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The 1997/1998 El Niño event caused mass coral bleaching and mortality in many tropical and subtropical regions, including corals on Green Island, Taiwan, in the northwestern Pacific Ocean. This study analyzed coral carbon isotope ratios (δ13C), oxygen isotope ratios (δ18O), and Sr/Ca ratios for 29 years, including the 1997/1998 El Niño period, to examine how high water temperature events are recorded in coral geochemical indicators. Sr/Ca ratios in coral skeletons from Green Island show the lowest peak, means the highest temperature during the 1997/1998 El Niño period. However, we couldn't observe high-temperature events on δ18O. Furthermore, a negative δ13C shift was observed after El Niño events. The regime shift of δ13C might have been caused by temporal bleaching and/or a decrease in symbiotic algae due to high water temperature stress under the continuous decrease in δ13C in DIC due to the Suess effect. [ABSTRACT FROM AUTHOR]

The article examines the construction of autobiographical discourse in Ramón Gómez de la Serna's book "Automoribundia." It delves into themes of death, identity, and the ethical responsibility of the narrator. The author emphasizes the importance of truth and authenticity in the autobiographical genre, while acknowledging the fluid nature of identity. The article also discusses Gómez de la Serna's writing style, influences, and his exploration of solitude and rejection of wealth and ambition. Additionally, it touches on his relationship with objects, women, and his political affiliations. [Extracted from the article]

We demonstrate a 1-year lagged extratropical response to the El Niño-Southern Oscillation (ENSO) in observational analyses and climate models. The response maps onto the Arctic Oscillation and is strongest in the North Atlantic, where it resembles the North Atlantic Oscillation (NAO). Unexpectedly, these 1-year lagged teleconnections are at least as strong as the better-known simultaneous winter connections. However, the 1-year lagged response is opposite in sign to the simultaneous response such that 1 year later, El Niño is followed by a positive NAO, whereas La Niña is followed by a negative NAO. The lagged response may also interfere with simultaneous ENSO teleconnections. We show here that these effects are unlikely to be caused by residual aliasing of ENSO cycles; rather, slowly migrating atmospheric angular momentum anomalies explain both the sign and the timing of the extratropical response. Our results have implications for understanding ENSO teleconnections, explaining observed extratropical climate variability and interpreting seasonal to inter annual climate predictions. [ABSTRACT FROM AUTHOR]

Deep convection in the Indo-Pacific warm pool is vital in driving global atmospheric overturning circulations. Year-to-year variations in the strength and location of warm pool precipitation can lead to significant local and downstream hydroclimatic impacts, including floods and droughts. While the El Niño-Southern Oscillation (ENSO) is recognized as a key factor in modulating interannual precipitation variations in this region, atmospheric internal variability is often as important. Here, through targeted atmospheric model experiments, we identify an intrinsic low-frequency atmospheric mode in the warm pool region during the austral summer, and show that its impact on seasonal rainfall is comparable to ENSO. This mode resembles the horizontal structure of the Madden-Julian Oscillation (MJO), and may play a role in initiating ENSO as stochastic forcing. We show that this mode is not merely an episodic manifestation of MJO events but primarily arises from barotropic energy conversion aided by positive feedback between convection and circulation. [ABSTRACT FROM AUTHOR]

The Atlantic Niño, a primary climatic variability mode in the equatorial Atlantic Ocean, exhibits pronounced variability not only in boreal summer but also in winter. However, the role of the winter Atlantic Niño in trans-basin interactions remains underexplored compared to its summer counterpart. Through analysis of observational reanalysis data since the mid-twentieth century, here we found that the winter Atlantic Niño significantly influences the development of El Niño–Southern Oscillation (ENSO), surpassing the impact of summer Atlantic Niño, with a longer lead time. This effect is reasonably captured in the CMIP6 Historical simulations from a multi-model ensemble perspective. Further analysis of the global warming scenario projects that the influence of winter Atlantic Niño on ENSO will persist into the future, in contrast to the reduced impact of summer Atlantic Niño. Therefore, these findings underscore the importance of further investigating the winter Atlantic Niño to gain a comprehensive understanding of trans-basin interactions and their future changes. [ABSTRACT FROM AUTHOR]

Tropical glaciers in the central Andes are vital water resources and crucial climate indicators, currently undergoing rapid retreat. However, understanding their vulnerability to the combined effects of persistent warming, the El Niño and La Niña climate phenomena, and interannual fluctuations remains limited. Here, we automate the mapping of key mass balance parameters on the Quelccaya Ice Cap (QIC) in Peru, one of the largest tropical ice caps. Using Landsat's near-infrared (NIR) band, we analyze snow cover area (SCA) and total area (TA) and calculate the accumulation area ratio (AAR) and equilibrium-line altitude (ELA) over nearly 40 years (1985–2023). Between 1985 and 2022, the QIC lost ∼58 % and ∼37 % of its SCA and TA, respectively. We show that the QIC's reduction in SCA and rise in ELA are exacerbated by El Niño events, which are strongly correlated with the preceding wet season's Oceanic Niño Index (ONI). Further, expansion in the QIC's SCA is observed during all La Niña years, except during the 2021–2022 La Niña. Although this is a singular event, it could indicate a weakened ability for SCA recovery and an accelerated decline in the future, primarily driven by anthropogenic warming. [ABSTRACT FROM AUTHOR]

Acknowledging the prolonged duration of the rainy season in Northeast India (NEI) compared to Central India, the official onset of the Indian summer monsoon over NEI is traditionally marked around 5 June, with May rainfall categorized as 'pre‐monsoon'. However, our study reveals that May rainfall in NEI occurs in active/break spells driven by persistent synoptic‐scale systems, contributing to a significant monsoon heat source during this period. Through an objective analysis, we determine that the climatological 'onset' in NEI actually occurs around 18 May, with withdrawal around 14 October, resulting in an extended rainy season of approximately 150 days. The enigma of the May onset, while the Intertropical Convergence Zone remains proximate to the equator, is addressed by identifying a conducive climate in May. This climate is characterized by low‐level cyclonic vorticity over the region, influenced by the interannual strengthening (weakening) by the Atlantic Niño (El Niño). The introduction of potential vorticity from extratropical transient Rossby waves in May significantly amplifies low‐level cyclonic vorticity by 3–4 times, acting as a catalyst for the monsoon onset in NEI. Furthermore, a 5–6 times intensification of northward moisture transport from the Bay of Bengal sustains the monsoon heat source post onset. The May onset is made feasible by the uplifting of low‐level cyclonic winds, facilitated by the horseshoe‐shaped orography around the Brahmaputra valley. This process is complemented by an increased local moisture content resulting from evapotranspiration. Our findings challenge conventional notions by demonstrating that a component of Indian summer monsoon rainfall in NEI is not directly related to the Intertropical Convergence Zone. This challenges the fundamental definition of the South Asian Monsoon and calls for a reassessment of the prevalent belief that the Indian monsoon season is confined to June–September in NEI. [ABSTRACT FROM AUTHOR]

Seasonal‐range predictability of summer climate in northwestern Europe is generally considered to be low. This is an increasing issue given the worsening impact of summer heatwaves, droughts and intense convective rainfall in a rapidly changing climate. In wintertime, predictive skill in the region is derived from a variety of sources, not least teleconnections with the El Niño‐Southern Oscillation (ENSO). Summer ENSO teleconnections, however, are often considered to be negligible. In this paper, we revisit the topic of summer teleconnections between ENSO and the North Atlantic‐European region. We build on previous work identifying upper tropospheric responses to tropical forcing, since dynamical teleconnections are most apparent at this level. Our results confirm that significantly increased geopotential heights are found stretching over the North‐Atlantic region and into western Europe when La Niña conditions are prevalent during summer. This pattern is part of the previously identified 'circumglobal' pattern of wider northern‐hemisphere height changes. We then look for these responses in a range of climate models used in operational seasonal prediction. While parts of the circumglobal pattern are weakly present, none of them produce the response seen over the North Atlantic, even when the effect of sampling on the observed teleconnection is accounted for. We additionally estimate the contribution of the previous (wintertime) phase of ENSO on the following summer. We find a significant delayed response, particularly in heights, to the earlier phase. The combination of the delayed and current responses gives height anomalies that are larger, on average, when ENSO changes phase from winter to summer. Finally, we show that a modest level of regional prediction skill from ENSO does exist. There is a contribution to skill in heights from the previous ENSO phase, but the equivalent contribution to the skill of zonal winds is smaller. [ABSTRACT FROM AUTHOR]

