Spatial and Temporal Variations of Hazes in Guangxi from 1960 to 2009

With the development of Guangxi economy and accelerating urbanization, human activities have discharged various pollutants into the atmosphere, which cause increasing atmospheric haze phenomenon in recent years. The toxic and harmful substances of hazes affect human health and environment a lot, becoming a new kind of severe weather. So it is very important to analyze the spatial-temporal variation characteristics of haze, which provide scientific bases for effective forecasting and controlling haze weather. Based on the data provided by 80 surface observation stations from 1960 to 2009, the haze days in Guangxi are calculated, and the characteristics of spatial-temporal variations of haze in Guangxi and its relationship with climate elements are analyzed by using EOF, linear trend estimation and other analytical methods. The average annual haze days in Guangxi are found to rise gradually over the past 50 years, which is closely related to the human activity and the increase in emissions by economic development. The haze happens more frequently in major cities and their surrounding areas than in remote areas and coastal areas. Comparing the periods of 1960—1979 and 1980—2009, and the remote areas and coastal areas, the haze days increase by different degrees in most parts of Guangxi, especially in Wuzhou, Liuzhou and other industrial cities. Haze in Guangxi occurs mainly in autumn and winter rather than in spring and summer, which may be the results of less precipitation. Compared to the 1960—1979 stage, the average monthly haze days increase significantly in 1980—2009 stage, especially in flood season. Haze days increase most significantly in December by 3.5 d, while in July increasing only 0.2 d. The average annual haze day in Guangxi over the past 50 years is 30.0 d, and the maximum is 61.7 d, which occurs in 2006. When haze weather occurs, the visibility distance mostly ranges from 5 km to 10 km, and the relative humidity mostly ranges from 70% to 90%. The change of haze days in Guangxi is proportional to temperature, and inversely proportional to wind. So, in addition to air pollution, the long-term decrease trend of wind speed in the last 50 years may have caused more hazy days.