Atmospheric Chemistry and Physics最新文献

{"title":"Tower- and drone-based BVOC observations in a suburban Tokyo forest: methodological insights and MEGAN comparison","authors":"Yujiro Ichikawa,Katsuhito Yoshida,Shinichi Yonemochi,Kentaro Takagi,Atsuyuki Sorimachi,Kazuhide Matsuda,Toshimasa Ohara","doi":"10.5194/acp-26-12521-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12521-2026","url":null,"abstract":"Abstract. Biogenic volatile organic compounds (BVOCs) substantially influence regional photochemical air pollution, climate, and the carbon cycle. However, observational constraints on BVOC emissions from urban or suburban forests in Asian megacity regions under humid subtropical climates remain limited. In this study, we conducted multi-year intermittent, multi-height BVOC observations at a 30 m flux tower in a suburban Tokyo forest dominated by Quercus serrata. Spatial variability was examined by combining tower measurements with supplemental drone-based sampling. The measurements were compared with estimates from the Model of Emissions of Gases and Aerosols from Nature (MEGAN). Isoprene volume mixing ratios increased during the warm-season observations from May to October, accounting for over 90 % of the measured BVOC composition during peak summer, while monoterpenes remained low with weak vertical gradients. Isoprene exhibited distinct vertical volume mixing ratio gradients peaking within the canopy, with the daily average emission fluxes ranging from −0.05 to 15.30 mgm-2h-1. Drone-based measurements indicated horizontal variability in isoprene volume mixing ratios of approximately 10 %–30 % within 30 m of the tower. Flux estimates derived from tower and drone measurements differed by approximately 30 %, suggesting that small-scale spatial heterogeneity and height differences can affect gradient-based flux estimates. MEGAN generally overestimated the observed fluxes, particularly during the warm-season observations. These results demonstrate the potential of combining tower-based vertical profiling with supplemental drone-based horizontal sampling to evaluate BVOC fluxes and their spatial representativeness. Although the intermittent sampling design limits comprehensive seasonal and interannual interpretations, this study provides methodological insights for future tower- and drone-based BVOC observations and emission model evaluation based on canopy-scale measurements.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"53 1","pages":"12521-12541"},"PeriodicalIF":6.3,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coastal upwelling and tropical warm water intrusions are key drivers of interannual fog variability along the southwestern African coast","authors":"Alexandre Mass,Jan Cermak,Hendrik Andersen","doi":"10.5194/acp-26-12565-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12565-2026","url":null,"abstract":"Abstract. Fog and low clouds (FLCs) are a key source of moisture for ecosystems in the Namib Desert, yet their variability and underlying mechanisms remain poorly quantified. We investigate monthly FLC cover in two fog hotspots: the Angolan Namib (15–17° S) and the Central Namib (22–24° S), using satellite-based observations from 2004 to 2019. Assuming that most fog originates from advected marine low clouds, we apply a cloud-controlling factor framework in which FLC anomalies are modeled as a linear function of spatial anomaly fields in estimated inversion strength (EIS), relative humidity at 700 hPa (R700), sea surface temperature (SST), and the eastward and northward components of the 10 m wind (U10 and V10). Sensitivities of FLCs to these drivers are quantified using a statistical model. Results indicate positive sensitivities to coastal EIS, negative sensitivities to R700, localized negative sensitivities to SST, and a strong influence of onshore circulation, consistent with an advective origin of fog in the Namib region. The statistical models are then used to reconstruct historical FLC anomalies for 1982–2019 using reanalysis data. The reconstructions reveal near-zero trends resulting from opposing influences: increased atmospheric stability enhances FLCs, while SST warming counteracts this. Finally, the reconstructions are used to assess interannual variability and its links to climate modes. Benguela Niño events, associated with tropical water intrusion and SST warming, explain up to half of the interannual FLC variability in the Angolan Namib, with warmer SSTs reducing FLC cover. El Niño conditions also enhance FLC occurrence, but their influence is much weaker.