bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impact of the Ensemble Kalman Filter Based Coupled Data Assimilation System on Seasonal Prediction of Indian Summer Monsoon Rainfall
Authors: Gade Sagar V. , Sreenivas Pentakota , Rao Suryachandra A. , Srivastava Ankur , Pradhan Maheswar 
Published: July 2022

AbstractThe sensitivity of seasonal prediction (June to September) of Indian monsoon to initial state from two variants of coupled data assimilation (CDA) products, viz. the Climate Forecast System (CFS) Reanalysis (CFSR) and Indian Institute of Tropical Meteorology, University of Maryland‐ Weakly Coupled Analysis (IWCA) is explored in this study. The IWCA implements the local ensemble transform Kalman filter, and incorporates theoretically advanced features of flow‐dependency and ensemble‐based analysis compared to CFSR. The CFS version‐2 predictions using IWCA simulate the large‐scale monsoon features, and convection centers well, and improve prediction skills compared to CFSR predictions. The enhanced analysis quality and Ocean‐Atmospheric cross‐domain equilibrium in IWCA reduce initial shocks in springtime predictions. Further, the sustained ensemble consistency aided to simulate the variability better and improved the seasonal predictions. The study strongly advocates the adaptation of advanced CDA methods for seasonal monsoon and probable seamless predictions.
Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations
Authors: Ringler A. T. , Anthony R. E. , Aster R. C. , Ammon C. J. , Arrowsmith S. , Benz H. , Ebeling C. , Frassetto A. , Kim W.‐Y. , Koelemeijer P. , Lau H. C. P. , Lekić V. , Montagner J. P. , Richards P. G. , Schaff D. P. , Vallée M. , Yeck W. 
Published: July 2022

AbstractGlobal seismographic networks (GSNs) emerged during the late nineteenth and early twentieth centuries, facilitated by seminal international developments in theory, technology, instrumentation, and data exchange. The mid‐ to late‐twentieth century saw the creation of the World‐Wide Standardized Seismographic Network (1961) and International Deployment of Accelerometers (1976), which advanced global geographic coverage as seismometer bandwidth increased greatly allowing for the recording of the Earth's principal seismic spectrum. The modern era of global observations and rapid data access began during the 1980s, and notably included the inception of the GEOSCOPE initiative (1982) and GSN (1988). Through continual improvements, GEOSCOPE and the GSN have realized near‐real time recording of ground motion with state‐of‐art data quality, dynamic range, and timing precision to encompass 180 seismic stations, many in very remote locations. Data from GSNs are increasingly integrated with other geophysical data (e.g., space geodesy, infrasound and Interferometric Synthetic Aperture Radar). Globally distributed seismic data are critical to resolving crust, mantle, and core structure; illuminating features of the plate tectonic and mantle convection system; rapid characterization of earthquakes; identification of potential tsunamis; global nuclear test verification; and provide sensitive proxies for environmental changes. As the global geosciences community continues to advance our understanding of Earth structure and processes controlling elastic wave propagation, GSN infrastructure offers a springboard to realize increasingly multi‐instrument geophysical observatories. Here, we review the historical, scientific, and monitoring heritage of GSNs, summarize key discoveries, and discuss future associated opportunities for Earth Science.
Diffuse Radiation Forcing Constraints on Gross Primary Productivity and Global Terrestrial Evapotranspiration
Authors: Chakraborty T. , Lee X. , Lawrence D. M. 
Published: July 2022

