Fracture geometry, density, and distribution control fluid and thermal transport in low porosity rocks, as well as their seismic attributes. The creation of cracks throughout the matrix can result in large and disparate reductions in P- and S-wave velocities with negligible porosity development, which breaks the classic velocity-porosity relationship. Properly interpreting these signatures in seismic surveys from stimulated geothermal, oil, and gas reservoirs or seismogenic areas requires a rock physics model that uses realistic elastic properties of fractures. Conventional models for cracked rocks employ specific inclusion shapes such as spheroids with small aspect ratios. However, all these exhibit the same normal-to-shear compliance ratio -- regardless of aspect ratio -- and therefore impact the bulk and shear moduli in the same qualitative way. As such they are inadequate for describing many of the complementary evolutions of P- and S-wave velocities that transpire with the generation of cracks. Using a differential model of dimensionless compliances, we analyze published velocities for granite, basalt, and limestone to quantify typical compliance ratios and find that it is often different from that assumed in conventional crack models, which then affects crack density estimates. We also investigate how the total normal and shear compliances change due to certain thermo-hydro-chemo-mechanical processes that generate large crack densities, and conclude that the final ratios often still deviate from that of conventional models. Finally, we demonstrate how the model can be used to describe scatter in both P- and S-wave velocity-porosity trends. Implications for energy extraction and seismic monitoring are discussed.

A document by Mark Looper. Click on the document to view its contents.

Groups of pelagic dolphins and whales (order cetacea) regularly strand on beaches throughout the world and are referred to as mass stranding events (MSEs). MSEs have been observed for centuries, however the underlying causes remain unclear. We investigated possible connections between MSEs in Cape Cod Massachusetts, USA, and regional wind and ocean currents. The seasonal MSE distribution is strongly correlated to both wind and ocean current strengths, and correlation is maximized when MSEs are compared to environmental data one month in the past. Furthermore, a superposed epoch analysis (a Chree analysis) indicates significant shifts in ocean current strength for months surrounding MSEs. These results may indicate that atmospheric and oceanic effects are possible underlying factors influencing MSEs. These factors could generate environments conducive for prey assemblages that attract cetaceans, or perhaps by driving seasonal production of prey species.

The current paper investigates the shallow layers of the lunar regolith at the Chang'E-4 landing site. Four layers between 0-10 meters were identified using lunar penetrating radar. Based on these outputs, a revised stratigraphic model is suggested for the post-Imbrian ejecta at the Von Karman crater. The layers were previously unseen due to the smooth boundaries between them. The revised model was inferred using an advanced hyperbola-fitting scheme. Applying conventional hyperbola-fitting to non-homogeneous media results in errors and inaccuracies that are often wrongly assumed to be negligible. We propose a novel hyperbola-fitting scheme that is not constrained to homogeneous media and can be applied subject to any arbitrary one-dimensional permittivity distribution. Via this approach, we can estimate the permittivity profile of an investigated area and detect layered structures that were previously transparent to electromagnetic waves due to the gradational dielectric properties at their interfaces.

The close connection between the total lightning flash rate and storm updraft has been well recognized. In this study, we assessed the benefit of such a relationship in convective-scale data assimilation (DA) for model initialization. A lightning DA scheme to update model kinematic states was developed in the Weather Research and Forecasting Data Assimilation (WRFDA) three-dimensional variational (3DVar) system. This scheme combines total lightning observations with model-based prescribed vertical velocity profiles to retrieve kinematic information useful to DA. With the availability of space-borne lightning imagers in recent years, total lightning data observations from the Lightning Mapping Imager (LMI) on board the FY-4A geostationary satellite were assimilated in combination with radar DA. A detailed analysis of the impact of the lightning DA scheme on convective precipitation forecasting was conducted using a squall line case over Beijing on 13 July 2017. The results showed that the assimilation of LMI data further improves the analyses of dynamical conditions from assimilating radar radial winds. Although the microphysical states are identical due to the assimilation of reflectivity, updrafts directly form at lightning observation locations via lightning DA and hence improve the convective-scale dynamical balance. The quantitative verification of short-term convective forecasts indicated that the lightning DA adds value to current radar DA by improving the precipitation forecast skill. The new lightning DA scheme was further applied to a heavy rainfall case in 2018, and the results confirmed the effective and robust improvement in storm forecasting.

