Southern Oscillation Research Articles

Interannual variability of the South Equatorial Current in the southeast Indian Ocean associated with the El Niño-Southern Oscillation

Abstract Interannual variability of the South Equatorial Current (SEC) in the southeast Indian Ocean is investigated using AVISO and Global Ocean Reanalysis and Simulations (GLORYS) data from January 1993 to December 2022 and a 1.5-layer reduced-gravity model. Interannual variability of the SEC averaged over the upper 200 m in the southeast Indian Ocean is influenced by the El Niño-Southern Oscillation (ENSO). The SEC has a significant positive correlation with the Niño 3.4 index and lags the Niño 3.4 index by 12–15 months, with the SEC weakening (strengthening) significantly during the decaying years of El Niño (La Niña) events. Mechanistic studies suggest that during the developing years of El Niño (La Niña) events, the northward (southward) SLA pressure gradient between the negative (positive) SLA off Sumatra-Java coast and the positive (negative) SLA of SEC region (90°E–115°E, 9°S–13°S) strengthens (weakens) the SEC under geostrophic equilibrium. During the decaying years of El Niño (La Niña) events, the negative (positive) SLA in the tropical western Pacific Ocean propagates through the Maritime Continent to the SEC region. The SLA pressure gradient between the Sumatra-Java coast and the SEC region reverses to southward (northward). This induces an eastward (westward) geostrophic current anomaly under geostrophic equilibrium, significantly weakening (strengthening) the SEC. Local wind in the southeast Indian Ocean has a suppressive effect on the SLA propagated to this area. The results of the 1.5-layer reduced-gravity model verify these phenomena, and the westward-propagating SLA from the Maritime Continent induced by the Pacific wind plays a dominant role in the SLA variation in the SEC region from model experiment. This study can improve the understanding of the effects of ENSO processes on ocean circulation in the southeast Indian Ocean.

Spatial and Temporal Characterization of Near Space Temperature and Humidity and Their Driving Influences

Near space refers to the atmospheric region 20–100 km above Earth’s surface, encompassing the stratosphere, mesosphere, and part of the thermosphere. This region is susceptible to surface and upper atmospheric disturbances, and the atmospheric temperature and humidity profiles can finely characterize its complex environment. To analyze the relationship between changes in temperature and humidity profiles and natural activities, this study utilizes 18 years of temperature and water vapor data from the TIMED/SABER and AURA/MLS instruments to investigate the variations in temperature and humidity with altitude, time, and spatial distribution. In addition, multiple linear regression analysis is used to examine the impact mechanisms of solar activity, the El Niño–Southern Oscillation (ENSO), and the Quasi-Biennial Oscillation (QBO) on temperature and humidity. The results show that in the mid- and low-latitude regions, temperature and water vapor reach their maxima at an altitude of 50 km, with values of 265 K and 8–9 × 10⁻⁶ ppmv, respectively; the variation characteristics differ across latitudes and altitudes, with a clear annual cycle; the feedback effects of solar activity and the ENSO index on temperature and humidity in the 20–40 km atmospheric layer are significantly different. Among these factors, solar activity is the most significant influence on temperature and water vapor, with response coefficients of −0.2 to −0.16 K/sfu and 0.8 to 4 × 10⁻⁶ ppmv/sfu, respectively. Secondly, in the low-latitude stratospheric region, the temperature response to ENSO is approximately −1.5 K/MEI, while in the high-latitude region, a positive response of 3 K/MEI is observed. The response of water vapor to ENSO varies between −1 × 10⁻⁷ and −4 × 10−⁷ ppmv/sfu. In the low-latitude stratospheric region, the temperature and humidity responses to the QBO index exhibit significant differences, ranging from −1.8 to −0.6 K/10 m/s. Additionally, there are substantial differences in responses between the polar regions and the low-latitude equatorial region. Finally, a three-dimensional model coefficient was constructed to illustrate the influence of solar activity, ENSO, and QBO on temperature and humidity in the near space. The findings of this study contribute to a deeper understanding of the temperature and humidity variation characteristics in near space and provide valuable data and model references for predicting three-dimensional parameters of temperature and humidity in this region.

