Journal of Geophysical Research: Atmospheres最新文献

{"title":"Wet Deposition of Black Carbon: Insights From a Comparative Study of Char/Soot in PM10 and Rainwater","authors":"Xiaocong Peng,&nbsp;Yuzhen Fu,&nbsp;Guohua Zhang,&nbsp;Wei Sun,&nbsp;Jinting Huang,&nbsp;Ziyong Guo,&nbsp;Juying Lin,&nbsp;Jianzhong Song,&nbsp;Xinming Wang,&nbsp;Ping'an Peng,&nbsp;Xinhui Bi","doi":"10.1029/2024JD043095","DOIUrl":"https://doi.org/10.1029/2024JD043095","url":null,"abstract":"<p>Wet scavenging of black carbon (BC) is essential for evaluating their atmospheric lifetime and radiative forcing. However, it is crucial to differentiate atmospheric BC into char and soot subgroups, given their significant disparities in physicochemical properties and potential impacts. We first conducted a comparative study of char/soot in PM₁₀ and rainwater, collected over a year in urban Guangzhou, China. The mean char/soot ratio in PM₁₀ (∼2.5) is obviously higher than that in rainwater (∼0.8), corresponding to higher wet scavenging efficiency of soot. Through sequence rainwater sampling during individual rainfall events, we further distinguished the contributions of in-cloud and below-cloud scavenging, with in-cloud scavenging predominantly contributed to the distinct difference between char and soot. Such a distinct wet scavenging behavior of char and soot would have substantial implications for the atmospheric behavior of BC, which should be considered in future models for accurate evaluation of its lifetime and climate impact.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the Indian Walker Circulation on \u0000 \u0000 \u0000 δ\u0000 \u0000 $delta $\u0000 18OP and Hydroclimate Variability in the Indian Ocean Basin","authors":"Patrick G. Cho,&nbsp;Georgina Falster,&nbsp;Diogo Bolster,&nbsp;Melissa A. Berke,&nbsp;Marc F. Müller","doi":"10.1029/2025JD043840","DOIUrl":"https://doi.org/10.1029/2025JD043840","url":null,"abstract":"<p>The Indian Ocean plays a crucial role in water cycle dynamics around the Indian Ocean Basin, yet the relationships between the Indian Walker Circulation (IWC) and hydroclimate variability remain poorly understood. We examine the IWC-hydroclimate linkages throughout the Indian Ocean Basin during two study periods (instrumental era and the last millennium), using the ECHAM5-wiso, iCESM-iLME, and ERA5 global data products. We leverage the stable isotopic composition of precipitation (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>δ</mi>\u0000 </mrow>\u0000 <annotation> $delta $</annotation>\u0000 </semantics></math>¹⁸O_P) as an integrative water cycle tracer to elucidate the link between large-scale atmospheric processes and regional hydroclimate characteristics. We find a strong statistical relationship between the East African short rain <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>δ</mi>\u0000 </mrow>\u0000 <annotation> $delta $</annotation>\u0000 </semantics></math>¹⁸O_P and IWC in Eastern Africa and Horn of Africa. In Indonesia, the relationship is weaker due to the strong influence of the Pacific Walker Circulation (PWC). These patterns arise over multiple time scales and are consistent with the strong tie between the IWC and precipitation variability during the short rain season in Eastern Africa and Horn of Africa that had previously been reported in the instrumental era but not yet for the last millennium. We document strong fluctuations in the strength of the IWC during the last millennium, with periods of stronger or weaker interactions with the PWC that influenced <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>δ</mi>\u0000 </mrow>\u0000 <annotation> $delta $</annotation>\u0000 </semantics></math>¹⁸O_P variability. Finally, our study underscores the ability of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>δ</mi>\u0000 </mrow>\u0000 <annotation> $delta $</annotation>\u0000 </semantics></math>¹⁸O_P to capture major atmospheric circulation signals, demonstrating its potential to examine the impact of interacting Walker Circulations on regional hydroclimate even during periods of low precipitation.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JD043840","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865857","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":"Resonant Asian Monsoon During Intermediate Conditions of the Last Deglaciation: Insights From Speleothem Records","authors":"Jingyao Zhao,&nbsp;Carlos Pérez-Mejías,&nbsp;Xiyu Dong,&nbsp;Yassine Ait Brahim,&nbsp;Jiahui Cui,&nbsp;Liangkang Pan,&nbsp;Xi Chen,&nbsp;Kexin Wang,&nbsp;Yan Yang,&nbsp;Jun Cheng,&nbsp;Haiwei Zhang,&nbsp;Liangcheng Tan,&nbsp;Hai Cheng","doi":"10.1029/2024JD042523","DOIUrl":"https://doi.org/10.1029/2024JD042523","url":null,"abstract":"<p>Extensive research has explored how sweet spot conditions influence climate variability in the nonlinear Earth system. However, their effects throughout deglaciations remain unclear. Based on an annual-laminated speleothem δ¹⁸O record with unprecedented chronology precision, we first identified a two-step termination of the Asian Heinrich Period-1 at 15.11 and 14.69 ky BP (thousand years before present, where the present is 1950 CE), each marked by a centennial-scale strengthening of the Asian summer monsoon (ASM), in contrast to centennial-scale ASM weakening events observed at 17.8 and 16.09 ky BP. These transitions occurred under intermediate CO₂ and ice volume conditions, which dynamically paced the Atlantic Meridional Overturning Circulation (AMOC) fluctuations and the subsequent reoccurrence of ASM events. It highlights the role of stochastic resonance in nonlinear climate system. Additionally, these AMOC/ASM events also resonated with abrupt CO₂ risings across various pervasive modes of variability, which account for half of total CO₂ rise during last deglaciation. This substantial contribution to CO₂ increases played a key role in ice termination.