The plate tectonic history of the hypothesized ‘proto-South China Sea’ (PSCS) ocean basin and surrounding SE Asia since Cenozoic times is controversial. We implement four diverse PSCS plate reconstructions into global geodynamic models to constrain PSCS plate tectonics and possible slab locations. We consider: southward versus double-sided PSCS subduction models; earlier (Eocene) or later (late Oligocene) initiation of Borneo counterclockwise rotations; and, larger or smaller reconstructed Philippine Sea plate sizes. We compare our modeling results against tomographic images by taking into account mineralogical effects and the finite resolution of seismic tomography. All geodynamic models reproduce the tomographically-imaged Sunda slabs beneath Peninsular Malaysia, Sumatra and Java. Southward PSCS subduction produces slabs beneath present Palawan, northern Borneo, and offshore Palawan. Double-sided PSCS subduction combined with earlier Borneo rotations uniquely reproduces sub-horizontal slabs under the southern South China Sea (SCS) at ~400 to 700 km depths; these models best fit seismic tomography. A smaller Philippine Sea (PS) plate with a ~1000 km-long restored Ryukyu slab was superior to a very large PS plate. Taken together, the four end-member plate models predict PSCS slabs at <900 km depths under present-day Borneo, the SCS, the Sulu and Celebes seas, and the southern Philippines. Regardless of plate models, we predicted passive mantle upwellings under Indochina during late Eocene-Oligocene times, and downwellings under the SCS during the late Cenozoic that do not support a deep-origin ‘Hainan plume’. Modeled Sundaland dynamic topography depends strongly on the imposed plate model, varying by several hundred meters.

We explored the geological history of the Taurus-Littrow Valley at the Apollo 17 landing site through the induced thermoluminescence (TL) properties of regolith samples collected from the foothills of the Northern and Southern Massifs, near the landing site, and the deep drill core taken in proximity to the landing site. The samples were recently made available by NASA through the Apollo Next Generation Sample Analysis program, in anticipation of the forthcoming Artemis missions. We found that the two samples from the foothills of the massifs exhibit induced TL values approximately four times higher than those of the valley samples. This observation is consistent with their elevated plagioclase content, indicating their predominantly highland material composition. Conversely, the valley samples display induced TL values characteristic of lunar mare material. The samples from the deep drill core demonstrate uniform induced TL properties, despite originating from depths of up to 3 meters. Notably, one of the samples from the lower section of the deep drill core presents anomalous induced TL readings. This anomaly coincides with elevated levels of low-potassium KREEP, along with reduced quantities of anorthositic gabbro and orange glass, and could be due to the traces of phosphate minerals. Alternatively, this observation raises the possibility that this sample contains Tycho impact material. The induced TL data is consistent with the regolith, extending to a depth of at least 3 meters, having been deposited by a singular event approximately 100 million years ago. This timing aligns with the hypothesized formation of the Tycho crater.