Potential of tree-ring chronologies for multi-centennial streamflow reconstructions: an insight from Nepal

Abstract. Rivers in the Himalayan and adjacent mountain regions are the lifelines of over 1 billion people and are the backbone of civilizations therein. The short gauge records of Nepal do not provide a sufficient time window to understand the natural variations in river discharge from a long-term climate perspective. By developing a network of over 100 tree-ring chronologies across Nepal, we checked their hydrological sensitivity for long-term streamflow reconstruction. This shows huge potential for long-term annual or seasonal streamflow reconstructions in different river basins of Nepal. A robust reconstruction model was developed between tree growth and streamflow, capturing 56 % of the variance in the actual data, and was used to reconstruct the March–July monthly average streamflow of Sinja Khola (river) at Diware from AD 1700 to 2013. The reconstruction revealed several dry and pluvial periods with the recent decline in the streamflow in the Sinja River. We found short- (2 to 8.7 years) to medium-term (35.2 years) periodicities in the reconstruction that are likely to be associated with climatic oscillations, such as the El Niño–Southern Oscillation (ENSO), the Atlantic Multidecadal Oscillation (AMO), and the North Atlantic Oscillation (NAO), along with the influence of local circulation patterns. Since Sinja Valley is related to the origin of the Nepali language and civilization, the information on long-term streamflow will be beneficial for water resource management in the context of rapid climate change and for preparedness for water-induced disasters in the region.

Climatic oscillation based 3-dimensional drought risk assessment over India

Drought risk assessment is essential for the efficient design of water resource infrastructures and agricultural planning. Conventional drought studies define droughts either in a spatial or temporal framework without considering the simultaneous temporal and spatial progression of droughts. Spatiotemporal drought (SPD), a dynamic and complex phenomenon, has been relatively understudied due to the challenges in developing algorithms for their identification. In this study, we use a 3-dimensional drought identification framework to identify the SPD events across India. Further, as large-scale ocean-atmospheric phenomena namely El Niño Southern Oscillation (ENSO) and Equatorial Indian Ocean Oscillation (EQUINOO) play an important role in modulating the occurrence of droughts in India, we investigated the influence of these climatic oscillations on SPD characteristics across different climatic regions of India. Further, ENSO-based drought risk assessment using drought characteristics and the synergy between univariate and multivariate drought risks are also evaluated. Results show that 1) there are significant seasonal and spatial variations in occurrences and magnitude of SPD characteristics for the different climate phases. SPDs during the ENSO positive (El Niño) and the EQUINOO negative phases have higher severity, especially over the monsoon core region. In northwest India, the median drought severity during El Niño events is over three times higher than La Niña events. Across most of India, a major portion of SPD event onset occurs during the monsoon seasons, however in the north-western and south-eastern regions an equal portion of drought onset occurs during the pre-monsoon and post-monsoon season, respectively. 2) Further, the ENSO-based drought risk assessment reveals that severe and longer-duration SPD events are associated with El Niño phases, making ENSO a crucial factor in drought frequency analysis. 3) The synergy between the univariate and multivariate drought risks conditioned on ENSO reveal that overall drought risks are linked to the magnitude of individual drought characteristics which have a strong association with ENSO phases. Thus, design criteria for drought resilient infrastructure should be based on the dominant drought characteristics influenced by ENSO phases for effective drought risk assessment. Overall, the study underscores the significant impact of ENSO on SPDs in India and the importance of incorporating ENSO information in drought frequency analysis for reliable risk assessments.