Studies have analyzed U.S. tornado variability and correlated F1–F5 tornado occurrence with various natural climate oscillations and anthropogenic factors. Using a relatively new empirical mode decommission (EMD) method that extracts time-frequency modes adaptively without priori assumptions like traditional time-series analysis methods, this study decomposes U.S. tornado variability during 1954–2022 into intrinsic modes on specific temporal scales. Correlating the intrinsic mode functions (IMFs) of EMD with climate indices found that 1. the U.S. overall tornado count is negatively (positively) correlated with the Atlantic Multidecadal Oscillation (AMO) index (the Southern Oscillation Index (SOI)); 2. the negative (positive) correlation tends to be more prevalent in the western (eastern) U.S.; 3. the increase in weak (F1–F2) and decrease in strong (F3–F5) tornadoes after around 2000, when both the AMO and the Pacific Decadal Oscillation (PDO) shifted phases, are likely related to their secular trends and low-frequency IMFs; and 4. the emerging Dixie Tornado Alley coincides with an amplifying intrinsic mode of the SOI that correlates positively with the eastern U.S. and Dixie Alley tornadoes. The long-term persistence of these climate indices can offer potential guidance for future planning for tornado hazards. [ABSTRACT FROM AUTHOR]

Drought poses a serious threat to Sudan, causing water shortages, crop failures, hunger, and conflict. The relationships between Indo-Pacific teleconnections and drought events in Sudan are examined based on the Standardized Precipitation Index (SPI), anomalies, Empirical Orthogonal Function (EOF), correlation, composite analysis, sequential Mann–Kendall test, and MK-trend test during the period of 1993–2022. The results of the SPI-1 values indicate that the extreme drought in Sudan in 2004 was an exceptional case that affected the entire region, with an SPI-1 value of −2 indicating extremely dry conditions. In addition, Sudan experienced moderate to severe drought conditions for several years (1993, 2002, 2008, 2009 and 2015). The Empirical Orthogonal Function showed that the first EOF mode (42.2%) was the dominant variability mode and had positive loading over most of the country, indicating consistent rainfall variation in the central, eastern, and western regions. Correlation analysis showed a strong significant relationship between June–September rainfall and Indian Ocean sea surface temperature (SST) (r ≤ 0.5). Furthermore, a weak positive influence of the Indian Ocean Dipole (IOD) on JJAS precipitation was observed (r ≤ 0.14). Various time lags in the range of ±12 months were examined, with the highest correlation (0.6) found at 9 month among the time lags of ±12 months. This study contributes to a better understanding of drought dynamics and provides essential information for effective drought management in Sudan. Further research is needed to explore the specific mechanisms driving these interactions and to develop tailored strategies to mitigate the impacts of drought events in the future. [ABSTRACT FROM AUTHOR]

The article discusses the potential impact of the 2024 Olympics and Paralympic Games in Paris on the risk of dengue outbreaks in the region. It highlights the rise in dengue cases globally in 2024 and the presence of Aedes albopictus mosquitoes capable of transmitting dengue, chikungunya, and Zika viruses in mainland France. The article emphasizes the importance of surveillance, vector-control measures, and healthcare provider awareness to prevent and manage potential dengue outbreaks during and after the Olympics. Additionally, it mentions the lack of antiviral treatment for dengue and the licensing of a live-attenuated tetravalent dengue vaccine for consideration in France. [Extracted from the article]

Downscaling global climate models (GCMs) provides crucial high-resolution data needed for informed decision-making at regional scales. However, there is no uniform approach to select the most suitable GCMs. Over Southeast Asia (SEA), observations are sparse and have large uncertainties, complicating GCM selection especially for rainfall. To guide this selection, we apply a standardised benchmarking framework to select CMIP6 GCMs for dynamical downscaling over SEA, addressing current observational limitations. This framework identifies fit-for-purpose models through a two-step process: (a) selecting models that meet minimum performance requirements in simulating the fundamental characteristics of rainfall (e.g. bias, spatial pattern, annual cycle and trend) and (b) selecting models from (a) to further assess whether key precipitation drivers (monsoon) and teleconnections from modes of variability are captured, i.e. the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). GCMs generally exhibit wet biases, particularly over the complex terrain of the Maritime Continent. Evaluations from the first step identify 19 out of 32 GCMs that meet our minimum performance expectations in simulating rainfall. These models also consistently capture atmospheric circulations and teleconnections with modes of variability over the region but overestimate their strength. Ultimately, we identify eight GCMs meeting our performance expectations. There are obvious, high-performing GCMs from allied modelling groups, highlighting the dependency of the subset of models identified from the framework. Therefore, further tests of model independence, data availability and future climate change spread are conducted, resulting in a final subset of two independent models that align with our a priori expectations for downscaling over the Coordinated Regional Climate Downscaling Experiment –Southeast Asia (CORDEX-SEA). [ABSTRACT FROM AUTHOR]

Using monthly data from 19 meteorological stations in Guangxi Zhuang Autonomous region from 1961 to 2020, this study calculated the standardized precipitation evapotranspiration index (SPEI) based on the Penman-Monteith evapotranspiration model (SPEI_PM). The temporal and spatial variation of meteorological drought were analyzed via linear tendency estimation, and Mann-Kendall trend test. The correlation between El Niño-Southern Oscillation (ENSO) and meteorological drought in Guangxi was also explored by cross-correlation function, cross wavelet transform and wavelet coherence. The values for summer, autumn, and annual SPEI_PM from 1961 to 2020 exhibited a significant linear trend of increasing wetness over time. Annual and seasonal droughts throughout the region were predominately mild and moderate, with less frequent severe and extreme droughts. Spring droughts were concentrated in the central part of the region, summer droughts in the southwest, autumn droughts in the southeast and northeast, and winter droughts spread throughout the region. Annual droughts were concentrated in the northeast. The rate of drought occurrence as measured by the stations in Guangxi exhibited a distinctly chronological character. Large-scale droughts (especially severe and extreme droughts) across the entire region occurred most often in the 1960s, 1970s, and 2000s. The impact of ENSO on the meteorological drought in Guangxi was characterized by spatial heterogeneity. Correlation between the ocean Niño index (ONI) and meteorological drought was highest in the northeast and southeast, as well as the northwest. There was no significant correlation between drought and ONI in coastal areas and most southwestern parts of the region. As a typical example from meteorological stations in northeastern Guangxi, SPEI-3 and ONI at the Guilin Meteorological station showed interannual oscillation cycles of 16-48 months in the period 1962-1976, and 12-64 months in the period 1990-2019. These results can serve as a useful reference for future drought forecasting and assessment in Guangxi. [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]

This study investigates the relationship between sea surface temperature (SST) anomalies in the subtropical Atlantic Ocean, as represented by the Southern Atlantic subtropical dipole (SASD), and SST anomalies in the tropical Pacific Ocean, identified by the El Niño‐Southern Oscillation (ENSO). Contrary to the previously held notion of a weak relationship between SASD and ENSO as suggested by earlier literature, our analysis reveals a substantial inverse correlation between the two. This correlation exhibits significant multi‐decadal variability, which has notably intensified over the most recent two decades compared with the preceding two decades. This intensification in the SASD–ENSO inverse correlation may be attributed to the shift in ENSO regime from predominance of eastern Pacific El Niño to central Pacific El Niño events around the turn of the century. This transition triggers wavetrains that propagate along different paths, consequently influencing the South Atlantic subtropical high and inducing alterations in anomalous SST patterns in the subtropical Atlantic Ocean. These findings advance our comprehension of the interactions between South Atlantic and Pacific SST variations, which strongly influence rainfall patterns, particularly in South America and southern Africa. Understanding such teleconnection holds promise for improving sub‐seasonal to seasonal precipitation predictions in these regions. [ABSTRACT FROM AUTHOR]

The Arctic warming around the Barents and Kara Sea frequently coincides with the Eurasian cooling winters, which is referred to as the warm Arctic-cold Eurasia (WACE) pattern. We here show that the WACE pattern during late winter (January-March) is closely associated with the tropical El Niño-Southern Oscillation but with a striking asymmetric linkage. In general, La Niña events are accompanied with an anomalous high-pressure system over Eurasia, facilitating the formation of the positive WACE pattern. However, a weak connection is detected between the El Niño and WACE pattern. This asymmetric influence of El Niño-Southern Oscillation (ENSO) on Eurasian circulation and surface air temperature can be attributed to the nonlinearity in its modulation on planetary waves and the spatial structure of stratospheric polar vortex during the warm and cold phases. During La Niña winters, the height anomalies over Eurasia tend to prevail in the troposphere due to an enhancement in the wave-1 planetary wave in the middle and low layers, in contrast to El Niño years with height anomalies more confined to the upper stratosphere. The identified linkage between La Niña and the WACE pattern provides a potential predictability source of cold winters over Eurasia on seasonal-to-interannual timescales. [ABSTRACT FROM AUTHOR]

