Search Results (270)

Regional sea-level trends derived from satellite altimetry deviate substantially from the global mean, but the relative roles of externally forced change and internally generated climate variability remain difficult to separate from the short satellite record. Here, we examine the 32-year Data Unification and Altimeter Combination System (DUACS) gridded multi-mission satellite altimetry product (January 1993–December 2024) together with 100 100-year samples from an unforced Community Earth System Model (CESM) pre-industrial control simulation. Empirical orthogonal function (EOF) analysis of satellite sea-level anomalies reveals a leading mode explaining 10.9% of total variance, with an Interdecadal Pacific Oscillation (IPO)-like dipolar pattern and high correlation with the IPO index (r = 0.92). A similar IPO-like mode appears consistently in the unforced CESM samples. Because previous large-ensemble studies indicate that the externally forced sea-level response is generally broader and structurally distinct from this dipolar internal mode, this agreement supports the interpretation that the satellite-observed leading pattern is strongly consistent with internally generated variability, although a partial forced contribution, particularly in the tropical Pacific, cannot be excluded. Based on CESM simulations, the empirical contribution of internal variability to regional trend uncertainty decreases approximately inversely with record length. The resulting location-specific estimate can be scaled by the local EOF amplitude and is largest in regions where the dominant internal-variability mode has large amplitudes, including the western tropical Pacific and Indian Ocean. However, this estimate represents only the internally generated component inferred from a single unforced CESM simulation. It does not include DUACS mapping errors, inter-mission calibration uncertainty, geophysical correction uncertainty, glacial-isostatic-adjustment-related bias, or uncertainty in the forced sea-level response. Thus, this study provides a model-based framework for estimating the internal-variability contribution to regional sea-level trend uncertainty, rather than a formal detection-and-attribution separation or a complete uncertainty bound for satellite-altimeter-derived regional sea-level trends. Full article

We develop a unified information-theoretic framework for the analysis of cancer transcriptomic dysregulation across measurement modalities. Three functionals capture distributional, network-aware, and joint-dependence aspects of expression: the Shannon entropy with a Miller–Madow correction, the signalling entropy rate over the protein interaction graph, and the Gaussian total correlation on a principal-component projection. A closed-form algebraic expression yields a linear-time algorithm for the signalling entropy rate. A Compositional Dilution Lemma decomposes bulk entropy into intrinsic and compositional contributions, and a Cross-Modality Invariance Proposition provides an empirically falsifiable null hypothesis. Validation uses 700,202 single cells and 3942 bulk samples across five cancer types. Pan-cancer tumour elevation is significant at $p<{10}^{-7}$, and cross-modality testing on 4230 observations does not reject the interaction null at $p>0.5$. The invariance conclusion is corroborated by cancer-level paired sign-flip permutation, cancer-block bootstrap, and empirical distribution function tests, and the prognostic Cox regressions satisfy proportional-hazards diagnostics with cross-validation concordance of $0.696\pm 0.018$. Immune deconvolution against the LM22 signature validates cell-type-specific predictions, partitioning cancers into myeloid-driven and lymphoid-driven classes. Breast cancer Cox regressions instantiate the predicted orthogonality of distributional and network-aware functionals after immune adjustment. Full article

In this paper, we present a fast and effective method for Bidimensional Empirical Mode Decomposition (BEMD) of large images. The proposed approach is based on the integration and adaptation of the partition of unity (PU) algorithm with compactly supported radial basis functions (CSRBFs) within the BEMD method. While the traditional BEMD algorithm is computationally intensive due to its reliance on envelope interpolation, the novel approach overcomes this limitation, as demonstrated by both complexity analysis and experimental results. Results obtained from both synthetic and real images demonstrate significant improvements in computational efficiency and decomposition quality compared to the recent BEMD-CSRBF approach, which demonstrates an important advancement over traditional BEMD methods. These improvements are reflected in lower orthogonality index (OI) values and faster processing times compared to the BEMD-CSRBF method. Across the tested images, the proposed BEMD-PU method reduces the computation time by ($17.22\%$)–($69.94\%$) and decreases the OI by ($8.93\%$)–($62.23\%$) compared with BEMD-CSRBF; on average, the computation time and OI are reduced by ($44.76\%$) and ($31.49\%$), respectively. Consequently, the proposed method performs exceptionally well with large images, making it an efficient tool for image processing. Full article

