Atmospheric Research最新文献

{"title":"Evaluating microphysics scheme impacts on summer precipitation in Northwestern China using a convection permitting WRF model","authors":"Ya Huang ,&nbsp;Qingyun Duan ,&nbsp;Yong Zhao ,&nbsp;Lihua Chen ,&nbsp;Yanping Li","doi":"10.1016/j.atmosres.2025.108691","DOIUrl":"10.1016/j.atmosres.2025.108691","url":null,"abstract":"<div><div>Microphysics parameterization strongly influences precipitation formation in numerical weather and climate models. This study evaluates three double moment microphysics schemes in the convection permitting WRF ARW model, including Jensen ISHMAEL (JIS), Thompson (TH), and WRF Double Moment 7 class (WDM7), for summer precipitation over Northwestern China using a 4 km simulation for 2009 to 2011. The evaluation, based on IMERG satellite data and surface observations, focuses on spatial distribution, diurnal cycle, hydrometeor structure, and thermodynamic conditions. All three schemes reproduce the major precipitation bands along the Tianshan, Qilian, and Kunlun Mountains, though with wet biases at high elevations and dry biases in the Tarim and Qaidam Basins. For diurnal variations, all schemes capture the characteristic double-peak cycle, with WDM7 providing the most accurate peak timing, TH performing moderately, and JIS showing a delayed, overly strong afternoon peak. Hydrometeor analysis shows that JIS and TH generate deeper, more continuous ice-phase layers in the mid- to upper troposphere, supporting persistent precipitation development. WDM7 produces noticeably weaker mid-level ice content, limiting sustained ice-phase growth. Thermodynamic responses indicate that JIS and TH modify local instability and moisture through stronger latent heating feedbacks, whereas WDM7 exhibits lower atmospheric moisture and instability and a higher lifting condensation level, creating conditions less favorable for deep convection. Among the three schemes, WDM7 exhibited the smallest wet bias and most effectively reduces the overestimation of mountain precipitation present in the JIS and TH simulations. These findings highlight the importance of microphysics selection for improving high resolution precipitation simulation over complex terrain.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"333 ","pages":"Article 108691"},"PeriodicalIF":4.4,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The climatology of complexity: Spatiotemporal analysis of summer subtropical anticyclones over Southwest Asia and adjacent regions","authors":"Morteza Keyhani,&nbsp;Abbas Mofidi,&nbsp;Azar Zarrin","doi":"10.1016/j.atmosres.2025.108713","DOIUrl":"10.1016/j.atmosres.2025.108713","url":null,"abstract":"<div><div>This study provides a comprehensive climatology of summer subtropical anticyclones (SAs) over Southwest Asia using daily ERA-Interim geopotential height data (1990–2019) across six pressure levels (900–100 hPa). Anticyclones were identified on 2760 summer days using combined objective and subjective methods, enabling a multi-level assessment of their frequency, spatial organization, preferred locations, vertical structure, seasonal evolution, and long-term variability. SAs are found throughout the atmospheric column, with maximum frequencies in the mid-troposphere and minimum occurrences near the surface. Distinct spatial modes emerge at different levels—bimodal at 500 hPa, trimodal at 700 hPa, and quadrimodal at 100–200 hPa—revealing finer spatial complexity than earlier climatologies. A key finding is a pronounced vertical seesaw pattern in seasonal occurrence: lower-tropospheric anticyclones peak in June but decline sharply in July, while mid- and upper-tropospheric anticyclones intensify. This indicates a coordinated vertical redistribution of anticyclonic activity during summer. Interlevel relationships exhibit strong coherence in the upper troposphere, whereas weaker correlations between adjacent lower and mid-tropospheric levels suggest level-dependent formation mechanisms and vertical tilt. Regionally, the study refines the characteristics of the Turkmenistan, Zagros, and Arabian anticyclones, highlighting the vertical continuity of the Arabian anticyclone and its sensitivity to surface thermal forcing. Long-term analysis reveals no significant meridional shifts but shows a notable increase in anticyclone frequency at 700 hPa, likely linked to recent warming over the Arabian Peninsula. Overall, the findings demonstrate the dynamical complexity of SAs across Southwest Asia and provide an updated framework for understanding their variability and climate relevance.