Search Results (430)

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

This study evaluated seasonal variations in mesozooplankton carbon biomass in Laguna de Terminos, a tropical coastal lagoon of the Southern Gulf of Mexico and a designated Ramsar site. We compared data from two contrasting 2022 sampling periods, the dry season (April) and the rainy season (October), coinciding with a strong La Niña event. Through systematic expeditions, we collected hydrographic and biological data to estimate zooplankton carbon biomass and assess its relationship with prevailing climatic conditions. Our results revealed distinct seasonal shifts. While surface water temperatures were higher in October (30 °C) than in April (28 °C), salinity and total dissolved solids exhibited the inverse trend. Chlorophyll-a peaked in April (>5 mg m⁻³) near river discharges and the lagoon’s connection to the Gulf of Mexico. Consistent with this, zooplankton carbon biomass was higher in April (up to 77.2 mg C m⁻³) than in October (up to 48.4 mg C m⁻³), with maximum concentrations observed in the eastern section of the lagoon. Given the scarcity of published reports for this system, these findings establish a critical baseline for future environmental monitoring. Furthermore, this data is essential for evaluating the lagoon’s primary and secondary productivity potential and for estimating the carbon pool held within lower-trophic-level organisms that support higher-level consumer groups. Full article

This study investigates the relationship between ground heat flux (GHF) over the Tibetan Plateau and heatwave days in Korea. A weak negative correlation was found during the pre-1998 period (1979 to 1997), whereas a strong positive correlation emerged during the post period (1998 to 2019). To further examine the mechanisms underlying this interdecadal change, seven positive and seven negative GHF years were selected for both the pre-1998 and post-1998 periods and composite analyses were conducted. During positive GHF years in the post-1998 period, the Tibetan Plateau experienced enhanced surface heating, reduced spring snow cover, and lower summer soil moisture. These conditions favored greater absorption and release of heat from the land surface. Concurrently, anomalous anticyclonic circulation strengthened throughout the troposphere, accompanied by enhanced subsidence over the latitude band containing the Korean Peninsula. In addition, both the western North Pacific high and the South Asian high expanded and intensified during positive GHF years, exerting a stronger influence on the middle and upper troposphere over Korea. The increased occurrence of heatwaves in Korea during the post-1998 period is partly attributable to enhanced thermal forcing over the Tibetan Plateau and the associated development of a circumglobal teleconnection-like wave train, which induced downstream anticyclonic circulation anomalies over East Asia. This upper-tropospheric forcing, together with a La Niña–like or negative Pacific Decadal Oscillation–like sea surface temperature pattern, created atmospheric conditions favorable for more frequent heatwave events over Korea. These results suggest that the influence of Tibetan Plateau thermal forcing on Korean heatwaves has strengthened since the late 1990s through its interaction with large-scale atmospheric circulation and oceanic background conditions. 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

This study aims to examine whether and through which transmission channels physical climate risk becomes financially relevant in agricultural commodity markets. Using daily returns on seven agricultural futures over 2000–2025 and a Diebold–Yilmaz connectedness framework, this paper shows that the increase in agricultural connectedness during La Niña episodes is explained mainly by global risk aversion rather than by regional macro-financial conditions. A sequential decomposition indicates that the VIX accounts for most of the unconditional La Niña effect, while Latin American financial variables explain only a negligible share. After controlling for these factors, the residual climate effect becomes small and statistically insignificant under wild cluster bootstrap inference. Quantile results further show that La Niña raises the floor of connectedness in low-stress states but adds little in already-stressed regimes. The effect is economically relevant: relative to neutral conditions, La Niña increases the absolute one-day 95% CVaR by approximately 17%—from 2.39% to 2.80%—and reduces the diversification ratio by 12.9%, from 1.889 to 1.645. Overall, the results suggest that climate stress in agricultural markets is transmitted primarily through global uncertainty pricing, with direct implications for portfolio management and climate stress testing. Full article

La Paz Lagoon is a semi-enclosed coastal ecosystem in the southwestern Gulf of California that was historically affected by wastewater discharges and other anthropogenic disturbances. This study evaluated the taxonomic diversity and community structure of soft-bottom fish assemblages across two climatic periods (Neutral, 2016–2017, and La Niña, 2022–2023) using alpha (α), beta (β), and gamma (γ) diversity metrics together with taxonomic distinctness indices (Δ, Δ*, Δ+, and Λ+). Six bimonthly surveys were conducted during each climatic period at seven sampling stations. A total of 93 fish species, representing 65 genera, 33 families, and 17 orders, were recorded across the two climatic periods. Species richness exhibited marked temporal variation, reaching its highest value in April and its lowest value in March. Periods of reduced richness were associated with increased species turnover among stations. Taxonomic distinctness indices remained within the expected confidence limits, indicating a stable taxonomic structure despite historical anthropogenic impacts. Dominant species included Paralabrax maculatofasciatus, Diapterus brevirostris, Eucinostomus gracilis, Urobatis halleri, and Synodus scituliceps. Overall, the results indicate that the soft-bottom fish assemblage of La Paz Lagoon exhibits characteristics consistent with a stable and well-structured community. Multivariate analyses further identified water temperature as the principal environmental variable associated with community variation. Collectively, these findings support the hypothesis that La Paz Lagoon is undergoing ecological recovery and provide a robust ecological baseline for long-term monitoring, conservation, and ecosystem management. Full article