This study investigates the forecast bust of Typhoon SHANSHAN (2024) characterized by large track errors using the four major interactive grand global operational ensemble data and the atmospheric reanalysis data. Ensemble space empirical orthogonal function (EOF) analysis is applied to 850, 500, and 300 hPa geopotential heights at three target times to diagnose how synoptic-scale uncertainty contributed to the erroneous motions of SHANSHAN. We align the multi-level EOF bases to a reference-time basis via a weighted Procrustes rotation and evaluate similarity to the atmospheric reanalysis data in the aligned principal component (PC) space, enabling robust, distance-based conditioning of ensemble members. Results show that ensemble spread is consistently larger in the mid-latitudes, with relatively large uncertainty concentrated around the upper-tropospheric trough and lower-tropospheric structure near SHANSHAN. The dominant EOF modes differ by phase of SHANSHAN: lower-tropospheric modes govern the westward-moving stage, whereas mid- and upper-tropospheric modes dominate after recurvature. Selecting members whose EOF-based PC structures most closely match the atmospheric reanalysis effectively suppresses large-error outliers and yields improved conditional track predictions. These findings highlight phase-dependent synoptic controls and demonstrate that adaptive, reference-consistent conditioning can enhance the track guidance of tropical cyclones during difficult forecast situations. Full article

Substantial uncertainties remain in climate model simulations of tropical cyclones (TCs), particularly those associated with internal climate variability. While the influence of the El Niño–Southern Oscillation (ENSO) on interannual TC variability is well established, the contribution of the Interdecadal Pacific Oscillation (IPO) to decadal-scale uncertainty is less well constrained. Although models generally reproduce IPO-related variations in tropical cyclone genesis frequency (TCGF) over the eastern North Pacific, large discrepancies persist across the broader North Pacific basin. Clarifying the role of IPO in modulating TCGF uncertainty is therefore essential for improving decadal TC projections. In this study, we analyzed a large ensemble of historical simulations from the MRI-AGCM within the d4PDF (Database for Policy Decision Making for Future Climate Change) framework. Empirical orthogonal function (EOF) analysis is applied to IPO-composited fields to identify the leading modes of intermember (100 members *60 y, 6000 times) simulation uncertainty on a decadal-scale. The results reveal that state-of-the-art models exhibit robust and spatially coherent uncertainty structures in TCGF under different IPO phases. Two leading modes are identified: (1) a South China Sea mode, closely associated with systematic precipitation biases, and (2) a zonal dipole mode between the eastern and western North Pacific, linked to the equatorward propagation of Arctic Oscillation (AO)-related variability. Misrepresentation of AO variability is found to contribute substantially to biases in simulated TCGF patterns. Comparisons with observational datasets further support the proposed mechanisms. These findings highlight the importance of improving the representation of precipitation processes and extratropical–tropical teleconnections in climate models, which is critical for enhancing the reliability of decadal predictions of North Pacific TC activity. Full article

As a critical trace gas and a sensitive indicator of climate change, water vapor (H₂O) plays a pivotal role in regulating the Earth’s radiative budget and middle-atmospheric chemical cycles. In this study, H₂O measurements from the Sounding of the Atmosphere using a Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite are analyzed to characterize the H₂O spatiotemporal distribution throughout the stratosphere–mesosphere–lower thermosphere (SMLT) region. Using eigen analysis, the bimonthly mean H₂O across different latitude bins between 2002 and 2025 is decomposed into four empirical orthogonal functions (EOFs). Results indicate that stratospheric water vapor remains relatively stable with weak latitudinal dependence, whereas H₂O in the mesosphere–lower thermosphere (MLT) at middle-to-high latitudes exhibits pronounced seasonal variations and distinct hemispheric antisymmetry. The first mode captures a global H₂O long-term increasing trend. Both EOF1 and EOF2 are associated with solar activity and the El Niño–Southern Oscillation (ENSO) to varying degrees, indicating that these dominant modes are driven by multiple concurrent forcing factors. EOF3 correlates with the Quasi-Biennial Oscillation (QBO), suggesting links to QBO-driven atmospheric dynamical processes, whereas EOF4 demonstrates no significant associations with natural activity indices, suggesting perturbations arising from alternative atmospheric mechanisms. By systematically applying EOF analysis to a 24-year dataset of H₂O observations in the SMLT region, this study characterizes the principal distribution patterns and evolutionary characteristics of SMLT H₂O. Through correlation analyses with natural forcing indices, the complex driving mechanisms governing its variability are elucidated. This work provides a comprehensive observational framework for SMLT water vapor variability, enhancing assessments of SMLT H₂O responses to long-term climate change and refining the understanding of the Earth–atmosphere system. Furthermore, these findings provide critical data support for the subsequent development and optimization of SMLT water vapor models. Full article

