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The impact of the Madden‐Julian oscillation (MJO) on the intraseasonal PNA (ISPNA) was investigated and was found to be modulated by the El Niño‐Southern Oscillation (ENSO), which reasonably explains the skewness of the ISPNA during El Niño and La Niña winters. It was shown that the intensity and periodicity of the ISPNA was much stronger and slightly longer in La Niña winters than in the El Niño winters. The phase‐locked association between the ISPNA and MJO indicate that this skewness was controlled by the MJO. The northward Rossby wave activities derived from the tropics associated with the MJO to the subtropical Pacific sector of the ISPNA clarified that the stronger intensity of the MJO convection in the western Pacific during the La Niña winters, as well as the slower eastward propagation of the MJO, led to the asymmetric intensity and period of the ISPNA in the two ENSO phases. Plain Language Summary: While prior studies have revealed that the El Niño‐Southern Oscillation (ENSO) can impact global climate, how ENSO affects the intraseasonal variability of the Pacific‐North American pattern (ISPNA) remains unclear. It was found that the ISPNA was skewed toward a higher intensity and a longer period in the La Niña winters than in the El Niño winters after removing the interfere of winter‐mean PNA. This is quite different from the conventional understanding that the PNA is often stronger during El Niño winters than during La Niña winters because of the asymmetric heating effort of the ENSO. The phase‐locked association between the ISPNA and the Madden‐Julian Oscillation (MJO) indicate that this skewness was controlled by the MJO. The northward Rossby wave activities derived from the tropics to the subtropical Pacific sector of the ISPNA clarified the cause‐and‐effect relationship between the ISPNA and the MJO. The stronger intensity of the MJO convection in the tropical Western Pacific to oceans east of Australia during the La Niña winters, as well as the slower eastward propagation of the MJO, led to the skewness of the stronger intensity and longer period of the ISPNA in the La Niña winters than in the El Niño winters. Key Points: The intraseasonal PNA (ISPNA) was skewed toward a higher intensity and a longer period in the La Niña winters than in the El Niño wintersThe Madden‐Julian Oscillation (MJO) and the ISPNA were found to have a stable phase‐locked relationshipThe differences in the intensity and propagation of the MJO between La Niña and El Niño winters dominantly led to the skewed ISPNA [ABSTRACT FROM AUTHOR]

As global warming intensifies, the coupling relationship between negative Indian Ocean Dipole (nIOD) and La Niña has substantially changed. However, the characteristics and mechanisms of these changes are not yet fully understood. Here, we find that the impact of La Niña on nIOD has considerably weakened since 1999, with the frequency of nIOD occurrences during La Niña years plummeting to a mere one‐third of the pre‐1999 levels. This is primarily attributed to the early onset of Indian summer monsoon and the decrease in La Niña intensity, while the effect of variations in Bjerknes feedback is relatively minor. Model simulations suggest that the influence of La Niña on nIOD will continue to weaken under future global warming through similar mechanisms as in the observations, increasing the complexity of air‐sea coupling in the Indian Ocean. Plain Language Summary: The negative Indian Ocean Dipole (nIOD) has significant impacts on both local and global climate change. La Niña is a major trigger for nIOD. However, as the globe warms up, the connection between nIOD and La Niña has changed a lot. This study analyze observation and reanalysis data from the 1950s onwards to see how nIOD and La Niña are linked. We find that La Niña has had less impact on nIOD since 1999. This is because the summer monsoon starts earlier, causing changes in wind patterns over the Indian Ocean. La Niña normally brings westerly wind anomalies in the Indian Ocean, but these winds are weakened because of the early monsoon. This makes it harder for nIOD to form. The feedback loop known as the Bjerknes feedback doesn't play a big role in maintaining nIOD. Furthermore, the reduction in La Niña intensity also contribute to weakening the relationship between La Niña and nIOD. Models predict that La Niña's impact on nIOD will continue to weaken under future global warming, increasing the complexity of air‐sea coupling in the Indian Ocean and leading to more challenges in forecasting. Key Points: The relationship between La Niña and negative Indian Ocean Dipole has weakened significantly in this centuryThe spring‐summer easterly anomaly induced by the premature summer monsoon weakens the La Niña‐induced westerly anomalyThe impact of La Niña on negative Indian Ocean Dipole will continue to weaken under future global warming [ABSTRACT FROM AUTHOR]

Coastal oceans, traditionally seen as a conduit for transporting atmospheric carbon dioxide (CO2)-derived anthropogenic carbon (CANT) to open oceans, exhibit complex carbon exchanges at their interface. South China Sea (SCS) exemplifies this complexity, where interactions with the Pacific, particularly through Kuroshio intrusion, challenge the understanding of CANT source and variability in a coastal ocean. Contrary to prevailing paradigm expectations, our high-resolution, long-term data reveal that CANT in the SCS primarily originates from Pacific water injection across the Luzon Strait rather than atmospheric CO2 invasion. Over the past two decades, the SCS has experienced increasing CANT levels, with notable interannual fluctuations driven by El Niño and La Niña events influencing Kuroshio intrusion, generating anomalously high and low CANT inventories, respectively. This highlights an overlooked CANT transport pathway from open to coastal oceans, responsible for cumulative ocean acidification that has already affected coral reefs enriched in the SCS located west of the Coral Triangle. [ABSTRACT FROM AUTHOR]

While deep learning models have shown promising capabilities in ENSO prediction, their inherent black-box nature often leads to a lack of physical consistency and interpretability. Here, we introduce ENSO-PhyNet, a Transformer-based model for ENSO prediction, which incorporates heat budget dynamical processes through self-attention computations. The model predicts sea surface temperature (SST) in the equatorial Pacific and achieves skillful predictions of the Niño 3.4 index with a lead time of up to 22 months. The self-attention maps reveal how the model makes predictions by focusing on specific processes in certain regions. Case analyses of recent El Niño and La Niña events underscore the impact of thermocline feedback and zonal advection feedback on the warming of the 2015 event, as well as the crucial role of anomalous easterlies in the emergence of the second-year La Niña in 2021. These findings demonstrate the model's interpretability and its ability to identify signals that are physically consistent with the development of ENSO events. [ABSTRACT FROM AUTHOR]

The study delves into the complexities of prolonged El Niño (PE) and La Niña (PL) events, examining their behaviour, dynamics, and representation in climate models participating in CMIP6. These events deviate from the typical cycles of the El Niño-Southern Oscillation (ENSO) system and significantly impact global weather patterns and socioeconomic systems. The study aims to enhance our understanding of these multi-year ENSO events through a comparative analysis of observational data and model simulations. Observational data reveal the distinct characteristics of PE and PL events, with prolonged warming or cooling anomalies persisting in the equatorial Pacific beyond the usual timeframe associated with canonical El Niño (CE) and La Niña (CL) events. However, while climate models generally capture the general trend of sustained warming or cooling, discrepancies exist in the magnitude and timing of SST anomalies, particularly during peak phases. The analysis highlights limitations in the ability of current climate models to simulate consecutive El Niño events following PE events and strong El Niño events preceding PL events accurately. Furthermore, discrepancies in the representation of subsurface oceanic dynamics and zonal wind stress patterns underscore challenges in capturing the intricate interactions driving ENSO variability. The study emphasizes the importance of refining climate models to capture better the intricacies of prolonged ENSO events, which have significant implications for future climate projections and adaptation strategies. [ABSTRACT FROM AUTHOR]

This study analyzes the atmospheric and oceanic mechanisms that influenced rainfall distribution in Ceará, Brazil during the 2018 rainy season and the impacts of the observed rainfall distribution on agriculture in the region. Special attention is given to the month of March, when precipitation was below the climatological average. Precipitation, wind, omega, specific humidity, outgoing longwave radiation, and oceanic indices from the Pacific and Atlantic data were used in the analyses. The Multivariate Real-Time Madden–Julian Oscillation (MJO) Index was employed to assess the influence of the MJO on precipitation in March 2018. The results indicate that subseasonal variability, through the MJO in phases 4, 5, and 6, played a crucial role in suppressing convective activity. Additionally, a delayed austral summer pattern was found, with the South American Convergence Zone (SACZ) positioned further north and a quasi-stationary trough at altitude. These two atmospheric factors inhibited the more intense rainfall activity in the Intertropical Convergence Zone (ITCZ). In the ocean analyses, Sea Surface Temperature (SST) anomalies indicated the presence of La Niña in the equatorial Pacific, although it was in transition from cooling to warming. This, in addition to the neutrality of the interhemispheric gradient of the Tropical Atlantic SST anomalies, may have also contributed to negative precipitation anomalies and influenced the MJO displacement. MJO phases associated with suppression contributed to economic losses for the agricultural sector. [ABSTRACT FROM AUTHOR]

El Niño-Southern Oscillation (ENSO) tropical cyclones (TCs) are important moisture sources in semiarid, mountainous Northwestern Mexico. Studies conducted in this region have not expressed differences between coastal and mountainous regions under different ENSO scenarios, instead, changes have been explored in the entire region as a whole. Attempting to fill this gap, the present study conducted an analysis of observed changes in rainfall contribution of landfalling tropical cyclones under five scenarios: (1) El Niño, (2) La Niña, (3) El Niño to La Niña, (4) La Niña to El Niño, and (5) Neutral on mountainous, foothill and coastal regions. In addition, the changes observed were explored under five scenarios in monthly precipitation peak and seasonal cumulative precipitation, which are important characteristics during the North American Monsoon (NAM). The results indicate that most changes occur in the coastal region during La Niña, El Niño to La Niña and Neutral scenarios, where more than half of the stations recorded average precipitation above their regional climatology. Thus, six TCs made landfall with an average of 73% of stations that recorded accumulations above their regional climatology (i.e. NAM precipitation) mainly affecting the southern foothill region. Although the observed changes do not show a well-defined seasonal pattern distinguishing the three regions, changes may be identified and explained by the latitudinal gradient, relief and soil moisture characteristics strongly influenced by local factors. Unfortunately, these results make it difficult to forecast the precipitation response under the different scenarios. [ABSTRACT FROM AUTHOR]

