Abstract:The aim of this paper is to investigate spatial temporal characteristics of the haze spanning 1971-2007 over Hebei Province of North China using the observations from 142 stations. Our study demonstrates that the haze frequency is changed with location and month, for example more haze appeared in piedmonts than in mountains or flat areas, while the haze was concentrated in winter (December and January) and least frequent in August and September. By using the observations about the 500 hPa height and the sea level pressure from 2004 to 2007, the conclusion can be drawn that the 500 hPa circulation patterns can be divided into 5 categories, including zonal circulation pattern, two troughs and one ridge pattern, mean height pattern, one trough and one ridge pattern and pattern of two ridges and one trough. A further analysis implies that the haze frequency also relies on local air pollution and regional circulation pattern dominant in addition to the terrain of surroundings. Above results are valuable to understand the forming mechanism and to establish a forecast system of haze over Hebei Province.