Based on monthly meteorological observations from 57 stations in Jiangsu Province during 1961–2022, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated to characterize regional dry–wet variability. Empirical Orthogonal Function (EOF) analysis was applied to extract the dominant spatially coherent dry–wet modes, and cross-wavelet analysis was further employed to examine, in the time–frequency domain, the mode-specific responses to multiscale climate drivers, including the El Niño–Southern Oscillation (ENSO), Sunspot Number (SSN), Arctic Oscillation (AO), and Pacific Decadal Oscillation (PDO). The results show that dry–wet variability in Jiangsu Province is primarily organized by a regionally coherent mode (EOF1, explaining 56.3% of the total variance) and a north–south dipole mode (EOF2, explaining 17.8%), with the zero-value line of EOF2 closely aligned with the Huaihe River–Subei Irrigation Canal climatic transition zone. The temporal coefficient of EOF1 (PC1) exhibits a significant regime shift around 2013, followed by a pronounced wetting trend across the entire region. This change may reflect recent hydroclimatic adjustments in the study area, although the present study does not attempt a formal attribution of the respective thermal and precipitation contributions. In contrast, the temporal coefficient of EOF2 (PC2) undergoes an abrupt change around 1980, indicating a transition of the spatial dry–wet pattern from “southern drought–northern flood” to “southern flood–northern drought,” broadly consistent with an interdecadal climatic transition. Cross-wavelet analysis further reveals that PC1 is closely associated with ENSO at interannual timescales, with a lag of approximately 4–6 months, while its long-term variability shows time–frequency coherence with SSN. PC2 also exhibits time–frequency coherence with SSN at longer timescales, with an apparent phase transition around the 1980s; however, this low-frequency signal should be interpreted cautiously because the underlying physical mechanism remains uncertain. Overall, this study shows that dry–wet variability in Jiangsu Province is organized by two leading spatial modes with distinct temporal evolution and scale-dependent climate linkages. These findings provide new evidence for understanding hydroclimatic variability in monsoon transition zones and offer a basis for spatially differentiated drought–flood risk assessment. Full article

This study characterizes the structure and variability of baroclinic semidiurnal tidal currents at the head of the Biobio Submarine Canyon (BbC), off central Chile, based on Acoustic Doppler Current Profiler (ADCP) and moored thermistor-chain observations from two deployments conducted in 2013 and 2014 under contrasting stratification conditions. The results show that the head of the BbC is a dynamically active site of semidiurnal variability, with markedly stronger and more coherent baroclinic motions during the more stratified winter–spring 2014 period. During that deployment, semidiurnal baroclinic current amplitudes reached up to 17 cm s⁻¹, and the associated energy was concentrated near the surface and bottom. Rotary spectral analysis indicated that these semidiurnal baroclinic currents rotated anticyclonically and were closely aligned with the canyon axis. Empirical orthogonal function (EOF) analysis further showed that their vertical structure was dominated by a first baroclinic mode, which explained more than 70% of the semidiurnal baroclinic variance in 2014. In contrast, the 2013 deployment exhibited weaker and less coherent semidiurnal baroclinic variability. Taken together, these results indicate that stronger stratification favored the development of semidiurnal internal-tide-related motions over the canyon head and that the BbC provides a dynamically favorable setting for enhanced semidiurnal internal-tide activity and potentially elevated mixing, although direct turbulence or dissipation measurements were not available in this study. These findings have potential implications for local water-column structure, nutrient supply, and primary productivity in this highly productive coastal region. Full article

Environmental loading is a major driver of nonlinear GNSS vertical displacements, yet its spatiotemporal heterogeneity remains insufficiently understood in regions with complex topography. In this study, we investigate the environmental loading effects on GNSS vertical motions across Southwest China using observations from a network of 66 stations. Singular Spectrum Analysis (SSA) and Empirical Orthogonal Function (EOF) analysis were applied to extract annual signals, while component-wise RMS reduction quantified hydrological and atmospheric loading contributions. Spatial statistical analysis, cross-wavelet transform, and k-means clustering examined correlation patterns and phase hysteresis between GNSS observations and modeled loads. Results show that hydrological loading dominates seasonal vertical oscillations, but crustal responses exhibit pronounced spatial heterogeneity controlled by regional topography and hydro-climatic gradients. EOF analysis reveals a dipole pattern induced by the Hengduan Mountains’moisture-blocking effect. Atmospheric loading anomalously dominates the eastern Sichuan Basin, whereas Yunnan displays strong amplitudes with high heterogeneity due to karst hydrogeology. Phase analysis identifies three distinct regimes: a rapid elastic response on the Tibetan Plateau, (with the lag of ~20 ± 5 days, correlation coefficient R ≈ 0.65), intermediate delays in Yunnan (~60 ± 5 days, R ≈ 0.58), and pronounced hysteresis in the Sichuan Basin (~105 ± 5 days, R ≈ 0.38) linked to slow groundwater diffusion and poroelastic processes. These findings highlight the critical role of local hydrogeological dynamics in modulating GNSS vertical deformation and provide new insights for improving environmental loading corrections in complex mountainous regions. Full article

