bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Characteristics of Giant Undulations During Geomagnetic Storms
Authors: Zhou Yi‐Jia , He Fei , Zhang Xiao‐Xin , Yao Zhong‐Hua , Wei Yong , Zhang Yong‐Liang 
Published: June 2021

AbstractIn this letter, the statistical characteristics of the structures of giant undulations (GUs) during geomagnetic storms are studied for the first time, based on aurora images during 2005–2019. The GUs mainly occur within ∼4 h following the beginning of the storm main phase and finish in ±4 h around the storm peak. The most interesting feature is that the anti‐sunward edge of GUs is quasi‐stable (18–19 h MLT) during their lifetime. The latitudinal amplitudes of GUs (AGU) peak at 200–300 km while the azimuthal wavelengths (WGU) occupy several discrete values between 100 and 900 km. Both AGU and WGU are quasi‐proportional to the strength of the storms, and AGU is also proportional to WGU. There are some differences in the characteristics of AGU and WGU between pre‐ and post dusk sectors. These results would provide both statistical insight for mechanisms of dynamic auroral structures and data sources for validating magnetosphere‐plasmasphere‐ionosphere coupling models.
Seismogenic Potential of the Main Himalayan Thrust Constrained by Coupling Segmentation and Earthquake Scaling
Authors: Michel Sylvain , Jolivet Romain , Rollins Chris , Jara Jorge , Dal Zilio Luca 
Published: June 2021

AbstractRecent studies have shown that the Himalayan region is under the threat of earthquakes of magnitude nine or larger. These estimates are based on comparisons of the geodetically inferred moment deficit rate with the seismicity of the region. However, these studies did not account for the physics of fault slip, specifically the influence of frictional barriers on earthquake rupture dynamics, which controls the extent and therefore the magnitude of large earthquakes. Here we combine an improved probabilistic estimate of moment deficit rate with results from dynamic models of the earthquake cycle to more fully assess the seismogenic potential of the Main Himalayan Thrust (MHT). We propose a straightforward and efficient methodology for incorporating outcomes of physics‐based earthquake cycle models into hazard estimates. We show that, accounting for uncertainties on the moment deficit rate, seismicity and earthquake physics, the MHT is prone to rupturing in 8.7 earthquakes every T > 200 years.
A Persistent and Intense Marine Heatwave in the Northeast Pacific During 2019–2020
Authors: Chen Ziyan , Shi Jian , Liu Qinyu , Chen Hui , Li Chun 
Published: June 2021

AbstractMotivated by increasing marine heatwaves (MHWs) and their dramatic climate effects, we analyze the persistent 2019–2020 MHW, which showed significant positive sea surface temperature (SST) anomalies in the Northeast Pacific. Four SST peaks were identified during its evolution, which appeared in November 2019, April, July, and November 2020. Positive temperature anomalies were mostly located within the mixed layer for the first‐year winter peak. However, the warm core was centered around 50 m below (at the bottom of) the mixed layer for the summer (second‐year winter) peak. The dominant factor for the two wintertime peaks was a surface heat flux anomaly, with reduction in evaporative cooling due to the easterly anomaly. The heat flux and potentially the vertical entrainment combined to induce the peak in spring. In the tropical Pacific, a La Niña event occurred following this MHW, while other recorded double‐peak events were associated with El Niño or neutral conditions.
Post‐Millennium Atmospheric Temperature Trends Observed From Satellites in Stable Orbits
Authors: Zou Cheng‐Zhi , Xu Hui , Hao Xianjun , Fu Qiang 
Published: June 2021

AbstractWe develop a post‐millennium mid‐tropospheric temperature time series from continuous observations by advanced microwave sounders onboard satellites in stable sun‐synchronous orbits. Such observations have high radiometric stability and do not experience diurnal sampling changes over time, allowing us to develop merged time series from multiple satellites with an accuracy better than 0.012 Kelvin/Decade. With such high accuracy, the resulting time series can be used as a reference measurement of climate variability and trends in atmospheric temperatures. The warming rate from this time series for the atmospheric layer between surface and 10 km is 0.230 ± 0.134 Kelvin/Decade during the period from 2002 to 2020, which is ∼14% higher than the existing satellite microwave sounder datasets. Our finding provides new insight on trend differences among microwave sounder temperature data sets developed by different research groups, and is also helpful in reconciling trend differences between satellite observations and climate model simulations.
The Role of Vorticity Tilting in Northward‐Propagating Monsoon Intraseasonal Oscillation
Authors: Li Baosheng , Zhou Lei , Qin Jianhuang , Murtugudde Raghu 
Published: June 2021

