Atmospheric Chemistry and Physics最新文献

{"title":"Tropospheric OH and its trends: new insight into atmospheric processes and implications for methane lifetime","authors":"Xuewei Hou,Ryan Hossaini,Oliver Wild,Andrea Mazzeo,Richard J. Pope,Ye Wang,Siyuan Wang,Yuanhong Zhao,James Lee,Bin Zhu,Tianliang Zhao,Alok K. Pandey","doi":"10.5194/acp-26-13767-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13767-2026","url":null,"abstract":"The hydroxyl radical (OH) is a critical determinant of global oxidative capacity and trace gas lifetimes, but its variation remains poorly constrained. This study investigates the sensitivity of modelled tropospheric OH concentration changes to new understanding of physical and chemical processes using the FRSGC/UCI chemistry transport model. We show that simulated tropospheric O 3 and NO 2 agree well with satellite observations, but that annual variations in CO do not, likely due to uncertainties in biomass burning emissions in the southern hemisphere and overestimated CO trends over Asia. This discrepancy, along with the background increase in CO, may lead to an underestimation of OH increase or overestimation of OH decrease from 2000 to 2017. Changes in tropospheric OH column show substantial spatial heterogeneity, with increases in OH in high-emission regions and decreases in the tropics. Global mean OH trends are dependent on the assumed trend in emissions: with time-varying emissions there is little change in OH, while under annually invariant emissions, OH increases in response to changes in meteorological conditions. Inclusion of water vapor UV absorption, heterogeneous reactions, and updates to the OH+NO 2 reaction rate have a smaller impact, but decrease OH levels by 3.6 %, 5.8 %, and 7.0 %, respectively, increasing CH 4 lifetimes by 4.2 %, 5.2 %, and 8.4 %. Incorporating oceanic CH 3 CHO emissions reduces global mean OH by up to 1.5 %, increasing the CH 4 lifetime by up to 1.6 %. These results provide a quantitative basis for understanding the drivers of tropospheric OH variability and their implications for global methane chemistry.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"36 1","pages":"13767-13793"},"PeriodicalIF":6.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088325","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":"Inferring European fossil fuel CO\u0000 2\u0000 emissions using TROPOMI NO\u0000 2\u0000 data and sector-based NO\u0000 \u0000 x\u0000 \u0000  : CO\u0000 2\u0000 emission ratios","authors":"Chlöe N. Schooling,Liang Feng,Ingrid Super,Paul I. Palmer","doi":"10.5194/acp-26-13743-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13743-2026","url":null,"abstract":"Accurate monitoring of fossil fuel CO 2  (ffCO 2 ) emissions is essential for tracking climate mitigation, yet natural carbon-cycle fluxes often obscure human-induced signals in atmospheric observations. This study presents a proof-of-concept satellite-driven data assimilation framework that uses nitrogen oxides (NO x  = NO + NO 2 ) – short-lived trace gases co-emitted with CO 2 –, to estimate ffCO 2 emissions. We estimate European NO x emissions for 2021 by assimilating TROPOMI NO 2 observations into an Ensemble Kalman Filter (EnKF) framework, optimised within the GEOS-Chem atmospheric transport model. We use a computationally efficient offline treatment of NO x chemistry, enabling large-ensemble inversions while retaining sensitivity to changes in photochemistry. Assimilating these data leads to a systematic reduction in the state vector uncertainty, with the mean uncertainty in total ffCO 2 emissions over Europe decreasing from 5.6 % in the prior to 3.3 % in the posterior. As well as overall improvement in model agreement with observations that corresponds to an annual correlation increase, Δ r =0.12, derived from the correlation of all daily model–observation pairs across all grid cells in the European domain. By leveraging sector-specific NO x  : CO 2 emission ratios, we translate our posterior NO x flux estimates into corresponding ffCO 2 estimates that capture enhanced seasonal variability. Our inferred ffCO 2 emissions exhibit elevated values in autumn and winter, spatially concentrated over major source regions and consistent with surface temperature variability. The inferred posterior adjustments include substantial increases in national emissions in several regions (20 %–91 % in national annual combustion CO 2 ), highlighting both the sensitivity of the method and the need for further validation and multi-species observational constraints. Independent evaluation against in situ measurements confirms significant improvements in mean error statistics in some regions. And updated national posterior ffCO 2 emissions show improved agreement with EDGAR across five high emitting European countries. This study demonstrates the potential of ensemble data assimilation and reduced-complexity chemistry to provide a first-order constraint on European ffCO 2 estimates, establishing a vital foundation for future joint NO 2 –CO 2 inversion systems.