bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Evaluation of a New Urban Parameterization in the Weather Research and Forecasting (WRF) Model
Authors: Bhautmage Utkarsh Prakash , Fung Jimmy Chi Hung , Pleim Jonathan , Wong Michael Mau Fung
Published: August 2022

In mesoscale Weather Research and Forecasting (WRF) model, several urban‐modeling options exist, such as Single‐layer Urban Canopy Model, Building Effect Parameterization, and Building Energy Model. However, these models have limitations in terms of the choice of land surface models (LSMs) and planetary boundary layer (PBL) schemes, the associated computational expenses, and other constraints. Recently, Dy et al. (2019, https://doi.org/10.1029/2018JD029333) included the urban‐momentum drag effect for wind‐speed modeling by developing a new multilayer model based on a modified nonlocal Asymmetric Convective Model version‐2 (ACM2) PBL scheme. This urban‐based ACM2 (UACM) has demonstrated a significantly improved ability over the base‐ACM2 (BACM) to predict wind speed near the urban ground surface and shown an inflection point at roof level in the vertical profile of horizontal wind. In this study, urban thermal and moisture components are introduced into the Pleim‐Xiu (PX) LSM and coupled with UACM. The diurnal variation in street, walls, and roof‐surface temperatures is modeled using the two‐layer force‐restore algorithm. Simple radiation treatment is considered to account for shadowing on streets based on the solar zenith angle and building morphology. Heat and moisture flux evolution are considered explicitly on all urban surfaces. The advantages of this novel UACM are simple formulation, more efficient execution, and its requirement for only a few fundamental urban morphological parameters. The idealized and real urban data case WRF simulations are performed over the Pearl River Delta region in southern China to test the new UACM. The computationally efficient UACM is expected to perform faster for operational forecasting runs.
Microphysical Piggybacking in the Weather Research and Forecasting Model
Authors: Sarkadi Noémi , Xue Lulin , Grabowski Wojciech W. , Lebo Zachary J. , Morrison Hugh , White Bethan , Fan Jiwen , Dudhia Jimy , Geresdi István
Published: August 2022

This paper presents incorporation of the microphysical piggybacking into the Weather Research and Forecasting (WRF) model. Microphysical piggybacking is to run a single simulation applying two microphysical schemes, the first scheme driving the simulation and the second piggybacking this simulated flow. “Driving the simulation” means that the simulated microphysical processes, affect the cloud buoyancy and thus force the simulated flow. In contrast, the piggybacking variables are advected by the simulated flow and undergo microphysical transformation, but they do not affect the simulated flow (like in prescribed flow—kinematic—simulations). The two sets of variables (driver and piggybacker) include temperature, water vapor mixing ratio, and all microphysical variables. We provide details of implementing piggybacking into the WRF model, illustrate its applications, and demonstrate the benefits of this methodology in two idealized three‐dimensional cases: (a) a squall line case applying two microphysics schemes, the Thompson bulk microphysics scheme and the University of Pécs/NCAR bin (UPNB) scheme. The piggybacking simulations revealed that the microphysics‐dynamics interaction plays a more important role than the pure microphysical size sorting effect in the transition zone formation. (b) A case of daytime shallow‐to‐deep convective development over land. This case uses the UPNB scheme and contrasts convection developing in environments with either pristine or polluted cloud condensation nuclei (CCN). The piggybacking results indicated that the increase of cloud cover and decrease of supersaturation are mainly associated with the microphysical effect of increasing CCN while the change of precipitation on the ground is also influenced by microphysics‐dynamics interactions.
The Effects of Numerical Dissipation on Hurricane Rapid Intensification With Observational Heating
Authors: Hasan M. B. , Guimond S. R. , Yu M. L. , Reddy S. , Giraldo F. X.
Published: August 2022

The computational fluid dynamics of hurricane rapid intensification (RI) is examined through idealized simulations using two codes: a community‐based, finite‐difference/split‐explicit model (WRF) and a spectral‐element/semi‐implicit model (NUMA). The focus of the analysis is on the effects of implicit numerical dissipation (IND) in the energetics of the vortex response to heating, which embodies the fundamental dynamics in the hurricane RI process. The heating considered here is derived from observations: four‐dimensional, fully nonlinear, latent heating/cooling rates calculated from airborne Doppler radar measurements collected in a hurricane undergoing RI. The results continue to show significant IND in WRF relative to NUMA with a reduction in various intensity metrics: (a) time‐integrated, mean kinetic energy values in WRF are ∼20% lower than NUMA and (b) peak, localized wind speeds in WRF are ∼12 m/s lower than NUMA. Values of the eddy diffusivity in WRF need to be reduced by ∼50% from those in NUMA to produce a similar intensity time series. Kinetic energy budgets demonstrate that the pressure contribution is the main factor in the model differences with WRF producing smaller energy input to the vortex by ∼23%, on average. The low‐order spatial discretization of the pressure gradient in WRF is implicated in the IND. In addition, the eddy transport term is found to have a largely positive impact on the vortex intensification with a mean contribution of ∼20%. Overall, these results have important implications for the research and operational forecasting communities that use WRF and WRF‐like numerical models.
Variations on a Pathway to an Early Eocene Climate
Authors: Henry Matthew , Vallis Geoffrey K.
Published: August 2022

