Search Results (196)

Total Electron Content (TEC) is a fundamental parameter characterizing the electron density distribution in the ionosphere. Traditional global TEC modeling approaches predominantly rely on mathematical methods (such as spherical harmonic function fitting), often resulting in models suffering from excessive smoothing and low accuracy. While the 1° high-resolution global TEC model released by MIT offers improved temporal-spatial resolution, it exhibits regions of data gaps. Existing ionospheric image completion methods frequently employ Generative Adversarial Networks (GANs), which suffer from drawbacks such as complex model structures and lengthy training times. We propose a novel high-resolution global ionospheric TEC modeling method based on a Dual-Branch Convolutional Neural Network (DB-CNN) designed for the completion and restoration of incomplete 1°-resolution ionospheric TEC images. The novel model utilizes a dual-branch input structure: the background field, generated using the International Reference Ionosphere (IRI) model TEC maps, and the observation field, consisting of global incomplete TEC maps coupled with their corresponding mask maps. An asymmetric dual-branch parallel encoder, feature fusion, and residual decoder framework enables precise reconstruction of missing regions, ultimately generating a complete global ionospheric TEC map. Experimental results demonstrate that the model achieves Root Mean Square Errors (RMSE) of 0.30 TECU and 1.65 TECU in the observed and unobserved regions, respectively, in simulated data experiments. For measured experiments, the RMSE values are 1.39 TECU and 1.93 TECU in the observed and unobserved regions. Validation results utilizing Jason-3 altimeter-measured VTEC demonstrate that the model achieves stable reconstruction performance across all four seasons and various time periods. In key-day comparisons, its STD and RMSE consistently outperform those of the CODE global ionospheric model (GIM). Furthermore, a long-term evaluation from 2021 to 2024 reveals that, compared to the CODE model, the DB-CNN achieves average reductions of 38.2% in STD and 23.5% in RMSE. This study provides a novel dual-branch input convolutional neural network-based method for constructing 1°-resolution global ionospheric products, offering significant application value for enhancing GNSS positioning accuracy and space weather monitoring capabilities. Full article

We present the validation of the latest version F Geophysical Data Records (GDR-F) for the TOPEX/POSEIDON (T/P) altimetry satellite mission. The GDR-F products represent a major evolution with respect to the preceding version B Merged Geophysical Data Records (MGDR-B) that were released more than two decades ago. Specifically, the numerical retracking of the altimeter waveforms significantly mitigates long-standing issues in the TOPEX altimeter measurements, such as drifts and hemispherical biases in the altimeter range and significant wave height. Additionally, GDR-F incorporates updated geophysical model standards consistent with current altimeter missions, improved sea state bias corrections, end-of-mission calibration for the microwave radiometer, and refined orbit ephemeris solutions. These enhancements notably decrease the variance of the Sea Surface Height Anomaly (SSHA) measurements, with along-track SSHA variance reduced by 26 cm² compared to MGDR-B and crossover SSHA variance lowered by 1 cm². GDR-F products also demonstrate improved consistency with Jason-1 measurements during their tandem mission phase, reducing the standard deviation of differences from 6 cm to 4 cm when compared to Jason-1 GDR-E data. These results confirm that GDR-F products offer a more accurate and consistent T/P data record, enhancing the quality of long-term sea level studies and supporting inter-mission altimetry continuity. Full article

This study investigates the combined effects of mesoscale eddies and rough sea surfaces on acoustic propagation in the eastern Arabian Sea and Gulf of Aden during summer monsoon conditions. Utilizing three-dimensional sound speed fields derived from CMEMS data, sea surface spectra from the SWAN wave model validated by Jason-3 altimetry, and the BELLHOP ray-tracing model, we quantify their synergistic impacts on underwater sound. A Monte Carlo-based dynamic sea surface roughness model is integrated with BELLHOP to analyze multiphysics interactions. The results reveal that sea surface roughness significantly influences surface duct propagation, increasing transmission loss by approximately 20 dB compared to a smooth sea surface, while mesoscale eddies deepen the surface duct and widen convergence zones by up to 5 km. In deeper waters, eddies shift convergence zones and reduce peak sound intensity in the deep sound channel. These findings enhance sonar performance and underwater communication in dynamic, monsoon-influenced marine environments. Full article

