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Abstract

We present measurements of 30–700 keV Solar Energetic Electrons (SEEs) near the Moon when within the terrestrial magnetotail by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun spacecraft. Despite their detection deep within the tail, the incident flux and spectral shape of these electrons are nearly identical to measurements taken upstream of Earth in the solar wind by the Wind spacecraft; however, their pitch angle distribution is isotropized compared to the more field-aligned distribution upstream. We illustrate that SEEs initially traveling Earthward precipitate onto the lunar far-side, generating extended shadows in the cis-lunar electron distribution. By modeling the dynamics of these electrons, we show that their precipitation patterns on the lunar near-side are comparatively reduced. The non-uniform precipitation and accessibility of potentially hazardous electrons to the Moon's surface are highly relevant in the context of astronaut safety during the planned exploration of the lunar environment.

Abstract

Subsurface gas storage is crucial for achieving a sustainable energy future, as it helps to reduce CO2 emissions and facilitates the provision of renewable energy sources. The confinement effect of the nanopores in caprock induces distinctive thermophysical properties and fluid dynamics. In this paper, we present a multi-scale study to characterize the subsurface transport of CO2, CH4, and H2. A nanoscale-extended volume-translated Cubic-Plus-Association equation of state was developed and incorporated in a field-scale numerical simulation, based on a full reservoir-caprock suite model. Results suggest that in the transition from nanoscale to bulk-scale, gas solubility in water decreases while phase density and interfacial tension increase. For the first time, a power law relationship was identified between the capillary pressure within nanopores and the pore size. Controlled by buoyancy, viscous force and capillary pressure, gases transport vertically and horizontally in reservoir and caprock. H2 has the maximum potential to move upward and the lowest areal sweep efficiency; in short term, CH4 is more prone to upward migration compared to CO2, while in long term, CH4 and CO2 perform comparably. Thicker caprock and larger caprock pore size generally bring greater upward inclination. Gases penetrate the caprock when CH4 is stored with a caprock thickness smaller than 28 m or H2 is stored with a caprock pore size of 2–10 nm or larger than 100 nm. This study sheds light on the fluid properties and dynamics in nanoconfined environment and is expected to contribute to the safe implementation of gigatonne scale subsurface gas storage.

Abstract

Bottom currents play a major role in deep-sea sedimentation, but their significance in the burial of organic carbon is poorly quantified at a global scale. Here we show that Holocene fluxes of organic carbon into the contourite drifts are high, with a global average of 0.09 g cm−2 Kyr−1. At individual drift sites, fluxes are commonly 1–2 orders of magnitude greater than rates in surrounding areas and in global depth-similar zones. These high fluxes of organic carbon into the contourite drifts are due to high rates of sedimentation. Over the past 50 million years, sedimentation rates at the studied contourite drift sites have overall increased, coincident with decreasing atmospheric CO2 and a cooling global climate. Our work suggests that a ramp-up of the bottom-current carbon pump has accelerated removal of CO2 from the atmosphere and oceanic water, thus contributing to the overall global cooling after the Eocene Thermal Maximum.

Abstract

Complex natural fracture networks typically consist of multiple clusters, whose connectivity is rarely quantified. Therefore, for each identified fracture network, we propose a connectivity metric that accounts for individual fracture clusters and their interactions. This metric evaluates contributions from all fracture clusters, considering their relative sizes and interactions among the isolated clusters, which in turn depend on the hydraulic conductance of the interconnecting rock matrix. Furthermore, we investigate how the system connectivity depends on fracture sealing, alterations of central clusters, and cluster linkage. Fracture sealing strongly impacts overall fracture connectivity, with 5 percent of sealed fractures reducing connectivity by 20 percent. The connectivity reduction is small when transitioning the central cluster from the largest to the smallest one. However, the largest cluster significantly contributes to overall connectivity, while the smallest one contributes minimally. Natural fracture networks increase connectivity by linking more clusters, with heterogeneity and anisotropy playing pivotal roles.

