ANSTO :: Browsing by Author "Williams, AG"

Browsing by Author "Williams, AG"

Now showing 1 - 20 of 70

20 year Australian Antarctic strategic plan
(Australian Government Department of the Environment and Energy, 2014-07) Williams, AG; Chambers, SD; Smith, AM
40 years of atmospheric composition observations and research at Cape Grim – an overview
(Australian Meteorological & Oceanographic Society, 2016-02-08) Krummel, PB; Keywood, MD; Fraser, PJ; Galbally, IE; Steele, PL; Lawson, S; van der Schoot, MV; Wilson, SR; Williams, AG; Cleland, S
In 2016, the Cape Grim station located at the north-west tip of Tasmania, will celebrate 40 years of continuous operation. Commencing operations in 1976, and in its current facilities since 1981, the Baseline Air Pollution Station at Cape Grim is Australia’s contribution to international efforts for monitoring the global background atmosphere for trends due to human activities and natural variability. It is one of the three premier stations in the Global Atmosphere Watch (GAW) network of the World Meteorological Organization (WMO). Cape Grim observations thereby contribute very significantly to the GAW programme, and research outputs are published in peer-reviewed international journals of the highest quality, are very frequently cited, and feed into the international/global assessments, for example the IPCC. Cape Grim’s essential purpose has not changed since the program’s inception in 1976. National and global concern that human activity is having an impact on the composition of the global (and regional) atmosphere requires that the changes be observed and understood. Initially, this was the main focus, whereas now the data are also used for prediction, to guide development of remedial policies, and to verify the effectiveness of global mitigation actions. The critical, but too often unrecognised role of precise in-situ atmospheric observation programs underpinning our current understanding of atmospheric processes and ability to model future climate, is well summarised in a commentary in Nature, titled “Cinderella science” (Nature 450, p789, 2007). The Cape Grim station is operated and funded by the Aust. Bureau of Meteorology, with the Cape Grim Science Program jointly supervised by CSIRO, the Bureau of Met., Univ. of Wollongong and ANSTO. This presentation will give an overview of the past and present measurement programs at the station, show some of the iconic long-term datasets, and summarise some of the science highlights and impacts from the past 40 years.
Aerosol iron solubility: comparison between the Australian subtropics and Southern ocean
(Bureau of Meteorology and CSIRO Oceans and Atmosphere Flagship, 2014-11) Winton, H; Edwards, R; Bowie, A; Chambers, SD; Keywood, MD; Werczynski, S; Williams, AG
Past changes in the atmospheric deposition of soluble, or bioavailable, trace metals to high nutrient low chlorophyll (HNLC) and nitrogen replete tropical waters have been shown to modulate primary production, atmospheric CO2, and global climate. The deposition of soluble trace metals can also trigger toxic algal blooms, which impact Australia’s fisheries and coral reefs. An understanding of the sources (e.g. mineral dust and biomass emissions) and geochemistry of soluble trace metals in atmospheric aerosols is critical for determining the impact of trace metal deposition on ocean fertility in the past and the future. However, to date no trace metal solubility data exists for biomass emissions from Australian fires and there are very few estimates of soluble trace metal aerosols entering the Southern Ocean. Trace metal clean aerosols were collected during the early‐late dry season experiment at Gunn Point, Northern Territory to investigate the trace metal aerosol solubility associated with biomass burning. Previous studies have suggested that mineral dust is the dominant source of trace metal aerosol. However, mineral dust is relatively insoluble and a significant fraction of soluble trace metals in the atmosphere could originate from biomass burning rather than mineral dust. Here we use the combination of soluble aerosol chemistry, back trajectories and diurnal and advective radon components to identify trace metal source regions throughout the campaign duration. We compare aerosol iron solubility at Gunn Point in the subtropics, where biomass burning can dominate the aerosol load in the dry season, to iron solubility in baseline air at Cape Grim which is representative of the Southern Hemisphere background. In doing this we highlight the importance of aerosol source at different latitudes for the solubility and bioavailability of trace metals.