The climate of the early Eocene was characterized by much higher temperatures and a smaller equator‐to‐pole surface temperature gradient than today. Comprehensive climate models have been reasonably successful in simulating that climate in the annual average. However, good simulations of the seasonal variations, and in particular much warmer Arctic winters over land, have proven more difficult. Further, while increased greenhouse gases seems necessary to achieve an Eocene climate, it is unclear whether there is a unique combination of factors that leads to agreement with all available proxies. Here we use a very flexible General Circulation Model to examine the sensitivity of the modeled climate to differences in CO2 concentration, land surface properties, ocean heat transport, and cloud extent and thickness. Even in the absence of ice or changes in cloudiness, increasing the CO2 concentration leads to a polar‐amplified surface temperature change because of increased water vapor levels combined with the lack of convection at high latitudes, with the nonlinear dependence of longwave radiation on temperature amplifying the increase in winter over land. Additional low clouds over Arctic land generally decrease summer temperatures and further increase winter temperatures (except at very high CO2 levels). An increase in the land surface heat capacity, plausible given large changes in vegetation, also decreases the Arctic land seasonality. Thus, different combinations of factors—high CO2 levels, changes in low‐level clouds, and an increase in land surface heat capacity—can lead to a simulation within the proxy uncertainty range of the majority of proxy data.
Per‐ and Polyfluoroalkyl Substances (PFAS) in Subsurface Environments: Occurrence, Fate, Transport, and Research Prospect
Authors: Lyu Xueyan , Xiao Feng , Shen Chongyang , Chen Jingjing , Park Chang Min , Sun Yuanyuan , Flury Markus , Wang Dengjun
Published: August 2022

Per‐ and polyfluoroalkyl substances (PFASs), also known as “forever chemicals,” are manmade chemicals that have been increasingly detected in various geological settings since the early 2000s. The soil and subsurface environments are the geological media commonly affected by PFAS. We conducted a comprehensive review of peer‐reviewed articles published from 2010 through 2022 concerning the fate and transport of PFAS in subsurface environments. This review is organized into different subsections, covering the basics of PFAS properties and how they affect the occurrence, fate, and transport of PFAS, the fundamental processes affecting subsurface transport and fate of PFAS, and mathematical models for describing and predicting PFAS transport behaviors. Mechanisms governing PFAS transport in the subsurface environment, including the sorption of PFAS at the air‐water interface, solid‐water interface, and nonaqueous phase liquids‐water interface, were explored in detail. Challenges and future research priorities are identified to better mitigate the global challenges of PFAS contamination.
Structural Architecture and Attenuation of the Ductile Lower Plate of the Ruby Mountain‐East Humboldt Range Metamorphic Core Complex, Northeast Nevada
Authors: Zuza Andrew V. , Levy Drew A. , Dee Seth , DesOrmeau Joel W. , Cheng Feng , Li Xiangzhong
Published: August 2022

Strongly deformed footwall rocks exposed in metamorphic core complexes (MCC) of the North American Cordillera were exhumed via ductile attenuation, mylonitic shearing, and detachment faulting. Whether these structures accommodated diapiric upwelling or regional extension via low‐angle normal faulting is debated. The Ruby Mountains‐East Humboldt Range MCC, northeast Nevada, records top‐west normal‐sense exhumation of deformed Proterozoic‐Paleozoic stratigraphy and older basement. We conducted 1:24,000‐scale mapping of the southwestern East Humboldt Range, with integrated structural, geochemical, and geochronological analyses to characterize the geometry and kinematics of extension and exhumation of the mylonitized footwall. Bedrock stratigraphy is pervasively intruded by Cretaceous, Eocene, and Oligocene intrusions, but observations of a coherent stratigraphic section show >80% vertical attenuation of Neoproterozoic to Ordovician rocks. These rocks are penetratively sheared with top‐west kinematics. The shear zone thus experienced combined pure‐ and simple‐shear (i.e., general shear) strain. We argue that this shear zone was syn‐/post‐kinematic with respect to Oligocene plutonism because: (a) mylonitic shearing spatially corresponds with preceding Oligocene intrusions; (b) thermochronology reveals that the shear zone experienced substantial cooling and exhumation after Oligocene plutonism; and (c) the mylonites are crosscut by undated, but likely late Oligocene, leucogranite. We propose that Eocene mantle‐derived magmatism and thermal incubation led to Oligocene diapiric upwelling of the middle crust, with ductile stretching focused on the flanks of this upwarp. Regional Basin and Range extension initiated later in the middle Miocene. Therefore, the development of the East Humboldt Range shear zone was not driven by regional extension and coupled detachment faulting.
Dynamics of Unusual Extreme Rainfall Events Over Different Altitudes Using Richardson Number
Authors: Ullah Kalim , Ikram Farah
Published: August 2022

