Abstract The Clouds And Precipitation Experiment at Kennaook (CAPE-k) student workshop leveraged international scientific expertise as students explored data collected using advanced instrumentation during the CAPE-k campaign in Tasmania, Australia from April 2024 to October 2025. By linking the workshop directly to CAPE-k, we aimed to inspire the next generation of atmospheric scientists by exposing them to state-of-the-science instrumentation and the excitement that accompanies a major international campaign of this nature. We harnessed the enthusiasm and skills of the cohort of students to start the initial exploration of the CAPE-k data via four projects, which are presented by the students in this article, foreshadowing some of the exciting science to emerge from this campaign.

Global shipping fuel sulphur content regulations introduced in 2020 reduced the radiative cooling effects of sulfate aerosol over the ocean. Here we use the WRF-Chem model to estimate the effect these regulations have had on aerosols, clouds and solar radiation at the Great Barrier Reef, where climate change is increasing the frequency of mass coral bleaching events. During February 2022, the build-up to a La Niña mass coral bleaching event, we find 11 Wm−2 extra daytime downwards shortwave radiation reaches the reef post-sulfate regulation, compared to the control pre-regulation scenario. The enhancement is dominated by clear-sky-only forcing changes and less severe in cloudier and windier periods. Persistent incoming shortwave radiation enhancements on the order of 5-11 Wm−2 likely lead to sea-surface temperature increases of 0.05-0.15 °C, implying that during bleaching-conducive conditions, 5-10

BACKGROUND:Understanding interactions between the components of bundled mitigation measures can aid the prospective evaluation of hospital infection control programmes. This work provides a prospective, simulation-based examination of engineering controls (re-configured ventilation systems) designed to protect the healthcare workforce from airborne exposure on a ward for patients with acute respiratory infections such as coronavirus disease 2019 (COVID-19). METHOD:We developed and applied an agent-based computational model of nosocomial SARS-CoV-2 outbreaks to evaluate the combined effects of adding return ventilation in patient rooms (room-return ventilation) and a point-of-care N95 respirator policy where healthcare workers use respirators within patient rooms but do not wear them in other clinical areas (corridors and nurse stations). FINDING:By simulating COVID-19 transmission in the ward environment, our study demonstrates that modifications of air return configurations to limit the transport of viral quanta from patient rooms into adjacent corridors complement the effect of point-of-care respirator use, with synergistic effects. Indicative results show an increase in the benefit of N95 respirators on the time required for 50% of the ward's healthcare staff to become infected from 14.5 days 95% confidence interval (CI) [14.4, 14.7] (+262% [+260%, +265%]) using the baseline corridor-return ventilation configuration, to 40.1 days 95% CI [39.7, 40.4] (+576% [+570%, +581%]) using the modified room-return configuration, for a synergistic effect of more than two-fold. CONCLUSION:The benefit of bundling room-return ventilation with the point-of-care N95 respirator policy is approximately equivalent to requiring N95 respirator use in all clinical areas (patient rooms, corridors, and nurse stations) with corridor-return ventilation.

Ultrafine particles (UFPs), a key component of urban air pollution, pose serious health risks due to their ability to penetrate deep into the lungs, enter the bloodstream, and reach the brain via the olfactory system. While larger particles (PM10 and PM2.5) are well studied through extensive monitoring and modelling, UFPs-measured as particle number concentration (PNC)-remain poorly quantified worldwide, including in Australasia. Available data on UFP concentrations and size distributions are scarce, fragmented, and often based on short-term or single-site studies, largely due to monitoring challenges. This limits the ability to detect regional trends, assess urban influences, and design effective air quality policies. This study addresses this gap in knowledge by analysing one year of PNC and particle size distribution (PSD) data from four cities - Brisbane, Melbourne, Sydney, and Auckland - representing four distinct environments. Cross-city comparisons were conducted using PNC harmonised to a common size range, while temporal variability, pollutant associations, and dominant PSD regimes were examined within each city. Harmonised median PNC levels across the three Australian sites were comparable, whereas the Auckland roadside site exhibited higher PNC associated with local source proximity. Diel patterns showed persistent traffic-related peaks and intermittent midday enhancements associated with new particle formation that varied by site type and season. Seasonal peaks occurred during the colder months, likely due to reduced atmospheric mixing and combustion-related sources. Findings highlight the need for dedicated PNC monitoring networks to improve understanding, guide air quality management, and reduce health risks from particulate pollution in urban environments.

