A mathematical model is considered for Rayleigh-Benard convection of mantle whose viscosity depends strongly both on temperature and pressure defined in an Arrhenius form. The model is solved numerically for extremely large viscosity variations across a unit aspect ratio cell, and steady solutions are obtained. To improve the efficiency of numerical computation, a modified viscosity law with a low temperature cut-off is used. The aim is to investigate the convection pattern with internal heating at a very high viscosity variation in the presence of high Rayleigh number. The study also investigates the relation between temperature-dependent parameter and pressure dependent parameter. The numerical simulation is done using the finite element method based PDE solver and the results are presented through figures, tables and graphs.

Global warming is expected to increase global mean precipitation by 2-4%/K, but this increase may be very uneven, leading to more flooding but also droughts. Utilizing the Gini index, a metric frequently used in economics, we analyze the unevenness of precipitation distribution locally and globally from daily to annual-mean timescale in CMIP6 global warming simulations. The unevenness of daily precipitation increases in all models over land and ocean, tropics and extratropics. Local-daily precipitation unevenness changes show a complex geographic pattern. However, particularly over land, we show that a simple theoretical scaling explains this complexity to result from increased precipitation intensity scaling at about the Clausius-Clapeyron rate, and a local balance between changes in time-mean precipitation and dry-day fraction. These results provide a novel perspective on the relation between global constraints on hydrological cycle to regional precipitation changes independent of changes in the quasi-stationary atmospheric circulation and geographic distribution of precipitation.

ANCHOR is a novel data assimilation model developed at the U.S. Naval Research Laboratory for nowcasting ionospheric parameters relevant to space weather applications. ANCHOR incorporates electron density observations from ionosondes, Abel inverted radio occultation data, and ground-based GNSS receivers data into a PyIRI driven model background using the Kalman filter technique. The purpose of this study is to validate the estimated model parameters with direct electron density observations from incoherent scatter radars (ISR) at various levels of solar activity. A six year dataset spanning from 2018 to 2024, has been collected from four operating ISRs located at varying latitudes left of the prime meridian: Arecibo, Jicamarca, Millstone Hill, and Poker Flat. The validation includes four distinct events, with two events at low solar activity, one at moderate, and one at high solar activity, each with data coverage from at least two radars. Parameter extraction is achieved using Epstein functions to derive the bottom and topside of the F2 layer after the peak density (NmF2) and altitude (hmF2) have been found. The ISR-extracted parameters are used to directly compare with the model outputs using the root mean square error (RMSE) analysis method. Up to 75% improvement relative to the background model for NmF2 and hmF2 parameters with consistency across all latitudes is found. Additionally, ANCHOR assimilative model was compared to PyIRTAM model, showing a good agreement between the performances of both systems.

High-frequency gravity waves (HFGWs) observed by the Zhurong/Tianwen-1 and Perseverance/Mars 2020 rovers between 09:00 and 11:00 local time, from Ls 140° to 165° in Mars Year 36 was investigated. By analyzing the eccentricity of hodographs for monochromatic wind perturbations obtained from harmonic fittings, HFGWs were identified via their predominantly linear characteristics. The background atmosphere stability was estimated using the Richardson number from the Dynamic Meteorology Laboratory general circulation model simulation. We find that the frequency of HFGWs doubled following the onset of a regional dust storm (RDS) in the Utopia Planitia region, where the Zhurong rover landed. The propagation directions of the HFGWs were determined using their polarization relationships. The HFGWs observed by Zhurong predominantly propagated north-south direction before the RDS and then east-west after. The propagation direction changes were likely due to the atmospheric instability changes in the region before and after the storm.

A document by Michael A. Chavez. Click on the document to view its contents.