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"31 1","pages":"13743-13766"},"PeriodicalIF":6.3,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088083","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":"Impact of model resolution and turbulence scheme on the representation of mountain waves and turbulence","authors":"Roshny Siri Jagan,Juerg Schmidli","doi":"10.5194/acp-26-13721-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13721-2026","url":null,"abstract":"Simulating mountain waves and associated turbulence in the upper troposphere and lower stratosphere (UTLS) remains a challenge in numerical weather prediction (NWP). We investigate how the representation of mountain-wave dynamics and turbulence in the ICOsahedral Nonhydrostatic (ICON) model depends on model resolution and turbulence parameterization. ICON simulations were performed in NWP mode (ICON-NWP) with varying horizontal (2, 1 km, 500 m) and vertical (400, 200, 100 m) resolutions, using the operational turbulent kinetic energy scheme (ICON-TKE) and the newly developed two-energy turbulence scheme (ICON-2TE). The simulations were evaluated against high-frequency in situ observations from the Deep Propagating Gravity Wave Experiment (DEEPWAVE) over New Zealand on 12 July 2014, as well as a nested large-eddy simulation (ICON-LES) at 130 m resolution. The results show reasonable agreement with observations: ICON-LES more closely captures wavelength and phase, while ICON-NWP better reproduces wave amplitude. Near-convergence of the primary mountain wave and of turbulence structures requires horizontal grid spacings of 1 km or finer and vertical spacings in the UTLS of 200 m or finer, whereas trapped lee waves and downstream wave structure remain resolution-sensitive at these resolutions. Area-averaged, bulk measures allow this convergence behavior to be characterized more systematically: the low-level gravity-wave momentum flux continues to increase with increasing resolution from 1 km to 500 m. A key finding is that both turbulence schemes yield similar wave structures, despite large differences in simulated turbulent kinetic energy. This discrepancy is attributed to the empirical horizontal-shear source term of the operational TKE-scheme configuration, which produces spurious TKE at km-scale resolution. These results provide guidance on the resolution and turbulence representation needed for reliable simulations of small-scale mountain waves and turbulence in the UTLS.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"26 1","pages":"13721-13741"},"PeriodicalIF":6.3,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149092291","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":"Isotopic fractionation during ice growth by riming and its effect on the\u0000 d\u0000 -excess of precipitation","authors":"Pradeep K. Aggarwal,Courtney Schumacher,Frederick J. Longstaffe,Aaron Funk,Matthew D. Shupe","doi":"10.5194/acp-26-13661-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13661-2026","url":null,"abstract":"We have investigated the impact of riming on the deuterium excess ( d -excess =  δ 2 H − 8 ⋅  δ 18 O) of precipitation. In mixed-phase clouds, precipitation forms by vapor deposition, where supercooled liquid droplets do not come in contact with ice particles, and by riming, where droplets freeze directly on particle surfaces. While vapor deposited ice generally has higher d -excess than liquid, riming is assumed to occur without isotopic fractionation. We correlated radar-observed mean Doppler velocity (MDV), an independent indicator of riming, with precipitation d -excess (−23 ‰ to +45 ‰) at polar (Summit, Greenland; Ny-Ålesund and Andenes, Norway, Dumont d'Urville, Antarctica), mid-latitude (Cazadero, California) and tropical (Rio Claro, Brazil) sites. The d -excess decreases with increasing MDV (or riming intensity) at all locations, except for winter precipitation at Summit. The low d -excess of rimed ice is consistent with the evaporation of accreted liquid on particle surface before freezing is complete. For Summit winter, cold temperatures and low δ 18 O of vapor suppress d -excess independently of riming. Calculations show that mixtures of ice growing by riming and vapor deposition (including diamond dust) can produce the observed range of precipitation d -excess in this study. We conclude that riming-driven lowering of d -excess can explain, at least in part, the spatial gradients in surface snow d -excess across Greenland and Antarctica previously attributed to changes in source moisture origin, and the very low d -excess of rainfall attributed solely to sub-cloud evaporation. Precipitation d -excess can be used to estimate the rimed mass fraction, providing observational constraints for improving microphysics schemes in climate models.