Search Results (814)

The Indian Ocean Dipole (IOD) and the El Niño-Southern Oscillation (ENSO) are two major modes of interannual climate variability that interact across the Indo-Pacific region. Although the autumn IOD is known to influence ENSO with a lag of about one year, the decadal stability of this relationship remains poorly understood. Here we investigate the decadal variability of the lagged IOD–ENSO relationship using observations and 30 Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Observational analyses reveal pronounced non-stationarity in the lagged IOD-ENSO linkage, characterized by a stronger (weaker) relationship during the negative (positive) phase of the Atlantic Multidecadal Oscillation (AMO). CMIP6 models exhibit a wide spread in their ability to reproduce this behavior, with only a subset capturing the observed decadal modulation. The inter-model differences are consistent with variations in the simulated amplitude of AMO variability. Models with more realistic AMO variability tend to better reproduce the observed decadal variability of the lagged IOD-ENSO linkage. These results suggest that AMO variability may be one contributing factor to the modulation of the lagged IOD–ENSO relationship, with potential implications for ENSO prediction. Full article

This study examines the long-run relationship between terms of trade (TOT) and real fishing-sector GDP in a small open economy, focusing on the Peruvian case. Despite the strategic importance of fisheries for exports, employment and foreign exchange generation, the extent to which external price conditions are associated with fishing-sector performance remains insufficiently explored in sector-level research. Building on the notion that TOT summarise opportunities and constraints arising from the international environment, the paper evaluates whether persistent external conditions are linked to the long-run trajectory of the fishing sector. The analysis employs the Johansen cointegration approach and a bivariate Vector Error Correction Model (VECM) using quarterly data for the period 2001–2025. Seasonal effects are incorporated through quarterly dummy variables, while robustness is assessed by controlling for extreme El Niño–Southern Oscillation (ENSO) episodes and the COVID-19 pandemic. The results reveal the existence of a unique long-run equilibrium relationship between TOT and fishing-sector GDP. The error-correction mechanism indicates that deviations from equilibrium are actively corrected over time, whereas the adjustment coefficient for TOT is statistically insignificant. Robustness tests further show that El Niño episodes are negatively and significantly associated with short-run sectoral performance, while no statistically significant association is detected for La Niña. The COVID-19 control does not materially alter the long-run relationship identified by the model. The findings contribute sector-level evidence for a resource-dependent economy and suggest that long-run equilibrium and sectoral adjustment dynamics are important elements for understanding the long-run behaviour of the fishing sector. Full article

El Niño–Southern Oscillation (ENSO) modulates tropical South American rainfall, but its Colombian expression is filtered by terrain, rainfall regime, moisture pathways, and atmospheric state. We quantify ENSO-related sensitivity of standardized precipitation anomalies in the Colombian Andes and Orinoquia using Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS v2.0; 1981–February 2026), station records from Colombia’s Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM), ERA5 atmospheric fields, and 1981–2010 climatologies. CHIRPS reproduced station-derived standardized anomalies ($r=0.94$ in the Andes; $r=0.91$ in Orinoquia), supporting regional anomaly analysis while retaining cautious comparison framing. Lagged associations with the Oceanic Niño Index (ONI) were evaluated for lags 0–6 months using effective sample size, block-bootstrap confidence intervals, and maximum-lag tests. ENSO sensitivity was stronger and more coherent in the Andes: annual lag-1 ONI–precipitation correlation was $-0.374$, with marked December–February and June–August responses. El Niño minus La Niña composites of column water vapor, 850-hPa moisture-flux convergence, 500-hPa vertical velocity, and Convective Available Potential Energy (CAPE) revealed seasonally heterogeneous moisture and convergence responses, but coherent positive $\omega$ anomalies over the Andes in DJF and JJA, consistent with reduced ascent. CAPE was significantly higher in MAM–SON, whereas the positive DJF difference was not statistically significant, showing that thermodynamic instability alone did not determine rainfall. Orinoquia did not exhibit a comparably consistent four-variable atmospheric signature. An elevation-stratified analysis showed a modest lowland-to-upland strengthening that plateaued above approximately 1000 m. A strictly antecedent ONI-lag model retained modest fixed-split skill in the Andes ($R^2=0.138$) but negligible skill in Orinoquia ($R^2=0.003$). The results support regional diagnosis, not causal or operational claims. Full article

