Observations on haze and fog in Shenyang area

In order to study the temporal variation of haze and fog in Shenyang,haze and fog times were determined from the hourly visibility,particle concentration,relative humidity and weather patterns,observed for one whole year from 1 June 2009 to 31 May 2010.Based on the experimental criteria and definitions,the haze times account for 53.9% of the total observations;far higher than the fog proportion of 8.4%.Considering the temporal variation,haze occurs most frequently in winter and fog reaches a peak in summer.They both appear comparatively frequently in autumn,while rarely in spring.The seasonal variation of particles is the same as that of haze,which means that haze is closely associated with air pollution and visibility.Haze is definitely an indicator of the city air quality.Haze times from mild to severe grade account for 72.1%,18.2%,6.5% and 3.2% of the total observational times.The proportion of medium and severe grade haze times is rather low.It can be seen that human health has not been affected seriously in Shenyang,but everyone should take health precautions in autumn and winter.