Study on the characteristics and influence factors of the haze in Shanghai

The haze days from December 2009 to November 2010 in Shanghai are analyzed by using meteorological data, particulate matter data and the method of back-trajectory-cluster analysis. The results are as follows: Northwest and southwest flows from inland are prevailing in haze days. In autumn and winter, the flows from northwest are more prevailing, while in summer, the flows from southeast are more prevailing. In spring, the numbers of the flows that are from northwest and southwest are very same. The occurrence of haze days in Shanghai are affected by both local factors and the long distance transportation of flow from other places, and the local factors are the major impacts. The high relative humidity and low wind speed are conducive to occurrence of haze. Fine particulate matters have great impacts on the occurrence of haze days. And the occurrences of the haze in Shanghai have relation with vehicle exhaust emission.