Abstract:

Based on the relative humidity and visibility data of the surface observation station from 1955 to 2007 and the temperature data of aerological sounding at 8：00 from 2001 to 2007，all records of haze weather were rectified and climatic characteristics of haze were analyzed.The relation between haze and meteorological factors(surface wind direction and velocity，surface pressure，surface temperature，continuous rainless days and aerological inversion layer and isothermal layer，etc.)was also analyzed .The results show that：（1）haze days significantly rose from 1975 and the sum total of annual haze days was 125d or more since 1980s；（2）haze weather was more likely to occur in winter and early spring，especially in January and December，in which half month was not free from haze weather；（3）haze weather was less likely to occur from May to September because of rain；（4）meteorological factors，such as the decrease of surface pressure and the increase of surface temperature，were favorable for the occurrence of haze；（5）if continuous rainless days occurred more in certain month，accordingly，haze days also occurred more in this period；（6）what makes haze days more frequent in recent years is not only the fact that the rapid development of city industry and the reckless destruction of vegetation cause more air pollution，but also that the climatic features of low surface wind velocity，aerological inversion layer and isothermal layer often existing in Yichang are obvious，and that many chemical plants place in the direction of prevailing wind.

Key words: haze/relative humidity/visibility