GRL

Understanding the nature of mixing between cloudy air and its surroundings is an important and yet, open question. In this research, we use high-resolution (10 m) bin-microphysics Large Eddy Simulation of a cumulus cloud, together with a Lagrangian passive tracer tracking method, to study mixing. We analyze the passive tracers as a function of their trajectories and the thermodynamic conditions they undergo inside and outside the cloud. Three main mixing regimes (core, periphery, and skin) are identified, each determining a subset of tracers with similar trajectories. These mixing regimes can be observed throughout the cloud's lifetime and they provide evidence for the presence of an undiluted core in shallow cumulus clouds. At the dissipation stage, a fourth regime is identified: cloud-top entrainment followed by downdrafts.

This study presents the observation and evaluation of a meteotsunami in the Indian Ocean triggered by the Hunga-Tonga volcanic eruption. The event was detected through tide gauges and bottom-pressure recordings across the Indian Ocean, with an amplitude of 10–15 cm, lasting for a few days. A numerical model was used to understand the ocean's response to meteotsunami and evaluate the dynamics behind it. The model results show that the sea-level oscillations result from the ocean waves generated by a propagating Lamb wave. In addition to interaction with bathymetry, refracted and reflected waves also determine the sea-level variability. Our analysis shows that bathymetric slope plays a vital role in near-shore processes. The spectral and spatial characteristics of the meteotsunami were reminiscent of seismic tsunamis. Our research on this rare event elucidates the unresolved issues and eventually leads to designing a blueprint for future observation and modeling of meteotsunamis and seismic tsunamis.

Land surface-atmosphere coupling and soil moisture memory are shown to combine into a distinct temporal pattern for wildfire incidents across the western United States. We investigate the dynamic interplay of observed soil moisture, vegetation water content, and atmospheric dryness in relation to fuel loading, fire ignition and post-fire recovery. We find that positive soil moisture anomalies around 5 months before fire ignition increase biomass growth in the subsequent months, thereby shaping fire-prone vegetation conditions. Then, concurrent decrease in soil moisture, vegetation dehydration, and atmospheric dryness collectively contribute to the occurrence of fire ignition events. This is followed by a rapid recovery in both soil and atmospheric moisture within several weeks after the fire incidents. Our findings provide insights into understanding of wildfire ignition dynamics, supporting fire modeling and enabling improved fire predictions, early warning systems, and mitigation strategies.

Concurrent pollution of fine particulate matter (PM2.5) and ozone has been increasingly reported in China recently. Here, we further confirm widespread co-occurring summertime PM2.5-ozone extremes in southern China. Annual-average frequency of co-occurrence is above 50% from 2015 to 2022, especially in Pearl River Delta region (72 ± 12%). The spatial extent (city numbers) and temporal persistence (co-occurrence days) for cities with co-occurrence frequency >50% increase at a rate of two cities/year and 14 days/year, respectively. We further identify typical synoptic conditions (e.g., typhoon periphery circulation, West Pacific subtropical high) conducive to widespread co-occurrence. Through combining multi-source data, Random Forest model well predicts PM2.5-ozone co-occurrence and identifies common precursors (e.g., volatile organic compounds) as important variables. Finally, we postulate co-occurrence is linked to synoptic conditions and secondary generation of PM2.5-ozone from shared precursors. Our results suggest high potentials for co-occurring PM2.5-ozone extremes in southern China and control strategies on common precursors to mitigate concurrent pollution.

It is well known that global warming increases the atmospheric water vapor content, which results in substantial changes in the hydrological cycle. Using five observational data sets, the results show that an increasing trend of near-surface water vapor pressure (AVP) over land and ocean was significant from 1975 to 1998, while such an increasing trend in AVP subsequently weakened from 1999 to 2019. This phenomenon is associated with decreased oceanic evaporation and land surface evapotranspiration in response to recent climate variations. One consequence of such a phenomenon is a large increase in near-surface vapor pressure deficit (VPD), which in turn increases atmospheric demand for water vapor and thus aridity and drought over land. This result emphasizes the importance of water vapor change under global warming.

Precipitation exerts far-reaching impacts on both socio-economic fabric and individual well-being, necessitating concerted efforts in accurate forecasting. Deep learning (DL) models have increasingly demonstrated their prowess in forecasting meteorological elements. However, traditional DL prediction models often grapple with heavy rainfall forecasting. In this study, we propose physics-informed localized graph neural network models called ω-GNN and ω-EGNN, constrained by the coupling of physical variables and climatological background to predict precipitation in China. These models exhibit notable and robust improvements in identifying heavy rainfall while maintaining excellent performance in forecasting light rain by comparing to numerical weather prediction (NWP) and other DL models with multiple perturbation experiments in different data sets. Surprisingly, within a certain range, even when a DL model utilizes more input variables, GNN can still maintain its advantage. The methods to fuse physics into DL model demonstrated in this study may be promising and call for future studies.

