Journal of Geophysical Research: Atmospheres最新文献

{"title":"Satellite-Derived 700-hPa Geopotential Height Fields for Localization of Southwest Vortices and Diagnosis of Their Lower-Tropospheric Environments","authors":"Ce Zhang,&nbsp;Xiaolei Zou","doi":"10.1029/2026JD046890","DOIUrl":"https://doi.org/10.1029/2026JD046890","url":null,"abstract":"<p>Topographic gravity waves over the Tibetan Plateau generate downstream southwest vortices (SWVs) that are difficult to localize objectively and often produce heavy precipitation across mainland China. We introduce a new geopotential-height-only framework for SWV localization and characterization of their lower-tropospheric environments using only satellite microwave temperature-sounding observations from a three-orbit polar satellite constellation—FY-3E, MetOp-C, and NOAA-20. First, we demonstrate that localization accuracy comparable to conventional methods can be achieved by identifying the center of an ellipse fitted to the largest connected region of 700-hPa geopotential height values below the first-decile threshold, thereby eliminating the need for vorticity and wind information. We then apply this approach to geopotential height fields retrieved from these satellite microwave temperature-sounding observations for 22 SWV cases occurring in 2023, enabling satellite-based tracking and characterization of associated lower-tropospheric environments, independently supported by Himawari-9 infrared brightness temperatures. In addition, the satellite-derived geopotential height fields are further evaluated against ERA5 reanalysis fields, ERA5 all-sky brightness temperature simulation-derived geopotential height fields, and a random-forest-based SWV tracking method, demonstrating overall consistency and robustness of the proposed framework. This capability enables observation-driven localization and environmental diagnosis of mesoscale weather systems, particularly in regions with sparse conventional observations.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149068471","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":"Characteristics of Immersion Freezing Ice Nucleating Particles During Dust Season in Beijing","authors":"Ke Cao,&nbsp;Manni Chen,&nbsp;Zhaolong Wu,&nbsp;Angnuo Tian,&nbsp;Yangze Ren,&nbsp;Kai Bi,&nbsp;Ping Tian,&nbsp;Qinghong Zhang,&nbsp;Huiwen Xue","doi":"10.1029/2026JD046632","DOIUrl":"https://doi.org/10.1029/2026JD046632","url":null,"abstract":"<p>Atmospheric dust is a primary source of ice nucleating particles (INPs), yet their concentrations at temperatures warmer than −20°C are not fully characterized during Asian dust events. This study uses a membrane filtering method to collect aerosol samples and a droplet freezing method to measure daily immersion-mode INP concentrations in Beijing during the dust season throughout March 2022. Daily aerosol samples are categorized into low, moderate, and heavy dust conditions using volume depolarization ratios from a Micro Pulse Lidar (MPL). Observed INP spectra exhibit a day-to-day variability of up to two orders of magnitude at a given temperature. The INP spectra can generally be fitted with a two-mode distribution. We find that INP concentration correlates strongly with the mass concentration of coarse aerosols (PM_coarse), but weakly with that of fine aerosols. We therefore develop a PM_coarse-based INP parameterization that is applicable to the mixed-phase cloud temperature range (−3.5°C to −23.5°C). The parameterization scheme is validated using several independent measurements in the Beijing region. It offers a practical approach for estimating INP concentrations at relatively warm temperatures in atmospheric models by utilizing routinely available PM_coarse data from air-quality monitoring networks or chemical transport models. Heat treatment tests reveal that more than 50% of INPs are heat-sensitive, indicating that biological or other heat-sensitive materials may significantly contribute to INP concentrations, particularly at warmer temperatures.