Previous study has revealed the possible linear superposition of the El Niño-Southern Oscillation (ENSO) and Quasi-Biennial Oscillation (QBO)'s impacts on the northern winter stratosphere. This study first assesses the reproducibility of stratospheric ENSO and QBO teleconnections by 18 models able of producing QBO from the Coupled Model Intercomparison Project Phase (CMIP)-5 and CMIP6. Based on different teleconnection indices, high-skill models are adopted to reexamine the extratropical response to four ENSO-QBO configurations (El Niño-QBO easterly (EQBO), El Niño-QBO westerly (WQBO), La Niña-QBO easterly, and La Niña-QBO westerly). The modelling evidence validates that the stratospheric ENSO (QBO) signal can be separated by selecting major events based on the corresponding index and subtracting the QBO (ENSO) signal from model outputs through the regression method. The composite stratospheric response to a specific ENSO-QBO configuration is almost identical to the summation of impacts of individual QBO and ENSO, which validates the linearity. This study offers novel model evidence that stratospheric ENSO and QBO's teleconnections exhibit strong linearity in the northern winter. This linearity also exists in the troposphere to some degree. During the composite compound El Niño-EQBO conditions, the stratospheric polar vortex (SPV) weakens and is warmer, and its strengthening and cold anomalies also enlarge for the composite compound La Niña-WQBO conditions due to their cooperative amplification of signals by both QBO and ENSO. In contrary, the sign of the composite polar stratospheric total response is mainly determined by the QBO phase in both El Niño-WQBO and La Niña-EQBO composites. [ABSTRACT FROM AUTHOR]

Predictability barriers (PBs) significantly limit the prediction skill of the El Niño-Southern Oscillation (ENSO). The EP-El Niño predictions often encounter the impact of the spring PB, while the CP-El Niño predictions usually have PB phenomenon in summer. Using a data analysis approach for predictability dynamics and the pre-industrial control runs from the CCSM4 model outputs, the study explores the PB mechanism for EP- and CP-El Niño by tracing the evolution of initial errors. It is found that the significant spring PB for EP-El Niño and the notable summer PB for CP-El Niño often occur during the transition period from warm to cold phase of the initial sea surface temperature (SST) error evolution in the east-central tropical Pacific; however, there still exist respective initial errors that have specific spatial patterns leading to summer PB for EP-El Niño and spring PB for CP-El Niño. A comparison is made among the initial errors causing PBs for the two types of El Niño, and the results show that the initial errors resulting in the summer PB of CP-El Niño events tend to have more positive SST errors than those causing the spring PB for EP-El Niño in both the tropics and the Victoria mode (VM) region in the Northeast Pacific. These particular positive characteristics of the initial errors causing the summer PB pose a role that hinders the dissipation of the tropical Pacific positive SST errors and thus delay the spring transition phase of SST error, consequently triggering the occurrence of the summer PB for CP-El Niño. The role of the VM mode on SST in the tropical Pacific is inextricably linked to CP-El Niño formation and also sheds light on why the CP-El Niño tends to occur PB in summer. These findings provide a theoretical basis for advancing forecasting skills of El Niño diversity. [ABSTRACT FROM AUTHOR]

The North Pacific Oscillation (NPO) is an important intrinsic atmospheric pattern over the North Pacific. Observations have shown that the boreal winter NPO is a crucial precursor to the El Niño-Southern Oscillation (ENSO), with many ENSO events being preceded by the NPO. It is therefore imperative to assess the ability of current coupled climate models to reproduce the relationship between winter NPO and the subsequent winter ENSO. Previous studies have shown that most coupled climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) underestimate the influence of winter NPO on the subsequent winter ENSO. Simulations from CMIP6, representing the latest generation of climate models, are now available. This study shows a remarkable improvement of the CMIP6 models in simulating the influence of winter NPO on the subsequent ENSO development compared to the CMIP5 models. This improvement is due to the improved air-sea interaction over the subtropical North Pacific in CMIP6. The enhanced air-sea interaction over the subtropical North Pacific promotes the equatorward propagation of the NPO-induced wind and SST anomalies, resulting in enhanced surface zonal wind anomalies over the tropical western Pacific, which further exert a stronger influence on the subsequent winter ENSO development by triggering the tropical Bjerknes positive air-sea interaction. The enhanced subtropical air-sea interaction is thought to be related to a southward shift of the North Pacific intertropical convergence zone in CMIP6 compared to CMIP5. [ABSTRACT FROM AUTHOR]

Skill in predicting monthly mean daily maximum air temperature (MonTmax) over India during the pre-monsoon months (March to May) at lead times of 1–3 months by the Scale Interaction Experiment-Frontier Research Center for Global Change Version 2 (SINTEX-F2) model was evaluated. Analysis revealed that MonTmax in April over northwest and south India could be skillfully predicted by the model with a two-month lead time. The model predictions could capture most of the extreme MonTmax events over the two regions. Analysis of the extreme events in April in La Niña and El Niño years shows that the anomalous Matsuno-Gill atmospheric response to the precipitation anomalies over the northwest Pacific plays a crucial role in enhancing MonTmax anomalies over India. In the El Niño-Southern Oscillation (ENSO) neutral years and in some ENSO years with sparse precipitation anomalies over the northwest and central Pacific, the atmospheric waves from higher latitudes play a role in enhancing MonTmax anomalies over northwest India. The SINTEX-F2 model could capture the processes realistically with minimal bias. [ABSTRACT FROM AUTHOR]

The Indochina Peninsula, located between China and the South Asian subcontinent, serves as a convergence zone for the South Asian monsoon, the East Asian monsoon, and the South China Sea monsoon. Our study reveals that the interannual variability of spring near-surface temperature in the Indochina Peninsula is influenced by the westward extension of the western North Pacific subtropical high (WNPSH). Specifically, the westward extension of the WNPSH leads to a decrease in the low cloud cover over the Indochina Peninsula, resulting in radiation warming and thus an increase in the near-surface temperature. Furthermore, this westward extension of the latter is modulated synergistically by El Niño and the Aleutian Low. El Niño reduces rainfall near the Philippine Sea by weakening the Walker circulation, which acts as a cooling forcing and triggers an anticyclonic anomaly on its northwest side. This contributes to the westward motion of the WNPSH. In addition, the Aleutian Low promotes this westward shift of the WNPSH through a southwesterly flow at its periphery. Further results indicate that there is an 87.5% probability for the WNPSH to move westward with a synergistic modulation by El Niño and the Aleutian Low, compared to 50% without such modulation. Based on these findings, we have developed a prediction model for predicting potential (westernmost point of the WNPSH) of spring near-surface temperature in the Indochina Peninsula using January Niño3.4 index and Aleutian Low index. The correlation coefficient between hindcasting potential during spring from 2014 to 2023 using this model and observations is 0.67. [ABSTRACT FROM AUTHOR]

This study compares the physical processes responsible for the heavy and light rain variations from the perspective of spring precipitation over Southern China. The results indicate that, heavy rain variation has a closer connection with the western North Pacific anticyclone. Intensified western North Pacific anticyclone and associated warm and humid air transport, coupled with intensified East Asian subtropical jet, favor significant moisture convergence and enhanced convective feedback over the key region, which causes increased heavy rain rather than light rain over there. In comparison, light rain variation shows a close relationship with the anomalous low over Lake Balkhash, which causes lower-tropospheric cyclone over the key region. On the one hand, anomalous cyclone favors lower-tropospheric cooling; concurred with cyclone-induced increased moisture, the lower-tropospheric relative humidity increases over there. On the other hand, the lower-tropospheric cooling center shifts northward with height and causes enhanced atmospheric baroclinity over there. Such atmospheric conditions are conducive to the occurrence of low cloud and more light rain. In addition, intensified East Asian subtropical jet associated with Lake Balkhash anomalous low also provides favorable dynamic lifting condition. Moreover, heavy and light rain variations are more related to El Niño-Southern Oscillation and North Atlantic horseshoe sea surface temperature in preceding winter, respectively. In addition, heavy rain shows a closer relationship with total precipitation amount variation, whereas light rain is more related to extreme consecutive dry days variation. [ABSTRACT FROM AUTHOR]

Due to the less fluctuating environment in the early Holocene (10–8 ka BP) than in the late Holocene (2 ka BP to present), the relationship between EI Nin ̃o-Southern Oscillation (ENSO) and the Australian summer monsoon (AUSM) may be different from that in the late Holocene. But, the questions that how and why the relationship would change remain unknown. In this study, the transient climate simulations over the past 21,000 year (TraCE-21) are analyzed to address these questions. The model can reproduce the negative correlation relationship observed between the ENSO and AUSM. Compared with those in the early Holocene, the precipitation anomalies over the east of NA have shrunk by 5 degrees in the late Holocene. However, from the early to late Holocene, ENSO has significantly intensified by about 30%. Moreover, the maximum sea surface temperature anomalies (SSTAs) have shifted from the eastern to central tropical Pacific, thereby changing the ENSO teleconnection. The central tropical Pacific SSTAs in the late Holocene enhance the AUSM circulation, whereas the eastern tropical Pacific SSTAs in the early Holocene pose nonsignificant impacts on the AUSM. As such, the amplification and structural change of ENSO have altered the AUSM's spatial pattern and the AUSM-ENSO relationship in the Holocene. The results reveal how the AUSM may respond to ENSO in the past and shed light on understanding the future change of the ENSO-AUSM relationship and associated extreme climatic events. [ABSTRACT FROM AUTHOR]