The observed warming in the Western Mediterranean (WMed) region over recent decades is projected to continue, outpacing the global average, making the region a prominent climate change hotspot. Even within this relatively small area, the combination of natural climate variability and anthropogenic climate change creates significant spatial variation in extreme climate events. This study analyzes temperature and precipitation trends in the WMed using ECMWF Reanalysis v5 (ERA5) data from 1951 to 2020 taking into consideration the climatic heterogeneity of the region. A non-hierarchical K-Means clustering method was applied to delineate nine climatically homogeneous regions within the WMed. A timescale decomposition analysis was then conducted to disentangle long-term, decadal, and interannual variability components of seasonal data. Results indicate that long-term trends explain most of the total observed variance in temperature (~65%), while interannual natural variability dominates observed precipitation (~60%). These patterns vary seasonally, with the strongest warming trends along the Mediterranean coast of the Iberian Peninsula and northern Africa in summer and the most significant drying trends in the southwestern Mediterranean during both summer and winter. The influence of different modes of natural climate variability in the observed trends is assessed and appears to contribute to winter drying, but no evidence was found of its influence on warming trends. This study lays a foundation for future climate change detection and attribution efforts in the WMed, emphasizing the need for sub-regional analysis due to the region’s pronounced heterogeneity.

• Arctic marine ecosystems experience enhanced climate stressors with differences over time and space and among models. • Trend magnitudes are projected to further increase over time for temperature increases and oxygen declines. • SSP2-4.5 emissions can avoid calcite undersaturation before 2100, but few regions can avoid aragonite undersaturation.

Landfills require extensive aftercare to safeguard human health and the environment. This involves monitoring emissions like leachate and gas, maintaining cover layers, and managing leachate and gas collection systems. Researchers have explored methods to conclude or extend aftercare. Experimental programs in the Netherlands are testing stabilization techniques for landfill waste bodies. Quantifying emission potential, a key concept integrating various processes influencing emissions, is essential for managing and predicting landfill impacts. In this study we developed a stochastic travel time model based on water life expectancies. The model is used to predict leachate production rates and leachate chloride concentrations from landfill waste bodies. We present new data for long-term time series of leachate production and leachate quality for four different waste bodies in the Netherlands. Unknown parameters are quantified by matching model output to measured time series using Bayesian inference. Once parameter distributions have been obtained, we are able to describe the measured long-term leachate dynamics. By analyzing the parameters and evolution of model states, we obtain a deeper understanding of the water and mass balance of the waste bodies. We demonstrate that the model can be used to quantify the emission potential and the estimated values of total mass match data quantified by sampling from the waste body. The results confirm that emissions with leachate are dominated by preferential flow infiltrating from the cover layer. Similar results have been obtained by applying the model to datasets from four different waste bodies, demonstrating that the approach is generally applicable.

Solute transport in unsaturated porous media is of interest in many engineering and environmental applications. The interplay between small-scale, local forces and the porous microstructure exerts a strong control on the transport of fluids and solutes at the larger, macroscopic scales. Heterogeneity in pore geometry is intrinsic to natural materials across a large range of scales. This multiscale nature, and the intricate links between two-phase flow and solute transport, remain far from well understood, by and large. Here, we use high-resolution direct simulation to quantify solute mixing and dispersion behavior within correlated porous media during drainage under an unfavorable viscosity ratio. Through analysis of flow and transport at multiple realizations, we find that increasing spatial correlations in pore sizes increase the size of the required Representative Elementary Volume (REV). We show that increasing the correlation length enhances solute dispersivity through its impact on the spatial distribution of low-velocity (diffusion-dominated) and high-velocity (advection-dominated) regions. Fluid saturation is shown to directly affect diffusive mass flux among high-and low-velocity zones. Another indirect effect of correlated heterogeneity on solute transport is through its control of the drainage patterns via repeated alteration in the connectivity of flowing pathways. Our findings improve quantitative understanding of solute mixing and dispersion under two-phase conditions, highly relevant to some of our most urgent environmental problems.