Chikungunya is undergoing global expansion, but how El Niño–Southern Oscillation (ENSO) influences its transmission remains unclear. We aim to assess the impact of ENSO phases on chikungunya incidence via temperature and precipitation teleconnections and to project future risk burden under climate change. We compiled annual national and subnational chikungunya case data (2008–2024), quantified ENSO–climate teleconnections using the E-index (eastern Pacific El Niño) and C-index (central Pacific La Niña), and applied distributed-lag time-series models to assess the teleconnection-mediated impact of ENSO on chikungunya incidence. We further projected future risk burden under climate change scenarios. Modelling shows that El Niño increased chikungunya risk after a 2-year lag (cumulative relative risk [CRR] = 1.40, 95% confidence interval [CI]: 1.02–1.85), while La Niña suppressed it (CRR = 0.09, 95% CI: 0.07–0.13). Temperature teleconnections were the dominant modifier of spatial heterogeneity in effects. Under all scenarios, El Niño-driven warming led to positive median excess cases, the highest under SSP2-4.5, whereas La Niña-driven changes projected smaller, highly uncertain reductions. ENSO influences chikungunya transmission through asymmetric and spatially heterogeneous teleconnection pathways. Integrating ENSO forecasts into surveillance efforts has the potential to enhance preparedness in climate-sensitive regions. Full article

Based on daily precipitation observations from six national meteorological stations in the Zhangye region from 1960 to 2023, this study examines the spatiotemporal evolution and possible driving factors of extreme precipitation using four ETCCDI-recommended indices (SDII, R10mm, R95p, and RX1day). Trends were evaluated using linear regression and the Mann–Kendall test, with Sen’s slope estimation. The results reveal significant (p < 0.05) increasing trends in both the frequency and intensity of extreme precipitation, with a shift from low-intensity, low-frequency to high-intensity, high-variability modes. Temporally, all indices exhibited a step-like surge around 2000, entering a period of high-level oscillation, with extreme characteristics amplified during strong El Niño years. Spatially, a distinct “higher in the south, lower in the north” pattern prevails among the six stations, with the southern Qilian Mountains being the primary contributor and the central plains showing a bimodal distribution, reflecting joint modulation by westerly troughs and local strong convection. The intensification is linked to enhanced atmospheric water vapor, northward penetration of the East Asian summer monsoon, and topographically forced lifting. While alleviating drought stress, this trend substantially elevates the risk of flash floods and debris flows in mountainous areas. It should be noted that the spatial patterns are derived from six stations and should be interpreted as inter-station comparisons rather than continuous spatial fields. Full article

Assessing long-term hydroclimatic variability in central Mexico is essential to understand regional water availability and groundwater recharge for urban centers such as Querétaro. This study developed a multi-century winter–spring precipitation reconstruction for the Sierra Gorda Biosphere Reserve (SGBR) using ring width chronologies of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco. Standard dendrochronological techniques were applied to develop a 284-year master chronology (1731–2015). Following the accepted Subsample Signal Strength criterion (SSS ≥ 0.85) for chronology reliability, the reconstruction was restricted to the 1744–2015 period, yielding a statistically robust 271-year December–April precipitation record. A bootstrapped ordinary least-squares regression model relating tree-ring indices to instrumental December–April precipitation was calibrated and validated using split-sample cross-validation, explaining 46% of the instrumental precipitation variance (R² = 0.46) and yielding positive verification statistics (RE = 0.38–0.58; CE = 0.37–0.57). Spatial field correlations against gridded climate data (CRU TS4.08) confirmed a broad regional hydroclimatic signal centered over the Sierra Madre Oriental. Continuous wavelet transform (CWT), spectral analysis, superposed epoch analysis (SEA), and wavelet coherence (WTC) revealed significant interannual (2–8 years) and decadal (10–20 years) variability associated with large-scale ocean–atmosphere climate modes, including the El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and Tropical North Atlantic (TNA) index. The pronounced sensitivity of these conifer forests to pre-monsoonal moisture deficits highlights their vulnerability to projected warming and increasing spring evapotranspiration stress. Although the reconstruction is limited to pre-monsoonal (December–April) precipitation, it provides a robust centuries-long baseline for contextualizing regional hydroclimatic variability and supports water-resource management, groundwater conservation, and climate-adaptation strategies in central Mexico. Full article

