Southerly Winds Research Articles

Abstract Concurrent cold and wet winter conditions in southern China may cause human discomfort and give rise to freezing rain and snow disasters. This work examines the cross-seasonal connection of autumn convection over the western tropical Indian Ocean (WTIO) with the winter climate in southern China based on both statistical analysis and numerical experiments. The result shows that the anomalous WTIO convection in autumn can persist into winter, which continuously excites a wave train propagating northeastward from the Arabian Sea to southern China. The subtropical westerlies are strengthened to the north of the anomalous Arabian Sea anticyclone and are conducive to the widespread cooling in subtropical Eurasia, including the Tibetan Plateau (TP). The anomalous cyclone over the TP and southern China favors enhanced precipitation in situ. Accordingly, the TP snow cover increases significantly since early winter and persists into the following winter and spring due to the snow–albedo effect. The cooling effect of the TP snow cover helps to intensify the cyclone over southern China and the anticyclone over the western North Pacific. Combined with the deepened India–Myanmar trough induced by WTIO convection, the anomalous southerly wind transports more water vapor from the ocean to southern China, leading to wetter winter in the region. The result of the linear baroclinic model experiments further verifies that WTIO heating can trigger a wave train propagating to the TP, and the cooling effect of the TP helps to maintain and extend the influence of WTIO convection from autumn to winter, affecting southern China. Significance Statement Early signals for cold–wet winter climate in southern China can be traced back to the western tropical Indian Ocean (WTIO) in the preceding autumn. This study reveals the cross-seasonal connection of autumn WTIO convection with the winter climate and the bridging role of the Tibetan Plateau (TP). The WTIO convection can trigger pronounced subtropical cooling and cyclonic anomalies in the TP, resulting in more snow cover. The snow–albedo effect causes the TP cooling to persist from early winter into the following spring. This cooling effect of the TP helps to maintain and extend the influence of WTIO convection from autumn to winter by intensifying the cyclone over southern China and the anticyclone over the western North Pacific, resulting in cold–wet winter climate.

Abstract To verify the identified irrigation effect on regional atmospheric circulation and precipitation in the U.S. Great Plains, as articulated in a recent dry-year case study, this work examined the irrigation effect in five extremely dry years. The ensemble results confirm the findings in the earlier case study, corroborating the irrigation effect on climate in the region. Irrigation largely increases rainfall rates in most events but does not affect their initiation, frequency, and duration. These changes result from modifications in atmospheric energy conditions due to irrigation-induced changes in both moisture and temperature. This study further examined five extremely wet years in the region and compared their ensemble irrigation effect to that in the dry years, with precipitation events defined using daily precipitation to ensure consistency in characterizing event intensity, duration, and timing. Their differences indicate a similar impact of irrigation on increasing precipitation intensity but with milder modifications to the atmospheric thermodynamic profile in wet years. Both wet and dry year ensembles show a weakening effect of irrigation on low-level southerly winds in the Great Plains. While these similar effects suggest that irrigation has an “add-on” effect on precipitation in wet and dry years instead of strong interactions with regional circulation, a larger percentage increase in precipitation in dry years than in wet years shows a more potent irrigation impact in the dry conditions, supporting the notion that large-scale irrigation can potentially help reduce regional drought severity.

Unique research aircraft observations were conducted within an Arctic fjord in Svalbard during three days in March 2013. Wijdefjorden is 110 km long, 5–15 km wide and has a north–south axis. Two-thirds of the fjord were covered by land-fast sea ice, but the northern part of the fjord was open. On two days the flow over the fjord was largely controlled by orographic channelling of the north-easterly wind, and on all three days a cold-air mass accumulated over the sea ice in the fjord and gradually propagated towards the open sea in the north. An ice breeze (analogous to land breeze) circulation, due to a strong temperature gradient across the sea-ice edge, was a key driver of the southerly near-surface wind over the fjord. On two days, the cold-air mass reached the open sea and the near-surface air mass warmed rapidly by several Kelvins. On one day, the channelled northerly flow pushed the cold-air mass to the south, from where it gradually propagated back to the north after the channelled flow had weakened. The results suggest that the channelling of the large-scale flow in the fjord can suppress the ice breeze to a shallow near-surface layer and even push the cold-air mass far south of ice edge. The near-surface air temperature and wind fields that were based on the Copernicus Climate Change Service Arctic Regional Reanalysis (CARRA) data set included large errors because CARRA did not have any sea ice in the fjord.