Utilizing atmospheric temperature observed from Mars Years 33 to 36 by the Imaging Ultraviolet Spectrograph (IUVS) onboard the Mars Atmosphere and Volatile Evolution (MAVEN) and Mars Climate Sounder (MCS) onboard Mars Reconnaissance Orbiter (MRO), we derive the diurnal and semidiurnal thermal tides from 30 to 160 km. Vertical phase velocities of the migrating tides indicate their upward propagation above 100 km during the dust season (solar longitude, Ls 240° to 300°). During the non-dust season (Ls 30° to 150°), the diurnal eastward wavenumber 2 (DE2) and wavenumber 3 (DE3) tides can propagate upward from the lower atmosphere to ~140 km. The seasonal variation of DE2 and DE3 amplitudes in the thermosphere corresponds well to their counterparts in the lower atmosphere, primarily controlled by their Hough (1,1) modes. The upward propagation of these tides could potentially impact the vertical coupling between the Martian lower and upper atmosphere.

Soil moisture is an important factor that affects terrestrial vegetation ecosystems and biological growth and development, and water deficit is one of the major environmental factors threatening vegetation restoration in the Loess Plateau. To determine the change in the soil water deficit characteristics from farmland to forestland on the Loess Plateau, in this study, we measured the soil water storage and deficit in abandoned grassland, shrubland, pioneer forestland and climax forestland along with vegetation succession. The results showed that the soil water content and the soil water storage with natural vegetation recovery from the abandoned grassland to shrubland and forestland showed a gradual declining trend, while on the contrary, the soil water deficit was increasing during succession, it was more severe in the deep soil than in the shallow soil layers, and the soil water deficit in July and September of the rainy season as well as that the vigorous growing period of plants was more serious than that in May and November, which are in the non-rainy season of the Chinese Loess Plateau. The vegetation types, soil texture and soil depth were the key factors affecting the soil water deficiency status in the process of vegetation succession. The results could have great potential in the sustainable development of forestry and provide a theoretical basis for effective water management and reasonable vegetation restoration in arid and semiarid loess regions.

Near-equatorial measurements of energetic electron fluxes, in combination with numerical simulation, are widely used for monitoring of the radiation belt dynamics. However, the long orbital periods of near-equatorial spacecraft constrain the cadence of observations to once per several hours or greater, i.e., much longer than the mesoscale injections and rapid local acceleration and losses of energetic electrons of interest. An alternative approach for radiation belt monitoring is to use measurements of low-altitude spacecraft, which cover, once per hour or faster, the latitudinal range of the entire radiation belt within a few minutes. Such an approach requires, however, a procedure for mapping the flux from low equatorial pitch angles (near the loss cone) as measured at low altitude, to high equatorial pitch angles (far from the loss cone), as necessitated by equatorial flux models. Here we do this using the high energy resolution ELFIN measurements of energetic electrons. Combining those with GPS measurements we develop a model for the electron anisotropy coefficient, n, that describes electron flux jtrap dependence on equatorial pitch-angle, αeq, jtrap ∼ sinnαeq. We then validate this model by comparing its equatorial predictions from ELFIN with in-situ near-equatorial measurements from Arase (ERG) in the outer radiation belt.

This study investigates the impact of weak sea surface temperature (SST) warm anomalies on trade cumulus cloudiness in an idealized and ensemble framework with large-eddy simulations. The control experiment uses a spatially uniform, time-invariant SST and mean large-scale conditions and atmospheric forcings derived from the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC). The perturbed experiment adds a Gaussian warm SST anomaly (SSTA) with a 12.5 km radius and 0.5 K magnitude. The ensemble-averaged differences between perturbation and control experiments show that cloud fraction is enhanced over the downwind half of the prescribed warm SSTA, with the enhancement peaking slightly above the environmental lifting condensation level (LCL) and then decaying with height. Furthermore, the low-level cloud response (<1 km) to the warm SSTA is stronger and occurs more systematically across different ensemble members. This near-LCL cloud response is driven by enhanced surface buoyancy flux and turbulence over the warm SSTA as opposed to SSTA-induced anomalous surface convergence and mesoscale upward motions. Process denial experiments indicate that the locally enhanced surface sensible and latent heat fluxes contribute almost equally to increase the near-LCL cloudiness, even though the locally enhanced surface sensible heat flux plays a dominant role in enhancing surface buoyancy flux. These results corroborate recent satellite composite results (Chen et al., 2023), suggesting that the observed increase of daily cloud fraction above warm SSTAs is due to more frequent turbulence-driven formation of shallow cumuli near the cloud base.

