Naturally driven variability in the global secondary organic aerosol over a decade

[摘要] In order to investigate the variability of the secondary organic aerosol(SOA) distributions and budget and provide a measure for the robustness ofthe conclusions on human induced changes of SOA, a global 3-dimensionalchemistry transport model describing both the gas and the particulate phasechemistry of the troposphere has been applied. The response of the globalbudget of SOA to temperature and moisture changes as well as to biogenicemission changes over a decade (1984-1993) has been evaluated. Theconsidered emissions of biogenic non-methane volatile organic compounds(VOC) are driven by temperature, light and vegetation. They vary between 756and 810 Tg Cy^-1 and are therefore about 5.5 times higher than theanthropogenic VOC emissions. All secondary aerosols (sulphuric, nitrates andorganics) are computed on-line together with the aerosol associated water.Over the studied decade, the computed natural variations (8%) in thechemical SOA production from biogenic VOC oxidation equal the chemical SOAproduction from anthropogenic VOC oxidation. Maximum values are calculatedfor 1990 (warmer and drier) and minimum values for 1986 (colder and wetter).The SOA computed variability results from a 7% increase in biogenic VOCemissions from 1986 to 1990 combined with 8.5% and 6% increases in thewet and dry deposition of SOA and leads to about 11.5% increase in theSOA burden of biogenic origin. The present study also demonstrates theimportance of the hydrological cycle in determining the built up and fate ofSOA in the atmosphere. It also reveals the existence of significant positiveand negative feedback mechanisms in the atmosphere responsible for the nonlinear relationship between emissions of biogenic VOC and SOA burden.

[学科分类] 大气科学