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"53 1","pages":"13661-13692"},"PeriodicalIF":6.3,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088327","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":"Measurement report: Global Total Ozone Records – Part 1: Ground-based monitoring networks performance assessment and status review","authors":"Xiaoyi Zhao,Vitali Fioletov,Irina Petropavlovskikh,Voltaire Velazco,Alberto Redondas,Anna Solomatnikova,Corinne Vigouroux,Kimberly Strong,Michel Van Roozendael,Andrea Pazmino,Thomas F. Hanisco,Alexander Cede,Martin Tiefengraber,Gordon Labow,Masatomo Fujiwara,Ronald van der A,Debora Griffin,Chris McLinden,Tom Kralidis,Wolfgang Steinbrecht,Sum Chi Lee","doi":"10.5194/acp-26-13693-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13693-2026","url":null,"abstract":"Total column ozone (TCO) has been observed since the 1920s, with a systematic monitoring network established during the International Geophysical Year (1957–1958). We compile and assess TCO records from six major ground-based instrument types: Dobson and Brewer spectrophotometers, Filter ozonometers, zenith-sky DOAS (UVVIS), Fourier-transform infrared (FTIR) spectroscopy, and Pandora spectrometers. Data are drawn from the World Ozone and Ultraviolet Radiation Data Centre, Network for the Detection of Atmospheric Composition Change, Pandonia Global Network, and European Brewer Network. Using harmonized statistical criteria and daily comparisons with multiple satellite products and four reanalysis datasets, we evaluate site-level performance in 5-year intervals from 1940 to 2024. Metrics include mean bias, variability of daily and monthly differences, seasonal amplitude, and the range of annual means, with percentile-based thresholds used to classify data quality. Ground-based annual means generally agree with satellite and reanalysis benchmarks within ± 2 %, with typical variability near 2 %. Larger discrepancies occur in the pre-satellite era, where reanalyses show biases of up to −5 % relative to Dobson observations. Network-wide distributions of daily mean differences to those from reanalysis and satellite data indicate comparable internal consistency for Brewer, Dobson, FTIR, and Pandora (standard deviations generally around 2 %), while Filter and UVVIS exhibit slightly broader spreads (< 3 %), especially at high latitudes. Network capacity has evolved substantially since the 2000s, with a decline in Dobson sites and expansion of Brewer and Pandora observations. By providing station-level flags and thresholds, this assessment helps network operators prioritize calibration and reprocessing efforts and helps users identify robust records, thereby improving confidence in long-term ozone trend detection and satellite validation.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"11 1","pages":"13693-13720"},"PeriodicalIF":6.3,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088329","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":"Tracing biological, anthropogenic, and inorganic sources of coarse aerosols via single-particle fluorescence and optical morphology","authors":"Aiden Jönsson,Jinglan Fu,Gabriel Pereira Freitas,Ian Crawford,Pavla Dagsson-Waldhauserová,Radovan Krejci,Yutaka Tobo,Karl Espen Yttri,Paul Zieger","doi":"10.5194/acp-26-13617-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13617-2026","url":null,"abstract":"Coarse-mode aerosol particles influence the environment, climate, and human health in diverse ways depending on their type. While mineral dust and sea spray aerosol (SSA) dominate this size range, rarer biological particles can have outsized impacts, such as initiating hydrometeor freezing at relatively warm temperatures. Accurate type-specific characterization of coarse-mode aerosol is therefore essential for investigating their roles in climate and the environment. We provide a new reference dataset for fluorescence spectra and morphology characteristics of coarse-mode aerosols from common sources, including pollen, dust, bacteria, and microplastics, measured in controlled experiments with a Multiparameter Bioaerosol Spectrometer (MBS). Comparisons with published datasets revealed consistent source-dependent fluorescence features, but also highlighted similarities between biological and non-biological particles that can bias fluorescence-based classifications. To explore solutions for these confounding similarities, we developed a supervised machine learning classification algorithm integrating fluorescence and morphology information, and evaluated it using MBS and comprehensive chemical tracer observations from Zeppelin Observatory, Svalbard. This evaluation illustrates challenges for inductive methods in distinguishing biomass burning from biological particles, and dust from SSA, suggesting that important particle classes may be missing and/or laboratory-generated aerosols significantly differ from real-world counterparts. We show that domain adaptation using complementary observations can help address these difficulties. Compared to a fluorescence-only approach, the domain-adapted algorithm reproduces the previously published annual bioaerosol cycle while yielding higher summertime concentrations matching those reported from offline analyses. This open-source algorithm provides a basis for quantifying bioaerosols across diverse environments and can be refined with future field and laboratory efforts.