Arctic sea ice has undergone a significant decline in the Barents–Kara Sea (BKS) since the late 1990s. Previous studies have shown that the decrease in sea ice caused by increased poleward moisture transport is modulated by tropical sea temperature changes (mainly referring to La Niña events). The occurrence of multi-year La Niña (MYLA) events has increased significantly in recent decades, and their impact on Arctic sea ice needs to be further explored. In this study, we investigate the relationship between sea-ice variation and different atmospheric diagnostics during MYLA and other La Niña (OTLA) years. The decline in BKS sea ice during MYLA winters is significantly stronger than that during OTLA years. This is because MYLA events tend to be accompanied by a warm Arctic–cold continent pattern with a barotropic high pressure blocked over the Urals region. Consequently, more frequent northward atmospheric rivers intrude into the BKS, intensifying longwave radiation downward to the underlying surface and melting the BKS sea ice. However, in the early winter of OTLA years, a negative North Atlantic Oscillation presents in the high latitudes of the Northern Hemisphere, which obstructs the atmospheric rivers to the south of Iceland. We infer that such a different response of BKS sea-ice decline to different La Niña events is related to stratospheric processes. Considering the rapid climate changes in the past, more frequent MYLA events may account for the substantial Arctic sea-ice loss in recent decades. [ABSTRACT FROM AUTHOR]

Winter precipitation over eastern China displays remarkable interannual variability, which has been suggested to be closely related to El Niño–Southern Oscillation (ENSO). This study finds that ENSO impacts on eastern China precipitation patterns exhibit obvious differences in early (November–December) and late (January–February) winter. In early winter, precipitation anomalies associated with ENSO are characterized by a monopole spatial distribution over eastern China. In contrast, the precipitation anomaly pattern in late winter remarkably changes, manifesting as a dipole spatial distribution. The noteworthy change in precipitation responses from early to late winter can be largely attributed to the seasonally varying Kuroshio anticyclonic anomalies. During the early winter of El Niño years, anticyclonic circulation anomalies appear both over the Philippine Sea and Kuroshio region, enhancing water vapor transport to the entirety of eastern China, thus contributing to more precipitation there. During the late winter of El Niño years, the anticyclone over the Philippine Sea is further strengthened, while the one over the Kuroshio dissipates, which could result in differing water vapor transport between northern and southern parts of eastern China and thus a dipole precipitation distribution. Roughly the opposite anomalies of circulation and precipitation are displayed during La Niña winters. Further analysis suggests that the seasonally-varying Kuroshio anticyclonic anomalies are possibly related to the enhancement of ENSO-related tropical central-eastern Pacific convection from early to late winter. These results have important implications for the seasonal-to-interannual predictability of winter precipitation over eastern China. [ABSTRACT FROM AUTHOR]

The East African Coastal Current (EACC) is an important western boundary current of the tropical south Indian Ocean and plays an important role in the ocean circulation and biogeochemical cycles in the Indian Ocean. This study investigates the interannual variability of the EACC and its dynamical mechanisms. The result shows that the EACC has interannual variability associated with El Niño–Southern Oscillation (ENSO) during 1993–2017. The EACC shows a significantly positive correlation with the Niño-3.4 index with a correlation coefficient of 0.65, lagging the Niño-3.4 index by 18 months. During the decaying phases of El Niño (La Niña) events, the negative (positive) sea level anomaly (SLA) propagates westward as upwelling (downwelling) Rossby waves from the southeast Indian Ocean to the southwest Indian Ocean and then strengthens (weakens) the EACC due to zonal SLA gradient off the East African coast under geostrophic equilibrium. The SLA gradually weakens in the southeast Indian Ocean during its westward propagation but strengthens in the southwest Indian Ocean promoted by local wind stress curl anomaly. This study can improve our understanding of the relationship between the western boundary current of the tropical south Indian Ocean and large-scale ENSO air–sea processes and is important for managing marine fisheries and ecosystems on the East African coast. [ABSTRACT FROM AUTHOR]

Despite common background La Niña conditions, Australia was very dry in November 2020 and wet in November 2021. This paper aims to provide an explanation for this difference. Large-scale drivers of Australian rainfall, including El Niño–Southern Oscillation, Indian Ocean dipole, Southern Annular Mode, and Madden–Julian oscillation, were examined but did not provide obvious clues for the differences. We found that the absence (in 2020) or presence (in 2021) of an enhanced thermal wind and subtropical jet over the Australian continent contributed to the rainfall anomalies. In general, La Niña sets up warm sea surface temperatures around northern Australia, which enhances the meridional temperature gradient over the continent and hence thermal wind and subtropical jet. In November 2021, these warm sea surface temperatures, coupled with a persistent midlatitude trough, which advected cold air over the Australian continent, led to an enhanced meridional temperature gradient and subtropical jet over Australia. The enhanced jet provided favorable conditions for the development of rain-bearing weather systems across Australia. In 2020, the continent was warm, displacing the latitude of maximum meridional temperature gradient south of the continent, resulting in fewer instances of the subtropical jet over Australia, and little development of weather systems over the continent. We highlight that although La Niña tilts the odds to wetter conditions for Australia, in any given month, variability in temperatures over the continent can contribute to subtropical jet variability and resulting rainfall in ways which confound the normal expectation from La Niña. Significance Statement: Forecasts of El Niño–Southern Oscillation are eagerly awaited, as the state of this climate driver has profound impacts on the likelihood of rainfall in regions around the world. While El Niño and La Niña do change rainfall likelihoods, the actual outcomes of these events are sometimes counter to expectation. This work explores one of the confounding factors to those expectations in the Australian context—the role of the meridional temperature gradient over the continent in modifying the storm track over Australia, which can disrupt the expected El Niño and La Niña teleconnections. We present case studies for two La Niña springs, highlighting that the Australian continent can help shape its own weather toward wetter or drier outcomes. [ABSTRACT FROM AUTHOR]

Context: Climate change reportedly affects global fisheries, including the highly valuable swimming crabs, an important benthic species in Asian waters. Aims: The aim of this study was to determine the effects of El Niño–Southern Oscillation (ENSO) events on catch rates and habitat suitability of Portunus pelagicus , Portunus sanguinolentus and Charybdis feriatus in the Taiwan Strait. Methods: We combined marine remote sensing data with Taiwanese trap vessel data to develop a weighted habitat suitability index modelling and analyse the recruitment dynamics of swimming crabs in different ENSO events. Key results: Our results suggest that Increasing salinity (>33.5 PSU) and sea temperature (>18.6°C) during La Niña events had a positive effect on stock recruitment and habitat suitability index of P. pelagicus and C. feriatus. By contrast, P. sanguinolentus were not affected by ENSO events. The low catch rates for P. sanguinolentus in normal years and for C. feriatus and P. pelagicus in normal and El Niño years were highly consistent with the significant shrinkage of the habitat suitability index. Conclusions: Monitoring climate change and environmental factors is essential for understanding their effects on marine ecosystems. Implications: This research can help implement sustainable crab fisheries. Climate change affects marine environments, disrupting fisheries and ecosystems. Marine crustaceans, like swimming crabs in the Taiwan Strait, respond by altering catchability and habitat suitability. El Niño events significantly affect their fishing grounds, whereas water exchange and wind changes influence temperature, salinity and water mass structure. During La Niña years, positive ocean temperature and salinity anomalies may further affect the optimal habitats and catchability of swimming crabs. [ABSTRACT FROM AUTHOR]

Long-lasting La Niña events (including double-year and triple-year La Niña events) have become more frequent in recent years. How the multi-year La Niña events affect tropical cyclone (TC) activities in the western North Pacific (WNP) and whether they differ from single-year La Niña events are unknown. Here we show that TCs are more active over the far-WNP (FWNP, 110°–150°E), leading to marked high risks at China coasts during the second decaying summer of double-year La Niña events. The anomalous TC activities are directly related to the enhanced cyclonic anomaly over the FWNP, possibly a result of large-scale remote forcing initiated by the tropical North Atlantic (TNA) cooling. The persistent TNA cooling from the decaying winter to summer of double-year La Niña events drives westerlies over the Indo-western Pacific through Kelvin waves, which induce the cooling over the north Indian Ocean via the wind-evaporation-sea surface temperature effect, favoring the asymmetric heat distribution pattern and stimulating an anomalous vertical circulation over the eastern Indian Ocean to FWNP. The cooling over the north Indian Ocean also excites Gill responses, magnifying the TNA-induced westerlies and boosting the anomalous vertical circulation, and thus gives rise to the strong cyclonic circulation anomaly over the FWNP in summer. We suggest that the key point of the process is the strong TNA cooling related to the persistent negative Pacific-North American pattern (PNA) and positive North Atlantic Oscillation (NAO) while double-year La Niña events decay, distinct from the rapid decline of PNA and NAO during single-year La Niña events. The work provides a unique perspective on understanding TC activities over the WNP related to the El Niño-Southern Oscillation. [ABSTRACT FROM AUTHOR]

This study analyses the spatio‐temporal variability of heatwave characteristics and their association with large‐scale climate drivers across seven climatic sub‐regions in Vietnam, including the Northwest (R1), Northeast (R2), Red River Delta (R3), North Central (R4), South Central (R5), Central Highlands (R6) and the South (R7). The analysis is based on observed daily maximum temperatures from 102 meteorological stations, spanning the period 1980–2020. The obtained results reveal diverse heatwave patterns across the country. Amongst the seven climatic sub‐regions of Vietnam, the R3 and R4 sub‐regions experienced more frequent heatwaves and a higher number of heatwave days, but shorter durations. In contrast, other sub‐regions had fewer heatwave events and heatwave days but experienced longer‐lasting heatwaves. The intensity of heatwave events varies amongst sub‐regions, with the highest value in the R4 sub‐region, and the lowest in R7. Notably, the R1–R5 sub‐regions are affected by heatwaves over larger areas, compared to others. Additionally, the findings confirm that the lagged influence of El Niño–Southern Oscillation (ENSO) is the primary climatic driver of heatwave characteristics in Vietnam. Generally, heatwaves tend to occur more frequently in the years following El Niño events than after La Niña events. This observation provides opportunities for developing a system of seasonal predictions of heatwaves in Vietnam. The impact of ENSO on the number of heatwave events and heatwave days is evident in five out of seven sub‐regions, with less impact in the R2 and R7 sub‐regions. However, it does not significantly affect heatwave intensity. [ABSTRACT FROM AUTHOR]

