The Crustal Fault Zones provides an interesting geological target for high temperature geothermal energy source in naturally deep-fractured basement areas. Field and laboratory studies have already shown the ability of these systems to let fluid flow down to Brittle-Ductile-Transition. However, several key questions about exploration still exist, in particular the fundamental effect of tectonic regimes on fluid flow in fractured basement domains. Based on poroelasticity assumption, we considered an idealized 3D geometry and realistic physical properties. We examined a model with no tectonic regime (benchmark experiment) and a model with different tectonic regimes applied. Compared to the benchmark experiment, the results suggest that different tectonic regimes cause pressure changes in the fault/basement system. The tectonic-induced pressure changes affect fluid patterns, onset of convection as well as the spatial extent of thermal plumes and the intensity of the temperature anomalies.

Over much of Africa, radiosonde data are lacking; consequently, the African UTLS is understudied, and potential proxies such as climate models and reanalyses fail to capture the behaviour of the UTLS fully. This study pioneers the use of Global Navigation Satellite System Radio Occultation (GNSS-RO) data from 2001 to 2020 to address the radiosonde data gaps over Africa and contributes to a better understanding of the tropopause (TP) characteristics under the influence of multiple climate drivers. The analyses show that GNSS-RO data from CHAMP, GRACE, MetOp, COSMIC, and COSMIC-2 agree with radiosonde measurements with differences being smaller than 1 K in the UTLS; thereby enabling in-filling of 80% of the missing radiosonde data in Africa during 2001-2020. By contrast, the smoothed vertical temperature profiles of reanalysis products lead to a warm bias of +0.8K in ERA5 and +1.2K in MERRA-2, and these biases alter some vertical and temporal structure details, with possible implications on climate change detection and attribution. Furthermore, the analysis of GNSS-RO data over Africa revealed: 1) influences of global climate drivers on TP temperature, with QBO > ENSO > IOD > NAO > SAM > MJO, and on TP height with ENSO > QBO > NAO > MJO > IOD > SAM; 2) multiple coupled global climate drivers such as ENSO-MJO, ENSO-NAO etc.; 3) coupled global and regional climate drivers that influence the TP variability, e.g., ENSO-ITCZ; and 4), the deep convection associated with the Asian Summer Monsoon and Tropical/African Easterly Jet locally influence TP height.

Lithospheric discontinuities, including the lithosphere-asthenosphere boundary (LAB) and the enigmatic mid-lithospheric discontinuities (MLDs), hold important clues about the structure and evolution of tectonic plates. However, P- and S-receiver-function techniques (PRF and SRF), two traditional techniques to image Earth’s deep discontinuities, have some shortcomings in imaging lithosphere discontinuities. Here, we propose a new method using reflections generated by teleseismic S waves (hereafter S reflections) to image lithospheric discontinuities, which is less affected by multiple phases than PRFs and has better depth resolution than SRFs. We apply this method to data collected by the Transportable Array and other regional seismic networks and obtain new high-resolution images of the lithosphere below the contiguous US. Beneath the tectonically active Western US, we observe a negative polarity reflector (NPR) in the depth range of 60–110 km, with greatly varying amplitude and depth, which correlates with active tectonic processes. We interpret this feature as the lithosphere-asthenosphere boundary below the Western US. Beneath the tectonically stable Central and Eastern US, we observe two NPRs in the depth ranges of 60–100 km and 100–150 km, whose amplitude and depth also vary significantly, and which appear to correlate with past tectonic processes. We interpret these features as mid-lithospheric discontinuities below the Central and Eastern US. Our results show reasonable agreement with results from PRFs, which have similar depth resolution, suggesting the possibility of joint inversion of S reflections and PRFs to constrain the properties of lithospheric discontinuities.