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"36 1","pages":"13617-13643"},"PeriodicalIF":6.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088331","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":"Molecular-level characterization of urban aerosol analogues in controlled atmospheric simulations","authors":"Elie Al Marj,Ambre Delater,Aline Gratien,Marie Line Torrijos,Juan Camilo Macias Rodriguez,Mathieu Cazaunau,Edouard Pangui,Antonin Bergé,Cécile Gaimoz,Thomas Bertin,Emmanuelle Mebold,Bénédicte Picquet-Varrault,Jean-François Doussin,Clément Buissot,Sophie Lanone,Patrice Coll","doi":"10.5194/acp-26-13645-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13645-2026","url":null,"abstract":"Urban air pollution consists of complex mixtures of gases and particulate matter. Understanding the molecular-level composition of these mixtures is essential for interpreting biological responses, but such characterization is difficult under ambient conditions. This study presents the chemical characterization of two controlled atmospheric scenarios generated in the CESAM smog chamber and transferred to the PolluRisk exposure isolator. The standard urban scenario consisted of selected anthropogenic and biogenic volatile organic compounds (VOCs) with primary ammonium sulphate seed particles. The biomass burning enhanced scenario included the same precursors and seed particles, with additional wood-pellet combustion emissions. Solar simulator was continuously turned on throughout the experimental periods and no day/night or dark-aging cycle was applied. Mean PM 1 concentrations in the exposed isolator were 15 ± 7 µg m −3 for the standard urban scenario and 63 ± 24 µg m −3 for the biomass burning scenario. Organic aerosol represented approximately 17 % and 40 % of PM 1 , respectively. Proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) identified 23 VOCs, with oxygenated compounds accounting for 74 %–77 %. Ultrahigh-performance liquid chromatography electrospray ionization ion mobility quadrupole time-of-flight mass spectrometry (UPLC/ESI-IMS-QTOFMS) revealed 32 distinct particle-phase compounds. The biomass burning scenario showed features compatible with combustion-related and oxidation-related products, including source-specific tracers such as a levoglucosan isomer, nitrophenolic compounds (e.g., 3-methyl-4-nitrocatechol, nitroguaiacol), and oxidized aromatics. Estimated volatility classes covered the semi-volatile, low-volatility, and extremely low-volatility organic compound ranges ( C ∗  < 300 µg m −3 ), indicating substantial functionalization and partitioning. The two simulated scenarios showed distinct compositions under the controlled operating conditions. These measurements provide a chemical framework for separate biological exposure experiments. This framework is intended to support mechanistic exposure-health studies, to be reported in a companion manuscript. However, the experiments were not designed to reproduce the full chemical composition of ambient urban air, determine an equivalent atmospheric age, or quantify the relative contributions of primary and secondary organic aerosol.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"8 1","pages":"13645-13660"},"PeriodicalIF":6.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149092292","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":"Origin of low ozone above western North America: an investigation of sources and trends","authors":"Ju-Mee Ryoo,Laura T. Iraci,Yu Yan Cui,Owen R. Cooper,Matthew S. Johnson,Kai-Lan Chang,Emma L. Yates,Valerie Thouret,Hanna Clark,Philippe Nedelec,Bastien Sauvage","doi":"10.5194/acp-26-13595-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13595-2026","url":null,"abstract":"While free-tropospheric ozone (O 3 ) over western North America (WNA) has increased since the mid-1990s, research has primarily focused on the mean. We investigate the lower tail (O 3  < 33rd percentile) to characterize the evolving remote background state. Because these air masses are minimally affected by episodic extremes, they offer a clearer window into long-term shifts in background O 3 , transport, and photochemistry. Using FLEXPART-ERA5 source–receptor relationships (SRRs) from 1994 to 2021, we analyze the transport history of air masses reaching WNA (25–55° N, 130–90° W). Despite no robust SRR trends within the lower and mid-troposphere (0–8 km), changing emission patterns suggest an intensifying remote influence. Specifically, WNA's surface NO x  emissions have decreased while lower-tail O 3 continues to rise, aligning with increasing surface emissions from Southeast Asia and intensified shipping. In contrast, UTLS (8–13 km) SRRs show a clear increase, indicating growing influence from high-altitude sources, including enhanced transport from Southeast Asia and the tropical Pacific, and rising global aircraft emissions. GMI chemical simulations corroborate these findings, revealing that net O 3 production over Southeast Asia increased by 157 % in the lower troposphere and 7 % in the free troposphere between 2007 and 2019. The rise in WNA's low O 3 percentiles is driven by the combined influence of intensified transport from Southeast Asia and the tropical Pacific, along with increasing global aircraft and shipping emissions. Ultimately, these trends reflect both the rapid growth of Southeast Asia emissions and shifting trans-Pacific transport.