What can we learn from global disaster records about multi-hazards and their risk dynamics?
Wiebke S. Jäger, Marleen C. de Ruiter, Timothy Tiggeloven, and Philip J. Ward
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-134,2024
Preprint under review for NHESS (discussion: open, 0 comments)
Multiple hazards, occurring at the same time or shortly after one another, can have more extreme impacts than single hazards. We examined the disaster records in the global emergency events database EM-DAT to better understand this phenomenon. We developed a method to identify such multi-hazards and analyzed their reported impacts using statistics. Multi-hazards have accounted for a disproportionate amount of the overall impacts, but there are different patterns in which the impacts compound.

Abstract

Since the 1950s, observations and climate models show an amplification of sea surface temperature (SST) seasonal cycle in response to global warming over most of the global oceans except for the Southern Ocean (SO), however the cause remains poorly understood. In this study, we analyzed observations, ocean reanalysis, and a set of historical and abruptly quadrupled CO2 simulations from the Coupled Model Intercomparison Project Phase 6 archive and found that the weakened SST seasonal cycle over the SO could be mainly attributed to the intensification of summertime westerly winds. Under the historical warming, the intensification of summertime westerly winds over the SO effectively deepens ocean mixed layer and damps surface warming, but this effect is considerably weaker in winter, thus weakening the SST seasonal cycle. This wind-driven mechanism is further supported by our targeted coupled model experiments with the wind intensification effects being removed.

Abstract

Solar-induced fluorescence (SIF) is a proxy of ecosystem photosynthesis that often scales linearly with gross primary productivity (GPP) at the canopy scale. However, the mechanistic relationship between GPP and SIF is still uncertain, especially at smaller temporal and spatial scales. We deployed a ultra-hyperspectral imager over two grassland sites in California throughout a soil moisture dry down. The imager has high spatial resolution that limits mixed pixels, enabling differentiation between plants and leaves within one scene. We find that imager SIF correlates well with diurnal changes in leaf-level physiology and gross primary productivity under well-watered conditions. These relationships deteriorate throughout the dry down event. Our results demonstrate an advancement in SIF imaging with new possibilities in remotely sensing plant canopies from the leaf to the ecosystem. These data can be used to resolve outstanding questions regarding SIF's meaning and usefulness in terrestrial ecosystem monitoring.

Abstract

This study investigates the potential impact of Solar Energetic Particles (SEPs) on the V0 layer of the Venus ionosphere. Electron density profiles obtained from radio occultation experiments conducted by the Venus Express (VEX) and Akatsuki missions were utilized for this purpose. Background data from the Analyzer of Space Plasma and EneRgetic Atoms (ASPERA-4) aboard VEX were used to detect SEP events. Additionally, observations from the Space Environment Monitor (SEM) suite onboard the Geostationary Operational Environmental Satellite (GOES) during alignments of Venus, Earth, and the Sun were also considered. Our findings indicate that while SEPs may contribute to the formation of the V0 layer, they are not the main driving force in the Venusian ionosphere.

Abstract

NOAA Daily Optimum Interpolation Sea Surface Temperature (DOISST) and other similar sea surface temperature (SST) products indicate that the globally averaged SST set a new daily record in March 2023. The record-high SST in March was immediately broken in April, and new daily records were set again in July and August 2023. The SST anomaly (SSTA) persisted at a record high from mid-March to the remainder of 2023. Our analysis indicates that the record-high SSTs, and associated marine heatwaves (MHWs) and even super-MHWs, are attributed to three factors: (a) a long-term warming trend, (b) a shift to the warm phase of the multi-decadal Pacific-Atlantic-Arctic (PAA) mode, and (c) the transition from the triple-dip succession of La Niña events to the 2023–24 El Niño event.

