ACP Atmospheric Chemistry and Physics ACP Atmos. Chem. Phys. 1680-7324 Copernicus Publications Göttingen, Germany 10.5194/acp-9-1943-2009 Characterisation of episodic aerosol types over the Australian continent Qin Y. 1 Mitchell R. M. 1 CSIRO Marine and Atmospheric Research, Centre for Australian Weather and Climate Research, a partnership between CSIRO and the Australian Bureau of Meteorology, Canberra, ACT, Australia 19 03 2009 9 6 1943 1956 Copyright: © 2009 Y. Qin 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/articles/9/1943/2009/acp-9-1943-2009.html The full text article is available as a PDF file from https://acp.copernicus.org/articles/9/1943/2009/acp-9-1943-2009.pdf

Classification of Australian continental aerosol types resulting from episodes of enhanced source activity, such as smoke plumes and dust outbreaks, is carried out via cluster analysis of optical properties obtained from inversion of sky radiance distributions at Australian aerosol ground stations using data obtained over the last decade. The cluster analysis distinguishes four significant classes, which are identified on the basis of their optical properties and provenance as determined by satellite imagery and back-trajectory analysis. The four classes are identified respectively as aged smoke, fresh smoke, coarse dust and a super-absorptive aerosol. While the first three classes show similarities with comparable aerosol types identified elsewhere, the super-absorptive aerosol has no obvious foreign prototype. The class identified as coarse dust shows a prominent depression in single scattering albedo in the blue spectral region due to absorption by hematite, which is shown to be more abundant in central Australian dust relative to the "dust belt"of the Northern Hemisphere. The super-absorptive class is distinctive in view of its very low single scattering albedo (~0.7 at 500 nm) and variable enhanced absorption at 440 nm. The strong absorption by this aerosol requires a high black carbon content while the enhanced blue-band absorption may derive from organic compounds emitted during the burning of specific vegetation types. This aerosol exerts a positive radiative forcing at the top of atmosphere (TOA), with a large deposition of energy in the atmosphere per unit aerosol optical depth. This contrasts to the other three classes where the TOA forcing is negative. Optical properties of the four types will be used to improve the representation of Australian continental aerosol in climate models, and to enhance the accuracy of satellite-based aerosol retrievals over Australia.

 References Abel, S J., Haywood, J M., Highwood, E J., Li, J., and Buseck, P R.: Evolution of biomass burning aerosol properties from an agricultural fire in southern Africa, Geophys. Res. Lett., 30(15), 1783, https://doi.org/10.1029/2004GL017342, 2003. Armstrong, D.: Natural History of the North East Deserts, ISBN 0 9596627 5 8, Royal Society of South Australia Inc., 1990. Bergstrom, R W., Pilewskie, P., Schmid, B., and Russell, P B.: Estimates of the spectral aerosol single scattering albedo and aerosol radiative effects during SAFARI 2000, J. Geophys. Res., 108(D13), 8474, https://doi.org/10.1029/2002JD002435, 2003. Berk, A., Anderson, G P., Acharya, P K., Chetwynd, J H., Bernstein, L S., Shettle, E P., Matthews, M W., and Adler-Gordon, S M.: MODTRAN4 User's Manual, Tech. rep., Air Force Research Laboratory, Hanscom AFB, MA, USA, 2000. Bicici, E. and Yuret, D.: Locally Scaled Density Based Clustering, Lect. Notes Comput. Sc., 4431, 739–748, 2007. Bullard, J E. and White, K.: Dust production and the release of iron oxides resulting from the aeolian abrasion of natural dune