Drought is a recurring agricultural hazard in Northeast Thailand’s floodplain environments, yet the actual values of remote sensing indices at confirmed drought locations remain poorly characterized. This study characterized six remote sensing indices (NDVI, VCI, SMI, NDMI, MNDWI, NSMI) at 541 agricultural drought-reporting locations in the Chi River Basin, Maha Sarakham Province, across three years representing different ENSO phases (La Niña 2020, El Niño 2023, neutral 2024). Drought-reporting frequency was classified based on village-level alert frequency: high frequency (six alerts, n = 100 villages) and low–moderate frequency (≤3 alerts, n = 441 villages). Sentinel-2 imagery was processed for the January–May dry season. Due to non-independence of observations (repeated measurements and spatial autocorrelation), analyses focused on descriptive statistics and effect sizes (Cohen’s d) rather than formal hypothesis testing. Results revealed remarkably small mean differences between frequency classes (0.008–0.024), with uniformly small effect sizes (Cohen’s d = 0.20–0.22). VCI and MNDWI showed negligible differences (Cohen’s d = 0.124 and 0.094, respectively). Index values at high-frequency locations showed stability across years (CV < 7% for all indices except NDMI), with limited year-to-year variation. SMI and NSMI were perfectly correlated (r = 1.00), indicating mathematical redundancy. Provisional descriptive reference points were derived from the three-year dataset (NDVI ≈ 0.21, VCI ≈ 0.52, SMI ≈ 0.41, MNDWI ≈ −0.33 at high-frequency locations), but these are descriptive summaries only and require validation with longer time series before they can be considered for operational use. These findings demonstrate that individual remote sensing indices have limited discriminatory power in this sandy soil floodplain environment, where local factors—soil properties, topography, and irrigation access—dominate over regional climate forcing. Five policy-relevant observations are proposed, including re-evaluation of threshold-based early warning systems and prioritized irrigation investments based on static vulnerability factors. This study contributes to SDG 2 (Zero Hunger), SDG 6 (Clean Water), and SDG 13 (Climate Action) through improved understanding of drought monitoring limitations in floodplain environments. Full article

Understanding the physical mechanisms of compound hot-drought events (CHDEs) over the Yangtze River Basin (YRB) is essential for improving climate predictability. Using high-resolution observations and ERA5 reanalysis, this study conducted a three-dimensional comparative diagnosis of two spatially distinct CHDEs (August 2022 and 2019), deconstructing their circulation dynamics and thermodynamic budgets. Specifically, the 2022 basin-wide event was highly associated with La Niña and a negative Indian Ocean Dipole (NIOD). Anomalous latent heating in the tropical eastern Indian Ocean favored an extensive meridional Hadley circulation and a deep high-pressure belt, blocking southwest moisture transport. Thermodynamically, intense downward vertical motions produced severe descending adiabatic warming, which offset longwave radiational cooling and sustained anomalous heat accumulation throughout the deep troposphere. Conversely, the 2019 localized event occurred under a weak Central Pacific El Niño and a positive IOD. The anomalous tropical cooling weakened systematic subsidence and provided a favorable background for a Rossby wave train, featuring an offshore cyclone over the Western North Pacific that severed moisture pathways. Characterized by shallower vertical subsidence, the lack of a penetrative adiabatic heat source merely maintained a lower-level thermodynamic balance, confining extreme heat to the central–eastern YRB. Although superficially similar at the surface, these CHDEs are sustained by two distinct ocean–atmosphere interaction paradigms. Clarifying these dual paradigms provides a critical physical basis for improving sub-seasonal prediction. 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