ANSTO AMS facility sample processing and target preparation: an update
(20th International Radiocarbon Conference, 2009-06-01) Jacobsen, GE; Barry, LA; Bertuch, F; Hua, Q; Mifsud, C; Pratap, P; Reilly, N; Varley, S; Williams, AG
The ANSTO AMS Facility has been operating for the past 17 years, and comprises two accelerators complemented with a suite of chemistry laboratories dedicated to the processing of samples for carbon, beryllium, aluminium, iodine, and actinide analyses. The facility performs and supports a wide range of research in the areas of paleoclimate change, water resource sustainability, archaeology, geomorphology, and nuclear safeguards. As a result, the chemistry laboratories are called upon to process a large variety of sample types and increasing numbers of samples. The radiocarbon laboratories process charcoal, wood, sediments, pollen, carbonates, waters, textiles, and bone though the pretreatment stages, combustion or hydrolysis, and graphitization. Over the years, we have continually worked to improve pretreatment methods, reduce sample size, and reduce background. Construction of a dedicated low-background combustion and graphitization system is underway. The cosmogenic laboratories process quartz-bearing rocks and sediments through cleaning, dissolution, separation, and purification of Be and Al and preparation of targets as oxides. In this poster, we will summarize the current methods and developments in the radiocarbon and cosmogenic chemistry laboratories.
ANSTO radon measurements at Cape Grim and other global atmospheric monitoring sites
(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-09) Williams, AG; Chambers, SD
Not supplied to the ANSTO Library.
Application for 222Rn in atmospheric research
(Australian Nuclear Science and Technology Organisation, 2012-10-16) Chambers, SD; Williams, AG; Zahorowski, W; Griffiths, AD
Radon-222 (radon) is a relatively short-lived (half-life 3.82 d), naturally occurring, radioactive gas, with a relatively consistent and well-defined terrestrial flux, and almost negligible oceanic flux. Being a noble, poorly-soluble gas that does not accumulate in the atmosphere, it is an ideal tracer of recent (<2-3 weeks) air mass contact with ice-free terrestrial regions. In conjunction with air mass back trajectory analysis, radon is thus a useful tool with which to perform fetch analyses for observed pollution events. Since radon’s half-life is much greater than the turbulent timescale in the atmospheric boundary layer (~1 hour), it can be considered a conservative tracer in such situations. Consequently, radon profiles or gradient measurements in the lower atmosphere also provide valuable insight into vertical mixing processes under a range of atmospheric conditions. This presentation will provide an overview of ANSTO’s radon measurement capabilities (including: standalone detectors, tall-tower gradient measurements, aircraft profile measurements and flux chambers), with recent examples of their recent application. Radon’s physical characteristics also make it ideal for the evaluation of transport and mixing schemes of weather, climate or chemical models. This presentation will also showcase a radon flux map of Australia, developed at ANSTO to improve the radon source function employed in regional models.
Assessing the impact of atmospheric stability on locally and remotely sourced aerosols at Richmond, Australia, using Radon-222
(Elsevier, 2015-12-13) Crawford, J; Chambers, SD; Cohen, DD; Williams, AG; Griffiths, AD; Stelcer, E
A flexible radon-based scheme for the classification of nocturnal stability regimes was used for the interpretation of daily-integrated PM2.5 aerosol observations collected at Richmond, Australia, between 2007 and 2011. Source fingerprint concentrations for the dominant locally and remotely sourced aerosols were analysed by nocturnal radon stability category to characterise the influences of day-to-day changes in daily integrated atmospheric mixing. The fingerprints analysed included: smoke, vehicle exhaust, secondary sulfate and aged industrial sulfur. The largest and most consistent stability influences were observed on the locally sourced pollutants. Based on a 5-year composite, daily integrated concentrations of smoke were almost a factor of 7 higher when nocturnal conditions were classed as “stable” than when they were “near neutral”. For vehicle emissions a factor of 4 was seen. However, when the winter months were considered in isolation, it was found that these factors increased to 11.5 (smoke) and 5.5 (vehicle emissions) for daily average concentrations. The changes in concentration of the remotely sourced pollutants with atmospheric stability were comparatively small and less consistent, probably as a result of the nocturnal inversion frequently isolating near-surface observations from non-local sources at night. A similar classification was performed using the commonly-adopted Pasquill–Gifford (PG) stability typing technique based on meteorological parameters. While concentrations of fingerprints associated with locally-sourced pollutants were also shown to be positively correlated with atmospheric stability using the PG classification, this technique was found to underestimate peak pollutant concentrations under stable atmospheric conditions by almost a factor of 2. © 2015, Elsevier Ltd.