AbstractThe diffuse radiation fertilization effect—the increase in plant productivity in the presence of higher diffuse radiation (K↓,d)—is an important yet understudied aspect of atmosphere‐biosphere interactions and can modify the terrestrial carbon, energy, and water budgets. The K↓,d fertilization effect links the carbon cycle with clouds and aerosols, all of which are large sources of uncertainties for our current understanding of the Earth system and for future climate projections. Here we establish to what extent observational and modeling uncertainty in sunlight's diffuse fraction (kd) affects simulated gross primary productivity (GPP) and terrestrial evapotranspiration (λE). We find only 48 eddy covariance sites with simultaneous sufficient measurements of K↓,d with none in the tropical climate zone, making it difficult to constrain this mechanism globally using observations. Using a land modeling framework based on the latest version of the Community Land Model, we find that global GPP ranges from 114 Pg C year−1 when using kd forcing from the Modern‐Era Retrospective analysis for Research and Applications, version 2 reanalysis to a ∼7% higher value of 122 Pg C year−1 when using the Clouds and the Earth's Radiant Energy System satellite product, with especially strong differences apparent over the tropical region (mean increase ∼9%). The differences in λE, although smaller (−0.4%) due to competing changes in shaded and sunlit leaf transpiration, can be greater than regional impacts of individual forcing agents like aerosols. Our results demonstrate the importance of comprehensively and systematically validating the simulated kd by atmosphere modules as well as the response to differences in kd within land modules across Earth System Models.
Inverse Magnetic Fabrics Caused by Magnetofossils in the Northwestern South China Sea Since End of the Last Glacial
Authors: Wang Haosen , Xu Xing , Gai Congcong , Liu Jiabo , Zhong Yi , Jiang Xiaodong , Zhang Yanan , Ferré Eric C. , He Kuang , Liu Qingsong 
Published: July 2022

AbstractThe relationships among the abundance of magnetofossils, the ensuing magnetic properties, and the controlling paleoenvironmental factors in marine sediments remain broadly unexplored. Here, we identify magnetofossils in core XB1 from the northwestern South China Sea (SCS) since end of the Last Glacial. Using rock magnetic and electron microscopic data, we propose a model that links the anisotropy of magnetic susceptibility fabric and the abundance of magnetofossils. The magnetofossil concentration in sediments increases significantly during the 14.7–4.7 ka period, which in turns leads to inverse magnetic fabrics and near‐horizontal of the minimum magnetic susceptibility axes. Further, we show that the abundance of magnetofossils is linked to paleoenvironmental changes in the northwestern SCS. The production and preservation of magnetofossils during the 14.7–4.7 ka period are promoted by an intensified East Asian summer monsoon and sluggish deep‐water ventilation, while the paucity of magnetofossils after 4.7 ka is attributed to high oxygen content.
More Intense, Organized Deep Convection With Shrinking Tropical Ascent Regions
Authors: Wodzicki Kyle R. , Rapp Anita D. 
Published: July 2022

AbstractChanges in the frequency and morphology of convection in a warming climate have major implications for the hydrologic cycle and continue to be a large source of variability in climate models. Recent studies of model output indicate a narrowing and intensification of the ascending branch of the Hadley circulation (i.e., the Intertropical Convergence Zone). The present work uses tropical ascent area fraction (Au) and Tropical Rainfall Measurement Mission precipitation features to study global tropical variability in convection with ascent area changes in the current climate. Ascent region convection becomes more intense and organized when Au is low. Overall increases in mean precipitation as the tropical ascent regions shrink are primarily driven by an increase in the areal extent of convective systems, rather than intensity of the convective system rainfall, suggesting an increase in the organization and aggregation of convection as the climate continues to warm.
Severe Drought Conditions in Northern East Asia During the Early Pliocene Caused by Weakened Pacific Meridional Temperature Gradient
Authors: Zheng Yanhong , Fedorov Alexey V. , Burls Natalie J. , Zhang Rui , Brierley Chris M. , Fang Zhengkun , Yu Xuefeng , Xian Feng , Lu Hongxuan 
Published: July 2022