Innovative groundwater management strategies are essential to preserve aquifers for crop irrigation. In western Kansas, USA, irrigators self-organized to extend the aquifer’s lifespan by self-imposing groundwater pumping limits enforced over a five-year period. While the five-year groundwater allocation period granted irrigators additional flexibility, it adds a new temporal dimension to their decision-making beyond the typical annual/sub-annual cropping and irrigation decisions. Pumping restrictions, along with uncertain precipitation, complicate multi-year farm planning. We formulated a two-stage stochastic modeling framework to design optimal annual cropping and irrigation allocations under pumping restrictions and uncertain precipitation. Optimal cropping and allocation strategies by the stochastic optimization model significantly outperform observed farmer strategies during the first two five-year LEMA periods (2013-2022) but only outperformed the optimal strategy by the deterministic optimization model assuming long-term average precipitation during drier conditions. We show that optimal cropping decisions shift from predominately corn to sorghum if more stringent pumping restrictions are imposed. Furthermore, irrigators are better off to use less water in the earlier years and saving more water for later years under more stringent five-year pumping restrictions, while they should use more of their allocation earlier under less stringent pumping limits. Extending the duration of the groundwater allocation window allows additional operational flexibility and enhances profits but the marginal gains for each additional year drop off after around seven years. Our versatile modeling framework is applicable to other regions considering groundwater pumping restrictions with the aim of balancing water conservation with farmer profitability and adaptability.

Equatorial Spread F (ESF), a manifestation of nighttime irregularities in the equatorial ionosphere has been linked to Atmospheric Gravity Waves (AGW) by different authors. However, there have not been much study to ascertain the extent of the relationship between the occurrence of AGW and the generation and occurrence of ESF. This study investigates the correlation between AGW and ESF occurrences during the year 2016, using data obtained with the aid of satellite borne Atmospheric Infrared Sounder (AIRS) and ionogram obtained with the aid of Digisonde Portable Sounder (DPS-4) located at Jicamarca, (geog. Lat. 11.95, Long. 76.87 and geomagnetic Lat. 9.28, Long.-7.92), an equatorial station in the Peruvian sector. During this period, 72.9% of AGW occurrence was observed between 18:00UT and 00:00UT (post-sunset period) while the remaining 27.1% occurrence was observed between 00:00 and 04:00UT (post-midnight period) coinciding with the period of occurrence of ESF. Results from the study reveal that the occurrences of ESF and AGW are independent of each other. An insignificant correlation (0.39) was found between the days of occurrence of the two phenomena. While ESF occurrence is a regular daily occurrence with local time dependence, AGW propagation is not dependent on local time. For Jicamarca, we found that ESF occurrence is greater during the solstice months than equinox. The probability of AGW reaching the bottomside F-layer depends on the properties of the wave. In this study, AGW was able to penetrate ionospheric heights on only six occasions. The results also show that AGW occurrence can only influence the conditions that trigger ESF rather than triggering ESF altogether. The occurrence of AGW tends to influence the occurrence of MSF type of ESF which is predominantly a post sunset phenomenon in preference to the other two types. Coefficient of correlation between AGW and MSF ranged between

Numerical experiments have revealed the importance of horizontal transport of light in the presence of clouds (“3D effects’), with consequences for climate, weather and solar resource availability predictions. Yet, atmospheric models continue to use 1D radiative transfer schemes. In this paper, we provide observational evidence for 3D effects. Observed direct and diffuse surface fluxes are compared to outputs from the ecRad radiative transfer scheme run on retrieved cloud profiles. The direct-beam calculation takes careful account of the field-of-view of the pyrheliometer to ensure consistency between observed and modeled direct fluxes. Only the solver that accounts for 3D effects is able to reproduce the observed mean direct–diffuse partition of surface fluxes as a function of solar zenith angle and cloud cover. This validates the physically-based model for 3D radiative processes included in ecRad. These results are in favor of a shift of paradigm from 1D to 3D radiation in large-scale models.

To improve current estimates of phytoplankton specific carbon in the Ross Sea, we calculated a regionally specific algorithm from in situ particulate organic carbon (POC) concentrations and backscatter sensor data. These data come from three independent Seaglider deployments during the austral summer. Algal-specific POC (Cphyto) accounted for between 19.8-61.0% of total POC in the Ross Sea with an average Cphyto concentration of 84.2 µg C L-1. As a result, Cphyto:chlorophyll a ratios were less than POC:chlorophyll a ratios and ranged from 9.00-257 µg C (µg chlorophyll a) L-1. This regionally-specific method is substantially more accurate (average Cphyto concentrations are 10-78 µg C L-1 greater) than estimates derived from published algorithms. Our findings highlight the value of regionally-specific algorithms for measuring inherent optical properties and how such approaches can inform our current understanding of particulate carbon partitioning and food web dynamics.

