A document by Anis Elyouncha. Click on the document to view its contents.

Abstract All earthquakes over 5th magnitude since 1962 were recorded on Sumatra and surroundings, marking their depths and distinguished whether they were triggered by maximum westward or north-southward tidal torques. Greatest differences were found in period 2003-2009 where earthquakes triggered by north-southward torque were situated on rim of Sumatra continental area on Mentawai Fault. Period 2009-2023 is characteristic by large number of westward tidally triggered earthquakes, situated westward from Sumatra coast reaching sometimes as far as into oceanic lithosphere. As far as the great earthquake M 9.1, 26.12.2004 was triggered by the beat of close tidal frequencies: 19 years Metonic cycle and Moon’s nodal 18.61 years variations and if the beat were symmetric with maximum amplitude 26.12.2004, then because Full Moon will be 27.12.2023 and New Moon 11.1.2024, (Moon’ declinations large +28.1º and -27.6º respectively), the earthquake will occur of 6.5 5th magnitude as similar earthquake 27.12.1985. This prediction has not been fulfilled because the beat has not been symmetric, but asymmetrically shifted by westward tidal torque as proved by absolutely missing earthquakes 25. and 26.12. 2023, documented by very sensitive earthquakes detection up to 2.5 magnitude.

Convective dissolution of CO2 is a well-known mechanism in geological storage of CO2 . It is triggered by gravitational instability which leads to the onset of free convection. The phenomenon is well studied in porous media, such as saline aquifers, and the literature provides substantial evidence that onset times and effective flux rates can be estimated based on a characterization of instabilities that uses the Darcy velocity. This work extends the study of convective dissolution to open water-filled fractures, where non-Darcy regimes govern the induced flow processes. Numerical simulations using a Navier-Stokes model with fluid density dependent on dissolved CO2 concentration were used to compute scenario-specific results for effective CO2 entry rates into an idealized fracture with varying aperture, temperature, and CO2 concentration at the gas-water interface. The results were analyzed in terms of dimensionless quantities. They revealed a Rayleigh invariance of the effective CO2 flux after the complete formation of a quasi-stationary velocity profile, i.e. after a certain entry length. Hence, this invariance can be exploited to estimate the effective CO2 entry rates, which can then be used, in perspective, in upscaled models. We have studied convective CO2 dissolution for two different fracture settings; the first one relates to karstification scenarios, where CO2 is the dominant driving force, and were stagnant-water conditions in fractures have not yet received attention to date. The second setting is inspired from geological CO2 storage, where the literature provides only studies on convective CO2 dissolution for porous-media flow with Darcy regimes.

Earth's climate sensitivity depends on how shallow clouds in the trades respond to changes in the large-scale tropical circulation with warming. In canonical theory for this cloud-circulation coupling, it is assumed that the clouds are controlled by the field of vertical motion on horizontal scales larger than the convection's depth (~1 km). This assumption has been challenged both by recent in-situ observations, and idealized large-eddy simulations (LESs). Here, we therefore bring together the recent observations, new analysis from satellite data, and a forty-day, large-domain (1600 x 900 km2) LES of the North Atlantic from the 2020 EUREC4A field campaign, to study the interaction between shallow convection and vertical motions on scales between 10-1000 km (mesoscales), in settings that are as realistic as possible. Across all datasets, the shallow mesoscale vertical motions are consistently represented, ubiquitous, frequently organised into circulations, and formed without imprinting themselves on the mesoscale buoyancy field. Therefore, we use the weak-temperature gradient approximation to show that between at least 12.5-400 km scales, the vertical motion balances heating fluctuations in groups of precipitating shallow cumuli. That is, across the mesoscales, shallow convection controls the vertical motion in the trades, and does not simply adjust to it. In turn, the mesoscale convective heating patterns appear to consistently grow through moisture-convection feedback. Therefore, to represent and understand the cloud-circulation coupling of trade cumuli, the full range of scales between the synoptics and the hectometre must be included in our conceptual and numerical models.

A document by Zixuan Zhou. Click on the document to view its contents.

Tree-ring series from ENSO rainfall impact regions reconstruct the tropical Pacific SST field with a high degree of skill back to 1100 CE. 2. Two very different reconstruction methods produce similar results and each can only reconstruct the leading EOF mode of SST variability. 3. Reconstructions extending back 1100 CE do not reveal any clear increase in El Niño variability, but do show a recent overall SST warming.

Peak glacial-to-Heinrich-1 changes in Denmark Strait Overflow and seawater stratification in the Nordic Seas, a switchboard of changes in Atlantic Meridional Overturning Circulation and the ’Nordic Heat Pump’Michael Sarnthein1) and Patrick Blaser2)1) Institut für Geowissenschaften, University of Kiel, D-24118 Kiel, Germany

A document by Bhupendra Bahadur Singh. Click on the document to view its contents.