To delineate the dynamic stability of a moist atmosphere and to measure stability within a statically stable atmosphere, local Richardson number (Ri) and Brunt‐Väisälä (BV) frequency are used in this study. The BV frequency is an important parameter that is widely used in dynamic meteorology and is calculated by replacing potential temperature with equivalent potential temperature in a moist atmosphere. For this purpose, extreme rainfall events were simulated by the WRF model. These events occurred on 9 September 2012 and 28 July 2010 during the summer monsoon in areas of different altitudes (ranging approximately from 100 to 3,500 m) which resulted in flash floods, loss of lives, and property damages in southern and northern parts of Pakistan. In the present case Ri (local Richardson number based on potential temperature) and Rie (local Richardson number based on equivalent potential temperature) are applied to investigate instability (Rie < 1) in a moist atmosphere. The results show that the values of Rie < 1 are mainly located in the lower‐to‐upper troposphere over the rainfall areas. The analysis shows that Rie is more suitable index for describing the convective instability in a moist saturated atmosphere. The results of Ri and Rie were justified with the European Centre for Medium‐Range Weather Forecasts fifth generation reanalysis (ERA5 hourly) available from Climate Data Store. Moreover, negative values of vertical velocity (hPa/s) clearly show large‐scale dynamical uplifting associated with instability resulting in a severe thunderstorm. Further, strong synoptic forcings also play a key role to develop deep convection over the region. In addition, maximum convective available potential energy (3,000 J/kg) and K‐index (>40) were observed over the areas of high instability that dominate its role in enhancing convection during the events.
Mitigation Strategies to Improve Reproducibility of Poverty Estimations From Remote Sensing Images Using Deep Learning
Authors: Machicao J. , Ben Abbes A. , Meneguzzi L. , Corrêa P. L. P. , Specht A. , David R. , Subsol G. , Vellenich D. , Devillers R. , Stall S. , Mouquet N. , Chaumont M. , Berti‐Equille L. , Mouillot D.
Published: August 2022

The challenges of Reproducibility and Replicability (R & R) in computer science experiments have become a focus of attention in the last decade, as efforts to adhere to good research practices have increased. However, experiments using Deep Learning (DL) remain difficult to reproduce due to the complexity of the techniques used. Challenges such as estimating poverty indicators (e.g., wealth index levels) from remote sensing imagery, requiring the use of huge volumes of data across different geographic locations, would be impossible without the use of DL technology. To test the reproducibility of DL experiments, we report a review of the reproducibility of three DL experiments which analyze visual indicators from satellite and street imagery. For each experiment, we identify the challenges found in the data sets, methods and workflows used. As a result of this assessment we propose a checklist incorporating relevant FAIR principles to screen an experiment for its reproducibility. Based on the lessons learned from this study, we recommend a set of actions aimed to improve the reproducibility of such experiments and reduce the likelihood of wasted effort. We believe that the target audience is broad, from researchers seeking to reproduce an experiment, authors reporting an experiment, or reviewers seeking to assess the work of others.
Relative Timing of Off‐Axis Volcanism From Sediment Thickness Estimates on the 8°20’N Seamount Chain, East Pacific Rise
Authors: Fabbrizzi Andrea , Parnell‐Turner Ross , Gregg Patricia M. , Fornari Daniel J. , Perfit Michael R. , Wanless V. Dorsey , Anderson Molly
Published: August 2022

Volcanic seamount chains on the flanks of mid‐ocean ridges record variability in magmatic processes associated with mantle melting over several millions of years. However, the relative timing of magmatism on individual seamounts along a chain can be difficult to estimate without in situ sampling and is further hampered by Ar40/Ar39 dating limitations. The 8°20’N seamount chain extends ∼170 km west from the fast‐spreading East Pacific Rise (EPR), north of and parallel to the western Siqueiros fracture zone. Here, we use multibeam bathymetric data to investigate relationships between abyssal hill formation and seamount volcanism, transform fault slip, and tectonic rotation. Near‐bottom compressed high‐intensity radiated pulse, bathymetric, and sidescan sonar data collected with the autonomous underwater vehicle Sentry are used to test the hypothesis that seamount volcanism is age‐progressive along the seamount chain. Although sediment on seamount flanks is likely to be reworked by gravitational mass‐wasting and current activity, bathymetric relief and Sentry vehicle heading analysis suggest that sedimentary accumulations on seamount summits are likely to be relatively pristine. Sediment thickness on the seamounts' summits does not increase linearly with nominal crustal age, as would be predicted if seamounts were constructed proximal to the EPR axis and then aged as the lithosphere cooled and subsided away from the ridge. The thickest sediments are found at the center of the chain, implying the most ancient volcanism there, rather than on seamounts furthest from the EPR. The nonlinear sediment thickness along the 8°20’N seamounts suggests that volcanism can persist off‐axis for several million years.
Laboratory Assessment of the Impact of Chemical Oxidation, Mineral Dissolution, and Heating on the Nitrogen Isotopic Composition of Fossil‐Bound Organic Matter
Authors: Martínez‐García Alfredo , Jung Jonathan , Ai Xuyuan E. , Sigman Daniel M. , Auderset Alexandra , Duprey Nicolas N. , Foreman Alan , Fripiat François , Leichliter Jennifer , Lüdecke Tina , Moretti Simone , Wald Tanja
Published: August 2022