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"9 1","pages":"12565-12589"},"PeriodicalIF":6.3,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A cellular automaton model of tropical oceanic rain clusters with criticality","authors":"Kevin K. W. Cheung,Chee-Kiat Teo,Tieh-Yong Koh","doi":"10.5194/acp-26-12543-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12543-2026","url":null,"abstract":"Abstract. The distributions of the cluster area, A, and total rain rate, R, for tropical oceanic rain clusters from a cellular automaton (CA) are analysed for their scaling exponent ζA, ζR, and β where f(s) ∼ s-ζS; S∈{A,R}; f(s) the probability distribution of S; β is that for rain rate conditioned by rain area. The CA only includes a few simple rules representing a small set of dynamics thought to be important for convective organization. These rules represent large-scale destabilization of the atmosphere under the moisture static energy framework with a slow driving timescale, as well as convective cells interaction through propagating gravity waves with a fast relaxation timescale. The CA exhibits percolation-like criticality, and the ζA is estimated to be near the theoretical 2-dimensional percolation value of 187/91. This agrees well with the ζA estimates over the Indian Ocean warm pool and the tropical Atlantic reported in previous modelling study, implying numerical models behave like percolation. Although other critical exponents of the rain cluster distributions from the CA, namely the ηS (scaling exponent of the characteristic scale) and DS (cluster fractal dimension), S∈A,R, depend on the adjustable parameter of the CA, the ζA is robust to the adjustable parameter. Although the CA cannot account for the observation-based ζA ∼ 5/3 reported elsewhere that is quite universal over all oceans, further tuning of it such as through the convective cells interaction strength or how they interact may allow the CA to produce the observed exponent. Whether such behaviour can arise from a genuinely self-organized mechanism, rather than through parameter tuning, remains a question for future investigation.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"9 1","pages":"12543-12564"},"PeriodicalIF":6.3,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893602","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Planetary albedo change exacerbates surface warming: a perspective from cloud-type changes","authors":"Ruixue Li,Jiming Li,Bida Jian,Lijie Zhang,Jiayi Li","doi":"10.5194/acp-26-12591-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12591-2026","url":null,"abstract":"Abstract. Persistent global warming is modulated by cloud changes, yet the specific contributions and associated controlling factors remain inadequately quantified. Using CERES radiation data with a surface energy-balance framework, we quantify the contribution of cloud radiative changes to decadal surface temperature trends over 2002–2023. Cloud changes exert a weak net effect on global mean warming due to near-cancellation between shortwave warming and longwave cooling, but strongly modulate the meridional pattern of zonal-mean warming. Specifically, clouds enhance warming in low- and mid-latitudes while mitigating warming at high latitudes. This pattern is associated with a systematic redistribution of cloud occurrence from low-/mid-level cloud types to high-level optically thin clouds, which reduce planetary albedo and weaken cloud longwave emission. These changes exhibit hemispheric difference. In 30–60° N, the region contributing most to global warming, the decline in the cloud-reflected solar radiation is mainly driven by decreased cloud fraction, linked to elevated sea surface temperatures, aerosol reductions, and mid-tropospheric drying. In 30–60° S, reduced cloud reflectivity resulting from decreased cloud optical thickness and increased liquid droplet radius dominates. However, at high latitudes in both hemispheres, increased mid-/high-clouds and enhanced cloud reflectivity, driven by enhanced moisture, upper-tropospheric static stability and increased cloud optical thickness, lead to greater reflected solar radiation and reduced downwelling longwave radiation, thereby attenuating local warming. Our results establish a direct observational link between cloud-type changes, planetary albedo decline, and contrasting warming across latitude zones, characterizing the cloud-radiative changes in recent climate change.