Kilometre Scale Research Articles

Recent progress in atmospheric modeling over the Andes – part I: review of atmospheric processes

The Andes is the longest mountain range in the world, stretching from tropical South America to austral Patagonia (12°N-55°S). Along with the climate differences associated with latitude, the Andean region also features contrasting slopes and elevations, reaching altitudes of more than 4,000 m. a.s.l., in a relatively narrow crosswise section, and hosts diverse ecosystems and human settlements. This complex landscape poses a great challenge to weather and climate simulations. The interaction of the topography with the large-scale atmospheric motions controls meteorological phenomena at scales of a few kilometers, often inadequately represented in global (grid spacing ∼200–50 km) and regional (∼50–25 km) climate simulations previously studied for the Andes. These simulations typically exhibit large biases in precipitation, wind and near-surface temperature over the Andes, and they are not suited to represent strong gradients associated with the regional processes. In recent years (∼2010–2024), a number of modeling studies, including convection permitting simulations, have contributed to our understanding of the characteristics and distribution of a variety of systems and processes along the Andes, including orographic precipitation, precipitation hotspots, mountain circulations, gravity waves, among others. This is Part I of a two-part review about atmospheric modeling over the Andes. In Part I we review the current strengths and limitations of numerical modeling in simulating key atmospheric-orographic processes for the weather and climate of the Andean region, including low-level jets, downslope winds, gravity waves, and orographic precipitation, among others. In Part II, we review how climate models simulate surface-atmosphere interactions and hydroclimate processes in the Andes Cordillera to offer information on projections for land-cover/land-use change or climate change. With a focus on the hydroclimate, we also address some of the main challenges in numerical modeling for the region.

Enhancing Atmospheric Monitoring Capabilities: A Comparison of Low- and High-Cost GNSS Networks for Tropospheric Estimations

Global Navigation Satellite System (GNSS) signals experience delays when passing through the atmosphere due to the presence of free electrons in the ionosphere and air density in the non-ionized part of the atmosphere, known as the troposphere. The Precise Point Positioning (PPP) technique demonstrates highly accurate positioning along with Zenith Tropospheric Delay (ZTD) estimation. ZTD estimation is valuable for various applications including climate modelling and determining atmospheric water vapor. Current GNSS network resolutions are not completely sufficient for the scale of a few kilometres that regional climate and weather models are increasingly adopting. The Centipede-RTK network is a low-cost option for increasing the spatial resolution of tropospheric monitoring. This study is motivated by the question of whether low-cost GNSS networks can provide a viable alternative without compromising data quality or precision. This study compares the performance of the low-cost Centipede-RTK network in calculating the Zenith Tropospheric Delay (ZTD) to that of the existing EUREF Permanent Network (EPN), using two alternative software packages, RTKLIB demo5 version and CSRS-PPP version 3, to ensure robustness and software independence in the findings. This investigation indicated that the ZTD estimations from both networks are almost identical when processed by the CSRS-PPP software, with the highest mean difference being less than 3.5 cm, confirming that networks such as Centipede-RTK could be a reliable option for dense precise atmospheric monitoring. Furthermore, this study revealed that the Centipede-RTK network, when processed using CSRS-PPP, provides ZTD estimations that are very similar and consistent with the EUREF ZTD product values. These findings suggest that low-cost GNSS networks like Centipede-RTK are viable for enhancing network density, thus improving the spatial resolution of tropospheric monitoring and potentially enriching climate modelling and weather prediction capabilities, paving the way for broader application and research in GNSS meteorology.

Deep vs shallow: GPS tags reveal a dichotomy in movement patterns of loggerhead turtles foraging in a coastal bay