In forested, seasonally dry watersheds, winter rains commonly replenish water storage deficits in the vadose zone before recharging underlying hillslope groundwater systems that sustain streamflow. However, the relative inaccessibility of the subsurface has hindered efforts to include the role of storage deficits, primarily generated by plant-water uptake, in moderating groundwater recharge. Here, we compare groundwater recharge inferred from the storage-discharge relationship with independent, distributed estimates of vadose zone storage deficits across 12 undisturbed California watersheds, thereby tracking the evolution of the deficit-recharge relationship without intensive field instrumentation. We find accrued deficits during the dry season (driven by evapotranspiration) alone insufficiently explain differences in the wet season partitioning of rainfall due to the inter-storm behavior of the deficit during the subsequent wet season. Tracking the deficit at the storm event-scale within the wet season reveals a characteristic response in groundwater to increasing rainfall not captured in the seasonal analysis, and may improve estimates of the rainfall required to generate recharge and streamflow on a per-storm basis. Our findings demonstrate the potential for existing public datasets to better capture water partitioning within the subsurface using a combined deficit-recharge approach, though our analysis is currently limited to basins with select characteristics.

In this paper, the modifications of the whistler dispersion characteristics are investigated which arise if resonant electrons are taken into account. The following chain of processes is emphasized: Generation of whistler waves propagating at different angles to the magnetic field and their nonlinear interaction with resonant electrons result in the appearance of modulated electron beams in the background plasma. As a result, the dispersion characteristics of waves in this new plasma might be significantly changed. By solving the kinetic dispersion relation of whistler waves in electron plasmas with so-called beam/plateau (b/p) populations, the associated modifications of the whistler dispersion characteristics are presented in diagrams showing, in particular, the frequency versus propagation angle dependence of the excited waves. It is important to point out the two functions of the b/p populations. The interaction of the beam-shifted cyclotron mode ω = Ωe + k·Vb (Vb<0, Vb is the b/p velocity, Ωe: electron cyclotron frequency)) with the whistler mode leads to enhanced damping at the ω-k point where they intersect. This is the origin of the frequency gap at half the electron cyclotron frequency (ω~Ωe/2) for quasi-parallel waves which are driven by temperature anisotropy. Furthermore, it is shown that the upstream b/p electrons alone (in the absence of temperature anisotropy) can excite (very) oblique whistler waves near the resonance cone. The governing instability results from the interaction of the beam/plateau mode ω=k·Vb (Vb>0) with the whistler mode. Relations to recent and former space observations are discussed.

This paper investigates the potential of coupling Thermal Energy Storage (TES) with Advanced Reactors (ARs) to address uncertainties posed by climate change in deep decarbonized power systems. The TES Use-case Team at Idaho National Laboratory (INL) has examined the potential of storing thermal energy from ARs during low demand periods and optimizing discharge during peak-priced hours, in both steady-state and transient conditions.  Building on this groundwork, this study bridges the gaps in optimal sizing of the sub-system of TES-coupled AR systems using Risk Analysis Virtual Environment (RAVEN) and Holistic Energy Resource Optimization Network (HERON), INL’s framework for grid optimization. By applying this framework, we present statistically-robust optimal charge, discharge including balance of plant (BOP), and storage sizing for the High-Temperature Gas-Cooled Reactor (HTGR) with 203 MWth output. To this end, we generated synthetic price samples for 30 years using 2018 – 2021 real-time market data from ERCOT, PJM and MISO. Our results reveals that the TES-coupled HTGR system is highly effective in maximizing revenue from electricity sales. We observed a substantial increase of 40 % in ERCOT and a noteworthy 15 % increase in PJM and MISO when compared to the conventional BOP without TES. This improvement is achieved through regionally-tailored sub-system sizing, which ranges from 398 to 416 MWth for the discharge system and 610 to 1029 MWth for the TES. We find that the average electricity price directly impacts the overall economics, while price volatility influences storage size. Additional sensitivity analyses were performed to access the impact of key assumptions on system economics and sizing, differentiating the optimization window (i.e., 24 – 219 hours of chronological observations) and by imposing storage continuity condition in tracking TES cycles. We observed that at the 142-hour of the optimization window, a reasonable balance between computation time and accuracy was achieved. Our analysis also highlights the significance of conducting multi-day cycle analysis (> 120-hour) for TES to capture interaction between electricity prices and storage dynamics, providing a comprehensive understanding of TES behavior that AR developers should integrate into their plant designs.

