthquakes on November 25, 2000 with Mw6.1 and 6.2 magnitudes. The seismic networks successfully recorded the foreshock, main shock and many aftershocks at respective locations. By using probabilistic analysis, magnitude of design earthquake for the current study in the oilfield was taken as 6.3. From this concept design (scenario) earthquake, accelerations were estimated for the distance of 35 km. In the second phase of the study, soil amplification factors and site characteristics data from boreholes were determined and estimated. In the next phase, the study uses synthesized accelerograms formed on the basis of simulation of the seismic wave propagation processes through ground layer aiming to determine the quantitative characteristics of seismic effect on the oilfield region. Soil amplification values estimated by empirical relationships in terms of shear wave velocities are in the range of 0.7 and 1.9 values. Shear wave velocity (Vs, 30) values are 100 and 110 (m/s). The PGA values for the study area were evaluated by considering the local site effects. Peak ground acceleration varies between 100 – 380 gal. On the basis of the empirical relationship between MSK-64 and peak ground acceleration, the special distribution of intensity of the design earthquake with intensity of >8 is represented. Finally, the study presents possible relationship between seismic effect and daily oil recovery which states the direct proportional characteristics.

Keywords: ground classification, oilfield, scenario earthquake, Vs30, amplification factor, peak ground acceleration
Considerable differences of the interannual variations for the tropical cyclone landfall over north and south East Asia in summer
Authors: Lai Jufen , Li Chaofan , Lu Riyu
Published: March 2020

Interannual variation of tropical cyclone (TC) landfall frequency is not consistent along the coast of East Asia, with large contrast of north and south East Asia coast regions in boreal summer. This study examines interannual variations of TC landfall frequency over north and south East Asia and identifies roles of the western North Pacific subtropical high (WNPSH) and TC genesis frequency associated with these variations. Although the total number of landing TC of north and south East Asia is similar, interannual variations of TC landfall frequency are relatively independent to each other, with the corresponding correlation coefficient north and south of 25°N is only –0.024 from 1979 to 2017. TC landfall over north East Asia is largely modulated by the circulation related to the WNPSH, while TC landfall in the south has no significant relationship with the WNPSH or other remote large-scale circulations. The WNPSH effectively regulates TC landfall in the north by modulating TC genesis east of the Philippines and steering flows. Nonetheless, the two factors have weak contradictory effects on TC landing in the south region. The frequency of TC genesis around the South China Sea directly connects to the TC landfall over south East Asia, which is modulated by the surrounding genesis environment, including relative humidity and relative vorticity. This work favors for a better understanding of the seasonal forecasts of TC landfall frequency and the subsequent climate service over East Asia.
Genesis of ca. 850-835 Ma high-Mg# diorites in the western Yangtze Block, South China: Implications for mantle metasomatism under the subduction process
Authors: Zhu Yu , Lai shaocong
Published: March 2020

High-Mg# (molar 100 × Mg/(Mg + Fe)) diorites can provide significant insights on the mantle metasomatism under the subduction zone. Here we investigate the genesis of Neoproterozoic high-Mg# diorites in the western Yangtze Block to constrain mantle metasomatism during the subduction process. Zircon U-Pb dating results display new weighted mean 206Pb/238U ages of 850.1 ± 1.7 Ma, 840.9 ± 2.4 Ma, and 836.6 ± 1.9 Ma for these high-Mg# diorites. They are metaluminous and calc-alkaline rocks, and characterized by moderate SiO2 (57.08–61.12 wt.%), high MgO (3.36–4.30 wt.%) and Mg# values (56–60). The relatively low initial 87Sr/86Sr ratios (0.703406 to 0.704157), highly positive whole-rock εNd(t) (+3.26 to +4.26) and zircon εHf(t) values (+8.43 to +13.6) imply that they were predominantly sourced from depleted lithospheric mantle. These high-Mg# diorites also show the enrichment of large ion lithophile elements (LILEs, e.g., Rb, Ba, K, and Sr) and depletion of high field strength elements (HFSEs, e.g., Nb, Ta, Zr, and Hf), resembling typical arc magma affinity. The highly variable Rb/Y, Th/Ce, Th/Sm, and Th/Yb ratios indicate the significant incorporation of subduction-related fluids and sediment-derived melts into primary mantle source. We therefore propose that the ca. 850–835 Ma high-Mg# diorites in this study were formed by the partial melting of metasomatized mantle source influenced by subduction fluids and sediment melts. Our new data, in conjunction with numerous studies of metasomatized mantle magmatism from the western Yangtze Block, suggest that Neoproterozoic mantle sources were progressively metasomatized by the subduction-related compositions from slab fluids, sediment melts, to oceanic slab melts during persistent subduction process.
Modular Korteweg - de Vries equation: Riemann, cnoidal and solitary waves
Authors: Pelinovsky Efim , Kokorina Anna , Slunyaev Alexey , Tobisch Elena
Published: March 2020