AbstractThe simulation of the northward‐propagating monsoon intraseasonal oscillation (MISO) is still a grand challenge for climate models. Here, we show that the tilting of vorticity plays a critical role in the northward‐propagating MISO. During the Indian summer monsoon (ISM), the persistent vertical easterly shear of background zonal wind sets up a horizontal vorticity. Due to the meridional gradient of vertical velocity associated with convection, positive vorticity anomalies are generated to the north of the convection, where the convection is enhanced. In 19 coupled general circulation models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), it is confirmed that the simulations of MISO have a strong dependence on the simulations of this tilting but the tilting structures are not well‐captured in CMIP6 models. This offers a specific target for alleviating the model bias in MISO as well as in ISM in contemporary climate models.
Ice‐Covered Lakes of Tibetan Plateau as Solar Heat Collectors
Authors: Kirillin Georgiy B , Shatwell Tom , Wen Lijuan 
Published: June 2021

AbstractThe Qinghai‐Tibet Plateau possesses the largest alpine lake system, which plays a crucial role in the land‐atmosphere interaction. We report first observations on the thermal and radiation regime under ice of the largest freshwater lake of the Plateau. The results reveal that freshwater lakes on the Tibetan Plateau fully mix under ice. Due to strong solar heating, water temperatures increase above the maximum density value 1–2 months before the ice break, forming stable thermal stratification with subsurface temperatures >6°C. The resulting heat flow from water to ice makes a crucial contribution to ice cover melt. After the ice breakup, the accumulated heat is released into the atmosphere during 1–2 days, increasing lake‐atmosphere heat fluxes up to 500 W m−2. The direct biogeochemical consequences of the deep convective mixing are aeration of the deep lake waters and upward supply of nutrients to the upper photic layer.
Quasi‐2‐Day Wave in Low‐Latitude Atmospheric Winds as Viewed From the Ground and Space During January–March, 2020
Authors: He Maosheng , Chau Jorge L. , Forbes Jeffrey M. , Zhang Xiaoli , Englert Christoph R. , Harding Brian J. , Immel Thomas J. , Lima Lourivaldo M. , Bhaskar Rao S. Vijaya , Ratnam M. Venkat , Li Guozhu , Harlander John M. , Marr Kenneth D. , Makela Jonathan J. 
Published: June 2021

AbstractHorizontal winds from four low‐latitude (±15°) specular meteor radars (SMRs) and the Michelson Interferometer for Global High‐resolution Thermospheric Imaging (MIGHTI) instrument on the ICON satellite, are combined to investigate quasi‐2‐day waves (Q2DWs) in early 2020. SMRs cover 80–100 km altitude whereas MIGHTI covers 95–300 km. Q2DWs are the largest dynamical feature of the summertime middle atmosphere. At the overlapping altitudes, comparisons between the derived Q2DWs exhibit excellent agreement. The SMR sensor array analyses show that the dominant zonal wavenumbers are s = +2 and + 3, and help resolve ambiguities in MIGHTI results. We present the first Q2DW depiction for s = +2 and s = +3 between 95 and 200 km, and show that their amplitudes are almost invariant between 80 and 100 km. Above 106 km, Q2DW amplitudes and phases present structures that might result from the superposition of Q2DWs and their aliased secondary waves.
GNSS Observations of GIA‐Induced Crustal Deformation in Lützow‐Holm Bay, East Antarctica
Authors: Hattori A. , Aoyama Y. , Okuno J. , Doi K. 
Published: June 2021

AbstractThe Japanese Antarctic Research Expeditions have conducted long‐term Global Navigation Satellite System (GNSS) observations at a series of bedrock outcrops along the coast of Lützow‐Holm Bay, East Antarctica, to elucidate the solid Earth response to ice mass changes. These GNSS observations capture both the viscoelastic response of the solid Earth to Antarctic Ice Sheet changes since the Last Glacial Maximum, termed glacial isostatic adjustment (GIA), and elastic deformation associated with recent surface mass changes due to snowfall variations. Here, we extract the GIA signals from the Lützow‐Holm Bay GNSS data by applying an elastic deformation correction based on the mass fluctuations observed in the Gravity Recovery and Climate Experiment and the satellite altimetry. Our results indicate that the region is currently experiencing approximately 1 mm/yr of subsidence, which is large enough to influence GIA model estimations. The resultant GIA‐induced deformation response in Lützow‐Holm Bay is 1–6 mm/yr of uplift.
Probing the Damage Zone at Parkfield
Authors: Delorey Andrew A. , Guyer Robert A. , Bokelmann Götz H. R. , Johnson Paul A. 
Published: June 2021