As the primary interannual signal of variability in the tropical ocean-atmosphere interaction, the El Niño-Southern Oscillation has a considerable impact on tropical cyclone (TC) activity over the western North Pacific (WNP). Both 2018 and 2021 were La Niña decay years, but TC activity over the WNP during the two summers (June–August) showed notable differences. In 2018, summer TC activity was unusually high with a total of 18 TCs, and the region of TC genesis was mainly in the central and eastern WNP. In contrast, only 9 TCs were generated in summer 2021, and the region of TC genesis was primarily in the western WNP. By comparing the characteristics of the large-scale environmental conditions over the regions of TC genesis, the thermal factors of the tropical oceans, and the activity of the Madden-Julian Oscillation (MJO), this study revealed the possible causes for the marked differences in TC genesis over the WNP during the two summers, which both had a similar background of La Niña decay. The Indian Ocean Basin Mode (IOBM) transitioned of a cold anomaly in the winter of 2017/2018 and persisted until summer 2018. At the same time, the Pacific Meridional Mode (PMM) maintained a positive phase, leading to eastward and northward displacement of the Western Pacific Subtropical High in summer, and eastward extension of the tropical monsoon trough, which presented conditions conducive to TC genesis over the Northwest Pacific. Moreover, the days when the MJO stagnated in phases 5 and 6 in the summer of 2018 increased by approximately 150% relative to climatological state, providing dynamic conditions favorable for TC formation. In 2021, the IOBM quickly turned to a warm anomaly in March and persisted until summer, whereas the PMM became a negative phase in January and remained so until summer. At the same time, the MJO stagnated in phases 2 and 3 for up to 47 days, with the center of convection located over the western Maritime Continent, producing conditions unconducive to TC genesis over the Northwest Pacific. Thus, despite being under a similar background of La Niña decaying year, the distinct evolutions of the IOBM, PMM, and MJO in spring and summer of 2018 and 2021 were the main causes of the notable differences in TC activity over the WNP during these two summers, and the anomalies in IOBM and MJO contributed more significantly than those of the PMM. [ABSTRACT FROM AUTHOR]

Under global warming, understanding the long-term variation in different types of heatwaves is vital for China's preparedness against escalating heat stress. This study investigates dry and wet heatwave shifts in eastern China over recent decades. Spatial trend analysis displays pronounced warming in inland midlatitudes and the Yangtze River Valley, with increased humidity in coastal regions. EOF results indicate intensifying dry heatwaves in northern China, while the Yangtze River Valley sees more frequent dry heatwaves. On the other hand, Indochina and regions north of 25°N also experience intensified wet heatwaves, corresponding to regional humidity increases. Composite analysis is conducted based on different situations: strong, frequent dry or wet heatwaves. Strong dry heatwaves are influenced by anticyclonic circulations over northern China, accompanied by warming SST anomalies around the coastal midlatitudes of the western North Pacific (WNP). Frequent dry heatwaves are related to strong subsidence along with a strengthened subtropical high over the WNP. Strong and frequent wet heatwaves show an intensified Okhotsk high at higher latitudes in the lower troposphere, and a negative circumglobal teleconnection wave train pattern in the upper troposphere. Decaying El Niño SST patterns are observed in two kinds of wet heatwave and frequent dry heatwave years. Risk analysis indicates that El Niño events heighten the likelihood of these heatwaves in regions most at risk. As global warming continues, adapting and implementing mitigation strategies toward extreme heatwaves becomes crucial, especially for the aforementioned regions under significant heat stress. [ABSTRACT FROM AUTHOR]

Besides the rapid retreating trend of Arctic sea-ice extent (SIE), this study found the most outstanding low-frequency variation of SIE to be a 4–6-year periodic variation. Using a clustering analysis algorithm, the SIE in most ice-covered regions was clustered into two special regions: Region-1 around the Barents Sea and Region-2 around the Canadian Basin, which were located on either side of the Arctic Transpolar Drift. Clear 4–6-year periodic variation in these two regions was identified using a novel method called "running linear fitting algorithm". The rate of temporal variation of the Arctic SIE was related to three driving factors: the regional air temperature, the sea-ice areal flux across the Arctic Transpolar Drift, and the divergence of sea-ice drift. The 4–6-year periodic variation was found to have always been present since 1979, but the SIE responded to different factors under heavy and light ice conditions divided by the year 2005. The joint contribution of the three factors to SIE variation exceeded 83% and 59% in the two regions, respectively, remarkably reflecting their dynamic mechanism. It is proven that the process of El Niño–Southern Oscillation (ENSO) is closely associated with the three factors, being the fundamental source of the 4–6-year periodic variations of Arctic SIE. [ABSTRACT FROM AUTHOR]

The Pacific meridional mode (PMM) is one of the dominant coupled modes in the northeastern tropical Pacific (NETP), characterized by strip-like sea surface temperature (SST) anomalies spanning from Baja California to the central equatorial Pacific. While the majority of the El Niño events follow a positive PMM, only a few La Niña events are preceded by a negative PMM. Such an asymmetric activity of PMM before the onset of El Niño–Southern Oscillation (ENSO) was previously attributed to the inherent nonlinear response of the wind–evaporation–SST (WES) feedback to trade winds in the NETP. Through data analysis and coupled model experiments, we pointed out that PMM is in fact a highly symmetric phenomenon, and the asymmetry of PMM before the ENSO onset thus must be associated with ENSO. On the one hand, the nonlinear response of deep convection over the equator to symmetric ENSO forcing in the central equatorial Pacific permits a stronger Pacific–North America (PNA) pattern in El Niño years than in La Niña years. On the other hand, since the majority of La Niña events are preceded by a sharp decay of an El Niño, the warm equatorial SST anomalies associated with the preceding El Niño provide another source to trigger PNA before the La Niña onset. The two mechanisms modulate the trade winds and heat fluxes in NETP more heavily before the La Niña onset than the El Niño onset and equally contribute to PMM asymmetry before the ENSO onset. [ABSTRACT FROM AUTHOR]

The zonal wavenumber-5 circumglobal teleconnection (CGT) pattern is one of the most critical atmospheric teleconnection patterns during boreal summer over the Northern Hemisphere (NH). CGT can exert significant climatic impact across NH including Europe, East Asia, and North America, but how reliable coupled climate models simulate the characteristics of CGT is poorly understood. Here, 20 coupled models with their respective versions in phase 5 of the Coupled Model Intercomparison Project (CMIP5) and CMIP6 are selected to evaluate their performance on CGT simulation. We find that while both CMIP5 and CMIP6 models are able to capture the basic features of CGT in multimodel mean (MMM), there are large intermodel discrepancies in the simulation of CGT pattern among CMIP5 and CMIP6 models. High-skill models exhibit strong action center over west-central Asia, coinciding with the pattern derived from reanalysis, while the corresponding action center in low-skill models is weaker. Further analyses demonstrate that high-skill models are capable of simulating more realistic Indian summer monsoon (ISM) precipitation anomalies related to CGT. The resultant anomalous upper-tropospheric divergence over west-central Asia, acting as a Rossby wave source, can therefore excite the abovementioned action center. This high- and low-skill model difference on CGT–ISM relationship is consistent in both CMIP5 and CMIP6. It is also found that high-skill models tend to simulate more realistic CGT–ENSO relationship. The relationship between simulation skills of CGT–ENSO correlation and CGT spatial pattern is attributed to the remote impact of ENSO on CGT wave train through affecting ISM precipitation anomalies. [ABSTRACT FROM AUTHOR]

Numerous studies focus on the impacts of ENSO diversity on tropical cyclone (TC) activities in the western North Pacific (WNP). In recent years, there is a growing threat of landfalling and northward-moving TCs in East Asia, accompanying an increase in central Pacific (CP) El Niño. Here, we aim to discover variations in landfalling TCs during various types of CP El Niño (CP-I and CP-II El Niño). It is found that significant changes in landfalling and going northward TCs over East Asia north 20°N are modulated by CP-I El Niño. During CP-I El Niño, TCs tend to landfall more often over the mainland of China with longer duration, moving distance, and stronger power dissipation index (PDI) after landfall and increased TC-induced rainfall, due to favorable conditions (beneficial steering flow, weak vertical wind shear, increased specific humidity, increased soil moisture, and temperature), especially significant over the northeastern part. The situation over the mainland of China is reversed during eastern Pacific (EP) El Niño and CP-II El Niño, with a significant decrease in the characteristics with corresponding unfavorable environments. Over the Korean Peninsula and Japan, the frequency of TC landfalls, as well as the duration and the moving distance after landfall, exhibits greater levels during CP-I and CP-II El Niño than during EP El Niño due to favorable steering flow, and thus, TC-induced rainfall enhances correspondingly. Regarding the PDI over the Korean Peninsula and Japan, it remains relatively consistent across all El Niño types. However, a notable increase in the PDI during EP El Niño could be attributed to the higher intensity of TCs prior to landfall. [ABSTRACT FROM AUTHOR]