Abstract

Fluid-induced seismicity has been a particularly emphasized mechanism over the last few years, especially after fluid-related, moderate-to-large earthquakes have been observed in several locations around the globe. Several studies suggest that the relationships between seismicity and fluid presence are related to variations in the stress state of rocks, due to the increase or drop of the pore fluid pressure. In this scenario, the Val d’Agri represents a precious case study where fluid-induced seismicity is observed. In this area, two seismic clusters are observed in the Apulian Carbonate Platform, caused by (a) wastewater reinjection that reactivated the Costa Molina Fault blind thrust, and (b) seasonal water loading from the Pertusillo reservoir. The mechanisms behind these reactivated faults' evolution are still uncertain, especially in the compressive/extensional tectonic setting characterizing the area's evolution. Consequently, the distribution of the seismic potential in the region is largely unconstrained. We constructed a numerical thermo-mechanical model to identify the main mechanisms that promoted the Val d’Agri present-day tectonic setting and to assess the seismic hazard characterizing this region. We show that deformation within the Sedimentary Cover and the Crystalline Basement decoupled along a major décollement layer, represented by the Triassic Burano Formation. We also estimate the Coulomb stress (σ C ) in the region, assessing the crust's potential to generate earthquakes. Our results suggest that σ C  > 0 in a large part of the crust, and therefore that fluid injection may be particularly effective for the reactivation of buried structures, especially at a depth between ≃2 and ≃6 km.

Multi-angle aerosol optical depth retrieval method based on improved surface reflectance
Lijuan Chen, Ren Wang, Ying Fei, Peng Fang, Yong Zha, and Haishan Chen
Atmos. Meas. Tech., 17, 4411–4424, https://doi.org/10.5194/amt-17-4411-2024, 2024
This study explores the problems of surface reflectance estimation from previous MISR satellite remote sensing images and develops an error correction model to obtain a higher-precision aerosol optical depth (AOD) product. High-accuracy AOD is important not only for the daily monitoring of air pollution but also for the study of energy exchange between land and atmosphere. This will help further improve the retrieval accuracy of multi-angle AOD on large spatial scales and for long time series.

Comparison of diurnal aerosol products retrieved from combinations of micro-pulse lidar and sun photometer observations over the KAUST observation site
Anton Lopatin, Oleg Dubovik, Georgiy Stenchikov, Ellsworth J. Welton, Illia Shevchenko, David Fuertes, Marcos Herreras-Giralda, Tatsiana Lapyonok, and Alexander Smirnov
Atmos. Meas. Tech., 17, 4445–4470, https://doi.org/10.5194/amt-17-4445-2024, 2024
We compare aerosol properties over the King Abdullah University of Science and Technology campus using Generalized Retrieval of Aerosol and Surface Properties (GRASP) and the Micro-Pulse Lidar Network (MPLNET). We focus on the impact of different aerosol retrieval assumptions on daytime and nighttime retrievals and analyze seasonal variability in aerosol properties, aiding in understanding aerosol behavior and improving retrieval. Our work has implications for climate and public health.

EAT v1.0.0: a 1D test bed for physical–biogeochemical data assimilation in natural waters
Jorn Bruggeman, Karsten Bolding, Lars Nerger, Anna Teruzzi, Simone Spada, Jozef Skákala, and Stefano Ciavatta
Geosci. Model Dev., 17, 5619–5639, https://doi.org/10.5194/gmd-17-5619-2024, 2024
To understand and predict the ocean’s capacity for carbon sequestration, its ability to supply food, and its response to climate change, we need the best possible estimate of its physical and biogeochemical properties. This is obtained through data assimilation which blends numerical models and observations. We present the Ensemble and Assimilation Tool (EAT), a flexible and efficient test bed that allows any scientist to explore and further develop the state of the art in data assimilation.

Abstract

Temperature serves as a critical yet elusive factor impacting the mechanical properties of deep rocks. In this work, we shall develop a new micro-thermomechanical model for rocks based on the Mori-Tanaka homogenization scheme. Free energy and thermodynamic forces are deduced within the framework of irreversible thermodynamics, including the local stress applied on the mesocracks, damage driving force, macroscopic stress, and entropy. The salient innovation of this study lies in formulating subtle physically based temperature-dependent friction and damage laws, considering the influence of ambient temperature on the mesocracking in rocks. Through a coupled friction-damage analysis, a temperature-dependent quasi-static strength criterion and analytical stress-strain-damage relations are then derived. Physical implications and calibration methods of each parameter in the proposed model are meticulously presented. Furthermore, a semi-implicit plasticity damage decoupled procedure (SIPDDC) integration algorithm is employed for the numerical implementation of the proposed model. Subsequently, numerical simulations are conducted to obtain the mechanical response of Jinping marble, Beibei sandstone, and Gongjue granite under various real-time temperature-confining pressure coupling conventional triaxial compression tests (TP-CTC). The congruence of stress-strain curves between model predictions and experimental data validates the robust performance and potential applicability of the proposed model.