Fossil‐bound organic material holds great potential for the reconstruction of past changes in nitrogen (N) cycling. Here, with a series of laboratory experiments, we assess the potential effect of oxidative degradation, fossil dissolution, and thermal alteration on the fossil‐bound N isotopic composition of different fossil types, including deep and shallow water scleractinian corals, foraminifera, diatoms and tooth enamel. Our experiments show that exposure to different oxidizing reagents does not significantly affect the N isotopic composition or N content of any of the fossil types analyzed, demonstrating that organic matter is well protected from changes in the surrounding environment by the mineral matrix. In addition, we show that partial dissolution (of up to 70%–90%) of fossil aragonite, calcite, opal, or enamel matrixes has a negligible effect on the N isotopic composition and N content of the fossils. These results suggest that the isotopic composition of fossil‐bound organic material is relatively uniform, and also that N exposed during dissolution is lost without significant isotopic discrimination. Finally, our heating experiments show negligible changes in the N isotopic composition and N content of all fossil types at 100°C. At 200°C and hotter, any N loss and associated nitrogen isotope changes appear to be directly linked to the sensitivity of the mineral matrix to thermal stress, which depends on the biomineral type. These results suggest that, so long as high temperature does not compromise the mineral structure, the biomineral matrix acts as a closed system with respect to N, and the N isotopic composition of the fossil remains unchanged.
Compositional Data Analysis (CoDA) of Clinopyroxene From Abyssal Peridotites
Authors: Nishio I. , Itano K. , Waterton P. , Tamura A. , Szilas K. , Morishita T.
Published: August 2022

We analyze a large database of abyssal peridotite clinopyroxene compositions using log‐ratio transformation, principal component analysis (PCA) and k‐means clustering, to better understand clinopyroxene compositional systematics in abyssal peridotites. We combine this analysis with open‐system melting models to investigate the potential sources of compositional variation. PCA shows that 84% of the variation in clinopyroxene compositions can be represented using only 2‐dimensional information. We use k‐means clustering to classify clinopyroxene compositions into four clusters. Clusters 1–3, representing 85% of the data, show progressive depletions in LREE/HREE, and are associated with decreases in Na2O in clinopyroxene, and general increases in Cr# of spinel. We interpret peridotites with clinopyroxene compositions from clusters 1–3 to represent residues of partial melt extraction. The degree of melt extraction increases from cluster 1 to 3, and exerts a primary control on compositional variations. The presence or absence of garnet‐field melting prior to spinel‐field melting and the retained melt fraction during partial melting exert secondary controls on clinopyroxene compositions. Cluster 4 clinopyroxenes, representing show less fractionated LREE/HREE with low‐HREE abundances, elevated Sr, and depleted signatures in their host peridotites. Clinopyroxene compositions in cluster 4 cannot be modeled by melt depletion alone. Instead, they are only reconstructed in our models where melt‐rock interaction, suggesting that peridotites with cluster 4 clinopyroxenes have experienced both of these processes. Clusters 1–4 are observed in most ridges, reflecting compositional heterogeneity on each ridge. This variability reflects variations in the degree of partial melting, amount of garnet‐field melting, retained melt fractions, and melt‐rock interaction.
Gravity‐Derived Antarctic Crustal Thickness Based on the Gauss‐FFT Method
Authors: Ji Fei , Wu Leyuan , Zhang Qiao
Published: August 2022

The information on crustal thickness in Antarctica can provide significant constraints on its crustal deformation and tectonic evolution. To generate reliable images of crustal features, we investigate the model of Moho depth and crustal thickness beneath Antarctica by applying the Bott‐Parker's formulas based on the Gauss‐fast Fourier transform method through a comprehensive analysis of gravity data, ice and sediment thicknesses and bedrock elevation, combined with seismic constraints. Tests with synthetic data indicate that the iterative inversion algorithm can yield a highly accurate Moho topography. Ultimately, inverted crustal thickness reveals a more detailed crustal image by clearly identifying more tectonic elements at different scales than previous results and correlates well with major tectonic provinces. Airy isostasy and flexural isostasy models are used to assess the crustal isostatic compensation. The distinctive negative isostatic anomalies are observed in the Transantarctic Mountains and the East Antarctic areas of the great escarpment in the Dronning Maud Land and Aurora and Wilkes Subglacial Basin, indicating that the low density of the uppermost mantle and lithospheric strength may play important roles in compensating for their elevations. Variations in crustal thickness in interior East Antarctica are analyzed; the thickened crust from Dronning Maud Land to the Gamburtsev Subglacial Mountains may be associated with the collision of continental blocks and is interpreted as the fossil sutures. We compare the relationship between the Moho and Curie interfaces and find that the uppermost mantle is magnetized in some areas of East Antarctica, which may indicate preserved Precambrian cratonic roots.
Stability of Aquatic Nitrogen Cycle Under Dramatic Changes of Water and Sediment Inflows to the Three Gorges Reservoir
Authors: Pang Lina , Sun Yanxin , Yue Yao , Liu Caiqiong , An Chenge , Yang Tiantian , Lu Xinhua , Xu Quanxi , Mei Jie , Liu Min , Zhang Xiaofeng
Published: August 2022