Abstract. The North China Plain (NCP) experiences severe air pollution, with PM2.5 (fine particulate matter with an aerodynamic diameter ≤ 2.5 µm) as the primary pollutant, especially in early winter (November to December). The PM2.5 concentrations in this period are significantly modulated by the El Niño-Southern Oscillation (ENSO). In this study, we have found that the stratospheric Quasi-Biennial Oscillation (QBO) exerts a nonlinear impact on the relationship between ENSO and PM2.5 concentrations over the NCP in early winter. During the easterly QBO (EQBO) phase, ENSO's influence on PM2.5 concentration is stronger compared to the westerly QBO (WQBO) phase. In El Niño and EQBO years, PM2.5 concentrations rise due to meteorological factors like a shallower boundary layer, higher relative humidity, and intensified southerly wind anomalies. Conversely, during La Niña and EQBO years, PM2.5 levels decrease due to opposite meteorological conditions. The study attributes these changes to planetary wave dynamics. During El Niño and EQBO years, upward-propagating planetary waves in mid-latitudes enhance upper-level divergence over Eurasia, strengthening westerlies. These westerlies guide Rossby wave trains into Northeast Asia, forming a strong anomalous anticyclone that worsens air pollution over the NCP. In La Niña and EQBO years, downward-propagating planetary waves induce divergence in sub-polar regions, strengthening westerlies that facilitate La Niña-related wave trains. These wave trains trigger cyclonic circulation over Northeast Asia, improving air quality in the NCP. These findings underscore the complex interplay between ENSO, QBO, and atmospheric dynamics in shaping regional air pollution.

ABSTRACTCold surges entering the Gulf of Mexico (GoM) generate northerly winds (Norte events), preceded by warm southerly winds (Surada events). These events were characterised in the Eastern Bay of Campeche (EBC) using ERA5 reanalysis data for 2002–2024. Both Norte and Surada events exhibited distinct intensity and predominant direction patterns in the EBC, compared with the broader GoM. Therefore, the separate identification of both events specific to the EBC was proposed. A minimum wind magnitude threshold (E) was determined for the EBC, above which events were considered sufficiently intense to be classified as Norte (2.4 ms−1) or Surada (1.3 ms−1) events in this region. It was shown that Norte events lasting < 24 h were associated with more intense Surada events; overall, 70.1% of Surada events exceeded the intensity of the corresponding Norte events, with a mean difference of 1.8 m s−1. Empirical Orthogonal Functions analysis for the southern GoM revealed that, in ~30% of the cases (Modes 2 and 3), cold fronts moved with a significant zonal component in the southern GoM. This pattern was associated with intense Surada events and weak or even absent Norte events in the EBC. Mode 1 accounted for more than 63% of the variability and corresponded to Surada events followed by Norte events with similar behaviour in the entire region. This study demonstrates a distinct wind behaviour associated with cold surges on the eastern and western sides of the Bay of Campeche in the southern GoM. Norte and Surada events can negatively impact local marine and fisheries sectors, as wind intensity forecasts are often generalised for the entire GoM and can be unreliable in the EBC. These events are critical for coastal circulation and influence ecosystem dynamics, fisheries, and key oceanographic processes such as coastal‐trapped waves, upwellings, and wave fields.