Whale shark aggregations in tropical coastal systems are linked to environmental variability and prey dynamics, yet the drivers of surface sightings remain poorly understood. In Nosy Be, Madagascar, a seasonal aggregation of immature whale sharks occurs within a productive coastal ecosystem. This study investigated the relationship between daily environmental conditions and whale shark surface sighting probability while accounting for heterogeneous sampling effort. Boat-based survey data collected from 2019 to 2025 were aggregated by sampling day, and daily whale shark surface sighting probability was analysed using a bias-reduced grouped binomial Generalized Linear Model. Environmental covariates included sea surface temperature, sea surface chlorophyll-a concentration, cloud cover, wind speed, and precipitation, while El Niño–Southern Oscillation variability was assessed as an interannual climatic descriptor. Using data from 103 recorded whale shark surface sightings, chlorophyll-a emerged as the strongest predictor, showing a positive association with daily sighting probability, whereas other environmental variables exhibited weaker and inconsistent effects. These findings suggest that whale shark surface sightings in Nosy Be are primarily associated with prey aggregation processes driven by local productivity rather than with direct responses to local physical environmental conditions. By integrating environmental variability and sampling effort into ecological models, this study provides insights into whale shark habitat use and supports ecosystem-based management of sustainable whale shark tourism in tropical coastal ecosystems. Full article

Climate variability can modulate zoonotic disease risk by altering interactions among wildlife hosts, vectors, and human environments, yet long-term evidence linking large-scale climate oscillations to natural plague systems remains scarce. We investigated the influence of El Niño–Southern Oscillation (ENSO)-related climate variability on rodent host dynamics in a long-established plague focus in Jianchuan County, southwestern China. Using continuous monthly surveillance data from 1978 to 2025, we analyzed population dynamics of two ecologically distinct plague hosts—the wild rodent Apodemus chevrieri and the domestic rodent Rattus tanezumi—together with flea infection rates and local climate variables. Generalized additive models showed that ENSO, quantified by the Southern Oscillation Index (SOI), exerted significant delayed effects on both rodent populations, with El Niño conditions consistently associated with increased host abundance. Wavelet coherence analyses revealed synchronized ENSO–rodent oscillations at dominant 2–3-year periodicities, indicating persistent large-scale climate forcing. In contrast, responses to local environmental factors differed between species: surface temperature strongly constrained the wild rodent A. chevrieri, whereas the domestic R. tanezumi showed weaker thermal sensitivity, consistent with buffering by human-modified indoor habitats. Flea infection rates declined as rodent densities increased, suggesting a dilution effect within the host–vector system. By integrating long-term wildlife surveillance, climate indicators, and vector data, this study provides empirical evidence that ENSO-driven climate variability plays a central role in regulating plague source activity at the human–animal–environment interface. These findings highlight the value of climate-informed, ecology-based surveillance frameworks for anticipating periods of elevated plague risk and strengthening early warning systems in endemic regions. Full article

Urban green spaces (UGSs) are vital for enhancing a city’s resilience and livability; however, their functionality is increasingly jeopardized by drought, particularly in water-scarce regions. This study evaluates drought impact on UGSs in Metropolitan Adelaide, Australia, a representative semi-arid urban system, using satellite-derived Normalized Difference Vegetation Index (NDVI) time-series data spanning 2000–2020. Vegetation dynamics were analyzed through Seasonal-Trend decomposition using Loess (STL), standardized anomaly assessment, lagged Pearson correlation, Ordinary Least Squares (OLS) regression, and Mann–Kendall trend analysis. To isolate climatically sensitive signals, 29 urban lawn patches were examined separately from mixed urban canopy, given their shallow root systems and direct dependence on surface moisture. NDVI declined by approximately 0.09 units during the Millennium Drought (2001–2009), with summer greenness deficits reaching 24% below the 20-year benchmark. Temperature was the dominant driver of lawn NDVI variability (r = −0.863, R² = 74.5%), substantially exceeding the effect of rainfall (r = 0.156, R² = 2.4%). El Niño–Southern Oscillation (ENSO) cycles modulated vegetation responses, with La Niña years supporting recovery and El Niño years amplifying decline. Post-drought recovery remained incomplete, with NDVI deficits of 8–20% persisting through 2020; full recovery was observed only in 2017, coinciding with the highest recorded summer rainfall. No significant directional trend was detected over the full study period (Mann–Kendall τ = 0.005, p = 0.908). These findings demonstrate that heat, rather than water limitation alone, is the primary driver of vegetation stress in urban systems, highlighting the benefits of integrated management strategies that address both warming and moisture deficits to sustain urban green infrastructure under future climate conditions. We introduce the concept of “urban greenery drought,” referring to a form of vegetation stress in managed urban landscapes where greenness is reduced primarily by elevated temperature and atmospheric demand despite water availability. Full article