Counteracting Impacts of ENSO and the Aleutian Low on Winter Surface Air Temperature over Japan Sea Rim Region

Abstract Exploring the mechanisms modulating Japan Sea Rim (JSR) winter surface air temperature (JSRWT) holds significant scientific and societal importance. The present study unravels the counteracting impacts of El Niño–Southern Oscillation (ENSO) and the Aleutian low (AL) on JSRWT. Although ENSO and the AL have a significant positive correlation on interannual timescale, they exert totally opposite impacts on JSRWT. The positive Niño-3.4 sea surface temperature anomalies (SSTAs) usually lead to positive JSRWT anomalies, while an enhanced AL often results in negative JSRWT anomalies. The tropical convection anomalies associated with the positive Niño-3.4 SSTA induce two tropical to extratropical Rossby wave trains, leading to a barotropic anomalous anticyclone over northeast Asia, and thereby positive JSRWT anomalies. Conversely, the strengthened AL perturbs the westerly jet and induces an eastward-propagating Rossby wave train, leading to a barotropic anomalous cyclone over northeast Asia and negative JSRWT anomalies. The northeastward-propagating Rossby wave induced by the ENSO-related tropical convection anomalies over the Indian Ocean offsets the downstream Rossby wave induced by the strengthened AL, leading to counteracting impacts of ENSO and the AL on JSRWT. Finally, a novel index for monitoring JSRWT is proposed based on the indices of ENSO and AL. Significance Statement Despite the advantage of ENSO as a well-known predictability source, the seasonal predictability of Japan Sea Rim winter surface air temperature (JSRWT) is far from satisfactory. Here, we discovered that the Aleutian low (AL) has an independent influence on JSRWT contrasting with that of ENSO. When the AL and ENSO are in-phase, JSRWT shows no significant anomalies, but the JSRWT anomalies are largely amplified when AL and ENSO are out-of-phase. Therefore, a novel index for monitoring JSRWT is proposed based on the indices of ENSO and AL. These findings shed light on the low capacity of the seasonal prediction of JSRWT when only considering ENSO as the precursor.

Historical and Future Asymmetry of ENSO Teleconnections with Extremes

Abstract El Niño–Southern Oscillation (ENSO) is the dominant source of climate variability globally. Many of the most devastating impacts of ENSO are felt through extremes. Here, we present and describe a spatially complete global synthesis of extreme temperature and precipitation relationships with ENSO. We also investigate how these relationships evolve under a future warming scenario under high greenhouse gas emissions using 14 models from phase 6 of Coupled Model Intercomparison Project (CMIP6) ensemble. First, we demonstrate that models broadly capture observed ENSO teleconnections to mean and extreme climate using the Twentieth Century Reanalysis, version 3 (20CRv3). The models project that more regions will experience an amplification of the historical ENSO teleconnection with mean temperature and precipitation than a dampening under a high-emission climate scenario. The response of the ENSO teleconnection with extremes is very similar to the mean response, with even larger changes in some regions. Hence, regions that are predicted to experience an amplification of the ENSO teleconnection under future warming can also expect a comparable amplification in the intensity of extremes. Furthermore, models that suggest greater amplification of ENSO amplitude also tend to exhibit greater intensification of mean and extreme teleconnections. Future changes in regional climate variability may be better constrained if changes in ENSO itself are better understood.

Revisiting the Role of Atmospheric Initial Signals in Predicting ENSO

Abstract El Niño–Southern Oscillation (ENSO) provides an important source of global seasonal–interannual predictability, while its prediction encounters bottlenecks. Besides the slow-varying air–sea feedbacks, high-frequency atmospheric signals (HFASs) act on ENSO evolution. This study revisits the role of atmospheric initial signals in ENSO prediction using an atmosphere–ocean coupled model. Two sets of sensitivity hindcasts are conducted. One utilizes a pure sea surface temperature (SST) nudging for initialization so that no observed atmospheric internal signal is assimilated. The other applies a combination of the SST nudging and spectral nudging of JRA-55 reanalysis, which not only assimilates the observed atmospheric states and hence realizes skillful predictions of HFAS at the initial stage but also improves the oceanic initial conditions (ICs), especially around the thermocline. Unexpectedly, the better atmosphere–ocean ICs neither improve ENSO prediction nor overcome the spring prediction barrier. Further analysis of Bjerknes stability index suggests that underestimated negative feedbacks and insufficient responses of ocean currents and thermocline slope to atmospheric internal winds may account for the failure. Nevertheless, assimilating the atmospheric information partly improves the prediction of El Niño onset, especially for two recent extreme cases (i.e., 1997/98 and 2015/16). This improvement is associated with better representations of initial westerly wind bursts (WWBs) that excite subsequent downwelling equatorial Kelvin waves. However, due to unpredictable WWBs and underestimated wind response to the SST warming owing to the cold tongue biases in boreal summer, the zonal advective feedbacks are underestimated and thus further development of El Niño cannot be well predicted. This study suggests the importance of initial atmospheric signals despite the limitation, prompting further efforts to improve model physics.