We have recently introduced a modification of the multiple signal classification (MUSIC) method for synthetic aperture radar. This method depends on a tunable, user-defined parameter, ε, that allows for quantitative high-resolution imaging. It requires however, relative large single-to-noise ratios (SNR) to work effectively. Here, we first identify the fundamental mechanism in that method that produces high-resolution images. Then we introduce a modification to Kirchhoff Migration (KM) that uses the same mechanism to produces tunable, high-resolution images. This modified KM method can be applied to low SNR measurements. We show simulation results that demonstrate the features of this method.

We present a 2D model of magma body formation in granitic crust by injection of rhyolitic or basaltic dikes and sills. An elastic analytical solution enables computation of rock displacement in response to magma intrusion. Phase diagrams for magma and host rocks predict melting/crystallization. We combine this model with our zircon crystallization/dissolution software and compute zircon survival histories within individual batches of magma and country rocks. Incremental accumulation of intruded magma generates interconnected magma batches of eruptible melt with melt fractions >50 vol% that form in clusters. The rate of melt production is highly variable in space and time. The volume of eruptible melt strongly depends on the input rates of magma Q and the width W of the injection region of dikes and on eruptions. For example, dikes injection with Q=0.125 m3/s with W=5 km during 100 ka generates ~50 km3 of eruptible melt while no significant melt forms if W=10 km. Injection of basaltic dikes produces more melt for the same flux rate. Frequent and small eruptions led to smaller magma bodies that are located deeper in the system, while systems with rare but voluminous eruption forms large melt. Due to partial melting, most host rock zircons loose significant portion of their old cores and, thus, their average age is reduced. Magmatic zircons in the periphery of the intrusion form very quickly due to rapid dikes cooling while in its central part crystals contain old cores and young rims and can grow during several hundreds of ka.

The long-wavelength negative gravity anomaly over Hudson Bay coincides with the area depressed by the Laurentide ice sheet during the Last Glacial Maximum, suggesting that it is, at least partly, caused by Glacial Isostatic Adjustment (GIA). Additional contributions to the static gravity field stem from dynamic topography and density anomalies in the subsurface. Previous estimates of the contribution of GIA to the gravity anomaly range from 25 percent to more than 80 percent. However, these estimates did not include uncertainties in all components that contribute to the gravity field. In this study, we develop a forward model for the gravity anomaly. We combine density anomalies, isostatic balance, and non-isostatic contributions from GIA and dynamic topography. The largest uncertainty in the predicted gravity anomaly is due to the lower mantle viscosity; uncertainties in the ice history, the crustal model, the lithosphere-asthenosphere boundary and the conversion from seismic velocities to density are found to have a smaller effect. A preference for lower mantle viscosities >10^22 Pa s is found, in which case at least 60 percent of the observed long-wavelength gravity anomaly can be attributed to GIA. This lower bound on the lower mantle viscosity has implications for models employing a viscosity profile in the mantle, such as models for mantle convection and GIA, and inferences based on these models.

Inter-variable dependencies are key properties to characterise many climate phenomena - such as compound events - and their future changes. Yet, climate simulations often have statistical biases. Hence, univariate (1dBC) and multivariate bias correction (MBC) methods are regularly applied. Inter-variable properties (e.g., correlations) can be altered by BC corrections. Then, it is necessary to assess how hypotheses of BC methods on climate change affect the adjustments. This can lead to better choices of BC methods. Here, we investigate whether an MBC method should try reproducing, preserving or modifying the changes in rank correlations between daily temperature and precipitation over Europe. An original “perfect model experiment” is set up and applied to two different climate simulation ensembles over 2001-2100: 40 runs from the CESM global climate model and 11 runs from the CMIP6 exercise. The results highlight that, within the multi-run single GCM ensemble (CESM), accounting for correlation changes bring valuable information for long-term projections but that a stationary hypothesis provides less biased correlations, up to medium-term projections (2060). For the multi-model ensemble (CMIP6), the non-stationary hypothesis provides larger biases than the stationary approach, up to the end of the century. Not correcting the model rank correlations (1dBC) provides the worst results. Whenever an ensemble is available, the best results come from accounting for the “robust’ part of the change signal (i.e., average change from different runs). This pleads for using ensembles and their robust information, in order to perform robust bias corrections.