East China is a global hotspot for landfalling tropical cyclones (TCs). While previous studies have extensively examined the influence of El Niño–Southern Oscillation (ENSO) on TC activity, whether and how ENSO alters the spatial organization of precipitation in landfalling TCs remains insufficiently understood. Using high-resolution satellite precipitation observations and ERA5 reanalysis data, this study investigates the heterogeneous responses of landfalling TC precipitation over East China to different ENSO phases. Composite analyses indicate ENSO-associated differences in TC precipitation at both regional and storm-relative scales. At the regional scale, positive composite precipitation differences occur over Fujian, southern Zhejiang, and Taiwan during El Niño years, whereas negative differences occur in parts of northern East China relative to La Niña years. At the storm-relative scale, mean outer-rainband precipitation was estimated to be 26.02% higher during El Niño years; however, the storm-level bootstrap 95% confidence interval included zero, indicating uncertainty associated with the limited number of independent TC events. Precipitation during La Niña years was relatively more concentrated within the inner-core region. Mechanistic diagnostics show that the El Niño composite is associated with differences in thermodynamic and dynamic conditions, including higher low-level cyclonic vorticity, upper-level divergence, ascent, and anomalous steering flows over southern East China and adjacent seas. TC-centric analysis further indicates that higher moisture supply and dynamic lifting coincide with the outer-rainband precipitation contrast during El Niño years. These findings suggest that ENSO is associated with spatially heterogeneous and structurally distinct responses of landfalling TC precipitation over East China, providing a diagnostic basis for understanding ENSO-related differences in regional TC precipitation risk. Full article

Understanding the interactions between vegetation dynamics and surface water availability is essential for assessing the resilience of tropical floodplain ecosystems under increasing hydroclimatic variability. This study analyzes the spatio-temporal dynamics of vegetation cover, surface water, and land use in Zambrano, a floodplain-dominated sector of the lower Magdalena River basin (Colombian Caribbean), over the period 1990–2025. Multi-temporal Landsat imagery was used to derive the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Water Index (NDWI), enabling the evaluation of seasonal and interannual ecohydrological variability under contrasting dry and rainy conditions. In addition, land-use classification was performed using a CORINE Land Cover methodology adapted for Colombia (CLC-C) to characterize the spatial organization of the landscape and its influence on vegetation–water interactions. Results show that vegetation dynamics are strongly controlled by hydroclimatic seasonality. Dense vegetation consistently expands during rainy periods, while dry seasons promote the expansion of open and sparse vegetation, reflecting seasonal vegetation stress rather than long-term degradation. NDWI patterns indicate that surface water and soil moisture are highly seasonal and spatially constrained, with open water largely confined to the Magdalena River channel and localized floodplain depressions. Extreme hydroclimatic events associated with the El Niño–Southern Oscillation (ENSO) produce abrupt but temporary changes in vegetation structure and surface moisture distribution. A strong inverse correlation between NDVI and NDWI reflects the contrasting spectral responses of vegetation and water surfaces resulting from the shared near-infrared (NIR) band in both indices. This spectral relationship is consistent with the observed seasonal variations in vegetation greenness and surface moisture across the floodplain. Land-use analysis reveals the progressive consolidation of the landscape, where the agropastoral matrix expanded from ~18,000 ha in 1990 to over 22,000 ha by 2025, driving a systematic reduction in natural and semi-natural forest structures. Forest conservation areas serve as critical ecological buffers, exhibiting lower seasonal variability in vegetation greenness. Overall, the results indicate that the Zambrano floodplain functions as a structurally stable yet highly responsive ecohydrological system, where vegetation dynamics and surface water availability are predominantly governed by interannual hydroclimatic pulses rather than long-term directional degradation. These findings demonstrate that while the structural matrix of the floodplain exhibits strong baseline resilience, its ecological functioning remains critically coupled with, and vulnerable to, the extreme phase shifts in ENSO cycles. Full article

Climate change poses significant environmental and socio-economic challenges for Small Island Developing States (SIDS), including Timor-Leste. This systematic review aimed to synthesise evidence on climate change impacts, vulnerabilities, adaptation pathways, and research gaps in Timor-Leste. Following PRISMA 2020 guidelines, literature searches were conducted in Web of Science, Scopus, and Google Scholar through May 2025. Eligible sources included peer-reviewed studies, technical reports, policy documents, and institutional publications. Source quality was assessed based on relevance, methodological consistency, credibility, and thematic contribution, and evidence was synthesised using a qualitative meta-synthesis approach. A total of 79 peer-reviewed studies and 8 international reports met the eligibility criteria, resulting in a final corpus of 87 documents. The evidence indicates a warming trend of 0.16 °C/decade and a sea-level rise of 5.5 mm/year with significant implications for agriculture, food security, water resources, and coastal systems. Approximately 70% of the population depends on climate-sensitive livelihoods, increasing exposure to climate-related risks. Evidence remains limited by data scarcity and methodological heterogeneity. Overall, Timor-Leste faces substantial climate vulnerability, highlighting the need for strengthened adaptation planning, improved climate information systems, and targeted policy interventions. Full article