Distinct impacts of the El Niño–Southern Oscillation and Indian Ocean Dipole on China's gross primary production

Abstract. Gross primary production (GPP), a crucial component in the terrestrial carbon cycle, is strongly influenced by large-scale circulation patterns. This study explores the influence of the El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) on China's GPP, utilizing long-term GPP data generated by the Boreal Ecosystem Productivity Simulator (BEPS). Partial correlation coefficients between GPP and ENSO reveal substantial negative associations in most parts of western and northern China during the September–October–November (SON) period of ENSO development. These correlations shift to strongly positive over southern China in December–January–February (DJF) and then weaken in March–April–May (MAM) in the following year, eventually turning generally negative over southwestern and northeastern China in June–July–August (JJA). In contrast, the relationship between GPP and IOD basically exhibits opposite seasonal patterns. Composite analysis further confirms these seasonal GPP anomalous patterns. Mechanistically, these variations are predominantly controlled by soil moisture during ENSO events (except MAM) and by temperature during IOD events (except SON). Quantitatively, China's annual GPP demonstrates modest positive anomalies in La Niña and negative IOD years, in contrast to minor negative anomalies in El Niño and positive IOD years. This outcome is due to counterbalancing effects, with significantly larger GPP anomalies occurring in DJF and JJA. Additionally, the relative changes in total GPP anomalies at the provincial scale display an east–west pattern in annual variation, while the influence of IOD events on GPP presents an opposing north–south pattern. We believe that this study can significantly enhance our understanding of specific processes by which large-scale circulation influences climate conditions and, in turn, affects China's GPP.

Tropical Interbasin Interaction as Effective Predictors of Late-Spring Precipitation Variability in the Southern Great Plains

Abstract The southern Great Plains experience fluctuating precipitation extremes that significantly impact agriculture and water management. Despite ongoing efforts to enhance forecast accuracy, the underlying causes of these climatic phenomena remain inadequately understood. This study elucidates the relative influence of the tropical Pacific and Atlantic basins on April–May–June precipitation variability in this region. Our partial ocean assimilation experiments using the Community Earth System Model unveil the prominent role of interbasin interaction, with the Pacific and Atlantic contributing approximately 70% and 30%, respectively, to these interbasin contrasts. Our statistical analyses suggest that these tropical interbasin contrasts could serve as a more reliable indicator for late-spring precipitation anomalies than El Niño–Southern Oscillation. The conclusions are reinforced by analyses of seven climate forecasting systems within the North American Multi-Model Ensemble, offering an optimistic outlook for enhancing real-time forecasting of late-spring precipitation in the southern plains. However, the current predictive skills of the interbasin contrasts across the prediction systems are hindered by the lower predictability of the tropical Atlantic Ocean, pointing to the need for future research to refine climate prediction models further. Significance Statement Agriculture and infrastructure in the southern plains face challenges from severe late-spring precipitation extremes. Traditional predictors like El Niño–Southern Oscillation (ENSO) lose effectiveness during the critical spring-to-summer transition, creating a forecasting gap. This study introduces the concept of tropical interbasin interactions, known to enhance seasonal predictability for late-spring precipitation in the southern plains. Novel climate model experiments highlight contributions from the tropical Pacific and Atlantic, offering a promising predictability that potentially surpasses the limitations of ENSO-based predictions. These outcomes hold the potential for developing operational forecasts of late-spring precipitation anomalies in the southern plains, enabling proactive risk management.