As a key dynamic element of the Bjerknes feedback mechanism, the thermocline effect (TE) is critically important to El Niño modeling. In this study, the potential influence of TE‐related parametric uncertainties on El Niño is investigated using the conditional nonlinear optimal parametric perturbation (CNOP) method based on an intermediate coupled model (ICM). The optimal perturbation of the TE‐related parameter (OTEP), which substantially affects El Niño simulations, is estimated through the CNOP approach. Results reveal that the El Niño simulation is highly sensitive to the TE uncertainty in the eastern equatorial Pacific, with OTEP‐induced simulation errors demonstrating an El Niño‐like growth trend. On one hand, as indicated by the simulated El Niño intensity, the uncertainty in the TE in the eastern region can easily affect the strength of the Bjerknes feedback‐related thermocline effect and atmospheric circulation. On the other hand, the enhanced TE is highly favored to accelerate the growth of the SST error due to the air–sea interaction, thus severely affecting the El Niño simulations. Therefore, adequately representing the TE in the equatorial eastern Pacific is emphasized for effectively improving El Niño simulations. Plain Language Summary: Thermocline effect (TE) uncertainty seriously challenges numerous climate models. Focusing on the TE‐related parameter in an intermediate coupled model, this study quantitatively examines the impact of the TE on El Niño simulations. The spatial structure of the TE‐related parameters that cause the largest simulation errors is determined by employing an optimization algorithm (conditional nonlinear optimal parametric perturbation). Subsequently, a systematic analysis of the error scenarios resulting from these optimal TE‐related parameters is conducted with their underlying mechanisms being explored. Results indicate that the uncertainties in the TE in the eastern tropical Pacific tend to alter the intensity of the positive Bjerknes feedback, leading to considerable errors in El Niño simulations. Furthermore, these simulation errors are intensified by air–sea interactions. This study provides vital theoretical insights for augmenting the precision of ENSO predictions. Key Points: El Niño simulation is sensitive to the model uncertainty in the thermocline effect (TE) in the eastern equatorial PacificThe TE uncertainty‐related effects on vertical advection and Kelvin wave act to amplify El Niño warming, thus causing large simulation errorsThe simulation error in El Niño due to TE uncertainty is further increased by air–sea interaction (more than 30%) [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs), extreme warm ocean temperature events, greatly impact marine ecosystems. While most MHW studies in the South China Sea (SCS) focus on the sea surface, subsurface characteristics remain less explored. This study uses high‐resolution (1/12°) ocean reanalysis data sets to assess MHW properties with depth in the SCS from 1993 to 2022. We find that MHW intensities are typically stronger at subsurface levels (30–150 m) than at the surface, with significant spatial variations. The vertical structures of MHW maximum and cumulative intensities peak between 70 and 100 m with 2.7°C and 63°C days, respectively; MHW annual days and duration increase gradually from 10 to 2,000 m with duration peaks at 2,000 m (∼60 days), four times longer than that at the surface. The SCS experienced two major periods of extensive El Niño‐related subsurface MHWs from 1997 to 2002 and 2008 to 2014, with MHWs reaching depths of 150 m and covering 70% of the upper 40 m. Strong El Niño events strengthen the western Pacific subtropical high, reducing summer monsoon winds, weakening coastal upwelling east of Vietnam, and increasing water temperatures. Regions of elevated eddy kinetic energy in the SCS suggest that significant mesoscale eddy activities are situated east of Vietnam. In addition, notable eddy heat transport was observed in the above region and west of the Luzon Strait in the upper 1,000 m. This may help to explain the high maximum and cumulative intensities of MHWs exceeding 100 m in the northern SCS. Plain Language Summary: Marine heatwaves (MHWs) have caused significant biological and socioecological impacts around the globe due to accelerated ocean warming. Most MHW studies have focused primarily on sea surface temperature extremes, while the subsurface impacts of MHWs have yet to be evaluated. In this study, we use high‐resolution (1/12°) ocean reanalysis data sets to estimate the statistical properties and potential mechanisms of MHWs from the surface to 2,000 m in the South China Sea (SCS) from 1993 to 2022. The results show that the maximum and cumulative intensities of MHWs are typically more intense in the subsurface at 30–150 m with significant spatial variations and that their annual days and duration increase with depth. Similarly, the vertical structures of maximum and cumulative intensities rapidly become strongest at depths between 70 and 100 m, reaching a maximum at 2.7°C and 63°C days, respectively. The SCS has experienced two major periods of widespread and persistent El Niño‐related subsurface MHWs, with the deepest reaching 150 m and covering 70% of the upper 40 m. Mechanistically, atmospheric circulation and ocean mesoscale eddy activity contribute to the intensification of subsurface MHWs in the SCS. Key Points: The maximum and cumulative intensities of marine heatwaves (MHWs) are significantly greater at the subsurfaceMHWs regularly extend into the deep ocean during the strengthened western Pacific subtropical high driven by strong El Niño eventsOcean eddy heat transport may be responsible for high‐intensity MHWs below 100 m in the northern South China Sea [ABSTRACT FROM AUTHOR]

The Solomon Sea is a major contributor to (a) the volume transport into the Equatorial Undercurrent and (b) the associated heat transport, which has an order one effect on interannual temperature variability on the equator according to previous work. The narrow western boundary current (New Guinea Coastal Undercurrent, NGCU) merges with the broad, shallow North Vanuatu Jet within 100 km of the southern entry to the sea, which implies mixing. Existing estimates from observations suggest mixing is larger than in models with different mixing parameterizations, which produce disparate properties of these exiting waters. Here, we use sustained underwater glider measurements across the Solomon Sea from 2007 to 2020 to examine the spatial variability of mixing estimates and internal waves. We estimate diffusivity via a finescale parameterization using the vertical strain of isopycnal displacements from internal waves. A typical accuracy of this parameterization when compared to turbulence measurements is within a factor of 2–3. Our results and previous observations in this area agree within this factor. Our main results are: (a) vertical diffusivity estimates are about 10−4 ${10}^{-4}$ m2 ${\mathrm{m}}^{2}$ s−1 ${\mathrm{s}}^{-1}$ on the inshore, anticyclonic side of the NGCU, which are 10–100 times higher than offshore and (b) elevated near‐inertial internal wave (NIW) amplitudes are also found inshore. Taken together, these results suggest trapping of NIW by the anticyclonic vorticity of the NGCU leads to the elevated mixing within 100 km of the entry to the Solomon Sea. Plain Language Summary: Two currents enter the Solomon Sea and merge within about 100 km, which implies mixing. The salinity change that occurs in this area indicates elevated mixing. This mixing contributes to the properties of waters exiting the sea, a major source of the Equatorial Undercurrent, which contributes to El Niño and other longer period variability on the equator. From 2007 to 2020 underwater gliders crossed the broad, shallow North Vanuatu Jet in the middle of the basin and the narrow boundary current on the western side of the basin (the New Guinea Coastal Undercurrent, NGCU). Internal gravity wave variability is measured by the vertical displacement of density surfaces and mixing is estimated based on measured vertical stretching and compressing between these density surfaces. This method is not actually measuring turbulence, but estimating it based on the energy in the measured internal waves. Our main result concerns the spatial pattern of the estimated mixing. Stronger internal gravity waves with frequencies near the inertial frequency (near‐inertial internal waves or NIW) are noted on the inshore side of the NGCU. Mixing is also elevated in this area, which suggests NIW are trapped there and provide an energy source for the mixing. Key Points: The subsurface salinity maximum erodes within 100 km of the southern entry to the Solomon Sea, which indicates mixingMixing estimates, vorticity, and near‐inertial energy are higher on the inshore, anticyclonic side of the western boundary currentNear‐inertial internal waves trapped by boundary current's anticyclonic vorticity appear to be the main energy source for the mixing [ABSTRACT FROM AUTHOR]