AbstractThe evolution of hydroclimate in East Asia during the Pliocene—a potential analog of the future greenhouse climate—remains highly uncertain. Here we reconstruct changes in the hydroclimate of Northern China during this epoch. Our results reveal previously undocumented severe drought conditions that persisted through the early Pliocene with a significantly greater magnitude than suggested by other records. Using a broad hierarchy of climate simulations, we find that reduction in the Pacific meridional sea surface temperature (SST) gradient has particularly strong impacts on precipitation over Northern China, which suggests its key role in maintaining drought conditions during the early Pliocene. The weaker Pacific meridional SST gradient causes the weakening of the East Asian summer monsoon precipitation over this region via a reduction of atmospheric northward moisture transport from the ocean, which enhances aridity inland. Our results highlight the fundamental control of the tropical ocean on the extra‐tropical hydrological cycle.
Varying Shear Wave Splitting Parameters Suggest Interaction Between Lithosphere and Asthenosphere in Arxan‐Chaihe Volcanic Field, NE China
Authors: Qiang Zhengyang , Wu Qingju , Li Yonghua , Zhang Fengxue 
Published: July 2022

AbstractOver 2 years of broadband seismic data from 27 temporary stations deployed in the Arxan‐Chaihe Volcanic Field (ACVF) provides us a valued opportunity to study mantle deformation and related geodynamic processes in NE China intraplate region. We estimated 153 pairs of high‐quality teleseismic shear wave splitting parameters at 22 stations and 98 non‐splitting measurements at 19 stations. Most of the stations in ACVF are characterized by NNW–SSE trending fast directions with variable splitting delay times, suggesting the fossilized extensional deformation within the lithosphere is locally thermal erased by the hot mantle upwellings associated with the volcanism. In the region south of the 46.5°N, a sharp swing of fast polarization occurs, and both nearly NW‐SE and W‐E oriented fast directions are observed, which could be explained by small local mantle convection caused by the lithospheric delamination.
Fluid‐Enhanced Neotectonic Faulting in the Cratonic Lithosphere of the Nullarbor Plain in South‐Central Australia
Authors: Yang H. , Sellmann S. , Quigley M. 
Published: July 2022

AbstractThe Nullarbor Plain is underlain by thick cratonic lithospheric mantle that is almost devoid of contemporary seismicity. Analysis of high‐resolution digital elevation models indicates neotectonic fault‐propagation fold traces on the nearly flat karst landscape that locally extend to lengths of >100 km, suggesting potential for hosting large (>7.3–7.5) moment magnitude earthquakes. Along‐strike maximum displacements are not proportional to neotectonic fold surface trace length but are spatially associated with crust‐scale electrical conductors identified in magnetotelluric surveys. Two major conductors penetrate from the upper crust to the uppermost mantle (at depths < 60 km) along crustal scale shear zones. Conductivity in the uppermost mantle shear zones is higher than conductivity at increased depth, suggesting fluid‐enhanced enrichment with hydrogen and/or carbon. Lithospheric fluid localization associated with ancient slab subduction and/or hydrothermal alteration may have weakened pre‐existing faults and enhanced neotectonic faulting in the Nullarbor Plain.
Vertical Propagation Speeds of Gravity Waves in the Daytime as a Precursor to the Onset of the Equatorial Spread‐F
Authors: Mandal Subir , Pallamraju Duggirala , Pant Tarun Kumar 
Published: July 2022

AbstractThe equatorial spread‐F (ESF) refers to the spread observed in return echoes of ionograms. Such spread in reflected echoes is found both in range and frequency, which can last for a few hours. These are due to large‐scale plasma irregularities occurring in the ionospheric heights on some nights. Under seemingly identical background conditions, ESF might occur on one night but remain absent on the other. These plasma irregularities adversely affect the trans‐ionospheric radio wave propagation but their occurrence on a given night continues to be one of the missing elements in our understanding of the equatorial ionospheric phenomena. In this work, the vertical propagation of gravity waves in daytime thermosphere has been shown to be a crucial parameter for the generation of ESF during post‐sunset hours. Using electron density profiles obtained from digisonde at Trivandrum, a dip‐equatorial location in India, we found that vertical propagation activity of gravity waves exists on 85% of the ESF days, whereas it is only 50% for the days without the occurrence of ESF during post‐sunset hours. Further, vertical propagation speeds of these gravity waves are higher on the ESF days than on the non‐ESF days. Also, ESF has been found to occur on 100% of the occasions, whenever the vertical speeds of these gravity waves are greater than 80 ms−1. This threshold value of vertical propagation speeds of gravity waves can be used to predict the ESF occurrence around 12–14 LT on that day, which is much in advance of the occurrence of ESF.
Combined Scattering of Suprathermal Electrons by Whistler‐Mode Chorus and Electromagnetic Ion Cyclotron Waves in the Low‐Density Plasmatrough
Authors: Yu Jiang , Wang Jing , He Zhaoguo , Liu Nigang , Li Kun , Ren Aojun , Li Liuyuan , Cui Jun , Cao Jinbin 
Published: July 2022