To precisely describe the dynamics of vegetation cover in high-density urban areas, this study evaluates the spatial and temporal consistency of the Normalized Difference Vegetation Index (NDVI) from multiple satellite data sources. The study areas of Downtown Beijing target at two scales: the district scale, and the neighborhood scale. Results show that Planet, Sentinel-2, Landsat-8, and MODIS share a similar spatial pattern; Sentinel-2, Landsat-8, and MODIS correlate in the temporal change of NDVI at both spatial scales in 2019, but AVHRR does not present useful information of spatial patterns of urban green space or urban vegetation dynamics at these two scales. Seasonal contrast derived from Sentinel-2 and Landsat-8 can be visualized through seasonal variation ratio to assist urban green space planning. This study highlights the usefulness of existing satellite observations in monitoring a variety of urban greening typologies at the neighborhood scale for improving urban environmental planning.

Variability in the El Nino-Southern Oscillation has global impacts on seasonal temperatures and rainfall. Current detection methods for extreme phases, which occur with irregular periodicity, rely upon sea surface temperature anomalies within a strictly defined geographic region of the Pacific Ocean. However, under changing climate conditions and ocean warming, these historically motivated indicators may not be reliable into the future. In this work, we demonstrate the power of data clustering as a robust, automatic way to detect anomalies in climate patterns. Ocean temperature profiles from Argo floats are partitioned into similar groups utilizing unsupervised machine learning methods. The automatically identified groups of measurements represent spatially coherent, large-scale water masses in the Pacific, despite no inclusion of geospatial information in the clustering task. Further, temporal dynamics of the clusters are strongly indicative of El Nino events, the Pacific warming phase of the El Nino-Southern Oscillation. The unsupervised clustering task successfully identifies changes in the vertical structure of the temperature profiles through reassignment to a different group, concisely capturing physical changes to the water column during an El Nino event, such as tilting of the thermocline. Clustering proves to be an effective tool for analysis of the irregularly sampled (in space and time) data from ocean floats and may serve as a novel approach for detecting future anomalies given the freedom from thresholding decisions. Unsupervised machine learning approaches could be particularly valuable due to their ability to identify patterns in datasets without user-imposed expectations, facilitating further discovery of anomaly indicators.

A document by Carolina Hurtado-Pulido. Click on the document to view its contents.

Flow routing is a fundamental process of Earth System Models’ (ESMs) river component. Traditional flow routing models rely on Cartesian rectangular meshes, which exhibit limitations, particularly when coupled with unstructured mesh-based ocean components. They also lack the support for regionally refined models (RRMs). While previous studies have highlighted the potential benefits of unstructured meshes for flow routing, their widespread application and comprehensive evaluation within ESMs remain limited. This study extends the river component of the Energy Exascale Earth System Model (E3SM) to unstructured Voronoi meshes. We evaluated the model’s performance in simulating river discharge and water depth across three watersheds spanning the Arctic, temperate, and tropical regions. The results show that while providing several benefits, unstructured mesh-based flow routing can achieve comparable performance to structured mesh-based routing, and their difference is often less than 10%. Although the unstructured mesh-based method could address several existing limitations, this research also shows that additional improvements in the numerical method are needed to fully exploit the advantages of unstructured mesh for hydrologic and ESMs.