Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation M. Fiebig1, D. Hirdman2, C. R. Lunder3, J. A. Ogren4, S. Solberg1, A. Stohl1, and R. L. Thompson1 1Department for Atmospheric and Climate Research, Norwegian Institute for Air Research, Kjeller, Norway 2Swedish Meteorological and Hydrological Institute (SMHI), Norrköping, Sweden 3Monitoring and Information Technology Department, Norwegian Institute for Air Research, Kjeller, Norway 4Earth System Research Laboratory/Global Monitoring Division, National Oceanic and Atmospheric Administration, Boulder Colorado, USA
Abstract. This article investigates the annual cycle observed in the Antarctic
baseline aerosol scattering coefficient, total particle number
concentration, and particle number size distribution (PNSD),
as measured at Troll Atmospheric Observatory.
Mie theory shows that the annual cycles in microphysical
and optical aerosol properties have a common cause.
By comparison with observations at other Antarctic stations, it is
shown that the annual cycle is not a local phenomenon, but common to
central Antarctic baseline air masses. Observations of ground-level ozone at Troll as well as backward
plume calculations for the air masses arriving at Troll demonstrate
that the baseline air masses originate from the free
troposphere and lower stratosphere region, and descend over the
central Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters
<100 nm recently formed from the gas-phase despite the absence of
external sources of condensible gases.
The total particle volume in Antarctic baseline
aerosol is linearly correlated with the integral insolation the
aerosol received on its transport pathway, and the
photooxidative production of particle volume is mostly limited by
photooxidative capacity, not availability of aerosol precursor gases.
The photooxidative particle volume formation rate in central Antarctic
baseline air is quantified to 207 ± 4 μm3/(MJ m).
Further research is proposed to investigate the applicability of this
number to other atmospheric reservoirs, and to use the observed
annual cycle in Antarctic baseline aerosol properties as a benchmark
for the representation of natural atmospheric aerosol processes in
Citation: Fiebig, M., Hirdman, D., Lunder, C. R., Ogren, J. A., Solberg, S., Stohl, A., and Thompson, R. L.: Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation, Atmos. Chem. Phys., 14, 3083-3093, doi:10.5194/acp-14-3083-2014, 2014.