sands, Earth Surf. Proc. Land., 30, 95–106, 2005. Carr, S B., Gras, J L., Hackett, M T., and Keywood, M D.: Aerosol Characterisation in the Northern Territory of Australia during the Dry Season with an Emphasis on Biomass Burning, Tech. rep., Intelligence, Surveillance and Reconnaissance Division Information Sciences Laboratory, Defence Science and Technology Organisation, Australia, DSTO-RR-0298, 2005. Cassar, N., Bender, M L., Barnett, B A., Fan, S., Moxim, W J., Levy II, H., and Tilbrook, B.: The Southern Ocean biological response to aeolian iron deposition, Science, 317, 1067–1070, 2007. Chýlek, P., Srivastava, V., Pinnick, R G., and Wang, R T.: Scattering of electromagnetic waves by composite spherical particles: experiments and effective medium approximations, Appl. Optics, 27, 2396–2404, 1988. Claquin, T., Schulz, M., and Balkanski, Y J.: Modeling the mineralogy of atmospheric dust sources, J. Geophys. Res., 104, 22243–22256, 1999. DEWR: Australia's Native Vegetation: A summary of Australia's Major Vegatation Groups, Tech. rep., Department of the Environment and Water Resources, Australian Government, Canberra, ACT, 42 pp., 2007. Draxler, R R. and Hess, G D.: Description of the HYSPLIT_4 modeling system, Tech. rep., NOAA, Silver Spring, Md., NOAA Tech. Memo. ERL ARL-224, 24 pp., 1997. Dubovik, O. and King, M D.: A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements, J. Geophys. Res., 105, 20673–20696, https://doi.org/10.1029/2000JD900282, 2000. Dubovik, O., Holben, B N., Kaufman, Y J., Yamasoe, M., Smirnov, A., Tanré, D., and Slutsker, I.: Single-scattering albedo of smoke retrieved from the sky radiance and solar transmittance measured from ground, J. Geophys. Res., 103, 31903–31923, 1998. Dubovik, O., Smirnov, A., Holben, B N., King, M D., Kaufman, Y J., Eck, T F., and Slutsker, I.: Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements, J. Geophys. Res., 105, 9791–9806, https://doi.org/10.1029/2000JD900040, 2000. Dubovik, O., Holben, B., Eck, T F., Smirnov, A., Kaufman, Y J., King, M D., Tanré, D., and Slutsker, I.: Variability of absorption and optical properties of key aerosol types observed in worldwide locations, J. Atmos. Sci., 59, 590–608, 2002. Dubovik, O., Sinyuk, A., Lapyonok, T., Holben, B N., Mishchenko, M., Yang, P., Eck, T F., Volten, H., Munoz, O., Veihelmann, B., van~der Zande, W J., Leon, J.-F., Sorokin, M., and Slutsker, I.: Application of spheroid models to account for aerosol particle nonsphericity in remonte sensing of desert dust, J. Geophys. Res., 111(D11), D11208, https://doi.org/10.1029/2005JD006619, 2006. Eck, T F., Holben, B N., Ward, D E., Mukelabai, M M., Dubovik, O., Smirnov, A., Schafer, J S., Hsu, N C., Piketh, S J., Queface, A., Le Roux, J., Swap, R J., and Slutsker, I.: Variability of biomass burning aerosol optical characteristics in southern Africa during the SAFARI 2000 dry season campaign and a comparison of single scattering albedo estimates from radiometric measurements, J. Geophys. Res., 108(D13), 8477, https://doi.org/10.1029/2002JD002321, 2003. Eck, T F., Holben, B N., Reid, J S., Sinyuk, A., Dubovik, O., Smirnov, A., Giles, D., O'Neill, N T., Tsay, S.