Surface Dynamics Research Articles

Integrating wide-swath altimetry data into Level-4 multi-mission maps

Abstract. Real-time observation of ocean surface topography is essential for various oceanographic applications. Historically, these observations have mainly relied on satellite nadir altimetry data, which were limited to observation scales greater than approximately 60 km. However, the recent launch of the wide-swath Surface Water Ocean Topography (SWOT) mission in December 2022 marks a significant advancement, enabling the two-dimensional global observation of finer-scale oceanic scales (∼ 15 km). While the direct analysis of the two-dimensional content of these swaths can provide valuable insights into ocean surface dynamics, integrating such data into mapping systems presents several challenges. This study focuses on integrating the SWOT mission into multi-mission mapping systems. Specifically, it examines the contribution of the SWOT mission to both the current nadir altimetry constellation (six/seven nadirs) and a reduced nadir altimetry constellation (three nadirs). Our study indicates that within the current nadir altimetry constellation, SWOT's impact is moderate, as existing nadir altimeters effectively constrain surface dynamics. However, in a hypothetical scenario where a reduced nadir altimetry constellation is envisioned to be operational by 2030, the significance of wide-swath data in mapping becomes more pronounced. Alternatively, we found that data-driven and dynamical mapping systems can significantly participate in refining the resolution of the multi-mission gridded products. Consequently, integrating high-resolution ocean surface topography observations with advanced mapping techniques can enhance the resolution of satellite-derived products, providing promising solutions for studying and monitoring sea-level variability at finer scales. However, to fully exploit SWOT's capabilities, future research will need to focus on innovations in data gridding and assimilation to extend mapping beyond geostrophically balanced flows.

Liquid flows induced in a rotating drum with different fill ratios

In the present study, we experimentally investigate the liquid flow induced in a rotating drum (cylindrical tank with a short aspect ratio) aligned horizontally, focusing on the variation in the time-averaged and fluctuating flow structures with different fill ratios. For each fill ratio, controlled by varying the water height, we measure the velocity fields at different cross-sectional planes with particle image velocimetry while varying the rotational speed of the drum. Compared to the condition of a fill ratio of 1.0, in which the liquid inside the drum rotates forming a large-scale (solid-body rotation) organized flow structure, a substantial asymmetric flow structure shows up in partially-filled conditions driven by the imbalance between (i) the momentum diffusion along the radial direction and the centrifugal acceleration, and (ii) the downward (gravitational) flux of the induced flow. In addition to the mean flow structure, we examine the fluctuating velocity fields together with the dynamics of the free surface, and we also briefly discuss the difference between the liquid flow and granular (particle) flow in a partially-filled drum. We think that the present results provide valuable insights on the partially-filled liquid drum toward various engineering applications.

Reservoir water level decline accelerates ground subsidence: InSAR monitoring and machine learning prediction of surface deformation in the Three Gorges Reservoir area