Characterizing black carbon (BC) on a fine scale globally is essential for understanding its climate and health impacts. However, sparse BC mass measurements in different parts of the world and coarse model resolution have inhibited evaluation of global BC emission inventories. Here, we apply globally distributed BC mass measurements from the Surface Particulate Matter Network (SPARTAN) and complementary measurement networks to evaluate contemporary BC emission inventories. We use a global chemical transport model (GEOS-Chem) in its high-performance configuration (GCHP) for high-resolution simulations to relate BC emissions to ambient concentrations for comparison with measurements. Here we find that simulations using the Community Emissions Data System (CEDS) emission inventory exhibit skill (r2 = 0.73) in representing variability in SPARTAN measurements across primarily developed regions with low BC concentrations but exhibit pronounced discrepancy (r2 = 0.00019) across high-BC regions in the Global South, underestimating BC by 38%. Alternative inventories (EDGAR, HTAP) yield similar results. These findings motivate renewed attention to the challenging task of characterizing BC emissions from low- and middle-income countries.

Bromine radicals released from sea ice, snow, and marine sources play a critical role in the atmospheric chemistry of polar regions. The Chemical and Mesoscale Mechanisms of Polar Cell Aerosol Nucleation (CAMMPCAN) ship campaign conducted in coastal East Antarctica over two 6-month periods in 2017-18 and 2018-19 provides a unique dataset to identify the environmental drivers of bromine variability in Antarctic spring and summer. In this study, we used CAMMPCAN chemical and meteorological observations combined with reanalysis data from the Modern Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) and satellite-based sea ice data from the National Snow and Ice Data Center to select variables that showed statistically significant correlation with bromine monoxide (BrO) partial columns measured during CAMMPCAN. We then used those variables in principal component analysis and subsequent principal component regression to identify dominant modes of Antarctic environmental variability and their impacts on lower tropospheric BrO. Comparing our three dominant Antarctic principal components to those from a similar analysis conducted previously for the Arctic (Swanson et al., 2020), we found only one mode with clear overlap, representing a vertical mixing mode in which low-pressure systems mix BrO and its precursors into the lower troposphere. We also identified an Antarctic mode describing conditions favourable for blowing snow, similar to the combined effect of two modes from the Arctic analysis but more clearly disambiguated here due to the inclusion of sea ice data in our analysis. The third Antarctic mode, attributed to an ocean source (biological activity and/or sea salt aerosol), was particularly important in summer. The principal component regression model developed from these modes showed moderate skill in predicting BrO partial columns in the lowest 2 km of the troposphere (R = 0.51), a significant improvement over the Arctic-based regression model (R = 0.08). Neither model could reproduce the observed variability in BrO in the lowest 200 m. Finally, we applied the same analysis to coincident CAMMPCAN observations of gaseous elemental mercury and found regression of our three dominant modes could explain nearly 50% of observed mercury variability (R = 0.69). Our results reinforce the importance of sea ice and ocean processes in bromine cycling in coastal East Antarctica and highlight the need to consider Antarctic-specific processes in mechanistic models of atmospheric bromine chemistry.

The interaction of natural marine aerosol with clouds and radiation is a significant source of climate model uncertainty. The Southern Ocean represents a key area to understand these interactions, and a region where significant model biases exist. Here we provide an evaluation of the Australian Community Climate and Earth System Simulator atmosphere model which includes a double-moment aerosol scheme. We evaluate against measurements of condensation nuclei (N10) and cloud condensation nuclei (CCN) number from seven ship campaigns and three terrestrial locations, spanning the years 2015-2019. We find that N10 is heavily underestimated in the model across all regions and seasons by more than 50 % and in some cases by over 80 % at higher latitudes. CCN is also strongly underestimated over marine and Antarctic regions, often by more than 50 %. We then perform seven sensitivity tests to explore different aerosol configurations. We find that updating the dimethyl sulfide climatology and turning on the primary marine organic aerosol flux marginally improves marine CCN by between 4 %-9 %. N10 was reduced by between 3 %-9 %. The Southern Ocean radiative bias is also reduced by this combination of changes, with limited adverse effects. We also test altering the sea spray flux to use wind gust instead of mean wind speed. This significantly improved CCN in the marine regions, but resulted in detrimental impacts on the region's radiation budget, indicating that drastically improving the Southern Ocean's CCN budget may lead to poorer simulations of the global climate.