BackgroundIndividual variation in movement strategies of foraging loggerhead turtles have been documented on the scale of tens to hundreds of kilometers within single ocean basins. Use of different strategies among individuals may reflect variations in resources, predation pressure or competition. It is less common for individual turtles to use different foraging strategies on the scale of kilometers within a single coastal bay. We used GPS tags capable of back-filling fine-scale locations to document movement patterns of loggerhead turtles in a coastal bay in Northwest Florida, U.S.A.MethodsIridium-linked GPS tags were deployed on loggerhead turtles at a neritic foraging site in Northwest Florida. After filtering telemetry data, point locations were transformed to movement lines and then merged with the original point file to define travel paths and assess travel speed. Home ranges were determined using kernel density function. Diurnal behavioral shifts were examined by examining turtle movements compared to solar time.ResultsOf the 11 turtles tagged, three tracked turtles remained in deep (~ 6 m) water for almost the entire tracking period, while all other turtles undertook movements from deep water locations, located along edges and channels, to shallow (~ 1–2 m) shoals at regular intervals and primarily at night. Three individuals made short-term movements into the Gulf of Mexico when water temperatures dropped, and movement speeds in the Gulf were greater than those in the bay. Turtles exhibited a novel behavior we termed drifting.ConclusionsThis study highlighted the value provided to fine-scale movement studies for species such as sea turtles that surface infrequently by the ability of these GPS tags to store and re-upload data. Future use of these tags at other loggerhead foraging sites, and concurrent with diving and foraging data, would provide a powerful tool to better understand fine-scale movement patterns of sea turtles.

Lateral heterogeneity of basin‐plain turbidites of the Cloridorme Formation, Quebec, Canada: Implications for horizontal well prediction

AbstractFacies models for basin‐plain turbidite systems often depict very simplistic event‐bed geometries that are tabular at the kilometre scale. However, recent studies have demonstrated more complex facies architectures, including rapid changes in event‐bed thickness and facies composition. This lateral event‐bed heterogeneity can have a significant impact on reservoir heterogeneity prediction in basin‐plain turbidite systems developed for hydrocarbon production, carbon sequestration or geothermal energy. Coastal outcrops on the Gaspé Peninsula in Quebec expose the Middle Ordovician Cloridorme Formation, a synorogenic ‘flysch’ turbidite system developed in the Taconic foreland basin. The formation is interpreted to occupy a basin‐floor position due to long‐distance (tens of kilometres) correlations of bedsets in the direction of palaeocurrent. This outcrop‐based study of the Cloridorme Formation utilises drone photogrammetry, centimetre‐scale graphic logs and handheld gamma ray scintillometry data to better understand the detailed turbidite and hybrid event‐bed architecture in a basin‐plain setting. While most beds in this outcrop study can be traced for 500 m or more in a downcurrent direction, these results indicate significant intra‐bed and inter‐bed lateral complexity, including changes in bed thickness, grain‐size distribution and mud content. The quantification of these lateral changes and comparison with other well‐constrained outcrop analogues refines the environment of the Cloridorme Formation and aids in the prediction of subsurface heterogeneity in conventional and unconventional hydrocarbon reservoir systems through reservoir model parameterisation, as well as the characterisation of lateral heterogeneity important for horizontal‐well geosteering and completion strategies.

WindSeer: real-time volumetric wind prediction over complex terrain aboard a small uncrewed aerial vehicle

Real-time high-resolution wind predictions are beneficial for various applications including safe crewed and uncrewed aviation. Current weather models require too much compute and lack the necessary predictive capabilities as they are valid only at the scale of multiple kilometers and hours – much lower spatial and temporal resolutions than these applications require. Our work demonstrates the ability to predict low-altitude time-averaged wind fields in real time on limited-compute devices, from only sparse measurement data. We train a deep neural network-based model, WindSeer, using only synthetic data from computational fluid dynamics simulations and show that it can successfully predict real wind fields over terrain with known topography from just a few noisy and spatially clustered wind measurements. WindSeer can generate accurate predictions at different resolutions and domain sizes on previously unseen topography without retraining. We demonstrate that the model successfully predicts historical wind data collected by weather stations and wind measured by drones during flight.