IntroductionSurface deformation in the Three Gorges Reservoir area poses significant threats to infrastructure and safety due to complex geological and hydrological factors. Despite existing studies, systematic exploration of long-term deformation characteristics and their driving mechanisms remains limited. This study combines SBAS-InSAR technology and machine learning to analyze and predict surface deformation in Fengjie County, Chongqing, China, between 2020 and 2022, focusing on riverside urban ground, riverside road slopes, and ancient landslides in the reservoir area.MethodsSBAS-InSAR technology was applied to 36 Sentinel-1A images to monitor surface deformation, complemented by hydrological and meteorological data. Machine learning models—Random Forest (RF), Extremely Randomized Trees (ERT), Gradient Boosting Decision Tree (GBDT), Support Vector Regression (SVR), and Long Short-Term Memory (LSTM)—were evaluated using six metrics, including RMSE, R2, and SMAPE, to assess their predictive performance across diverse geological settings.ResultsDeformation rates for riverside urban ground, road slopes, and ancient landslides were −3.48 ± 2.91 mm/yr, −5.19 ± 3.62 mm/yr, and −6.02 ± 4.55 mm/yr, respectively, with ancient landslides exhibiting the most pronounced deformation. A negative correlation was observed between reservoir water level decline and subsidence, highlighting the influence of seasonal hydrological adjustments. Urbanization and infrastructure development further exacerbated deformation processes. Among the models, LSTM demonstrated superior predictive accuracy but showed overestimation trends in ancient landslide areas.DiscussionReservoir water level adjustments emerged as a critical driver of subsidence, with rapid water level declines leading to increased pore pressure and soil compression. Seasonal effects were particularly evident, with higher subsidence rates during and after the rainy season. Human activities, including urbanization and road construction, significantly intensified deformation, disrupting natural geological conditions. Progressive slope failure linked to road expansion underscored the long-term impacts of engineering activities. For ancient landslides, accelerated deformation patterns were linked to prolonged drought and reservoir-induced hydrological changes. While LSTM models showed high accuracy, their limitations in complex geological settings highlight the need for hybrid approaches combining machine learning with physical models. Future research should emphasize developing integrated frameworks for long-term risk assessment and mitigation strategies in reservoir environments.ConclusionsThis study provides new insights into the complex surface dynamics in the Three Gorges Reservoir area, emphasizing the interplay of hydrological, geological, and anthropogenic factors. The findings highlight the need for adaptive management strategies and improved predictive models to mitigate subsidence risks.

Data-driven modeling for electro-active liquid crystal polymer networks

In this paper, we propose a data-driven nonlinear modeling approach to describe the dynamics of smart surfaces composed of electroactive liquid crystal networks (LCNs). LCNs are among the top candidates for materials to be employed in smart surfaces such as haptic displays. To realize such applications, the ability to predict an accurate LCN surface response as a function of the input signal is crucial. In this paper, we propose a data-driven modeling approach to identify the parameters of a dynamic model based on experimental data. The resulting model is used for feedforward control to compute the appropriate excitation parameters that ensure a certain desired surface deformation. This feedforward control approach is validated in a simulation study.

Single Particle Dynamics at the Free Surface of Imidazolium-Based Ionic Liquids.

In this work, we carry out a systematic computer simulation investigation of the single particle dynamics at the free surface of imidazolium-based room temperature ionic liquids by applying intrinsic surface analysis. Besides assessing the effect of the potential model and temperature, we focus in particular on the effect of changing the anion type, and, hence, their shape and size. Further, we also address the role of the length of the cation alkyl chains, known to protrude into the vapor phase, on the surface dynamics of the ions. We observe that the surface dynamics of ionic liquids, being dominated by strong electrostatic interactions, is about 2 orders of magnitude slower than that for common molecular liquids. Furthermore, the free energy driving force for exposing apolar chains to the vapor phase "pins" the cations at the surface layer for much longer than anions, allowing them to perform noticeable lateral diffusion at the liquid surface during their stay there. On the other hand, anions, accumulated in the second layer beneath the liquid surface, stay considerably longer here than in the surface layer. The ratio of the mean surface residence time of the cations and anions depends on the relative size of the two ions: larger size asymmetry typically corresponds to larger values of this ratio. We also find, in a clear contrast with the bulk liquid phase behavior, that anions typically diffuse faster at the liquid surface than cations. Finally, our results show that the surface dynamics of the ions is largely determined by the apolar layer of the cation alkyl chains at the liquid surface, as in the absence of such a layer, cations and anions are found to behave similarly with respect to their single particle dynamics.

Effects of Temperature Fluctuations on Surface Mobility of Atomic Steps and Oxidation Dynamics in High-Temperature Alloys.