The review paper by Oleg Rudenko [1] suggests several examples of elastic systems with so-called modular nonlinearities. In this study we consider the modular Korteweg - de Vries (KdV) equation in the form u_t + 6 u u_x + u_{xxx} = 0. This equation is not integrable by means of the Inverse Scattering Transform in the general case, but sign-defined functions which never change the sign satisfy the integrable KdV equation, and hence possess an exact solution. Firstly, we consider the dispersionless limit of the modular KdV equation and analyze the evolution of a simple nonlinear wave (Riemann wave) and its Fourier transform including the asymptotics when the wave tends to break [2]. Then, we study the structure of travelling waves. If the waves propagate on a pedestal and do not cross the zero level u = 0, they coincide with the well-known travelling wave solutions of the classic KdV equation in the form of cnoidal and solitary waves. If the pedestal is zero, the structure of sign-varying travelling waves is expressed through Jacobi elliptic functions. The interaction of solitary waves of different polarities is studied numerically using an implicit pseudo-spectral method. The simulation has revealed the inelastic character of the collision; in the course of the interaction the solitons can alter their amplitudes (the small soliton decreases and the large one grows) and emit small-amplitude waves. The inelastic effects are most pronounced when the solitons’ amplitudes are close. When their amplitudes differ significantly, the maximum wave height which is attained during the absorb-emit interaction tends to the sum of the heights of the solitons with the polarity inherited from the large soliton, as predicted in the frameworks of different long-wave integrable models in [3, 4]. As a result of the collision the solitons may experience non-classic phase shifts as they both jump back.

[1] O.V. Rudenko. Physics – Uspekhi, Vol. 56(7), 683-690 (2013).

[2] E. Tobisch, and E. Pelinovsky. Appl. Math. Lett., Vol. 97, 1-5 (2019).

[3] A.V. Slunyaev, and E.N. Pelinovsky. Phys. Rev. Lett., Vol. 117, 214501 (2016).

[4] A. Slunyaev. Stud. Appl. Math., Vol. 142, 385-413 (2019).
Stability of ambient noise H/V spectra obtained from OBS near the Japan Trench
Authors: Farazi Atikul Haque , Garcia Emmanuel Soliman M. , Ito Yoshihiro
Published: March 2020

Ocean bottom seismometers (OBS) are widely in use since recent past to monitor seismicity of slow earthquakes as well as that of ordinary earthquakes. Seismic velocity structures, especially of S-wave are essential to estimate hypocenters of them with accuracy. Here we focus on spatial and temporal stability of ambient noise horizontal to vertical spectral ratio (H/V) spectra calculated from ocean bottom seismometers, as the first step toward future application of ambient noise H/V to estimate S-wave velocity structure. We aim to use the Nakamura’s method (1989) for ambient noise H/V spectra using a 3-component OBS array in the Japan Trench, to image deep structure above the plate interface near the trench. To achieve the imaging, it is necessary to examine spatial and temporal stability of the derived H/V spectra from these seismometers. First, we split each 24-hours record into 1-hour windows after removing the instrumental response, Then, Fourier amplitude spectra of each component is taken and smoothed using Konno and Ohmachi (1998) method, with applying downsampling, mean and trend removal, and tapering to each window. Finally, a 1-hour H/V spectral ratio is calculated with taking quadratic mean of two horizontal components. However, a total of 21 OBS, 3 broadband and 18 short-period, stations have been used in this study. A daily variation and stability of the H/V spectra are examined along with comparing them spatially from one station to another. Stability of the H/V spectra from OBS is promising for carrying out our future endevour of deeper observation using the ambient noise H/V method.
Preliminary application of machine learning in ensemble forecasting
Authors: Ma Junjie , Duan Wansuo
Published: March 2020