Atmospheric carbondisulfide and dimethylsulfide measurements at Cape Grim Australia, marine, terrestrial and anthropogenic contributions
(Bureau of Meteorology and CSIRO Marine and Atmospheric Research, 2013-11-01) Ivey, JP; Swan, HB; Williams, AG; Krummel, PB; Hammond, AP; Steele, PL
Atmospheric stability effects on potential radiological releases at a nuclear research facility in Romania: characterising the atmospheric mixing state
(Elsevier, 2016-04-01) Chambers, SD; Galeriu, D; Williams, AG; Melintescu, A; Griffiths, AD; Crawford, J; Dyer, LL; Duma, M; Zorila, B
A radon-based nocturnal stability classification scheme is developed for a flat inland site near Bucharest, Romania, characterised by significant local surface roughness heterogeneity, and compared with traditional meteorologically-based techniques. Eight months of hourly meteorological and atmospheric radon observations from a 60 m tower at the IFIN-HH nuclear research facility are analysed. Heterogeneous surface roughness conditions in the 1 km radius exclusion zone around the site hinder accurate characterisation of nocturnal atmospheric mixing conditions using conventional meteorological techniques, so a radon-based scheme is trialled. When the nocturnal boundary layer is very stable, the Pasquill–Gifford “radiation” scheme overestimates the atmosphere's capacity to dilute pollutants with near-surface sources (such as tritiated water vapour) by 20% compared to the radon-based scheme. Under these conditions, near-surface wind speeds drop well below 1 m s−1 and nocturnal mixing depths vary from ∼25 m to less than 10 m above ground level (a.g.l.). Combining nocturnal radon with daytime ceilometer data, we were able to reconstruct the full diurnal cycle of mixing depths. Average daytime mixing depths at this flat inland site range from 1200 to 1800 m a.g.l. in summer, and 500–900 m a.g.l. in winter. Using tower observations to constrain the nocturnal radon-derived effective mixing depth, we were able to estimate the seasonal range in the Bucharest regional radon flux as: 12 mBq m−2 s−1 in winter to 14 mBq m−2 s−1 in summer. © 2016, Elsevier Ltd.
Atmospheric transport and chemistry of trace gases in LMDz5B
(Copernicus Publications, 2015-02-03) Locatelli, R; Bousquet, P; Hourdin, F; Saunois, M; Cozic, A; Couvreux, F; Grandpeix, JY; Lefebvre, MP; Rio, C; Bergamaschi, P; Chambers, SD; Karstens, U; Kazan, V; van der Laan, S; Meijer, HAJ; Moncrieff, J; Ramonet, M; Scheeren, HA; Schlosser, C; Schmidt, M; Vermeulen, AT; Williams, AG
Representation of atmospheric transport is a major source of error in the estimation of greenhouse gas sources and sinks by inverse modelling. Here we assess the impact on trace gas mole fractions of the new physical parameterizations recently implemented in the atmospheric global climate model LMDz to improve vertical diffusion, mesoscale mixing by thermal plumes in the planetary boundary layer (PBL), and deep convection in the troposphere. At the same time, the horizontal and vertical resolution of the model used in the inverse system has been increased. The aim of this paper is to evaluate the impact of these developments on the representation of trace gas transport and chemistry, and to anticipate the implications for inversions of greenhouse gas emissions using such an updated model. © Author(s, 2015.
Background level of atmospheric radon-222 concentrations at Gosan Station, Jeju Island, Korea in 2011
(Korea Science, 2014-04-20) Kim, WH; Ko, HJ; Hu, CG; Lee, HY; Lee, CK; Chambers, SD; Williams, AG; Kang, CH
Real-time monitoring of hourly atmospheric radon (Rn-222) concentration was performed throughout 2011 at Gosan station, Jeju Island, one of the least polluted regions in Korea, in order to characterize the background levels, and temporal variations on diurnal to seasonal time-scales. The annual mean radon concentration for 2011 was mBq , and the seasonal cycle was characterized by a broad winter maximum, and narrow summer minimum. Mean monthly radon concentrations, in descending order of magnitude, were Oct > Sep > Feb > Nov > Jan > Dec > Mar > Aug > Apr > Jun > May > Jul. The maximum monthly mean value (3595 mBq , October), exceeded the minimum value (1243 mBq , July), by almost a factor of three. Diurnal composite hourly concentrations increased throughout the night to reach their maximum (2956 mBq ) at around 7 a.m., after which they decreased to their minimum value (2259 mBq ) at around 3 p.m. Back trajectory analyses indicated that the highest radon events typically exhibited long-term continental fetch over Asia before arriving at Jeju. In contrast, low radon events were generally correlated with air mass fetch over the North Pacific Ocean. Radon concentrations typical of predominantly continental, and predominantly oceanic fetch, differed by a factor of 3.8. (C) KISTI. All Rights Reserved.