In contrast to the traditional perspective that thermal fluctuations are insignificant in surface dynamics, here we report their influence on surface reaction dynamics. Using real-time low-energy electron microscopy imaging of NiAl(100) under both vacuum and O2 atmospheres, we demonstrate that transient temperature variations substantially alter the direction of atom diffusion between the surface and bulk, leading to markedly different oxidation outcomes. During heating, substantial outward diffusion of atoms from the bulk to the surface results in step growth. Conversely, cooling induces considerable inward diffusion of adatoms, producing a distinct oxide morphology. In both scenarios, initially formed oxide islands impede local atomic step mobility, thereby increasing step length due to mass transfer between the surface and bulk, with atomic steps acting as adatom sinks during heating and sources during cooling. Furthermore, we show that this pinning effect on atomic step mobility can be mitigated by applying persistent temperature fluctuations. Understanding these nuances is vital for accurately predicting and dynamically manipulating the performance of active materials in various chemical processes under transient thermal conditions.

Determining Dhap Pokhari lake surface dynamics for restoration strategies through geoelectrical mapping

ABSTRACT Lakes in the hilly regions of the Sikkim Himalayas in India are crucial for water supply and tourism. However, this area experiences frequent earthquakes and microtremors, increasing the risk of seismic hazards and contributing to a higher density of subsurface fractures and discontinuities. This has led to water seepage in lakes across Sikkim, turning some from perennial to seasonal. To investigate these issues, geoelectrical mapping techniques, specifically Vertical Electrical Sounding (VES) and profiling, were used to study Dhap Pokhari Lake in Sikkim’s Pakyong district. The findings revealed a subsurface fracture zone beginning at a depth of 20 m and extending down to 50 m. The VES data showed significant variations in sediment thickness and subsurface lithology between two measurement points only 10 m apart, with a noticeable ground settlement of about 2 m at one location. The profiling results indicated a major fracture and two minor ones, which are likely causing water seepage and ground saturation, particularly during rainy seasons, leading to compaction and ground settlement. This poses a risk to the structural stability of the surrounding areas, highlighting the need for effective lake restoration strategies. Geoelectrical mapping is a valuable tool for identifying such subsurface fractures and making evidence-based strategies to revive lakes in this seismically active region.

Characterizing Surface Deformation of the Earthquake-Induced Daguangbao Landslide by Combining Satellite- and Ground-Based InSAR.

The Daguangbao landslide (DGBL), triggered by the 2008 Wenchuan earthquake, is a rare instance of super-giant landslides globally. The post-earthquake evolution of the DGBL has garnered significant attention in recent years; however, its deformation patterns remain poorly characterized owing to the complex local topography. In this study, we present the first observations of the surface dynamics of DGBL by integrating satellite- and ground-based InSAR data complemented by kinematic interpretation using a LiDAR-derived Digital Surface Model (DSM). The results indicate that the maximum line-of-sight (LOS) displacement velocity obtained from satellite InSAR is approximately 80.9 mm/year between 1 January 2021, and 30 December 2023, with downslope displacement velocities ranging from -60.5 mm/year to 69.5 mm/year. Ground-based SAR (GB-SAR) enhances satellite observations by detecting localized apparent deformation at the rear edge of the landslide, with LOS displacement velocities reaching up to 1.5 mm/h. Our analysis suggests that steep and rugged terrain, combined with fragile and densely jointed lithology, are the primary factors contributing to the ongoing deformation of the landslide. The findings of this study demonstrate the effectiveness of combining satellite- and ground-based InSAR systems, highlighting their complementary role in interpreting complex landslide deformations.

Characterizing ground ice content and origin to better understand the seasonal surface dynamics of the Gruben rock glacier and the adjacent Gruben debris-covered glacier (southern Swiss Alps)