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"333 ","pages":"Article 108713"},"PeriodicalIF":4.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the boreal spring arctic oscillation on the midsummer maritime continent precipitation","authors":"Yining Tao ,&nbsp;Gang Zeng ,&nbsp;Chen Chen ,&nbsp;Aminu Dalhatu Datti ,&nbsp;Zhongxian Li","doi":"10.1016/j.atmosres.2025.108730","DOIUrl":"10.1016/j.atmosres.2025.108730","url":null,"abstract":"<div><div>The Arctic Oscillation (AO), the dominant mode of extratropical Northern Hemisphere circulation, is known to influence midlatitude climate variability, but its impacts on tropical rainfall–particularly over the Maritime Continent (MC)–remain unclear. Here, we examine the influence of the boreal spring AO on midsummer (July–August) MC precipitation during the period 1979–2023. The results reveal a significant negative relationship between midsummer MC precipitation and the preceding March–April AO. Further examination identifies a physical mechanism linking the two: during the negative phase of the March–April AO, atmosphere–ocean interactions generate warm sea surface temperature (SST) anomalies in the North Atlantic that persist from March to August. These mid–latitude SST anomalies in the North Atlantic trigger an atmospheric wave train that propagates from the North Atlantic to the North Pacific, ultimately inducing pronounced westerly wind anomalies in the upper troposphere and easterly wind anomalies in the lower troposphere over the tropical western Pacific in July–August. This circulation pattern enhances vertical wind shear, promoting anomalous ascent via dynamic pumping and increasing rainfall. Simulations using the Community Atmosphere Model (CAM5.3) further validate the proposed mechanism.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"333 ","pages":"Article 108730"},"PeriodicalIF":4.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145823513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tropical easterly waves in the North Atlantic basin and their precipitating moisture sources: Insights from a downscaled climatological analysis","authors":"Orlando L. Córdova-García ,&nbsp;Ricardo M. Trigo ,&nbsp;Raquel Nieto ,&nbsp;Luis Gimeno ,&nbsp;Rogert Sorí ,&nbsp;Milica Stojanovic ,&nbsp;Albenis Pérez-Alarcón","doi":"10.1016/j.atmosres.2025.108727","DOIUrl":"10.1016/j.atmosres.2025.108727","url":null,"abstract":"<div><div>Tropical easterly waves (TEWs) play a key role in rainfall variability and act as precursors to tropical cyclones in the North Atlantic. However, the origin of TEW-related precipitation remains insufficiently explored. This study presents a 39-year (1985–2023) climatology of TEWs using a curvature vorticity-based tracking method applied to a downscaled ERA5 dataset, combined with a Lagrangian moisture source analysis. An average of 41 ± 5 TEWs per year is identified, with a pronounced peak during July–September. TEWs propagate westward at approximately 8 m/s, with the highest activity across the main development region of tropical cyclones. TEWs account for 1–7 % of annual rainfall across the basin, with peaks spatially coinciding with areas of highest wave activity. Moisture source diagnostics reveal three distinct TEW regimes. Near the African coast, moisture is primarily derived from the eastern tropical Atlantic and continental Africa, whereas waves in the central Atlantic and Caribbean region increasingly rely on long-distance zonal transport from the eastern and central tropical Atlantic, consistent with the wave lifecycle. The analysis also reveals the trade and easterly winds as the primary moisture transport mechanisms, while area-average moisture uptake and associated precipitation show no statistically significant positive long-term trends. Meanwhile, the mean water vapour residence time for TEW-related precipitation is about 3.6 days, slightly longer than for tropical cyclones. This study extends previous climatologies and contributes to enhancing the understanding of TEW-related hydroclimate processes in the tropical North Atlantic.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108727"},"PeriodicalIF":4.