SummaryA high-precision and high-resolution vertical velocity for the Chinese mainland is obtained by integrating precise leveling and GNSS data, using a Helmert joint adjustment method. The results show that the surface vertical rates range between -3.0 and 3.9 mm/yr with continuous deformation in most areas, except the obvious subsidence at the rates of -15.0 to -94.2 mm/yr induced by groundwater exploitation in the North China Plain. Particularly, the central and southern Tibet, Tien Shan, Alashan, Ordos, eastern Cathaysia, and Northeast China uplift at the rates of 0.5 – 3.9 mm/yr; the southeastern Tibetan Plateau, Sichuan basin, and Yangtze block are dominated by surface subsidence at the rates of -3.3 to -0.5 mm/yr. Furthermore, the vertical rates vary little between the eastern and western regions of the Chinese mainland despite their pronounced differences in horizontal deformations. The effects of gravity isostasy and non-tectonic factors, including the environmental mass loads, Glacier Isostatic Adjustment (GIA), poroelastic expansion/compression, and mining operations have partially contributed to the vertical deformation of the Chinese mainland. Overall, this velocity reflects the complicated deformation features induced by the multiple geodynamic processes of the Chinese mainland. These geodynamic processes include isostasy, orogenic processes, and geothermal anomalies associated with slab subduction/plate collision.
SummaryThe gravity-geologic method (GGM) is an approach that utilizes marine gravity anomalies and shipborne bathymetric data to invert seafloor topography by resolving short-wavelength gravity anomalies through the Bouguer plate approximation. Such an approximation ignores the nonlinear effects caused by surrounding seafloor topographical undulations that actually exist in short-wavelength gravity anomalies, and thus leaving the space for further modification of GGM. This study thoroughly derives the relationship between seafloor topography and gravity anomaly (GA), as well as the formula of GGM. Then, we propose a self-adaptive method to improve the accuracy of the inversion significantly: the enhanced gravity-geologic method (EGGM). The method employs the equivalent mass line method to approximate the nonlinear gravitational effects of the surrounding seafloor topography to correct the short-wavelength gravity anomalies. By introducing two optimal density contrast parameters, EGGM has been designed to effectively integrate the combined effects of various nonlinear factors to a certain extent. The accuracy of the seafloor topography models, produced with a spatial resolution of 1'×1', was evaluated over the study area (132 °E-136 °E, 36 °N-40 °N) located in the Sea of Japan. The results indicate that the accuracy of EGGM has a relative improvement of 13.73% compared to that of GGM in the overall study area, while the accuracy of both models is higher than that of the SIO_unadjusted model. The study further investigated the feasibility and stability of EGGM by examining the accuracy of both GGM and EGGM in various water depth ranges and areas with diverse terrain characteristics.
SummaryWe present a new 3-D radially anisotropic seismic velocity model EARA2024 of the crust and mantle beneath East Asia and the northwestern Pacific using adjoint full-waveform inversion tomography. We construct the EARA2024 model by iteratively minimizing the waveform similarity misfit between the synthetic and observed waveforms from 142 earthquakes recorded by about 2,000 broadband stations in East Asia. Compared to previous studies, this new model renders significantly improved images of the subducted oceanic plate in the upper mantle, mantle transition zone, and uppermost lower mantle along the Kuril, Japan, Izu-Bonin, and Ryukyu Trenches. Complex slab deformation and break-offs are observed at different depths. Moreover, our model provides new insights into the origins of intraplate volcanoes in East Asia, including the Changbaishan, Datong-Fengzhen, Tengchong, and Hainan volcanic fields.
The first seven months of 2024 have been so eventful, it's easy to forget that the year started off with a magnitude 7.5 earthquake centered beneath Japan's Noto Peninsula on New Year's Day. The earthquake killed more than 280 people and damaged more than 83,000 homes.
Dynamical Madden–Julian Oscillation forecasts using an ensemble subseasonal-to-seasonal forecast system of the IAP-CAS model
Yangke Liu, Qing Bao, Bian He, Xiaofei Wu, Jing Yang, Yimin Liu, Guoxiong Wu, Tao Zhu, Siyuan Zhou, Yao Tang, Ankang Qu, Yalan Fan, Anling Liu, Dandan Chen, Zhaoming Luo, Xing Hu, and Tongwen Wu
Geosci. Model Dev., 17, 6249–6275, https://doi.org/10.5194/gmd-17-6249-2024, 2024
We give an overview of the Institute of Atmospheric Physics–Chinese Academy of Sciences subseasonal-to-seasonal ensemble forecasting system and Madden–Julian Oscillation forecast evaluation of the system. Compared to other S2S models, the IAP-CAS model has its benefits but also biases, i.e., underdispersive ensemble, overestimated amplitude, and faster propagation speed when forecasting MJO. We provide a reason for these biases and prospects for further improvement of this system in the future.