Tropical cyclones bring health risks and can trigger outbreaks of diarrheal diseases in affected populations. There are several reviews that mention the relationship between tropical cyclones and diarrheal diseases. However, there is no dedicated review of the current evidence and extent of research on the association between tropical cyclones and diarrheal diseases. We performed a scoping review to thoroughly examine the available literature. We also thematically analyzed the transmission pathways explained in the literature. A total of 96 studies were included. Twenty-three studies quantitatively measured the tropical cyclone--diarrhea associations, with half reporting positive associations. We found that the studies defined and measured tropical cyclone exposure differently and mostly analyzed a single event. The study designs employed were mostly pre-post comparisons that had several limitations affecting internal validity. These differences also prevent the quantitative pooling of evidence. A standardized approach to measuring the association between tropical cyclones and diarrheal diseases can be devised by suggesting the most appropriate exposure definition and modeling.

Characterizing fault behaviors prior to large earthquakes through long-term seismicity is crucial for seismic hazard assessment, yet constructing high-resolution catalogs over extended periods poses significant challenges. This study introduces LoSAR, a novel deep learning-driven workflow that enhances phase picking by Localizing a Self-Attention Recurrent neural network with local data, addressing the generalization problem common in data-driven approaches. We apply LoSAR to two distinct regions that are both featured by recent large earthquakes: (1) preseismic period of the Ridgecrest-Coso region (2008-2019), and (2) pre-postseismic period of the East Anatolian Fault Zone (EAFZ, 2020-2023/04). Through detailed comparisons, we demonstrate that LoSAR offers slightly higher detection completeness than the QTM matched filter catalog, while boosts an over 100 times faster processing and a superior temporal stability, avoiding low-magnitude gaps during background periods. Against PhaseNet and GaMMA, two established phase picker and associator, LoSAR proves more scalable and generalizable, achieving roughly 2.5 times more event detections in the EAFZ case, along with a ~7 times higher phase association rate. By leveraging the two enhanced catalogs and b-value analysis, we gain insights into the preseismic fault behaviors: (1) The Ridgecrest faults are characterized by sparse and distributed seismicity across a band of ~20 km, revealing multiple orthogonal preexisting faults; coupled with a low b-value that signifies this area as a persistent asperity; (2) The Erkenek-Pütürge segment of EAFZ exhibits complex fault geometry that forms a persistent rupture barrier, which consists of a hidden conjugate fault system that presents as a ~10-km wide fault zone.

This study presents the development of a TKE-l parameterization of the diffusion coefficients for the representation of turbulent diffusion in neutral and stable conditions in large-scale atmospheric models. The parameterization has been carefully designed to be completely tunable in the sense that all adjustable parameters have been clearly identified and their number minimized as much as possible to help the calibration and to thoroughly assess the parametric sensitivity. We choose a mixing length formulation that depends on both static stability and wind shear to cover the different regimes of stable boundary layers. We follow a heuristic approach for expressing the stability functions and turbulent Prandlt number in order to guarantee the versatility of the scheme and its applicability for planetary atmospheres composed of an ideal and perfect gas such as that of Earth and Mars. Particular attention has also been paid to the numerical stability at typical time steps used in General Circulation Models. Test, parametric sensitivity assessment and preliminary tuning are performed on single-column idealized simulations of the weakly stable boundary layer. The robustness and versatility of the scheme are also assessed through its implementation in the LMDZ General Circulation Model and the Mars Planetary Climate Model and by running simulations of the Antarctic and Martian nocturnal boundary layers.

The tectono-stratigraphic development of continental basins is key to our understanding of the location and scale of metal deposits required by the energy transition. We examine the Neo-proterozoic Katangan copper basin of Central Africa to determine the link between lithosphere and crust and the generation of potential fluid pathways. Integration of lithospheric thickness, quantitative basin analysis and structure, defines a basin scale tectono-stratigraphic model for controls on potential fluid pathways. The basin developed along the thinned (140-170 km thick) margins of the Congo, Kalahari and Bangweulu cratons. Crustal scale fault zones define these margins and imply a mechanical weakness in the basin. Drill core and seismic data show extensional, half graben geometries. Basin subsidence analysis indicates two phases of rift-driven subsidence and increasing lithospheric extension from the basin boundary to a Central Rift Zone (CRZ). The CRZ also maps out as a sediment provenance boundary. Subsequent Late Ediacaran and Cambrian orogenesis and rift-fault inversion occurred most intensively within the CRZ. Basin expulsion and thrust tectonics resulted in a narrow belt of crustal thickening defined today by a ~50 km wide zone of garnet amphibolite facies metamorphism. The spatial coincidence of early crustal extension, relatively thin lithosphere, and later intense basin inversion along the CRZ, indicates that pre-existing crustal structure and weakness was a key tectonic control. The reactivated structures define several tectonic domains, control basin architecture within the zones and occur as potential fluid pathways for high volume fluid migration for metal bearing brines.