Unraveling microbial community structure–function relationships in the horizontal and vertical spatial dimensions in extreme environments

A fundamental challenge in soil macroecology is to understand how microbial community structure shapes ecosystem function along environmental gradients of the land surface at broad spatial scales (i.e. the horizontal dimension). However, little is known about microbial community structure–function relationships in extreme environments along environmental gradients of soil depth at finer spatial scales (i.e. the vertical dimension). Here, we propose a general spatial dimension partitioning approach for assessing the patterns and drivers of soil microbial community structure–function relationships across horizontal and vertical spatial gradients simultaneously. We leveraged a 200‐km desert soil salinity gradient created by a 12‐year saline‐water irrigation in the Tarim basin of Taklamakan Desert. Specifically, using a general linear model, hierarchical variance partitioning, and a path model, we assessed the patterns and key ecological processes controlling spatial turnover in microbial community structure (i.e. β‐diversity) and enzymatic activity relevant to carbon, nitrogen, and phosphorus cycling along soil salinity gradients across study sites (horizontal dimension) and soil depths (vertical dimension). We found a decoupled relationship between soil microbial β‐diversity and enzymatic activity. Differences in soil depth (on the scale of meters) were as important as geographic distance (on the scale of kilometers) in shaping bacterial and fungal β‐diversity. However, the vertical and horizontal turnover in enzymatic activity was largely attributed to an increase in the heterogeneity of soil properties, such as soil texture, water content, and pH. Our findings suggest that dispersal limitation controls microbial community β‐diversity and that environmental heterogeneity, rather than soil salinization, controls enzymatic activity. Taken together, this work highlights that in the face of ongoing environmental alterations, soil depth is an under‐explored spatial dimension that must be considered in soil conservation efforts as a critical factor in determining microbial community structure and function in extreme environments.

Estimation and usefulness of measurement uncertainty from sampling at different spatial scales: microns to kilometres

Uncertainty of measurement values (MU) is crucial to their reliable geochemical interpretation. MU can be estimated using the Duplicate Method, which requires the taking of a small proportion of duplicated samples, and can be applied at any spatial scale. The distance between the duplicated samples is selected to reflect the effect of analyte heterogeneity on the measurement result (i.e. estimated concentration) within each sampling target, at the particular scale of investigation. Three published case studies, at different spatial scales, are used to explain how the Duplicate Method can be applied to estimate MU. They also illustrate how MU can be used to improve geochemical interpretation and validate measurement procedures (that include sampling) by judging their fitness for purpose. At the kilometre scale, measurements from the GEMAS survey of agricultural soils across Europe are used to estimate their MU for the first time. The MU for 53 elements range from an uncertainty factor of 1.01 to over 10. The MU contributes more that 20% to the total variance for 8 of the 53 elements, showing that the measurement procedure was not fit for purpose in those cases. At the micron scale, measurements of oxygen isotopes in candidate quartz reference materials had MU that was dominated by its sampling component, caused by sometimes unacceptable heterogeneity. A third case study of Pb in soils at 12 UK sites showed that the Duplicate Method can also be used to quantify the heterogeneity (as factor 1.03 to 2.4), and that it can indicate different possible sources of an element.

Effects of soil moisture variations on the neutron spectra measured above ground: feasibility of a soil moisture monitor system based on neutron moderating cylinders

Mapping the soil moisture is a key activity in water management and sustainable agriculture, especially in regions characterised by fragile agri-food systems and water scarcity. Cosmic Ray Neutron Sensors (CRNS) is a contactless nuclear technology used for estimating soil moisture (SM) content on a 20–30 m scale at the landscape level. Very interestingly, this corresponds to the so-called intermediate scale gap between the local probes, operating on the meter scale, and the satellite-based technologies, working on the kilometre scale and above. In state-of-art CRNS, the cosmic neutrons degraded by the soil are simply counted by a slightly moderated thermal neutron counter. After a calibration procedure, the SM is inferred by combining this count rate with environmental parameters: the atmospheric pressure, temperature and the air humidity. As the SM affects not only the environmental neutron fluence rate but also its energy distribution, this study was organised in such a way to understand if a CRNS with spectrometric capabilities could provide improved information on the SM distribution. To this aim, an environmental neutron spectrometer was designed by extending the Bonner Spheres to a more sensitive system made of moderating cylinders embedding long BF3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ _3 $$\\end{document} proportional counters, the Moderating Cylinders Spectrometer (MCS). Relying on literature environmental neutron spectra, corresponding to different SM values in a standardised soil, the count rates in the MCS were calculated for different values of SM. To simulate various counting scenarios, these count rates were associated to different levels of “realistic” uncertainties and unfolded by means of the FRUIT code. The resulting neutron spectra are compared to the literature ones, allowing at estimating the resolving power of the spectrometer in terms of SM.