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865856","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":"Observed Links Between Atmospheric Cloud Radiative Effects and Mesoscale Organization of Deep Convection","authors":"Ni Dai,&nbsp;Hui Su,&nbsp;J. David Neelin,&nbsp;Brian J. Soden,&nbsp;Yi-Hung Kuo","doi":"10.1029/2024JD041030","DOIUrl":"https://doi.org/10.1029/2024JD041030","url":null,"abstract":"<p>Recent research suggests atmospheric cloud radiative effect (ACRE) acts as an important feedback mechanism for enhancing the development of convective self-aggregation in idealized numerical simulations. Here, we seek observational relationships between longwave (LW) ACRE and the spatial organization of mesoscale convective systems (MCSs) in the tropics. Three convective organization metrics that are positively correlated with the area of MCS, that is, convective organization potential, the area fraction of precipitating MCS, and the precipitation fraction of MCS, are used to indicate the degree of convective organization. Our results show that the contrast in the LW ACRE inside and outside an MCS is consistent across different MCS precipitation intensities throughout the life cycle of an MCS, typically 90–100 W/m², and provides important positive feedback to the circulation of the given MCS. However, the LW ACRE inside and outside an MCS as well as their difference are not strongly related to the degree of organization, suggesting that the LW cloud radiative feedback may be supportive of MCS formation and maintenance without necessarily being a dominant factor for spatial organization of MCSs. The domain average vertical velocity does tend to be related to the measures of convective organization, suggesting that factors that favor large-scale low-level convergence may exert a leading effect in creating an environment favorable for mesoscale organization of deep convection.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041030","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143865855","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":"Characteristics of Global Light Rain System From GPM/DPR Measurements","authors":"Seoeun Choi,&nbsp;Jihoon Ryu,&nbsp;Sang-Moo Lee,&nbsp;Byung-Ju Sohn","doi":"10.1029/2024JD042434","DOIUrl":"https://doi.org/10.1029/2024JD042434","url":null,"abstract":"<p>Understanding the microphysical and macrophysical characteristics of global light rain (0.2–2.5 mm/hr) is important for modeling the hydrological cycle and enhancing the cloud-related parameterization in the numerical weather prediction (NWP) model. To understand the characteristics of light rain systems, this study classified global light rain events using the Global Precipitation Measurement Dual-frequency Precipitation Radar measurements over the 8–years period. As a result, global light rain systems were identified into four types based on microphysical (mass-weighted mean diameter (<i>D</i>_<i>m</i>) and normalized intercept parameter (log<i>N</i>_<i>w</i>)) and macrophysical (cloud-echo-top height (CETH)) parameters. The four classified types are (a) Type 1: light rain dominant in tropics and mid-latitude, (b) Type 2: light rain linked to atmospheric deep convection, (c) Type 3: light rain from humid oceanic inflow blocked by topography, and (d) Type 4: light rain associated with subtropical high-pressure systems. Type 2 shows the largest <i>D</i>_<i>m</i> and the smallest log<i>N</i>_<i>w</i>, while Type 4 exhibited opposite patterns. Type 3 has the highest CETH and vertically stretching radar reflectivity profiles. Type 1 showed similar distributions of <i>D</i>_<i>m</i> and log<i>N</i>_<i>w</i> with Type 3 and radar reflectivity with Type 4 but different distributions of hydrometeor phase with Types 3 and 4. To clarify the characteristics of Type 1, a detailed analysis was conducted, showing larger <i>D</i>_<i>m</i> and log<i>N</i>_<i>w</i>, higher radar reflectivity, and stronger seasonality in tropical regions compared to mid-latitudes. This study provides valuable insights into geospatial/statistical characteristics of global light rain, which is expected to enhance the accuracy of cloud parameterization in the NWP model.