Stronger Westerly Wind Bursts in a Warming Climate: The Effects of the Pacific Warming Pattern, the Madden–Julian Oscillation, and Tropical Cyclones

Abstract Westerly wind bursts (WWBs) in the western–central equatorial Pacific are critical in El Niño–Southern Oscillation (ENSO) dynamics. Understanding how they may change with global warming has important implications for future projections of El Niño. In this study, we investigate how the enhanced eastern equatorial Pacific warming pattern, emerging in future climate projections, can influence WWB characteristics in an atmospheric general circulation model, CAM6. Changes in three main factors affecting WWBs—El Niño-conditions mean westerly wind stress anomalies, the Madden–Julian oscillation (MJO), and tropical cyclones (TCs)—are analyzed. We find that during El Niño onset (December–April), the WWB wind stress intensity remains largely unchanged but WWBs shift westward by about 20° of longitude. In contrast, during El Niño development (May–November), the WWB intensity increases by 41% or 79% in two warming scenarios considered [shared socioeconomic pathways (SSP5-8.5) and SSP2-4.5, respectively], which is mainly caused by a higher frequency of TC occurrence in the central tropical Pacific within 15°N/S. Further, we find that westerly wind speed anomalies associated with El Niño and the MJO also increase during El Niño development. However, as trade winds weaken in the central-eastern equatorial Pacific, the mean strength of the resulting westerly wind stress anomalies does not change much, and no significant eastward shift of WWBs is observed. Thus, our atmospheric model simulations suggest a strong TC-driven increase in WWB wind stress anomalies during El Niño development and hence a more important role of TCs in WWB generation, which in a coupled system could lead to stronger ENSO events, enhanced TC–ENSO coupling, and even greater intensification of WWBs.

Variability of ENSO teleconnections indices, and its impacts on moroccan agriculture

In Morocco, drought periods have become more frequent and severe due to climate change, which has had a substantial effect on freshwater supply and agricultural output. The El Niño-Southern Oscillation (ENSO) and the influence of climatic variability were the main subjects of the current study, which made use of daily precipitation, maximum and minimum temperature data collected at 50 locations around the nation from 1990 to 2022. The study analysed Palmer Drought Severity Index (PDSI) over Morocco to evaluate the impact of climate indices such as the Oceanic Niño Index (ONI) and the North Atlantic Oscillation (NAO) on drought severity. It also investigated the changes in precipitation, temperature, and extreme event-related indices. Rainfall is used as a proxy for El Nino and La Nina, supported by a negative and significant correlation between Oceanic Nino Index (ONI) and rainfall. Attempted to understand the impact of the NAO on Morocco's agricultural production, particularly during the winter months. During negative NAO phases, winter temperatures can lead to reduced wheat yields by 35–45% during the El Niño years and decreased by 4–7% during the La Niña years compared to the actual yield. Relying on the NAO plays a crucial role in modulating the precipitation patterns, which implies that crop requires adequate soil moisture with no extreme temperature during the growing season in order to produce higher yield. ENSO events can indeed lead to these extreme conditions in selected locations, potentially impacting crop yields.

Evaluation of Equatorial Westerly Wind Events in the Pacific Ocean in CMIP6 Models

Abstract Westerly wind events (WWEs) are anomalously strong, long-lasting westerlies over the Indian or Pacific Oceans that are capable of forcing oceanic wave modes, which in turn can impact the evolution of coupled ocean–atmosphere phenomena such as El Niño–Southern Oscillation (ENSO). This work examines the fidelity of equatorial WWEs over the Pacific Ocean in 30 CMIP6 historical simulations against observations. WWEs are identified using equatorially averaged zonal wind stress anomaly duration, zonal extent, and intensity criteria. Most simulations correctly place the majority of WWEs over the west Pacific although they are skewed westward and generally occur less frequently compared to observations. Simulated WWEs tend to be weaker than observations for a given duration and zonal extent with several models having shorter durations and zonal extents than observations. Biases in simulated WWEs are associated with biases in Madden–Julian oscillation (MJO) and convectively coupled Rossby wave (CRW) variability. Models that underpredict WWE forcing in the west Pacific also severely underpredict MJO and CRW variance. Further, the multimodel mean shows a smaller fraction of WWEs associated with both the MJO and CRW than observations.