Satellite observations revealed two extremely low surface chlorophyll concentration (SCC) events with a warm sea surface temperature anomaly in the southeastern Arabian Sea (SEAS, 6°–15°N, 72°–77°E) during the summer (July–August–September) in 2015 and 2019. We find that the physical processes leading to these two similar low SCC events are remarkably different. The low SCC in the SEAS during summer 2019 is mainly related to the weakened upwelling and deepening of the thermocline depth due to the combined effects of the local wind anomalies and the arrival of westward‐propagating downwelling coastal Kelvin wave driven by easterly anomalies near the eastern Sri Lanka during an extreme positive Indian Ocean Dipole (IOD) event. In summer 2015, a weaker positive IOD‐induced easterly anomalies in the southern Bay of Bengal also drives downwelling coastal Kelvin waves westward, deepening the thermocline in the SEAS. But unlike that in summer 2019, the local wind stress curl anomalies in the SEAS during summer 2015 favors upwelling, which counteracts the downward motion of the coastal Kelvin waves, leading to weaker downward transport (one‐third of that in 2019). Meanwhile, the upper ocean layer in the SEAS experiences extreme warming during summer owing to the development of 2015/2016 super El Niño. This substantial warming enhances upper oceanic stratification, which results in weaker vertical mixing and reduces the SCC to an extremely low level despite the much weaker IOD strength in 2015. Plain Language Summary: Surface chlorophyll concentrations (SCC) in the ocean have important implications for marine fisheries and material cycling. Satellite observations show extremely negative anomalies in the SCC in the southeastern Arabian Sea (SEAS) during the summers of 2015 and 2019. Even though positive Indian Ocean Dipole (IOD) occurred in both years, the physical processes leading to the two similar low SCC events are remarkably different. In summer 2019, the local wind anomaly and the arrival of westward‐propagating downwelling coastal Kelvin wave weakens upwelling and deepens thermocline, which leads to the low‐SCC event. In summer 2015, a weaker positive IOD‐induced easterly anomaly in the southern Bay of Bengal also drives downwelling coastal Kelvin waves westward and deepens the thermocline in the SEAS. Meanwhile, the remote forcing of the 2015/2016 super El Niño weakens vertical mixing in the SEAS and further reduces the SCC. This study may help to further understand the response of the SCC in the SEAS to the diversities of IOD events. Key Points: Satellite observations indicate extremely negative anomalies of the surface chlorophyll concentration (SCC) in the southeastern Arabian Sea (SEAS) during the summers in 2015 and 2019The extremely negative SCC anomaly in the SEAS during summer 2019 was due to strong positive Indian Ocean Dipole‐induced local and remote wind anomaliesThe SEAS warming forced by the 2015/2016 super El Niño inhibited vertical mixing and reduced the SCC to a similar level as that in 2019 [ABSTRACT FROM AUTHOR]

Shoreline position (e.g., beach width) is a critical component of flooding and overtopping forecasts but difficult to predict accurately. We model beach width changes with a supervised machine learning (ML) approach informed by equilibrium principles. The time history of wave energy anomalies that force equilibrium models is used as an ML input feature. The sweeping simplifying equilibrium model assumptions relating beach width change to anomalies are replaced with data‐based ML results. Supervised learning regression methods including linear, support vector, decision trees, and ensemble regressors are tested. Observations for model training and testing includes weekly to quarterly beach elevation surveys spanning approximately 500 m alongshore and 8 years at two beaches, each supplemented with several months of ∼100 sub‐weekly surveys. These beaches, with different sediment types (sand vs. sand‐cobble mix), both widen in summer in response to the seasonal wave climate, in agreement with a generic equilibrium model. Differences in backshore erodability contribute to differing beach responses in the stormiest (El Niño) year that are reproduced by a simple extra trees regression model but not by the equilibrium model. With sufficiently extensive training data, the ML model outperforms equilibrium by providing flexibility and complexity in the response to wave forcing. The present ML and equilibrium models both fail to simulate a uniquely stunted beach recovery unlike other recoveries in the training data. Plain Language Summary: Beach elevation surveys are compared at two beaches in San Diego County. Both beaches narrow during winter as large wave events transport sand offshore and widen during summer as gentle waves move sand onshore. The seasonality of such beaches has been characterized by simple models that primarily rely on wave energy relative to an average state to predict beach width changes, known as equilibrium models. Here, we highlight some of the limitations of equilibrium models, such as a tendency to over predict winter erosion at a beach backed by non‐erodible infrastructure. We demonstrate that machine learning models, when trained with sufficient observations, can predict beach width changes more accurately than equilibrium models. Key Points: The Equilibrium‐informed extra tree (ET) regression machine learning model uses input features of only wave history, inspired by equilibrium conceptsWith sufficient training, ET outperforms a widely used equilibrium model [ABSTRACT FROM AUTHOR]

This study investigated the sociological dimensions informing public perceptions of water scarcity during the El Niño drought period in Colombia. We conducted this study in Santa Marta, Colombia, and surveyed 405 urban and rural residents to understand their perceptions of water scarcity, management, and the impacts of the El Niño phenomenon. The survey used a Likert scale to measure responses and employed a multivariate analysis of variance to analyze the data while considering factors such as location (urban versus rural) and gender. The study results indicated that urban residents often experience an irregular water supply all year, whereas most rural respondents noted a more consistent availability of water. The perception of water scarcity also differed notably between urban and rural areas due to their different historical and cultural experiences (habitus). Urban respondents mostly recognized the presence of water, while rural perspectives were less conclusive, likely influenced by their direct access to natural water sources. Participants across various demographics consistently reported that poor management by local, regional, and national governments contributes to the water scarcity crisis, highlighting the importance of improving communication about climate events like El Niño and water management to increase community engagement in public policies. Our research suggests that better understanding the social foundations of such perceptions using Bourdieu's concepts of social fields, habitus, and capital forms can significantly enhance water management strategies. [ABSTRACT FROM AUTHOR]

A surface layer (upper 20 m depth) heat budget analysis, derived from a hindcast regional-scale ocean modeling experiment, was employed to examine the underlying mechanisms behind the emergence of sea surface temperature anomalies (SSTA) in the Indonesian seas during El Niño events over the 1995–2019 course. Prior to the emergence of warm SSTA, which typically appeared following the mature phase of El Niño and lasted for almost a year, apparent anomalous heat accumulation occurred for at least 2–4 months and peaked in conjunction with the climatic event. Further examination revealed possible east–west distinct dynamics in the heat budget variations within the region during El Niño years. The anomalous heat accumulation in the western part of Indonesian seas (Java Sea) was predominantly caused by modulation in the surface net heat flux. Whereas in the eastern part (Banda Sea), the ocean circulation also exerted important influence in addition to the surface net heat flux. The ocean circulation in the eastern Indonesian seas notably contributed to moderate the effect of surface net heat flux during El Niño growth. Moreover, the same ocean circulation was responsible for prolonging the anomalous heat accumulation in the eastern Indonesian seas from mature to decay phase of the El Niño, ultimately resulted in warmer SSTA than that in the western part. The study conducted here provides additional insights on how the Indonesian seas responded to the El Niño and further reaffirms the idea that the climatic event results in anomalous warming across the Indonesian seas. [ABSTRACT FROM AUTHOR]

Global-mean surface temperature rapidly increased 0.29 ± 0.04 K from 2022 to 2023. Such a large interannual global warming spike is not unprecedented in the observational record, with a previous instance occurring in 1976–1977. However, why such large global warming spikes occur is unknown, and the rapid global warming of 2023 has led to concerns that it could have been externally driven. Here we show that climate models that are subject only to internal variability can generate such spikes, but they are an uncommon occurrence (p = 1.6 % ± 0.1 %). However, when a prolonged La Niña immediately precedes an El Niño in the simulations, as occurred in nature in 1976–1977 and 2022–2023, such spikes become much more common (p = 10.3 % ± 0.4 %). Furthermore, we find that nearly all simulated spikes (p = 88.5 % ± 0.3 %) are associated with El Niño occurring that year. Thus, our results underscore the importance of the El Niño–Southern Oscillation in driving the occurrence of global warming spikes such as the one in 2023, without needing to invoke anthropogenic forcing, such as changes in atmospheric concentrations of greenhouse gases or aerosols, as an explanation. [ABSTRACT FROM AUTHOR]

Water transparency, as indicated by the Secchi disk depth (Zsd), is a key parameter for assessing the quality of aquatic environments, reflecting the ability of light to penetrate through the water column. In the Tibetan Plateau (TP), where lakes are abundant yet remote and challenging to access, remote sensing techniques offer a promising approach for monitoring Zsd over large spatial scales. In this study, we used the semianalytical -based Zsd algorithm to study the temporal and spatial dynamics of water transparency over TP during the period from 2003 to 2022. The results show that the 173 lakes have a mean value of Zsd is 3.64 ± 2.4 m for long term, and generallywith the significantly increasing change trends in the past 20 years. In the central Tibetan Plateau (CTP) region, lake transparency showed a positive correlation with lake surface temperature (r = 0.73) and a negative correlation with precipitation (r = -0.54), highlighting the region's heightened sensitivity tometeorological changes compared to other areas. The spike inwater clarity observed in the CTP region may be linked to alterations in lake hydrodynamics driven by the extremely climate events (i.e., El Niño). These results indicated the importance of considering regional climatic factors when interpreting fluctuations in water transparency. [ABSTRACT FROM AUTHOR]