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD046632","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149068237","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":"High Time-Resolution Measurements of Organic Molecular Markers Reveal the Chemical Evolution and Formation Mechanism of Summertime High-PM Episodes: A Case Study in Wuhan, Central China","authors":"Yongyi Zhao,&nbsp;Shuhui Zhu,&nbsp;Zongjun Li,&nbsp;Hongli Wang,&nbsp;Qingyan Fu,&nbsp;Bo Zhu,&nbsp;Nan Chen,&nbsp;Qiongqiong Wang,&nbsp;Huan Yu","doi":"10.1029/2025JD046263","DOIUrl":"https://doi.org/10.1029/2025JD046263","url":null,"abstract":"<p>China has experienced frequent fine particulate matter (PM_2.5) episodes in recent years; however, molecular-level chemical evolution and formation mechanisms of these events remain poorly understood. This study presents the first integrated analysis combining high-time-resolution measurements of organic molecular markers from thermal desorption aerosol gas chromatography-mass spectrometry (TAG) and chemical ionization mass spectrometry (CIMS), with bulk aerosol composition measurements, to investigate the dynamic chemical transformation and formation processes of summer PM episodes in Wuhan, Central China. Using the mass increment ratio (MIR), defined as the concentration during episodes divided by that before episodes, we quantified the enhancement of different species. MIR values &gt;1 were observed for most PM_2.5 major components and organic molecular markers. By examining diagnostic ratios of selected molecular tracer pairs, we revealed distinct aging characteristics of different aerosol types during episodes. Source apportionment analysis incorporating the comprehensive high-time-resolution organic molecular tracers identified 11 source factors, six of which were characterized by organic tracers: biomass burning, vehicle emission, cooking emission, aliphatic secondary organic aerosol (SOA), aromatic SOA, and biogenic SOA. Biomass burning and secondary sulfate formation process were two major sources across the campaign period, each contributing to 23% of PM_2.5. During local episodes, the rapid increase in PM_2.5 was primarily driven by biomass burning emissions and secondary nitrate formation process, with fresh biomass burning tracers and nitro-aromatic compounds showing the highest enhancements. In contrast, during transport episodes, elevated contributions from biogenic SOA, and secondary nitrate formation process, along with greater mass increments of hDCAs and biogenic SOA tracers, suggested regional transport of aged secondary aerosols. These results advance mechanistic understanding of how competing photochemical and aqueous-phase pathways drive SOA formation and how source-specific emissions evolve during different episode types. This study demonstrates the efficacy of high-time-resolution organic marker measurements in elucidating rapid chemical evolution and formation mechanisms of PM episodes, providing a scientific basis for formulating region-specific air quality management strategies with implications for other regions experiencing severe air pollution.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149068470","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":"Sulfur Dioxide Point Sources Remain Important for Daytime Plume-Scale New Particle Formation in the United States: Case Study for Gary, Indiana During the Summer 2023 AEROMMA Aircraft Campaign","authors":"En Li,&nbsp;Samuel E. O’Donnell,&nbsp;Adam T. Ahern,&nbsp;Kelvin H. Bates,&nbsp;Charles A. Brock,&nbsp;Wyndom S. Chace,&nbsp;Matthew M. Coggon,&nbsp;Emily V. Fischer,&nbsp;Jessica B. Gilman,&nbsp;Georgios I. Gkatzelis,&nbsp;Han N. Huynh,&nbsp;Emily R. Lill,&nbsp;Ming Lyu,&nbsp;Ann M. Middlebrook,&nbsp;Alison M. Piasecki,&nbsp;Jeff Peischl,&nbsp;Ilana B. Pollack,&nbsp;Andrew W. Rollins,&nbsp;Nell B. Schafer,&nbsp;Chelsea E. Stockwell,&nbsp;Victoria Treadaway,&nbsp;Carsten Warneke,&nbsp;Eleanor M. Waxman,&nbsp;Lu Xu,&nbsp;Kristen Zuraski,&nbsp;Robin G. Stevens,&nbsp;Shantanu H. Jathar,&nbsp;Jeffrey R. Pierce","doi":"10.1029/2026JD047267","DOIUrl":"https://doi.org/10.1029/2026JD047267","url":null,"abstract":"<p>Plumes from sulfur dioxide (SO₂) point sources have been shown to be significant contributors to new particle formation (NPF), but SO₂ emissions in the United States (US) have decreased drastically by ∼10× since the early 2000s. We present observations of plume-scale NPF from SO₂ point sources over the industrial hub in Gary, Indiana and assess the importance of SO₂ plumes to NPF using the P6 subgrid NPF parameterization and model the subsequent aerosol growth using the Statistical Oxidation Model-TwO Moment Aerosol Sectional (SOM-TOMAS) kinetic gas/aerosol model. We identify 29 SO₂-rich NPF plumes downwind of SO₂ point sources in our observations. Across eight separate flight