Journal of Geophysical Research: Atmospheres最新文献

{"title":"Machine Learning-Based Estimation of Clear-Sky Direct Aerosol Radiative Forcing Using Multisensor Satellite Observations","authors":"Lu Zhang,&nbsp;Jing Li,&nbsp;Yueming Dong,&nbsp;Tong Ying,&nbsp;Zhenyu Zhang,&nbsp;Guanyu Liu,&nbsp;Chongzhao Zhang","doi":"10.1029/2024JD043170","DOIUrl":"https://doi.org/10.1029/2024JD043170","url":null,"abstract":"<p>Aerosol forcing remains highly uncertain in climate change assessment. Observation-based forcing estimates have been typically given more weight as they do not rely on assumptions and parameterizations in models. Traditional estimation of direct aerosol radiative forcing (DARF) based on observation is realized by regressing the observed radiative fluxes against aerosol optical depth (AOD). Here we improve this procedure by considering more aerosol parameters such as single scattering albedo (SSA) and adopting a machine learning-based method (eXtreme Gradient Boosting (XGBoost)) to establish the relationship between top-of-atmosphere (TOA) radiative fluxes and aerosol properties. Our approach gives a global mean DARF of −0.80 ± 0.73 W/m² under clear sky, which largely agrees with previously reported results. The DARF uncertainty includes the impact of measurement errors and the XGBoost model, in which AOD and SSA uncertainties cause ∼0.66 and ∼0.14 W/m² changes in the DARF respectively.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144563439","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":"Wildfire Smoke Shading Observations: Impacts on Boundary Layer Mixing and Thermally Driven Smoke Transport","authors":"Brian J. Carroll,&nbsp;Edward Strobach,&nbsp;Sunil Baidar,&nbsp;Maxwell W. Holloway,&nbsp;Brandi McCarty,&nbsp;Richard Marchbanks,&nbsp;W. Alan Brewer","doi":"10.1029/2024JD043303","DOIUrl":"https://doi.org/10.1029/2024JD043303","url":null,"abstract":"<p>Smoke shading from wildfire smoke cools the surface and atmosphere below the smoke by absorbing and scattering sunlight. This has the potential to create meteorological feedback and large air quality impacts, but observations of smoke shading and induced local flows are rare. Mobile truck-based Doppler lidar observations during the California Fire Dynamics Experiment (CalFiDE) in August and September 2022 provide a novel data set of smoke shading events. The truck-based lidar conducted measurements of horizontal and vertical winds while underway, along with qualitative smoke backscatter, allowing a study of boundary layer (BL) dynamics in and out of the smoke shaded areas. An in situ temperature sensor on the truck recorded air temperature. Smoke shaded versus clear-sky temperature differences of up to 8°C were observed over 12 km along a valley floor in complex terrain. Using vertical velocity variance as a measure of turbulent mixing, smoke shading reduced BL mixing by up to two orders of magnitude, preventing the development of an afternoon convective BL in some cases. Temperature gradients also resulted in thermally driven flows wherein the cold smoky air mass undercut warmer ambient air. One density current case was observed with a strong opposing flow resulting in a convergent updraft and shear-induced vortices atop the smoke-filled density current. In another case, the flow was impeded by complex terrain resulting in a slower-moving smoke front and a temperature gradient that lagged behind the front.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD043303","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144558188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impacts of Heatwaves on Characteristics of Atmospheric Methylglyoxal in a Suburban Area in Eastern China","authors":"Haoyu Liu,&nbsp;Tengyu Liu,&nbsp;Yuanyuan Li,&nbsp;Aoqi Ge,&nbsp;Lei Wang,&nbsp;Shiyi Lai,&nbsp;Guangdong Niu,&nbsp;Junchao Yin,&nbsp;Xueyu Zhou,&nbsp;Yuliang Liu,&nbsp;Jiaping Wang,&nbsp;Qiaozhi Zha,&nbsp;Ximeng Qi,&nbsp;Wei Nie,&nbsp;Xuguang Chi,&nbsp;Sijia Lou,&nbsp;Xin Huang,&nbsp;Yanli Zhang,&nbsp;Wei Song,&nbsp;Xinming Wang,&nbsp;Aijun Ding","doi":"10.1029/2025JD044284","DOIUrl":"https://doi.org/10.1029/2025JD044284","url":null,"abstract":"<p>Methylglyoxal (Mgly) is a ubiquitous yet poorly constrained