Current climate models suggested that Antarctic sea ice cover would decrease substantially under cumulative CO2 emission, but little is known whether large decrease in Antarctic sea ice can influence the occurrence of strong El Niño. Using time slice coupled and uncoupled model experiments, we show that in response to half reduction of Antarctic sea ice projected near the end of the 21st century, the frequency of strong El Niño would be increased by ~40%. It is contributed by enhanced thermocline, Ekman, and zonal advective positive feedbacks that are partly offset by enhanced thermodynamic damping. The strong warming and weakened westerly winds in the southeastern Pacific generate an anomalous Rossby wave propagating into the eastern subtropical and tropical Pacific, favoring stronger El Nino, and air-sea coupling and ocean feedbacks play a critical role in the teleconnection. Unexpectedly, compare to halved Antarctic sea ice, the ice-free Antarctic leads to a decrease in the frequency of strong El Niño, which is largely due to a substantial increase in thermodynamic damping. We also show that a large portion of the increase of strong El Niño events under greenhouse warming might be connected with Antarctic sea-ice loss, though increased greenhouse gas plays an important role. [ABSTRACT FROM AUTHOR]

The occurrence of extreme hot and dry summer conditions in the Pacific Northwest region of North America (PNW) has been known to be influenced by climate modes of variability such as the El Niño-Southern Oscillation and other variations in tropospheric circulation such as stationary waves and blocking. However, the extent to which the subseasonal remote tropical driver influences summer heat extremes and fire weather conditions across the PNW remains elusive. Our investigation reveals that the occurrence of heat extremes and associated fire-conducive weather conditions in the PNW is significantly heightened during the boreal summer intraseasonal oscillation (BSISO) phases 6-7, by ~50–120% relative to the seasonal probability. The promotion of these heat extremes is primarily attributed to the enhanced diabatic heating over the tropical central-to-eastern North Pacific, which generates a wave train traveling downstream toward North America, resulting in a prominent high-pressure system over the PNW. The ridge, subsequently, promotes surface warming over the region primarily through increased surface radiative heating and enhanced adiabatic warming. The results suggest a potential pathway to improving subseasonal-to-seasonal predictions of heatwaves and wildfire risks in the PNW by improving the representation of BSISO heating over the tropical-to-eastern North Pacific. [ABSTRACT FROM AUTHOR]

This paper uses time-varying smooth transition autoregressive model to investigate the asymmetric nature of El Niño Southern Oscillation (ENSO) —an exogenous climatic factor—with respect to the nonlinear dynamics of food prices in sub-Saharan Africa. Curating food price series from more than 1100 markets from 36 SSA countries, the study finds that ENSO (linearly or nonlinearly) affects roughly half of food prices considered, with most nonlinear models exhibiting strong asymmetric properties with shock-inflicted persistence. Moreover, in terms of the location of the burden of ENSO impact, I find a geographical and food product divide. Specifically, ENSO appears to be more efficacious on maize prices in Southern, Eastern, and some parts of Central Africa. Conversely, local rice, cassava, millet, and animal products are least affected. The policy implication of this dichotomy is that response to ENSO news should be subregion-specific rather than region-specific, depending on how the subregions absorb the shock. [ABSTRACT FROM AUTHOR]

The sensitivity of atmospheric CO2 growth rate to tropical temperature (T) has almost doubled between 1959 and 2011, a trend that has been linked to increasing drought in the tropics. However, T has declined since then. Understanding whether these variations in T reflect forced changes or internal climate variability in the carbon cycle is crucial for future climate projections. We show that doubling sensitivity events can arise in simulations by Earth system models with perturbed initial conditions but are likely explained by internal climate variability. We show that the doubling sensitivity event is associated with the occurrence of a few, but very strong, El Niño events, such as 1982/83 and 1997/98. Such extreme events result in concurrent carbon release by tropical and extratropical ecosystems, increasing the variance of the global land carbon sink and its apparent sensitivity to tropical temperature. Our results imply that the doubling sensitivity does not necessarily indicate a change in carbon cycle response to climate change. [ABSTRACT FROM AUTHOR]

The influence of El Niño‐Southern Oscillation (ENSO) on the North Tropical Atlantic (NTA) sea surface temperature (SST) is well‐documented in boreal spring, yet it manifests greater complexity in winter. Distinct from El Niño, La Niña has a statistically significant impact on winter NTA SST, which is primarily contributed by the re‐occurring (i.e., second and third years of multi‐year) La Niña events. Despite similar atmospheric forcing, prominent SST anomalies are observed in the NTA during the re‐occurring La Niña winters but not in the first‐year La Niña winters, mainly due to different initial states associated with previous tropical Pacific forcing. Targeted pacemaker experiments well reproduce the robust impacts of re‐occurring La Niña events on the wintertime NTA SST, highlighting the crucial impact of ENSO cycle complexity in its inter‐basin linkages. Plain Language Summary: The El Niño‐Southern Oscillation (ENSO) significantly influences the sea surface temperature (SST) in the North Tropical Atlantic (NTA), particularly as ENSO events decay during boreal spring. However, during winter when ENSO reaches its peak, the NTA SST anomalies exhibit strong uncertainty. While no marked SST anomalies are observed in the NTA during El Niño winters, prominent SST anomalies can often be found in the NTA during La Niña winters. The significant La Niña‐related SST anomalies in the NTA are primarily contributed by the second and third years of multi‐year La Niña events, rather than the first‐year La Niña events. The SST difference between the first‐year and re‐occurring La Niña winters can be attributed to the SST initial state in the NTA, which is related to the preceding forcing from the tropical Pacific. By incorporating this initial state, we can more accurately reconstruct the NTA SST anomalies during La Niña winters. Targeted pacemaker experiments corroborate the significant role of re‐occurring La Niña events in influencing wintertime NTA SST. Key Points: La Niña usually has stronger impacts on winter NTA SST than El Niño, primarily contributed by re‐occurring La Niña eventsDifferent NTA SST anomalies during the first‐year and re‐occurring La Niña can be well understood by considering the NTA initial stateTargeted pacemaker experiments confirm the important effect of re‐occurring La Niña on the NTA SST [ABSTRACT FROM AUTHOR]

Prior research extensively investigates the delayed influence of El Niño‐Southern Oscillation (ENSO) events on subsequent summer climates, with persistent sea surface temperature anomalies (SSTAs) in remote tropical oceans serving as crucial pathways. This study unveils a previously overlooked midlatitude pathway. During the developing winter, El Niño events induce basin‐scale cold SSTAs in the central North Pacific, which can persist into the following summer. These anomalies significantly influence early‐summer atmospheric circulation by enhancing atmospheric baroclinicity and transient eddy activities. Primarily driven by transient eddy vorticity forcing, an equivalent barotropic geopotential low anomaly emerges over the North Pacific. Enhanced by the southwesterly winds of the atmospheric low, tropical moisture is transported farther northeastward in the early summer, resulting in increased rainfall in the Pacific Northwest region. By elucidating this meridional pathway, our study advances the understanding of ENSO's delayed impacts and associated dynamical processes, in which the midlatitude oceanic feedbacks are emphasized. Plain Language Summary: The El Niño‐Southern Oscillation (ENSO) events are considered as a primary driver of climate anomalies. Even during their decaying phase, its impact on the Northern Hemisphere summer climate remains notable. This study delves into the intricate mechanisms underlying the delayed impacts of ENSO events on subsequent summer climates. While prior research has extensively explored the zonal pathways involving tropical Indian and Atlantic oceans, this study illuminates a previously overlooked meridional pathway. It reveals that El Niño events trigger significant cold sea surface temperature anomalies (SSTAs) in the North Pacific during their mature phase in winter, which persist into the following summer. These SSTAs wield substantial influence over early‐summer atmospheric circulation, fostering atmospheric baroclinicity and transient eddy activities. Consequently, an anomalous low‐pressure system emerges over the North Pacific in early summer, enhancing southwesterly winds and transporting tropical moisture farther northeastward. This moisture influx results in increased rainfall in the Pacific Northwest region. By elucidating this meridional pathway, the study advances our comprehension of ENSO's delayed impacts, highlighting the crucial role of midlatitude oceanic feedbacks. In essence, it demonstrates how ENSO events can influence North American climate anomalies during subsequent early summer, shedding light on a previously unrecognized pathway of ENSO's effect. Key Points: Cold central North Pacific sea surface temperature anomalies (SSTAs), initiated by El Niño events, can endure into the subsequent summerBy transient eddy forcing, these cold SSTAs induce a whole‐layer geopotential low anomaly over North Pacific in post‐El Niño early summerThus, northeastward moisture transport strengthens, boosting increased early‐summer rainfall in Pacific Northwest after El Niño events [ABSTRACT FROM AUTHOR]