Abstract The Ross Sea is the most productive region of phytoplankton around the Antarctic margin and supports the marine food web in the Southern Ocean. However, the long-term variability of chlorophyll-a production in this region is not fully understood. Here we explore the long-term changes in austral summer chlorophyll-a concentrations in the Ross Sea region across the 1997-2023 period. The results indicate a clear east-west asymmetric change in chlorophyll-a concentration between 180°W-130°W: decreasing (increasing) in the west (east), which is dominated by changes in wind forcing and sea ice coverage. Cyclonic wind anomalies drive regional sea ice divergence off Marie Byrd Land, while increasing coastal easterly winds off Marie Byrd Land and southerly wind anomalies in the western Ross Sea drive regional sea ice convergence. As a result, the availability of photosynthetically active radiation (PAR) increased (decreased), promoting (limiting) phytoplankton growth in the eastern (western) zone. The warming SST and potential increases in dissolved iron may also contribute to the chlorophyll-a blooms in the eastern zone.

ABSTRACTThe spatial unevenness of precipitation significantly impacts local hydrological cycles and exacerbates natural hazards. However, the underlying mechanisms governing such variability over complex terrains remain poorly understood. This study bridges this gap by employing a spatial unevenness index to investigate environmental conditions and fine‐scale characteristics of precipitation events with different spatial unevenness over the steep terrains in North China. Results show that strongly uneven precipitation events are associated with unstable atmospheric stratification and high convective available potential energy (CAPE). Both cold‐top–warm‐bottom temperature anomalies and wet‐bottom–dry‐top humidity anomalies enhance atmospheric instability. Under the thermodynamic influence of complex terrain, these events cluster along the mountains and predominantly occur in the afternoon, coinciding with diurnal peaks in both precipitation frequency and intensity. In contrast, weakly uneven precipitation events are mainly driven by synoptic‐scale forcing, featured with lower‐tropospheric convergence, upper‐tropospheric divergence, and strong large‐scale upward motion. Warm anomalies in the upper troposphere and abundant moisture transported by anomalous low‐level southerly winds are crucial to these events. Spatially, weakly uneven precipitation events spread extensively across North China, covering both mountains and plains. Maximum precipitation amount occurs at the foot of mountains, highlighting the blocking and uplifting effects of topography. For this type, precipitation amount and frequency peak in the early morning, whereas intensity peaks in the afternoon. These findings advance our understanding of precipitation unevenness and provide a scientific basis for improving flood forecasting and water resource management in complex terrains.

Based on a coupled high-resolution numerical model, changes in the current structure and wind wave field in the northeastern part of the Neva Bay adjacent to the 300th Anniversary Park of St. Petersburg caused by coastal hydrotechnical constructions have been analysed. Using August 2011 conditions, it has been shown that under weak winds conditions, the River Neva runoff is the main contributor to the formation of the current field in this region. The influence of coastal constructions is manifested in the destruction of an anticyclonic vortex near the hydrotechnical structure No. 3 and a in a decrease of current velocity from 15 cm/s to 5 cm/s. For December 2011 conditions, it has been found that under weak southwestern and western winds, the influence of coastal constructions is expressed in a decrease of current velocity by 5–10 cm/s in the beach zone of the park while maintaining the overall structure of the current field. During stormy westerly winds, typical of late December 2011, a considerable southward deflection of the Neva outflow occurs, reducing the outflow current velocity to 20–25 cm/s. At the same time, a current directed along the shoreline from the northwest to the southeast forms in the beach area. The influence of coastal structures in this case leads to a decrease in current velocity by 5 cm/s in the area between hydrotechnical structures No. 2 and No. 3, resulting in the formation of a stagnant zone. Analysis of the wave regime has revealed that coastal constructions create wave shadow zones, thus significantly reducing wave heights in their immediate vicinity, though the protective effect is limited to localised areas. The maximum decrease in wave activity due to the presence of coastal constructions is observed under westerly winds, while the minimum occurs under southerly winds.

