Abstract
Determining the shear-velocity dependence of dry granular friction can provide insight into the controlling variables in a dry granular friction law. Some laboratories believe that the quality of this study is at the forefront of the discipline for the following reasons. Results suggest that granular friction is greatly affected by shear-velocity (v), but shear experiments over the large range of naturally occurring shear-velocities are lacking. Herein we examined the shear velocity dependence of dry friction for three granular materials, quartz sand, glass beads and fluorspar, across nine orders of magnitude of shear velocity (10−8–2 m/s). Within this range, granular friction exhibited four regimes, following a broad approximate “m” shape including two velocity-strengthening and two velocity-weakening regimes. We discuss the possible physical mechanisms of each regime. This shear velocity dependence appeared to be universal for all particle types, shapes, sizes, and for all normal stresses over the tested range. We also found that ultra-high frequency vibration as grain surfaces were scoured by micro-chips were formed by spalling at high shear velocities, creating ∼20 μm diameter impact pits on particle surfaces. This study provides laboratory laws of a friction-velocity (μ-v) model for granular materials.
Aircraft engine dust ingestion at global airports
Claire L. Ryder, Clément Bézier, Helen F. Dacre, Rory Clarkson, Vassilis Amiridis, Eleni Marinou, Emmanouil Proestakis, Zak Kipling, Angela Benedetti, Mark Parrington, Samuel Rémy, and Mark Vaughan
Nat. Hazards Earth Syst. Sci., 24, 2263–2284, https://doi.org/10.5194/nhess-24-2263-2024, 2024
Desert dust poses a hazard to aircraft via degradation of engine components. This has financial implications for the aviation industry and results in increased fuel burn with climate impacts. Here we quantify dust ingestion by aircraft engines at airports worldwide. We find Dubai and Delhi in summer are among the dustiest airports, where substantial engine degradation would occur after 1000 flights. Dust ingestion can be reduced by changing take-off times and the altitude of holding patterns.
An improved dynamic bidirectional coupled hydrologic–hydrodynamic model for efficient flood inundation prediction
Yanxia Shen, Zhenduo Zhu, Qi Zhou, and Chunbo Jiang
Nat. Hazards Earth Syst. Sci., 24, 2315–2330, https://doi.org/10.5194/nhess-24-2315-2024, 2024
We present an improved Multigrid Dynamical Bidirectional Coupled hydrologic–hydrodynamic Model (IM-DBCM) with two major improvements: (1) automated non-uniform mesh generation based on the D-infinity algorithm was implemented to identify flood-prone areas where high-resolution inundation conditions are needed, and (2) ghost cells and bilinear interpolation were implemented to improve numerical accuracy in interpolating variables between the coarse and fine grids. The improved model was reliable.
Tsunami hazard assessment in the South China Sea based on geodetic locking of the Manila subduction zone
Guangsheng Zhao and Xiaojing Niu
Nat. Hazards Earth Syst. Sci., 24, 2303–2313, https://doi.org/10.5194/nhess-24-2303-2024, 2024
The purpose of this study is to estimate the spatial distribution of the tsunami hazard in the South China Sea from the Manila subduction zone. The plate motion data are used to invert the degree of locking on the fault plane. The degree of locking is used to estimate the maximum possible magnitude of earthquakes and describe the slip distribution. A spatial distribution map of the 1000-year return period tsunami wave height in the South China Sea was obtained by tsunami hazard assessment.
Modeling Seismic Hazard and Landslide Potentials in Northwestern Yunnan, China: Exploring Complex Fault Systems with multi-segment rupturing in a Block Rotational Tectonic Zone
Jia Cheng, Chong Xu, Xiwei Xu, Shimin Zhang, and Pengyu Zhu
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-96,2024
Preprint under review for NHESS (discussion: open, 3 comments)
The Northwestern Yunnan Region (NWYR), with a complex network of active faults, presents significant seismic hazards such as multi-segment ruptures and landslides. This article introduces a new seismic hazard model, which integrates fault slip parameters to assess the risks associated with multi-segment ruptures. The results reveal the intricate relationship between these ruptures and the regional small block rotation induced by regional low-crustal flow and gravitational collapse.