Monsoon precipitation variability over the Indo‐China Peninsula (ICP) has become more complicated affected by global warming. In this study, the modulation of Pacific decadal oscillation (PDO) on the relationship between El Niño–Southern Oscillation (ENSO) and the rainy season onset over the ICP were investigated. The results showed that the ICP rainy season onset were predominantly correlated with winter sea surface temperature anomalies (SSTAs) in the East Pacific Ocean, with late and early onsets following El Niño and La Niña events, respectively. During the warm and cold PDO phase, the correlations tended to be substantially strengthened and weakened, respectively. Further analysis indicates that PDO significantly influenced the effects of ENSO on the ICP rainy season onset by modulating SSTAs and low‐level wind fields. During the El Niño events, abnormal easterlies over the Bay of Bengal (BoB) and southern ICP suppressed water vapour transporting to the ICP, which may be related to the zonal SST anomaly gradient between the Indian Ocean and the Northwest Pacific Ocean. When the El Niño occurred during the warm PDO phase, the rainy season onsets were later. The anomalous easterlies became stronger corresponds to the increasing zonal sea surface temperature anomaly (SSTA) gradient between the Indian Ocean and the Northwest Pacific Ocean. There was no significant anomaly on the rainy season onset during the cold PDO phase. During the La Niña events, the abnormal westerlies in BOB accelerated water vapour transport, and the rainy season onset were earlier during the warm and cold PDO phase. The modulating effects of PDO on La Niña were less than those on El Niño. These results suggest that the predictability of rainy season onset over the ICP can be improved through PDO and thus help agricultural planning and water resources management. [ABSTRACT FROM AUTHOR]

In July and August 2022, the Yangtze River basin (YRB) experienced its hottest summer since 1961. The SINTEX‐F2 seasonal prediction system initialized in early May predicted the hotter‐than‐normal summer due to its successful prediction of central Pacific La Niña, negative Indian Ocean Dipole and the resultant warming in the tropical West Pacific‐East Indian Ocean (TWP_EIO). The common SST forcing explains only about 26% to the heatwave strength, while the internal variations in the anomalous warming in the TWP_EIO and Europe, surplus precipitation in Pakistan, and local land‐air interaction account for approximately 65%, based on the analysis of 108 ensemble members. These factors have collectively increased the maximum temperature over the YRB through the enhancement and westward expansion of western North Pacific subtropical high. Our findings quantify the relative contributions of external forcing and internal variations to the unprecedented hot event, offering insights into its forming mechanism and potential predictability. Plain Language Summary: A record‐breaking heatwave event occurred in the YRB in July and August 2022, posing significant risks on human health, power supply, and social economic activities. Recognizing the importance of such an event, our study aims to identify key factors influencing its prediction using the SINTEX‐F2 system. The central Pacific La Niña, negative Indian Ocean Dipole and the resultant warming in the TWP_EIO provide the dominant predictability, but accounts only about 26% of the heatwave strength. However, internal variations in the anomalous warming in the TWP_EIO and Europe, surplus precipitation in Pakistan, and local land‐air interaction collectively explain about 65%. Our results suggest the necessity of large‐ensemble prediction in capturing this kind of unprecedented extreme event. Key Points: The SINTEX‐F2 initialized on 2022 early May captures the warmer‐than‐normal air temperatures in Yangtze River basinThe model successfully predicts co‐occurrences of CP La Niña and negative IOD in 2022However, the direct SST forcing contributes only 26% to the 2022 extreme event in Yangtze River basin [ABSTRACT FROM AUTHOR]

In this study, we investigated the triple‐dip La Niña during 2020–2022 by comparing it with the previous (1973–1975 and 1998–2000) La Niña events. We found that the cold sea surface temperature (SST) in the eastern equatorial Pacific was moderate during the study period; however, the accompanying near‐surface easterly wind anomaly was unusually stronger during its lifecycle than during the previous two events. The maintenance of 2020–2022 La Niña appeared to be attributable to the strong zonal SST gradient. The strong zonal SST gradient resulted from the La‐Niña‐associated interannual SST anomaly, which was further enhanced by a warming trend in the western equatorial Pacific (165°E−160°W, 5°S–5°N) and the interdecadal oscillation of the Pacific‐Decadal‐Oscillation‐associated cold SST in the eastern tropical Pacific. The warming trend in the western equatorial Pacific, with a faster warming speed than global warming, also modified the La‐Niña‐associated Pacific–North American teleconnection to shifted eastward. Plain Language Summary: The La Niña during 2020–2022 was the first triple‐dip event in the 21st century. It induced several major disasters worldwide, such as the record flooding in Pakistan caused 30 million people to lose their homes and took the lives of more than 1,000 individuals. However, how this long‐duration La Niña was maintained remained unclear. The physical processes related to the 2020–2022 La Niña were investigated by comparing them with those of the previous 3‐year La Niña events (1973–1975 and 1998–2000). The major distinctive feature of the 2020–2022 La Niña was the moderate negative sea surface temperature (SST) anomaly in the eastern equatorial Pacific, which was accompanied by an unusually strong near‐surface easterly wind anomaly in the central equatorial Pacific. Our study revealed the maintenance of the triple‐dip La Niña during 2020–2022 was attributable to the strong zonal SST gradient between the western and eastern equatorial Pacific, with the western waters being dominated by a warming trend and the eastern waters being influenced by the cold phase of the Pacific Decadal Oscillation. The warming trend in the western equatorial Pacific provided a favorable background for a triple‐dip La Niña event and also modified the La‐Niña‐associated Pacific–North American teleconnection so that it shifted eastward. Key Points: The La‐Niña‐associated cold SST was moderate during 2020–2022, but the accompanying easterly wind anomaly reached an unusual highThe strong easterly was in response to the zonal SST gradient between the warm western tropical Pacific and cold eastern tropical PacificThe western equatorial Pacific SST, with a faster warming speed than global warming, modulated the PNA teleconnection to shift eastward [ABSTRACT FROM AUTHOR]

Zonal extensions of the Western Pacific subtropical high (WPSH) strongly modulate extreme rainfall activity and tropical cyclone (TC) landfall over the Western North Pacific (WNP) region. These zonal extensions are primarily forced on seasonal timescales by inter‐basin zonal sea surface temperature (SST) gradients. However, despite the presence of large‐scale zonal SST gradients, the WPSH response to SSTs varies from year to year. In this study, we force the atmosphere‐only NCAR Community Earth System Model version 2 simulations with two real‐world SST patterns, both featuring the large‐scale zonal SST gradient characteristic of decaying El Niño‐developing La Niña summers. For each of these patterns, we performed four experimental sets that tested the relative contributions of the tropical Indian Ocean, Pacific, and Atlantic basin SSTs to simulated westward extensions over the WNP during June–August. Our results indicate that the subtle differences between the two SST anomaly patterns belie two different mechanisms forcing the WPSH's westward extensions. In one SST anomaly pattern, extratropical North Pacific SST forcing suppresses the tropical Pacific zonal SST gradient forcing, resulting in tropical Atlantic and Indian Ocean SSTs being the dominant driver. The second SST anomaly pattern drives a similar westward extension as the first pattern, but the underlying SST gradient driving the WPSH points to intra‐basin forcing mechanisms originating in the Pacific. The results of this study have implications for understanding and predicting the impact of the WPSH's zonal variability on tropical cyclones and extreme rainfall over the WNP. Plain Language Summary: Westward extensions of the Western North Pacific subtropical high (WPSH) drive rainfall extremes over the Western North Pacific basin, and is important for the prediction of summer rainfall, including monsoonal rainfall and tropical cyclone activity. Studies have previously highlighted the importance of tropical large‐scale zonal sea surface temperature (SST) gradient—warm tropical Indian Ocean in conjunction with cold equatorial eastern Pacific Ocean—in developing and maintaining the summer WPSH and westward extensions. Here, we further show that even with very similar SST patterns, the large‐scale zonal SST pattern may belie forcing from inter‐basin SSTs versus intra‐basin SSTs. We find that the net influence from the Pacific basin determines whether inter‐basin remote SST gradients versus intra‐basin Pacific SST gradients are the predominant driver of westward extensions. Key Points: Two similar SST patterns belie two different mechanisms forcing the subtropical high's westward extensionsTropical Pacific SST gradient forcing of westward extensions can be suppressed by its extratropical SST forcingRemote Atlantic SST forcing drives westward extensions when the local net Pacific forcing is weak [ABSTRACT FROM AUTHOR]