Reconstruction of Minimum May Temperatures in Northeast China Since 1797 AD Based on Tree Ring Width in Pinus sylvestris var. mongolica

We developed a tree ring width chronology from 1797 to 2020 (224 years) for the northwestern foothills of the Greater Khingan Mountains (GKMs) in northeastern China using 51 tree ring sample cores from 24 Pinus sylvestris var. mongolica (PSM). Pearson’s correlation analysis was used to analyze the relationship between tree ring width and regional climate factors. The standardized chronology was positively associated with the minimum temperature (Tmin) in the previous May (r = 0.721, p < 0.01), indicating that this parameter was the main climatic factor limiting PSM growth in the region. We established a secure reconstruction equation for the May Tmin from 1797 to 2020. There were 31 warm and 43 cold years in the 224-year reconstructed temperature series, accounting for 13.8% and 19.2% of the total years, respectively. Warm periods were observed in 1820–1829, 1877–1898, 1947–1958, and 1991–2020, whereas cold periods occurred in 1820, 1829–1870, 1899–1927, 1934–1947, and 1960–1988. The observed temperature sequence was highly consistent with the reconstructed sequence from the tree rings, which verified the reliability of the reconstructed results. The spatial correlation analysis indicated that the reconstructed temperature sequence accurately represented the temperature changes in the northwestern foothills of the GKM and surrounding areas. Multi-window spectral analysis and wavelet analysis revealed significant periodic fluctuations from 2 to 6 years, 21.2 years, 48.5 years, and 102.2 years. These periodic variations may be related to the El Niño–Southern Oscillation (ENSO), the Atlantic Multi-Year Intergenerational Oscillation (AMO), the Pacific Decadal Oscillation (PDO), and solar activity. This study expands the existing climate records in the region and provides valuable data support for understanding climate change patterns in the GKM and the scientific predictions of future climate changes.

Evolution and Drivers of Extreme Subsurface Marine Heatwaves in the Western Tropical Pacific Ocean during 2008 and 2010–11

Abstract Marine heatwaves (MHWs) have adverse impacts on marine ecosystems and fisheries, yet extreme MHWs in the western tropical Pacific Ocean remain largely unexplored. Here, we investigate the evolution and drivers of the two strongest subsurface MHWs in the western tropical Pacific Ocean on record, in 2008 (MHW-08) and 2010–11 (MHW-11). The two events have similar evolutions, as they were both initiated and developed locally in tropical regions during their onset phase and gradually dissipated with multiple cores during the decay phase. We examined the physical processes during the evolution of MHW-08 and MHW-11 and performed a heat budget analysis for the subsurface layer in each case. We find that the onset of both events were mainly controlled by convergence and vertical heat advection due to anomalous Ekman downwelling, while the decay of both events was mainly controlled by horizontal heat advection due to anomalous horizontal currents and withdrawal of anomalous convergence. The relationship between the subsurface MHWs and El Niño–Southern Oscillation is discussed. We suggest that the anomalous heat advections plus the La Niña–related background warming lead to the extreme subsurface MHW events. Our findings may have important implications for environmental change and marine life in the western tropical Pacific Ocean.

Understanding northeastern tropical atlantic ocean dynamics in relation to climate indices