Abstract
The ground-based, high-frequency radars of the Super Dual Auroral Radar Network (SuperDARN) observe backscatter from ionospheric field-aligned plasma irregularities and features on the Earth's surface out to ranges of several thousand kilometers via over-the-horizon propagation of transmitted radio waves. Interferometric techniques can be applied to the received signals at the primary and secondary antenna arrays to measure the vertical angle of arrival, or elevation angle, for more accurate geolocation of SuperDARN observations. However, the calibration of SuperDARN interferometer measurements remains challenging for several reasons, including a 2π phase ambiguity when solving for the time delay correction factor needed to account for differences in the electrical path lengths between signals received at the two antenna arrays. We present a new technique using multi-frequency ionospheric and ground backscatter observations for the calibration of SuperDARN interferometer data, and demonstrate its application to both historical and recent data.
Abstract
High energy resolution DEMETER satellite observations from the Instrument for the Detection of Particle (IDP) are analyzed during an electromagnetic ion cyclotron (EMIC)-induced electron precipitation event. Analysis of an Interval Pulsation with Diminishing Periods (IPDP)-type EMIC wave event, using combined satellite observations to correct for incident proton contamination, detected an energy precipitation spectrum ranging from ∼150 keV to ∼1.5 MeV. While inconsistent with many theoretical predictions of >1 MeV EMIC-induced electron precipitation, the finding is consistent with an increasing number of experimentally observed events detected using lower resolution integral channel measurements on the POES, FIREBIRD, and ELFIN satellites. Revised and improved DEMETER differential energy fluxes, after correction for incident proton contamination shows that they agree to within 40% in peak flux magnitude, and 85 keV (within 40%) for the energy at which the peak occurred as calculated from POES integral channel electron precipitation measurements. This work shows that a subset of EMIC waves found close to the plasmapause, that is, IPDP-type rising tone events, can produce electron precipitation with peak energies substantially below 1 MeV. The rising tone features of IPDP EMIC waves, along with the association with the high cold plasma density regime, and the rapidly varying electron density gradients of the plasmapause may be an important factor in the generation of such low energy precipitation, co-incident with a high energy tail. Our work highlights the importance of undertaking proton contamination correction when using the high-resolution DEMETER particle measurements to investigate EMIC-driven electron precipitation.
Abstract
The present study provides an evidence for the generation of harmonics of magnetosonic waves in the Martian magnetosheath region. The wave signatures are manifested in the magnetic field measurements recorded by the fluxgate magnetometer instrument onboard the Mars Atmosphere and Volatile Evolution missioN (MAVEN) spacecraft in the dawn sector around 5–10 LT at an altitude of 4,000–6,000 kms. The wave that is observed continuously from 19.1 to 20.7 UT below the proton cyclotron frequency (f
ci
≈ 46 mHz) is identified as fundamental mode of the magnetosonic wave. Whereas harmonics of the magnetosonic wave are observed during 19.7–20.3 UT at frequencies that are multiple of f
ci
. The ambient solar wind proton density and plasma flow velocity are found to vary with a fundamental mode frequency of 46 mHz. It is noticed that the fundamental mode is mainly associated with the left-hand (LH), and higher frequency harmonics are associated with the right-hand (RH) circular polarizations. A clear difference in the polarization and ellipticity is noticed during the time of occurrence of harmonics. The magnetosonic wave harmonics are found to propagate in the quasi-perpendicular directions to the ambient magnetic field. The results of linear theory and Particle-In-Cell simulation performed here are in agreement with the observations. The present study provides a conclusive evidence for the occurrence of harmonics of magnetosonic wave in the close vicinity of the magnetosheath region of the unmagnetized planet Mars.