-C., Ji, Q., Mandoos, A A., Khan, M R., Reid, E A., Schafer, J S., Sorokine, M., Newcomb, W., and Slutsker, I.: Spatial and temporal variability of column-integrated aerosol optical properties in the southern Arabian Gulf and United Arab Emirates in summer, J. Geophys. Res., 113, D01204, https://doi.org/10.1029/2007JD008944, 2008. Evans, L F., King, N K., MacArthur, D A., Packham, D R., and Stephens, E T.: Further studies of the nature of bushfire smoke, Technical Paper~2, Division of Applied Organic Chemistry, CSIRO, 12 pp., 1976. Forster, P., Ramaswamy, V., Artaxo, P., Berntsen, T., Betts, R., Fahey, D., Haywood, J., Lean, J., Lowe, D., Myhre, G., Nganga, J., Prinn, R., Raga, G., Schulz, M., and Dorland, R V.: Changes in Atmospheric Constituents and in Radiative Forcing, in: Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., 2007. Gras, J L., Jensen, J B., Okada, K., Ikegami, M., Zaizen, Y., and Makino, Y.: Some optical properties of smoke aerosol in Indonesia and tropical Australia, Geophys. Res. Lett., 26, 1393–1396, 1999. Grira, N., Crucianu, M., and Boujemaa, N.: Unsupervised and semi-supervised clustering: a brief survey, in A Review of Machine Learning Techniques for Processing Multimedia Content, Report of the MUSCLE European Network of Excellence (6th Framework Program), 12 pp., 2005. Herring, J A. and Hobbs, P V.: Radiatively Driven Dynamics of the Plume from 1991 Kuwait Oil Fires, J. Geophys. Res., 99, 18809–18826, 1994. Hoffer, A., Gelencsér, A., Guyon, P., Kiss, G., Schmid, O., Frank, G. P., Artaxo, P., and Andreae, M. O.: Optical properties of humic-like substances (HULIS) in biomass-burning aerosols, Atmos. Chem. Phys., 6, 3563–3570, 2006. Holben, B N., Eck, T F., Slutsker, I., Tanré, D., Buis, J P., Setzer, A., Vermote, E., Reagan, J A., Kaufman, Y J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET – A federated instrument network and data archive for aerosol characterization, Remote Sens. Environ., 66, 1–16, 1998. Kinne, S., Schulz, M., Textor, C., Guibert, S., Balkanski, Y., Bauer, S. E., Berntsen, T., Berglen, T. F., Boucher, O., Chin, M., Collins, W., Dentener, F., Diehl, T., Easter, R., Feichter, J., Fillmore, D., Ghan, S., Ginoux, P., Gong, S., Grini, A., Hendricks, J., Herzog, M., Horowitz, L., Isaksen, I., Iversen, T., Kirkevåg, A., Kloster, S., Koch, D., Kristjansson, J. E., Krol, M., Lauer, A., Lamarque, J. F., Lesins, G., Liu, X., Lohmann, U., Montanaro, V., Myhre, G., Penner, J., Pitari, G., Reddy, S., Seland, O., Stier, P., Takemura, T., and Tie, X.: An AeroCom initial assessment – optical properties in aerosol component modules of global models, Atmos. Chem. Phys., 6, 1815–1834, 2006. Kirchsetter, T W. and Novakov, T.: Evidence that the spectral dependence of light absorption by aerosols in affected by organic carbon, J. Geophys. Res., 109, D21208, https://doi.org/10.1029/2004JD004999, 2004. Kotsiantis, S B. and Pintelas, P E.: Recent advances in clustering: A brief survey, WSEAS Trans. Info. Sci., 1, 73–81, 2004. Koven, C D. and Fung, I.: Inferring dust composition from wavelength-dependent absorption in Aerosol Robotic Network (AERONET) data, J. Geophys. Res., 111, D14205, https://doi.org/10.1029/2005JD006678, 2006. Krekov, G M.: Models of Atmospheric Aerosols, in Aerosol Effects on Climate, edited by: Jennings, S. G., 9–72, Univ. of Ariz. Press, Tucson, 1992. Levy, R C., Remer, L A., and Dubovik, O.: Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land, J. Geophys. Res., 112, D13210, https://doi.org/10.1029/2006JD007815, 2007. Luhar, A K., Mitchell, R M., Meyer, C. P M., Qin, Y., Campbell, S K., Gras, J L., and Parry, D.: Biomass burning emissions over northern Australia constrained by aerosol measurements: II – model validation, and impacts on air quality and radiative forcing, Atmos. Environ., 42, 1647–1664, 2008. McTainsh, G H., Lynch, A W., and Trews, E K.: Climate controls upon dust storm occurrence in eastern Australia, J. Arid Emviron., 39, 457–466, 1998. Meyer, C. P M., Luhar, A K., and Mitchell, R M.: Biomass burning emissions over northern Australia constrained by aerosol measurements: I – modelling the distribution of hourly emissions, Atmos. Environ., 42, 1629–1646, 