Atmospheric variability associated with the winter North Pacific Oscillation (NPO), preceding El Niño‐Southern Oscillation (ENSO) events by about 1 year, is driven mainly by the tropical Pacific sea surface temperature (SST) anomalies but may also affect the subsequent ENSO. To isolate the latter, we conduct an idealized hindcast experiment using a climate model MIROC6, in which the NPO‐related surface heat flux and wind stress anomalies are overridden over the North Pacific. The ENSO evolution can be overall reproduced without the NPO forcing, confirming the predominant intrinsic predictability arising from the tropical coupled dynamics. However, the extratropical atmospheric forcing associated with the NPO, when it reaches three standard deviations, can enhance the ENSO development by about 29.6%, contrasting with limited effects of the moderate NPO forcing. La Niña events exhibit much less sensitivity to the NPO forcing compared to El Niño events, possibly due to asymmetric patterns of the simulated NPO. Plain Language Summary: The winter North Pacific Oscillation (NPO), manifesting as a meridional dipole structure in sea level pressure over the North Pacific, is suggested to play a role in the subsequent El Niño‐Southern Oscillation (ENSO) development. Recent studies demonstrate that the preceding winter NPO signal mainly originates from the tropical Pacific SST forcing, making it challenging to isolate its specific impact on ENSO. In this study, we design a series of "overriding" experiments to decouple the tropical and extratropical Pacific processes based on the MIROC6 model. It is found that the ENSO evolution can be reproduced when excluding the NPO forcing, suggesting that the ENSO events is primarily driven by internal dynamics within the tropics. While the moderate NPO forcing has minor effects on the ENSO events, the exceptionally strong NPO forcing can further amplify the ENSO development. This study underscores that while NPO‐related extratropical variabilities do affect ENSO, their impact, especially under moderate conditions, should not overshadow the intrinsic predictability from the tropics. Key Points: The El Niño‐Southern Oscillation (ENSO) development is primarily driven by internal dynamics within tropicsThe NPO forcing of the extreme rather than moderate amplitude can significantly amplify the ENSO developmentDevelopment of El Niño events are more sensitive to the NPO forcing compared to La Niña events [ABSTRACT FROM AUTHOR]

This study evaluates the capability of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models to simulate El Niño‐Southern Oscillation teleconnections in the Southern Hemisphere during austral summer. The wave trains from the tropical Pacific to the Amundsen Sea are underestimated and too far westward in CMIP6 simulations. However, Atmospheric Model Intercomparison Project Phase 6 (AMIP6) experiments well capture the observed location and amplitude of the teleconnection. El Niño and La Niña‐related tropical precipitation anomalies are underestimated in CMIP6 and have their maximum amplitude too far westward, while the precipitation responses in AMIP6 simulations are similar to those observed. The weaker precipitation response in CMIP6 likely arises from a cold bias in climatological‐mean SST, which reduces the sensitivity of precipitation to SST anomalies. Increased resolution in coupled experiments eradicates the westward bias in the El Niño and La Niña‐related circulation anomalies over the Amundsen Sea, but not their insufficient amplitude. Plain Language Summary: Abnormally warm and cold sea surface temperatures (SST) in the tropical Pacific during El Niño and La Niña events, respectively, generate atmospheric circulation anomalies that propagate across the Southern Hemisphere toward the Amundsen Sea, where they influence west Antarctic climate. In this study, we evaluate how well state‐of‐the‐art climate models simulate these El Niño and La Niña‐related teleconnections. We find that free‐running models simulate teleconnections that are too weak and too far westward. When models are provided with realistic SST however, they well simulate the teleconnection location and amplitude. The errors in free‐running models likely occur because the models are too cold in the tropical Pacific, and this reduces the sensitivity of simulated rainfall to SST anomalies; and the SST anomalies are too far westward. Increased ocean resolution eradicates the error in the location of the El Niño and La Niña teleconnections but does not substantially improve their strength. Key Points: CMIP6 models underestimate the intensity of observed ENSO teleconnection to the Amundsen Sea and simulate a westward bias in the wave trainExperiments prescribed with historical global SST and sea ice, closely match the location and strength of observed ENSO‐related wave trainIncreased ocean resolution eliminates the westward bias in the wave train responses to ENSO, but not their insufficient amplitudes [ABSTRACT FROM AUTHOR]

The interannual variation of the South China Sea (SCS) summer monsoon onset (SMO) may bring extreme weather and climate disasters in East Asia. However, its skillful forecast still remains challenging. This study investigates the intraseasonal ocean‐atmosphere interaction that affects the SCSSMO through diagnostic analysis and numerical experiments. It reveals that the cold sea surface temperature in the Southern SCS during winter (referred as cold tongue, CT) is the key pathway controlling the propagation of the 30–60 days intraseasonal oscillation (ISO) convective system from the Bay of Bengal (BOB) to the SCS. The CT variations affect the interannual variation of the SCSSMO. Specifically, the strong (weak) CT after the peak of La Niña (El Niño) years suppresses (enhances) the propagating ISO from the BOB to the SCS, resulting in a delayed (advanced) SCSSMO. This finding offers the new scientific insights for improving the forecasting of the SCSSMO. Plain Language Summary: The occurrence of a strong cold tongue (CT) in winter, commonly detected in the southern South China Sea (SCS) during La Niña decay years, plays a significant role in delaying the SCS summer monsoon onset (SCSSMO). It adversely affects the northeastward progression of the 30‐60‐day convective Intraseasonal Oscillation (ISO) from the equatorial Indian Ocean to the southern SCS. This interference leads to the delayed onset of the SCSSMO. It highlights the crucial influence of the CT sea surface temperatures (SST) on the linkage between Bay of Bengal and SCS at the intraseasonal scale, thus significantly impacting the timing of the SCSSMO. Key Points: The winter cold tongue in South China Sea (SCS) is a crucial oceanic precursor for the interannual variation of the SCS summer monsoon onset (SCSSMO)Strong cold tongue in the SCS can suppress the propagation of the 30‐60‐day intraseasonal oscillation into the SCSStrong SCS cold tongue during La Niña years tends to delay the SCSSMO [ABSTRACT FROM AUTHOR]

The Makassar Strait throughflow (MST) is the major component of the Indonesian Throughflow (ITF), transferring Pacific water into the Indian Ocean. In our previous study, we identified a new zonal pathway, a. k.a. the North Equatorial Subsurface Current (NESC), which carried equatorial water into the MST sub‐thermocline (>300 m) in the summer 2016 following the 2015/16 El Niño. We now show continued strong southward MST in the sub‐thermocline during the winter of 2016–2017, with salinity higher than that in the summer 2016, due to direct South Pacific water intrusion into the Sulawesi Sea. The origin of the intrusion is identified from the New Guinea Coastal Undercurrent (NGCUC) and from an anomalous westward flow along 3°N in the western equatorial Pacific. The identified interannual variability of the western Pacific Ocean circulation is particularly strong in the winter following super El Niño events. Plain Language Summary: The Indonesian Throughflow (ITF) transfers Pacific waters into the eastern Indian Ocean through the complex passages of the Maritime Continent, affecting the water properties and heat content in both oceans. The vertical structure of the ITF plays an important role in modulating the Indo‐Pacific Ocean heat content and climate. Understanding the Pacific water mass sources of the ITF and their variations is essential to understanding interocean heat and salt transports. The sub‐thermocline (>300 m) throughflow within the Indonesian Seas, has waters drawn from the relatively salty South Pacific thermocline. To date, the pathway of the South Pacific water into the ITF is not understood well. Here we present evidence showing a new pathway for high salinity South Pacific water flowing into the sub‐thermocline Makassar Strait directly after strong El Nino events, which may become more common in the future. This study helps to understand the importance of the South Pacific water in the variations of the Great Ocean Conveyer Belt and in biogeochemical processes with ecological impacts downstream of the ITF. Key Points: Strong anomalous southward flow with higher salinity in the winter of 2016–2017 was observed in the sub‐thermocline Makassar StraitThe high salinity is due to direct intrusion of South Pacific water from the western boundary current and an anomalous flow along 3 °NThe identified direct intrusion of South Pacific water into the Makassar Strait appears strong in the winter following a super El Niño [ABSTRACT FROM AUTHOR]

Heatwaves are projected to substantially increase at a global scale, exacerbating worldwide heat-related risks in the future. However, understanding future heterogeneous heatwave changes and their origins remains challenging. By analyzing the output of various climate models from the Coupled Model Intercomparison Project Phase 6, we found pronounced spatial disparity of projected heatwave increases in the Northern Hemisphere, even outstretching seven-fold inter-regional differences in extreme heatwave occurrences, attributed primarily to future changes in heat-dome-like circulations and soil moisture–temperature coupling. Specifically, we found that by the end of the 21st century, the modulations of combined Pacific El Niño and positive Pacific Meridional Mode on magnified heat-dome-like circulations would be translated into summertime hotspots over western Asia and western North America. Amplified soil moisture–temperature couplings then further aggravate the heatwave intensity over these two hotspots. This study provides support for formulating impact-based mitigation strategies and efficiently addressing the potential future risks of heatwaves. [ABSTRACT FROM AUTHOR]