Abstract
Solar eclipse traveled across South China in the afternoon on 21 June 2020. Five ionosondes located from mid-to low-latitudes and on both north and south of the eclipse path were applied to investigate the ionospheric responses. Both the zonal and meridional ranges of the observation region have exceeded 1,000 km. All the five ionosondes had observed the Intermediate Descending Layers (IDLs) simultaneously just after the eclipse maximum and this is a very small probability event. During the solar eclipse, the multi-hop echoes above the Es, the rising Es to 150 km altitude, the plasma flux from above F2-layer were also observed and analyzed. The descending trend of the IDLs and the peak height of F2-layer (h
m
F2) shows great consistency, indicating the close relationship between the eclipse induced plasma flux and the IDLs. The traces of gravity waves were also found in the IDLs and F-layer. The plasma flux may carry the ions to valley region and the eclipse produced gravity waves were responsible for the formation of the IDLs.
RoGeR v3.0.5 – a process-based hydrological toolbox model in Python
Robin Schwemmle, Hannes Leistert, Andreas Steinbrich, and Markus Weiler
Geosci. Model Dev., 17, 5249–5262, https://doi.org/10.5194/gmd-17-5249-2024, 2024
The new process-based hydrological toolbox model, RoGeR (https://roger.readthedocs.io/), can be used to estimate the components of the hydrological cycle and the related travel times of pollutants through parts of the hydrological cycle. These estimations may contribute to effective water resources management. This paper presents the toolbox concept and provides a simple example of providing estimations to water resources management.
Abstract
The Millennium Eruption of Changbaishan Volcano is heralded as one of the largest explosive eruptions in the Late Holocene and produced huge quantities of tephra. The petrogeochemical method estimates that the Millennium Eruption emitted up to 45 Tg of sulfur into the atmosphere—more than in the Tambora eruption in 1815 CE, which caused “a year without a summer” across the Northern Hemisphere in 1816 CE. Despite such massive emissions, evidence for this eruption's climate impact in East Asia remains elusive. To explain this contradiction, this study used 67 high-resolution tree-ring-width records from the Northern Hemisphere spanning the past two millennia, complemented by volcanic sensitivity experiments conducted with the Community Earth System Model. Results reveal a prevailing decreasing/negative trend in the proxy records during the potential eruption period, with 945 CE marking the most notable negative anomaly, suggesting that the Millennium Eruption likely occurred in 945 CE rather than 946 CE. Sensitivity experiments, corroborated by proxy records, demonstrate that the Millennium Eruption induced substantial negative temperature anomalies at middle and high latitudes, alongside an increase in Meiyu-Baiu-Changma precipitation in the middle and lower reaches of the Yangtze River and southwestern Japan and a decrease in precipitation in India, northern China, and the South China Sea in the first post-eruption year. This study offers a novel perspective on the climate impact of the Millennium Eruption, reconciling previous discrepancies regarding its climate impact.
Abstract
The timing and duration of volatile generation from crystallizing magma reservoirs and fluid release across the magmatic-hydrothermal interface depend on complex coupled interactions controlled by non-linear, dynamic properties of magmas, rocks and fluids. Understanding these mechanisms is essential to explain the rare formation of economic porphyry copper deposits. For this study, we further developed a coupled numerical model that can simultaneously resolve magma and hydrothermal flow by introducing a description of fluid transport within the magma reservoir and volatile release to the host rock. Our simulations use realistic magma properties derived from published experimental and modeling studies and cover different magma compositions and water contents. We show that magma convection at melt-dominated states leads to homogenization, which delays fluid release and promotes a rapid evolution toward a mush state. The onset of magmatic volatile release can be near-explosive with a tube-flow outburst event lasting <100 years for high initial water contents of >3.5 wt% H2O that could result in the formation of hydrothermal breccias and vein stockworks or trigger eruptions. This event can be followed by sustained fluid release at moderate rates by volatile flushing caused by magma convection. Subsequent fluid release from concentric tube rings by radial cooling of non-convecting magma mush with a volume of ∼100 km3 at ∼5 km depth is limited to remaining water contents of ∼3.1 wt% H2O and lasts 50–100 kyr. Ore formation from hydrous magmas may thus involve distinct phases of volatile release.