Stability of nitrogen cycle is a key indicator to aquatic health. In recent years, water and sediment inflows to the Three Gorges Reservoir (TGR) have changed significantly. To reveal the effects of such dramatic hydrological changes on aquatic nitrogen cycle, this paper at first analyzed the changing trends of water and suspended sediment discharges of TGR based on dynamic harmonic regression, and found that the intra‐year distribution of water flow was significantly homogenized between flood and dry seasons, with the seasonal variations narrowed by 43.5%–69.9% during 2007–2016, while sediment concentration sharply dropped (the non‐periodic term decreased by 1.48%–2.07%/month). Modified with the effects of sediment concentration variations on nitrification/denitrification rates, the proposed numerical model surprisingly showed that ammonia nitrogen and total nitrogen concentrations in TGR were insensitive to either water flow homogenization or sediment reduction, implying relative stability of microbial community related to nitrogen cycle, which is a positive sign for aquatic health. However, N2 emission varied more violently. The variation range of nitrogen gas (N2) emitted from TGR enlarged by 30% with the homogenization of water inflow from 2010 to 2016, while the annual total N2 emission decreased by 7% due to the reduction of sediment concentration, indicating quick response and strong adaption of the microbial N2 producing process to the environmental changes of TGR, which is beneficial for maintaining ecological functions related to nitrogen cycling. This work helps understanding nitrogen cycle of reservoirs experiencing dramatic changes in water and sediment inflows.
Jupiter's Low‐Altitude Auroral Zones: Fields, Particles, Plasma Waves, and Density Depletions
Authors: Sulaiman A. H. , Mauk B. H. , Szalay J. R. , Allegrini F. , Clark G. , Gladstone G. R. , Kotsiaros S. , Kurth W. S. , Bagenal F. , Bonfond B. , Connerney J. E. P. , Ebert R. W. , Elliott S. S. , Gershman D. J. , Hospodarsky G. B. , Hue V. , Lysak R. L. , Masters A. , Santolík O. , Saur J. , Bolton S. J.
Published: August 2022

The Juno spacecraft's polar orbits have enabled direct sampling of Jupiter's low‐altitude auroral field lines. While various data sets have identified unique features over Jupiter's main aurora, they are yet to be analyzed altogether to determine how they can be reconciled and fit into the bigger picture of Jupiter's auroral generation mechanisms. Jupiter's main aurora has been classified into distinct “zones”, based on repeatable signatures found in energetic electron and proton spectra. We combine fields, particles, and plasma wave data sets to analyze Zone‐I and Zone‐II, which are suggested to carry upward and downward field‐aligned currents, respectively. We find Zone‐I to have well‐defined boundaries across all data sets. H+ and/or H3+ cyclotron waves are commonly observed in Zone‐I in the presence of energetic upward H+ beams and downward energetic electron beams. Zone‐II, on the other hand, does not have a clear poleward boundary with the polar cap, and its signatures are more sporadic. Large‐amplitude solitary waves, which are reminiscent of those ubiquitous in Earth's downward current region, are a key feature of Zone‐II. Alfvénic fluctuations are most prominent in the diffuse aurora and are repeatedly found to diminish in Zone‐I and Zone‐II, likely due to dissipation, at higher altitudes, to energize auroral electrons. Finally, we identify significant electron density depletions, by up to 2 orders of magnitude, in Zone‐I, and discuss their important implications for the development of parallel potentials, Alfvénic dissipation, and radio wave generation.
An Auroral Signature of the Duskside Boundary of the Cusp
Authors: Feng Hui‐Ting , Han De‐Sheng , Teng Shang‐Chun , Shi Run , Su‐Zhou  , Yang Hui‐Gen , Qiu Hui‐Xuan , Zhang Y.‐L.
Published: August 2022

The cusp is a region in which the solar wind plasma can directly penetrate into the ionosphere. Most previous studies mainly focused on the low‐ and high‐latitude boundaries of the cusps, the identification of the dawnside and duskside boundaries of them appears to be questionable. The auroras are the ionospheric manifestations of solar‐terrestrial energy coupling. This paper presents a new approach to diagnose the duskside boundary of the cusp with the observation of a particular polar cap arc (PCA) located near the ∼1500 magnetic local time sector (15MLT‐PCA). Using measurements from Defense Meteorological Satellite Program satellite, we selected several 15MLT‐PCA examples where the satellite flew over different regions and analyze the particle characteristics. We identified the precipitating particles in dawnside and duskside regions next to 15MLT‐PCA are from the low latitude boundary layer/cusp and boundary plasma sheet/central plasma sheet respectively. The statistical result further confirms our findings. Therefore, we proposed that 15MLT‐PCA can be used as an identifiable optical signature of the duskside boundary of the cusp. This paper provides a valuable approach to identify the cusp boundaries, and the results are critical for understanding the generation mechanism of 15MLT‐PCA.
Solar Wind Energy Input: The Primary Control Factor of Magnetotail Reconnection Site
Authors: Nagai Tsugunobu , Shinohara Iku
Published: August 2022

In this paper, we examine the solar wind energy input (expressed by −Vx × Bs, where Vx is the x component of the solar wind velocity and Bs is the southward component of the interplanetary magnetic field IMF Bz) for an onset of magnetic reconnection in the near‐Earth magnetotail. There are 41 events in which in situ observations of magnetic reconnection were made by Geotail. Magnetic reconnection in the postmidnight (premidnight) sector of the plasma sheet occurred under strong (weak) solar wind energy input conditions. Furthermore, we study temporal variations in the solar wind energy input with two different approaches using ground magnetic field observations and proton injections at geosynchronous altitude. These two analyses confirmed the preference of the postmidnight sector for the onset of magnetic reconnection under the strong solar wind energy input conditions. It is also found that the medium and weak solar wind energy input may move the onset location to earlier magnetic local times. The onset location of magnetic reconnection in the near‐Earth magnetotail is controlled by the solar wind energy input through the global magnetospheric dynamics during the loading period.
Verification of Substorm Onset From Intruding Flow Channels With High‐Resolution SuperDARN Radar Flow Maps
Authors: Lyons Larry R. , Nishimura Yukitoshi , Liu Jiang , Bristow William A. , Zou Ying , Donovan Eric F.
Published: August 2022