Baseline characterisation of source contributions to daily-integrated PM2.5 observations at Cape Grim using Radon-222
(Elsevier, 2018-08-20) Crawford, J; Chambers, SD; Cohen, DD; Williams, AG; Atanacio, AJ
We discuss 15 years (2000–2015) of daily-integrated PM2.5 samples from the Cape Grim Station. Ion beam analysis and positive matrix factorisation are used to identify six source-type fingerprints: fresh sea salt (57%); secondary sulfate (14%); smoke (13%); aged sea salt (12%); soil dust (2.4%); and industrial metals (1.5%). An existing hourly radon-only baseline selection technique is modified for use with the daily-integrated observations. Results were not significantly different for days on which >20 hours were below the baseline radon threshold compared with days when all 24 hours satisfied the baseline criteria. This relaxed daily baseline criteria increased the number of samples for analysis by almost a factor of two. Two radon baseline thresholds were tested: historic (100 mBq m−3), and revised (50 mBq m−3). Median aerosol concentrations were similar for both radon thresholds, but maximum values were higher for the 100 mBq m−3 threshold. Back trajectories indicated more interaction with southern Australia and the Antarctic coastline for air masses selected with the 100 mBq m−3 threshold. Radon-only baseline selection using the 50 mBq m−3 threshold was more selective of minimal terrestrial influence than a similar recent study using wind direction and back trajectories. The ratio of concentrations between terrestrial and baseline days for the primary sources soil, smoke and industrial metals was 3.4, 2.6, and 5.5, respectively. Seasonal cycles of soil dust had a summer maximum and winter minimum. Seasonal cycles of smoke were of similar amplitude for terrestrial and baseline events, but of completely different shape: peaking in autumn and spring for terrestrial events, compared to summer for baseline conditions. Seasonal cycles of industrial metals had a summer maximum and winter minimum. A significant fraction of the Cape Grim baseline smoke and industrial metal contributions appeared to be derived from long-term transport (>3 weeks since last terrestrial influence). Crown Copyright © 2018 Published by Elsevier Ltd.
Benchmarks for chemical transport models based on radon-derived stability assessment of urban air pollution
(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-09) Chambers, SD; Williams, AG
Not provided to the ANSTO Library.
A bright future for accelerator science at ANSTO
(Australian Institute of Nuclear Science and Engineering (AINSE), 2009-11-25) Hotchkis, MAC; Child, DP; Cohen, DD; Dodson, JR; Fink, D; Garton, D; Hua, Q; Ionescu, M; Jacobsen, GE; Levchenko, VA; Mifsud, C; Siegele, R; Smith, AM; Williams, AG; Winkler, S
In the May 2009 budget, the Federal Government announced funding of $25m to ANSTO through the Education Investment Fund, to build state-of-the-art applied accelerator science facilities, by upgrading and replacing existing facilities and laboratories at ANSTO. Currently, ANSTO's researchers, jointly with researchers from all 37 Australian universities, plus other agencies such as CSIRO, government departments and local government bodies, and overseas collaborators and customers, use ANSTO's accelerator facilities for analysis of a wide range of materials, predominantly by Accelerator Mass Spectrometry (AMS) and Ion Beam Analysis (IBA). There are >100 external users of those facilities every year. © 2009 AINSE
Bulk mixing and decoupling of the nocturnal boundary layer characterised using a ubiquitous natural tracer
(Springer, 2013-12-01) Williams, AG; Chambers, SD; Griffiths, AD
Vertical mixing of the nocturnal stable boundary layer (SBL) over a complex land surface is investigated for a range of stabilities, using a decoupling index () based on the 2-50 m bulk gradient of the ubiquitous natural trace gas radon-222. The relationship between and the bulk Richardson number () exhibits three broad regions: (1) a well-mixed region () in weakly stable conditions (); (2) a steeply increasing region () for "transitional" stabilities (); and (3) a decoupled region (-1.0) in very stable conditions (). exhibits a large variability within individual bins, however, due to a range of competing processes influencing bulk mixing under different conditions. To explore these processes in - space, we perform a bivariate analysis of the bulk thermodynamic gradients, various indicators of external influences, and key turbulence quantities at 10 and 50 m. Strong and consistent patterns are found, and five distinct regions in - space are identified and associated with archetypal stable boundary-layer regimes. Results demonstrate that the introduction of a scalar decoupling index yields valuable information about turbulent mixing in the SBL that cannot be gained directly from a single bulk thermodynamic stability parameter. A significant part of the high variability observed in turbulence statistics during very stable conditions is attributable to changes in the degree of decoupling of the SBL from the residual layer above. When examined in - space, it is seen that very different turbulence regimes can occur for the same value of , depending on the particular combination of values for the bulk temperature gradient and wind shear, together with external factors. Extremely low turbulent variances and fluxes are found at 50 m height when and (fully decoupled). These "quiescent" cases tend to occur when geostrophic forcing is very weak and subsidence is present, but are not associated with the largest bulk temperature gradients. Humidity and net radiation data indicate the presence of low cloud, patchy fog or dew, any of which may aid decoupling in these cases by preventing temperature gradients from increasing sufficiently to favour gravity wave activity. The largest temperature gradients in our dataset are actually associated with smaller values of the decoupling index (), indicating the presence of mixing. Strong evidence is seen from enhanced turbulence levels, fluxes and submeso activity at 50 m, as well as high temperature variances and heat flux intermittencies at 10 m, suggesting this region of the - distribution can be identified as a top-down mixing regime. This may indicate an important role for gravity waves and other wave-like phenomena in providing the energy required for sporadic mixing at this complex terrain site. © 2013, Springer.