Abstract. Over the recent years, there have been focused international efforts to coordinate the development and compilation of rock glacier inventories. Nevertheless, in some contexts, identifying and characterizing rock glaciers can be challenging as complex conditions and interactions, such as glacier–rock-glacier interactions, can yield landforms or landform assemblages that are beyond a straightforward interpretation and classification through ordinary visual means alone. To gain a better understanding of the spatial and temporal complexity of the ongoing processes where glacier–permafrost interactions have occurred, the characterization of the subsurface of the Gruben rock glacier and its adjacent complex contact zone with the then more extended Little Ice Age Gruben glacier is quantitatively assessed using a petrophysical joint inversion (PJI) scheme, based on electrical resistivity (ERT) and refraction seismic (RST) data. Surface dynamics are assessed using both in situ and close-range remote sensing techniques to monitor daily and seasonal displacements and to monitor landform-wide surface changes at high spatial resolution, respectively. Both the geophysical and geodetic surveys allowed two zones to be identified: the rock glacier zone and the complex contact zone where both permafrost and embedded surface ice are present. In the complex contact zone extremely high ice contents (estimated up to 85 %) were found. Widespread supersaturated permafrost conditions were found in the rock glacier zone. Surface displacement rates in this zone are typical of permafrost creep behaviour, with a gradual acceleration in late spring and a gradual deceleration in winter. Moreover, the coherent nature of the rock glacier zone surface deformation contrasts with the back-creeping and slightly chaotic surface deformation of the complex contact zone. Favouring a multi-method approach allowed a detailed representation of the spatial distribution of ground ice content and origin, which enabled us to discriminate glacial from periglacial processes as their spatio-temporal patterns of surface change and geophysical signatures are (mostly) different.

Atmospheric and Surface Dynamics During Winter Warm Spells in the Southern Great Plains: Insights From the 2021 Case Study

AbstractTwo 2021 winter warm spell events experienced near record extreme surface temperatures, anomalies exceeding C, during the winter season in 2021 across the Southern Great Plains (SGP). Extreme heat during the winter season results in similar detrimental socioeconomic impacts compared to their counterpart summer heat wave events. Winter warm spell events across the SGP have been historically increasing over the last several decades, and as such, it is crucial to investigate the drivers of these extreme events. In this study, we use ERA‐5 reanalysis data to investigate the atmospheric and surface characteristics associated with these two extreme events (i.e., (a) 29 November–17 December 2021 and (b) 22 December–31 December 2021). A prolonged period of positive geopotential height anomalies amplified subsidence in combination with increased incoming solar radiation and surface heat fluxes aiding extreme surface temperatures during the first winter warm spell event. However, a more prominent atmospheric blocking high (i.e., Alaskan Ridge) initiated and intensified the extreme heat during the second winter warm spell. Increased incoming solar radiation and positive sensible heat flux due to a dry surface fostered extreme heat during the second winter warm spell event. Warm air advection throughout both winter warm spell events supported the extreme surface temperatures. Discovering potential crucial drivers to winter warm spells identifies the sources of predictability to improve prediction of these extreme heat events.

Nature of the carrier dynamics and contrast formation on the photoactive material surfaces: Insight from ultrafast imaging to DFT calculations.

Precise material design and surface engineering play a crucial role in enhancing the performance of optoelectronic devices. These efforts are undertaken to particularly control the optoelectronic properties and regulate charge carrier dynamics at the surface and interface. In this study, we used ultrafast scanning electron microscopy (USEM), which is a powerful and highly sensitive surface tool that provides unique information about the photoactive charge dynamics of material surfaces selectively and spontaneously in real time and space in high spatial and temporal resolution. Here, time-resolved images of CdTe (110), CdSe (100), GaAs (110), and other semiconductors revealed that the presence of oxide layers on the surface of materials leads to an increase in the work function (WF) and trap state densities upon optical excitation, leading to the formation of dark image contrast in USEM experiments. These findings were further supported by abinitio calculations, which confirmed the reliability of the observed changes in the excited surface WFs. Besides enhancing our understanding of surface charge dynamics, it also offers valuable insights into manipulating these properties. This study paves the way for precise control and the potential to design highly efficient light-harvesting devices.

Microdroplet Resuspension Off Surfaces.