BACKGROUND:Outbreaks of respiratory pathogens on hospital wards present challenges for control of hospital-acquired infections. AIM:To investigate the potential for synergistic effects between structural controls (single-occupancy patient rooms) and routine precautions (use of N95 respirators by healthcare staff), in preventing and mitigating outbreaks of airborne pathogens on hospital wards. METHODS:This study applied an agent-based extension of the Wells-Riley model of airborne pathogen exposure to simulate COVID-19 outbreaks on hospital wards. Secondary attack rates and the sizes of outbreaks resulting from introduction of unrecognized cases in hospital wards with double- or single-occupancy patient rooms were simulated. The impact of N95 respirator use by nurses during patient care activities was simulated, assuming an efficacy of 90% for protection and source control. FINDINGS:The size of simulated outbreaks recorded at day 14 was markedly lower in wards with only single-occupancy rooms, compared to double-occupancy rooms (with means of 14.1 and 22.8 infections, respectively). Nurses were more likely to acquire infection than patients for both single- and double-occupancy scenarios. Single occupancy was associated with smaller outbreak sizes, with a larger relative impact on patients than on staff. N95 respirators were effective at mitigating outbreaks, with higher impacts in wards with single-occupancy patient rooms. CONCLUSION:Our results are consistent with claims that single-occupancy patient rooms reduce transmission of SARS-CoV-2 on hospital wards. Our findings also support the claim that use of N95 respirators by nurses when caring for patients can reduce the effective reproductive ratio of the pathogen. Finally, we demonstrated that switching to single occupancy can increase the benefit of N95 respirator use by healthcare staff.

Aerosol vertical profile measurements were made using a Multi-Axis Differential Optical Absorption Spectrometer (MAX-DOAS) and Mini Micro Pulse Lidar (MPL) at One Tree Island in the Southern Great Barrier Reef from February to April 2023. This is an understudied location in terms of atmospheric aerosols and chemistry but is growing in importance as multiple research streams examine the influence of aerosols on radiation over the Great Barrier Reef. Solar radiation management proposals, such as marine cloud brightening, require regional-scale aerosol modelling, which is evaluated against aerosol extinction and optical depth measurements, necessitating a thorough understanding of measurements of these quantities. MPL aerosol retrieval showed extinction-to-backscatter ratios (0.031 on average) and depolarization ratios (0.015 on average) consistent with clean, unpolluted southern hemispheric marine aerosol. The maximum depolarization ratio tended to be above the layer of maximum MPL backscatter, consistent with dried sea salt layers above the boundary layer. MAX-DOAS and MPL extinction profiles show aerosol layers extending beyond 2 km altitude in the morning and to around 1 km in the afternoon. We run the MAX-DOAS retrieval at 360 and 477 nm simultaneously, using the Retrieval of Atmospheric Parameters from Spectroscopic Observations using DOAS Instruments (RAPSODI) algorithm, finding that this gives much better agreement with the vertically resolved diurnal cycle of aerosol extinction from the MPL. We also compared aerosol optical depth measurements from integrated MAX-DOAS and MPL extinction profiles, with observations from a hand-held Microtops sun photometer. Mean aerosol optical depth (AOD) values across the campaign compare well, being 0.084 +/- 0.003 for the Microtops, 0.090 +/- 0.040 for the MAX-DOAS and 0.091 +/- 0.025 for the MPL (smoothed to match the MAX-DOAS vertical sensitivity). The diurnal cycles of the smoothed MPL and the MAX-DOAS AOD agreed within uncertainty in most hours of the day, showing a morning peak and afternoon minimum in boundary layer aerosol amount. These measurements show that even in this challenging environment with frequent occurrences of low marine clouds and high humidity, MAX-DOAS (with dual-wavelength retrieval) and MPL provide robust methods for probing aerosol vertical distributions and optical depth in the lower troposphere.