Atmospheric Rivers (ARs) are key drivers of extreme precipitation and hydrological variability along the west coasts of continents. While many studies have focused on their atmospheric impacts, the oceanographic response remains underexplored. Using remote sensing and in situ observations, this study examines how ARs affect river plumes, hydrodynamics and biogeochemical conditions in central-southern Chile (33–40° S). Synoptic atmospheric conditions associated to the passage of different oriented AR (i.e., Tilted and Zonal ARs) produce contrasting river plume dynamics, while TARs favor coastally trapped and southward-advected plumes by the northerly winds, ZARs generate dispersed and offshore plumes influenced by southerly winds. High resolution mooring data show that both TARs and ZARs initially enhance vertical mixing and currents by strong winds, followed by stratification due to the arrival of a river plume. Biogeochemical samplings before and after the passing of a series of ARs show that TARs increase surface nitrates, silicic acid and chlorophyll-a more than ZARs. The results provide novel insights into the response of river plumes and water column changes to the passage of ARs in the coastal ocean.

This study presents an integrated assessment of anchorage-related emissions and air quality impacts in the Panama Canal region through Automatic Identification System (AIS) data, bottom-up emission estimation, and atmospheric dispersion modeling. One year of terrestrial AIS observations (July 2024–June 2025) captured 4641 vessels with highly variable waiting times: mean 15.0 h, median 4.9 h, with maximum episodes exceeding 1000 h. Annual emissions totaled 1,390,000 tons of CO2, 20,500 tons of NOx, 4250 tons of SO2, 656 tons of PM10, and 603 tons of PM2.5, with anchorage activities contributing 497,000 tons of CO2, 7010 tons of NOx, 1520 tons of SO2, 232 tons of PM10, and 214 tons of PM2.5. Despite the main engines being shut down during anchorage, these activities consistently accounted for 34–36% of the total emissions across all pollutants. High-resolution emission mapping revealed hotspots concentrated in anchorage zones, port berths, and canal approaches. Dispersion simulations revealed strong meteorological control: northwesterly flows transported emissions offshore, sea–land breezes produced afternoon fumigation peaks affecting Panama City, and southerly winds generated widespread onshore impacts. These findings demonstrate that anchorage operations constitute a major source of shipping-related pollution, highlighting the need for operational efficiency improvements and meteorologically informed mitigation strategies.

Abstract. In this study, we analysed the extreme meteo-marine event that occurred between October and November 2023 in the northern Adriatic Sea region, focusing on its effects in the Gulf of Trieste (GoT). This event featured a strong inflow of very humid southerly winds, very intense thundershowers and storm surges on the coast, and caused several damages in the north-eastern part of Italy. The heavy rainfall in the Isonzo/Soča catchment led to two major runoff peaks with significant discharges into the GoT. These events represent an ideal case study to investigate how the interplay between local river discharges and the wind regime influence ocean currents in coastal areas. We adopted an integrated approach to fully understand the dynamics of peculiar environmental processes, clearly emerging from the visual analysis of satellite images (Sentinel-2) collected throughout the event. Therefore, we incorporated in our analysis multiple datasets, including rainfall, wind and surface currents from both HF radars and numerical models. In this way, we could analyse the interaction between river runoff and ocean currents in the GoT, and the importance of prevailing winds such as Bora and Sirocco in modulating current dynamics. The use of rainfall time series allowed us to assess the impact of precipitation on environmental conditions, while the analysis of the wind regime helped to understand the patterns, distribution and intensity of winds in the area of interest. It was observed that the intense runoff of the Isonzo/Soča River triggered by heavy rainfall can override the effects of wind, leading to a dominance of river-induced circulation in the GoT. Such a multi-platform integrated approach proves to be a useful tool for the analysis and, potentially, forecast of surface ocean dynamics and possible extreme events in coastal areas.

ABSTRACT South China experienced substantial rainfall from April 19 to April 22, 2024, with accumulated precipitation ranging from 200 mm to 350 mm. This significant precipitation was primarily driven by the combined synoptic influences of the southern branch trough, low‐level jet stream, and the Jiang–Huai cyclone, affecting northern and central‐eastern Guangxi as well as most parts of Guangdong. These synoptic conditions facilitated the initiation, development, and propagation of mesoscale convective systems (MCSs). Specifically, an MCS initiated in the evening over the eastern edge of the Yunnan–Guizhou Plateau (YGP), leading to the formation of a mesoscale vortex with closed cyclonic circulation at 850 hPa, which further promoted the merging of convection cells into an organized MCS. The intensified southerly winds appeared over the eastern parts of the mesoscale vortex, preceding the peak meridional component of moisture convergence by approximately 4–5 h. Moisture budget analysis revealed that the meridional component of horizontal moisture convergence was the primary contributor to the moisture increase over Guangxi and Guangdong provinces. Consequently, the enhanced mesoscale systems (vortices and MCSs) significantly increased horizontal convergence at lower levels, contributing substantially to the moisture accumulation over South China. The intensified low‐level southerly wind associated with mesoscale vortices can be considered a potential forewarning parameter for short‐range precipitation forecasting in such heavy rainfall events.