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD042434","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143861769","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":"Impact of MJO Seasonality on the Intensification of Intraseasonal PNA During El Niño and La Niña Winters","authors":"Shenghua Jian,&nbsp;Fang Zhou,&nbsp;Minghong Liu,&nbsp;Jian Shi","doi":"10.1029/2025JD043818","DOIUrl":"https://doi.org/10.1029/2025JD043818","url":null,"abstract":"<p>This study mainly examined the distinct early-to-late winter variations in the intraseasonal Pacific–North American teleconnection mode (ISPNA) under the two El Niño–Southern Oscillation phases. Results showed that these variations were controlled by the Madden–Julian Oscillation (MJO) seasonality. Compared to El Niño winters, the ISPNA exhibits a stronger early-to-late winter enhancement during La Niña winters. Furthermore, the MJO and the ISPNA exhibit a phase-locked relationship, which is more pronounced and reliable in late winter. The Rossby wave activity associated with the MJO that propagates northward from the tropics toward the subtropical action center of the ISPNA indicates that increased MJO activity contributes to greater ISPNA intensity. The MJO also exhibits clear seasonality, exhibiting enhancement from early winter to late winter, which is particularly evident during La Niña winters and results in intensified ISPNA during these periods.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850982","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":"Preliminary Breakdown Process of Winter Positive Cloud-To-Ground Lightning and Its Relation to the Following First Return Stroke","authors":"Qingliu Yang,&nbsp;Daohong Wang,&nbsp;Ting Wu","doi":"10.1029/2024JD041496","DOIUrl":"https://doi.org/10.1029/2024JD041496","url":null,"abstract":"<p>We have studied the preliminary breakdown (PB) process and its relation to the following positive first return stroke (RS) for 60 winter positive cloud-to-ground (+CG) lightning flashes using their 3D mapping data by Discone Antenna Lightning Mapping Array in conjunction with the E-field change information by Fast Antenna Lightning Mapping Array. 31 (52%) PBs are found to propagate upward, 27 (45%) downward, and the remaining 2 (3%) with some initial progression direction reversal features. The winter +CG PBs can be characterized with an initiation height from 0.9 to 4.4 km, a propagation distance from 0.2 to 2.6 km, a propagation speed from <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>3</mn>\u0000 <mo>.</mo>\u0000 <mn>5</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mn>5</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> $3.5times {10}^{5}$</annotation>\u0000 </semantics></math> to <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>5.4</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mn>6</mn>\u0000 </msup>\u0000 </mrow>\u0000 <annotation> $5.4times {10}^{6}$</annotation>\u0000 </semantics></math> m/s without significant differences between upward and downward PBs. The time interval and the 2D displacement distance from the PB initiation to the first RS range from 6.1 to 603.7 ms, from 0 to 39.2 km, respectively. Return strokes with strongest intensities tend to have shorter intervals and 2D displacements between PB and RS. We also found some weak correlations between the PB characteristic parameters. All 60 +CGs involved multiple charge regions with opposite polarities and small separations. Finally, we have discussed our findings.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041496","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850971","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":"Summertime Carbonaceous Aerosol in Interior Versus Coastal Northern Alaska","authors":"Allison M. Welch,&nbsp;Tate Matthews,&nbsp;Rebecca J. Sheesley,&nbsp;Hui Wang,&nbsp;Kelley C. Barsanti,&nbsp;Nicole Nielsen,&nbsp;Xiaomei Xu,&nbsp;Lurui Niu,&nbsp;Alex B. Guenther,&nbsp;Claudia I. Czimczik","doi":"10.1029/2024JD042080","DOIUrl":"https://doi.org/10.1029/2024JD042080","url":null,"abstract":"<p>Rapid warming is likely increasing primary production and wildfire occurrence in the Arctic. Projected changes in carbonaceous aerosols during the summer will impact atmospheric chemistry and climate, but our understanding of these processes is limited by sparse observations. Here, we characterize carbonaceous aerosol in Alaska, USA: Toolik Field Station in the Interior and the Atmospheric Radiation Measurement facility at Utqiaġvik on the Arctic coast, during the summers of 2022 and 2023. We estimated PM_2.5 and PM₁₀ concentrations using laser light scattering (PurpleAir sensors) and examined total carbon (TC) and its organic carbon (OC) and elemental carbon (EC) fractions in total suspended particles (TSP). We investigated the dominant sources of carbonaceous aerosol using air mass backward-trajectories from the NOAA HYSPLIT model and radiocarbon source apportionment of TC. TC concentrations were about twice as high in the Interior compared to the coast, with contemporary sources dominating at both Toolik (95%–99%) and Utqiaġvik (86%–89%) over minor contributions from fossil sources. Elevated PM, TC, OC, and EC concentrations coincided with major boreal forest fire activity in North America that brought smoke to the region. The radiocarbon signature of EC measured at Toolik during these wildfire events indicated that over 90% of the EC came from contemporary sources. Our measurements demonstrate the potential for Arctic aerosol concentrations to respond significantly to climate warming-induced changes to the landscape and emphasize the need for continuous atmospheric monitoring to advance our understanding of this rapidly changing environment.