Abstract: Based on the meteorological and environmental data, a continuous floating dust pollution event on May 12, 2011 in Changchun was analyzed by methods of a climate statistics, a circulation evolution, a physical diagnosis and a back trajectory analysis. The results show that the annual dust day is in a fluctuant decreasing trend in Changchun. The dust weather mainly occurs during March to May. The sand source is originated from the central Mongolia and mid-eastern of Inner Mongolia, and the dust is transported to northeast China with upper jet stream. There is no local sand source in this process. It is a continuous floating dust process rather than a sandstorm because of obviously upper jet stream, smaller surface wind speed, larger temperature dew point difference, weak wind areas in the eastern Inner Mongolia and northern Liaoning province and stable atmosphere in the whole layer.

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