Abstract Wind energy is a growing component of energy production in Illinois (IL). However, uncertainty remains regarding future wind speed variability and trends and their potential impact on wind energy generation. Here, we assess recent (1992–2021) trends in monthly average wind speed and direction using data from the Illinois Climate Network (ICN), which consists of 18 weather stations across IL, supplemented by five IL stations from the Global Historical Climatology Network (GHCN) hourly dataset. We find decreases in mean annual wind speed at most ICN stations, ranging from −0.46% to −17.92% decade−1, and all five GHCN stations (from −1.53% to −6.53% decade−1). Decreasing wind speed trends are found in all seasons. In contrast, 10-m wind speed trends for IL in reanalysis data, a primary source of data for climate model validation and wind energy projection, are positive or show no trend in most grids that approximate IL station locations [1.28%–3.10% decade−1 for ERA5, NASA MERRA-2, and NCEP North American Regional Reanalysis (NARR)]. Some IL stations also show a significant shift to more southerly winds, indicating a greater influence of air masses originating from the Gulf of Mexico. This trend is also not captured by reanalysis data, despite accurate wind direction climatologies. Thus, model validation of regional wind should be performed cautiously with reanalysis data, and reliance on reanalysis wind data may lead to an overestimation of future IL wind speeds and wind power generation. Significance Statement Reanalysis data are used to validate climate models and for wind energy projection. The purpose of this study is to assess how well three widely used reanalysis products reproduce surface wind observations in Illinois, which ranks fifth in the country for wind power capacity. We found reanalysis data better reproduce wind direction than wind speed and tend to overestimate wind speeds. The station data show significant decreases in wind speeds and changes in wind direction, but those trends are not found in any of the reanalysis products studied here. This could lead to an overestimation of future wind energy generation and inaccuracies in wind in climate models. These results highlight the limitations of reanalysis data, which should be used cautiously.

Abstract Results are presented of a 3-day intensive observational period carried out during a wintertime air pollution episode in the Santiago Valley in central Chile. The objective was to characterize nonlocal factors of the convective boundary layer (CBL) and evening transition (ET), including advective effects and the possible role of internal waves. The principal measurements were performed with a mobile ceilometer that probed the fine vertical structure of aerosols along two ∼70-km paths designed to assess the horizontal variation of the CBL inside the valley and the meridional structure of complex ET aerosol layers documented by previous studies. Ancillary observations included four fixed ceilometers, 3-hourly radiosondes, one tethered balloon system, occasional pilot balloons, and two automatic meteorological stations measuring wind above the standard 10 m AGL height. The CBL showed a terrain-following mode of horizontal variation in the center of the valley and a growth rate affected by a surface-detached early morning warming. A minimum-advection (MA) estimate of the energy and water CBL budgets suggests a 3.2 Bowen ratio for the valley surface fluxes. The complex ET aerosol layers were associated with southerly winds that brought clean air to the center of the valley displacing the CBL residual layer. During one ET, intense wind and pressure oscillations were observed presumably related to an internal gravity wave, with significant effects in surface winds, stability, and turbulence. The observations enhanced the understanding of this complex terrain boundary layer and provided data for the validation of its numerical modeling.