Air pollution events pose significant challenges to public health in Melbourne and Sydney, Australia’s most populous cities. This study evaluates publicly available data to understand the frequency of air pollution exceedance events beyond World Health Organization (WHO) guidelines, as well as national and state standards. The air quality of both cities generally complies with national standards but consistently fails to meet WHO air quality guidelines. Since 2000, Sydney recorded single-pollutant events on 43% of monitored days and multi-pollutant events on 14% of monitored days. In Melbourne, single-pollutant events were recorded on 42% of monitored days, and multi-pollutant events on 8%. In Sydney, NO2 exceeded WHO guidelines on 52% of monitored days, PM2.5 on 13%, PM10 on 4%, and O3 on 6%. In Melbourne, NO2 exceeded on 47% of monitored days, PM2.5 on 4%, PM10 on 6%, and O3 on 2%. Evaluating long-term, city-scale air quality is challenging due to significant variations in spatial and temporal data coverage, especially in Melbourne. Many monitoring stations have limited temporal coverage and do not consistently monitor all key pollutants, meaning the true extent of air pollution is likely not fully captured. Since 2017, Melbourne has had only five active monitoring stations, compared to over 15 in Sydney. This study demonstrates the urgent need for expanded air pollution monitoring networks in Australia’s largest cities and highlights the need for ongoing research into the impacts of multi- as well as single-pollutant exceedance events.

The capture vaporizer (CV) was developed to reduce uncertainties in non-refractory aerosol composition measurements made using the aerosol mass spectrometer (AMS) and the aerosol chemical speciation monitor (ACSM). Use of the capture vaporizer has achieved this by improving the instruments' collection efficiency to similar to 1, but it has also lengthened the aerosol particles' residence times in the instrument, which has changed AMS and ACSM measurements using the standard vaporizer by altering known fragmentation patterns of organic marker species and increasing the likelihood of detecting refractory particles such as sea salt at typical operating temperatures (similar to 550 degrees C). This study reports that the changes affected by the capture vaporizer leads to sea salt particles interfering with measurements of biomass burning organic aerosols (BBOA) in environments where both particle sources are present as the ACSM's unit mass resolution is unable to distinguish between different molecules with the same molecular mass. Demonstration of this interference was performed using CV-Time of Flight-ACSM (CV-ToF-ACSM) measurements at two coastal Australian locations: the Kennaook-Cape Grim Baseline Air Pollution Station, Tasmania; and the site of the COALA-2020 (Characterizing Organics and Aerosol Loading over Australia 2020) campaign in New South Wales. Concentrations of BBOA marker ions m/z 60 and m/z 73 were examined at both locations, which showed two distinct branches of points: one where the two marker ions were positively correlated and one that was uncorrelated. This was due to m/z 60 also being a marker for sea salt. A threshold concentration of m/z 73 was established at each location to recognise periods where m/z 60 originated from BBOA. Lower concentrations of m/z 44 and radon when m/z 73 concentration was below the BBOA threshold indicated that m/z 60 concentration during these periods corresponded to inorganic particles of marine origin. Positive Matrix Factorization has also been shown to separate m/z 60 concentration from the two sources. This study suggests that using CV-ToF-ACSMs in coastal locations that are exposed to biomass burning smoke needs to consider sea salt interference when identifying BBOA. Measurements of biomass burning organic aerosols using the capture vaporizer-ACSM are interfered with by sea salt aerosols, as both have m/z 60 as a marker ion and the capture vaporizer is able to detect refractory particles like sea salt.

Abstract. The interaction of natural marine aerosol with clouds and radiation is a significant source of climate model uncertainty. The Southern Ocean represents a key area to understand these interactions, and a region where significant model biases exist. Here we provide an evaluation of the Australian Community Climate and Earth System Simulator atmosphere model which includes a double-moment aerosol scheme. We evaluate against condensation nuclei (N10) and cloud condensation nuclei (CCN) from seven ship campaigns and three terrestrial locations, spanning the years 2015–2019. We find that N10 is heavily underestimated in the model across all regions and seasons by more than 50 % and in some cases by over 80 % at higher latitudes. CCN is also strongly underestimated over marine and Antarctic regions, often by more than 50 %. We then perform seven sensitivity tests to explore different aerosol configurations. We find that updating the dimethyl sulfide climatology and turning on the primary marine organic aerosol flux marginally improves marine CCN by between 4–9 %. N10 however was reduced by between 3–9 %, resulting in worse model performance. The Southern Ocean radiative bias is also reduced by this combination of changes, with limited adverse effects. We also test altering the sea spray flux to use wind gust instead of mean wind speed, which significantly improved CCN in the marine regions, but resulted in detrimental impacts on the radiation budget. Our results indicate significant problems in the model’s microphysical processes and with over tuning. We suggest this needs to be addressed in a holistic way.