atmospheric volatile organic compound significantly contributing to the formation of ozone and secondary organic aerosols. Global warming increases heatwaves frequency, affecting sources and sinks of Mgly. Thus, studies on Mgly observations during heatwaves become increasingly urgent. Here, we combined field measurements using Vocus proton transfer reaction time-of-flight mass spectrometry (Vocus PTR-ToF-MS), box model, and the Weather Research and Forecasting model with Chemistry (WRF-Chem) to investigate the impacts of heatwaves on Mgly at a suburban site in eastern China during a prolonged heatwave influenced summer in 2022. After verifying that Vocus PTR-ToF-MS accurately detects Mgly and eliminating ion fragmentation artifacts of isoprene, we discovered that the heatwave doubled Mgly concentrations. This was attributed to a significant rise of isoprene—the dominant precursor of Mgly as confirmed by box modeling. The heatwave also altered photolysis and oxidation of Mgly and emission characteristics of isoprene, leading to an earlier peak and then a sudden drop of Mgly in the morning. This was different from the consistent peaks with air temperatures observed during non-heatwave period. The concentrations of Mgly and isoprene showed positive correlations with air temperatures below 33°C, whereas both species' concentrations decline as temperatures exceeded 35°C. Additionally, WRF-Chem underestimated isoprene and slightly overestimated Mgly. It could not capture the trends of Mgly and the discrepancies between model and measurements exacerbated when heatwave occurred. This study highlights the significant impact of heatwaves on Mgly and provides a benchmark for future model optimization.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550926","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":"Carbon Sink of Terrestrial Ecosystems in China During 2010–2020: Spatiotemporal Variability and Climate Impact","authors":"Nanhong Xie,&nbsp;Tijian Wang,&nbsp;Min Xie,&nbsp;Danyang Ma,&nbsp;Qian Zhang,&nbsp;Mengmeng Li,&nbsp;Shu Li,&nbsp;Bingliang Zhuang,&nbsp;Ume Kalsoom,&nbsp;Natalya Andreeva Kilifarska,&nbsp;Georgi Gadzhev,&nbsp;Reneta Dimitrova,&nbsp;Dimitrios Melas,&nbsp;Kostas Karatzas","doi":"10.1029/2025JD043405","DOIUrl":"https://doi.org/10.1029/2025JD043405","url":null,"abstract":"<p>Carbon neutrality in China can be achieved through maintained and improved terrestrial carbon sinks. However, the impact of climate change on the carbon cycle remains unclear. Here, we assess the spatiotemporal dynamics of net ecosystem productivity (NEP) in China's terrestrial ecosystems from 2010 to 2020 and its response to climate change using the regional climate-chemistry-ecology coupled model RegCM-Chem-YIBs. The estimations demonstrate that the national annual average NEP was 399.08 TgC yr⁻¹ and increased by 8.83 TgC yr⁻¹, effectively offsetting 15.4% of industrial carbon emissions. The NEP decreased gradually from southeast to northwest, with the maximum occurring in the southwest (122.31 TgC yr⁻¹); the NEP intensity peaked in summer (102.31 gC m⁻² yr⁻¹). Climate change positively contributed to NEP (11.2 TgC yr⁻¹), with significant interannual and regional differences. Precipitation anomalies in the southern region are the main meteorological factor for the interannual fluctuation of NEP. The increase in radiation led to an increase in NEP of 4.85 TgC yr⁻¹ and dominated 46.49% of the region in China. The increase in NEP in the southern region was attributed to enhanced radiation, while the northern region benefited from increased precipitation and rising temperatures. These findings highlight the significant spatiotemporal variations in the impact of climate change on the carbon sinks of terrestrial ecosystems in China. It is essential to account for the effects of climate change and to adopt differentiated strategies to enhance carbon sinks during policy formulation.