Mitigating the impact of dense vegetation on the Sentinel-1 surface soil moisture retrievals over Europe

ABSTRACT The C-band Synthetic Aperture Radar (SAR) on board of the Sentinel-1 satellites have a strong potential to retrieve Surface Soil Moisture (SSM). Using a change detection model to Sentinel-1 backscatter, an SSM product at a kilometre scale resolution over Europe could be established in the Copernicus Global Land Service (CGLS). Over areas with dense vegetation and high biomass. The geometry and water content influence the seasonality of the backscatter dynamics and hamper the SSM retrieval quality from Sentinel-1. This study demonstrates the effect of woody vegetation on SSM retrievals and proposes a masking method at the native resolution of Sentinel-1’s Interferometric Wide (IW) swath mode. At a continental 20 m grid, four dense vegetation masks are implemented over Europe in the resampling of the backscatter to a kilometre scale. The resulting backscatter is then used as input for the TUWien (TUW) change detection model and compared to both in-situ and modelled SSM. This paper highlights the potential of high-resolution vegetation datasets to mask for non-soil moisture-sensitive pixels at a sub-kilometre resolution. Results show that both correlation and seasonality of the retrieved SSM are improved by masking the dense vegetation at a 20 m resolution.

Attitude Determination of Photovoltaic Device by Means of Differential Absorption Imaging

Future wireless power transmission will cover power levels up to kilowatts or more and transmission distances up to the scale of kilometers. With its narrow beam divergence angle, optical wireless power transmission (OWPT) is a promising candidate for such system implementations. In the operation of OWPT, it is necessary to estimate the position, direction (azimuth, elevation), and attitude of the target photovoltaic device before the power supply. The authors have proposed the detection of targets using differential absorption imaging and positioning with a combination of stereo imagery. In the positioning by stereo imagery, a condition regarding the consistency of the left and right images can be defined. This corresponds to the certain value of the exposure time of the image sensor, and this depends on the target’s attitude angle. In this paper, we discuss target attitude estimation using this minimum exposure time at which the integrity measure converges. A physical model was derived under general conditions of target position and experimental configuration. Target attitudes were estimated within an error range of 10 to 15 degrees in approximately 60 degrees range. On the other hand, there is an attitude estimation method based on the apparent size of the target. When using this method to estimate the attitude angle, errors are significantly large for specular and diffuse mixed targets like the PV. The method proposed in this paper is a robust attitude estimation method for the photovoltaic device in OWPT.

Modelling and inferring fracture curvature from borehole GPR data: A case study from the Bedretto Laboratory, Switzerland

AbstractFracture curvature has been observed from the millimetre to the kilometre scales. Nevertheless, characterizing curvature remains challenging due to data sparsity and geometric ambiguities. As a result, most numerical models often assume planar fractures to ease computations. To address this limitation, we present a novel approach for inferring fracture geometry from travel‐time data of electromagnetic or seismic waves. Our model utilizes co‐kriging interpolation of control points in a three‐dimensional surface mesh to simulate fracture curvature effectively, resulting in an unstructured triangular grid. We then refine the fracture surface into a structured grid with equidistant elements so that both small‐scale heterogeneities and large‐scale curvature can be modelled. To constrain the fracture geometry, we perform a deterministic travel‐time inversion to optimally place these control points. We validate our methodology with synthetic data and address its limitations. Finally, we infer the geometry of a large (more than 200 m) fracture observed in single‐hole ground‐penetrating radar field data. The fracture surface closely agrees with borehole televiewer observations and is also constrained far from the boreholes. Our modelling approach can be trivially adapted to multi‐offset ground‐penetrating radar or active seismic data.