Understanding the resuspension of droplets from surfaces into air is important for elucidating a range of processes such as disease transmission of airborne pathogens and determining environmental contamination and the effectiveness of cleaning procedures. The resuspension condition is defined as the escape velocity of a droplet from a surface. This study investigated the dynamics of microliter-sized droplet resuspension off surfaces utilizing a novel free-fall device. We studied surfaces with three different wettabilities, three droplet volumes, and substrate velocities ranging from 0 to 3.5 m/s for deionized water and viscous droplets representing a prototype saliva substitute. Experimental results provide quantitative results for the increased propensity for drop resuspension for more hydrophobic surfaces, larger droplet volume, and higher velocity. By using high-speed imaging, we segment the resuspension process into four stages: initial equilibrium, deformation, elongation, and breakage. Experimental results are generalized as a machine-learning-derived decision surface, which predicts resuspension by defining a 2D decision boundary in our 3D parameter space. We present a simple physical model, corroborated by computational fluid dynamics simulations, for the dynamics of resuspension that explains the process and is in good agreement with the experiments.

Schmidt-hammer exposure-age dating of talus slopes in upper Jostedalen, southern Norway: Interpreting the age and development of diachronous surfaces

Schmidt-hammer exposure-age dating (SHD) was used to evaluate the surface age, dynamics and evolution of eight talus (scree) slopes located between ~520 and ~1010 m a.s.l. in the upper Jostedalen area of southern Norway. Statistically significant differences in mean R-values were found between talus slopes but there was no consistent difference in R-values between three mid- to lower-slope positions, two operators, or first and second impacts from the same boulders. A new regional age-calibration equation yielded SHD ages ranging from 8425 ± 700 years to 2620 ± 740 years. SHD ages from talus slopes and other landforms with diachronous surfaces (such as alluvial fans, snow-avalanche fans, pronival ramparts and rock glaciers) represent the average exposure age of the surface boulders and provide insights into landform evolution. Here, our SHD ages are interpreted in terms of Early Holocene paraglacial rock-slope instability, Mid-Holocene permafrost degradation, low but possibly variable rates of rockfall activity in the Late-Holocene, and spatial variations affected by local site differences. Survival of rock particles with relatively old exposure ages towards the distal margins of the talus slopes is attributed to their slow development with low levels of modern activity. SHD ages from diachronous surfaces may considerably underestimate landform age (defined as the onset of landform formation). Greater application can be anticipated, however, in the inference of landform dynamics from the R-value distributions of diachronous surfaces and in the use of SHD age as an indicator of the extent of modern activity.

Assessment of reactive surface and kinetic parameters of basaltic rocks during CO2 storage

Carbon capture and storage (CCS) is a novel technology that aims to reduce the presence of carbon dioxide from the atmosphere. This technology involves capturing CO2 from industrial sources or directly from the air, treating, transporting, and storing it in long-term safe rock formations. Basaltic rock comprises reactive minerals and glassy phases, which trap CO2 permanently through the mineralization mechanism. However, this method is complex mainly due to the rapid interaction between solid and liquid phases. The mineralization occurs at the interface between the reactive fluid and the basaltic rock surface, converting the dissolved CO2 into solid carbonate mineral that precipitates in the pores and fractures of the rock matrix. The reaction rate of a basaltic rock depends significantly on the CO2 wettability and rock-fluid interfacial interactions. However, there is limited information about the influence of the reactive surface on the reaction rate of minerals present in basalt formations. This work investigates the influence of kinetics parameters such as pH, temperature, and reactive surface area in the reaction rate of basaltic rocks. Basaltic rock dissolution and precipitation is assessed using the geochemical software PHREEQC. The proposed numerical model solves the reactive transport problem and provides feedback on the influence of the kinetics reaction parameters. The dynamics of the reactive surface during the reaction of basalt rocks is evaluated. The numerical results show the potential of basaltic rock for CO2 mineral storage as solid carbonates and identify the main factors that limit the mineralization process. Finally, this work provides a deeper understanding of CO2 mineralization that can provide valuable findings to guide Brazilian CCS projects.