The planetary boundary layer height (PBLH) is an important meteorological feature defining the boundary between surface processes and the free troposphere. The PBLH plays a key role in cloud formation and the vertical extent of aerosols and air pollutants. Measurements of PBLH were made by meteorological sensors mounted to a multi-copter drone over the southern Great Barrier Reef, Australia. We then compared these drone-based measurements to remote-sensed PBLH observations, using a Mini-Micropulse (MP) LiDAR system. Across the measurement campaign (1 March-2 April 2023), the mean PBLH value using the drones was 801 +/- 203 m. Using the gradient method for MP LiDAR normalised relative backscatter profiles, the mean PBLH was 811 +/- 260 m. Using an ideal MP LiDAR profile fitting method the mean was 912 +/- 202 m and using a wavelet covariance transform method the mean was 862 +/- 298 m. The boundary layer was consistently well mixed, without convective instability or a strong diurnal PBLH cycle. The three MP LiDAR methods compared well to the drone measurements overall with Pearson's R correlation coefficients >0.60; however, estimates from the MP LiDAR were typically similar to 10% higher than from the drone. These results indicate congruence between the backscatter- and thermodynamically derived PBLH at One Tree Island, which is robust to variations in sampling conditions and the choice of MP LiDAR PBLH retrieval method.

Background Outbreaks of respiratory pathogens on hospital wards present a major challenge for control of hospital-acquired infections. When illness presentation is mild or infection is asymptomatic, isolation of recognised cases may be insufficient to prevent outbreaks, as unrecognised cases may be common. In such scenarios, structural controls such as the design of wards with single-occupancy patient rooms, or routine precautions such as the use of N95 respirators by healthcare staff can play an important role in preventing and mitigating outbreaks. Methods This study applies an agent-based extension of the Wells-Riley model of airborne pathogen exposure to simulate COVID-19 outbreaks on hospital wards. We simulated the impact of single-vs. double-occupancy patient rooms on secondary attack rates and the sizes of outbreaks resulting from introduction of unrecognised cases. We further simulated the impact of N95 respirator use by nurses during patient care activities, assuming an efficacy of 90% for protection and source control. Results In our simulations, the size of outbreaks recorded at day 14 was markedly lower in wards with only single-occupancy rooms, compared to double-occupancy rooms (with means of 15.2 and 25.1 infections, respectively). We found that nurses working on wards were more likely to acquire infection than patients. Higher patient room occupancy was associated with increased outbreak size, with a larger relative impact on patients than staff. N95 respirators were effective at mitigating outbreaks, with higher impacts in wards with single-occupancy patient rooms. Conclusions Single-occupancy rooms can greatly decrease the risk of hospital acquired airborne infection for patients. We show that single-occupancy hospital rooms can also reduce the number of healthcare workers infected during an outbreak of an airborne respiratory virus, but not to the same relative extent as patients. Due to the structural constraints limiting transmission between patients in different rooms, outbreaks were driven by transmission events involving nurses, which were effectively mitigated through the use of N95 respirators. Taken together, our results suggest that single-occupancy rooms are effective at reducing outbreak sizes. However, they are insufficient by themselves to prevent large outbreaks without mitigation efforts focused on limiting the potential for transmission involving healthcare workers, such as the use of N95 respirators. ### Competing Interest Statement SGS reports consulting for Astra Zeneca, CSL Seqirus, Evo Health, Moderna, Novavax, and Pfizer. ### Funding Statement This research was supported by the Medical Research Future Fund (MRFF) via a COVID-19 Treatment Access and Public Health Activities grant (Grant ID: MRF2017355). RS and JM are recipients of funding from ARC Industrial Transformation Training Centre (Grant ID: IC220100012). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced are available online at https://github.com/cjzachreson/ward\_model\_public [https://github.com/cjzachreson/ward\_model\_public][1] [1]: https://github.com/cjzachreson/ward_model_public

