ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-9-8639-2009 Cold oceans enhance terrestrial new-particle formation in near-coastal forests Suni T. 1 Sogacheva L. 1 Lauros J. 1 Hakola H. 2 Bäck J. 3 Kurtén T. 1 Cleugh H. 4 van Gorsel E. 4 Briggs P. 4 Sevanto S. 1 Kulmala M. 1 Department of Physics, University of Helsinki, P.O. Box 48, 00014 Helsinki, Finland Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland Department of Forest Ecology, P.O. Box 27, 00014 University of Helsinki, Finland CSIRO Marine and Atmospheric Research, GPO Box 1666, Canberra ACT 2601, Australia 16 11 2009 9 22 8639 8650 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/9/8639/2009/acp-9-8639-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/9/8639/2009/acp-9-8639-2009.pdf

The world's forests produce atmospheric aerosol by emitting volatile organic compounds (VOC) which, after being oxidized in the atmosphere, readily condense on the omnipresent nanometer-sized nuclei and grow them to climatically relevant sizes. The cooling effect of aerosols is the greatest uncertainty in current climate models and estimates of radiative forcing. Therefore, identifying the environmental factors influencing the biogenic formation of aerosols is crucial. In this paper, we connected biogenic aerosol formation events observed in a Eucalypt forest in South-East Australia during July 2005–December 2006 to air mass history using 96-h back trajectories. Formation of new particles was most frequent in the dry westerly and south-westerly air masses. According to NDVI (Normalized Difference Vegetation Index) measurements, photosynthesis was not significantly higher in this direction compared to the north-east direction. It is unlikely, therefore, that differences in photosynthesis-derived organic precursor emissions would have been significant enough to lead to the clear difference in NPF frequency between these two directions. Instead, the high evaporation rates above the Pacific Ocean resulted in humid winds from the north-east that effectively suppressed new-particle formation in the forest hundreds of kilometers inland. No other factor varied as significantly in tune with new-particle formation as humidity and we concluded that, in addition to local meteorological factors in the forest, the magnitude of evaporation from oceans hundreds of kilometers upwind can effectively suppress or enhance new-particle formation. Our findings indicate that, unlike warm waters, the cold polar oceans provide excellent clean and dry background air that enhances aerosol formation above near-coastal forests in Fennoscandia and South-East Australia.

 References Anttila, T. and V.-M. Kerminen: Modeling study on aerosol dynamical processes regulating new particle and CCN formation at clean continental areas, Geophys. Res. Lett., 35, L07813, doi:10.1029/2008GL033371, 2008. Atkinson, R.: Atmospheric chemistry of VOCs and NO<sub>x</sub>, Atmosph. Env., 34, 2063–2101, 2000. Baker, M. B. and Peter, T.: Small-scale cloud processes and climate, Nature, 451, 299–300, 2008. Bonn, B. and Moortgat, K.: Sesquiterpene ozonolysis: Origin of atmospheric new particle formation from biogenic hydrocarbons, Geophys. Res. Lett., 30, 1585, doi:10.1029/2003GL017000, 2003. Bonn, B., Schuster, G., and Moortgat, G. K.: Influence of Water Vapor on the Process of New Particle Formation during Monoterpene Ozonolysis, J. Phys. Chem. A, 