The Agulhas Current system, the strongest western boundary current in the Southern Hemisphere, plays a key role in regulating carbon cycling in the southwestern Indian Ocean. However, the variability of particulate organic carbon (POC) and its response to climate forcing remain poorly understood. Using multi-source satellite observations and reanalysis data from 1998–2025, we investigated the spatial, seasonal, interannual, and decadal variability of POC, chlorophyll-a (Chl-a), and POC:Chl-a in the Agulhas Current system. Our results show that Chl-a and POC concentrations are consistently higher in the Agulhas Retroflection than in the Return Current region, reflecting enhanced mesoscale activity and nutrient supply. Seasonally, Chl-a and POC peaked during austral spring–summer and declined during autumn–winter, whereas POC:Chl-a exhibited an opposite cycle driven by variations in light availability and mixed-layer depth. At interannual timescales, ENSO exerted a pronounced influence on POC variability. El Niño events increased Chl-a and POC by up to 0.3 mg m⁻³ and 30 mg m⁻³, respectively, while reducing POC:Chl-a by up to 60 g g⁻¹ through enhanced eddy activity and improved light conditions; the opposing anomalies occurred during La Niña events. Positive Southern Annular Mode (SAM), phases increased Chl-a and POC in the Return Current region by strengthening vertical mixing and nutrient entrainment. On multi-decadal timescales, contrasting regional trends resulted in a persistent increase in the POC:Chl—a ratio across both regions, suggesting a structural shift in the particulate carbon pool and an increasing decoupling between particulate organic carbon and phytoplankton biomass. These results highlight the combined roles of stratification, mesoscale dynamics, and climate modes in regulating regional carbon cycling and carbon-sink variability. Full article

Marine low clouds (MLCs) strongly affect Earth’s radiation budget due to their extensive coverage and strong reflection of incoming solar radiation. Despite their important role in the Earth system, the extent and mechanisms of MLC response to climate oscillations are not well understood. In this study, the effect of the El Niño–Southern Oscillation (ENSO) on cloud and meteorological properties across the Pacific Ocean is investigated by integrating various satellite observations and reanalysis datasets. The results reveal a pronounced hemispheric asymmetry in the response of subtropical MLCs to ENSO. During El Niño events, the Northeast Pacific exhibits reduced cloud cover and weaker shortwave radiative cooling, while an opposite response is observed over the Southeast Pacific, where cloudiness and radiative cooling are enhanced. These contrasting responses are linked to distinct ENSO-driven meteorological changes between the two hemispheres. Over the Northeast Pacific, El Niño conditions weaken inversion strength and the subtropical high, suppressing MLCs. In contrast, the Southeast Pacific experiences enhanced inversion strength and lower-tropospheric geopotential height during El Niño, which favor MLC development. It is suggested that hemispheric asymmetries in the climatological positions and ENSO-induced responses of the Pacific subtropical highs contribute to the opposite MLC responses between the two hemispheres. These findings highlight the importance of large-scale controls in shaping regional cloud responses to climate variability and provide insights for improving cloud representation in global climate models. Full article

Earthen archeological sites may be damaged by rain-induced erosion processes. Huaca Fortaleza (HF; 600–750 AD) is an originally four-level truncated pyramid in the semi-arid Lambayeque region of northern Peru, an area affected by seasonal intense rain due to El Niño Southern Oscillation (ENSO). We use data from a UAV-based photogrammetric survey and generate a Digital Surface Model from which we extract selected geomorphometric parameters and apply a hillslope diffusion model. The obtained data show that HF steep flanks exhibit a marked erosion expressed by a drainage network of parallel rills and gullies with architectural structures controlling pathways for concentrated flow. The southwestern flank is affected by gravity instability. Localized pits at the top of HF cause infiltration of rainwater. The erosion by ENSO rainfall is responsible for extensive architectural loss, with the HF lower platforms now entirely obliterated. We calculate vertical erosion rates of 0.28–0.38 m/century, a range of values comparable with that estimated for river incision. Erosion due to diffusion processes is estimated in the order of ~0.015 m/century. Our approach represents a transferable methodology applicable to other earthen archeological sites affected by erosion worldwide. Full article