Global ground-level measurements of elements in ambient particulate matter (PM) can provide valuable information to understand the distribution of dust and trace elements, assess health impacts, and investigate emission sources. We use X-ray fluorescence spectroscopy to characterize the elemental composition of PM samples collected from 27 globally distributed sites in the Surface PARTiculate mAtter Network (SPARTAN) over 2019-2023. Consistent protocols are applied to collect all samples and analyze them at one central laboratory, which facilitates comparison across different sites. Multiple quality assurance measures are performed, including applying reference materials that resemble typical PM samples, acceptance testing, and routine quality control. Method detection limits and uncertainties are estimated. Concentrations of dust and trace element oxides (TEO) are determined from the elemental dataset. In addition to sites in arid regions, a moderately high mean dust concentration (6 μg/m3) in PM2.5 is also found in Dhaka (Bangladesh) along with a high average TEO level (6 μg/m3). High carcinogenic risk (>1 cancer case per 100000 adults) from airborne arsenic is observed in Dhaka (Bangladesh), Kanpur (India), and Hanoi (Vietnam). Industries of informal lead-acid battery and e-waste recycling as well as coal-fired brick kilns likely contribute to the elevated trace element concentrations found in Dhaka.

Background: Healthcare workers treating SARS-CoV-2 patients are at risk of infection by respiratory exposure to patient-emitted, virus-laden aerosols. Source control devices such as ventilated patient isolation hoods have been shown to limit the dissemination of non-infectious airborne particles in laboratory tests, but data on their performance in miti-gating the airborne transmission risk of infectious viruses are lacking.Aim: We used an infectious airborne virus to quantify the ability of a ventilated hood to reduce infectious virus exposure in indoor environments.Methods: We nebulized 109 plaque forming units (pfu) of bacteriophage PhiX174 virus into a w30-m3 room when the hood was active or inactive. The airborne concentration of infectious virus was measured by BioSpot-VIVAS and settle plates using plaque assay quantification on the bacterial host Escherichia coli C. The airborne particle number concentration (PNC) was also monitored continuously using an optical particle sizer.Findings: The median airborne viral concentration in the room reached 1.41 x 105 pfu/m3 with the hood inactive. When active, the hood reduced infectious virus concentration in air samples by 374-fold. The deposition of infectious virus on the surface of settle plates was reduced by 87-fold. This was associated with a 109-fold reduction in total airborne particle number escape rate.Conclusion: A personal ventilation hood significantly reduced airborne particle escape, considerably lowering infectious virus contamination in an indoor environment. Our find-ings support the further development of source control devices to mitigate nosocomial infection risk among healthcare workers exposed to airborne viruses in clinical settings. (c) 2023 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

The remoteness and extreme conditions of the Southern Ocean and Antarctic region have meant that observations in this region are rare, and typically restricted to summertime during research or resupply voyages. Observations of aerosols outside of the summer season are typically limited to long-term stations, such as Kennaook / Cape Grim (KCG; 40.7∘ S, 144.7∘ E), which is situated in the northern latitudes of the Southern Ocean, and Antarctic research stations, such as the Japanese operated Syowa (SYO; 69.0∘ S, 39.6∘ E). Measurements in the midlatitudes of the Southern Ocean are important, particularly in light of recent observations that highlighted the latitudinal gradient that exists across the region in summertime. Here we present 2 years (March 2016–March 2018) of observations from Macquarie Island (MQI; 54.5∘ S, 159.0∘ E) of aerosol (condensation nuclei larger than 10 nm, CN10) and cloud condensation nuclei (CCN at various supersaturations) concentrations. This important multi-year data set is characterised, and its features are compared with the long-term data sets from KCG and SYO together with those from recent, regionally relevant voyages. CN10 concentrations were the highest at KCG by a factor of ∼50 % across all non-winter seasons compared to the other two stations, which were similar (summer medians of 530, 426 and 468 cm−3 at KCG, MQI and SYO, respectively). In wintertime, seasonal minima at KCG and MQI were similar (142 and 152 cm−3, respectively), with SYO being distinctly lower (87 cm−3), likely the result of the reduction in sea spray aerosol generation due to the sea ice ocean cover around the site. CN10 seasonal maxima were observed at the stations at different times of year, with KCG and MQI exhibiting January maxima and SYO having a distinct February high. Comparison of CCN0.5 data between KCG and MQI showed similar overall trends with summertime maxima and wintertime minima; however, KCG exhibited slightly (∼10 %) higher concentrations in summer (medians of 158 and 145 cm−3, respectively), whereas KCG showed ∼40 % lower concentrations than MQI in winter (medians of 57 and 92 cm−3, respectively). Spatial and temporal trends in the data were analysed further by contrasting data to coincident observations that occurred aboard several voyages of the RSV Aurora Australis and the RV Investigator. Results from this study are important for validating and improving our models and highlight the heterogeneity of this pristine region and the need for further long-term observations that capture the seasonal cycles.