Auroral observations were first to identify the substorm, and later used to propose that substorm onset is triggered in the inner plasma sheet (equatorward portion of the auroral oval) by an intrusion of low entropy plasma comprising plasma sheet flow channels. Longitudinal localization makes the intruding flow channels difficult to observe with spacecraft. However, they are detectable in the ionosphere via the broader, two‐dimensional coverage by radars. Line‐of‐sight radar flow measurements have provided considerable support for the onset proposal. Here we use two‐dimensional, ionospheric flow maps for further testing. Since these maps are derived without the smoothing from global fits typically used for global convection maps, their spatial resolution is significantly improved, allowing representation of localized spatial structures. These maps show channels of enhanced ionospheric flow intruding to the time and location of substorm onset. We also see evidence that these intruding flows enter the plasma sheet from the polar cap, and that azimuthal spread of the reduced entropy plasma in the inner plasma sheet contributes to azimuthal onset spreading after initial onset. Identified events with appropriate radar data remain limited, but we have found no exceptions to consistency with flow channel triggering. Thus, these analyses strongly support the proposal that substorm onset is due to the intrusion of new plasma to the onset region. The lower entropy of the new plasma likely changes the entropy distribution of inner plasma sheet, a change possibly important for the substorm onset instability seen via the growing waves that demarcate substorm auroral onset.
From Long‐ to Short‐Term Inter‐Plate Coupling at the Subducted Carnegie Ridge Crest, Offshore Central Ecuador
Authors: Collot J.‐Y. , Proust J.‐N. , Nocquet J.‐M. , Martillo C. , Michaud F. , Lebrun J.‐F. , Schenini L. , Popescu S. , Hernandez M.‐J. , Ratzov G.
Published: August 2022

We investigate the relationship between the long‐term (Quaternary) interplate coupling and the short‐term geodetically derived interseismic coupling at the Central Ecuador subduction zone. At this nonaccretionary margin, the Cabo Pasado shelf promontory and coastal area are associated with two inter‐plate geodetically locked patches. The deepest patch ruptured co‐seismically during the Mw7.8‐2016 Pedernales earthquake, while the shallowest underwent dominantly after‐slip. Marine geophysical and chronostratigraphic data allow reconstructing the Quaternary tectonic evolution of the shelf promontory and substantiating variation of the long‐term inter‐plate coupling that led to the geodetically locked patches. Prior to ∼1.8 Ma, the outer‐wedge inter‐plate coupling was strong enough to activate trench‐subparallel strike‐slip faults. Then, between ∼1.8 and 0.79 Ma, shortening and uplift affected the shelf promontory, implying a locally increased inter‐plate coupling. After a short, post‐0.79 Ma period of subsidence, shortening and uplift resumed denoting a high inter‐plate coupling that endured up to the present. The synchronicity of the structural evolution of the shelf promontory with the subduction chronology of two reliefs of the Carnegie Ridge crest suggests that the locked patches are caused by a geometrical resistance to subduction that propagates landward causing permanent deformation. In 2016, the deepest subducted relief localized stress accumulation and high seismic slip, while the shallowest relief, which is associated with a weakened outer‐wedge, prevented updip rupture propagation. Thus, at nonaccretionary margins, active outer‐wedge strike‐slip faults might be considered a proxy of near‐trench coupling, and subducted relief a cause of plate coupling but an obstacle to the tsunami genesis when the relief is shallow.
The Influence of Roughness on Experimental Fault Mechanical Behavior and Associated Microseismicity
Authors: Fryer Barnaby , Giorgetti Carolina , Passelègue François , Momeni Seyyedmaalek , Lecampion Brice , Violay Marie
Published: August 2022

Fault surfaces are rough at all scales, and this significantly affects fault‐slip behavior. However, roughness is only occasionally considered experimentally and then often in experiments imposing a low‐slip velocity, corresponding to the initiation stage of the earthquake cycle. Here, the effect of roughness on earthquake nucleation up to runaway slip is investigated through a series of dry load‐stepping biaxial experiments performed on bare rock surfaces with a variety of roughnesses. These laboratory faults reached slip velocities of at least 100 mm/s. Acoustic emissions were located during deformation on bare rock surfaces in a biaxial apparatus during load‐stepping experiments for the first time. Smooth surfaces showed more frequent slip instabilities accompanied by slip bursts and larger stress drops than rough faults. Smooth surfaces reached higher slip velocities and were less inclined to display velocity‐strengthening behavior. The recorded and localized acoustic emissions were characterized by a greater proportion of large‐magnitude events, and therefore likely a higher Gutenberg‐Richter bGR‐value, for smoother samples, while the cumulative seismic moment was similar for all roughnesses. These experiments shed light on how local microscopic heterogeneity associated with surface topography can influence the macroscopic stability of frictional interfaces and the associated microseismicity. They further provide a laboratory demonstration of roughness' ability to induce stress barriers, which can halt rupture, a phenomenon previously shown numerically.
Stacking of EAC Eddies Observed From Argo
Authors: Rykova Tatiana , Oke Peter R.
Published: August 2022