Frequent drought has posed widespread, large-scale and extremely severe impact on the ecological environment under global climate and human activities. This study aims to analyze the spatiotemporal dynamic evolution of drought in China. A threshold of -0.5 was chosen to identify drought conditions. A raster was set as the drought state at standardized precipitation evapotranspiration index (SPEI) less than -0.5. The start and end times of drought were varied for each raster within a single event, indicating the dynamic and evolving drought. At the same time, some rasters exited the drought states, while others entering. The contribution rates of drought to rasters were calculated at a given time, in order to capture the dynamic changes in drought. Three perspectives were considered: the extent of drought impact, duration, and severity. The SPEI was then used to assess the drought, in order to introduce the concept of persistent drought rasters. Large-scale and persistent drought events were identified to investigate the spatiotemporal dynamic evolution from 1961 to 2020, together with their response mechanisms to the atmospheric circulation. The research findings can be summarized as follows: 1) A total of 47 events occurred between 1961 and 2020. The 1970s witnessed the highest frequency of large-scale persistent drought events, with 10 occurrences, while the 2000s and 2010s each experienced 9 such events. The average duration of these drought events was 7.14 months, with the longest average duration in the 1960s at 11.83 months. The average extent was 28.66%, with the highest average extent index reaching 33.75% in the 2000s.The average severity was -2.86 for the 47 large-scale persistent drought events. Between 1980 and 2010, the average area affected by persistent drought events each decade showed a continuous expanding trend. Between 1970 and 2020, the average duration of persistent drought events each decade was concentrated between 4 to 8 months. 2) Before the 1990s, the lag time of Oceanic Niño Index's impact on spring precipitation was 3 and 9 months. From then on, the ONI's influence on summer and autumn precipitation extended to 6, 9, and 12 months. Once La Niña events occurred, there was the decrease in the spring precipitation, thereby increasing the frequency of spring droughts in China. 3) There was a resonance period of 16-48 months between ONI and SPEI3 during the years 1961-1976, 1980-1988, 1994-2001, and 2006-2020. The ONI index also demonstrated the strongest correlation with SPEI3 in this timeframe. While the WP index exhibited the weakest correlation with SPEI3 during the same periods.The research results help further understand the causes and patterns of drought in China, thereby enhancing the scientific basis and precision of drought prevention and mitigation policies. [ABSTRACT FROM AUTHOR]

This study examines the asymmetry in the Indian summer monsoon rainfall (ISMR) response over India and its four homogeneous regions to two distinct types of temporal evolution in La Niña. We have shown this uneven response by analysing the large‐scale dynamics over tropical Indo‐Pacific region for the period 1951–2022. We have identified two types of La Niña events during monsoon season (June–September) based on whether they evolved from El Niño or La Niña from preceding boreal winter season (December–February). India receives significantly more (less) rainfall during La Niña years, when it was preceded by El Niño (La Niña) in the preceding winter. We further observed the spatial diversity of rainfall over India with a northeast–southwest dipole pattern. When La Niña years were preceded by El Niño, positive surface pressure anomaly over west‐north Pacific, low‐level westerlies and moisture transport favoured the rainfall over south peninsula and west‐central India. Whereas moisture divergence associated with anomalous lower‐tropospheric anticyclone over west‐north Pacific suppressed the rainfall over Indo‐Gangetic plains. However, when La Niña years were preceded by La Niña in winter, the absence of westerlies and weak moisture transport subdued the rainfall over south peninsula and west‐central India. At the same time, moisture convergence and a greater number of monsoon depressions favoured rainfall over north‐west India. This study also looked at how well eight Copernicus Climate Change Service (C3S) models predicted ISMR and SST for two types of La Niña with April initial conditions during the period 1993–2016. Models were able to capture the spatial pattern of SST anomalies over Indo‐Pacific Ocean, but all models could not capture the spatial pattern of ISMR. However, in terms of intensity, six out of eight models could predict more (less) ISMR when it was preceded by El Niño (La Niña), coinciding with the observed anomaly. [ABSTRACT FROM AUTHOR]

Knowledge of spring warm pool in the Bay of Bengal (BoBWP) is key for further understanding the climate variability in this region and beyond, but little is known about the BoBWP climatological state and the related mechanisms. In this study, we investigate the spatial structure and evolution of the BoBWP using daily Optimum Interpolation SST data from 1982-2022 in combination with multi-source data. Our analysis shows that the BoBWP is located in the central bay (6°-13°N) with a thickness around 20m~ 40 m. Composite analysis indicates that the BoBWP emerges in early April, peaks in early May and dissipates in early June. During the developing period, the net heat flux dominates the formation of spring warm pool through significant air-sea coupling processes, and induces the warming rate of 0.27°C/10d in the mixed layer, which is far larger than the contribution of oceanic dynamical processes (0.01°C/10d). During the decaying period, the net heat flux also plays a dominant role, with a cooling rate of -0.21°C/10d, meanwhile ocean dynamical processes contribute to the cooling of the warm pool with a rate of -0.01°C/10d. Additionally, the SST and the area of the BoBWP are significantly correlated with ENSO (r=0.66 and 0.73, p=0.05). During El Niño decaying year, the BoBWP primarily expands in a southward direction, with a 75% increase in area. Conversely, during La Niña decaying year, the BoBWP almost disappears, with a 52% decrease. [ABSTRACT FROM AUTHOR]

Tropical and extra-tropical storms generate extreme waves, impacting both nearby and remote regions through swell propagation. Despite their devastating effects in tropical areas, the contribution of tropical cyclones (TCs) to global wave-induced coastal risk remains unknown. Here, we enable a quantitative assessment of TC's role in extreme waves approaching global coastlines, by designing twin oceanic wave simulations with and without realistic TC wind forcing. We find that TCs substantially contribute to extreme breaking heights in tropical regions (35-50% on average), reaching 100% in high-density TC areas like the North Pacific. TCs also impact remote TC-free regions, such as the equatorial Pacific experiencing in average 30% of its extreme wave events due to TCs. Interannual variability amplifies TC-induced wave hazards, notably during El Niño in the Central Pacific, and La Niña in the South China Sea, Caribbean Arc, and South Indian Ocean coastlines. This research offers critical insights for global risk management and preparedness. This paper shows that tropical cyclones contribute between 40% and 100% of the extreme wave events approaching coastlines in basins prone to tropical cyclone activity, while they can also impact remote areas via swell propagation across the ocean. [ABSTRACT FROM AUTHOR]

Monitoring areas susceptible to desertification contributes to the strategic development of regions located in environments of extreme hydric and social vulnerability. Therefore, the objective of this study is to evaluate the process of soil degradation in the Desertification Nucleus of Cabrobó (DNC) over the past three decades using remote sensing techniques. This study used primary climatic data from TerraClimate, geospatial data of land use and land cover (LULC), and vegetation indices (SAVI and LAI) via Google Earth Engine (GEE) from Landsat 5/TM and 8/OLI satellites, and established the aridity index (AI) from 1992 to 2022. The results indicated 10 predominant LULC classes with native vegetation suppression, particularly in agriculture and urbanization. SAVI ranged from −0.84 to 0.90, with high values influenced by La Niña episodes and increased rainfall; conversely, El Niño episodes worsened the rainfall regime in the DNC region. Based on the Standardized Precipitation Index (SPI), it was possible to correlate normal and severe drought events in the DNC with years under the influence of El Niño and La Niña phases. In summary, the AI images indicated that the DNC remained semi-arid and that the transition to an arid region is a cyclical and low-frequency phenomenon, occurring in specific periods and directly influenced by El Niño and La Niña phenomena. The Mann–Kendall analysis showed no increasing trend in AI, with a Tau of −0.01 and a p-value of 0.97. During the analyzed period, there was an increase in Non-Vegetated Areas, which showed a growing trend with a Tau of 0.42 in the Mann–Kendall analysis, representing exposed soil areas. Annual meteorological conditions remained within the climatic pattern of the region, with annual averages of precipitation and actual evapotranspiration (ETa) close to 450 mm and an average temperature of 24 °C, showing changes only during El Niño and La Niña events, and did not show significant increasing or decreasing trends in the Mann–Kendall analysis. [ABSTRACT FROM AUTHOR]

By exploring the multifaceted physical mechanisms underlying hot extreme events, the way for informed strategies to mitigate their impacts and enhance the nation's resilience in the wake of a changing climate can be paved. The long-term spatio-temporal variability of hot extremes analysis found an increasing trend (0.001 °C) of DMXT over whole Indian region except the eastern parts (Indo-Gangetic plains). The hot day is noted when DMXT > 40 °C, DMXT > 37 °C, DMXT > 35 °C and also DMXT is above the 90th percentile at each grid point in the plains, hilly, coastal region of India. The temperature tendency equation has been computed to identify the role of various physical processes driving the local extreme temperature changes in India. The analysis showed that the surface adiabatic warming found to be one of the prominent drivers of hot extreme events over India. The impact of El Niño-Southern Oscillation (ENSO) phases on the frequency of hot extreme days at local scale in India are quantified. The linear trend of hot days has been found increasing at a rate of 0.14/year, 0.08/year and 0.06/year in El Niño, La Niña and neutral years respectively. Similarly, the DMXT anomaly found to be 0.4 °C higher in El Niño phase as compared to La Niña phase. The results infers that the chances of hot days occurrence are increased (decreased) by 38% (16% and 8%) in El Niño (La Niña and neutral) period. The advection of hot air by westerlies into the Indian region leads to an increase in temperature. The composite elevated (dropped) geopotential height at 500 hPa showed the presence of high (low) pressure systems which leads to hot days occurrence over western, southern and central (northern, north western) India, where winds are westerlies (easterlies) in El Niño (La Niña) phase of ENSO. This reversal of wind is linked with the movement of warm sea surface temperature from western to eastern Pacific Ocean. Comprehending the dynamics of hot extremes in the India is vital for the development of strategies to mitigate the adverse impacts on various sectors, including agriculture, health, water resources, and infrastructure. [ABSTRACT FROM AUTHOR]