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145813834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Winter PM2.5 pollution in China's largest arid urban agglomeration: Impacts of basin terrain and synoptic-scale circulations","authors":"Qian Liang ,&nbsp;Yucong Miao ,&nbsp;Yan Yan ,&nbsp;Shuhua Liu","doi":"10.1016/j.atmosres.2025.108728","DOIUrl":"10.1016/j.atmosres.2025.108728","url":null,"abstract":"<div><div>Severe wintertime PM_2.5 pollution persists in the Urumqi–Changji–Shihezi urban agglomeration, China's largest arid-region urban cluster, despite emission controls that have improved air quality in eastern China. Using air quality monitoring data, radiosonde observations, and chemical transport model simulations for two winters (2022–2024), we investigated the combined roles of synoptic-scale circulation and basin terrain in modulating pollutant accumulation. Results show that PM_2.5 pollution exhibits strong spatial synchrony among Urumqi, Changji, and Shihezi, indicating dominant regional meteorological control beyond local emissions. Stagnant westerly circulation with warm advections aloft fosters persistent cold-air pool within the Junggar Basin, producing strong thermal inversions, shallow boundary layers, and PM_2.5 accumulation in the urban agglomeration. In contrast, Siberian cold surges and northwesterly flows channel cold air through low-elevation gaps on the basin's north and west margins, weakening stratification, enhancing surface winds via horizontal and partial downward momentum transport, and deepening the boundary layer, which promotes pollutant dispersion. These findings highlight the critical interplay between large-scale forcing and complex terrain in controlling air quality in arid basins and provide a scientific basis for improved forecasting and targeted mitigation strategies.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108728"},"PeriodicalIF":4.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145813835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relative contribution of extreme and non-extreme rainfall to seasonal precipitation over Northwest India and the underlying mechanisms","authors":"Bhargavi Veesam,&nbsp;Jasti S Chowdary,&nbsp;C. Gnanaseelan","doi":"10.1016/j.atmosres.2025.108711","DOIUrl":"10.1016/j.atmosres.2025.108711","url":null,"abstract":"<div><div>This study assesses the contributions of extreme and non-extreme rainfall events to seasonal precipitation over Northwest India (NWI) and examines the underlying dynamical mechanisms. Our analysis reveals a notable increase (10 %) in overall seasonal rainfall of NWI during 2000–2023 period relative to 1971–2000. In addition, we also found that extreme rainfall events (EREs; R90s) have contributed more than 75 % of the total seasonal rainfall over majority of NWI, with some regions (Punjab, Haryana, Rajasthan and Gujarat) extending the contributions beyond 90 %. Our comprehensive analysis reveals large scale atmospheric circulation as the key driver during EREs. Specifically, the Rossby wave induced trough elongation from Europe played a dominant role and is modulated by the negative configuration of the East Asian Polar and Subtropical Jet streams, which eventually facilitated downstream propagation. The resulting wave pattern featured an amplified barotropic ridge over the North Pacific, a distorted positive phase of the Pacific-North American (PNA) pattern, and a ridge (trough) over North Atlantic Ocean and Europe. This European trough slowly descended from upper to lower levels, elongated and merged with the pre-existing low over NWI. Such synoptic configuration enhanced the moisture transport from the equatorial Indian Ocean and Arabian Sea into NWI by strengthening the low-level jet and sustaining deep convection, leading to rainfall extremes. In concordance, the features of CAPE, Cloud base heights, Low level Cloud liquid water content, enhanced convergence and Moist Static Energy underscore the dominance of vigorous convective precipitation over NWI in the post 2000 period. These findings have severe implications for hydrological and ecological sectors.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108711"},"PeriodicalIF":4.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the SM2RAIN-ASCAT dataset in Morocco: Accuracy evaluation and drought monitoring application","authors":"Said El Goumi ,&nbsp;Mustapha Namous ,&nbsp;Abdenbi Elaloui ,&nbsp;Samira Krimissa ,&nbsp;Nasem Badreldin ,&nbsp;Sakine Koohi ,&nbsp;Nafia El Alaouy ,&nbsp;El Houssaine Bouras","doi":"10.1016/j.atmosres.2025.108729","DOIUrl":"10.1016/j.atmosres.2025.108729","url":null,"abstract":"<div><div>SM2RAIN-ASCAT, a bottom-up satellite-based precipitation product, has been increasingly used for drought monitoring due to its ability to estimate rainfall from soil moisture data. To determine its suitability for precipitation estimation and drought monitoring in Morocco, this study compares SM2RAIN-ASCAT dataset with observed data from 36 ground-based