Using data from Argo floats, satellite altimetry, and satellite sea surface temperature (SST), we investigate the merging of two anti‐cyclonic eddies in the Tasman Sea. The eddies are of different size and different density. Once the distance between the eddies falls below a critical separation distance, water from the smaller, denser eddy is observed to flow around the larger, lighter eddy, sink to greater than 400 m depth, and slowly spiral toward the eddy‐center. The merging event is characterized by filaments around the eddy perimeter, evident in high‐resolution, satellite SST data. The merged eddy develops multiple well‐mixed layers, each almost 400 m thick, with large anomalies in temperature and salinity that penetrate to about 1,000 m depth. After the merging is complete, water from the lighter eddy is stacked on top of water from the denser eddy. Using a simple conceptual model, we show that the merged profiles can be simply explained by subduction of surface waters from the denser eddy, and mixing with subsurface waters from the lighter eddy. The stacked eddy has a distinct signature in TS‐space. Using this TS‐signature, together with altimetry for context, we identify over 20 other examples when Argo floats sample stacked eddies in the Tasman Sea. We speculate that merged eddies may be more common than previously thought, with implications for ocean productivity, underwater acoustics, and the transfer of energy across scales.
Roles of Drop Size Distribution and Turbulence in Autoconversion Based on Lagrangian Cloud Model Simulations
Authors: Oh D. , Noh Y.
Published: August 2022

The roles of the drop size distribution (DSD) and turbulence in the autoconversion rate A are investigated by analyzing Lagrangian cloud model (LCM) data for shallow cumulus clouds. The correlations of DSD and turbulence with other cloud parameters are estimated, and they are applied to parameterize their effects on A. A new parameterization of A based on this analysis is proposed: with , where is the cloud water mixing ratio, and are the number concentration and the volume mean radius of cloud droplets, is the dissipation rate, is the threshold value of , H is the Heaviside step function, and X, , and b are constants. Here, represents the effect of DSD via its correlation with and , while represents the effect of gravitational collisional growth for a given DSD and turbulence. The correlation between turbulence and DSD makes b larger than expected from turbulence‐induced collision enhancement only. The effects of DSD and turbulence and their correlations with and explain a wide range of exponent values of and in many existing parameterizations of A. The new parameterization is compared with the LCM data and applied to a bulk cloud model (BCM) while clarifying the difference between the cloud droplet mixing processes in the LCM and BCM. The importance of DSD and turbulence in raindrop formation in shallow cumulus clouds is shown by comparing the A results with and without these effects.
The Relation Between the Latitudinal Shifts of Midlatitude Diabatic Heating, Eddy Heat Flux, and the Eddy‐Driven Jet in CMIP6 Models
Authors: Lachmy Orli
Published: August 2022

The midlatitude storm tracks and eddy‐driven jet are predicted to shift poleward in response to anthropogenic climate change. Here the relation between the latitudes of the eddy‐driven jet and storm track and their responses to climate change in preindustrial and abrupt 4 × CO2 simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) are examined, focusing on the Southern Hemisphere summer. The eddy‐driven jet, Ferrel cell, midlatitude diabatic heating, and eddy heat flux all shift poleward in response to climate change, while the eddy‐driven jet latitude is positively correlated with the diabatic heating latitude and the Ferrel cell latitude, but is not significantly correlated with the eddy heat flux latitude, and is negatively correlated with the midlatitude diabatic heating strength. The roles of eddy heat flux and diabatic heating in the midlatitude circulation response to climate change are analyzed using the Kuo‐Eliassen equation. Each heating term induces a meridional circulation and an associated Coriolis force, which acts to change the vertical shear of the zonal mean zonal wind. It is found that in response to climate change, the heating due to eddy heat flux accelerates the vertical wind shear on the equatorward side of the jet, while the diabatic heating decelerates the vertical wind shear on the poleward side of the jet. The contributions of the heating terms to the momentum budget balance the contributions due to eddy momentum flux and surface friction, which act to shift the vertical shear poleward in response to climate change.
Examining the Role of the Land Surface on Convection Using High‐Resolution Model Forecasts Over the Southeastern United States
Authors: Henderson David S. , Otkin Jason A. , Mecikalski John R.
Published: August 2022

The influence of the Unified Noah and Noah‐MP land surface models (LSMs) on the evolution of cumulus clouds reaching convective initiation (CI) is assessed using infrared brightness temperatures (BT) from GOES‐16. Cloud properties from individual cloud objects are examined using output from high‐resolution (500 m horizontal grid spacing) model simulations. Cloud objects are tracked over time and related to observed clouds reaching CI to examine differences in cloud extent, longevity, and growth rate. The results demonstrate that differences in assumed surface properties can lead to large discrepancies in the net surface radiative budget, particularly in the sensible and latent heating components where differences exceed 40 W m−2. These differences lead to changes in the local mesoscale circulation patterns that are more pronounced near the edges of forested and grassland boundaries where lower‐level convergence is stronger. Higher sensible heating from the Noah‐MP LSM produced growth of CI clouds earlier and with increased longevity, which was closer to the timing and growth observed from GOES‐16. The increased cloud growth in the Noah‐MP experiment results from stronger and deeper updrafts, which lofts more cloud water into the upper levels of the troposphere. The weaker updrafts from the Noah LSM experiment results in shallower convection after CI is detected due to slower growth rates. The differences in cloud properties and growth are directly related to the land surfaces they develop above and point to the importance of accurately representing land properties and radiative characteristics when simulating convection in numerical weather prediction models.
Investigation of the Reaction of Schumann Resonances to Short Transient Geophysical Events Under the Influence of Atmospheric Electromagnetic Noise
Authors: Poklad Yu. V. , Ryakhovsky I. A. , Gavrilov B. G. , Ermak V. M. , Kozakova E. N. , Achkasov N. S.
Published: August 2022