Wind energy is an important form of clean energy, and its rational utilization represents a crucial solution for mitigating the energy crisis and global warming. In this study, wind energy potential and its long-term changes in the South China Sea (SCS) are evaluated using ERA5 100 m wind data from 1944 to 2023, validated against ASCAT observations. High wind speeds and high wind power density (WPD) are concentrated southwest of Taiwan and southeast of Vietnam. Annual wind availability exceeds 6457 h across most regions, reaching up to 8283 h in optimal locations. WPD and capacity factor peak in winter (up to 2.4 × 10⁸ Wh·m⁻² and >50% capacity factor), with the most stable conditions occurring in the southwestern Taiwan Strait, southeast of the Pearl River Delta, and the Beibu Gulf. Empirical orthogonal function analysis reveals that the first mode of winter WPD accounts for 65.7% of the total variance, with a statistically significant increasing trend since 1990. The interannual variation in wind energy resources in the SCS during winter is controlled by the combined effects of sea surface temperature (SST) anomalies in the tropical Pacific and the Arctic Barents Sea. Specifically, in the years with strong wind anomalies in the SCS, mega-La Niña-type SST patterns in the tropical Pacific trigger anomalous cyclonic circulation in the SCS and the eastern Philippine Sea, while warm anomalies in the Arctic Barents Sea surface drive a wave-like structure of “anticyclone–cyclone–anticyclone” from Siberia to South China. The coupling of the two systems jointly promotes the strengthening of the South China Sea monsoon, leading to increased wind speeds and elevated WPD in the northern SCS. These findings provide a scientific basis for wind farm siting and long-term operational planning in the region. Full article

The significant interannual variability in Madden–Julian Oscillation (MJO) intensity remains incompletely understood. Empirical orthogonal function (EOF) analysis reveals that the first three leading EOF modes of the annual mean MJO intensity are significantly correlated with the Quasi-Biennial Oscillation (QBO), Eastern Pacific El Niño-Southern Oscillation (ENSO), and Central Pacific ENSO. Focusing on the distinct EOFs related to three key tropical interannual variabilities, we conduct an investigation into the potential governing processes through which the changes in background mean states impact MJO intensity based on the MJO moisture mode theory. Observations suggest that the accumulation of moist static energy (MSE) during MJO moistening phases and its dissipation during drying phases play a crucial role in regulating MJO amplitude. At the interannual timescale, regions characterized by positive EOF values display positive (negative) MSE tendency anomalies during MJO moistening (drying) phases, leading to amplified MSE accumulation (dissipation) throughout the MJO lifecycle and subsequently facilitating an increase in MJO amplitude. Conversely, regions with negative EOF values exhibit opposing trends. Further analysis reveals that these MSE tendency anomalies are mainly associated with the zonal advection term, which is influenced by interannual changes in the background mean MSE and low-level winds. The spatial pattern of the background mean MSE is strongly linked to sea surface temperature (SST) anomalies, with low-level background winds aligning well with the horizontal gradients of SST anomalies. Full article