Abstract The southerly monsoon surge (SMS) produces a large amount of extreme rainfall (ER) over the North China Plain (NCP). This study proposes a new perspective in which the thermal contrast between the NCP and Mt. Taihang to its west can enhance the southerlies in planetary boundary layer (PBL) during SMS episodes and thus plays an important role in the production of ER. Based on reanalysis data, this study finds 145 SMS episodes in 30 warm seasons from 1988 to 2017, during which the NCP encountered 66% of the ER. These episodes feature strong poleward transport of moisture in the PBL. The diabatic heating over Mt. Taihang produces strong low‐level baroclinicity, which together with synoptic forcing in the free atmosphere drives the strong PBL southerlies. The south wind components in PBL and in low troposphere are only moderately correlated, whereas their difference is closely related to the zonal temperature gradient. Based on convection‐permitting numerical simulations, this study further investigates the impacts of mountain‐plain thermal contrast on the production of ER during a 20‐day SMS episode in the summer of 2024. A sensitivity experiment reveals significantly weakened PBL southerlies and moisture transport over NCP when the PBL over Mt. Taihang is cooled by ∼1 K. The simulated ER amount is 38.7% less than that in the control experiment. Additional experiments indicate that the low‐level temperature over mountain modulates the diurnal variation of the PBL wind over plain via the Holton mechanism.

Abstract This study focuses on a series of long-lived atmospheric bores that persisted from midnight to the late afternoon on 10 June 2023 over the coastal and offshore regions of the Yellow Sea. These bores were sustained by a favorable trapping mechanism associated with the stability of the marine boundary layer and the presence of a low-level wind component perpendicular to the propagation direction of the bores. These bores aided in maintaining and enhancing convective systems offshore with outflows that reached inland and initiated new convective cells. These convective cells eventually organized to produce severe weather under favorable thermodynamic conditions. These findings underscore the unique atmospheric conditions over the Yellow/East China Sea that promote long-lived atmospheric bores during the day, which is a potential mechanism to cause severe convective systems over the coastal region of eastern China. The complex multiscale processes influencing the development of mesoscale convective systems during the mei-yu monsoon season over this region present unique challenges for their accurate representation especially in coarse-grid weather and climate models. Given the growing density of coastal populations, further research is needed into the frequency of bores generated by convection and their subsequent impact on coastal convection. Significance Statement This study links atmospheric bores over the Yellow/East China Sea to the generation of severe convection over the eastern coast of China. These offshore bores persisted well into the daylight hours with far longer lifetimes than their inland counterparts. This longevity was supported by the presence of a stable marine boundary layer and prevailing southerly winds associated with the sea breeze. These offshore bores influenced severe coastal daytime convection both directly and indirectly. This study reveals the complex characteristics of convective systems along the eastern coast of China. These findings underscore the need to incorporate offshore and coastal atmospheric measurements into operational forecasting and research activities.

Abstract An Observing System Simulation Experiment was conducted to assess the impact of assimilating oceanic wind profiles on the simulations of warm‐sector heavy rainfall along the South China coast. This rainfall event was strongly influenced by an upstream boundary layer jet (BLJ) over the northern South China Sea (NSCS). Using a 21‐member WRF ensemble initialized with Global Ensemble Forecast System data, the best‐performing member was selected as the nature run. Simulated wind profiles over the NSCS from the nature run were assimilated into the worst‐performing member at the initial time step, improving the representation of the BLJ structure and strength. The data assimilation experiments reveal a significant sensitivity of simulated rainfall intensity and spatial distribution to both the number and location of assimilated wind profile observations. A strengthened marine BLJ with a more southerly wind component extending toward the coast enhanced low‐level convergence, upward motion, and moisture transport at its terminus, thus creating a more favorable environment for convection. However, momentum budget analysis indicates that, despite wind profile assimilation, the nearshore BLJ remained too weak to sustain upscale convective growth following convective initiation.