Abstract
The 2024 Mw 7.5 Noto Peninsula, Japan, earthquake was initiated within the source region of intense swarm activity. To reveal the mainshock early process, we relocated the earthquake hypocenters and found that many key phenomena, including the mainshock initiation, foreshocks, swarm earthquakes, and deep aseismic slip, occurred at parts of a previously unrecognized fault in intricate fault network. This fault is subparallel (several kilometers deeper) to a known active fault, and the mainshock initiation and foreshocks occurred at the front of a 2-year westward swarm migration. The initiation location coincides with the destination of the upward migration of a deeper earthquake cluster via several smaller faults. Fluid supply, small earthquakes, and aseismic slip on the fault likely triggered the mainshock, leading to the first major rupture at the western region, propagating further to the west and east sides, resulting in an Mw7.5 event, exceeding 100 km in length.
Abstract
As a practical reflection of the opportunity window of Madden-Julian Oscillation (MJO), there are intermittent periods of relatively high forecasting skills, namely the forecast skill windows. Robust forecast skill windows are identified based on the subseasonal-seasonal reforecast database, during which the majority of models show high forecast skills. A total of 15 MJO forecast skill windows during 1993–2020 have been identified. Most of the forecast skill windows are closely associated with active MJO events with high amplitude. Whether a high-skill forecast window appears significantly depends on the magnitude of MJO intensity during the same period. The maintenance of active strong MJO events is potentially related with the warmer surface sea temperature anomalies in the western Pacific. Further research into such processes may unveil the MJO development mechanism and improve the MJO forecast skill.
Partition between supercooled liquid droplets and ice crystals in mixed-phase clouds based on airborne in situ observations
Flor Vanessa Maciel, Minghui Diao, and Ching An Yang
Atmos. Meas. Tech., 17, 4843–4861, https://doi.org/10.5194/amt-17-4843-2024, 2024
The partition between supercooled liquid water and ice crystals in mixed-phase clouds is investigated using aircraft-based in situ observations over the Southern Ocean. A novel method is developed to define four phases of mixed-phase clouds. Relationships between cloud macrophysical and microphysical properties are quantified. Effects of aerosols and thermodynamic and dynamical conditions on ice nucleation and phase partitioning are examined.
Atmospheric H2 observations from the NOAA Cooperative Global Air Sampling Network
Gabrielle Pétron, Andrew M. Crotwell, John Mund, Molly Crotwell, Thomas Mefford, Kirk Thoning, Bradley Hall, Duane Kitzis, Monica Madronich, Eric Moglia, Donald Neff, Sonja Wolter, Armin Jordan, Paul Krummel, Ray Langenfelds, and John Patterson
Atmos. Meas. Tech., 17, 4803–4823, https://doi.org/10.5194/amt-17-4803-2024, 2024
Hydrogen (H2) is a gas in trace amounts in the Earth’s atmosphere with indirect impacts on climate and air quality. Renewed interest in H2 as a low- or zero-carbon source of energy may lead to increased production, uses, and supply chain emissions. NOAA measurements of weekly air samples collected between 2009 and 2021 at over 50 sites in mostly remote locations are now available, and they complement other datasets to study the H2 global budget.
Simulation and detection efficiency analysis for measurements of polar mesospheric clouds using a spaceborne wide-field-of-view ultraviolet imager
Ke Ren, Haiyang Gao, Shuqi Niu, Shaoyang Sun, Leilei Kou, Yanqing Xie, Liguo Zhang, and Lingbing Bu
Atmos. Meas. Tech., 17, 4825–4842, https://doi.org/10.5194/amt-17-4825-2024, 2024
Ultraviolet imaging technology has significantly advanced the research and development of polar mesospheric clouds (PMCs). In this study, we proposed the wide-field-of-view ultraviolet imager (WFUI) and built a forward model to evaluate the detection capability and efficiency. The results demonstrate that the WFUI performs well in PMC detection and has high detection efficiency. The relationship between ice water content and detection efficiency follows an exponential function distribution.
A research team focused on the extreme rainfall event of "21·7" in Henan in 2021. By analyzing anomalous physical characteristics and understanding multi-model forecast biases, they significantly enhanced the accuracy of precipitation intensity forecasts. This improvement was achieved by incorporating optimization metrics and constraints better suited to the physical and data characteristics of precipitation into the neural network loss function.
Abstract
This study analyzes hydrometeor evolution during rapid intensification (RI) and tropical cyclone (TC) intensity dependence using satellite data. Previous studies have suggested ice cloud water or non-convective precipitation as a predictor of RI from different perspectives. However, few studies have focused on the impact of TC intensity or comprehensive comparisons to identify better indicators. During RI, hydrometeor contents in weak TCs increase over the entire region, whereas they increase mainly in the inner-core region and decrease in advance in the outer-core region for strong TCs. Hydrometeor contents in the inner-core are higher in RI than in slow intensification, and their maxima location is related to TC intensity and intensification rate. Cloud water path (CWP) in the inner-core region is most correlated with the intensification rate, especially in weak TCs. Therefore, the CWP can serve as a predictor of RI and can be applied to all TC intensities.