AbstractRocks are heterogeneous materials that exhibit nonlinear elastic (anelastic) behavior at scales ranging from the laboratory to Earth. In the laboratory, typical, complex relationships exist between stress and strain that include hysteresis, finite relaxation times, strain rate, and history dependence. These behaviors are linked to important characteristics such as stress, porosity, permeability, material integrity, and material failure. We adopted a “pump‐probe” type experiment common in laboratory studies, using solid earth tides as the low‐frequency pump and empirical Green's function as the high‐frequency probe. By probing the velocity at different points in the pump cycle, we constrained important information about the strain‐modulus relationship. Near the San Andreas Fault, we observed strongly nonlinear elastic behavior that characterizes the damage zone. We also constrained important aspects of hysteretic behavior that are related to damage properties and possibly pore pressure. Away from the fault, the nonlinear behavior is diminished.
Fast Cross‐Scale Energy Transfer During Turbulent Magnetic Reconnection
Authors: Nakamura T. K. M. , Hasegawa H. , Genestreti K. J. , Denton R. E. , Phan T. D. , Stawarz J. E. , Nakamura R. , Nystrom W. D. 
Published: June 2021

AbstractMagnetic reconnection is a key fundamental process in collisionless plasmas that explosively converts magnetic energy to plasma kinetic and thermal energies through a change of magnetic field topology in a central electron‐scale region called the electron diffusion region (EDR). Past simulations and observations demonstrated that this process causes efficient energy conversion through the formation of multiple macro‐scale or micro‐scale magnetic islands/flux ropes. However, the coupling of these phenomena on different spatiotemporal scales is still poorly understood. Here, based on a new large‐scale fully kinetic simulation with a realistic, initially fluctuating magnetic field, we demonstrate that macro‐scale evolution of turbulent reconnection involving merging of macro‐scale islands induces repeated, quick formation of new electron‐scale islands within the EDR which soon grow to larger scales. This process causes an efficient cross‐scale energy transfer from electron‐ to larger‐scales, and leads to strong electron energization within the growing islands.
Amplified Waveguide Teleconnections Along the Polar Front Jet Favor Summer Temperature Extremes Over Northern Eurasia
Authors: Xu Peiqiang , Wang Lin , Vallis Geoffrey K. , Geen Ruth , Screen James A. , Wu Peili , Ding Shuoyi , Huang Ping , Chen Wen 
Published: June 2021

AbstractAn apparent increase in the frequency of summer temperature extremes over northern Eurasia has been observed in the past decade. Some of these high‐impact events were associated with amplified waveguide teleconnections embedded in the polar front jet, but it remains unclear if extreme temperatures are robustly and routinely related to amplified waves along the polar front jet. This study systematically examines relationships between planetary wave activity and temperature extremes using observations, reanalysis, and large‐ensemble simulations from multiple climate models. Months with extreme temperatures over northern Eurasia generally have amplified wave activity along the polar front jet, whereas months with near‐average temperatures tend to have attenuated wave activity. Waveguide teleconnections are particularly amplified during extremely hot and cold summer months over eastern Europe and western Russia. These findings demonstrate the important role of waveguide teleconnections along the polar front jet in generating regional temperature extremes over northern Eurasia.
Betatron Cooling of Electrons in Martian Magnetotail
Authors: Guo Z. Z. , Fu H. S. , Cao J. B. , Fan K. , Yao Z. H. , Liu Y. Y. , Chen Z. Z. , Wang Z. , Liu X. Y. , Xu Y. , Mazelle C. , Mitchell D. L. 
Published: June 2021