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD042080","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850980","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":"Atmospheric HONO Observed Over Global Biomass Burning Regions Using Satellite Observations of TROPOMI and GEMS","authors":"N. Theys,&nbsp;H. Yu,&nbsp;B. Franco,&nbsp;L. Clarisse,&nbsp;R. Volkamer,&nbsp;H. Cha,&nbsp;J. Kim,&nbsp;I. De Smedt,&nbsp;T. Stavrakou,&nbsp;J. van Gent,&nbsp;M. Van Roozendael","doi":"10.1029/2024JD043163","DOIUrl":"https://doi.org/10.1029/2024JD043163","url":null,"abstract":"<p>Nitrous acid (HONO) is a key tropospheric species primarily due to ist role as a source of the hydroxyl radical (OH), which is pivotal in breaking down pollutants and greenhouse gases and is also a key ingredient to photochemical air pollution. Recent HONO measurements from space in fresh biomass burning plumes offer the potential to inform about HONO formation mechanisms globally. However, research is needed to further develop, interpret, and evaluate the satellite retrievals. Here, we present a new global HONO column data set of 5.5 years from the TROPOspheric Monitoring Instrument (TROPOMI). We leverage the Covariance-Based Retrieval Algorithm to significantly improve the sensitivity to weak HONO signals over all biomass burning regions. Radiative transfer simulations for retrieving HONO columns indicate a strong dependence on plume height and smoke aerosols. Such information is mostly inaccessible from space for thick plumes but can be obtained from suborbital measurements during dedicated campaigns. We compare the TROPOMI HONO columns to aircraft observations from the BB-FLUX campaign. When explicitly accounting for aerosols, the satellite and aircraft data are in good agreement albeit with significant comparison uncertainty. We also evaluate the TROPOMI retrievals against HONO columns measured by IASI and discuss the differences. Next, we demonstrate the potential of geostationary satellites like the Geostationary Environment Monitoring Spectrometer to provide temporally resolved information on pyrogenic HONO. Finally, we find a close relationship between satellite HONO detections and fire intensity both in space and time, highlighting the likely dominance of HONO production during the flaming phase of the fires.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850981","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":"Marine Boundary Layer Cloud Condensation Nuclei Bias Over the Southern Ocean: Comparisons Between the Community Atmosphere Model 6 and Field Observations","authors":"Qing Niu,&nbsp;Christina McCluskey,&nbsp;Greg M. McFarquhar","doi":"10.1029/2024JD042734","DOIUrl":"https://doi.org/10.1029/2024JD042734","url":null,"abstract":"<p>Marine boundary layer (MBL) clouds play a crucial role in regulating radiative balance in the atmosphere. Previous studies identified that MBL cloud droplet number concentration (Nd) is underestimated by a factor of 2 over the summertime Southern Ocean (SO) close to the Antarctic coast in many models. Here, comparisons between cloud condensation nuclei (CCN) observations from field campaigns during the 2017–2018 Austral summer over the Australasian sector of the SO and simulated CCN from the Community Atmospheric Model 6 (CAM6) are presented. Modeled MBL CCN number concentration (N_CCN) is underestimated, by close to 100% at latitudes south of 55°S with the N_CCN bias (a) largest close to the Antarctic Plateau during summer, implying the biased CCN type has seasonal and latitudinal variation and, (b) three times larger over sea ice than over open water, implying sea spray CCN are better simulated compared to secondary CCN. Assessments of aerosol size distributions indicate an underestimation of accumulation-mode-aerosols (Ac) with diameters 70 nm &lt; D &lt; 100 nm. CCN supersaturation spectra indicate that the observed CCN had lower hygroscopicity compared to simulated CCN, implying differences in CCN chemical composition. With secondary aerosols including sulfate being less hygroscopic than sea salt CCN, the CCN activation ratio derived using bulk hygroscopicity kappa in the Abdul-Razzak function leads to an underestimation of critical supersaturation south of 62°S. The biases reported here highlight important shortfalls in simulated CCN that can be important to the well-documented underestimated <i>N</i>_d by Earth System Models, a key feature and uncertainty of pre-industrial conditions.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 8","pages":""},"PeriodicalIF":3.8,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850983","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}