Quantifying the spatial inhomogeneity of ice concentration in mixed-phase stratiform cloud using airborne observation

The distribution of ice particles strongly affects the microphysical processes in mixed-phase clouds, but the inhomogeneity of ice distribution is not well understood. In this paper, based on airborne in-situ measurements from three flights on May 31, 2021 in Hulun Buir, China, the inhomogeneity and clustering of ice distribution in a stratiform cloud is quantitatively analyzed using the pair correlation function (PCF). The results show that ice clusters on scales of a few kilometers dominate the inhomogeneity of the ice distribution. Due to the cumulative impact of ice clusters on different scales, the probability of finding relative high ice concentration within a lag of 80 m can be enhanced by 0.1 to 3.5 times. On average, the scale of ice cluster is ∼100 m for a sampling distance of 1 km, and increases to 3.2 km for a sampling distance of 20 km. It is also found that the ice growth is not fast enough to cluster the ice water content (IWC), and the inhomogeneity of IWC is strongly influenced by ice generation in addition to ice growth in the observed cloud. The results are helpful to better understand the distribution of ice in mixed-phase cloud, and provide potentially important information to improve the parameterizations of microphysics in models.

Water isotopic characterisation of the cloud–circulation coupling in the North Atlantic trades – Part 1: A process-oriented evaluation of COSMOiso simulations with EUREC4A observations

Abstract. Naturally available, stable, and heavy water molecules such as HDO and H218O have a lower saturation vapour pressure than the most abundant light water molecule H216O; therefore, these heavy water molecules preferentially condense and rain out during cloud formation. Stable water isotope observations thus have the potential to provide information on cloud processes in the trade-wind region, in particular when combined with high-resolution model simulations. In order to evaluate this potential, nested COSMOiso (isotope-enabled Consortium for Small Scale Modelling; Steppeler et al., 2003; Pfahl et al., 2012) simulations with explicit convection and horizontal grid spacings of 10, 5, and 1 km were carried out in this study over the tropical Atlantic for the time period of the EUREC4A (Elucidating the role of clouds-circulation coupling in climate; Stevens et al., 2021) field experiment. The comparison to airborne in situ and remote sensing observations shows that the three simulations are able to distinguish between different mesoscale cloud organisation patterns as well as between periods with comparatively high and low rain rates. Cloud fraction and liquid water content show a better agreement with aircraft observations with higher spatial resolution, because they show strong spatial variations on the scale of a few kilometres. A low-level cold-dry bias, including too depleted vapour in the subcloud and cloud layer and too enriched vapour in the free troposphere, is found in all three simulations. Furthermore, the simulated secondary isotope variable d-excess in vapour is overestimated compared to observations. Special attention is given to the cloud base level, which is the formation altitude of shallow cumulus clouds. The temporal variability of the simulated isotope variables at cloud base agrees reasonably well with observations, with correlations of the flight-to-flight data as high as 0.7 for δ2H and d-excess. A close examination of isotopic characteristics under precipitating clouds, non-precipitating clouds, clear-sky and dry-warm patches at the altitude of cloud base shows that these different environments are represented faithfully in the model with similar frequencies of occurrence, isotope signals, and specific-humidity anomalies as found in the observations. Furthermore, it is shown that the δ2H of cloud base vapour at the hourly timescale is mainly controlled by mesoscale transport and not by local microphysical processes, while the d-excess is mainly controlled by large-scale drivers. Overall, this evaluation of COSMOiso, including the isotopic characterisation of different cloud base environments, suggests that the simulations can be used for investigating the role of atmospheric circulations on different scales for controlling the formation of shallow cumulus clouds in the trade-wind region, as will be done in part 2 of this study.

Short-term habituation of the longfin squid (Doryteuthis pealeii) to pile driving sound

Abstract Offshore windfarms are a key renewable solution to help supply global energy needs. However, implementation has its challenges, including intense pile driving sound produced during constructions, which can affect marine life at the individual level, yet impacts at the group level remain poorly studied. Here, we exposed groups of longfin squid (Doryteuthis pealeii) in cages at multiple distances from consecutive pile driving events and sought to quantify responses at both individual and group levels. Pile driving induced short-term alarm responses at sound levels (in zero-peak) of 112–123 dB re 1 µm s−2 that were similar to those measured at kilometre scale from offshore windfarm constructions. The rate of individual alarm responses quickly decreased both within and across consecutive pile driving events, a result consistent with previous laboratory studies. Despite observing dramatic behavioural changes in response to initial pile driving sound, there were no significant differences in squid shoaling areas before and during exposure, showing no disruption of squid collective behaviours. Our results demonstrate rapid habituation of squid to pile driving sound, showing minimal effects on this ecologically and commercially key taxon. However, future work is now needed to assess responses of wild squid shoals in the vicinity of offshore windfarm constructions.