passes over Gary, the total plume-scale particle production rate via NPF is estimated to be in the range of 8.5 × 10¹³–3.5 × 10¹⁸ # s⁻¹ and is typically comparable to or greater than primary particle number emissions from traffic in nearby Chicago. On a single case day, subsequent growth of newly formed particles is mainly driven by regional condensation of organics and coagulation. These results demonstrate the continued importance of SO₂ point sources for plume-scale NPF and regional aerosol number concentrations, including those of climate-relevant sizes (&lt;50–100 nm diameter), despite more than a factor-of-10 reduction in SO₂ emissions in recent decades. Further, organics are critical in sustaining the growth of these newly formed particles, and organics may be more important for this growth compared to past decades due to reduced sulfuric acid (H₂SO₄).</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD047267","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149206182","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":"Dependence of Neutralized Charge Amount on Meteorological Conditions in Summertime Lightning Discharges in Japan","authors":"Naota Iwai,&nbsp;Yousuke Sato,&nbsp;Mitsuteru Sato,&nbsp;Masaru Inatsu","doi":"10.1029/2026JD046314","DOIUrl":"https://doi.org/10.1029/2026JD046314","url":null,"abstract":"<p>Lightning discharges in Gunma Prefecture, Japan, from June–September 2023 were analyzed to explore the dependence of the neutralized charge amount on cloud structures embedded in weather systems, mainly based on in situ measurements of the ground-based electric field, radar and satellite remote sensing, and numerical simulations using a bulk lightning model. Two types of lightning episodes distinguished by meteorological conditions were identified during the analysis period: lightning discharges in frontal cloud systems with abundant hydrometeors and lightning discharges in isolated convective storms under highly unstable conditions. Lightning discharges in frontal cloud systems were characterized by a large amount of neutralized charge and high lightning frequency. This was attributed to abundant graupel between the −10°C and −20°C levels, a critical temperature range for charge separation. In contrast, the neutralized charge amount was approximately three times smaller in isolated convective storms. In this case, graupel was mainly distributed above the −20°C level, outside the critical temperature range, resulting in a reduced amount of charge carried by hydrometeors.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD046314","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149068238","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":"Molecular Evidence for the Atmospheric Transformation of Trash Burning Aerosol Into Organonitrate- and Organosulfate-Rich Haze: A Case Study From the Eastern Indo-Gangetic Plain","authors":"Amna Ijaz,&nbsp;Susan Mathai,&nbsp;Zezhen Cheng,&nbsp;Simeon Schum,&nbsp;Nurun Nahar Lata,&nbsp;William Kew,&nbsp;Claudio Mazzoleni,&nbsp;Lynn Mazzoleni,&nbsp;Swarup China","doi":"10.1029/2026JD046895","DOIUrl":"https://doi.org/10.1029/2026JD046895","url":null,"abstract":"<p>Open burning of solid waste is projected to contribute up to 29% of global anthropogenic PM_2.5 emissions, yet its role in secondary aerosol formation remains largely absent from current assessments. Using 21-T Fourier transform-ion cyclotron resonance mass spectrometry, we show that fresh trash burning organic aerosol (tbOA) in the Indo-Gangetic plain, specifically West Bengal, India, during wintertime is dominated by more volatile, low-oxygenation CHO species (66% of the formulae), including markers of plastic and biomass combustion. The downwind ambient aerosol in haze was dominated by less volatile, highly oxygenated organonitrates and organosulfates (&gt;85% of the formulae), consistent with substantial atmospheric transformation. Single-particle measurements show that freshly emitted tbOA is internally mixed with inorganic salts, implying enhanced hygroscopicity and aqueous-phase processing as a mechanistic driver of this transformation. Our molecular-level observations suggest a potential link between open trash burning and organonitrate- and organosulfate-rich secondary aerosol in the regional winter boundary layer. Our results motivate targeted chamber experiments and regional modeling studies to better quantify the contributions and chemical evolution of trash burning emissions in air quality assessments.