2008. Mitchell, R M. and Campbell, S.: The Australian Aerosol Ground Station Network: Status Report and Development of a Radiometric Calibration Facility, Opt. Pur y Apl., 3259–3262, 2004. Mitchell, R M. and Forgan, B W.: Aerosol measurements in the Australian Outback: intercomparison of sun photometers, J. Atmos. Ocean. Tech., 20, 54–66, https://doi.org/10.1175/1520-0426(2003), 2003. Mitchell, R M., O'Brien, D M., and Campbell, S K.: Characteristics and radiative impact of the aerosol generated by the Canberra firestorm of January 2003, J. Geophys. Res., 111(D2), D02204, https://doi.org/10.1029/2005JD006304, 2006. Nousiainen, T. and Vermeulen, K.: Comparison of measured single-scattering matrix of feldspar particles with T-matrix simulations using spheroids, J. Quant. Spectrosc. Ra., 79–80, 1031–1042, 2003. O'Brien, D M. and Mitchell, R M.: Atmospheric heating due to carbonaceous aerosol in northern Australia – confidence limits based on TOMS aerosol index and sun-photometer data, Atmos. Res., 66, 21–41, https://doi.org/10.1016/S0169-8095(02)00173-4, 2003. Omar, A H., Won, J.-G., Winker, D M., Yoon, S.-C., Dubovik, O., and McCormick, M P.: Development of global aerosol models using cluster analysis of Aerosol Robotic Network (AERONET) measurements, J. Geophys. Res., 110, D10S14, https://doi.org/10.1029/2004JD004874, 2005. Reid, J S., Jonsson, H H., Maring, H B., Smirnov, A., Savoie, D L., Cliff, S S., Reid, E A., Livingstone, J M., Meier, M M., Dubovik, O., and Tsay, S.-C.: Comparison of size and morphological measurements of coarse mode dust particles from Africa, J. Geophys. Res., 108(D19), 8593, https://doi.org/10.1029/2002JD002485, 2003. Rotstayn, L D., Forgan, B W., Gabric, A J., Gallbally, I E., Gras, J L., Keywood, M D., Luhar, A K., Mitchell, R M., and Young, S A.: Possible impacts of anthropogenic and natural aerosols on Australian climate and weather: a review, Int. J. Climatol., 29, 461–479, https://doi.org/10.1002/joc.1729, www.interscience.wiley.com, 2009a. Rotstayn, L D., Collier, M., Hendon, H H., Smith, I N., and Syktus, J.: Improved simulation of Australian ENSO-related rainfall variability in a GCM with an interactive aerosol treatment, Int. J. Climatol., submitted, 2009b. Sander, J., Ester, M., Kriegel, H., and Xu, X.: Density-Based Clustering in Spatial Databases: The Algorithm GDBSCAN and its Applications, Data Min. Knowl. Disc., 2, 169–194, 1998. Satheesh, S K. and Ramanathan, V.: Large differences in tropical aerosol forcing at the top of the atmosphere and Earth's surface, Nature, 405, 60–63, https://doi.org/10.1038/35011039, 2000. Sokolik, N. and Toon, O B.: Incorporation of mineralogical composition into models of the radiative properties of mineral aerosol from UV to IR wavelengths, J. Geophys. Res., 104, 9423–9444, 1999. Tanaka, T Y. and Chiba, M.: A numerical study of the contributions of dust source regions to the global dust budget, Global Planet. Change, 52, 88–104, 2006. Vines, R G., Gibson, L., Hatch, A B., King, N K., MacArthur, D A., Packham, D R., and Taylor, R J.: On the nature, properties and behaviour of bushfire smoke, Technical Paper~1, Division of Applied Chemistry, CSIRO, 75–80, 1971. Webb, N P., McGowan, H A., Phinn, S R., and McTainsh, G H.: AUSLEM (AUStralian Land Erodibility Model): A tool for identifying wind erosion hazard in Australia, Geomorphology, 78, 179–200, 2006. Weinzierl, M., Petzold, A., Esselborn, M., Wirth, M., Rasp, K., Kandler, K., Shütz, L., Koepke, P., and Fiebig, M.: Airborne measurements of dust layer properties, particle size distribution and mixing state of Saharan dust during SAMUM 2006, Tellus, 61B, 96–117, https://doi.org/10.111/j.1600-0889.2008.00392.x, 2009.