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"13 1","pages":"13595-13615"},"PeriodicalIF":6.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088332","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":"Impacts of South Asian aerosol inflow over Mount Qomolangma on downstream cloud–precipitation processes through a long-range ice-crystal “seeding” effect","authors":"Xiangde Xu,Wenyue Cai,Tianliang Zhao,Changjun Yang,Kai Meng,Chong Wu,Na Dong,Yueqing Li,Shunjiu Wang,Wenqing Liu,Tianshu Zhang,Ga Zhuo,Shengjun Zhang,Bin Chen,Chunsong Lu,Jinghua Chen,Kai Yang,Jianming Xu","doi":"10.5194/acp-26-13581-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13581-2026","url":null,"abstract":"Mount Qomolangma (MQ) serves as a natural laboratory for investigating aerosol–cloud–precipitation interactions over the Tibetan Plateau (TP). Using satellite and comprehensive ground-based observations, we identify pronounced ice-cloud activation associated with transported exogenous aerosols. Under different large-scale atmospheric circulation regimes, ice-phase cloud activated over MQ can be efficiently transported downstream through distinct pathways, exerting a pronounced ice crystal seeding effect on cloud–precipitation conversion. The spatial patterns of these downstream pathways are highly consistent with regions of enhanced ice-phase occurrence, precipitation, and upper-tropospheric latent heat release. This study provides new insight into the downstream impacts of aerosol transport through ice seeding for cloud precipitation. The findings highlight the important role of aerosol-induced ice-phase processes in modulating cloud and precipitation systems over the “Third Pole” and its downstream regions, with significant implications for understanding downstream extreme precipitation and environment change under South Asian increasing anthropogenic influences.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"8 1","pages":"13581-13593"},"PeriodicalIF":6.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149088330","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":"Climate impact of contrail cirrus from hydrogen combustion aircraft","authors":"Susanne M. Pettersson,Christian Azar,Daniel J. A. Johansson","doi":"10.5194/acp-26-13485-2026","DOIUrl":"https://doi.org/10.5194/acp-26-13485-2026","url":null,"abstract":"One possibility for reducing the climate impact of aviation is to transition to aircraft powered by hydrogen combustion. Hydrogen combustion leads to zero CO 2 exhaust emissions and represents a potential major step toward reduced climate impact, although the non-CO 2 effects (primarily contrail cirrus) remain uncertain. In this study, we simulate the climate impact, in terms of energy forcing, of contrail cirrus from hydrogen combustion aviation, using a modified version of the Contrail Cirrus Prediction model (CoCiP). With no soot in the exhaust, contrail ice particles mainly form on ambient aerosols entrained into the plume and on lubrication oil droplets in the exhaust. The formation of ice particles is modelled using an emulator developed from a theoretically based microphysical contrail formation model. Following the Schmidt-Appleman criterion, hydrogen combustion enables contrail formation at lower altitudes and higher temperatures than fossil jet fuel. However, we find a significant reduction in contrail energy forcing. This result holds across a wide range of assumptions, with a global average reduction of about 66 % using our base case assumptions on ambient aerosols, lubrication oil properties, droplet size distribution, emission index and energy efficiency of hydrogen aircraft. We conclude that hydrogen aircraft not only eliminate CO 2 emissions in the exhaust, but may also reduce the climate impact of contrail cirrus, depending on engine design for lubrication oil handling. However, we acknowledge that the modelling approach has limitations and uncertainties. Before firm conclusions can be drawn about the contrail cirrus effects of hydrogen-combustion aircraft, further studies are needed. These should include more realistic hydrogen aircraft models, alternative meteorological and microphysical models, and analyses of real-world flight patterns. In particular, measurements of lubrication-oil emissions from hydrogen aircraft under cruise conditions, as well as measurements of ice crystal number concentrations in hydrogen-aircraft contrails, would be valuable for constraining the present analysis.","PeriodicalId":8611,"journal":{"name":"Atmospheric Chemistry and Physics","volume":"15 1","pages":"13485-13503"},"PeriodicalIF":6.3,"publicationDate":"2026-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149049775","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}