To measure the long-range transport of PCDD/Fs, a background sampling site at Mt. Lulin station (Taiwan) was selected based on meteorological information and its location relative to burning events in Southeast Asia. During regular sampling periods, a higher concentration of PCDD/Fs was recorded in 2008 at Mt. Lulin station during La Niña events, with levels reaching 390 fg I-TEQ/m3. In contrast, a higher concentration of 483 fg I-TEQ/m3 was observed in 2013 during biomass burning events. This indicates that La Niña affects the ambient PCDD/F concentrations. The ratio of ΣPCDD/ΣPCDF was 0.59, suggesting significant long-range transport contributions from 2007 to 2023. From 2007 to 2015, the predominant species was 2,3,4,7,8-PCDF, accounting for 25.3 to 39.6% of the total PCDD/Fs. From 2018 onward, 1,2,3,7,8-PCDD became more dominant, accounting for 15.0 to 27.1%. According to the results from the receptor model PMF (n = 150), the sources of PCDD/Fs were identified as dust storms and monsoon events (19.3%), anthropogenic activity (28.5%), and biomass burning events (52.2%). The PSCF values higher than 0.7 highlighted potential PCDD/F emission source regions for Mt. Lulin during biomass burning events, indicating high PSCF values in southern Thailand, Cambodia, and southern Vietnam. [ABSTRACT FROM AUTHOR]

El Niño–Southern Oscillation (ENSO) usually peaks in the boreal winter—November to January of the following year. This particular feature of ENSO is known as the seasonal phase locking of ENSO. In this study, based on 34 climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), the seasonal phase-locking characteristics of the model-simulated El Niño and La Niña events are evaluated in terms of the evolution of the SST anomalies associated with ENSO and the probability distribution of the peak month—the time at which ENSO peaks. It is found that CMIP6 models underestimate the phase-locking strength of ENSO for both El Niño and La Niña events. The ensemble mean peak month matches the observations, but the inter-model spread is large. The models simulate the phase locking of El Nino events better than that of La Niña events, and the large simulation bias of CMIP6 for La Niña phase-locking in the models may have an impact on the simulation of seasonal phase-locking in the ENSO. [ABSTRACT FROM AUTHOR]

The 2022 Yangtze mega-flash drought is characterized by strong intensity and rapid development both in time and space, accompanied by a persistent anticyclonic circulation anomaly. However, the causes of the extreme event remain elusive given the multiscale nature of drought. Here we presented a brief overview for the oceanic and terrestrial causes of the mega-flash drought during the summer of 2022, and estimated the risk in a changing climate. Using the soil moisture percentile as the drought index, it was found that the drought expanded to the entire Yangtze River basin within two months, with 80% of basin under severe drought conditions at the end of August. Both the intensity and onset speed of the 2022 mega-flash drought were ranked as the first during the past 62 years, with return periods of 86 and 259 years, respectively. The results of composite analysis showed that the spring La Niña can facilitate the abrupt change from a wet/normal condition in May–June to drought in July–August over the Yangtze River basin, which was beneficial for the increase of flash drought intensity and onset speed in 2022. The analysis through the linear regression also indicated that the unprecedented intensity was associated with the negative phase of the Pacific Decadal Oscillation. Quantified by a coupling strength index for soil moisture and vapor pressure deficit, it was found that there was a strong land-atmosphere coupling over the Yangtze River basin during July–August 2022. The attribution by using CMIP6 climate models suggested that land-atmosphere coupling increased the risks of flash drought intensity and onset speed like 2022 by 61%±6% and 64%±7% under natural climate forcings, and the synergy of coupling and anthropogenic climate change would increase the risks by 75%±22% and 85%±12%. Our findings emphasized the role of land-atmosphere coupling combined with anthropogenic climate change in intensifying flash droughts. [ABSTRACT FROM AUTHOR]

Droughts and climate change are causing severe and persistent dust storms in the arid and hot regions. The potential existence of significant relationships between the Oceanic Niño Index (ONI), Indian Ocean Dipole (IOD), and the MERRA-2 dust column mass density data are thus investigated in the State of Kuwait during 1990–2021 as a study case in the hot and arid regions. The findings show that the correlation starts from ONI-DJF (December–January-February) with the Pearson test value of -0.36 and increasing to a value of -0.55 on ONI-AMJ (April-May-June), the same results were obtained when applying the Spearman correlation test. The correlation exists between the July dust column mass density and IOD-January with a value of -0.484 and − 0.544 over Pearson and ' 'Spearman's test, respectively, all estimated p-values are lower than 0.05. The results of the One-Way ANOVA show that the output is pretty straightforward and statistically significant at p > 0.05, which was confirmed by the nonparametric Kruskal–Walli's test and Mann-Whitney Test. This considerable correlation means that active dust storms are linked with La Niña, while light dust storms occur during the El Niño event. A positive correlation occurs between precipitation and ONI - SON (September-October-November), while a negative correlation is found between precipitation and IOD-July. Our preliminary findings in this paper indicate that an appearance of -0.7°C in ONI-DJF could serve as a definitive marker of the La Nina phase and an indicator for at-risk communities to prepare for the expected activity dust storm. [ABSTRACT FROM AUTHOR]

The analysis of extreme precipitation events plays a crucial role in the management of water resources, infrastructure, public water supply, agriculture, fire control, and public health. For an accurate characterization of precipitation events using historical series, the observed variations must be solely attributable to weather and climate conditions. This study aimed to identify homogeneous gauge stations in Paraná State, southern Brazil, based on four statistical tests (SNHT, Buishand, Pettitt, and Von Neumann) and conduct a homogeneity analysis of daily rainfall data. Missing values were imputed into the time series, and only stations with up to 25% of data gaps were included. Of the 482 stations analyzed in the state, 73.7% (n = 355) demonstrated homogeneity, 11.6% (n = 56) were considered doubtful, and 14.7% (n = 71) were deemed suspect. The highest number of homogeneity breaks was recorded from 1990 to 2005. The number of breaks during this period was estimated at 75 (59.1%) by SNHT, 86 (67.7%) by the Buishand test, and 89 (70.1%) by the Pettitt test. The year with the highest number of homogeneity breaks was 1998, with 81 breaks identified by the Pettitt test. These breaks may be related to El Niño and La Niña phenomena, given that a large sample of rainfall stations was analyzed in the study. [ABSTRACT FROM AUTHOR]

In this study we defined the association of SACZ episodes with ENOS phases during the 2000–2021 summer seasons, considering November to March months, and the circulation associated patterns. Each SACZ episode was classified when OLR values were below 220 W m− 2 and precipitable water values above 45 kg m− 2 for more than three consecutive days. The association between ONI and the annual number of days with SACZ and the number of SACZ episodes shows linear correlation of -0.44 and − 0.34, respectively, showing the prevalence of SACZ episodes during the La Niña phase. Analysis of the entire series shows a linear annual mean increase of ~ 16 days with SACZ episodes from 2000 up to 2021. Sea level pressure anomalies between El Niño and La Niña periods present meridional dipole patterns between northern and southern South Atlantic, including the southamerican continent. OLR anomalies fields present negative (positive) values during LN (EN) periods over the northern South America extending to SACZ areas, helping to explain the higher number of SACZ episodes in LN (63 episodes) than in EN (29 episodes) periods. Both SLP and OLR anomalous patterns are associated with higher moisture convergence in the SACZ area in LN than in EN periods. Analysis of very dry (2014–2015) and very rainy (2020–2021) summer seasons over southeastern South America, illustrating El Niño and La Niña periods, respectively, shows strengthened upward movement over southwestern South America and weakened upward movement over northeastern in the former summer season and the opposite signals in the second one. These patterns were associated with typical circulation at low and high tropospheric levels: the upper level cyclonic vortex and the subtropical South Atlantic high pressure displacement to continental areas during the very dry period, 2014–2015, and the displacement of both systems, in upper and low levels, to the ocean during the very rainy period, 2020–2021. [ABSTRACT FROM AUTHOR]

Unprecedented precipitation deficits in the 2022-2023 growing season across the primary wheat-producing region in the United States caused delays in winter wheat emergence and poor crop growth. Using an integrated approach, we quantitatively unraveled a 37% reduction in wheat production as being attributable to both per-harvested acre yield loss and severe crop abandonment, reminiscent of the Dust Bowl years in the 1930s. We used random forest machine learning and game theory analytics to show that the main driver of yield loss was spring drought, whereas fall drought dominated abandonment rates. Furthermore, results revealed, across the US winter wheat belt, the La Niña phase of the El Niño Southern Oscillation (ENSO), increased abandonment rates compared to the El Niño phase. These findings underscore the necessity of simultaneously addressing crop abandonment and yield decline to stabilize wheat production amid extreme climatic conditions and provide a holistic understanding of global-scale ENSO dynamics on wheat production. [ABSTRACT FROM AUTHOR]

Rainfall erosivity (RE), a pivotal external force driving soil erosion, is impacted by El Niño/Southern Oscillation (ENSO). Studying the spatiotemporal variations in RE and their response to ENSO is essential for regional ecological security. In this study, a daily RE model was identified as a calculation model through an evaluation of model suitability. Daily precipitation data from 1971 to 2020 from 38 meteorological stations on Hainan Island, China, were utilized to calculate the RE. The multivariate ENSO index (MEI), Southern Oscillation Index (SOI), and Oceanic Niño Index (ONI) were used as the ENSO characterization indices, and the effects of ENSO on RE were investigated via cross-wavelet analysis and binary and multivariate wavelet coherence analysis. During the whole study period, the average RE of Hainan Island was 15,671.28 MJ·mm·ha−1·h−1, with a fluctuating overall upward trend. There were spatial and temporal distribution differences in RE, with temporal concentrations in summer (June–August) and a spatial pattern of decreasing from east to west. During ENSO events, the RE was greater during the El Niño period than during the La Niña period. For the ENSO characterization indices, the MEI, SOI, and ONI showed significant correlations and resonance effects with RE, but there were differences in the time of occurrence, direction of action, and intensity. In addition, the MEI and MEI–ONI affected RE individually or jointly at different time scales. This study contributes to a deeper understanding of the influence of ENSO on RE and can provide important insights for the prediction of soil erosion and the development of related coping strategies. [ABSTRACT FROM AUTHOR]