Sea surface height (SSH) serves as a fundamental geophysical parameter in oceanographic research. In 2023, China successfully launched the world’s first spaceborne interferometric GNSS-R (iGNSS-R) altimeter, which features dual-frequency multi-beam scanning, interferometric processing, and compatibility with three major satellite navigation systems: the BeiDou Navigation Satellite System (BDS), the Global Positioning System (GPS), and the Galileo Satellite Navigation System (GAL). This launch marked the first in-orbit validation of the iGNSS-R altimetry technology. This study provides a detailed overview of the iGNSS-R payload design and analyzes its dual-frequency delay mapping (DM) measurements. We developed a refined DM waveform-matching algorithm that precisely extracts the propagation delays between reflected and direct GNSS signals, enabling the retrieval of global sea surface height (SSH) through the interferometric altimetry model. For validation, we employed an inter-satellite crossover approach using Jason-3 and Sentinel-6 radar altimetry as references, achieving an unprecedented SSH accuracy of 17.2 cm at a 40 km resolution. This represents a breakthrough improvement over previous GNSS-R altimetry efforts. The successful demonstration of iGNSS-R technology opens up new possibilities for cost-effective, wide-swath sea level monitoring. It showcases the potential of GNSS-R technology to complement existing ocean observation systems and enhance our understanding of global sea surface dynamics. Full article

Existing low-light image enhancement methods often struggle to effectively enhance space targets in deep-space contexts due to the effects of extremely low illumination, stellar stray light, and Earth halos. This work proposes a low-light image enhancement method based on multi-image fusion, which integrates features of space targets with the Retinex theory. The method dynamically adjusts contrast by detecting luminance distribution and incorporates an adaptive noise removal mechanism for enhanced image quality. This method effectively balances detail enhancement with noise suppression. This work presents experiments on deep-space background images featuring 10 types of artificial satellites, including AcrimSat, Calipso, Jason, and others. Experimental results demonstrate that the proposed method outperforms traditional methods and mainstream deep learning models in qualitative and quantitative evaluations, particularly in suppressing Earth halo interference. This study establishes an effective framework for improving the visual quality of spacecraft images and provides important technical support for applications such as spacecraft identification, space target detection, and autonomous spacecraft navigation. Full article

After the publication of the paper, Endre Takacs from Clemson University contacted the corresponding author Alaa Saadah to ask for multiple individuals (Laszlo Fadgyas, Jason Henderson, Tibor Koroknai, Máté Koroknai, David Takacs, Peter Panko, and Endre Takacs) to be added as additional co-authors of the original publication [...] Full article

This paper describes and implements a time-spatial correction of the regional prediction wave system, compared with altimeter data, by using an ensemble Kalman filter. The technique is successful in areas with substantial wave height around the Azores islands. Using winds from ERA5 and wave spectral boundary conditions from a prior study, the SWAN wave model generates wave conditions in the Azores area for 6 years. The time-spatial correction model is determined by comparing the hindcast data with the data from seven altimetry satellites: ERS-1, ERS-2, ENVISAT, TOPEX/POSEIDON, Jason-1, Jason 2, and GEOSAT Follow ON. The hindcast results are then corrected with the correction model. Furthermore, in situ buoy measurements are then employed to validate the corrected hindcast data. The outcomes demonstrate a significant improvement in the wave predictions. Full article

Jason Allen-Paisant in Self-Portrait as Othello moves unflinchingly through complex histories and genealogies that widen to include Jamaica, Venice, Italy, France, and elsewhere and to locate the duppy manifestations of an unburied past in the pervasive precariousness of Black life. Across his poems, he tracks the chaotic reverberations of intergenerational traumas that persist across time, space and collective memory. This paper contends that the poet, through his use of allusion evident in his grafting and borrowings of other stories, literary syncretism, the symbolism of foreignness and its mysterious power, back and forth journeys through Europe and into homelands (Jamaica), procures an integrated circuit of Black meaning and kindred relations. This interconnectedness lays bare the sociohistorical conditions that have and continue to circumscribe and assault Black lives and deconstructs the perpetuity of anti-Black systems in the modern Western world. For all his worldly travels, the poet-narrator situates himself in an interstitial zone where each crossroad leads to new possibilities and affirmative energy. Allen-Paisant thus offers a way to reconcile a vicious history of Black xenophobia while procuring moments and processes to make peace with rupturous spaces, which necessitates a return to his homeland. However, homecoming complicates the search for self and the idea of return draws him into a dialogue with the fragmented inheritances of his past. He ultimately achieves coherence and fresh understandings through images of sterility and barrenness which he re-purposes as a foundation to make bold leaps of faith across uncertain chasms. This paper thus argues that for the poet of the African diaspora, who aspires to recover a long and complex spiritual history, the interface between domestic and international dramas highlights the luminous transcendence embodied in the journey along complicated routes and the steadfast pursuit of ideas that illuminate the deepest insights about identity, culture and the Black experience. Full article