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536963","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":"Prioritizing Urban Emission Reductions to Mitigate Pollution and Health Effects of Ozone and Nitrogen Dioxide in China","authors":"Zhaolei Zhang,&nbsp;Wenxuan Yu,&nbsp;Shuai Wang,&nbsp;Xinyue Li,&nbsp;Xia Meng,&nbsp;Peng Wang,&nbsp;Hongliang Zhang","doi":"10.1029/2024JD042831","DOIUrl":"https://doi.org/10.1029/2024JD042831","url":null,"abstract":"<p>Despite significant reductions in fine particulate matter (PM_2.5) concentrations in China due to air pollution control measures, ozone (O₃) pollution has worsened in recent years, with pronounced regional disparities in long-term exposure to O₃ and NO₂. Assessing these disparities in exposure to gaseous pollutants and the resulting unequal health risks between urban and rural regions has become increasingly essential. The contributions of various anthropogenic emissions to O₃ and NO₂ were quantified using a source-oriented version of the Community Multiscale Air Quality (CMAQ) model, combined with population and GDP data sets. From 2010 to 2019, NOx and VOC emissions from non-urban areas decreased by 14% and 25%, respectively, whereas urban anthropogenic activities caused a 10% increase in NOx emissions and a 22% rise in VOC emissions. The simulations indicated that background levels constituted the majority of maximum daily 8-hr average O₃ (MDA8 O₃), contributing 83% in 2010 and 75% in 2019. Non-urban anthropogenic activities were the primary sources of NO₂, accounting for 64% in 2010 and 57% in 2019. The proportion of O₃ and NO₂ from urban anthropogenic emissions in the total concentration continuously increased between 2010 and 2019. Although overall O₃-related premature mortality increased by 51% and NO₂-related premature mortality decreased by 3% during this period, the number of premature mortalities related to O₃ and NO₂ from urban anthropogenic activities rose by 133% and 15% respectively. We underscore the critical need to prioritize the reduction of urban anthropogenic emissions to effectively mitigate O₃ and NO₂ pollution in China.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144550948","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":"Analysis of High-Ozone Episodes Using a Chemical Metric Based on the Reactivities of Organic Precursors","authors":"Duy-Hieu Nguyen,&nbsp;Hsin-Cheng Hsieh,&nbsp;Sheng-Po Chen,&nbsp;Chang-Feng Ou-Yang,&nbsp;Chih-Chung Chang,&nbsp;Wen-Tzu Liu,&nbsp;Chieh-Heng Wang,&nbsp;Jia-Lin Wang","doi":"10.1029/2025JD043921","DOIUrl":"https://doi.org/10.1029/2025JD043921","url":null,"abstract":"<p>This study examines high-ozone episodes in an urban area of northern Taiwan influenced by local photochemical processes and transboundary pollution from the Asian continent. Long-term data sets from Photochemical Assessment Monitoring Stations and Air Quality Monitoring Stations were used to develop a photochemical metric based on volatile organic compounds ratios. We analyzed the ratio of ln(n-butane/ethane) versus ln(n-pentane/ethane) based on which we derived the <i>δ</i> value to assess the degree of regional air mass aging from a chemical reactivity perspective. In summer, extreme ozone events with low <i>δ</i> values are primarily driven by local photochemical activity. However, in fall and spring, the slightly higher <i>δ</i> values in some episodes signify the involvement of long-range transport (LRT) bringing in continental ozone and cooler air masses while local photochemistry remains active. The interaction between transported and locally produced ozone is pronounced during milder ozone episodes (100–120 ppbv). We further examined the <i>m,p</i>-xylene/ethylbenzene ratio as a complementary chemical indicator for characterizing ozone events with mild LRT. Slightly lower temperatures (below 28.8°C) are often accompanied by elevated nocturnal ozone levels (40–80 ppbv) and a less defined <i>m,p</i>-xylene/ethylbenzene ratio. Overall, high-ozone episodes (≥100 ppbv) are primarily driven by local photochemical processes. However, LRT can elevate the ozone baseline, particularly during spring and fall, when aged air masses bring in residual ozone leading to increased daytime ozone levels. These findings highlight how local photochemistry and regional transport shape high-ozone episodes emphasizing the value of chemical indicators for understanding air mass aging and ozone formation.