A versatile water vapor generation module for vapor isotope calibration and liquid isotope measurements
Hans Christian Steen-Larsen and Daniele Zannoni
Atmos. Meas. Tech., 17, 4391–4409, https://doi.org/10.5194/amt-17-4391-2024, 2024
The water vapor generation module is completely scalable, allowing autonomous calibrations to use N standards and providing integration times only restricted by sample availability. We document improved reproducibility in 17O-excess liquid measurements. This module makes spectroscopy measurements comparable to mass spectrometry. We document that the vapor generation module can be used to analyze instrument performance and for vapor isotope calibration during field campaign measurements.

Aerosol optical property measurement using the orbiting high-spectral-resolution lidar on board the DQ-1 satellite: retrieval and validation
Chenxing Zha, Lingbing Bu, Zhi Li, Qin Wang, Ahmad Mubarak, Pasindu Liyanage, Jiqiao Liu, and Weibiao Chen
Atmos. Meas. Tech., 17, 4425–4443, https://doi.org/10.5194/amt-17-4425-2024, 2024
China has launched the atmospheric environment monitoring satellite DQ-1, which consists of an advanced lidar system. Our research presents a retrieval algorithm of the DQ-1 lidar system, and the retrieval results are consistent with other datasets. We also use the DQ-1 dataset to investigate dust and volcanic aerosols. This research shows that the DQ-1 lidar system can accurately measure the Earth's atmosphere and has potential for scientific applications.

Abstract

Daily mean albedo, a crucial variable of the earth radiation budget, is significantly affected by the diurnal variation of land surface albedo (DVLSA). The DVLSA typically exhibits asymmetry, thereby affecting the estimation of the daily mean albedo. However, the asymmetry in the DVLSA is generally ignored in daily mean albedo estimation. In this study, we investigated the influencing factors of the asymmetry in the DVLSA and evaluated its impacts on estimating the daily mean albedo based on field observations and simulated data. Our findings reveal that the asymmetry in the DVLSA varies among land cover types, with forests exhibiting more pronounced asymmetry compared to croplands, grasslands, and bare soil. The diurnal variation of the atmospheric conditions is the primary factor controlling the asymmetry in the DVLSA, with that of land surface conditions being a secondary factor. Neglecting the asymmetry in the DVLSA leads to estimation error in daily mean albedo, particularly pronounced during winter. The relative error of daily mean albedo can exceed 10% when the mean asymmetry index of diffuse irradiance fraction reaches 40%. However, the DVLSA retrieved from the satellite Bidirectional Reflectance Distribution Function product inadequately captures asymmetry, resulting in a relative error of approximately 13.7% in estimating daily mean albedo.

Abstract

The Spring Predictability Barrier (SPB) phenomenon is characterized by the reduced accuracy of El Niño/Southern Oscillation (ENSO) forecasts during the spring, which substantially limits our ability to predict ENSO events. By investigating the nonlinear dynamic characteristics of ENSO systems simulated by a box model, we found that the strong surface heating process in spring may contribute to the SPB by regulating the different coupling processes between the ocean and atmosphere. Specifically, the intensified springtime surface heating increases the Sea Surface Temperature (SST), further amplifying the thermal damping effect of SST anomalies and reducing the dynamic connection between zonal SST gradient and upwelling process, and finally increasing the chaotic degree of ENSO systems simulated by the box model. The enhanced chaotic degree of ENSO systems leads to a more rapid growth of initial errors in the forecast model in spring, potentially leading to the SPB phenomenon.

Science, Volume 385, Issue 6707, July 2024.

Science, Volume 385, Issue 6707, July 2024.