Pelagic organisms inhabiting coastal upwelling regions face a high risk of advection away from the nearshore productive habitat, potentially leading to mortality. We explored how animals remain in a productive yet highly advective environment in the Northern California Current System using the cabled observatory system located off the Oregon coast. Acoustic scatterers consistent with swimbladder-bearing fish were only present during the downwelling season as these animals avoided the cold waters associated with strong upwelling conditions in summer and fall. Fish responded to short-term upwelling events by increasing the frequency of diel vertical migration. Throughout the study, their vertical positions corresponded to the depth of minimum cross-shelf transport, providing a mechanism for retention. The observed behavioral response highlights the importance of studying ecological processes at short timescales and the abilities of pelagic organisms to control their horizontal distributions through fine-tuned diel vertical migration in response to upwelling.

Myanmar bears a high risk of destructive earthquakes, yet detailed seismicity catalogs are rare. We designed a deep-learning-based data processing pipeline and applied it to the data recorded by a large-aperture (∼400 km) seismic array in central Myanmar to produce a high-resolution earthquake catalog. We precisely located 1891 earthquakes at shallow (<50 km) depth, a 2-fold increase compared to the traditional procedures. The new catalog reveals the Kabaw Fault seismicity disappears south of ∼22.8°N, where the deeper (20–40 km) seismicity appears west of the southern Kabaw Fault. Such seismicity contrast along the strike of the Kabaw Fault possibly implies an along-strike change of deformation responses to the shortening process by the India plate oblique subduction. The middle segment of the Sagaing Fault is likely locked and prone to hosting large earthquakes according to the derived low b-value.

The location and origin of Neoproterozoic-Cambrian sutures provide keys to understand the formation and evolution of the supercontinent Gondwana. The Larsemann Hills is located near a major Neoproterozoic-Cambrian suture zone in the Prydz Belt, but has not been examined locally by comprehensive geophysical studies. In this study, we analyzed data collected from a one-dimensional (1D) joint seismic-MT array deployed during the 36th Chinese National Antarctic Research Expedition. We found that a sharp Moho discontinuity offset of 6–8 km shows up in the stacked image of teleseismic P-wave receiver function analysis; coinciding with the abrupt Moho offset, a near-vertical channel with (a) low resistivity extending to the uppermost mantle depths, and (b) high crustal Poisson's ratio in the crust is identified. These findings provide evidence for the determination of the location and collisional nature of the Prydz belt or a portion of it.

We present simulation results of the vertical structure of Large Scale Traveling Ionospheric Disturbances (LSTIDs) during synthetic geomagnetic storms. These data are produced using a one-way coupled SAMI3/Global Ionosphere Thermosphere Model (GITM) model, where GITM provides thermospheric information to SAMI3 (SAMI3 is Another Model of the Ionosphere), producing LSTIDs. We show simulation results which demonstrate that the traveling atmospheric disturbances (TADs) generated in GITM extend to the topside ionosphere in SAMI3 as LSTIDs. The speed and wavelength (600–700 m/s and 10º–20° latitude) are consistent with LSTID observations in storms of similar magnitudes. We demonstrate the LSTIDs reach altitudes beyond the topside ionosphere with amplitudes of <5% over background which will facilitate the use of plasma measurements from the topside ionosphere to supplement measurements from Global Navigation Satellite System in the study of Traveling Ionospheric Disturbances (TIDs). Additionally, we demonstrate the dependence of the characteristics of these TADs and TIDs on longitude.

A relation between tectonics and arc magmatism has been proposed in the west Pacific-type accretionary orogens, but the specific mechanism remains unclear. This study examines the Cretaceous records in NE Asia in order to unravel this link. Two tectono-magmatic episodes, namely the Early and Late Cretaceous, are recognized. The first episode was under (trans-)extension, consisting of both mafic and felsic, depleted and enriched, and deep- and shallow-derived arc magmas. The second episode experienced several compressive events with highly evolved and shallow-derived (mid-crustal level) arc magmas. We propose that (trans-)extension thinned the arc crust, facilitating deep mafic magmas to ascend and cool rapidly, maintaining their geochemical diversity. Compression led to magmatic emplacement around the middle crust; and the warm crust allowed highly-evolved granitoids to form. Therefore, tectonic setting controls arc magmatism in NE Asia, and is likely representative of other west Pacific-type orogens.

New particle formation (NPF) substantially contributes to global cloud condensation nuclei (CCN), and their climate impacts. Individual NPF events are also thought to increase local CCN, cloud droplet number (CDN), and cloud albedo. High resolution simulations however go against the latter, showing that radiatively important stratiform clouds can experience a systematic and substantial decrease in CDN during and after NPF events. CDN drops because particles too small to act as CCN uptake condensable material, and stunt the growth of particles that would otherwise form droplets. Convective clouds however experience modest increases in CDN—consistent with established views on the NPF-cloud link. Together, these results reshape our conceptual understanding of NPF impacts on clouds, as the newly discovered duality of responses would drive cloud systems in a fundamentally different manner than thought.