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"47 1","pages":"12591-12612"},"PeriodicalIF":6.3,"publicationDate":"2026-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upward transport and segregation of ice-nucleating particles in deep convective clouds","authors":"Jonas Schaefer,Sarah Grawe,Hans-Christian Clemen,Stephan Mertes,Johannes Schneider,Bruno Wetzel,Daniel Sauer,Jennifer Wolf,Laura Tomsche,Johanna Mayer,Roland Schrödner,Silvia Henning,Tina Jurkat-Witschas,Christiane Voigt,Helmut Ziereis,Theresa Harlaß,Mira Pöhlker,Frank Stratmann","doi":"10.5194/acp-26-12505-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12505-2026","url":null,"abstract":"Abstract. Ice-nucleating particles (INPs) play a crucial role in Earth's weather and climate by influencing cloud properties and precipitation. However, their abundance in the free troposphere, vertical distribution, and transport mechanisms are not well-characterized. This study presents immersion INP measurements from filter samples collected aboard the High Altitude and LOng range research aircraft (HALO) in the troposphere and the lower stratosphere (up to 14.5 km) over Europe during the CIRRUS-HL (Cirrus in High Latitudes) campaign in summer 2021. By sampling cloud particle residuals and aerosol particles in the inflow and outflow of deep convective clouds (DCCs), and performing offline INP analysis, we shed light on the vertical transport and segregation of INPs in DCCs. INP-temperature spectra of convective inflow included both INPs active at high (T > −15 °C) and low temperatures (T < −20 °C). In contrast the outflow spectra only featured INPs active at low temperatures. We explain the observed INP segregation in the updraft with precipitation scavenging of INPs active at high temperatures. INPs active at lower temperatures (T < −20 °C), however, are efficiently transported upwards into the free troposphere. There, ambient temperatures are below −40 °C, i.e., temperatures far below the temperatures at which these INPs initiate immersion freezing. In the DCC outflow, INP concentrations exceed the upper tropospheric background concentration by at least two orders of magnitude. These INPs are then available for ice formation in mid and upper tropospheric clouds.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"30 1","pages":"12505-12520"},"PeriodicalIF":6.3,"publicationDate":"2026-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the critical role of stabilized Criegee intermediates (sCIs) in sulfuric acid formation: coupling mechanistic updates with interpretable machine learning","authors":"Yuhuan Zhu,Qiang Chen,Luyan He,Chunlin Shang,Li Jiang,Donghong Guan,Guirong Yao,Wenkai Guo","doi":"10.5194/acp-26-12479-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12479-2026","url":null,"abstract":"Abstract. Sulfuric acid, formed via gas-phase SO2 oxidation, drives new particle formation and secondary sulfate aerosol under low relative humidity (RH). Beyond the well-established OH-mediated pathway, stabilized Criegee intermediates (sCIs) from alkene ozonolysis provide an additional SO2 oxidation route whose rate (LSO2,sCIs) and fractional contribution (μsCIs) vary markedly across environments. Although prior studies have documented this spatiotemporal heterogeneity, quantifying the individual factor contributions governing these differences remains lacking. Furthermore, because sCI and OH formation share common precursors yet differ mechanistically, μsCIs can alter the sensitivity of total SO2 oxidation (LSO2) to precursor variations, but the magnitude of this influence remains unclear. Here, we updated Criegee-related reactions in MCM v3.3.1 following recent IUPAC recommendations, conducted extensive AtChem box-model simulations, and trained interpretable XGBoost surrogate models to attribute LSO2,sCIs and μsCIs to their controlling factors and examine how μsCIs regimes modulate LSO2 sensitivity. LSO2,sCIs was primarily controlled by RH and isoprene. The dominant drivers of μsCIs differed between day and night: daytime factors included alkene speciation, O3, and the alkene fraction in VOCs; nighttime factors included alkene speciation, RH, and NOx. Under high-μsCIs regimes, positive LSO2responses to O3, VOCs, and alkene fraction were consistently amplified relative to low-μsCIs regimes. Field observation-based modeling of a summer episode in Wuhai supported these regime-dependent patterns. These findings indicate that reducing VOC emissions provides a more effective mechanism for regulating sulfuric acid formation under conditions with active alkene ozonolysis.