Since 1993, Satellite Altimetry greatly enhanced the ability to study and understand ocean dynamics, particularly in the context of climate change. Though relatively low-energy and understudied, the Northeast Tropical Atlantic Ocean (NTAO) plays a crucial role in the Earth’s climate system. This study aims to deepen understanding of the NTAO region using the satellite altimetry-derived daily sea level gridded data set provided by the Copernicus Climate Change Service (C3S).The analysis of long-term regional Sea Level Anomaly (SLA) signals in the NTAO reveals a higher rate of sea level rise compared to the global average. The same analysis for regional Eddy Kinetic Energy (EKE) per unit mass and surface geostrophic currents shows declining rates, in contrast to global counterparts.Correlation analysis between SLA and climate indices (CI) uncovered significant links with the North Atlantic Oscillation, Tropical North/South Atlantic, Western Hemisphere Warm Pool, and Southern Oscillation Index. Composite maps of sea surface temperature (SST), sea level pressure (SLP), and wind anomalies, as well as complementary maps with anomalies of SLA, EKE, and ocean circulation, were examined to understand the primary mechanisms behind these correlations. SST emerged as the main forcing factor, with SLP and wind anomalies also contributing to specific regional and index correlations. EKE anomalies further elucidate differences in the anomalies of the surface geostrophic currents in the areas influenced by the key currents in the study region. The findings of this study show an intricate interplay between oceanic dynamics and climate phenomena, shedding light on the complex mechanisms driving changes in the Northeast Tropical Atlantic Ocean.

ENSO predictive analytics based on layered rendering

El Niño-Southern Oscillation (ENSO) is a periodic climate phenomenon in the equatorial Pacific that significantly influences global climate patterns. Accurate prediction and monitoring of ENSO events are essential for meteorological agencies and governmental institutions. This study introduces a content-guided attention module within a convolutional neural network to improve prediction accuracy. This module models inter-channel relationships and enhances information interaction by integrating channel and spatial attention weights. These advancements substantially improve prediction accuracy and help overcome the spring prediction barrier in ENSO forecasting. The research emphasizes global feature modeling and proposes a novel content-guided ENSO prediction model. It also includes an ocean data generation model utilizing global attention. Furthermore, a layered rendering technique is employed to invert ocean data, facilitating detailed analysis and contributing to the development of an ocean synthetic dataset.

Extremes of Temperature and Precipitation Under CMIP6 Scenarios Projections Over Central Hokkaido, Japan

ABSTRACTClimate extreme events are intensifying globally, posing increasing risks across various sectors. Understanding climate extremes' spatiotemporal patterns and responses to climate change is crucial for effective management, especially on a regional scale. This study examines temperature and precipitation extremes, as well as compound dry‐hot events (CDHEs), in the Ishikari River basin (IRB) of Northeastern Japan, an area of significant socioeconomic importance. We focus on spatiotemporal analysis under multiple scenarios of temperature/precipitation extremes and CDHEs based on statistical downscaled datasets from the Coupled Model Intercomparison Project Phase 6. Results indicate that IRB underwent increased trends of extreme hot periods, extreme droughts, and heavy rainfalls during 1985–2014, which are significantly affected by the North Pacific Oscillation and Southern Oscillation Index. Future projections show that warming temperatures and less rainfall shift asymmetrical impacts on temperature and precipitation extremes, expecting increased warm spells and CDHEs but increased wet durations and less heavy rainfalls. Emission scenarios analysis suggests low‐emission scenarios (SSP1‐2.6) could mitigate their exacerbations, especially for CDHEs (decreased by 139%). Moreover, spatial‐pattern analysis reveals regional heterogeneity in temperature and precipitation extremes, with northern mountainous regions more susceptible to thermal extremes and southern plain regions (e.g., Sapporo city) experiencing prolonged drought and CDHEs. This study provides valuable insights into climate risk management and adaptation strategies.

El Niño southern oscillation, weather patterns, and bacillary dysentery in the Yangtze River Basin, China