AbstractBetatron cooling, a plasma process losing particle energy in the perpendicular direction but reserving particle energy in the field‐aligned direction, is a consequence of magnetic depression under the conservation of magnetic moment. Such process has been widely studied in the Earth's magnetosphere but has never been reported in other planetary environment. Here, by utilizing the Mars Atmosphere and Volatile EvolutioN (MAVEN) measurements, we report two events of betatron cooling in the Martian magnetotail. In one of the events, betatron cooling occurs in the suprathermal and energetic ranges of electrons, whereas in the other event, it occurs in the thermal‐energy range. We quantitatively reproduce these two processes by using an analytical model. Gratifyingly, the cooling factor derived from the analytical model agrees well with the observation of magnetic depression. These results, for the first time demonstrating the betatron‐cooling effect beyond the Earth, are useful to understand the electron dynamics in the planetary magnetosphere.
Contrasting Response of Ultrafine Particle Number and PM2.5 Mass Concentrations to Clean Air Action in China
Authors: Zhao S. P. , Yu Y. , Yin D. Y. , Qin D. H. 
Published: June 2021

AbstractThe strictest ever Clean Air Action has been implemented since 2013 at nationwide scale in China. Nevertheless, PM2.5 (particulate matter with aerodynamic diameter smaller than 2.5 μm) mass and number of ultrafine particles (UFPs, the particles with diameters smaller than 100 nm) exhibited contrasting response to the emission mitigation policies. Unlike reduction of PM2.5 and number of accumulation mode particles, UFPs number decreased from 2012 to 2015, and then has begun to increase sharply since 2016, and annual change of number in nucleation mode particles can reach 40% at noontime during 2017–2019. We examined inter‐annual trends of mode diameter, frequency of new particle formation (NPF) events, formation and growth rates, and particles were found to be much finer and NPF events have been more frequent since 2017. The much higher temperature and stronger solar radiation induced by PM2.5 reduction could promote the formation of secondary aerosol particles at noon.
Piecewise Evolutionary Spectra: A Practical Approach to Understanding Projected Changes in Spectral Relationships Between Circulation Modes and Regional Climate Under Global Warming
Authors: Putrasahan D. A. , von Storch J.‐S. 
Published: June 2021

AbstractRegional climate variability is strongly related to large‐scale circulation modes. However, little is known about changes in their spectral characteristics under climate change. Here, we introduce piecewise evolutionary spectra to quantify time‐varying variability and co‐variability of climate variables, and use ensemble periodograms to estimate these spectra. By employing a large ensemble of climate change simulations, we show that changes in the variability and relationships of the North Atlantic Oscillation (NAO) and regional surface temperatures are disparate on individual timescales. The relation between NAO and surface temperature over high‐latitude lands weakens the most on 20‐year timescales compared to shorter timescales, whereas the relation between NAO and temperature over subtropical North Africa strengthens more on shorter timescales than on 20‐year timescales. These projected evolution and timescale‐dependent changes shed new light on the controlling factors of circulation‐induced regional changes. Accounting for them can lead to the improvement of future regional climate predictions.
Influence of Low‐Frequency PNA Variability on MJO Teleconnections to North American Atmospheric River Activity
Authors: Toride Kinya , Hakim Gregory J. 
Published: June 2021

AbstractThe Madden‐Julian oscillation (MJO) modulates atmospheric river (AR) activity along the West Coast of North America. The forecast skill of ARs based solely on the MJO phase is limited, motivating the identification of other predictive factors. Here we show that low‐frequency variability of the Pacific/North American (PNA) pattern is mostly independent of the MJO, and the monthly PNA pattern influences the MJO‐AR relationship much more robustly than other large‐scale patterns such as the El Niño Southern Oscillation and the quasi‐biennial oscillation. During PNA+ conditions, when the Pacific jet exit region is located further east than average, baroclinic wave packets extend downstream toward North America. The clear contrast in wave packets' zonal scale results in partitioning active and inactive AR phases. The PNA influence is most significant over the Pacific Northwest region of North America, where AR landfall is most frequent, with implied forecasting skill beyond 20 days.
Does Catchment Nestedness Enhance Hydrological Similarity?
Authors: Betterle A. , Botter G. 
Published: June 2021

