Articles | Volume 9, issue 15
Atmos. Chem. Phys., 9, 5461–5474, 2009
Atmos. Chem. Phys., 9, 5461–5474, 2009

  03 Aug 2009

03 Aug 2009

Long term particle size distribution measurements at Mount Waliguan, a high-altitude site in inland China

N. Kivekäs1, J. Sun2, M. Zhan2, V.-M. Kerminen1, A. Hyvärinen1, M. Komppula3, Y. Viisanen1, N. Hong4, Y. Zhang2, M. Kulmala5, X.-C. Zhang2, Deli-Geer4, and H. Lihavainen1 N. Kivekäs et al.
  • 1Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
  • 2Key Laboratory for Atmospheric Chemistry of CMA, Center for Atmosphere Watch and Services, Chinese Academy of Meteorological Sciences, Beijing 100081, China
  • 3Finnish Meteorological Institute P.O. Box 1627, 70211 Kuopio, Finland
  • 4China GAW Baseline Observatory, Qinghai Meteorological Bureau, Xining 810001, China
  • 5University of Helsinki, Dept. Physical Sciences, P.O. Box 64, 00014 Univ. of Helsinki, Finland

Abstract. Particle number size distributions in size range 12–570 nm were measured continuously at Mount Waliguan, a remote mountain-top station in inland China. The station is located at the altitude of 3816 m a.s.l., and some 600–1200 m above the surrounding area. The measurement period lasted from September 2005 to May 2007. The measurements were verified with independent CPC measurements at the same site. The average particle concentration in ambient conditions was 2030 cm−3, which is higher than the values measured at similar altitude in other regions of the world. On average, the Aitken mode contributed to roughly half of the particle number concentration. The concentrations were found to be higher during the summer than during the winter. The diurnal variation was also investigated and a clear pattern was found for the nucleation mode during all seasons, so that the nucleation mode particle concentration increased in the afternoon. The same pattern was visible in the Aitken mode during the summer, whereas the accumulation mode did not show any level of diurnal pattern during any season. Excluding the nucleation mode, the average day-time particle concentrations were not significantly higher than those measured at night-time, indicating no systematic pattern of change between planetary boundary layer conditions and free troposphere conditions. In air masses coming from east, the number concentration of particles was higher than in other air masses, which indicates that the air mass might be affected anthropogenic pollution east of the station. Also other factors, such as active new-particle formation, keep aerosol number concentrations high in the area.

Final-revised paper