Browsing by Author "Miljevic, B"

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    Comprehensive aerosol and gas data set from the Sydney Particle Study
    (Copernicus Publications, 2019-12-02) Keywood, MD; Selleck, PW; Reisen, F; Cohen, DD; Chambers, SD; Cheng, M; Cope, M; Crumeyrolle, S; Dunne, E; Emmerson, K; Fedele, R; Galbally, IE; Gillett, R; Griffiths, AD; Guerette, EA; Harnwell, J; Humphries, R; Lawson, S; Miljevic, B; Molloy, SB; Powell, J; Simmons, J; Ristovksi, Z; Ward, J
    The Sydney Particle Study involved the comprehensive measurement of meteorology, particles and gases at a location in western Sydney during February–March 2011 and April–May 2012. The aim of this study was to increase scientific understanding of particle formation and transformations in the Sydney airshed. In this paper we describe the methods used to collect and analyse particle and gaseous samples, as well as the methods employed for the continuous measurement of particle concentrations, particle microphysical properties, and gaseous concentrations. This paper also provides a description of the data collected and is a metadata record for the data sets published in Keywood et al. (2016a, https://doi.org/10.4225/08/57903B83D6A5D) and Keywood et al. (2016b, https://doi.org/10.4225/08/5791B5528BD63). © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 Licence.
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    Marine productivity and synoptic meteorology drive summer-time variability in Southern Ocean aerosols
    (Copernicus Publications, 2020-07-10) Alroe, J; Cravigan, LT; Miljevic, B; Johnson, GR; Selleck, PW; Humphries, RS; Keywood, MD; Chambers, SD; Williams, AG; Ristovski, ZD
    Cloud–radiation interactions over the Southern Ocean are not well constrained in climate models, in part due to uncertainties in the sources, concentrations, and cloud-forming potential of aerosol in this region. To date, most studies in this region have reported measurements from fixed terrestrial stations or a limited set of instrumentation and often present findings as broad seasonal or latitudinal trends. Here, we present an extensive set of aerosol and meteorological observations obtained during an austral summer cruise across the full width of the Southern Ocean south of Australia. Three episodes of continental-influenced air masses were identified, including an apparent transition between the Ferrel atmospheric cell and the polar cell at approximately 64∘ S, and accompanied by the highest median cloud condensation nuclei (CCN) concentrations, at 252 cm−3. During the other two episodes, synoptic-scale weather patterns diverted air masses across distances greater than 1000 km from the Australian and Antarctic coastlines, respectively, indicating that a large proportion of the Southern Ocean may be periodically influenced by continental air masses. In all three cases, a highly cloud-active accumulation mode dominated the size distribution, with up to 93 % of the total number concentration activating as CCN. Frequent cyclonic weather conditions were observed at high latitudes and the associated strong wind speeds led to predictions of high concentrations of sea spray aerosol. However, these modelled concentrations were not achieved due to increased aerosol scavenging rates from precipitation and convective transport into the free troposphere, which decoupled the air mass from the sea spray flux at the ocean surface. CCN concentrations were more strongly impacted by high concentrations of large-diameter Aitken mode aerosol in air masses which passed over regions of elevated marine biological productivity, potentially contributing up to 56 % of the cloud condensation nuclei concentration. Weather systems were vital for aerosol growth in biologically influenced air masses and in their absence ultrafine aerosol diameters were less than 30 nm. These results demonstrate that air mass meteorological history must be considered when modelling sea spray concentrations and highlight the potential importance of sub-grid-scale variability when modelling atmospheric conditions in the remote Southern Ocean. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
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    Sydney particle study: overview and motivations
    (The Centre for Australian Weather and Climate Research, 2011-11-15) Keywood, MD; Gallaby, I; Cope, M; Boast, K; Chambers, SD; Cheng, M; Dunne, E; Fedele, R; Gillett, R; Griffiths, AD; Lawson, S; Miljevic, B; Molloy, SB; Powell, J; Reisen, F; Ristovski, Z; Selleck, PW; Ward, J
    Studies of health impacts from atmospheric pollutants suggest that particles are currently one of the most significant pollutants with respect to human mortality and morbidity. However, reduction in particle concentrations through source regulation is challenging due to the large number particle sources (both natural and anthropogenic) present in an airshed, and the wide range of particle sizes and chemical species emitted. Additionally, secondary particles can also make a significant contribution to total particle exposure, particularly in the fine size fraction which is considered to have the largest impact on health. Being generated through photochemical processes (similar to ozone), a reduction in the concentration of secondary particles requires that source regulators also consider the relevant gas-phase precursors to these particles. Climate change projections for NSW suggest significant increases in the frequency of drought, increases in the frequency of hot days and increases in the frequency of high fire risk weather. This has important ramifications for air pollution and health, with atmospheric particle smog severity linked to the frequency of hot, sunny days, and with the highest particle pollution concentrations linked to the presence of bushfire plumes in the Sydney airshed. Particles and ozone are also coupled, with enhanced ozone concentrations often observed on bushfire days and with 50% or greater of fine particle mass potentially of photochemical origin. The development of a long term control strategy for particles in Sydney can be informed through the use of comprehensive three-dimensional simulations of the atmosphere, sources and multi-phase phase chemistry. However the development of such modelling capability requires a good understanding of the contribution made by local and remote particles sources to the total particle exposure within the region. Such understanding requires detailed and high quality data sets. We present here an overview of the Sydney Particle Study, a combined modelling and observation project which included an intensive field campaign of aerosol and aerosol precursor measurements carried out in Sydney during February 2011. We focus our discussion on the field campaign which combined sophisticated measurement techniques to produce a high quality data set of atmospheric composition observations. The campaign was a collaboration 43between CSIRO Marine and Atmospheric Research, NSW Office of Environment and Heritage, Queensland University of Technology and ANSTO. Data collected included criteria pollutant concentrations, aerosol microphysical properties, aerosol chemical composition (as a function of size, integrated over 4 hours and in real time), concentration of volatile organic compounds (integrated over 4 hours and in real time) and radon concentrations. Continuous aerosol size distributions indicated the occurrence of secondary aerosol formation occurring in the afternoons on approximately 50% of the days sampled. Data analysis continues in order to understand the processes driving this secondary formation. © 2011 CSIRO and the Bureau of Meteorology.