A document by Yasuo YABE. Click on the document to view its contents.

Relativistic electron precipitation (REP) refers to the release of high energy electrons initially trapped in the outer radiation belt that precipitate into the Earth’s upper atmosphere. REP plays an important role in the magnetosphere as it contributes to the fast depletion of radiation belt electron flux. This study presents a statistical analysis of the REP observations made by the Calorimetric Electron Telescope (CALET) experiment on board the International Space Station (2015- present). Specifically, a catalog based on count rates from the two top scintillators constituting the top charge detector, sensitive to electrons with energies $>$1.5 MeV and $>$3.4 MeV, respectively. Data from the CALET experiment reveals a previously unreported semi-annual variation in the occurrence of REP events. The REP periodicities are similar to those observed for trapped electrons in the outer belt, and correlates with the occurrence of solar wind high-speed streams and the solar cycle variations.

Breaking-wave induced bioluminescence is a critical component of the biogeochemical process in the ocean. Understanding bioluminescence is important for monitoring red tides caused by bioluminescent microorganisms. In this study, we present the first numerical effort to quantify bioluminescent light intensity based on high-fidelity direct numerical simulations of breaking waves and a quantitative bioluminescent model. The dynamics of breaking waves are extensively validated through comparison with existing studies. We find that the time-averaged and Lagrangian-averaged shear stress saturates as surface tension effects decrease and wave steepness increases. The spatial distribution of light intensity correlates with the wave crest overturning and air bubbles generated in plunging breakers. Furthermore, we observe that the maximum light intensity asymptotically approaches the emission of single cells, suggesting the potential for cost-effective prediction models in future studies.

Astronomical solutions form the backbone of accurate dating for geology and paleoclimate studies. Beyond ∼50 Ma, however, the chaos inherent in the solar system makes it impossible to calculate a single unique astronomical solution. Geological data have been used to constrain this chaos in order to arrive at a geologic time scale up to the end-Cretaceous. Here, we adopt and extend this approach into the latest Cretaceous, by re-analyzing the Zumaia and Sopelana composite proxy records from the Maastrichtian. We find that the filtered sum total light reflectance (L*) record is most compatible with the astronomical solution ZB20a. However, these results are sensitive to parameter choices in our algorithm, which we describe in detail. Nevertheless, we present evidence in favor of solution ZB20a for cyclostratigraphy during the latest Cretaceous. Periods with very long eccentricity nodes (VLNs) (low amplitude in the short eccentricity cycle) in the astronomical solutions that coincide with large amplitudes in the short eccentricity-related peaks in the filtered sum proxy record rule out alternatives.

In this study, we show that non-thermal collisions can play a significant role in shaping Europa's exospheric structure. Collisions between radiolytically produced O2 and the O produced via electron impact dissociation of O2 play a significant role in affecting the exospheric structure and escape rates. Specifically, O+O2 collisions lead to the production of a non-thermal O2 population, and increase the O2 escape while decreasing the O escape. These collisions are dependent on three specific physical parameters: (1) the density of O2 , (2) the electron impact dissociation rate of O2 , and (3) the O+O2 collision cross section. We demonstrate here that O+O2 collisions affect Europa's atmosphere even in the lowest limits considered. Thus, to more accurately determine the influence O+O2 collisions have on Europa's atmosphere in preparation for the forthcoming spacecraft missions, Europa Clipper and the JUpiter ICy moons Explorer (JUICE), these physical parameters need to be better constrained.