2D/3D heterojunction carrier dynamics and interface evolution for efficient inverted perovskite solar cells

The 2D/3D heterojunction perovskites have garnered increasing attention due to their exceptional moisture and thermal stability. However, few works have paid attention to the influence of the subsequent change process of 2D/3D heterojunction PSC on the stability of PSCs. Moreover, the evolution of the interface and carrier dynamic behavior of the 2D/3D perovskite films with long-term operation has not been systematically developed before. In this work, the effects of 2D/3D heterojunction evolution on the interface of perovskite films and different carrier dynamics during 2D/3D evolution are systematically analyzed for the first time. The decomposition of 2D/3D heterojunction in the perovskite film will have a certain impact on the surface and carrier dynamics behavior of perovskite. During the evolution of 2D/3D heterojunction, PbI2 crystals will appear, which will improve the interfacial energy level matching between the electron transport layer and perovskite film. With a long evolution time, some holes will appear on the surface of perovskite film. The open circuit voltage (VOC) of PSCs increased from 1.14 to 1.18 V and the PCE increased to 23.21% after 300 h storage in the nitrogen atmosphere, and maintained 89% initial performance for with 3000 h stability test in N2 box. This discovery has a significant role in promoting the development of inverted heterojunction PSCs and constructing the revolution mechanism of charge carrier dynamic.

Insights of Dynamic Forcing Effects of MJO on ENSO from a Shallow Water Model

Abstract The Madden–Julian oscillation (MJO) is believed to play a significant role in triggering El Niño–Southern Oscillation (ENSO) events and affect the dynamics of ENSO. In this study, the dynamic forcing effects of MJO on the equatorial oceanic dynamic fields and the onsets of different types of ENSO events are investigated through sensitive experiments using spatiotemporally filtered forcing based on an anomalous shallow water model. The comparisons between observations and model responses provide meaningful insights into the extent of MJO’s impacts on sea surface dynamics relative to other atmospheric variabilities. The following conclusions are made. First, the MJO-forced perturbations on zonal currents are stronger and more significant than those on sea surface heights. Second, MJO is essential for improving zonal current simulation in the western-central Pacific and generating activity centers of zonal currents in the eastern Pacific in the model. Third, MJO tends to contribute to the onset of El Niño events rather than La Niña events. Strong intraseasonal oceanic Kelvin waves forced by MJO are confirmed in simulations during the onset stages of the 1997/98 and 2004/05 events. The 120-day running standard deviations of zonal current and sea surface height anomaly series forced by MJO exhibit positive skewness similar to those of the 20–100-day band-passed observational series. Yet, not all the onsets of historical ENSO events are in company with strong MJO-related perturbations. Additionally, the wind stress formula can amplify the responses of zonal current and sea surface height anomalies to synoptic forcings with periods shorter than 20 days through entraining lower-frequency variabilities. Significance Statement The Madden–Julian oscillation (MJO) is believed to be able to trigger El Niño–Southern Oscillation (ENSO) events and influence our understanding of the fundamental nature of ENSO. In this study, spatiotemporally filtered forcing experiments are implemented on an anomalous shallow water model. The results show that MJO is more important for improving the simulation of surface zonal currents rather than the sea surface heights and tends to contribute to the onset of El Niño events rather than La Niña events through triggering strong intraseasonal oceanic Kelvin waves.

Surface dynamics of small fast-rotating asteroids: Analysis of possible regolith on asteroid 2016 HO3

The Chinese Tianwen-2 mission is planned to explore and sample the near-Earth asteroid 2016 HO3, also named 469219 Kamo’oalewa. This paper intends to answer the question of whether 2016 HO3 has any regolith. A 3D model of an irregular shape was reconstructed from light curve data of 2016 HO3, with simulated impact craters embedded on its surface. We used numerical simulations to calculate the acceleration from gravity, fast rotation, and the van der Waals cohesive force. We found that the poles have a higher chance of hosting regolith, and the regolith may also rest on the walls of craters that face toward the rotation axis, making them potential sample collection sites. On the surface of 2016 HO3, the van der Waals force is strong enough to hold particles smaller than several centimeters against centrifugal force. Furthermore, we compare a pair of transient processes: thermal fatigue, which generates small particles, and micro-impacts, which remove the surface mass. Thermal fatigue is at least comparable to, and perhaps more efficient than, micro-impacts for 2016 HO3. Therefore, it is highly possible that regolith exists on the surface of 2016 HO3.