AbstractBased on the observation from Van Allen Probes, we report an event of intense and simultaneous electromagnetic ion cyclotron (EMIC) and chorus waves inside the low‐density plasmatrough. By calculating the scattering rates and performing the diffusion simulations, we for the first time evaluate the combined scattering of suprathermal electrons by EMIC and chorus waves in the low‐density plasmatrough. Landau acceleration of suprathermal electrons by EMIC waves is mainly restricted at large pitch angles while their scattering loss by chorus waves occurs at small pitch angles well below 90°. When EMIC and chorus waves are simultaneously present, the scattering of suprathermal electrons by the two waves is very different from that by each type of waves alone. EMIC waves play a complementary role in the scattering of suprathermal electrons by chorus waves, which facilitate the scattering of suprathermal electrons over all pitch angles. The near‐equatorially minoring suprathermal electrons are firstly scattered toward intermediate pitch angles by EMIC waves and further toward the loss cone by chorus waves. Our results highlight the complementary role of different types of magnetospheric waves in the suprathermal electron scattering, which potentially have vital implications for the dynamics of suprathermal electrons in the planetary magnetosphere.
Parametric Model for Eddies‐Induced Sound Speed Anomaly in Five Active Mesoscale Eddy Regions
Authors: Chen Wen , Zhang Yongchui , Liu Yuyao , Ma Lina , Wang Haodi , Ren Kaijun , Chen Shiyao 
Published: July 2022

AbstractMesoscale eddies are ubiquitous in the ocean. Their acoustic properties have attracted considerable research attention. However, the three‐dimensional structure for eddy‐induced sound speed anomalies has remained obscure, hindering further understanding of the impact of eddies on acoustic propagation. To solve this problem, a region‐dependent parametric model for eddy‐induced sound speed anomaly (SSA) structure is established by performing a composite analysis based on abundant profiles measured by Argo floats and the corresponding satellite altimetry data. The parametric SSA model can be applied to fast reconstruct the underwater sound speed (SS) field of the eddy based only on the intensity and radius of the eddy. A comparison with a surveyed eddy shows that the errors of the reconstructed SSA are 2.36 m/s (8.33%) in strength and 37 m (9.37%) in core depth. The reconstructed SS field is employed to study the sound propagation characteristics in the presence of a cyclonic eddy with the ray‐tracing method. The results show that the parametric model can advance eddy‐acoustic effect research in the case of observation data shortages.
Melt Production and Ejection From Lunar Intermediate‐Sized Impact Craters: Where Is the Molten Material Deposited?
Authors: Liu T. , Luther R. , Manske L. , Wünnemann K. 
Published: July 2022

AbstractDifferently aged impact melt in lunar samples is key to unveiling the early bombardment history of the Moon. Due to the mixing of melt products ejected from distant craters, the interpretations of the origin of lunar samples are difficult. We use numerical modeling for a better quantitative understanding of the production of impact‐induced melt and in particular its distribution in ejecta blankets for lunar craters with sizes ranging from 1.5 to 50 km. We approximate the lunar stratigraphy with a porosity gradient, which represents the gradual transition from upper regolith via megaregolith to the solid crustal material. For this lunar setting, we quantify the melt production relative to crater volume and derive parameters describing its increasing trend with increasing transient crater size. We found that about 30%–40% of the produced melt is ejected from the crater. The melt concentration in the ejecta blanket increases almost linearly with distance from the crater center, while the thickness of the ejecta blanket decreases following a power law. Our study demonstrates that if in lunar samples the concentration of a melt with a certain age is interpreted to be of a nonlocal origin, these melts could be the impact products of a large crater (>10 km) located hundreds of kilometers away.
SRF2—A Short‐Term (1–24)h foF2 Prediction Method
Authors: Perrone L. , Mikhailov A. V. 
Published: July 2022