The cloud properties and governing processes in Southern Ocean marine boundary layer clouds have emerged as a central issue in understanding the Earth's climate sensitivity. While the simulated cloud feedbacks in Southern Ocean clouds have evolved in the most recent climate model intercomparison, the background properties of simulated summertime clouds in the Southern Ocean are not consistent with measurements due to known biases in simulating cloud condensation nuclei concentrations. This paper presents several case studies collected during the Capricorn 2 and Marcus campaigns held aboard Australian research vessels in the Austral Summer of 2018. Combining the surface-observed cases with MODIS data along forward and backward air mass trajectories, we demonstrate the evolution of cloud properties with time. These cases are consistent with multi-year statistics showing that long trajectories of air masses over the Antarctic ice sheet are critical to creating high droplet number clouds in the high latitude summer Southern Ocean. We speculate that secondary aerosol production via the oxidation of biogenically derived aerosol precursor gasses over the high actinic flux region of the high latitude ice sheets is fundamental to maintaining relatively high droplet numbers in Southern Ocean clouds during Summer.

Soil samples (n = 45) and water samples (n = 111) were collected in the coastal zone of SW Bangladesh in wet (November) and dry (May) seasons in 2016 to identify the factors influencing soil arsenic concentrations. Soils are entisols formed from recently deposited, predominantly silt-sized sediments with low carbon concentrations typical of the local mangrove forests. Arsenic concentrations in bulk soil are higher in November than in May and vary little between sites. Arsenic concentrations in deionized H2O extracts are ~2 orders of magnitude lower, indicating only ~1% of As is soluble. Water samples show that As concentrations are highest in groundwater from tubewells. Bulk soil As is positively correlated with As concentration in irrigation water, suggesting that As from irrigation water is added to the soil. Unlike other water types, As in rice paddy water is much higher in the wet season, consistent with some fields being irrigated with tubewell water. Arsenic in rice paddy water increases by soil sulfide dissolution, and decreases by dilution during the monsoon. Water soluble As in rice paddy soils is positively correlated with S and DOC concentrations in rice paddy soil extracts due to sulfide dissolution and complexation with DOC. Thus, waterlogging of rice paddy soils leads to reducing conditions, the absence of ferric oxyhydroxides that could sorb As, and the presence of sulfides that incorporate As. As soil pH increases from 7 to 8, KD(soil/extract) increases, consistent with the observed positive correlation between irrigation water pH and bulk soil As concentration. Arsenic bioavailability could be decreased through soil aeration (draining and tilling) and by avoiding the use of groundwater for rice paddy irrigation.

Understanding the falling velocity of cloud droplets and ice crystals in a nonuniform flow is fundamental to cloud physics and precipitation. In this study, the mean settling velocity of a hydrometeor falling into a non-stationary fluid is examined. To investigate the possible particle-fluid interaction, a homogeneous and isotropic turbulent flow fields is considered. The study covers a wide range of flow velocities and hydrometeor density and size. The results show initially reduction of hydrometeor settling velocity and then enhancement in strong turbulence. The mean settling velocity depends on a) mean flow and turbulent intensity i.e., standard deviation of flow and b) particle terminal velocity i.e., the shape and size of hydrometeor, its density, the dynamic viscosity and the density of the fluid, and the gravitational acceleration. The non-dimensional parameters that are important in characterization of hydrometeor settling velocities are estimated using dimensional analysis. These non-dimensional parameters are then used to formulate the mean settling velocity.

Declaration (Stauning, 2022) on “invalid PCS index” is based on the following arguments: PCS index is calculated with use of incorrect “unified” PC derivation method; PCS index used in analyses is a preliminary index, which was not approved by IAGA and, therefore, it cannot be regarded as a correct index; PCN and PCS indices demonstrate, intermittently, large difference in value, which should be treated as evidence of the PCS index invalidity. The paper presents comments to these arguments. Conclusion is made that criticism of the PCS index, presented in Stauning (2022), is based on groundless arguments.