Theory of spin center sensing of diffusion and other surface electric dynamics

Surface electric dynamics influences the quantum coherence of near-surface spin centers (i.e., T1 and T2 times) through spatial and temporal fluctuations of the surface charge density and the electrostatic potential at the crystal surface that are described by the spectral noise density S(ω). We find that the electric noise's S(ω) dependence on the depth d of a spin center below the surface follows a power law d−γ not solely determined by whether the surface charges move as localized pointlike charges (monopoles) or dipoles. The exponent γ instead reveals the structure of the surface charge and surface potential correlation functions. For surface dynamics originating from diffusion, the spin center's relaxation and decoherence times exhibit a temporal crossover near the correlation time of the fluctuators and thus provide a quantitative fingerprint of the diffusive behavior of charged particles at surfaces. Published by the American Physical Society 2024

Kr Adsorption in Porous Carbons: Temperature-Dependent Experimental and Computational Studies†.

The temperature dependence of the adsorption energy of krypton adsorption on activated carbon materials was studied by experiment and simulation. Adsorption isotherms were measured at temperatures from 250 to 330 K and analyzed with Henry's law. The adsorption energy determined from these measurements was found to weaken by more than 10% in this range. Slit pore widths for simulations in this work were modeled by the removal of integral numbers of planes in graphite. Vibrational dynamics of the krypton adsorbate and the carbon atom adsorbent were calculated with the stochastic temperature-dependent effective potential (sTDEP) method, using energetics from density functional theory (DFT) with the many-body dispersion energy method (MBD). Thermal displacements of carbon atoms had a negligible effect on the adsorption energy. The width of the slit pore had the greatest effect on the surface dynamics and the energies of the adsorbate atoms at different temperatures. Assuming a distribution of pore widths, the Boltzmann distribution of site occupancies causes a large weakening of the thermally averaged adsorption energy at higher temperatures.

A temporally insensitive spatio-temporal fusion method for remote sensing imagery via semantic prior regularization

Spatio-temporal fusion has become a popular technology for generating remote sensing images with high spatial and high temporal resolutions, thus providing valuable data support for remote sensing monitoring applications, such as environmental monitoring and city planning. Currently, deep learning-based methods have garnered a significant amount of attention, and they mostly employ the fine image at the neighboring date as an auxiliary image. However, capturing usable neighboring fine images may be challenging due to the adverse effects of weather conditions on optical images. Moreover, the fusion performance drops sharply when the temporal interval is long (i.e., there are significant differences in images). In this paper, we proposed a bidirectional pyramid fusion network with semantic prior regularization (BPFN-SPR), which exhibits remarkable flexibility and robustness to temporal intervals.Specifically, the proposed BPFN-SPR contains dual-path operations (i.e., Semantic Extraction path and Image Reconstruction path). The semantic extraction path has two modes: parameter learning mode and parameter freezing mode. The parameter learning mode aims to learn the information representation of the auxiliary fine image, while the parameter freezing mode aims to perceive the accurate semantic information of the target fine image. The image reconstruction path progressively reconstructs spatial details of fine images from coarse images, which jointly optimizes the target fine image and the auxiliary fine image, reducing the temporal sensitivity of the reconstruction branch, and thereby improving its generalization ability. Experimental results show that the proposed method has competitive performance, especially for areas with land cover changes. In addition, extensive experiments using images at multi-temporal intervals as auxiliary images have also demonstrated the significant advantages of the proposed method. The mean PSNR value attains 31.0713, while the average spectral index SAM measures 0.1640 on the LGC test set. Meanwhile, for the CIA test set, the average PSNR is recorded at 29.5332, accompanied by an average spectral index SAM of 0.1865. Therefore, the proposed BPFN-SPR has considerable potential in monitoring Earth's surface dynamics.