Fractures in glaciers—Crack tips and their stress fields by observation and modeling

AbstractHigh‐resolution optical camera systems are opening new opportunities to study fractures in ice. Here, we present data obtained from the Modular Aerial Camera System camera system operated onboard of Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) polar aircraft in northeast Greenland in 2022. In addition, we are using optical and radar satellite imagery. The study area is the 79°N Glacier (Nioghalvfjerdsbræ, 79NG), an outlet glacier of the Northeast Greenland Ice Stream. We found that crack tips are exhibiting additional isolated cracks ahead of the main crack. Subsequent crack propagation is starting from those isolated cracks, leading to an advance of the crack, with bridges between crack faces. The bridges provide information of the episodic crack propagation. Fractures have typically a length scale of kilometers and the distance of crack faces is in the order of meters to tenths of meters. Fracture modes will be inferred from stress fields computed by an inverse modeling approach using the Ice Sheet and Sea Level System Model. To this end, a surface velocity field derived from satellite remote sensing is used for the optimal control method that constrains model parameters, for example, basal friction coefficient or rheology.

Towards improving short-term sea ice predictability using deformation observations

Abstract. Short-term sea ice predictability is challenging despite recent advancements in sea ice modelling and new observations of sea ice deformation that capture small-scale features (open leads and ridges) at the kilometre scale. A new method for assimilation of satellite-derived sea ice deformation into numerical sea ice models is presented. Ice deformation provided by the Copernicus Marine Service is computed from sea ice drift derived from synthetic aperture radar at a high spatio-temporal resolution. We show that high values of ice deformation can be interpreted as reduced ice concentration or increased ice damage – i.e. scalar variables responsible for ice strength in brittle or visco-plastic sea ice dynamical models. This method is tested as a proof of concept with the neXt-generation Sea Ice Model (neXtSIM), where the assimilation scheme uses a data insertion approach and forecasting with one member. We obtain statistics of assimilation impact over a long test period with many realisations starting from different initial times. Assimilation and forecasting experiments are run on synthetic and real observations in January 2021 and show increased accuracy of deformation prediction for the first 3–4 d. Similar conclusions are obtained using both brittle and visco-plastic rheologies implemented in neXtSIM. Thus, the forecasts improve due to the update of sea ice mechanical properties rather than the exact rheological formulation. It is demonstrated that the assimilated information can be extrapolated in space – gaps in spatially discontinuous satellite observations of deformation are filled with a realistic pattern of ice cracks, confirmed by later satellite observations. The limitations and usefulness of the proposed assimilation approach are discussed in a context of ensemble forecasts. Pathways to estimate intrinsic predictability of sea ice deformation are proposed.

Variations and causes of in-situ stress orientations in the Dibei-Tuziluoke Gas Field in the Kuqa Foreland Basin, western China

The Kuqa Foreland Basin, adjacent to the southern Tianshan Mountains, is an important gas-producing basin in northwestern China. The development of the basin is dominated by a regional stress field with orientations of the maximum horizontal stress (SHmax) in the north-south direction, as a result of the collision between the Indian and Eurasian Plates. Previous studies have noted variations in the stress state in the Kuqa Foreland Basin; however, little attention has been paid to understanding the mechanisms causing such variations. In this study, a systematic analysis of in-situ SHmax orientations and fractures has been carried out using image logs from eight wells and XMAC/DSI logs from five wells. These wells are located in an East-West (E-W) trending fold-thrust in the foreland basin. The SHmax orientations (having quality ranked between A and D) obtained from borehole breakouts and drilling-induced fractures are highly variable and occur as two evidently different stress patterns on a scale of less than 10 km. The first stress pattern with SHmax orientations between NNW and NNE (165.08 and 188.59 °N) is broadly comparable to the regional stress field inferred from earthquake focal mechanism solutions in northwestern China from the World Stress Map (WSM). The stress pattern is interpreted to be controlled by plate boundary forces related to the collision between the Indian and Eurasian Plates. The SHmax orientations for the second stress pattern, however, ranging from NNE to ENE (26.65–57.77 °N), are clearly inconsistent with the regional stress filed and have been influenced by local geological factors. Faults and hinge-parallel fractures (trending in an approximately W-E direction) formed during the syn-folding stage probably resulted in heterogeneity of elastic properties and thus deflected SHmax orientations, both laterally and vertically, to generate the second stress pattern. The NE-striking hinge-oblique fractures are interpreted to have formed in response to the stress reorientation. Observations in this study suggest that there may exist a close relationship between fracturing (faulting) and stress variations, and pre-existing faults and fractures can influence subsequent fracturing by regulating local stress fields on a scale of several kilometers. The coupling between fracturing or faulting and stress produced fracture swarms, which can significantly enhance fluid flow and hence petroleum production.