NOAA Daily Optimum Interpolation Sea Surface Temperature (DOISST) and other similar sea surface temperature (SST) products indicate that the globally averaged SST set a new daily record in March 2023. The record‐high SST in March was immediately broken in April, and new daily records were set again in July and August 2023. The SST anomaly (SSTA) persisted at a record high from mid‐March to the remainder of 2023. Our analysis indicates that the record‐high SSTs, and associated marine heatwaves (MHWs) and even super‐MHWs, are attributed to three factors: (a) a long‐term warming trend, (b) a shift to the warm phase of the multi‐decadal Pacific‐Atlantic‐Arctic (PAA) mode, and (c) the transition from the triple‐dip succession of La Niña events to the 2023–24 El Niño event. Plain Language Summary: Observation‐based analyses such as the NOAA DOISST show that global mean SST reached a record high in April 2023, breaking the previous record of global mean SST set in March 2016, and the April 2023 record of global mean SST was broken again in July and August 2023. Our study indicates that these record‐breaking SSTs in 2023 resulted from record‐high SSTs over much of the global oceans and associated with widespread marine heatwaves (MHWs). Further analyses show that the record‐high SSTs are attributed to a long‐term‐warming trend associated with increasing greenhouse gases, a shift to the warm phase of a multidecadal Pacific‐Atlantic‐Arctic (PAA) mode, and a warming associated with the transition from 2020–23 La Niña events to the 2023–24 El Niño event. Key Points: Global mean sea surface temperature (SST) in 2023 set a record highRecord‐high SST was associated with widespread marine heatwaves (MHWs) and super‐MHWs throughout the oceansRecord‐high SST was attributed to the multi‐decadal warming trend, warm phase of Pacific‐Atlantic‐Arctic mode, and 2023–24 El Niño event [ABSTRACT FROM AUTHOR]

El Niño Southern Oscillation (ENSO) diversity is characterized based on the longitudinal location of maximum sea surface temperature anomalies (SSTA) and amplitude in the tropical Pacific, as Central Pacific events are typically weaker than Eastern Pacific events. SSTA pattern and intensity undergo low‐frequency modulations, affecting ENSO prediction skill and remote impacts, and resulting in low‐frequency changes in ENSO variance. Yet, how different ENSO types contribute to these decadal variance changes remains unclear. Here, we decompose the low‐frequency changes of ENSO variance into contributions from ENSO diversity categories. We propose a fuzzy clustering of monthly SSTA to allow for non‐binary event category memberships, where each event can belong to different clusters. Our approach identifies two La Niña and three El Niño categories and shows that the major shift of ENSO variance in the mid‐1970s was associated with an increasing likelihood of strong La Niña and extreme El Niño events. Plain Language Summary: The El Niño Southern Oscillation (ENSO) is a climate phenomenon that involves changes in ocean temperatures in the central and eastern tropical Pacific and greatly influences the weather around the globe. ENSO events are usually categorized based on where these temperature variations are the strongest and how intense they are. However, these categories are at times ambiguous and the way ENSO behaves can change over decades. Our study introduces a new way to estimate how different kinds of ENSO events contribute to its overall variation over time. We base our variability analysis on a fuzzy categorization of ENSO events, which results in three different kinds of El Niño events and two kinds of La Niña events. We find that the decadal changes in ENSO variance, including the decadal shift in the mid‐1970s, were primarily associated with strong La Niña and extreme El Niño events. Key Points: Using a fuzzy categorization, five different El Niño Southern Oscillation (ENSO) types are identified in observationsExtreme El Niño events emerge as a distinct categoryStrong La Niña and Extreme El Niño categories mainly contributed to the shift in decadal ENSO variance around 1970 [ABSTRACT FROM AUTHOR]

Water years (WY) 2017 and 2023 were anomalously wet for California, each alleviating multiyear drought. In both cases, this was unexpected given La Niña conditions, with most seasonal forecasts favoring drier‐than‐normal winters. We analyze over seven decades of precipitation and snow records along with mid‐tropospheric circulation to identify recurring weather patterns driving California precipitation and Sierra Nevada snowpack. Tropical forcing by ENSO causes subtle but important differences in these wet weather patterns, which largely drives the canonical seasonal ENSO‐precipitation relationship. However, the seasonal frequency of these weather patterns is not strongly modulated by ENSO and remains a primary source of uncertainty for seasonal forecasting. Seasonal frequency of ENSO‐independent weather patterns was a major cause of anomalous precipitation in WY2017, record‐setting snow in WY2023, and differences in precipitation outcome during recent El Niño winters 1983, 1998, and 2016. Improved understanding of recurrent atmospheric weather patterns could help to improve seasonal precipitation forecasts. Plain Language Summary: In 2017 and 2023, California experienced unexpectedly wet conditions despite predictions of dry winters due to La Niña. In 2016, seasonal predictions in California favored wet conditions due to the very strong El Niño, but the season was normal‐to‐dry statewide. Understanding relationships between El Niño/La Niña and recurring atmospheric weather patterns driving individual storms is needed to improve seasonal forecasts. We studied historical relationships between weather patterns that bring rain and snow to the region and the El Niño Southern Oscillation (ENSO). We find ENSO influences important characteristics of weather patterns once they make landfall in California, making El Niño storms generally wetter in coastal southern California and Desert Southwest. However, ENSO does not strongly affect how often these patterns occur in a season, which makes seasonal precipitation forecasts challenging. The frequency of certain weather patterns not tied to ENSO played important roles in the unusual rainfall of 2017, the heavy snowfall of 2023, and the drier than expected winter of 2016. Understanding these weather patterns provides operationally and scientifically relevant context for future seasonal forecasts by highlighting that while ENSO only minimally influences the frequency of certain impactful storm types, it does change the precipitation characteristics of these storms. Key Points: Weather regime type and frequency are key drivers of winter seasons with anomalous precipitation and/or snow accumulation in CaliforniaENSO does not modulate the seasonal frequency of weather regimes impacting the coast, presenting a challenge for seasonal forecastingENSO modulates synoptic circulation characteristics of key weather regimes which produces the canonical ENSO‐precipitation relationship [ABSTRACT FROM AUTHOR]

This study investigates the specific circulation anomalies that have sustained the low Antarctic sea ice state since 2016. Firstly, we find a significant strengthening and southward shift in the Ferrel Cell (FC) during 2016–2022, resulting in a marked increase in southward transport of heat and moisture. Secondly, this enhanced FC is closely associated with a stronger mid‐latitude wave pattern. This pattern is zonally asymmetric and greatly amplifies the poleward advections of heat and moisture, leading to the increased downward longwave radiation, more liquid precipitation and sea ice retreat in specific regions, including the western Pacific and Indian Ocean sectors, Ross and northern Weddell Seas. The mechanism deduced from the short‐term period is further supported by the results of 40 ensemble members of simulations. The southward expansion of the FC and sea ice decline are closely linked to La Niña‐like conditions but may also be driven by anthropogenic global warming. Plain Language Summary: Following the sudden decline in 2016, the Antarctic sea ice extent has persisted at historically low levels. In 2023, it reached unprecedented record lows. However, the specific atmospheric circulation anomalies that have sustained the Antarctic sea ice at low levels are still unknown. It is well‐established that the Ferrel Cell, a mid‐latitude atmospheric meridional circulation, plays a pivotal role in the energy exchange between the high‐ and mid‐latitudes. Our findings indicate that the enhanced Ferrel Cell zonally intensified southward transport of heat and moisture over the sea ice regions, which sustains the overall low Antarctic sea ice state. Additionally, in the horizontal plane, the enhanced mid‐latitude wave pattern is responsible for the regional sea ice retreat over the western Pacific sector, Ross Sea, Indian Ocean sector, and northern Weddell Sea, and is also closely associated with the enhanced Ferrel Cell. The effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations. Therefore, this study suggests that concurrent with the southward shifting of the Ferrel Cell, the stronger warm and moist air intrusions, and the increased liquid precipitation, restrict the Antarctic sea ice expansion following its sudden decline. Key Points: Since 2016, the low Antarctic sea ice extent has persisted, consistent with heat and moisture accumulation over the sea ice edgesThe Ferrel Cell was enhanced and shifted southward, leading to the increased southward heat/moisture advection, and liquid precipitationThe effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations [ABSTRACT FROM AUTHOR]

The Pacific/North American (PNA) pattern is a major low‐frequency variability in boreal winter. A recent modeling study suggested that PNA variability increases through extratropical atmosphere‐ocean coupling, but the effect was not fully extracted due to a particular experimental design. By comparing coupled and two sets of uncoupled large‐ensemble global model simulations, here we show that the PNA‐induced horseshoe‐shaped sea‐surface temperature (SST) anomaly in the North Pacific returns a non‐negligible influence on the PNA itself. Its magnitude depends on the presence or absence of atmosphere‐ocean coupling. The coupling accounts for ∼16% of the PNA variance, while the horseshoe‐shaped SST anomaly explains only 5% under the uncoupled condition. The coupling reduces the damping of available potential energy by modulating turbulent heat fluxes and precipitation, magnifying the PNA variance. Precipitation processes in the extratropics as well as tropics are therefore important for realistically representing PNA variability and thereby regional weather and climate. Plain Language Summary: Atmospheric flow is not entirely random; patterns of circulation variability appear recurrently in the same regions, known as teleconnection patterns. A major wintertime teleconnection pattern over the North Pacific‐North American sector is called the Pacific/North American (PNA) pattern. It causes strong fluctuations in precipitation, air temperature, and pressure over North America through persistent strengthening or meandering of the jet stream. While the influence of tropical ocean variability, such as El Niño/La Niña, on the formation and persistence of the PNA has been known, the role of the extratropical ocean remains unclear. Here we perform a vast number of numerical model simulations to detect the influence of the extratropical ocean on PNA. We show that the atmosphere‐ocean coupling (two‐way interaction between the ocean and atmosphere) enhances the PNA variability (i.e., the magnitude of meandering and strengthening of the westerlies) compared to the uncoupled condition. Furthermore, we propose possible mechanisms behind this enhancement. The findings of this study are expected to contribute to improving the accuracy of long‐term forecasts, such as one‐month predictions, and reducing uncertainty in future climate change projections through the improvement of numerical models. Key Points: Extratropical air‐sea coupling enhances the variance of the Pacific/North American (PNA) pattern, which explains 16% of the total varianceThe enhancement is due to the reduced damping of available potential energy through modulations of turbulent heat fluxes and precipitationAtmosphere‐only simulation is likely to underestimate the impact of extratropical sea surface temperature anomalies on the PNA variability [ABSTRACT FROM AUTHOR]