106, 2869–2881, 2002. Buzorius, G., Rannik, Ü., Nilsson, D., and Kulmala, M.: Vertical fluxes and micrometeorology during aerosol particle formation events, Tellus B 53, 394–405, 2001. Calogirou, A., Richter Larsen, B., Brussol, C., Duane, M., and Kotzias, D.: Decomposition of terpenes by ozone during sampling on Tenax., Anal. Chem. 68, 1499–1506, 1996. Calogirou, A., Richter Larsen, B., and Kotzias, D.: Gas-phase terpene oxidation products: a review, Atmosph. Env., 33, 1423–1439, 1999. Carrasco, N., Doussin, J. F., O'Connor, M., Wenger, J. C., Picquet-Varrault, B., Durand-Jolibois, R., and Carlier, P : Simulation Chamber Studies of the Atmospheric Oxidation of 2-Methyl-3-Buten-2-ol: Reaction with Hydroxyl Radicals and Ozone Under a Variety of Conditions, J. Atmos. Chem. 56, 33–55, 2007. Clement, A. C., Burgman, R., and Norris, J. R.: Obser vational and model evidence for positive low-level cloud feedback. Science, 325, 460–464, doi:10.1126/science.1171255, 2009. Draxler, R. R. and Hess, G. D.: Description of the HYSPLIT_4 Modeling System, NOAA Technical Memorandum ERL ARL-224, 2004. Hakola, H., Tarvainen, V., Bäck, J., Rinne, J., Ranta, H., Bonn, B., and Kulmala, M.: Seasonal variation of mono- and sesquiterpene emission rates of Scots pine, Biogeosciences, SRef-ID: 1726-4189/bg/2006-3-93, 93–101, 2006. Hakola, H., Tarvainen, V., Laurila, T., Hiltunen, V., Hellén, H., and Keronen, P.: Seasonal variation of VOC concentrations above a boreal coniferous forest, Atmos. Env. 37, 1623–1634, 2003. Helmig, D.: Ozone Removal Techniques in the Sampling of Atmospheric Volatile. Organic Trace Gases, Atmos. Environ. 31, 3635–3651, 1997. Hirsikko, A., Bergman, T., Laakso, L., Dal Maso, M., Riipinen, I., Hõrrak, U., and Kulmala, M.: Identification and classification of the formation of intermediate ions measured in boreal forest, Atmos. Chem. Phys., 7, 201–210, 2007. Hyvönen, S., Junninen, H., Laakso, L., Dal Maso, M., Grönholm, T., Bonn, B., Keronen, P., Aalto, P., Hiltunen, V., Pohja, T., Launiainen, S., Hari, P., Mannila, H., and Kulmala, M.: A look at aerosol formation using data mining techniques, Atmos. Chem. Phys. 5, 3345–3356, 2005. Jonsson, Å.M., Hallquist, M., and Ljungström, E.: Impact of Humidity on the Ozone Initiated Oxidation of Limonene, $\Delta^3$-Carene, and $\alpha $-Pinene, Environ. Sci. Technol. 40, 188–194, 2006. Jonsson, Å.M., Hallquist, M., and Ljungström, E.: Influence of OH Scavenger on the Water Effect on Secondary Organic Aerosol Formation from Ozonolysis of Limonene, $\Delta^3$-Carene, and $\alpha $-Pinene, Environ. Sci Technol. 42, 5938–5944, 2008a. Jonsson, Å. M., Hallquist, M., and Ljungström, E.: The effect of temperature and water on secondary organic aerosol formation from ozonolysis of limonene, $\Delta ^3$-carene and $\alpha $-pinene, Atmos. Chem. Phys., 8, 6541–6549, 2008b. Kerminen, V.-M., Lihavainen, H., Komppula, M., Viisanen, Y., and Kulmala, M.: Direct observational evidence linking atmospheric aerosol formation and cloud droplet activation, Geophys. Res. Lett. 32, L14803, doi:10.1029/2005GL023130, 2005. Kesselmeier, J. and Staudt, M.: Biogenic Volatile Organic Compounds (VOC): An Overview on Emission, Physiology and Ecology, J. Atmos. Chem. 33, 23–88, 1999. Kulmala, M., Lehtinen, K. E. J., and Laaksonen, A.: Cluster activation theory as an explanation of the linear dependence between formation rate of 3nm particles and sulphuric acid concentration, Atmos. Chem. Phys. 6, 787–793, 2006. Kulmala, M., Vehkamäki, H., Petäjä, T., Dal Maso, M., Lauri, A., Kerminen, V.