The Centre for Accelerator Science at ANSTO
(International Atomic Energy Agency, 2014-01-14) Hotchkis, MAC; Child, DP; Cohen, DD; Dodson, JR; Fink, D; Fujioka, T; Garton, D; Hua, Q; Ionescu, M; Jacobsen, GE; Levchenko, VA; Mifsud, C; Pastuovic, Z; Siegele, R; Smith, AM; Wilcken, KM; Williams, AG
In 2009, the Federal government provided funding of $25m to ANSTO through the Education Investment Fund, to build state-of-the-art applied accelerator science facilities, with the primary aim of providing world-leading accelerator mass spectrometry (AMS) and ion beam analysis (IBA) facilities. New buildings are now under construction and Building plans are now well advanced, and two new accelerators are on order with National Electrostatics Corporation, USA. The 1MV AMS accelerator system is designed with the capability to perform high efficiency, high precision AMS analysis across the full mass range. Large beam-optical acceptance will ensure high quality and high throughput radiocarbon measurements. High mass resolution analyzers, at low and high energy, coupled to a novel fast isotope switching system, will enable high quality analysis of actinide radioisotopes. The 6MV tandem accelerator will be instrumented with a wide range of AMS, IBA and ion irradiation facilities. The three ion sources include hydrogen and helium sources, and a MCSNICS sputter source for solid materials. The AMS facility has end stations for (i) a gasabsorber detector for 10Be analysis, (ii) a time-of-flight detector, (iii) a gas-filled magnet and(iv) a general use ionization detector suited to 36Cl and other analyses. Initially, there will be four IBA beamlines, including a new ion beam microprobe currently on order with Oxford Microbeams. The other beamlines will include an on-line ion implanter, nuclear reaction analysis and elastic recoil detection analysis facilities. The beam hall layout allows for future expansion, including the possibility of porting the beam to the existing ANTARES beam hall for simultaneous irradiation experiments.Two buildings are currently under construction, one for the new accelerators and the other for new chemistry laboratories for AMS and mass spectrometry facilities. The AMS chemistry labs are planned in two stages, with the new radiocarbon labs to come in the second phase of work.
