Title Cold oceans enhance terrestrial new- particle formation in near-coastal forests
Author Suni, T.; Sogacheva, L.; Lauros, J.; Hakola, H.; Back, J.; Kurten, T.; Cleugh, H.; van Gorsel, E.; Briggs, P.; Sevanto, S.; Kulmala, M.
Author Affil Suni, T., University of Helsinki, Department of Physics, Helsinki, Finland. Other: Finnish Meteorological Institute, Finland; University of Helsinki, Finland; CSIRO Marine and Atmospheric Research, Australia
Source Atmospheric Chemistry and Physics, 9(22), p.8639-8650. Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2009
Notes In English. Published in Atmospheric Chemistry and Physics Discussions: 11 June 2009, http://www.atmos-chem-phys- discuss.net/9/13093/2009/acpd-9-13093-2009.ht ml; accessed in May, 2011. 34 refs. GeoRef Acc. No: 310115. CRREL Acc. No: 65006738
Index Terms aerosols; atmospheric circulation; precipitation (meteorology); evaporation; humidity; photosynthesis; trees (plants); vegetation; Arctic Ocean; Australia--New South Wales; Southern Ocean; atmospheric precipitation; Australasia; Australia; biogenic processes; climate forcing; East Australian Current; environmental analysis; forests; grasslands; humid environment; New South Wales Australia; organic compounds; photochemistry; seasonal variations; solar forcing; terrestrial environment; trees; uncertainty; volatile organic compounds; volatiles; winds; world ocean
Abstract 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.
URL http://www.atmos-chem-phys.net/9/8639/2009/acp-9-8639-2009.pdf
Publication Type journal article
Record ID 91456