Natural porous media is generally heterogeneous and anisotropic. The structure of porous media plays a vital role and is often the source of the heterogeneity and anisotropy. In physical processes such as fluid flow in porous media, a small number of major features, here referred to as wide channels, are responsible for the majority of the flow. The thickness and orientation of these channels often determine the permeability characteristics. Typically, the identification of such major features is conducted through time-consuming and expensive simulations. Here we propose a prompt approach based on geometric properties derived from three-dimensional (3D) images. The size or radius of the major features is obtained via distance maps, and their orientations are determined by Principal Component Analysis. Subsequently, we visualize these features with color and color brightness according to their orientation and size, together with their location and distribution in 3D space. The simultaneous visualization of anisotropy (orientation) and heterogeneity (size) in one plot provides a straightforward way to enhance our understanding of pore structure characteristics. Besides, we propose a refined stereographic projection method to statistically illustrate both heterogeneity and anisotropy. Based on these insights, we further present a new way to compress the model size in numerical simulation, therefore significantly reducing the computational cost, while retaining its essential characteristics.

The Arabian Gulf (AG) exports hypersaline, dense waters into the Sea of Oman (SOO), replaced by fresher inflowing surface waters from the Indian Ocean. We investigate the impact of recent AG warming on its exchange with the SOO and the implications this has on the AG biogeochemistry. Using an eddy-resolving hindcast model simulation, we analyze the hydrography and biogeochemistry of the AG and the SOO from 1980 to 2018. Our study reveals that changes in summer surface winds have accelerated AG warming and weakened it in the SOO, reducing the density gradient and water exchange between the two seas during late summer. This has led to nutrient buildup, increased productivity, and heightened deoxygenation and acidification in the AG. These findings underscore how subtle wind changes can exacerbate the vulnerability of marginal seas to climate change and stress the need to properly represent regional winds in global climate models.

Idealized general circulation models (GCMs) suggest global-mean precipitation ceases to increase with warming in hot climates. However, it is unclear if this occurs in more comprehensive GCMs. Here, we examine precipitation over a wide range of climates simulated with comprehensive GCMs. We find that in the Community Atmosphere Model, global-mean precipitation increases approximately linearly with global-mean surface temperatures up to about 330~K, where it peaks at 5~mm~day$^{-1}$. Beyond 330~K, global-mean precipitation decreases substantially despite increasing surface temperatures. This occurs because of increased atmospheric shortwave absorption from water vapor, which limits shortwave radiation available for surface evaporation. Precipitation decreases in the tropics and subtropics, but continues to increase in the extratropics due to increased poleward moisture transport. Precipitable water increases everywhere, resulting in longer water-vapor residence times and implying more episodic precipitation. Other GCMs indicate global-mean precipitation might exhibit a smaller maximum rate and begin to decrease at lower surface temperatures.

A document by Deep S Banerjee. Click on the document to view its contents.

Surface ozone regulation policies rely heavily on air quality models, such as CAMx, as important guiding tools. Comparison with observations is crucial to validating a model’s ability to represent ozone production chemistry. Identifying factors influencing surface ozone formation is complicated because ozone photochemical production rates are non-linearly dependent on concentrations of precursors such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). We compare ozone production regimes (OPRs) identified from satellite observations and model simulations, as defined by the ratio of column formaldehyde to nitrogen dioxide (FNR, HCHO/NO2). We perform CAMx simulations for June-July-August 2016 over the Contiguous United States (CONUS) and compared these outputs against two OMI NO2and HCHO retrievals. Our analysis spans diurnal and altitudinal variations of OPRs, offering important insights for effective policy formulation. At the time of the OMI overpass (~1:30 PM LT), OPR is NOx-limited over most of the CONUS, as determined from OMI column ratios. Analysis of CAMx column ratios shows similar results. In contrast, more regions are VOC-limited when we constrain our ratio to within the Planetary Boundary Layer (PBL). In the morning (~9 AM LT), the CAMx PBL column ratios shift towards VOC-limited regime. We highlight areas of the CONUS for which satellite measurements of FNR may not be an accurate indicator of near-surface OPRs. Air quality regulations based on satellite observations should consider the diurnal variations of surface OPRs and assess how well their ratios represent near-surface OPR. Our results have implications for interpretation of TEMPO data for policy relevant applications.

The Arctic winter-time atmospheric boundary layer often features strong and persistent low-level stability which arises from longwave radiative cooling of the surface during the polar night. This stable stratification results in a positive lapse rate feedback, which is a major contributor to Arctic amplification. A second state, associated with cloudy conditions, with weaker stability and near-zero net surface longwave flux is also observed. Previous work has shown that many CMIP5 climate models fail to realistically represent the cloudy state. In this study, we assess the representation of the Arctic atmospheric boundary layer over sea ice during the winter months in global climate models contributing to the latest phase of the Coupled Model Intercomparison Project (CMIP6). We compare boundary layer process relationships seen in these models to those in surface-based and radiosonde observations collected during the recent MOSAiC (2019-2020) field campaign, alongside the earlier SHEBA (1997-1998) expedition, and from North Pole drifting stations (1955-1991). Here, we show that a majority of CMIP6 models fail to realistically represent the cloudy state over winter Arctic sea ice. Despite this, CMIP6 models have a multi-model mean low-level stability which falls within the range recorded by observational campaigns, and are mostly able to capture the observed dependence of low-level stability on near-surface air temperature and wind speed. As the Arctic warms, CMIP6 models predict a decline of winter low-level stability, with the Central Arctic’s mean stability falling below zero in the multi-model mean state by the end of the century under the SSP2-4.5 emissions scenario.