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536965","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":"Emerging Constraints on the H2 Budget From Polar Firn Air Reconstructions","authors":"John D. Patterson,&nbsp;Eric S. Saltzman,&nbsp;Fabien Paulot","doi":"10.1029/2025JD043662","DOIUrl":"https://doi.org/10.1029/2025JD043662","url":null,"abstract":"<p>Comparison of modeled atmospheric hydrogen (H₂) levels with observations is an important way of testing the scientific understanding of H₂ biogeochemistry. But the instrumental record is short and provides a limited dynamic range with which to test assumptions about H₂ cycling. Here, we compare twentieth century H₂ levels reconstructed from polar firn air to the output from a historical run of the Geophysical Fluid Dynamics Laboratory Atmospheric Model 4.1 (GFDL-AM4.1). Simulated H₂ exhibits reasonable agreement with the reconstruction. The twentieth century increase in H₂ levels is consistent with rising atmospheric methane levels and changing emissions from fossil fuel combustion. However, the model fails to capture the reconstructed reversal in the interpolar H₂ gradient between 1960 and 1990. We invert an 8-box model of the atmosphere to show that the reversal in the interpolar difference requires a large increase (decrease) in the simulated NH (SH) net source of H₂ peaking circa 1980. Revisions to our estimates of historical biomass burning emissions, photochemical production, and/or anthropogenic emissions could help resolve the discrepancy. Our optimization also implies a 15% increase in the strength of the soil sink in the NH mid to high-latitudes from 1970 to 2000, which is qualitatively consistent with expectations based on changing soil moisture and temperature. We also show that smaller adjustments to the H₂ budget would be needed to explain the reversal in the interpolar gradient if the H₂ deposition lifetime were shorter than commonly accepted. A shorter lifetime may be supported by recently identified geological sources of H₂.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536964","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 Regional Climate Trends in West Africa Under Geoengineering: A Multimodel Comparison of UKESM1 and CESM2","authors":"Francis Nkrumah,&nbsp;Kwesi A. Quagraine,&nbsp;Gandome Mayeul Leger Davy Quenum,&nbsp;Daniele Visioni,&nbsp;Hubert A. Koffi,&nbsp;Nana Ama Browne Klutse","doi":"10.1029/2024JD043117","DOIUrl":"https://doi.org/10.1029/2024JD043117","url":null,"abstract":"<p>This study investigates West Africa's climate vulnerability under stratospheric aerosol injection (SAI), using UKESM1 and CESM2 models. We analyzed temperature and precipitation responses for 2050–2069 relative to 2015–2034 under SSP2-4.5 and ARISE-SAI-1.5 scenarios. Our approach involved evaluating temperature and precipitation anomalies, applying signal-to-noise ratio (SNR) analysis—defined as the ratio of the forced climate response to internal variability—to assess signal robustness, and using cumulative distribution (CDF) and probability density (PDF) functions to explore shifts in precipitation extremes. Results indicate that under SSP2-4.5, both models project significant warming. UKESM1 simulates increases near 1.8°C, while CESM2 projects between 1.0°C and 1.2°C. Under ARISE-SAI-1.5, UKESM1 shows pronounced cooling, with temperatures dropping up to 0.3°C below the reference period at some latitudes. CESM2 shows a more uniform cooling, with temperatures between 0°C and 0.3°C above the reference. SNR analysis reveals robust, statistically significant temperature changes across the region, clearly emerging above natural variability by midcentury. Precipitation changes, however, show lower SNR values and greater spatial uncertainty, suggesting weaker and less predictable hydrological responses. CDF and PDF analyses highlight complex shifts in precipitation extremes, suggesting that while SAI could counteract warming trends, it may introduce additional variability and uncertainty in rainfall projections. These results emphasize the importance of multimodel comparisons in assessing geoengineering impacts on regional climates, as differing sensitivities to radiative forcing and feedback can produce divergent outcomes.