Drought is a complex natural hazard with severe impacts on ecosystems, agriculture, water resources, and socio-economic stability. Understanding its spatiotemporal evolution is critical for effective drought monitoring and prevention. This study analyzed drought characteristics in Henan province from 1961 to 2023 using the Standardized Precipitation Evapotranspiration Index (SPEI), calculated from daily meteorological data at 111 meteorological stations. Drought was examined at annual and seasonal scales across multiple time scales, including the 1-month time scale (SPEI1), 3-month time scale (SPEI3), and 12-month time scale (SPEI12), and future trends were assessed using Theil–Sen Median and Hurst exponent analyses. Key findings revealed the following: (1) Drought frequency showed a non-significant increasing trend overall, but drought intensity increased significantly, with severe and extreme droughts becoming more frequent. Most areas are projected to continue aridification. (2) Winter recorded the highest frequency and occurrence of droughts, followed by autumn and summer. Except for summer, moderate and severe droughts increased across all seasons. Extreme droughts increased significantly across all seasons, especially in spring and autumn. (3) High annual drought frequency was concentrated in the northwest, north, and east. Spatial patterns varied by drought severity: slight droughts were more common in the north, moderate droughts in the central–east, severe droughts in the west and south, and extreme droughts in the southwest and north. (4) Empirical Orthogonal Function (EOF) analysis revealed three main spatial modes: a uniform regional pattern, a southeast–northwest contrast, and a central–eastern opposition. Shorter time scales provided more detailed spatial patterns, while longer scales better reflected interannual characteristics of drought and flood variations. This study offers valuable insights for improving drought assessment and supporting risk management and policy decisions. Full article

The mechanisms by which the regional hydroclimate responds to global climate forcing are complex, particularly in geographically heterogeneous countries like China. Focusing on Hunan Province, this study employs the Standardized Precipitation Index (SPI) derived from long-term precipitation records at 87 meteorological stations to delineate climatic sub-regions with coherent dry–wet variability. Using rotated empirical orthogonal function analysis, we systematically characterize the spatiotemporal patterns of SPI components and quantify their teleconnections with global ocean–atmosphere circulation modes. The analysis of multi-timescale SPI reveals four distinct sub-regions and a pronounced northwest–southeast dipole in long-term trends. Despite an overall reduction in annual drought, the northwestern sub-region experienced intensification. Seasonally, a pattern of spring/autumn drying versus summer/winter wetting emerged. Wavelet analysis identified dominant interannual (2–7 years) and interdecadal (13–71 months) oscillations. These periodicities are significantly teleconnected to large-scale circulation indices (e.g., Southern Oscillation and Pacific Decadal Oscillation), with influences peaking at 16–64-month and 2–5-year scales. Importantly, the primary circulating driver differs by sub-region, revealing a complex teleconnection landscape. The findings delineate region-specific atmospheric pathways, offering insights to bolster drought preparedness and optimize water allocation, thereby enhancing climate resilience in vulnerable monsoon transition zones. Full article

Accurate three-dimensional (3D) salinity fields are crucial for diagnosing freshwater transport and upper-to-intermediate ocean dynamics, yet subsurface salinity observations remain uneven in space and time, especially away from primary observing corridors. Gridded fields derived from sparse measurements can also suffer from regional biases and over-smoothing, which may blur mesoscale signals in energetic regimes. This study presents an empirical orthogonal function-guided U-shaped Vision Transformer (EOF-UViT) to reconstruct daily 3D salinity in the Northwest Pacific (0–50°N, 100–150°E) from multi-source surface remote-sensing factors. Compared with the U-Net baseline and the Modular Ocean Data Assimilation System (MODAS) reconstruction, EOF-UViT produces more realistic horizontal structures and improved vertical consistency, with the largest gains in dynamically active regions. Comparison with collocated in situ profiles further supports the reconstruction skill (RMSE = 0.094 psu; R² = 0.904), with estimates clustering more tightly around the 1:1 line than MODAS. Overall, EOF-UViT provides an efficient, observation-driven route to spatially coherent 3D salinity fields, supporting applications such as model initialization, assimilation background fields, and basin-scale salinity variability analysis. Full article

This study uses satellite altimeter data from the new AVISO dataset to investigate the coupling between sea level variability in the Sicily Channel and the Ionian Sea. The dataset spans the last three decades (1993–2024) and provides high spatial resolution coverage of the Mediterranean Sea (1/16°, or approximately 7 km). We analyze the variability of the sea surface height through Empirical Orthogonal Function and Singular Value Decomposition techniques applied to the Absolute Dynamic Topography. While the dominant modes of long-term variability reflect the known dynamics of the North Ionian Gyre, the singular value analysis allows us to identify a coherent spatial structure extending from the Sicily Channel to the Northern Ionian Sea. This provides the first observation-based, robust evidence of a dynamical coupling between the two basins, indicating that in the last thirty years the Northern Ionian Gyre is part of a broader, dynamically connected regional system integrating flows from the Sicily Channel. These findings are consistent with previous work, based on a hindcast simulation covering 1980–2010, in which we highlighted the key role of the Atlantic Ionian Stream in shaping interannual to decadal variability in the Northern Ionian Sea. Here, we extend the analysis to the present day, providing the most up-to-date, observation-based assessment of the regional dynamics. Full article