Local meteorology over the Great Barrier Reef (GBR) can significantly influence ocean temperatures, which in turn impacts coral ecosystems. While El Niño–Southern Oscillation (ENSO) provides insight into the expected synoptic states, it lacks details of anticipated sub‐seasonal weather variability at local scales. This study explores the influence of the Madden‐Julian oscillation (MJO) on Australian tropical climate, both independently and in combination with ENSO, focusing on GBR impacts. We find that during El Niño periods, including the summer of 2009/10, faster propagating MJO patterns can disrupt background warm, dry conditions, and potentially provide cooling relief via increased cloud cover and stronger winds. In La Niña periods, such as the summer of 2021/22, the MJO tends to be prevented from passing the Maritime continent, forcing it to remain in a standing pattern in the Indian Ocean. This leads to decreased cloud cover and weaker winds over the GBR, generating warm ocean anomalies. Plain Language Summary: Bleaching is likely when tropical corals are exposed to ocean temperatures above a threshold for a prolonged period. In austral summer, tropical weather over the Great Barrier Reef (GBR) can vary from hot and sunny to stormy with rain and strong winds. During El Niño, summer weather over the GBR is typically warm, still, and dry, increasing the likelihood of coral bleaching due to increased exposure to solar radiation and decreased mixing. During La Niña, tropical storms, with cooling effects through increased rainfall and cloud cover, are more typical. The Madden‐Julian oscillation (MJO) is an eastward moving storm pattern near the equator that can also influence the background climate over the GBR. We find that the MJO can significantly influence the weather variability over the GBR, altering the expected states of El Niño and La Niña periods. Key Points: Composite maps show how the Madden‐Julian oscillation (MJO) can change meteorological patterns on the Great Barrier ReefCluster analysis is used to show the types of MJO propagation patterns likely to occur during El Niño and La Niña periodsOcean temperature variability is discussed with El Niño/La Niña phases as the background states and the MJO as a sub‐seasonal modulator [ABSTRACT FROM AUTHOR]

• High tropospheric NO 2 VCDs were detected in Rosario, area of more than 1 million people. • Rural areas showed high NO 2 levels during the fire events. • We analyzed tropospheric NO 2 VCD and air masses by using TROPOMI data and HYSPLIT. • Maximum daily FRP value of 10 GW was detected by VIIRS/S-NPP. Wildfires in the Paraná River Delta started to be a common situation in the year 2008 and during the first years of the 2020́s decade: 2020, 2021, 2022. These fires affected natural areas, primarily the islands within the delta, situated in front of Rosario city (32.95 °S, 60.67 °W, 25 meters above sea level (m.a.s.l.)), Argentina. They mostly occur during the period between June and September each year and are more intense when a strong La Niña event is present. The aim of this study is to examine the association between the propagation of high intensity nitrogen dioxide ( NO 2 ) plumes and the significant fire events that occurred in the Paraná River Delta from 6 to 17 September 2022. Satellite data of NO 2 obtained from the TROPOspheric Monitoring Instrument (TROPOMI) on board the European Space Agency (ESA) Sentinel-5 Precursor satellite, air mass forward trajectories performed with The Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT), Fire Radiative Power (FRP) data provided by Visible Infrared Imaging Radiometer Suite (VIIRS) on board The National Oceanic and Atmospheric Administration - 20 (NOAA-20) and Suomi National Polar-orbiting Partnership (S-NPP) satellites, Aerosol Optical Depth (AOD) from VIIRS S-NPP and Smoke Injection Height from Multi-Angle Implementation of Atmospheric Correction (MAIAC) Thermal Technique were employed. The trajectories followed by the air masses coming from the major fire sources locations nearby Rosario city and its surrounding area, were analyzed at altitudes of 20, 500, 1000, 1500 and 2000 m above ground level (AGL) in order to evaluate the impact of the NO 2 clouds present in the atmosphere and carried by the winds, at different sites of Rosario and its adjacent region. The NO 2 plumes has the potential to pose a significant health risk for this region, inhabited by an approximate population of one and a half million individuals. This risk is contingent upon the altitude where the highest levels of NO 2 in the tropospheric column are found. Tropospheric vertical column densities (VCDs) of NO 2 in the range of 4.68 × 10 14 to 1.66 × 10 16 molecules/cm2 were determined. The results indicate a robust correlation between elevated tropospheric NO 2 VCD values and intense fires, as characterized by their FRP. Additionally, high tropospheric NO 2 VCDs were observed to impact cities and towns located in close proximity to the fires. In particular, the unusually high tropospheric NO 2 VCDs determined for the towns of Fighiera and Pueblo Esther, situated along the coast and near the Paraná River Delta, are noteworthy. This is uncommon considering they are small towns in rural areas that typically have good air quality. The results regarding FRP, provided by VIIRS on board NOAA-20 and S-NPP satellites, indicate that the fire characterization of hotspots during the considered period had a mean value in the range of 20.17–21.47 MW. On specific days (12, 13 and 16 September 2022), the cumulative (total) daily values were very high, ranging from 2000 to 10000 MW. Furthermore, on 12 and 13 September 2022, the smoke aerosols did not reach significant altitudes in the atmosphere, remaining within the range of 0 to 1500 m AGL. During the fire period, AOD values close to 1 were observed within the fire plume. Notably, Puerto San Martín (0.27), San Lorenzo (0.22), and Ibarlucea (0.20) recorded higher average AOD values compared to other sites. The remaining sites generally exhibited lower average AOD values, with a slight distinction between rural locations (Pueblo Esther: 0.14 and Fighiera: 0.14) and the city center of Rosario (0.09). [ABSTRACT FROM AUTHOR]

In the context of escalating climate change-induced impacts on water resources, robust monitoring tools are imperative. Satellite altimetry, benefiting from technical improvement such as the use of SAR and InSAR techniques and tracking modes considering topography, is emerging as a crucial means of estimating lake levels, data that are fundamental to understanding climate dynamics. This study delves into the use of satellite-altimetry-determined water levels to analyze changes in water storage and superficial area in Lake Ranco, in south-central Chile, from 1995 to 2023. The main objective is to provide valuable information for water-resource management and policy formulation. Leveraging AlTiS software (v2.2.9-0-gf5938ab), radar-altimetry data from the missions ERS-2, ENVISAT, SARAL, and Sentinel-3A were processed, generating a complete time series of water levels. The lake-level data were complemented by the bathymetric data for the lake to obtain the variation in the area and volume in the period 1995–2023. These results were analyzed with respect to hydrometeorological data from the study area, such as precipitation, temperature, relative humidity, and potential evapotranspiration. Additionally, the effects of ENSO (ENSO 3.4 index) and the Pacific Decadal Oscillation index (PDO) were considered. Results reveal a strong correlation between altimetry-derived lake levels and observed in situ data, with a mean square error of 0.04 m, a coefficient of determination of 0.99, an index of agreement of 0.99, and a Kling−Gupta efficiency of 0.90. The analysis of climatic variables showed that variations in lake level coincide with changes in precipitation within the study area and also showed the influence of variations in temperature and potential evapotranspiration. Additionally, the effects of the ENSO phenomenon can be seen within the study area for its cold phase (i.e., La Niña) in the 2010–2012 period and for its warm phase (i.e., El Niño) in the 2015–2016 period, with a decrease and increase in precipitation, respectively. These effects were enhanced when the cold and warm phases of the ENSO and PDO phenomena occured. The successful application of satellite altimetry demonstrated in this study underscores its critical role in advancing our understanding and management of water resources amidst changing climate scenarios. [ABSTRACT FROM AUTHOR]

Recent studies have shown that deep learning (DL) models can skillfully forecast El Niño–Southern Oscillation (ENSO) events more than 1.5 years in advance. However, concerns regarding the reliability of predictions made by DL methods persist, including potential overfitting issues and lack of interpretability. Here, we propose ResoNet, a DL model that combines CNN (convolutional neural network) and transformer architectures. This hybrid architecture enables our model to adequately capture local sea surface temperature anomalies as well as long-range inter-basin interactions across oceans. We show that ResoNet can robustly predict ENSO at lead times of 19 months, thus outperforming existing approaches in terms of the forecast horizon. According to an explainability method applied to ResoNet predictions of El Niño and La Niña from 1- to 18-month leads, we find that it predicts the Niño-3.4 index based on multiple physically reasonable mechanisms, such as the recharge oscillator concept, seasonal footprint mechanism, and Indian Ocean capacitor effect. Moreover, we demonstrate for the first time that the asymmetry between El Niño and La Niña development can be captured by ResoNet. Our results could help to alleviate skepticism about applying DL models for ENSO prediction and encourage more attempts to discover and predict climate phenomena using AI methods. [ABSTRACT FROM AUTHOR]

Much research has raised concerns about how a warming planet will interact with natural cyclical climatic variations, and the implications for the resilience and vulnerability of coastal communities. As the anticipated effects of climate change will continue to intensify, it is necessary to understand the response and adaptive capacity of individuals and communities. Coastal communities in Ecuador have evolved in an environment of such cyclical climatic variations referred to as El Niño-Southern Oscillation (ENSO) and La Niña. These climatic events are frequently characterized by extreme variations in precipitation, violent storms, and coastal flooding during El Niño and lowered sea water temperatures and drought during La Niña. This paper draws on survey data and long-term ethnographic research in Ecuadorian coastal communities to explore how fishers understand the impacts of ENSO and implications for their livelihood decisions and resilience to climate variability. The results suggest that fishers along the coast of Ecuador understand and respond differentially to the impacts of ENSO depending on social, cultural, environmental, and geographical factors. These differential levels of response suggest that livelihood diversification may uphold social resilience, which has implications for how coastal communities may adapt to the increasingly harsh weather conditions predicted by many climate models. Our findings further suggest that the impacts of El Niño are more salient than the impacts of La Niña; these findings have significant implications for fisheries management and science communication. [ABSTRACT FROM AUTHOR]

