Abstract: A durative regional haze and fog weather occurred in Shanxi Province in November 1994 was comprehensively analyzed based on the observed data. The results are as follows: (1) Front area at 500 hPa was located by north, circulation at midlatitude was straight, and there was a warm advection at 850 hPa to convey continually towards Shanxi. These were the important weather background to form a largescale haze. While blocking situation at 500 hPa maintained stably and the surface refluence was stable to form the largescale fog; (2) Change of relative humidity at 850 hPa was the basic criterion of judging the formation of haze and fog; sustained existence of temperature inversion layer was the important reason for haze and fog; differences of humidity and intensity of temperature inversion layer were the criteria of judging the largescale haze and fog; (3) There was a wholelayer negative vorticity advection, but a weak reversion occurred at 1 000-925 hPa, and it was a dynamic factor for haze; there was a negative vorticity advection near ground surface but a positive one above 925 hPa, or there was a wholelayer positive one, which was the dynamic structure for fog; (4) The total temperature advection diagnosis reveals that there was a warmdry advection conveying to Shanxi before haze but a warmmoisture advection or a coldmoisture conveying to Shanxi before fog. The total temperature advection of haze was larger than that of fog, but the contribution of each component to the total temperature advection was different; (5) The occurring time and duration of haze and fog were quite different, and the meteorological factors were quite different before and after haze and fog occurred. All these could provide the references for forecasting haze and fog weather.

Key words: haze and fog, circulation situation, dynamic structure, relative humidity, vorticity advection, Shanxi Province