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD043117","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Merger of a Supercell and Squall Line in the Great Plains. 1: Initiation of the Supercell","authors":"Hongpei Yang,&nbsp;Yu Du,&nbsp;Juanzhen Sun","doi":"10.1029/2024JD042393","DOIUrl":"https://doi.org/10.1029/2024JD042393","url":null,"abstract":"<p>Using a four-dimensional variational data assimilation system that incorporates radar and surface observations, we investigated the initiation mechanism of a nocturnal supercell in the central Great Plains on 23 May 2020. This pristine convection occurred ahead of an eastward-propagating squall line, despite the absence of discernible surface convergence, and later evolved into a supercell that eventually merged with the approaching squall line. The atmospheric environment, which featured a low-level inversion layer with considerable convective inhibition, was generally unfavorable for surface-based convective initiation (CI). However, our analysis indicated that the spatial heterogeneous nocturnal southerly low-level jet (LLJ) played a key role in the elevated CI. As the LLJ advected moisture and warm air, neighboring regions experienced substantial low-level destabilization. Multiple convergence bands associated with the heterogeneous LLJ were identified, and the timing and location of CI were governed by these bands. CI occurred when one of the convergence bands moved northward to a position beneath a divergence band at the entrance of the mid-tropospheric jet. This overlapping pattern of convergence-divergence persisted for over an hour, facilitating both the initiation and development of the supercell. Additionally, we observed two other episodes of CI ahead of the squall line, each with different characteristics. The first, occurring earlier than the supercell initiation, was triggered by topographic convergence in a valley but quickly dissipated. Later, as the LLJ rotated clockwise, the most prominent convergence band shifted eastward, favoring the continuous development of forward-building cells ahead of the squall line, resulting in a T-shaped system.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144537008","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 Merger of a Supercell and Squall Line in the Great Plains: 2. Formation of a Bow Echo","authors":"Hongpei Yang,&nbsp;Yu Du,&nbsp;Juanzhen Sun","doi":"10.1029/2024JD042394","DOIUrl":"https://doi.org/10.1029/2024JD042394","url":null,"abstract":"<p>The merger of squall line and supercell has been commonly observed in the Great Plains of the United States. On 23–24 May 2020, an isolated supercell formed ahead of a squall line and subsequently evolved into a bow echo through their merger. Utilizing a 10-min update four-dimensional variational data assimilation system that integrates radar and surface observations, we investigated the convective-scale processes that led to the formation of this bow echo. Our findings indicated that as the squall line advanced eastward, its inflow was initially obstructed by the supercell, causing the weakening of both the squall line and its associated cold pool. However, during the merger, a strong rear inflow jet (RIJ) rapidly developed ahead of the squall line's leading edge and behind the supercell. Unlike a classic RIJ that typically expands rearward over the cold pool, this RIJ accelerated forward toward the supercell. Diagnostic pressure analysis revealed that the RIJ was primarily driven by the developing mesolow embedded within the supercell. Additionally, the supercell's strengthening prior to bowing generated a deep-tropospheric gravity wave downdraft, which amplified the RIJ by enhancing near-surface westerlies. Despite the weakening of the squall line's cold pool, it still contributed to the RIJ formation by providing negative horizontal vorticity at its leading edge and facilitating the RIJ's descent. Consequently, the intense RIJ and the subsequent replacement of the supercell against the initial leading edge led to the formation of a severe bow echo, producing a broad swath of damaging winds.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 13","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144536994","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}