Geological characterization and controlling factors of small-scale variations in the cobalt-rich ferromanganese crust deposits

Cobalt-rich ferromanganese crusts (CRC) are potential resources for Co, Ni, Pt, and other strategic metals. The CRC thickness varies from a few mm to more than 100 mm at various distance scales over the rock outcrops in the seamounts. However, their variation patterns and controlling factors are not well understood. We conducted a comprehensive small-scale survey, including shipboard acoustic measurements, seafloor observations, and rock drilling over the Xufu Guyot of the Marcus-Wake seamounts in the Northwestern Pacific to characterize the thickness variations on a scale of several kilometers with the topography and geological evolution of the guyot. Rock drilling revealed that thicker CRC (>100 mm) tend to occur on the margins and flat areas on the guyot, while thinner CRC are associated with carbonate reef mounds over the volcanic pinnacles and seamount slopes. The microstratigraphic description indicated that the CRC thickness is strongly related to the geological evolution of the guyot, mainly the stability of the substrate rocks and coverage with calcareous pelagic sedimentation.

A turbulent orographic form drag scheme accounting for anisotropy and orientation for kilometer‐ to subkilometer‐scale models

AbstractThis paper presents a turbulent orographic form drag (TOFD) parameterization scheme that takes into account the directional effects stemming from the angle between the low‐level wind and the principal axis of small‐scale orography. Suitable for models with both kilometer and subkilometer horizontal resolutions, this scheme builds upon prior theoretical and numerical studies to formulate surface TOFD based on the slope and direction of the sinusoidal hills. In this study, we proposed a straightforward function to calculate the surface TOFD for various orographic aspect ratios and directional parameters. The vertical decay of the drag is modeled with a scale twice the standard deviation of the sub‐grid orography. A comparison with numerous large‐eddy simulations featuring a single ellipsoidal hill demonstrates that our scheme effectively captures the dependence of drag on factors such as maximum slope, aspect ratio, the angle between low‐level wind and the principle axis, and hill height. We recommend calculating the sub‐grid orographic parameters using a well‐established method and digital terrain elevation data with a horizontal resolution less than a 100 m. This will allow for representation on orographic scales of both kilometers and subkilometers. Real‐case numerical weather prediction tests are conducted and verified with dense surface wind observations. The proposed scheme improves surface wind simulation compared to a renowned TOFD scheme, and also effectively exhibits the wind response to orographic anisotropy.

Cyclostratigraphy at a tipping point

There are key patterns of variation in the (litho‐) stratigraphical record, which, with advances in computing technology in recent decades, have become amenable to objective numerical analysis. This research has chiefly focused on the search for spatially regular cycles in the sedimentary rock record, since there are theoretical grounds for believing that these would be periodic and thus provide a means of time‐calibrating the stratigraphical records in which they occurred. Less popular lines of research consider the scaling relationships of the tangible, measurable sedimentary rock layers, and of the hiatuses, individually of indeterminate length, that punctuate these layers. Objective source data for all these analyses is provided, on limited (usually decametre) scales, by detailed lithological logging, sampling and dating of sections provided by exposures and cores. An objective global lithostratigraphical database, with larger, kilometre scales, is provided by the widespread practice of electric (wire‐line) logging of deep wells. This involves measurement, at 6‐inch (~15 cm) depth intervals of lithology‐related petrophysical properties. Rapid desk top computer analysis of the hundreds or thousands of readings that comprise these two data series, searches for patterns of variation. This review considers the published evidence for ‘ubiquitous’ cyclicity and its use in chronostratigraphy, despite the contrary claims that stratigraphical records are predominantly random in character.