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 19","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD046895","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146886","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":"Excessive Convective Precipitation Formation Caused by Warm-Phase Bulk Microphysical Scheme Biases: A Multi-Platform Observational Diagnosis","authors":"McKenna W. Stanford,&nbsp;Adam C. Varble,&nbsp;Zhe Feng,&nbsp;Jerome Fast,&nbsp;William I. Gustafson Jr.,&nbsp;Susanne Glienke,&nbsp;Joseph C. Hardin,&nbsp;Zhixiao Zhang","doi":"10.1029/2026JD047076","DOIUrl":"https://doi.org/10.1029/2026JD047076","url":null,"abstract":"<p>Recent work has demonstrated that convection-permitting models often produce a greater number of precipitating convective cells compared to radar observations. Congestus-depth cells contribute most to the bias, which are colloquially termed “popcorn convection.” This study explores warm-phase microphysical contributions to the bias using simulations spanning a field campaign hosted in the mountains of central Argentina. Observations from a C-band radar, satellite, in situ aircraft, and surface disdrometers are used to evaluate a 3-km grid spacing, 6.5-month simulation using bulk aerosol-aware microphysics and case studies with higher model resolutions. Compared to observations, clouds precipitate too frequently (by up to a factor of 2.5), particularly for congestus-depth clouds. These cells precipitate under high aerosol loadings (&gt;4,000 cm⁻³) and most are purely liquid upon initiation of precipitation. Comparison with in situ aircraft observations shows that simulations shift too much bulk liquid mass to precipitation-sized drops, especially for low liquid water contents (LWCs), indicating potential issues with parameterized autoconversion. This leads to high-biased in-cloud radar reflectivity of 8–14 dBZ for LWCs &lt; 10⁻¹ g m⁻³, producing radar reflectivity signals that contribute to convective cell identification and cell-number biases. Case studies using 500 and 100 m horizontal grid spacings do not ameliorate these biases, implying that under-resolved updrafts and entrainment are not first-order culprits. Attributing warm-phase microphysical processes to convective cell-number and precipitation frequency biases motivates a more detailed understanding of precipitation formation pathways in continental convective clouds, their sensitivity to aerosols, and novel methods capable of relieving modern structural limitations in bulk microphysics schemes.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 18","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD047076","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146965","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":"Near-Field Acoustic and Gravity Wave Modes in the Ionosphere Triggered by Ground Motion and Tsunami During the 2024 Mw7.4 Hualien Earthquake","authors":"Oluwasegun M. Adebayo,&nbsp;Lucie Rolland,&nbsp;Esfhan A. Kherani,&nbsp;Tung-Yuan Hsiao,&nbsp;Loren C. Chang,&nbsp;Alexandre A. Pimenta,&nbsp;Virginia A. Klausner","doi":"10.1029/2026JD046968","DOIUrl":"https://doi.org/10.1029/2026JD046968","url":null,"abstract":"<p>The interaction between the atmosphere and other components of the Earth system, such as the solid Earth and the oceans, remains an open and active area of research. In particular, the dynamic response of the ionosphere to forcing from below, such as earthquakes and tsunamis, is not yet fully understood. In this study, we investigate the ionospheric response to the Mw7.4 Hualien, Taiwan earthquake and trace each observed disturbance mode to its corresponding source mechanism. Using ground vertical velocity data from seismometer stations, Total Electron Content (TEC) measurements from 122 GNSS receivers, and tsunami observations from DART buoy data, we identify multi-mode ionospheric disturbances propagating at speeds of ∼1.0, 0.60, and 0.22 km/s. The ∼1.0 km/s is the fastest mode directly driven by coseismic ground shaking. The slower mode of 0.60 km/s is most likely generated by the superposition of the primary acoustic waves (1.0 km/s) and ducted acoustic-gravity waves; may therefore be interpreted as a secondary acoustic-gravity wave. The slowest mode, propagating at 0.22 km/s, lies within the gravity wave range and is attributed to the regional-scale tsunami triggered by the Mw7.4 earthquake. To the best of our knowledge, this represents the first observation of ionospheric disturbances generated by a moderate regional-scale tsunami. Short-Time Fourier Transform (STFT) analysis further reveals dominant center frequencies of ∼3.80, ∼2.60, and 1.30 mHz for the acoustic and gravity wave modes, respectively, consistent with known spectral characteristics of acoustic and tsunamigenic sources.