stations. This analysis examines the performance of the satellite product in a variety of climate zones across the country. The accuracy of the precipitation dataset was assessed using a suite of quantitative and qualitative metrics validated against observations. For the purpose of drought monitoring, the Standardized Precipitation Index (SPI) was calculated at 1, 3, 6, and 12 month timescales. To evaluate the performance of the product, the evaluation was also stratified by climate zone. The mean correlation coefficient (CC) with ground observations strengthened from 0.45 (daily) to 0.67 (monthly), with monthly and 10 days aggregations providing the most consistent performance. The dataset had a high probability of detecting rain events, with a monthly Probability of Detection (POD) exceeding 0.75 for 89% of stations. While the product showed a tendency to underestimate intense rainfall, the relative bias was low at nearly half of the stations, and the lowest RMSE value was found at monthly scale. With an underestimation of precipitation in Mediterranean regions and an overestimation in arid regions of Morocco, the product exhibits climatic bias; yet, its efficacy for drought monitoring has been proven. The calculated SPI values for short to medium-term durations (1, 3, 6 and 12 months) align well with ground observations across several climate zones in Morocco. While the 1 month SPI shows only weak to moderate agreement with gauge data, the correlation strengthens markedly for 3 and 6 month periods, with a CC of approximately 0.70 and 0.80, respectively. Notably, the results for long-term hydrological drought monitoring (SPI-12) are particularly promising, demonstrating excellent agreement with ground observations across nearly all stations. SM2RAIN-ASCAT is a reliable option for drought analysis in many arid regions like Morocco, it excels at detecting droughts in arid zones over humid ones, and similarly, it performs highly at identifying wet periods in hot arid climates than in wetter zones. Finding show that the integration of bottom-up (SM2RAIN) and top-down approaches can improve precipitation and drought monitoring performance, compensating for the limitations of each method. Overall SM2RAIN-ASCAT product is particularly recommended for agricultural drought monitoring and water management.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108729"},"PeriodicalIF":4.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145796304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Altitude-resolved O3 transport in the Beijing-Tianjin-Hebei region: A multi-scenario analysis of extreme meteorology and pollution gradients","authors":"Hanyu Zhang ,&nbsp;Jungang Wang ,&nbsp;Maofa Ge ,&nbsp;Shengrui Tong ,&nbsp;Hailiang Zhang ,&nbsp;Zhiliang Yao","doi":"10.1016/j.atmosres.2025.108721","DOIUrl":"10.1016/j.atmosres.2025.108721","url":null,"abstract":"<div><div>Tropospheric ozone (O₃) pollution is an emerging challenge in the Beijing-Tianjin-Hebei region, where extreme meteorology and multiple pollution gradients frequently occurred. However, altitude-dependent structure of O₃ transport under such conditions has been rarely quantified. Here, we resolved horizontal and vertical O₃ fluxes in Beijing, Tianjin and Shijiazhuang across favorable/unfavorable meteorology, heatwaves, and varying pollution gradients through WRF-CAMx models. Results revealed strong spatial autocorrelation for O₃ across “2 + 36” Chinese cities (Moran's I: 0.21–0.77), with pronounced clustering in autumn and winter. Dominant southwest-northeast corridors were identified, with episodic cross-sea inflows to Tianjin, contributing 12.1 %–21.5 % of total inflow. Horizontal inflow and outflow fluxes peaked on pollution days (e.g., exceeding 44 kt/d in Beijing) and bottomed on excellent days (e.g., 28.8 kt/d in Beijing), while net fluxes showed the opposite trend, ranging from 0.4 to 5.3 kt/d. Vertically, upward fluxes maximized during pollution days, with Beijing transitioning from a net “sink” (−24.0 to −55.7 kt/d in non-pollution scenarios) to a “source” (46.7–85.5 kt/d on pollution days), whereas Tianjin and Shijiazhuang consistently acted as a “source”. Furthermore, the vertical distribution of the horizontal and vertical net fluxes showed significant differences across scenarios, and the altitude at which the maximum flux occurs also varied with scenarios. Severe pollution episode analysis demonstrated the altitude-dependent and city-specific interplay between transport and photochemistry in driving episodic O₃ extremes. These findings refine understanding of how altitude-scenario interactions shape O₃ dynamics, supporting the coordinated control strategies.