The two seminal studies on westward intensification, carried out by Stommel and Munk over 70 years ago, are revisited to elucidate the role of the domain aspect ratio (i.e.~meridional to zonal extents of the basin) in determining the width and speed of a western boundary current (WBC). We examine the general mathematical properties of the two models by transforming them to differential problems that contain only two parameters — the domain aspect ratio and the non-dimensional damping (viscous) coefficient. Simple proxies of width and speed (and hence the transport that equals their product) of the WBC are derived from analytical solutions of the non-dimensional vorticity equations in the relevant region of the (damping, aspect ratio) parameter space. These analytically determined proxies are then benchmarked against numerical simulations of the corresponding time-dependent equations. In both models, the three proxies vary as a power law in the domain aspect ratio and in particular, the non-dimensional transport varies linearly with the domain aspect ratio.

Atmospheric methane mixing ratio rose by 15 ppbv between 2019 and 2020, the fastest growth rate on record. We conduct a global inverse analysis of 2019-2020 GOSAT satellite observations of atmospheric methane to analyze the combination of sources and sinks driving this surge. The atmospheric methane growth rate increased by 31 Tg a-1 from 2019 to 2020, representing a 36 Tg a-1 forcing on the methane budget away from steady state. 86% of the forcing in the base inversion is from increasing emissions (82 ± 18% in the 9-member inversion ensemble), and 14% is from decrease in tropospheric OH. Half of the increase in emissions is from Africa (15 Tg a-1) and appears to be driven by wetland inundation. There is also a large relative increase in emissions from Canada and Alaska (4.8 Tg a-1 , 24%) that could be driven by temperature sensitivity of boreal wetland emissions.

Meandering gravel-bed rivers tend to exhibit bed surface sorting patterns with coarse particles located in pools and fine particles on bar tops. The mechanism by which these patterns emerge has been explored in sand-bed reaches; however, for gravel-bed meandering channels it remains poorly understood. Here we present results from a flume experiment in which bed morphology, velocity, sediment sorting patterns, and bed load transport were intensively documented. The experimental channel is 1.35 meters wide, 15.2 meters long, and its centerline follows a sine-generated curve with a crossing angle of 20 degrees. Water and sediment input were held constant throughout the experiment and measurements were collected under quasi-equilibrium conditions. Boundary shear stress calculated from near-bed velocity measurements indicates that in a channel with mild sinuosity, deposition of fine particles on bars is a result of divergent shear stress at the inside bend of the channel, downstream of the apex. Boundary shear stress in the upstream half of the pool was below critical for coarse particles (>8 mm), leading to an armored pool. Inward directed selective transport was responsible for winnowing of fine particles in the pool. Fine and coarse sediment followed similar trajectories through the meander bend, which contrasts earlier studies of sand-bedded meanders where the loci of fine and coarse particles cross paths. This suggests a different sorting mechanism for gravel bends. This experiment shows that a complex interaction of quasi-equilibrium bed topography, selective sediment transport, and secondary currents are responsible for the sorting patterns seen in gravel-bed, meandering channels.

This work presents the results of a paleostress investigation in dated Mio-Pliocene volcanic rocks in the vicinity of the town of Lądek Zdrój in the Rychlebské hory Mts., as a part of the central Sudetic Mts. in the NE Bohemian Massif. Six different paleostress field regimes from the Late Miocene to Quaternary were distinguished. Each stress regime is characterized by the orientation of the principal parameters and is discussed in relation to the known paleostress regimes within the surrounding regions of the Sudetic Mts., Fore-Sudetic block, and European Alpine foreland in Central Europe. The results show switching of tectonic phases with dominant compression, transtension or extension. Moreover, the orientation of theoretical planes with maximum shear stress and with a high tendency to dilate for individual paleostress regimes is defined and compared with the orientation of known faults within the study area suggesting their possible kinematics. The timing of the derived regimes is determined more accurately and is in good accordance with the data reported from different regions in Central Europe, which suggests their broader validity. In addition, one event or shorter events interrupting the main Plio-Quaternary extensional regime and one differently oriented Plio-Quaternary extension regime were discovered and constrained based on several dated phases of the volcanism of the faulted rocks.

