Dust events in Beijing, China (2004–2006): comparison of ground-based measurements with columnar integrated observations 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
2Leibniz-Institute for Tropospheric Research, 04318 Leipzig, Germany
3Atmospheric Environment Division, National Institute for Environmental Studies, Tsukuba, Japan
Received: 09 Jan 2009 – Published in Atmos. Chem. Phys. Discuss.: 14 May 2009 Abstract. Ambient particle number size distributions spanning three years were used to
characterize the frequency and intensity of atmospheric dust events in the
urban areas of Beijing, China in combination with AERONET sun/sky radiometer
data. Dust events were classified into two types based on the differences in
particle number and volume size distributions and local weather conditions.
This categorization was confirmed by aerosol index images, columnar aerosol
optical properties, and vertical potential temperature profiles. During the
type-1 events, dust particles dominated the total particle volume
concentration (<10 μm), with a relative share over 70%.
Anthropogenic particles in the Aitken and accumulation mode played a
subordinate role here because of high wind speeds (>4 m s−1). The
type-2 events occurred in rather stagnant air masses and were characterized
by a lower volume fraction of coarse mode particles (on average, 55%).
Columnar optical properties showed that the superposition of dust and
anthropogenic aerosols in type-2 events resulted in a much higher AOD
(average: 1.51) than for the rather pure dust aerosols in type-1 events
(average AOD: 0.36). A discrepancy was found between the ground-based and
column integrated particle volume size distributions, especially for the
coarse mode particles. This discrepancy likely originates from both the
limited comparability of particle volume size distributions derived from Sun
photometer and in situ number size distributions, and the inhomogeneous
vertical distribution of particles during dust events.
Revised: 25 Aug 2009 – Accepted: 07 Sep 2009 – Published: 22 Sep 2009
Citation: Wu, Z. J., Cheng, Y. F., Hu, M., Wehner, B., Sugimoto, N., and Wiedensohler, A.: Dust events in Beijing, China (2004–2006): comparison of ground-based measurements with columnar integrated observations, Atmos. Chem. Phys., 9, 6915-6932, doi:10.5194/acp-9-6915-2009, 2009.