After a long La Niña event (2020-2023), the US National Oceanographic and Atmospheric Administration warned of a quick transition to an El Niño phase. As a monitoring of sea surface temperature (SST) and chlorophyll-a (Chl-a) levels in the Gulf of California, Mexico, this study aims to show the evolution of both parameters during the first seven months of 2023. It compares them with the first seven months of 2015 when an extreme El Niño event occurred. Satellite data from the Moderate Resolution Imaging Spectroradiometer were obtained from which maps of both variables were constructed to quantitatively assess the changes in the SST and the Chl-a levels during the selected periods. Satellite data/pixels were extracted from the southern region of the gulf, in the connection between the gulf and the open Pacific Ocean. The results showed a gradual increase in the SST values from February to July of 2023 with 20.43, 22.29, 22.77, 27.88, 28.72 and 31.64ºC, respectively (a thermal variation of 11.21ºC), while Chl-a levels showed a decrease over the same period, from 1.81, 1.10, 0.78, 0.24, 0.19 mg m-3 to unusually low values of 0.11 mg m-3, respectively (a reduction of 1.70 mg m-3 ). A similar pattern was found in 2015, with increased SST and decreased Chl-a. Were the observed patterns in 2023 the early signals of El Niño in the Gulf of California? [ABSTRACT FROM AUTHOR]

This study demonstrates asymmetric relationships between El Niño–Southern Oscillation (ENSO) and tropical cyclones (TCs) affecting the Philippines during October–December. In El Niño or La Niña years, the number of TCs impacting the Philippines may increase or decrease. These variations result in four ENSO–TC variability types all of which exhibit strong sea surface temperature (SST) anomalies across the equatorial eastern Pacific. The major difference between the active and inactive types in terms of El Niño or La Niña years is related to the magnitude of SST anomalies in the tropical western Pacific (TWP) over the 120°–150°E region. During El Niño years, moderate cold SST anomalies in this TWP region cause an anomalous divergent centre around the 120°–130°E zone to evoke an anomalous cyclone east of the Philippines. In the western North Pacific (WNP), this anomalous cyclone causes more TCs to form and move toward the Philippines, resulting in active TC activity. For the inactive TC type during El Niño years, very weak cold SST anomalies in the aforementioned TWP region correspond with a northeastward‐extended anomalous divergent centre over the 120°–140°E, 10°S–20°N zone and an anomalous anticyclone across the Philippines and its eastern side. Decreases in the formation of the WNP TC and movement toward the Philippines lead to inactive TC activity. The large‐scale anomalies and regulating processes are mainly opposite between the active TC type during El Niño years and the inactive TC type during La Niña years. These two types are influenced by interdecadal variability of the Pacific decadal oscillation. Opposite anomalies and regulating processes also occur between the inactive TC type during El Niño years and the active TC type during La Niña years. The former type is jointly modulated by the positive Indian Ocean Dipole mode and central‐Pacific El Niño. [ABSTRACT FROM AUTHOR]

Sardinops melanostictus is mainly distributed in Northwest Pacific Ocean, which is significantly affected by climate change. The carbon and nitrogen stable isotope ratios of the muscles of Japanese sardines from the Northwest Pacific Ocean were measured based on samples taken by the ocean-going fishery resources survey ship "Songhang" in the high seas of the Northwest Pacific Ocean between June and July 2021. The GAM model was then used to examine the effects of both biotic (body length) and abiotic (Latitude, sea surface temperature, offshore distance, chlorophyll-a) factors on the stable nitrogen isotopes; The differences in the trophic niche among sex and body length groups were also analyzed in Japanese sardines in Northwest Pacific Ocean. The results showed that there was no significant difference in muscle δ13C and δ15N between males and females during La Niña years. However, both δ13C and δ15N differed among body length groups. The GAM model's results showed that as body length increases, both δ13C and δ15N exhibited a trend of first decreasing and then increasing; δ13C also exhibits this trend with increasing latitude; δ15N exhibits a negative correlation with both offshore distance and chlorophyll-a. The overlap rate between female and male niche is generally high, with a similar niche width between females and males ranging from 100 to 160 mm. The width of the ecological niche varied across the length groups, and its position changed with growth. However, compared to males, females have substantially broader niches, ranging from 161 to 220 mm. In contrast to usual years, the La Niña year's readings for δ13C and δ15N are all low. The study demonstrates that the feeding ecology of Japanese sardines in Northwest Pacific Ocean varies depending on sex and body length, and that changes in the marine environmental elements under La Niña events affected the feeding ecology of Japanese sardines. [ABSTRACT FROM AUTHOR]

This paper discussed the use of stable isotope compositions of precipitation (δ2H and δ18O) to understand its characteristics and the parameters controlling meteorological conditions in Malaysia. The meteoric water line for Malaysia, or MMWL established in this study are δ2H = (7.43 ± 0.05)δ18O + (7.33 ± 0.11) (n = 595, r2 = 0.97) for individual values, and δ2H = (7.07 ± 0.20)δ18O + (4.90 ± 0.75) (n = 51, r2 = 0.96) for annual precipitation weighted means. No major variations in local meteoric water lines established between the stations, except for one (i.e., Cameron Highlands), which was found to be significantly different due to its high deuterium excess, or d value, attributed to moisture recycling (re–evapotranspiration) from the surrounding dense rainforest area. The precipitation moisture came from the two monsoon systems; the Northeast monsoon (NEM) and Southwest monsoon (SWM). They differ only slightly in their isotope signatures, where the NEM (winter monsoon) is 0.38‰ more negative than the SWM (summer monsoon), and the rainfall amount and temperature have a relatively weak influence on the stable isotopes in precipitation. Rainfall δ18O is poorly correlated with the monthly rainfall amount and temperature, with very low r2 values (–0.4‰/100 mm; 0.09 and 0.7‰/°C; 0.06, respectively). The seasonal variability of isotopic compositions of precipitation in this region is controlled by the insubstantial but conspicuous inverse correlation amount effect. The seasonal patterns of δ2H and δ18O are evident, with higher values observed during the NEM and lower values observed during SWM. However, the temporal variations of rainfall δ2H and δ18O during NEM and SWM are almost indistinguishable due to local climatic conditions, prevailing atmospheric circulations, and sources of precipitation. The apparent sign of El Niño and La Niña events (2015 and 2017, respectively) of the El Niño–Southern Oscillation (ENSO) cycle were successfully identified from this study, indicated by the heavier δ18O from the peaks in the annual precipitation amount versus δ18O annual precipitation weighted mean plot, while La Niña corresponds to the lighter values of the rainfall isotopes. [ABSTRACT FROM AUTHOR]

El Niño events display a large diversity in terms of spatial pattern, temporal evolution, and amplitude, which may change over time due to climate change or internal variability. We used the Extended Reconstructed Sea Surface Temperature (SST), version 5 (ERSSTv5) dataset and applied a nonlinear K-means cluster analysis to the evolution of SST anomalies in the equatorial Pacific for 33 El Niño years from 1901 to 2020. Based on the analysis of the spatio-temporal evolution of El Niño events, we identified 4 types of El Niño, which include basin-wide, eastern Pacific (EP), central Pacific (CP), and successive El Niño. EP and CP El Niño events are weaker and terminate faster than basin-wide El Niño, whereas successive El Niño events are often (83 % ) followed by a La Niña event. The frequency of basin-wide and particularly CP El Niño events has started to increase since the mid-1950s, while a gradual decrease in the frequency of both EP and successive El Niño is identified during the study period. We have analyzed the linkage between the identified 4 types of El Niño and the Indian Ocean Dipole (IOD). A statistically significant positive correlation is found between basin-wide El Niño and the IOD in boreal autumn, implying that a developing basin-wide El Niño generally can trigger a positive IOD in boreal autumn. Our results have important implications for a better understanding of interdecadal changes in the type of El Niño events and provide a framework to improve the predictability of the IOD. [ABSTRACT FROM AUTHOR]

Factors related to rainfall variabilities in southern and southeastern Ethiopia have not yet been addressed. The extreme wet and dry events caused by atmospheric circulation patterns during the March-April-May periods were studied using 1991–2022 data from Climate Hazard Group InfraRed Precipitation with Stations (CHIRPS) and atmospheric circulation anomalies datasets. Empirical orthogonal function (EOF), precipitation concentration index (PCI), and coefficient of variation (CV) are used to determine the interannual variation. The study revealed that both PCI and CV exhibit rainfall variability with increasing magnitude from west to east of the region, while the first mode of EOF showed a dominantly uniform pattern and accounted for 48.8% of the observed variance. Eight extreme dry and four extreme wet years were also observed. Composite analyses suggested that the study area during wet years were characterized by convergence or divergence of velocity potential, and decrease or increase of vertical velocity at lower or upper troposphere which favorable conditions to vertical motion, while opposite phenomena observed during dry periods. Westerly winds from the southern Atlantic Ocean were associating with wet, while easterly winds from the Indian Ocean with dry. The study found a negative correlation between rainfall and Azores SLP, a positive correlation with Indian Ocean SST, and 62.5% of the driest periods coexisted with La Niña events. In summary, Indian Ocean SST, Nino Index 3.4, Azores SLP, South Atlantic 850-hPa westerly winds, and vertical velocity are predictive factors that should be considered in the rainfall forecasting process in the study area. [ABSTRACT FROM AUTHOR]