The Anthropocene is a proposed geological epoch whereby humans are deemed to be the primary drivers of ecological and environmental change, through activities that lead to environmental degradation. This theory that human activity poses more of a threat to the natural environment than natural processes that have been in place for millions of years, highlights the significance of the human impact.
Abstract
In this study, prominent dust source areas are identified along with their plume extent using high temporal frequency satellite observations. Hourly dust plume observations of the Dust Belt from geostationary-orbit satellites are analyzed for the 2017-12–2022-11 period. To identify dust source areas and their extents, we back-track plumes to their source, assessing source areas in terms of emission frequency, contribution, and plume extent patterns. This method advances over traditional source allocation techniques that rely on polar-orbiting satellites based on a few daily passes and meteorological wind fields for backtracking. Our findings indicate that Boreal summer is the most intense season for most sources, except in the Southern Sahara, which experiences winterly winds. Our analysis also reveals significant contributions from regions within the Sahara that experience expansive but infrequent dust storms, highlighting the importance of considering both frequency and magnitude in understanding dust emissions.
Abstract
Radio-echo sounding (RES) shows large-scale englacial stratigraphic folds are ubiquitous in Greenland's ice sheet. However, there is no consensus yet on how these folds form. Here, we use the full-Stokes code Underworld2 to simulate ice movements in three-dimensional convergent flow, mainly considering ice anisotropy due to a crystallographic preferred orientation, vertical viscosity and density gradients in ice layers, and bedrock topography. Our simulated folds show complex patterns and are classified into: large-scale folds (>100 m amplitude), small-scale folds (<<100 m) and basal-shear folds. The amplitudes of large-scale folds tend to be at their maximum in the middle of the ice column or just below, in accordance with observations in RES data. We conclude that ice anisotropy amplifies the perturbations in ice layers (mainly due to bedrock topography) into large-scale folds during flow. Density differences between the warm deep ice and cold ice above may enhance fold amplification.
Abstract
Ion-acoustic waves (IAWs) commonly occur near interplanetary (IP) shocks. These waves are important because of their potential role in the dissipation required for collisionless shocks to exist. We study IAW occurrence statistically at different heliocentric distances using Solar Orbiter to identify the processes responsible for IAW generation near IP shocks. We show that close to IP shocks the occurrence rate of IAW increases and peaks at the ramp. In the upstream region, the IAW activity is highly variable among different shocks and increases with decreasing distance from the Sun. We show that the observed currents near IP shocks are insufficient to reach the threshold for the current-driven instability. We argue that two-stream proton distributions and suprathermal electrons are likely sources of the waves.
Abstract
The Central Asian Orogenic Belt (CAOB) was formed by the aggregation and collage of numerous Paleozoic subduction-accretion assemblages and Precambrian microcontinental blocks. However, the tectonic nature of the southeastern CAOB remains controversial, which complicates the reconstruction of the Paleo-Asian Ocean. To address this issue, a deep seismic reflection survey was initiated across the southeastern CAOB and reveals broad gentle sub-horizontal reflectors in the middle-lower crust and a relatively transparent zone in the upper crust. Combining with the Precambrian geological outcrops and other geophysical features, we support a microcontinental block, the Xilinhot Block, existed in the Paleo-Asian domain. Thus, the Paleo-Asian Ocean was separated into two branches that underwent north-dipping and double-dipping oceanic plate subduction, respectively, to form the Hegenshan-Heihe and Solonker sutures. Multiple relics beneath Hegenshan-Heihe Suture indicate that multiple sets of unidirectional oceanic subduction-accretion and magmatism were important mechanisms of continental growth.
Deformation monitoring plays a vital role in geological disaster management, transportation, and engineering maintenance. While Global Navigation Satellite System (GNSS) relative positioning has been the standard for such tasks, its precision often falters in long strip regions due to inconsistent distances between monitoring stations and base stations.
An international study led by the Institute of Natural Resources and Agrobiology of Seville (IRNAS-CSIC), of the Spanish National Research Council (CISC), has shown that as the number of global change factors increases, terrestrial ecosystems become more sensitive to the impacts of global change.
Abstract
Abduallah et al. (2024b, https://doi.org/10.1029/2023sw003824) proposed a novel approach using a deep neural network model, which includes a graph neural network and a bidirectional LSTM layer, named SYMHnet, to forecast the SYM-H index one and 2 hr in advance. Additionally, the network also provides an uncertainty quantification of the predictions. While the approach is innovative, there are some areas where the model's design and implementation may not align with best practices in uncertainty quantification and predictive modeling. We focus on discrepancies in the input and output of the model, which can limit the applicability in real-world forecasting scenarios. This comment aims to clarify these issues, offering detailed insights into how such discrepancies could compromise the model's interpretability and reliability, thereby contributing to the advancement of predictive modeling in space weather research.