Magnetopause shadowing (MPS) effect could drive a concurrent dropout of radiation belt electrons and ring current protons. However, its relative role in the dropout of both plasma populations has not been well quantified. In this work, we study the simultaneous dropout of MeV electrons and 100s keV protons during an intense geomagnetic storm in May 2017. A radial diffusion model with an event-specific last closed drift shell is used to simulate the MPS loss of both populations. The model well captures the fast shadowing loss of both populations at L* > 4.6, while the loss at L* < 4.6, possibly due to the electromagnetic ion cyclotron wave scattering, is not captured. The observed butterfly pitch angle distributions of electron fluxes in the initial loss phase are well reproduced by the model. The initial proton losses at low pitch angles are underestimated, potentially also contributed by other mechanisms such as field line curvature scattering.

Lightning channel morphology depends on the thunderstorm cloud charge structure, which in turn is influenced by the thunderstorm dynamics. In this paper, based on three-dimensional radiation source localization data from the Lightning Mapping Array and radar-based data, our analysis shows that the overall morphology and detailed morphology of the lightning channel correspond to different eddy dissipation rate (EDR) characteristics. Lightning with complex channel morphology occurs in regions with large EDRs. In single lightning events, channels that extend directly within a certain height range without significant bifurcation and turning tend to propagate in the direction of decreasing EDRs, while channel bifurcations and turns usually occur in regions with large radial velocity gradients and large EDRs. This study shows the relationship between channel morphology and thunderstorm dynamics and provides a new method for the direct application of channel-level localization data to understand thunderstorm dynamics characteristics.

Following the termination of seafloor spreading in the South China Sea (SCS) basin, abundant intraplate volcanism widely spreads in the Indochina block, SCS basin, and Leiqiong area, forming the Southeastern Asian Basalt Province (SABP). The geodynamic origin of the SABP has long been enigmatic and debated. Here, we present a high-resolution 3-D upper mantle S-wave velocity model in the region by conducting earthquake-based surface wave tomography with seismic data collected across Southeast Asia. The resultant images depict a plume-like structure beneath the central area of the SABP, characterized by a continuous, sub-vertical low-velocity column in the upper mantle. Our new findings, combined with previous geochemical and geodynamic evidence, suggest that the extensive post-spreading intraplate volcanism within the SABP is likely induced by this focused mantle upwelling, which could be further traced down to the core-mantle boundary as inferred by existing global velocity models.

The core-mantle boundary (CMB) marks the most dramatic changes in physical properties within the Earth, and plays a critical role in the understanding of the Earth's dynamics. PmKP waves are seismic phases that reflect (m − 1) times under the CMB and are useful for studying the complex CMB structure. We present an automated workflow for detecting PmKP phases using multi-station records from global seismic stations. We employ a novel sampling method to extract PmKP waveforms into a 2-D matrix. Two deep neural networks are then utilized for initial phase detections and subsequent slowness validations. Numerous PmKPab (3 ≤ m ≤ 7) and their CMB diffracted signals were identified for deep earthquakes (magnitude >6) occurred from 2000 to 2020, including diffracted P7KPab waves with diffraction lengths of nearly 20°. Our approach significantly improves the efficiency of PmKP phase identification and holds the capability to detect other weak core phases, such as PKiKP.

Quasiperiodic (QP) emissions are whistler-mode electromagnetic waves observed in the Earth's inner magnetosphere whose intensity has a nearly periodic time modulation with typical modulation periods on the order of minutes. Some events exhibit, on top of the main modulation period, an additional fine inner modulation with modulation periods on the order of seconds. We use high-resolution multi-component electromagnetic wave data obtained by the Van Allen Probes spacecraft to investigate one such event. Detailed wave analysis demonstrates that the fine inner modulation is due to a wave packet bouncing back and forth between the hemispheres. The presence of a density duct is important for the formation of the event, as demonstrated by the increased ratio of wave power propagating away from the equator (a tentative source region) within the duct. The main QP modulation period corresponds to the plasma number density modulation observed just outside the plasmasphere.

In this study we use micromagnetic modeling to show that the magnetizations of magnetically single-vortex particles rotate toward the stress axis on the application of a differential compression stress. This is the exact opposite response to magnetically single-domain particles, which previously provided the theoretical underpinning of the effect of stress on the magnetic signals of rocks. We show that the magnetization directions of single-vortex and equant single-domain particles are altered by much lower stresses than previously predicted, c.f., 100 versus 1,000 MPa; where a change in magnetization is defined as a rotation of >3° after the removal of stress. The magnetization intensity of assemblages also drops by ∼20%–30% on the application and removal of stress of ∼100 MPa. Given that single-vortex particles are now thought to dominate the magnetization of most rocks, future studies should account for paleomagnetic directional uncertainties and potential underestimation of the ancient magnetic field intensity.

Central Asia (CA) has experienced a faster temperature rise than the global land over the past decades. However, the role of regional/global drivers and their associated underlying biophysical mechanisms is poorly explored. Here, we combined observations and model simulations to show that the rapid warming in CA was overwhelmingly contributed by rapid spring warming (i.e., 49.23%). The decrease of cloud cover (CLD) was the main driver of spring warming in CA, leading to the surface receiving more solar radiation, consequently heating the surface air temperature, and contributing almost 40.79% to the spring warming. Besides, the strengthening of sea level pressure states results in continuous subsidence of vertical motion over CA, which was unfavorable for cloud formation. Our study will deepen our understanding of the climate evolution in the arid CA.