While temperature drop across the mantle’s basal thermal boundary layer (TBL) is likely $>$1000 K, the temperature anomaly of plumes believed to rise from that TBL is only up to a few hundred Kelvins. Reasons for that discrepancy are still poorly understood and a number of causes have been proposed. Here we use the ASPECT software to model plumes from the lowermost mantle and study their excess temperatures. We use a mantle viscosity that depends on temperature and depth with a strong viscosity increase from below the lithosphere towards the lower mantle, reaching about $10^{23}$ Pas above the basal TBL, consistent with geoid modelling and slow motion of mantle plumes. With a mineral physics-derived pyrolite material model, the difference between a plume adiabat and an ambient mantle adiabat just below the lithosphere is about two thirds of that at the base of the mantle, e.g. 1280 K vs.\ 835 K. 3-D models of isolated plumes become nearly steady-state >10-20 Myr after the plume head has reached the surface, with excess temperature drop compared to an adiabat for material directly from the CMB usually less than 100 K. In the Earth, plumes are likely triggered by slabs and probably rise preferrably above the margins of chemically distinct piles. This could lead to reduced excess temperatures, if plumes are more sheet-like, similar to 2-D models, or temperature at their source depth is less than at the CMB. Excess temperatures are further reduced when averaged over the plume conduit or melting region.

The correlation between surface displacements and groundwater level changes has been widely used to understand aquifer properties and their site characteristics; however, the underlying mechanism of various correlation types and influence of earthquakes has not been fully investigated. In this study, we examine correlations in Osaka and Kyoto, Japan, over 4 years including the period of the June 18, 2018, Mw 5.6 northern Osaka earthquake surface displacement from InSAR analyses and groundwater level monitoring data. Both positive and negative correlations were identified at groundwater level observation stations. Based on the different types of correlations, we propose a new conceptual aquifer model that drives the opposite interaction between the surface displacement and the groundwater level change. We further reveal that sites with negative correlations increased after the earthquake, suggesting that the earthquake increased the groundwater recharge rate as a result of increases in aquifer transportation properties such as permeability and porosity.

Urban Heat Island (UHI) effects have significant implications on the microclimatic conditions in urban environments, impacting human health, energy consumption, and overall urban planning. This study aims to assess the diurnal intensity of UHI in a microclimatic urban setting by adopting the Local Climate Zone (LCZ) classification approach. We utilized a combination of remote sensing data, ground-based measurements, and LCZ classification to analyze the temporal and spatial variation of UHI intensity throughout the day and night. The study area, Dehradun city, a densely populated urban area situated in the valley region of Himalayas, exhibited diverse LCZs, including compact low-rise, dense trees, and open spaces. Using satellite-derived land surface temperature (LST) data and hourly in-situ measurements, we quantified the UHI effect during daytime and nighttime hours. The results revealed distinct diurnal patterns of UHI intensity among different LCZs, with peak intensity occurring during late afternoon and early evening hours. Furthermore, we investigated the impact of vegetation and built-up characteristics on UHI variation, highlighting the cooling effect of green spaces and the amplifying effect of impervious surfaces. This research contributes to a better understanding of microclimatic urban environments and their relation to UHI dynamics, providing valuable insights for urban planners, policymakers, and researchers aiming to mitigate heat-related issues and promote sustainable urban development. The findings underscore the importance of considering local land-use patterns and urban morphology when assessing and managing UHI effects.