The coastal sandy land in northeast Hainan Province is typical for this land type, also exhibiting strong sand activity. This study is based on wind speed, wind direction, and sediment transport data obtained at a field meteorological station using an omnidirectional sand accumulation instrument from 2020 to 2024, studying the coastal aeolian environment and sediment transport distribution characteristics in the region. Its findings provide a theoretical basis for comprehensively analyzing the evolution of coastal aeolian landforms and the evaluation and control of coastal aeolian hazards. The research results show the following: (1) The annual average threshold wind velocity for sand movement in the study area is 6.84 m/s, and the wind speed frequency (frequency of occurrence) is 51.54%, dominated by easterly (NE, ENE) and southerly (S, SSE) winds. (2) The drift potential (DP) refers to the potential amount of sediment transported within a certain time and spatial range, and the annual drift potential (DP) and resultant drift potential (RDP) of Mulan Bay from 2020 to 2024 were 550.82 VU and 326.88 VU, respectively, indicating a high-energy wind environment. The yearly directional wind variability index (RDP/DP) was 0.59, classified as a medium ratio and indicating blunt bimodal wind conditions. The yearly resultant drift direction (RDD) was 249.45°, corresponding to a WSW direction, indicating that the sand in Mulan Bay is generally transported in the southwest direction. (3) When the measured data extracted from the sand accumulation instrument in the study area from 2020 to 2024 were used for statistical analysis, the results showed that the total sediment transport rate (the annual sediment transport of the observation section) in the study area was 110.87 kg/m·a, with the maximum sediment transport rate in the NE direction being 29.26 kg/m·a. These results suggest that when sand fixation systems are constructed for relevant infrastructure in the region, the construction direction of protective forests and other engineering measures should be perpendicular to the net direction of sand transport.

Understanding the variability in material transport from the Taiwan Strait (TS) to the Korean Strait (KS) is crucial for predicting ecological changes and the spread of marine debris in the East Asian Marginal Seas (EAMS). However, the dynamic variability of this transport remains poorly understood. In this study, we investigated the dynamic variability of material transport from the TS to the KS, using a Lagrangian particle-tracking system coupled with a three-dimensional numerical model. The model results showed that particles originating from the TS most frequently passed through the KS in August, with distinct interannual variability. Our findings indicate that southerly winds enhance the sea surface height (SSH) gradient in the southwestern East China Sea (ECS) shelf region through surface Ekman transport, weakening cross-shelf offshore currents and preventing particles from being transported offshore. The interannual variability of southerly winds is associated with variations in SSH in the southwestern shelf region, thereby modulating material transport from the TS to the KS. Furthermore, southerly winds over the EAMS are found to strengthen during negative phases of the Pacific Decadal Oscillation, suggesting a potential linkage between material connectivity in the EAMS and large-scale climate indices. These findings reveal how physical processes govern material transport in the EAMS, offering valuable insights into the prediction of nutrient fluxes and pollutant dispersion.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-13861-z.

Abstract. In the summer of 2022, atmospheric conditions characterized by persistent anticyclonic anomalies caused an extreme marine heatwave in the western Mediterranean Sea. Time series of temperature profiles at various points along the northeastern coast of the Gulf of Lion (NW Mediterranean Sea) showed exceptional temperatures down to depths of 30 m, which led to massive mortality of benthic species. A hydrodynamic numerical simulation was used to analyze the physical processes responsible for this subsurface heatwave in a region where the climatology in summer is characterized by northerly winds inducing upwelling alternating with low winds. Firstly, the recurrence of heatwaves limited to the surface was demonstrated, triggered when upwelling stopped and warm water from the Northern Current intruded onto the shelf. More importantly, in August and early September 2022, two episodes of southerly and easterly winds of 8 to 10 m s−1 occurred. The oceanic response to these winds was an alongshore cyclonic current advecting warm water onto the shelf and a downwelling of this warm water to depths of the order of 30 to 40 m. A large part of the Gulf of Lion coast was warmed by these events. However, the northeastern part of the shelf, on either side of the city of Marseille, was by far the area most affected at depth due to the combination of the proximity of the warm surface waters of the Ligurian coast advected by wind-induced currents and the local acceleration of the wind by the continental topography, which intensifies the downwelling of these surface waters. These events are rare in summer, but their impact on the rich benthic ecosystems that characterize the region is dramatic and will only increase with the warming trend in surface waters, which is already close to 1 °C, as seen over the last decade.