AbstractA sunrise F2‐layer short‐term (1–24) h foF2 prediction method has been developed to forecast foF2 variations at a given ionosonde station during magnetically quiet and disturbed periods. The proposed method efficiently describes both positive and negative quiet time F2‐layer disturbances under daily Ap <30 nT and this was done for the first time. A comparison with modern global empirical models demonstrates a statistically significant advantage over them under various seasons and levels of solar activity.
Effect of Flow‐Direction‐Dependent Dispersivity on Seawater Intrusion in Coastal Aquifers
Authors: Fahs Marwan , Koohbor Behshad , Shao Qian , Doummar Joanna , Baalousha Husam M. , Voss Clifford I. 
Published: July 2022

AbstractFlow‐direction‐dependent (FDD) dispersivity in coastal aquifers (CAs) may strongly affect the inland extend of seawater intrusion (SWI) and the accompanying vertical salinity distribution. FDD dispersivity may predict greater inland intrusion of the saltwater wedge, but less vertical spreading of salinity than does the classical flow‐direction‐independent (FDI) dispersivity, the standard currently employed in most numerical CA models. Dispersion processes play a key role in the SWI process and directly affect CA pumped water quality. Constant FDI dispersivities may be inappropriate in representing mixing processes due to large differences between depth and horizontal salinity transport scales, and due to typical structured heterogeneities in aquifer fabrics. Comparison of FDI and FDD model forecasts for the classical Henry problem (HP) steady‐state SWI, based on a new HP semianalytical solution with FDD and on a numerical FDI model modified to additionally represent FDD, highlights the theoretical types of differences implied by these alternative dispersivity assumptions and exactly how each parameter affects the solution. Large differences between FDI and FDD dispersivity forecasts of time‐dependent SWI in large scale heterogeneous aquifers occur in a typical CA (Akkar CA, Lebanon). The FDD model forecasts that future salinities in pumping wells will exceed the potable water limit, whereas the FDI model greatly underestimates the historic inland intrusion of the saltwater wedge and forecasts no impact on future Akkar CA potable water supply. These results indicate the importance of employing the appropriate dispersion process representation when creating model‐based SWI forecasts, especially for developing effective CA management strategies.
Merging bound states in the continuum by harnessing higher-order topological charges
Authors: Kang Meng , Mao Li , Zhang Shunping , Xiao Meng , Xu Hongxing , Chan Che Ting 
Published: July 2022

AbstractBound states in the continuum (BICs) can confine light with a theoretically infinite Q factor. However, in practical on-chip resonators, scattering loss caused by inevitable fabrication imperfection leads to finite Q factors due to the coupling of BICs with nearby radiative states. Merging multiple BICs can improve the robustness of BICs against fabrication imperfection by improving the Q factors of nearby states over a broad wavevector range. To date, the studies of merging BICs have been limited to fundamental BICs with topological charges ±1. Here we show the unique advantages of higher-order BICs (those with higher-order topological charges) in constructing merging BICs. Merging multiple BICs with a higher-order BIC can further improve the Q factors compared with those involving only fundamental BICs. In addition, higher-order BICs offer great flexibility in realizing steerable off-Γ merging BICs. A higher-order BIC at Γ can split into a few off-Γ fundamental BICs by reducing the system symmetry. The split BICs can then be tuned to merge with another BIC, e.g., an accidental BIC, at an off-Γ point. When the in-plane mirror symmetry is further broken, merging BICs become steerable in the reciprocal space. Merging BICs provide a paradigm to achieve robust ultrahigh-Q resonances, which are important in enhancing nonlinear and quantum effects and improving the performance of optoelectronic devices.