The optimal perturbation method is a beneficial way to generate ensemble members to be used in ensemble forecasting. With orthogonal optimal perturbation, orthogonal conditional nonlinear optimal perturbations (O-CNOPs) generating initial perturbations and orthogonal nonlinear forcing singular vectors (O-NFSVs) generating model perturbations are two kinds of skillful ensemble forecasting methods. There is main disadvantage that O-CNOPs and O-NFSVs generate optimal perturbation members may need a lot of time, but in practical weather prediction, the ensemble members usually need to be generated quickly. In order to benefit from O-CNOPs and O-NFSVs, as well as considering the cost of calculation, therefore, we present a way with the big data and machine learning thinking to simplify the process of the optimal perturbation ensemble methods. Using the historical samples and their optimal perturbations to establish a database, we look for the historical sample which is analogous to what need to be forecasted currently from the database by using the convolutional neural network (CNN). In comparison with using optimization algorithm to get O-CNOPs and O-NFSVs directly, this way gets O-CNOPs and O-NFSVs faster which still obtain acceptable prediction performance. In addition, once the CNN model is trained completely, the cost of time for prediction will be saved. We illustrate the advantage by numerical simulations of a Lorenz 96 model.

Further more, based on above study, some comparison of the ensemble forecasting skill of O-CNOPs and O-NFSVs has been done, and there are three results for the reference: (1) in the early stage (1-6 days), the O-CNOPs method perform more skillfully, and in the later stage (6-12 days), the O-NFSVs method perform more skillfully; (2) within 1-5 days, if the development of analysis error is bigger than or close to the average value of the analysis error development of historical samples, the O-CNOPs method is preferred, else the O-NFSVs method is preferred; (3) within 0-3 days, if the development of energy is bigger than or close to the average value of the energy development of the historical samples, the O-CNOPs method is preferred, else the O-NFVS method is preferred. Next, further work is required to examine and explore more and deeper research using machine learning in ensemble forecasting studies of atmosphere and other systems.
Simulating extreme precipitation over the Arabian Peninsula using a convective-permitting sub-seasonal reforecast product
Authors: Luong Thang M. , Risanto Christoforus Bayu , Chang Hsin-I , Dasari Hari Prasad , Attada Raju , Castro Christopher L. , Hoteit Ibrahim
Published: March 2020

Despite being one of the driest places in the world, the Arabian Peninsula (AP) occasionally experiences extreme precipitation events associated with organized convections. On 25 November 2009, for instance, a cutoff low driven rainfall exceeding 140 mm over a 6-hour period triggered a flash flood event in Jeddah, Saudi Arabia, claiming hundreds of lives and substantially damaging infrastructure. Similar extreme precipitation events have occurred in subsequent years. To assess the potential predictability of extreme precipitation in the Arabian Peninsula, we perform retrospective forecast simulations for several extreme events occurring over the period 2000 to 2018, out to a sub-seasonal timescale (3-4 weeks). Using the Advanced Research version of Weather Research and Forecasting Model (WRF-ARW), we dynamically downscale 11 ensemble members of the European Centre for Medium-Range Weather Forecasts (ECMWF) sub-seasonal reforecasts at convective-permitting resolution (4 km). WRF simulated precipitation is evaluated against various precipitation products, including the Global Precipitation Measurement (GPM) system, Climate Prediction Center morphing technique (CMORPH), and the Saudi Ministry of Water and Electricity(MOWE) and the Presidency of Meteorology and Environment(PME) regional rain gauge measurements. The convective-permitting WRF simulations substantially improve the representation of precipitation relative to the ECMWF reforecast, in terms of spatial distribution and timing. A specific focus in the presentation of the results will be on the potential value added by the use of convective-permitting modeling (CPM) to forecasting extreme events at sub-seasonal timescales. The predictability of the synoptic pattern could be the key for CPM sub-seasonal-type forecast for the AP.
Biophysical climate effects of changing forest cover across scales
Authors: Jia Gensuo
Published: March 2020

Changes of forest cover regulate climate system directly through the alteration of water vapor, energy, and momentum exchange between land surface and the atmosphere. These land-based biophysical effects vary with locations and seasons and cause regional cooling or warming, which enhances or diminishes the climatic benefits of forest carbon drawdown in different cases. Biophysical climate effects of forest conversion exhibit the largest uncertainty in the mid-latitudes. The sign and magnitude of biophysical effect in temperate zones are still under hot debate. Over the past two decades, most of our understandings on how forest affects climate through biophysical processes came from sensitivity analysis of climate modeling, by comparing paired model simulations of forest and short vegetation covers. However, much remains unknown in the real world due to the complicated process and uncertainty in magnitude, especially in the temperate bioclimate regions. Here we reviewed complex results and debates from model simulation, field measurements, and satellite observation, and then applied satellite-based observation to investigate the biophysical climate response to potential forest conversion in temperate regions, especially on the spatial and temporal patterns and underlying mechanisms. We also interpret some key findings on land-climate interactions from recent IPCC special report on climate change and land (SRCCL).