-M., Birmili, W., and McMurry, P. H.: Formation and growth rates of ultrafine atmospheric particles: a review of observations, J. Aerosol Sci., 35, 143–176, 2004. Kurtén, T., Kulmala, M., Dal Maso, M., Suni, T., Reissell, A., Vehkamäki, H., Hari, P., Laaksonen, A., Viisanen, Y., and Vesala, T.: Estimation of different forest-related contributions to the radiative balance using observation in southern Finland, Boreal Env. Res., 8, 275–285, 2003. Laaksonen, A., Hamed, A., Joutsensaari, J., Hiltunen, L., Cavalli, F., Junkermann, W., Asmi, A., Fuzzi, S., and Facchini, M. C.: Cloud condensation nucleus production from nucleation events at a highly polluted region, Geophys. Res. Lett. 32, L06812, doi:10.1029/2004GL022092, 2005. Leuning, R., Cleugh, H. A., Zegelin, S., and Hughes, D.: Carbon and water cycles in two contrasting Australian ecosystems: Wet/Dry savannas and cool temperate Eucalyptus forest, Agr. For. Meteor. 129, 151–173, 2005. Modini, R. L., Ristovski, Z. D., Johnson, G. R., He, C., Surawski, N., Morawska, L., Suni, T., and Kulmala, M.: New particle formation and growth at a remote, sub-tropical coastal location, Atmos. Chem. Phys., 9, 7607–7621, 2009 Nilsson, E. D., Paatero, J., and Boy, M.: Effects of air masses and synoptic weather on aerosol formation in the continental boundary layer, Tellus B 53, 462–478, 2001. Ristovski, Z D., ~Suni, T., Kulmala, M., Boy, M., Meyer, N K., Duplissy, J., Turnipseed, A , Morawska, L., and Baltensperger, U.: The role of sulphates and organic vapours in new particle formation in a eucalypt forest, Atmos. Chem. Phys. Discuss.,~9,~17793–17815,~2009. Sogacheva, L., Dal Maso, M., Kerminen, V.-M., and Kulmala, M.: Probability of nucleation events and aerosol particle concentration in different air mass types arriving at Hyytiälä, southern Finland, based on back trajectories analysis, Boreal Environ. Res., 10, 479–491, 2005. Spracklen, D. V., Carslaw, K. S., Kulmala, M., Kerminen, V.-M., Mann, G. W., and Sihto, S.-L.: The contribution of boundary layer nucleation events to total particle concentrations on regional and global scales, Atmos. Chem. Phys., 6, 5631–5648, 2006. Suni, T., Kulmala, M., Hirsikko, A., Bergman, T., Laakso, L., Aalto, P. P., Leuning, R., Cleugh, H., Zegelin, S., Hughes, D., van Gorsel, E., Kitchen, M., Vana, M., Hõrrak, U., Mirme, S., Mirme, A., Sevanto, S., Twining, J., and Tadros, C.: Formation and characteristics of ions and charged aerosol particles in a native Australian Eucalypt forest, Atmos. Chem. Phys., 8, 129–139, 2008. Tunved, P., Hansson, H.-C., Kerminen, V.-M., Ström, J., Dal Maso, M., Lihavainen, H,. Viisanen, Y., Aalto, P. P., Komppula, M., and Kulmala, M.: High Natural Aerosol Loading over Boreal Forests, Science, 312, 261–263, doi:10.1126/science.1123052, 2006. Vartiainen, E., Kulmala, M., Ruuskanen, T. M., Taipale, R., Rinne, J., and Vehkamäki, H.: Formation and growth of indoor air aerosol particles as a result of d-limonene oxidation, Atmos. Env. 40, 7882–7892, doi:10.1016/j.atmosenv.2006.07.022, 2006. Wang, J., Lee, Y.-N., Daum, P. H., Jayne, J., and Alexander, M. L.: Effects of aerosol organics on cloud condensation nucleus (CCN) concentration and first indirect aerosol effect, Atmos. Chem. Phys. 8, 6325–6339, 2008