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"70 1","pages":"12479-12503"},"PeriodicalIF":6.3,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A cross-instrument closure and polarimetric study for improving sub-millimeter polarimeter-radiometer ice cloud microphysics retrievals","authors":"Jie Gong,Yuli Liu,Joseph A. Finlon,Ian S. Adams,Rachael A. Kroodsma,Dong L. Wu,Ralf Bennartz","doi":"10.5194/acp-26-12457-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12457-2026","url":null,"abstract":"Abstract. Ice cloud microphysical properties, such as phase, shape, size and density, introduce significant uncertainties and biases that affect our understanding of how clouds influence weather and climate. The upcoming spaceborne sub-millimeter radiometers are expected to help in reducing the ice microphysics induced uncertainties in observations. Yet our knowledge about ice microphysics in this spectrum is still limited, and comparison/validation work is still sparse. This paper delivers a comprehensive cross-instrument closure study using active, passive remote sensing and in-situ cloud probe measurements collected during the NASA's IMPACTS field campaign. Through combined use of two radars, one lidar and in-situ cloud probe measurements, a comprehensive best reference “truth” is generated, which is then used to validate collocated sub-mm CoSSIR radiance measurements. We found out that only through a realistic vertical hydrometeor type classification that all types of measurements can reach a closure with minimal discrepancies between simulations and observations, which is critical for generating high-quality retrievals for frozen hydrometeors. We further present a comprehensive exploration of the scientific merit of polarimetric measurements in improving frozen hydrometeor microphysics retrievals. For the first time, we can validate previous theoretical predictions that sub-mm polarimetric signals can be used to retrieve ice particle habit and size. Moreover, we find it is possible to differentiate detailed vertical structure of hydrometeor types using both polarimetric and radiance measurements. This paper paves concrete steps in assuring timely delivery of high-quality science products for the sub-mm radiometer missions as well as possibilities of new science products beyond the mission requirements.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"1 1","pages":"12457-12477"},"PeriodicalIF":6.3,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orographic impacts of Réunion Island and Madagascar on heavy rainfall during Tropical Cyclone Batsirai (2022)","authors":"Keun-Ok Lee,Soline Bielli,Clément Soufflet,Rémi Laxenaire,Kevin Hoarau","doi":"10.5194/acp-26-12435-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12435-2026","url":null,"abstract":"Abstract. During the passage of tropical cyclone (TC) Batsirai (2022), the mountainous regions of Réunion Island and the eastern part of Madagascar experienced devastating floods. TC Batsirai passed north of Réunion Island (minimum distance of ∼ 210 km) before making landfall along the eastern coast of Madagascar. Using a non-hydrostatic research atmospheric model at 2 km resolution, we conducted a control simulation with realistic topography (CTL) and three flattened-terrain experiments (FLTall, FLTmdg, and FLTreu) to assess orographic effects. Relative to the flattened-terrain experiments, the presence of terrain increased localized rainfall by 96 % (2906 mm) over Réunion Island (CTL versus FLTreu) and 82 % (830 mm) over Madagascar (CTL versus FLTall), respectively. Over Réunion Island, orographically uplifted low-level moisture sustained 60 h of heavy rainfall (10 mm h−1), with a peak of 96 mm h−1, although the cyclone's intensity and track were minimally affected. In Madagascar, terrain not only intensified precipitation (19 h of heavy rainfall with a peak intensity of 92.8 mm h−1) but also altered the TC trajectory, delaying landfall by about 12 h and shifting it approximately 30 km south. These findings highlight the critical role of complex orography in shaping localized rainfall and TC behaviour in the southwest Indian Ocean.