Readings:

Jia, G., E. Shevliakova, P. Artaxo, et al. (2019): Land-climate interactions, in Skea J. et al. (eds.) IPCC Special report on climate change and land. Intergovernmental Panel on Climate Change. IPCC, Geneva (in press) https://www.ipcc.ch/srccl/chapter/chapter-2/

Ma, W., G. Jia, and A. Zhang (2017): Multiple satellite-based analysis reveals complex climate effects of temperate forests and related energy budget,  J. Geophys. Res. Atmos., 122, 3806–3820, doi:10.1002/2016JD026278

Web: green.tea.ac.cn
A sea surface height perspective on El Niño diversity, ocean energetics and energy damping rates
Authors: Shi Jian , Fedorov Alexey , Hu Shineng
Published: March 2020

Ocean energetics is a useful framework for understanding El Niño development and diversity; however, its key element, available potential energy (APE), requires accurate ocean subsurface data that are hard to measure. However, sea surface heights (SSH) provide a useful alternative. In this study, we describe an SSH-based index, SSHI, that accurately captures APE variations and can be easily computed from satellite observations. Using SSHI we obtain an observation-based estimate of the APE damping timescale α-1 of approximately 1.7 years, slightly longer than previous ocean reanalysis-based estimates. We further show that SSHI records the relative strength of the thermocline feedback, serving as an indicator for El Niño “flavors”. SSHI demonstrates a clear decadal shift in El Niño-Southern Oscillation (ENSO) properties that occurred in early 2000s, with a more tilted mean thermocline and weaker thermocline slope variations indicative of the dominance of “Central Pacific” El Niño activity during the past two decades.
Backstripping the Briançonnais (Western Alps) to test Alpine rifting models
Authors: Forzese Martina , Butler Robert W. H. , Stephenson Randell , Maniscalco Rosanna
Published: March 2020

During the Mesozoic, the relative movement of African and Eurasian plates caused the opening of the Tethys Ocean. The rifting phase is well charted by the stratigraphic sequence of Western Alps, which provide an exceptional record of continental margin evolution. The Briançonnais domain occupies a pivotal place for testing various rifting models. This domain contains a remarkably uniform succession of very shallow-water carbonates of Triassic age, capped by Middle-Jurassic shallow-water carbonates or by non-deposition before passing abruptly up into deep-water facies. Here we show that the back-stripped Mesozoic tectonic evolution of the Briançonnais block can be applied to investigate models of lithospheric stretching. Applying the Airy correction, we found that the Triassic is characterised by a constant tectonic subsidence rate of 17 m/Ma. If this is the result of “post-rift” thermal re-equilibration of upper mantle after late Palaeozoic rifting, this rift phase occurred with a stretching factor of c 1.4. That this thermal subsidence was modulated by differential uplift and erosion of the Briançonnais in the early Jurassic implies significant mantle thinning, reducing net density of the Briançonnais lithosphere. The subsidence of more than 3000m during Bathonian-Callovian stages are too rapid to be explained by thermal re-equilibration: it suggests substantial crustal thinning. Our results demonstrate that a uniform stretching model is not able to explain the Jurassic isostatic movement of the Briançonnais domain. It is consistent with two-stage, depth-variable stretching of the Briançonnais lithosphere during the Jurassic. Our study represents a starting point for more sophisticated and developed numerical models, to explain rapid vertical movements in hyper-extended continental margins.
Soil moisture decline following the plantation of Robinia pseudoacacia forests: Evidence from the Loess Plateau
Authors: Liang HaiBin , Li Zongshan
Published: March 2020