Satellite altimetry observations are checked against in situ measurements to assess the capability of this remote sensing technique to describe the surface circulation in the Ligurian Sea. CTD profiles were collected during five oceanographic campaigns from 2017 and 2024 along the satellite track Jason 044, crossing the Ligurian Sea from the Corsica Channel to the coast close to Genoa. Eight months of ADCP surface currents from a fixed mooring were also used for the comparison with altimetric-derived geostrophic currents. Moreover, the possible contribution of ICESat-2 to oceanographic studies in the area is investigated. Altimetric measurements successfully reproduce the basic circulation features of the region and their seasonal variation and, despite the different nature of the used systems, can be well integrated with in situ observations. The results from the direct comparison with daily mean values of ADCP surface currents reported an RMSD of the same order as the standard deviation, which is consistent with similar investigations in other areas but evidences the need to define more appropriate metrics and methods. Full article

In 2024, Eilish Quin published the novel Medea, which is a feminist approach to the Medea myth from Greek mythology. Medea’s myth is heavily influenced by Euripides’ play Medea, a play in which she kills her children to enact revenge on her cheating husband Jason. Quin’s novel is a reimagining of the myth, which explores Medea’s monstrosity and attempts to make her more sympathetic and less monstrous than the source text. I argue that Quin’s novel pulls from established characteristics of Medea that depict her as a monster and attempts to shift the narrative perspective. Using monster theory, I examine Medea’s monstrosity by looking at Euripides’ play and Quin’s novel. Quin attempts to recast Medea as a sympathetic woman instead of a monster through Medea’s anti-woman sentiments and monstrous power, along with her status as an outsider; moreover, Medea’s villainous nature is removed by changing the story surrounding the murder of her brother and children while stressing Jason’s excessively violent nature. Quin’s novel reflects a contemporary concern with female autonomy and victimization, but the novel’s approach highlights the issues with trying to remove Medea’s monstrosity. Full article

The Surface Water and Ocean Topography (SWOT) mission was launched on 16 December 2022 to measure water levels over both open ocean and inland waters. To achieve these objectives, the SWOT Payload contains an innovative Ka-band radar interferometer, called KaRIn, completed with a nadir altimeter called POSEIDON-3C that was switched on a month after launch and a few days before KaRIn. POSEIDON-3C measurements provide a link between large-scale phenomena and high resolution. The POSEIDON-3C design is based on POSEIDON-3B, its predecessor on board JASON-3. It is also a dual-frequency radar altimeter operating in C- and Ku-bands, but with some improvements to enhance its performance. Even though it is a Low Resolution Mode altimeter, its performance over open ocean, inland waters and coastal zones are indeed excellent. This paper first describes the POSEIDON-3C design and its modes with a focus on its new features and the Digital Elevation Model that drives its open-loop tracking mode. Then, we assess the in-flight performances of the altimeter from an instrumental point of view. For that purpose, special and routine calibrations have been realized. They show the good performance and stability of the radar. In-flight assessments thus provide confidence when it comes to ensuring excellent altimeter measurement stability throughout the mission duration. Full article

Collagen-based membrane is the most commonly used biomaterial for guided bone and tissue regeneration; however, its barrier function can be threatened by its rapid degradation pattern, affecting the success of the regeneration process. Differences in the origin and functionalization of the membrane to obtain better properties can alter the degradation rate. The objective of this study was to examine the biodegradation pattern of two commercially available collagen membranes (Jason^® and Collprotect^®) manufactured using porcine pericardium or dermis, doped or not with zinc-ions or doxycycline, in a period up to 21 days. The membrane specimens were subjected to hydrolytic and bacterial degradation tests. The different immersion times were carried out from 12 h up to 21 days. At each time point, quantitative measurements of thickness and weight were made using a digital caliper and an analytic microbalance, respectively. ANOVA and Student–Newman–Keuls tests were carried out for comparison purposes (p < 0.05). The differences between time-points within the same membranes and solutions were assessed by pairwise comparisons (p < 0.001). Unfunctionalized Jason membrane made of porcine pericardium attained the highest resistance to both degradation tests. The functionalization of the membranes did not alter the biodegradation patterns. All the membranes completely degraded before 48 h in the bacterial collagenase solution, which was the most aggressive test. Full article