AbstractThe topology of river networks defines the hierarchical organization of the landscape and controls the drainage pathways triggered by precipitation. This study investigates how the structure of channel networks influences spatial patterns of flow regimes by focusing on the hydrograph observed at the outlet of nested and non‐nested basins. An extensive data set spanning diverse geomorphoclimatic conditions is used to show that – when inter‐catchment distance increases – nested catchments exhibit a more pronounced decrease of streamflow correlation as compared to non‐nested sites. Thus, non‐nested basins have more correlated hydrologic responses at large distances. This unexpected behavior is explained by a geometrical model, which reveals that inter‐catchment differences in size and elevation are larger in nested sites, thereby increasing the spatial heterogeneity of key hydrological processes that shape the hydrograph. This study provides clues to critically reinterpret the hydrological response on nested versus non‐nested catchments, with relevant implications for hydrology and ecology.
Geodetic Constraints on Recent Subduction Earthquakes and Future Seismic Hazards in the Southwestern Coast of Mexico
Authors: Yu Chen , Li Zhenhong , Song Chuang 
Published: June 2021

AbstractThree major subduction earthquakes occurred on March 20, 2012 (Mw 7.4), February 16, 2018 (Mw 7.2), and June 23, 2020 (Mw 7.4) in the southwestern coast of Mexico, which caused fatalities, casualties, considerable damage, and raised safety concerns about future seismic hazards. We use satellite geodetic observations to invert for the slip distributions of the three events and then investigate their interactions. Coulomb Failure Stress (CFS) induced by their slip both on surrounding thrust and normal faults are calculated. The positive CFS changes, along with the spatial‐temporal seismicity evolution, approximate earthquake recurrence rate and interseismic coupling, collectively indicate an increased possibility of a near‐future rupture around the areas between the 2018 and 2020 events in Oaxaca. Furthermore, there is a lowered chance of shallow coastal or offshore normal earthquakes but an increased chance of inland normal ruptures.
Spatiotemporal control of CRISPR/Cas9 gene editing
Authors: Zhuo Chenya , Zhang Jiabin , Lee Jung-Hwan , Jiao Ju , Cheng Du , Liu Li , Kim Hae-Won , Tao Yu , Li Mingqiang 
Published: June 2021

AbstractThe clustered regularly interspaced short palindromic repeats (CRISPR)/associated protein 9 (CRISPR/Cas9) gene editing technology, as a revolutionary breakthrough in genetic engineering, offers a promising platform to improve the treatment of various genetic and infectious diseases because of its simple design and powerful ability to edit different loci simultaneously. However, failure to conduct precise gene editing in specific tissues or cells within a certain time may result in undesirable consequences, such as serious off-target effects, representing a critical challenge for the clinical translation of the technology. Recently, some emerging strategies using genetic regulation, chemical and physical strategies to regulate the activity of CRISPR/Cas9 have shown promising results in the improvement of spatiotemporal controllability. Herein, in this review, we first summarize the latest progress of these advanced strategies involving cell-specific promoters, small-molecule activation and inhibition, bioresponsive delivery carriers, and optical/thermal/ultrasonic/magnetic activation. Next, we highlight the advantages and disadvantages of various strategies and discuss their obstacles and limitations in clinical translation. Finally, we propose viewpoints on directions that can be explored to further improve the spatiotemporal operability of CRISPR/Cas9.
TDMA scheduling schemes targeting high channel utilization for energy‐harvesting wireless sensor networks
Authors: Gong Siliang , Liu Xiaoying , Zheng Kechen , Lu Wenwei , Zhu Yi‐hua 
Published: June 2021

AbstractAs a contention‐free channel access protocol, Time Division Multiple Access (TDMA) is widely applied in Energy Harvesting Wireless Sensor Networks (EH‐WSNs) due to ease of implementation. TDMA scheduling in EH‐WSNs faces the problem of low channel utilization since time slots assigned to some nodes may not be used by them due to shortage of energy or data. It is important to design TDMA scheduling schemes that enhance channel utilization. In this paper, the Fixed Frame Size Scheme (FFSS) and the Adaptive Frame Size Scheme (AFSS) are proposed to improve channel utilization of EH‐WSNs. The FFSS aims at the optimal TDMA slot assignment for the TDMA scheduling with fixed frame size, and the AFSS considers the TDMA with variable frame size and targets both the optimal frame size and the optimal slot assignment. The optimization problems maximizing channel utilization are formulated for the FFSS and the AFSS, respectively, which take the upcoming energy and data into account. The optimization problems are transformed into assignment‐like problems and solved by the Hungarian‐based algorithm in polynomial time. Simulation results indicate that the proposed FFSS and AFSS can considerably improve channel utilization in the EH‐WSNs compared with the existing TDMA scheduling schemes.