BackgroundIncreasingly intense weather anomalies associated with interannual climate variability patterns, like El Niño-southern oscillation (ENSO), could exacerbate the occurrence and transmission of infectious diseases. However, research in China remains limited in understanding the impacts and intermediate weather changes of ENSO on bacillary dysentery (BD). This study aimed to reveal the relationship between ENSO, weather conditions, and the incidence of BD, and to identify the potential meteorological pathways moderated by ENSO in the ENSO-BD connections.MethodsBD disease data and meteorological data, as well as ENSO index, from 2005 to 2020 were obtained for 95 cities in the Yangtze River Basin. We first established the associations between ENSO events and BD, ENSO and weather, as well as weather and BDs using two-stage statistical models. Then, we applied a causal mediation analysis to identify the specific meteorological changes in the ENSO-BD relationship.ResultsIn the Yangtze River Basin, both El Niño (IRR: 1.06, 95%CI: 1.04 ~ 1.08) and La Niña (IRR: 1.03, 95%CI: 1.02 ~ 1.05) events were found to increase the risk of BD. Variations of ENSO index were associated with changes in local weather conditions. Both the increases in regional temperatures and rainfall were associated with a higher risk of BD. In the casual mediation analyses, we identified that higher temperatures and excessive rainfall associated with La Niña and El Niño events mediated the ENSO’s effect on BD, with mediation proportions of 38.58% and 34.97%, respectively.ConclusionsLong-term climate variability, like ENSO, can affect regional weather conditions and lead to an increased risk of BD. We identified the mediating weather patterns in the relationship between ENSO and BD, which could improve targeted health interventions and establish an advanced early warning system in response to the BD epidemic.

New northernmost distribution records of the Eastern South Pacific southern right whale (Eubalaena australis), including the first cases from Ecuador and northern Peru.

The Eastern South Pacific Right Whale (SRW) (Eubalaena australis) population has gained interest due to its Critically Endangered conservation status. So far, this population has been confirmed only along the coasts of Chile (18°20'S to 56°30'S) and from southern to central Peru (17°38'S to 12°11'S). Recent records have extended the species' known range, highlighting its geographic distribution, now reaching 1500 km north. Here, we report six recent records, consisting of five sightings and one stranding, that expand the documented range to northern Ecuador (0.6°N). The northern extension of the population may be associated with the unusual three-year-long cold phase (La Niña) of the El Niño Southern Oscillation (ENSO) in the eastern South Pacific, population expansion, movement and re-distribution of the species, increased monitoring effort, or a combination of these factors. These observations raise hope for the Critically Endangered SRW population, as the occurrence of mother-calf pairs may indicate a potential for population recovery. Nevertheless, these findings intensify concerns for what is still the least abundant SRW population, underscoring the urgency for more targeted research and conservation measures.

Climate Extremes in the New Zealand Region: Mechanisms, Impacts and Attribution

ABSTRACTAs global surface temperatures have increased with human‐induced climate change, notable compound climate extremes in the New Zealand (NZ) region associated with atmospheric heatwaves (AHWs) and marine heatwaves (MHWs) have occurred in the past 6 years. Natural modes of variability that also played a key role regionally include the Interdecadal Pacific Oscillation (IPO), El Niño/Southern Oscillation (ENSO) and changes in the location and strength of the westerlies as seen in the Southern Annular Mode (SAM). Along with mean warming of 0.8°C since 1900, a negative phase of the IPO, La Niña phase of ENSO and a strongly positive SAM contributed to five compound warm extremes in the extended austral summer seasons (NDJFM) of 1934/35, 2017/18, 2018/19, 2021/22 and 2022/23. These are the most intense coupled ocean/atmosphere (MHWs/AHWs) heatwaves on record with average temperature anomalies over land and sea +0.8°C to 1.1°C above 1991–2020 averages. The number of days above 25°C and above the 90th percentile of maximum temperature has increased, while the number of nights below 0°C and below the 10th percentile has decreased. Coastal waters around NZ recently experienced their longest MHW in the satellite era (1982‐present) of 289 days through 2023. The estimated recurrence interval reduces from 1 in 300‐years for the AHW event during the 1930s climate to a 1 in 25‐year event for the most recent decade. Consequences include major loss of ice of almost one‐third volume from Southern Alps glaciers from 2017 to 2021 with rapid melt of seasonal snow in all four cases. Above‐average temperatures in the December/January grape flowering period resulted in advances in veraison (the onset of ripening); and higher‐than‐average grape yields in 2022 and 2023 vintages. Marine impacts include widespread sea‐sponge bleaching around northern and southern NZ.