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 18","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD046968","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146748","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":"MAIAC Aerosol Algorithm Over Water","authors":"Alexei Lyapustin,&nbsp;Yujie Wang,&nbsp;Myungje Choi,&nbsp;Andrew M. Sayer,&nbsp;Sergey Korkin","doi":"10.1029/2026JD047862","DOIUrl":"https://doi.org/10.1029/2026JD047862","url":null,"abstract":"<p>MAIAC VIIRS Collection 2 aerosol product for the first time provides global coverage over land and ocean. This paper gives a first systematic description of MAIAC ocean aerosol algorithm covering cases of open ocean, waters with sediments and brown waters from rivers' discharge. An extensive validation of MAIAC AOD and Ångström Exponent (AE) against AERONET and Maritime Aerosol Network data confirms retrieval accuracy within ±10% for AOD and ±0.4 for AE. A comparison with the Deep Blue (DB) and Dark Target (DT) algorithms shows a generally similar performance with some improvement in the AE accuracy and in cloud detection. A comparison of MAIAC aerosol products derived from VIIRS on SNPP, JPSS1 and JPSS2 satellites indicates minor spectral calibration differences which will be addressed in our ongoing calibration work.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 18","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026JD047862","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149048369","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":"Size-Resolved Particle Effective Density in the Free Troposphere at Mt. Hua, China: Influence of Chemical Aging and Sources","authors":"Yaqing Zhou,&nbsp;Jiaen Cai,&nbsp;Nan Ma,&nbsp;Qiyuan Wang,&nbsp;Li Li,&nbsp;Weikang Ran,&nbsp;Juan Hong,&nbsp;Jiangchuan Tao,&nbsp;Shaobin Zhang,&nbsp;Jingnan Shi,&nbsp;Shuang Han,&nbsp;Minghua Liang,&nbsp;Yong Zhang,&nbsp;Jie Tian,&nbsp;Linhong Xie,&nbsp;Qiaoqiao Wang,&nbsp;Hang Su,&nbsp;Yafang Cheng,&nbsp;Junji Cao","doi":"10.1029/2026JD046678","DOIUrl":"https://doi.org/10.1029/2026JD046678","url":null,"abstract":"<p>Effective density (<i>ρ</i>_eff) is a key physical property of atmospheric particles, yet it has rarely been investigated in free tropospheric environments. It is largely determined by chemical compositions and particle morphology, providing valuable insights into atmospheric evolution and air-mass aging. Here, size-resolved <i>ρ</i>_eff was measured at Mount Hua (2060 m a.s.l.) in the Fenwei Plain, China, during autumn 2021, using a coupled differential mobility analyzer-centrifugal particle mass analyzer-condensation particle counter (DMA-CPMA-CPC) system. We found that the <i>ρ</i>_eff increased from 1.40 g cm⁻³ at 50 nm to 1.54 g cm⁻³ at 350 nm, generally higher than those observed for similar size ranges at ground-level sites (∼1.2–1.4 g cm⁻³), indicating a reduced contribution from low-density particles and the predominance of aged aerosol components in the free troposphere. Black carbon (BC) exerted the strongest influence on <i>ρ</i>_eff, and a 5% increase in BC mass fraction was associated with a decrease of approximately 0.06 g cm⁻³ in <i>ρ</i>_eff. The retrieved BC effective density ranged from 0.85 to 1.20 g cm⁻³, indicating that BC particles may remained non-spherical shapes even within the free troposphere. During the observation, a vertical transport event led to <i>ρ</i>_eff decline of ∼0.1 g cm⁻³ as near-surface pollutants were entrained to the summit. Additionally, long-range transport from northwestern China systematically lowered <i>ρ</i>_eff due to distinct changes in chemical composition. These findings highlight the significant role of aerosol source and transport in shaping the physical and chemical properties of free tropospheric aerosols.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"131 18","pages":""},"PeriodicalIF":3.8,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149048172","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}