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"10 1","pages":"12435-12455"},"PeriodicalIF":6.3,"publicationDate":"2026-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Source-dependent optical and mineral signatures of dust outbreaks over the Mediterranean","authors":"Alkistis Papetta,Celia Herrero del Barrio,S. Yeşer Aslanoğlu,Rizos-Theodoros Chadoulis,Georgia Charalampous,Sara Herrero-Anta,Dimitra Kouklaki,Michail Mytilinaios,Anna Moustaka,Emmanouil Proestakis,Vassilis Amiridis,Christos Spyrou,Antonis Gkikas,Michael Pikridas,Maria Kezoudi,Franco Marenco,Jean Sciare,Sophie Vandenbussche,Stavros Solomos,Stelios Kazadzis,Ilias Fountoulakis","doi":"10.5194/acp-26-12395-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12395-2026","url":null,"abstract":"Abstract. Dust events frequently affect the Mediterranean Basin, however, the evolution of their optical and microphysical properties during transport remains poorly characterized. This study examines four major dust outbreaks in 2021–2022 affecting the Mediterranean, originating from the Eastern, Western, and Central Sahara and the Middle East. Combining ground-based AERONET sun photometers (24 stations), satellite (IASI, MODIS MIDAS) dust optical depth (DOD) data, and HYSPLIT back-trajectories, we track these events across Mediterranean sites. Results reveal regional differences in dust optical properties, including aerosol optical depth, single scattering albedo, and asymmetry factor, arising from source regions and transport processes. The Saharan events examined were dominated by coarse, scattering mineral dust, while the event originating from the Middle East featured finer, more absorbing particles, likely influenced by anthropogenic sources. MIDAS DOD-to-AOD ratios indicate that only one East-Central Saharan event maintained high dust fractions (DOD-to-AOD >0.8), suggesting relatively pure dust, while other events exhibited stronger spatial variability, with the Middle East event showing the lowest ratios, reflecting enhanced mixing with anthropogenic or marine aerosols. A regional case study in Cyprus using in situ elemental and absorption measurements shows that Middle Eastern dust event, despite lower mass concentrations, exhibited stronger absorption than the Saharan dust events observed in Cyprus. METAL-WRF mineralogical simulations indicate broadly similar mineral fractions across events, which alone could not explain the optical variability that observed across events. UAV-based composition data provide a first case-specific evaluation of modeled variability, although discrepancies in aluminum and magnesium highlight limitations in current dust representations.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"53 1","pages":"12395-12434"},"PeriodicalIF":6.3,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aircraft observations suggest an important contribution of methanesulfonic and sulfuric acids to tropical Indo-Pacific aerosol","authors":"Hannah Klebach,Martin Heinritzi,Katharina Kaiser,Lisa Beck,Samuel Ruhl,Samira Atabakhsh,Nirvan Bhattacharyya,Lucía Caudillo-Plath,Philipp Joppe,Thomas Klimach,Peter Lloyd,Mira Pöhlker,Ulrich Pöschl,Sarah Richter,Douglas M. Russell,Johannes Schneider,Marcel Zauner-Wieczorek,Joachim Curtius","doi":"10.5194/acp-26-12355-2026","DOIUrl":"https://doi.org/10.5194/acp-26-12355-2026","url":null,"abstract":"Abstract. In the marine environment dimethyl sulfide (DMS) is the most abundant sulfur-containing trace gas. It serves as a key precursor to new particle formation and growth via its oxidation products, sulfuric acid (SA, H2SO4) and methanesulfonic acid (MSA, CH3SO3H). Here, we present measurements of MSA and SA in the Indo-Pacific region during the CAFE-Pacific (Chemistry of the Atmosphere Field Experiment in the Pacific) campaign in January–February 2024. The measurements were conducted on board the HALO (High Altitude and LOng-range) aircraft using nitrate mass spectrometry. We observe gas-phase concentrations of up to 4×107 cm−3 MSA and 6×107 cm−3 SA in the marine boundary layer. In the lower free troposphere, the MSA / SA ratio increases with altitude in agreement with the temperature-dependent DMS oxidation. At higher altitudes, adiabatic heating and subsequent evaporation of acidic particles within the instrument inlet enable the detection of both particle- and gas-phase MSA and SA. A detailed analysis of two flights shows that marine deep convection can lead to DMS transport from the boundary layer to the upper troposphere and subsequent particle formation and growth after approximately 10–20 h of OH exposure aligning with the DMS lifetime determined by kinetic modelling. We frequently observe MSA concentrations significantly exceeding those of SA, suggesting that free-tropospheric particles – particularly over the Indo-Pacific Warm Pool – may be dominated by MSA. Our results imply that marine convection represents an important source of airborne particles in the upper tropical troposphere, one of the most pristine regions of Earth's atmosphere.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"7 1","pages":"12355-12393"},"PeriodicalIF":6.3,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148893614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}