Rice cultivation commonly employs the continuous flooding (CF) method, which depends heavily on water availability creating anaerobic conditions for methane (CH₄) emissions. Rainfed rice areas rely on precipitation for irrigation, making the system sensitive to climatic variability. This study examines associations between ENSO phases and satellite-observed atmospheric XCH₄ variability over Thailand using GOSAT as the primary long-term dataset from 2012 to 2022, with Sentinel-5P/TROPOMI used as a supporting dataset for recent spatial patterns. The analysis conducted covers three cropping seasons: (1) January–April, (2) May–August, and (3) September–December. The results indicate comparable average atmospheric methane concentrations of 1787.94 ± 11.50 XCH₄ (ppb) during El Niño, 1788.8 ± 11.22 XCH₄ (ppb) in neutral conditions, and 1793.45 ± 10.93 XCH₄ (ppb) during La Niña. The obtained data indicate a seasonal variability, with the highest satellite-observed XCH₄ values found during September–December, corresponding to the main growing period of wet-season rice. The results suggest that climate change amplifies these anomalies through altered precipitation patterns and water availability. Current rice cultivation practices warrant reconsideration, in particular the alternate wetting and drying (AWD) method, offering reduced CH₄ emissions while conserving water resources. This underscores the importance of water management strategies for sustainable rice production and resilience to climate variability. Full article

Olive (Olea europaea L.) orchards on the hyper-arid Peruvian coast (Tacna, ${18}^{\circ }$ S) suffered >70$\%$ yield collapses in the 2016 and 2024 El Niño seasons against a non-failure mean of $\sim 6$ t ha⁻¹ and a 2022 La Niña bumper harvest, raising the question of whether insufficient winter chilling is the binding climate constraint. We combined in situ daily meteorology (2015–2025) with yield records from eleven Sevillana–Ascolana parcels (88 parcel-years over eight seasons) and fitted a year-level log-OLS model with mean chill-window and fruit-growth temperatures, validated by year-block bootstrap, permutation, a closed-form Bayesian posterior, and a parcel-year mixed model. The model achieves $R_{log}^2=0.65$, and the chill slope ($\beta =-0.82$) is robust across three independent tests: one-sided permutation $p=0.036$; Bayesian posterior with 99.8% of mass below zero (Savage–Dickey BF₁₀ = 15.9); parcel-year mixed model $p<{10}^{-14}$. Counterfactual restoration of chill-window temperature to its non-failure climatology recovers the full collapse in both years, whereas restoring fruit-growth temperature recovers nothing. CMIP6 delta-method projections identify a chill-collapse threshold at $\Delta T_{\mathrm{winter}}\approx +{1.25 }^{\circ }$C; SSP1-2.6 alone reduces mid-century mean yield by $\sim 52\%$, and SSP5-8.5 reaches $-89\%$ by 2051–2070. Tacna emerges as a chill-sentinel system where winter warmth, not summer heat, is the binding constraint and the transition to the failure regime lies on a near-term adaptation horizon. Full article

Interannual climate variability exerts a strong control on the thermohaline structure of eastern boundary upwelling systems, particularly in transition zones where distinct water masses converge. Seasonal and interannual variability in temperature and salinity were examined in the southern California Current System for the period 2000–2015 using hydrographic observations and satellite altimetry, analyzed by season and ENSO phase. During El Niño, the upper 100 m exhibits positive temperature and salinity anomalies of 1–2 °C and ~0.1–0.2 g kg⁻¹ associated with 50–80 m isopycnal deepening, reduced upwelling-induced ventilation, the expansion of subtropical waters onto the shelf, and enhanced poleward geostrophic transport. In contrast, La Niña conditions shoal isopycnals, enhances upper-layer stratification, and sustains equatorward flow throughout the year. Temperature and salinity anomalies extend below 100 m, suggesting a remote reorganization of the baroclinic structure at the shelf–ocean boundary. Salt fingering is inferred to be the dominant non-conventional mixing process in the region, with peak occurrence in autumn. These results highlight that ENSO confines thermohaline reorganization to the inner continental shelf (~150 km), modulates coastal–ocean density gradients, weakens equatorward geostrophic transport during El Niño, and alters coastal–ocean heat and salt exchanges within the southern CCS transition zone. Full article

El Niño–Southern Oscillation (ENSO) has been identified as a key factor influencing grapevine phenology and harvest timing in South America. Nevertheless, few long-term analyses have explored its varietal impacts in hyper-arid viticultural regions. The goal was to evaluate the effect of ENSO phases on harvest dates and bioclimatic indices in different grapevine varieties cultivated in Northern Chile. The results revealed that Muscat of Alexandria showed little variation in harvest timing across ENSO phases. In contrast, harvest time in Thompson Seedless was delayed under La Niña events, being strongly correlated with the Maximum Spring Temperature Summation (SON_max) Index. Moscatel Rosada and Flame Seedless showed non-statistical significance and high variability on harvest dates. El Niño phases were consistently warmer than La Niña events that showed markedly greater interannual variability on harvest dates and bioclimatic index values. The strength of correlations was improved when the bioclimatic indices were recalculated over adjusted seasonal windows, underscoring the need for phenology-based rather than calendar-based approaches. These results provide new evidence of the heterogeneous responses of table and Pisco grapevine varieties to ENSO events in the hyper-arid regions of Northern Chile, underscoring the varietal differences in sensitivity to early-season climatic anomalies. Full article