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108721"},"PeriodicalIF":4.4,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145796305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of nonlinear convection–SST sensitivity in shaping the southward displacement of westerly anomalies during El Niño peak phase","authors":"Jingwen Sun ,&nbsp;Jianing Lu ,&nbsp;Yifan Jia ,&nbsp;Ruihuang Xie","doi":"10.1016/j.atmosres.2025.108712","DOIUrl":"10.1016/j.atmosres.2025.108712","url":null,"abstract":"<div><div>This study investigates the southward displacement of anomalous westerlies over the central equatorial Pacific during El Niño peak phase, using ERA5 reanalysis and long-term simulations from UKESM1.0-LL. The analysis reveals that this displacement is anchored by the seasonal migration of the tropical warm pool, thereby enhancing convection sensitivity to sea surface temperature (SST) south of the equator. The spatial structure and intensity of the westerly anomalies are further regulated by the nonlinear convection–SST relationship, with sensitivity peaking within the 27°–29 °C high SST range. Observation shows that, prior to 2000, stronger El Niño events produced more intense and spatially extensive southward-displaced westerly anomalies, whereas since the early 21st century, a La Niña–like mean-state change has weakened the convection–SST sensitivity and reduced the magnitude and extent of the westerly anomalies. Similar relationships among southward-displaced westerly anomalies, El Niño amplitude and convection-SST sensitivity were reproduced in UKESM1.0-LL model. Building on these findings, a synergistic framework is proposed, in which El Niño amplitude sets the scale of SST anomaly forcing, convection–SST sensitivity modulates the convective response, and the warm pool background constrains the spatial location of convection and associated wind anomalies. This thermodynamic mechanism complements existing dynamical explanations and highlights the role of convection–SST sensitivity in shaping El Niño-induced wind responses.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"332 ","pages":"Article 108712"},"PeriodicalIF":4.4,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence of the linkage between mesoscale eddy activity in the Bay of Bengal and Indian Summer Monsoon Rainfall","authors":"V.G. Kiran ,&nbsp;Suryachandra A. Rao ,&nbsp;Prasanth A. Pillai ,&nbsp;Rajesh Kumar Singh Maurya ,&nbsp;Ankur Srivastava ,&nbsp;Maheswar Pradhan","doi":"10.1016/j.atmosres.2025.108708","DOIUrl":"10.1016/j.atmosres.2025.108708","url":null,"abstract":"<div><div>The mesoscale eddies present in many dynamic regions of the world ocean are known to modulate wind and precipitation in their vicinity. This study investigates the observed association between eddy activity in the western Bay of Bengal and seasonal rainfall over the monsoon core region during the boreal summer. A novel method is employed to characterise eddy variability in the Bay of Bengal using the Okubo-Weiss (OW) parameter. The anticyclonic (cyclonic) eddy activity in the western Bay correlates with increased (decreased) monsoon rainfall and westerly (easterly) wind anomalies across the monsoon core zone. During years when BoB is dominated by anticyclonic eddies, the seasonal Indian summer monsoon rainfall (ISMR) in this region exceeds the climatological mean by up to 35 % of its standard deviation. A mechanism linking the anticyclonic eddies and the ISMR is proposed here based on the observational data for the 1993–2022 period. The presence of anticyclonic eddies appears to mitigate the detrimental effects of El Niño on east-central Indian rainfall by fostering atmospheric conditions favourable for monsoon low-pressure system formation. Furthermore, years dominated by anticyclonic eddies exhibit a stronger, narrow coastal SST gradient in the northwestern Bay of Bengal, which may further enhance LPS development.</div><div>Methodically structured model sensitivity experiments using a standalone atmospheric model substantiate the impact of mesoscale SST structures and the coastal gradient in the BoB on rainfall, thus providing potential evidence regarding the interplay between eddies and the Indian monsoon system.</div></div>","PeriodicalId":8600,"journal":{"name":"Atmospheric Research","volume":"333 ","pages":"Article 108708"},"PeriodicalIF":4.4,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145785331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}