Abstract
The standard rate-and-state friction (RSF) has extensively captured frictional behaviors, but it fails to explain the velocity dependence of frictional stability transition and widespread slow-slip events (SSEs) in experiments and nature adequately. An alternative microphysical Chen-Niemeijer-Spiers (CNS) model can well describe the velocity dependence of frictional behaviors of granular gouges. Using the original CNS model, standard RSF parameters can be quantified microphysically. However, some micro-parameters are not easy to estimate quantitatively, making it difficult to extrapolate to natural and experimental conditions. Here, we simplify the microphysically-derived RSF parameters including direct effect a, evolution effect b, and critical slip distance D
c
, as well as equivalent values (a
eq, b
eq, and D
eq). The simplified friction parameters directly illustrate their velocity dependence, namely the essentially constant a, a
eq, and D
c
, negatively velocity-dependent b and b
eq, as well as varying D
eq for different laws. They are roughly consistent with experimental results in various fault gouges. A modified CNS model is further derived from the original CNS model, establishing a direct link between the standard RSF and CNS models. The modified CNS model exhibits virtually identical frictional behaviors to the original CNS, but differs from the standard RSF at large velocity perturbations. Moreover, the linearized stability analysis indicates that the critical stiffness for the modified CNS model is velocity-dependent. Compared with the standard RSF, the modified CNS model not only explains the velocity dependence of frictional stability transition, but also exhibits a more gradual transition for SSEs with a broader range of stiffness ratios.
Abstract
The firn layer covers 98% of Antarctica's ice sheets, protecting underlying glacial ice from the external environment. Accurate measurement of firn properties is essential for assessing cryosphere mass balance and climate change impacts. Characterizing firn structure through core sampling is expensive and logistically challenging. Seismic surveys, which translate seismic velocities into firn densities, offer an efficient alternative. This study employs Distributed Acoustic Sensing technology to transform an existing fiber-optic cable near the South Pole into a multichannel, low-maintenance, continuously interrogated seismic array. The data resolve 16 seismic wave propagation modes at frequencies up to 100 Hz that constrain P and S wave velocities as functions of depth. Using co-located geophones for ambient noise interferometry, we resolve very weak radial anisotropy. Leveraging nearby SPICEcore firn density data, we find prior empirical density-velocity relationships underestimate firn air content by over 15%. We present a new empirical relationship for the South Pole region.
Estimation of biogenic volatile organic compound (BVOC) emissions in forest ecosystems using drone-based lidar, photogrammetry, and image recognition technologies
Xianzhong Duan, Ming Chang, Guotong Wu, Suping Situ, Shengjie Zhu, Qi Zhang, Yibo Huangfu, Weiwen Wang, Weihua Chen, Bin Yuan, and Xuemei Wang
Atmos. Meas. Tech., 17, 4065–4079, https://doi.org/10.5194/amt-17-4065-2024, 2024
Accurately estimating biogenic volatile organic compound (BVOC) emissions in forest ecosystems has been challenging. This research presents a framework that utilizes drone-based lidar, photogrammetry, and image recognition technologies to identify plant species and estimate BVOC emissions. The largest cumulative isoprene emissions were found in the Myrtaceae family, while those of monoterpenes were from the Rubiaceae family.