Soil moisture is the foundation of ecosystem sustainability in arid and semi-arid regions, and the spatial–temporal details of soil moisture dynamics of afforested areas can benefit for land use management in watershortage regions such as the Loess Plateau of China. In this study, spatial–temporal variations in soil moisture under Robinia pseudoacacia plantations on the Loess Plateau were analyzed. A total of 147 observations of soil moisture content (SMC) data to a depth of 500 cm soil profile were collected in 23 counties via field transect surveys and analyses of published literature. The results suggested that (1) the depth-averaged SMC was generally lower under forest sites than under cropland, both in the shallow layers and in the deep profiles. This finding implied that, compared with the native vegetation, the introduced R. pseudoacacia plantations caused intense reductions in soil moisture. (2) SMC was positively correlated with climatic factors (mean annual precipitation (MAP), mean annual temperature (MAT), and the Palmer drought severity index (PDSI)), indicating that the SMC under R. pseudoacacia plantations was highly consistent with the hydrothermal conditions at the regional scale. (3) The decreasing amplitude of SMC was linearly related to the increasing number of restoration years, especially in the areas below the 500–550 mm precipitation threshold. This finding showed that the restoration ageing sequence was an influential factor that affected the regional SMC variation in R. pseudoacacia plantations on the Loess Plateau. Our results suggest that afforestation activities should be avoided if the local total precipitation is insufficient for replenishing the soil moisture and that local tree species with a lower demand for water resources should be considered a top priority for further afforestation of the Loess Plateau.
Evaporation over saturated bare soil: the role of soil texture
Authors: Li Wanxin , Wang Wenke , Brunner Philip , Wang Zhoufeng , Li Zhi , Wang Yike , Lu Yanying , Hendricks Franssen Harrie-Jan
Published: March 2020

Calculating actual bare soil evaporation (ETa) on the basis of potential bare soil evaporation (PE) is a widely followed approach in many disciplines including hydrogeology, hydrology and agricultural sciences. This approach considers that PE is independent from soil properties, and only ETa is affected by soil properties. In this work, in a unique experiment, seasonal and diurnal cycles of PE over saturated bare soil were assessed for lysimeters installed in the Guanzhong Basin, China. The assessment was made for different soil textures including gravel (PEgravel), coarse sand (PEcoarse) and fine sand (PEfine) and also open water (PEwater). Meteorological variables, ground heat flux and soil temperature were captured at a high temporal resolution (5 min.) for more than 15 consecutive months. The daily evaporation rates over saturated bare soil (PEsoil) showed clear differences between gravel, coarse sand and fine sand, with higher PE for fine sand, smaller PE for coarse sand and smallest PE for gravel, during spring and summer. In addition, PEwater was smaller than PE for the saturated bare soil lysimeters. In autumn and winter, the measured PE rates over different surfaces showed only minor differences. The measurement data also revealed that during spring and summer night-time PE was considerable with ~1.0 mm ET per night. These results can be quantitatively explained with detailed calculations of the energy balance, considering the different porosities for gravel, coarse sand and fine sand, as well as the thermal conductivities of the phases which constitute the porous media. 
Toba volcano super eruption destroyed the ozone layer and caused a human population bottleneck
Authors: Osipov Sergey , Stenchikov Georgiy , Tsigaridis Kostas , LeGrande Allegra , Bauer Susanne , Fnais Mohamed , Lelieveld Jos
Published: March 2020

Volcanic eruptions trigger a broad spectrum of climatic responses. For example, the Mount Pinatubo eruption in 1991 forced an El Niño and global cooling, and the Tambora eruption in 1815 caused the "Year Without a Summer." Especially grand eruptions such as Toba around 74,000 years ago can push the Earth's climate into a volcanic winter state, significantly lowering the surface temperature and precipitation globally. Here we present a new, previously overlooked element of the volcanic effects spectrum: the radiative mechanism of stratospheric ozone depletion. We found that the volcanic plume of Toba enhanced the UV optical depth and suppressed the primary formation of stratospheric ozone from O2 photolysis. Sulfate aerosols additionally reflect the photons needed to break the O2 bond (λ < 242 nm), otherwise controlled by ozone absorption and Rayleigh scattering alone during volcanically quiescent conditions. Our NASA GISS ModelE simulations of the Toba eruption reveal up to 50% global ozone loss due to the overall photochemistry perturbations of the sulfate aerosols. We also consider and quantify the radiative effects of SO2, which partially compensated for the ozone loss by inhibiting the photolytic O3 sink.

Our analysis shows that the magnitude of the ozone loss and UV-induced health-hazardous effects after the Toba eruption are similar to those in the aftermath of a potential nuclear conflict. These findings suggest a “Toba ozone catastrophe" as a likely contributor to the historic population decline in this period, consistent with a genetic bottleneck in human evolution.