The interference of electromagnetic signals from lightning discharges in the frequency range below 100 Hz is the source of a global electromagnetic phenomenon in the Earth's atmosphere known as the Schumann resonance (SR). Changes in the parameters of SR signals caused by geophysical disturbances make it possible to study the state and dynamics of the lower ionosphere. When calculating the SR parameters, there are problems associated with the impact of electromagnetic interference of natural and anthropogenic origin. The main natural sources of interference are signals associated with the radiation of nearby lightning discharges, as well as the influence of the Alfvén ionospheric resonator. The paper presents a new method for calculating the SR parameters, which makes it possible to find the spectra distorted by interference, mention above, and exclude them from further processing. The developed technique significantly increased the temporal resolution of the obtained data on the frequency and amplitude of the SR. Due to this, it became possible to study the influence of fast heliogeophysical disturbances (such as solar X‐ray flares) on the lower ionosphere and, as a consequence, on the parameters of the SR. An analysis of the experimental data made it possible to establish a linear dependence of the SR frequency on the logarithm of the X‐ray flux in the range up to 0.2 nm during a class X solar flare.
Unraveling the Deep‐Sea Sedimentary Record of Ice Sheet History
Authors: Cowan Ellen A.
Published: August 2022

Ice rafted debris (IRD) is a proxy used to interpret the deep‐sea sedimentary record of ice sheet history. McKay et al. (2022, https://doi.org/10.1029/2021PA004404) focused on methods used to reconstruct past iceberg presence around Antarctica using IRD from deep‐sea sediment cores and address the efficacy of the following three common methodologies of IRD quantification: counting clasts >2 mm in x‐radiographs; the sieved weight percent of the medium‐to‐coarse sand fraction (250 μm–2 mm); and volumetric estimates of the >125 μm sand fraction using laser particle size analysis. A high correlation occurred between IRD percentage determined by sieve analysis and visual clast counts using radiograph analysis. Although each method has pros and cons that are considered by the authors, the separation of coarse sand (>250 μm–2 mm) from fine‐grained sediment by sieving provided the cleanest signal. In addition, IRD grains can be used for paleoenvironment or provenance analyses providing more complete marine ice sheet paleorecords. This thorough analysis highlights a topic that has been previously overlooked and has become increasingly important in understanding the response of marine ice sheets to a warming atmosphere and ocean.
Comment on “Diffraction by a Flanged Parallel‐Plate Waveguide”
Authors: Honarbakhsh B.
Published: August 2022

It is shown that there is a better choice for solution of equations appeared in the above‐mentioned paper from the aspects of convergence and CPU time.
Quantifying the Cryptic Topography of the High Plains
Authors: Bogolub Kyren R. , Jones Craig H.
Published: August 2022

The origin of the presently high topography of the High Plains of the western United States has been a topic of considerable debate. We remove the directly quantifiable effects of thrust loading and post‐Early Cretaceous sedimentation to identify topography supported by subsurface means. We term this amount of unexplained topography cryptic topography. To determine the amount of topography that can be attributed to sedimentation, thrust loading, and the flexural response of the lithosphere, we estimate the thickness and density of the sedimentary rocks that overly the Dakota Formation from well logs. We then calculate the flexure that results from the emplacement of these rocks as well as the thrust load of the Rocky Mountains. We then subtract these effects from the present day Dakota horizon. The results of removing these effects indicate that between ∼1 and 1.5 km of topography at the western edge of the High Plains is cryptic and demands some change in the deeper crust or mantle since the deposition of the Dakota Formation.
Influence of zinc levels and Nrf2 expression in the clinical and pathological changes in patients with diabetic nephropathy
Authors: Nie Ping , Lou Yan , Bai Xue , Zhu Yuexin , Guo Qiaoyan , Luo Ping , Zhang Weiguang , Li Bing
Published: August 2022

Objective

We investigated the correlation between zinc levels and Nrf2 expression and potential effects on the clinicopathology of patients with diabetic nephropathy (DN).

Methods

We selected 30 patients with DN, diagnosed via renal biopsy at our hospital from March 2018 to November 2019, and enrolled 30 healthy individuals from a medical examination center as the control group. Patients with DN were divided into normal-zinc and low-zinc groups. We detected the levels of zinc, copper, and Nrf2 mRNA in their serum, and collected the clinical and pathological data of DN patients.

Results

Serum zinc level and Nrf2 mRNA expression were significantly decreased in patients with DN compared to those of healthy people (P < 0.05). Of the 30 patients, 16 had low zinc (53.3%) and 14 had normal zinc levels (46.7%). There was no significant difference in the blood Nrf2 mRNA expression between the two groups (P > 0.05). However, the expression of Nrf2 in the kidney tissue of the low-zinc group was significantly lower compared to the normal-zinc group (P < 0.05). Diastolic blood pressure and copper levels were significantly higher in the low-zinc group (P < 0.05). In contrast, body mass index, red blood cell count, Hb level, and the ratio of zinc to copper were significantly lower in the low-zinc group (P < 0.05). The pathological classifications of the low-zinc group were more severe (P < 0.05).

Conclusion

Patients with DN were more likely to have zinc deficiency and lower expression of Nrf2. Additionally, DN patients with zinc deficiency were prone to have more severe clinical and pathological manifestations.