This study analyzes sea level changes (SLCs) in China seas and their adjacent ocean (CSO) using data from the TOPEX/Poseidon and Jason-1/2/3 satellite altimetry missions from 1993 to 2022. A 30-year time series of sea level anomalies (SLAs) is established, with trends, spatial distribution, and periodicities analyzed through least squares linear fitting, Kriging interpolation, and wavelet analysis. The average yearly sea level rise in the CSO is 3.87 mm, with specific rates of 4.15 mm/yr in the Bohai Sea, 3.96 mm/yr in the Yellow Sea, 3.54 mm/yr in the East China Sea, and 4.09 mm/yr in the South China Sea. This study examines the spatiotemporal variations in SLAs and identifies an annual primary cycle, along with a new periodicity of 11 years. Utilizing 30 years of satellite observation data, particularly the newer Jason-3 satellite data, this reanalysis reveals new findings related to cycles. Overall, the research updates previous studies and provides valuable insights for further investigations into China’s marine environment. Full article

The study of upper ocean mixing processes, including their dynamics and thermodynamics, has been a primary focus for oceanographers and meteorologists. Wave breaking in deep water is believed to play a significant role in these processes, affecting air–sea interactions and contributing to the energy dissipation of surface waves. This, in turn, enhances the transfer of gas, heat, and mass at the ocean surface. In this paper, we use the FVCOM-SWAVE coupled wave and current model, which is based on the MY-2.5 turbulent closure model, to examine the response of upper ocean turbulent kinetic energy (TKE) and temperature to various wave breaking parametric schemes. We propose a new parametric scheme for wave breaking energy at the sea surface, which is based on the correlation between breaking wave parameter $R_B$ and whitecap coverage. The impact of this new wave breaking parametric scheme on the upper ocean under typhoon conditions is analyzed by comparing it with the original parametric scheme that is primarily influenced by wave age. The wave field simulated by SWAVE was verified using Jason-3 satellite altimeter data, confirming the effectiveness of the simulation. The simulation results for upper ocean temperature were also validated using OISST data and Argo float observational data. Our findings indicate that, under the influence of Typhoon Nanmadol, both parametric schemes can transfer the energy of sea surface wave breaking into the seawater. The new wave breaking parameter $R_B$ scheme effectively enhances turbulent mixing at the ocean surface, leading to a decrease in sea surface temperature (SST) and an increase in mixed layer depth (MLD). This further improves upon the issue of uneven mixing of seawater at the air–sea interface in the MY-2.5 turbulent closure model. However, it is important to note that wave breaking under typhoon conditions is only one aspect of wave impact on ocean disturbances. Therefore, further research is needed to fully understand the impact of waves on upper ocean mixing, including the consideration of other wave mechanisms. Full article

This study employs the two-dimensional Legendre polynomial fitting (2-D LPF) method to fit M2 tidal harmonic constants from satellite altimetry data within the region of 53°E–131°E, 34°S–6°N, extracting internal tide signals acting on the sea surface. The M2 tidal harmonic constants are derived from the sea surface height (SSH) data of the TOPEX/Poseidon (T/P), Jason-1, Jason-2, and Jason-3 satellites via t-tide analysis. We validate the 2-D LPF method against the 300 km moving average (300 km smooth) method and the one-dimensional Legendre polynomial fitting (1-D LPF) method. Through cross-validation across 42 orbits, the optimal polynomial orders are determined to be seven for 1-D LPF, and eight and seven for the longitudinal and latitudinal directions in 2-D LPF, respectively. The 2-D LPF method demonstrated superior spatial continuity and smoothness of internal tide signals. Further single-orbit correlation analysis confirmed generally higher correlation with topographic and density perturbations (correlation coefficients: 0.502, 0.620, 0.245; 0.420, 0.273, −0.101), underscoring its accuracy. Overall, the 2-D LPF method can use all regional data points, overcoming the limitations of single-orbit approaches and proving its effectiveness in extracting internal tide signals acting on the sea surface. Full article