Abstract
Large volcanic eruptions are known to influence the climate through a variety of mechanisms including aerosol-forced cooling and warming via emitted CO2. The January 2022 Hunga shallow underwater eruption caused an increase in stratospheric water vapor, and demonstrated how the associated positive radiative forcing can be an important component of an eruption's climate forcing. We present interactive stratospheric aerosol model simulations of super-volcanic eruptions with a range of SO2 emissions that can produce climate warming through feedback effects produced by a large igneous province (or “flood basalt”) mid-latitude super-eruption using Goddard Earth Observing System Chemistry Climate Model climate model simulations. The model experiments suggest total SO2 emissions ≳4,000 Tg/4 Gt generate a multi-year period of sustained aerosol absorptive local-heating of the upper troposphere and lower stratosphere and hence produce net climate warming after strong initial cooling. The eruptions produce stratospheric water vapor increases of factors of 8–600. The initiation of these feedbacks within the simulations suggest they could occur for individual stratovolcano eruptions of the scale of the Toba or Tambora eruptions. We note the sensitivity of our results to volcanic sulfate aerosol microphysics and model chemistry.
Abstract
The cloud classification algorithm widely used in the International Satellite Cloud Climatology Project (ISCCP) tends to underestimate low clouds over the Tibetan Plateau (TP), often mistaking water clouds for high-level clouds. To address this issue, we propose a new algorithm based on cloud-top temperature and optical thickness, which we apply to TP using Advanced Himawari Imager (AHI) geostationary satellite data. Compared with Clouds and the Earth's Radiant Energy System cloud-type products and ISCCP results obtained from AHI data, this new algorithm markedly improved low-cloud detection accuracy and better aligned with cloud phase results. Validation with lidar cloud-type products further confirmed the superiority of this new algorithm. Diurnal cloud variations over the TP show morning dominance shifting to afternoon high clouds and evening mid-level clouds. Winter is dominated by high clouds, summer by mid-level clouds, spring by daytime low clouds and nighttime high clouds, and autumn by low and mid-level clouds.
Bayesian cloud-top phase determination for Meteosat Second Generation
Johanna Mayer, Luca Bugliaro, Bernhard Mayer, Dennis Piontek, and Christiane Voigt
Atmos. Meas. Tech., 17, 4015–4039, https://doi.org/10.5194/amt-17-4015-2024, 2024
ProPS (PRObabilistic cloud top Phase retrieval for SEVIRI) is a method to detect clouds and their thermodynamic phase with a geostationary satellite, distinguishing between clear sky and ice, mixed-phase, supercooled and warm liquid clouds. It uses a Bayesian approach based on the lidar–radar product DARDAR. The method allows studying cloud phases, especially mixed-phase and supercooled clouds, rarely observed from geostationary satellites. This can be used for comparison with climate models.
Regional validation of the solar irradiance tool SolaRes in clear-sky conditions, with a focus on the aerosol module
Thierry Elias, Nicolas Ferlay, Gabriel Chesnoiu, Isabelle Chiapello, and Mustapha Moulana
Atmos. Meas. Tech., 17, 4041–4063, https://doi.org/10.5194/amt-17-4041-2024, 2024
In the solar energy application field, it is key to simulate solar resources anywhere on the globe. We conceived the Solar Resource estimate (SolaRes) tool to provide precise and accurate estimates of solar resources for any solar plant technology. We present the validation of SolaRes by comparing estimates with measurements made on two ground-based platforms in northern France for 2 years at 1 min resolution. Validation is done in clear-sky conditions where aerosols are the main factors.
Low-frequency solar radio type II bursts and their association with space weather events during the ascending phase of solar cycle 25
Theogene Ndacyayisenga, Jean Uwamahoro, Jean Claude Uwamahoro, Daniel Izuikedinachi Okoh, Kantepalli Sasikumar Raja, Akeem Babatunde Rabiu, Christian Kwisanga, and Christian Monstein
Ann. Geophys., 42, 313–329, https://doi.org/10.5194/angeo-42-313-2024, 2024
This article reports the first observations of 32 type II bursts in cycle 25 from May 2021 to December 2022. The impacts of space weather on ionospheric total electron content (TEC) enhancement, as measured by the rate of change of TEC index (ROTI), are also studied. According to the current analysis, 19 of 32 type II bursts are connected with imminent space weather occurrences, such as radio blackouts and polar cap absorption events, indicating a high likelihood of space weather disturbance.
