Aircraft observations of dust and pollutants over northeast China: Insight into the meteorological mechanisms of transport

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Abstract

[1] The meteorological mechanisms for lofting trace gases and aerosols out of the planetary boundary layer (PBL) into the free troposphere are key to understanding local air pollution problems as well as regional and global atmospheric chemistry and climate issues. Over the North American continent, convective storms and lifting in warm conveyor belts transport pollutants into the free troposphere. Little is known about the vertical distribution of pollutants and dust over east Asia, and the processes leading to transport, transformation, and removal of these species remain uncertain. To provide insight into these mechanisms, we report on eight flights based out of Shenyang in NE China as part of the U.S./China EAST-AIRE project conducted in April 2005. We evaluate profiles of trace species, along with back trajectories and satellite data, in the meteorological context of cyclonic systems. The warm-sector PBL air ahead of a cold front was highly polluted, while in the free troposphere concentrations of trace gases and aerosols were lower, but well above background; we measured ∼300 ppb CO, ∼2 ppb SO2, ∼70 ppb O3, and ∼ 8 × 10−5 m−1 aerosol scattering between ∼1000 and 4000 m altitude. Satellite observations indicate that the entire plume contained almost 105 tons of SO2 and that the gas decayed with a lifetime of 3–5 d. Roughly the same mass of aerosol was transported into the free troposphere. Over the east Asian continent, dry convection appears to dominate with warm conveyor belts first coming into play as the cyclonic systems move off the coast.

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