Characterisation of mixing processes in the lower atmosphere using Rn-222 and climate-sensitive gases
(Australian Nuclear Science and Technology Organisation, 2007-08) Schelander, P; Griffiths, AD; Williams, AG; Chambers, SD; Zahorowski, W
Characterising diurnal & synoptic timescale changes in urban air quality using Radon-222
(Europenan Geosciences Union, 2020-05-01) Chambers, SD; Kikaj, D; Podstawczyńska, A; Williams, AG; Crawford, J; Griffiths, AD
Urban air quality is strongly influenced by the atmosphere’s ability to disperse primary emissions and opportunities for secondary pollution formation. In mid- to high-latitude regions that experience enduring winter snow cover or soil freezing, regional subsidence and stagnation associated with persistent anti-cyclonic conditions such as the “Siberian High” can lead to “cold pool” or “persistent inversion” events. These events can result in life-threatening pollution episodes that last for weeks. While often associated with complex topography [1,2], persistent inversion events can also influence the air quality of urban centres in flat, inland regions [3]. This presentation will describe a recently-developed radon-based technique for identifying and characterising synoptic-timescale persistent inversion events, which is proving to be a simple and economical alternative to contemporary meteorological approaches that require regular sonde profiles [1]. Furthermore, key assumptions of the radon-based technique to characterise diurnaltimescale changes in the atmospheric mixing state described by Chambers et al. [4] are violated during persistent inversion conditions. Here we demonstrate how atmospheric class-typing, through successive application of radon-based techniques for identifying synoptic- and diurnaltimescale changes in the atmospheric mixing state, improves understanding of atmospheric controls on urban air quality in non-summer months across the full diurnal cycle. This knowledge translates directly to statistically-robust techniques for assessing public exposure to pollution, and for evaluating the efficacy of pollution mitigation measures. Lastly, we show how atmospheric class-typing can be used to enhance the evaluation of chemical transport models. © Author(s) 2020
Characterising terrestrial influences on Antarctic air masses using Radon-222 measurements at King George Island
(European Geosciences Union, 2014-09-18) Chambers, SD; Hong, SB; Williams, AG; Crawford, J; Griffiths, AD; Park, SJ
We report on one year of high-precision direct hourly radon observations at King Sejong Station (King George Island) beginning in February 2013. Findings are compared with historic and ongoing radon measurements from other Antarctic sites. Monthly median concentrations reduced from 72 mBq m−3 in late-summer to 44 mBq m−3 in late winter and early spring. Monthly 10th percentiles, ranging from 29 to 49 mBq m−3, were typical of oceanic baseline values. Diurnal cycles were rarely evident and local influences were minor, consistent with regional radon flux estimates one tenth of the global average for ice-free land. The predominant fetch region for terrestrially influenced air masses was South America (47–53° S), with minor influences also attributed to aged Australian air masses and local sources. Plume dilution factors of 2.8–4.0 were estimated for the most terrestrially influenced (South American) air masses, and a seasonal cycle in terrestrial influence on tropospheric air descending at the pole was identified and characterised. © Author(s) 2014
The citical role of observations in developing numerical representations of ice nucleating particles for southern ocean mixed phased clouds
(American Meterological Society, 2020-01-31) McCluskey, CS; DeMott, PJ; Hill, TCJ; Kreidenweis, SM; Ovadnevaite, J; Rinaldi, M; Atkinson, J; Belosi, F; Ceburnis, D; Marullo, S; Lohmann, U; Kanji, ZA; O'Dowd, C; Humphries, R; Rauker, AM; Moreau, S; Strutton, PG; Chambers, SD; Williams, AG; McRobert, I; Ward, J; Keywood, MD; Harnwell, J; Pronsonby, W; Loh, Z; Krummell, P; Protat, A; Gettelman, A; Bardeen, CG; Twohy, CH; MA, PL; Burrows, SM
The abundance of supercooled liquid clouds over the remote Southern Ocean (SO) region challenges the aerosol-cloud microphysical interactions that are currently represented in global climate models. In particular, most global climate models simulate SO clouds that are over-glaciated compared to satellite observations, leading to large radiative biases. Primary ice formation initiated by atmospheric ice nucleating particles (INPs) is a critical process in cloud glaciation and is augmented by additional processes, such as secondary ice production. Due to extremely high winds and large distances from land, the INP sources are likely dominated by locally produced sea spray aerosol (SSA) and long-range transported terrestrial aerosol (e.g., dust and pollution). However, a dearth of aerosol and INP observations in the remote SO have limited our ability to advance numerical representations of freezing processes until recent years. In this study, we demonstrate ways in which recent INP observations have improved our understanding of SO INP populations and how modeling studies can aid in developing hypotheses that can be tested by future observational studies. Coastal and ship observations were used to 1) characterize remote INP populations and 2) develop and test numerical representations of INPs relevant for remote oceanic regions. These observations revealed that INPs associated with SSA are up to a factor of 1000 less ice nucleation active compared to mineral dust. Extremely low INP concentrations observed over the SO support the prevalence of supercooled liquid clouds known to dominate the SO region. In a series of nudged simulations with the Community Earth System Model, Versions 1 and 2, we demonstrated that observed INP number concentrations in the marine boundary layer are successfully predicted using an approach that considers only SSA and dust INPs. This predictive tool was further used to estimate INP populations at higher altitudes over the SO study region, revealing that while SSA dominates the INP population below 3-5 km, mineral dust INPs may be critical for INP populations present above 5 km. Finally, an evaluation of model-estimated INPs present at higher altitudes using recent airborne measurements of INPs from the 2018 Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study will be presented.

Browsing by Author "Williams, AG"

Results Per Page

Sort Options