Study On The Change Characteristics And Causes Of The Haze Weather In Tianjin

In recent years,with the rapid development of economics,the acceleration of urbanization and the rapid increase of motor vehicles,haze phenomenon occurs more and more frequently.Tianjin is an important part of the Beijing-Tianjin-Hebei region,if we can effectively prevent and control the phenomenon of haze in Tianjin,the haze weather of Beijing-Tianjin-Hebei region will be well controlled.To better understand the characteristics,the influencing factors and the development process of haze weather in Tianjin,can provide scientific basis for the government to develop haze prevention and control policy and measures.In this paper,we selected the following data as the initial data: the meteorological observation data(timing visibility,timing temperature,timing barometric pressure,timing relative humidity,timing wind speed and timing wind direction at 2: 00,8: 00,14: 00,20:00)of three typical areas(Jixian,Xiqing and Tanggu)in Tianjin from January 1st,1994 to December 31 st,2013,the observation data(hourly relative humidity,hourly visibility,500 hPa altitude and ground analysis maps)of Tianjin from January 1st,2016 to March 31 st,2016,and the pollutant data(hour-by-hour AQI value,concentrations of hourly PM2.5,PM10,CO,SO2,NO2,and O3)of Tianjin from January 1st,2016 to March 31 st,2016.After the initial data Screening,statistics and integration according to the actual research needs,combining with the definition of haze in the Meteorological Observing Regulations,and the local climatic characteristics and actual observation experience,the general trends of haze weather conditions were analyzed.We selected three typical haze weather processes,and analyzed the change characteristics of circulation patterns,and the trends of pollutants in haze process,to explore the causes of haze weather in Tianjin area and put forward the prevention and control measures of haze weather.The main findings are as follows:(1)The haze weather in Tianjin area has obvious regional differences,the number of haze weather days in Tanggu area is the least,but the number of haze days in Xiqing area increased the fastest.Overall,the total haze weather days in Tianjin in recent years showed an increasing trend.The main haze weather concentrated in winter and spring.Daily change showed that,the haze phenomenon is most likely occur in the afternoon.With the rapid development of the city and the increasing number of vehicles,the duration of the haze phenomenon in Tianjin increased obviously.(2)Stable weather situation forms haze weather more easily,and cold air contributes to the dissipation of haze.The changing trend of AQI reflects the process of the generation,development and dissipation of haze weather.In most cases,the primary pollutant affecting haze weather is PM2.5 or PM10.In the haze weather process,the relative humidity will increase the haze weather phenomenon in a certain humidity range,and the increase in wind speed will quickly dissipate the haze.(3)The major pollutants in haze weather in Tianjin are PM10,PM2.5,CO,nitrogen oxides,sulfides and so on.Human factors have more influence on haze weather than natural factors.Human activities determine the quantity and types of pollutants in the air.Meteorological conditions determine the diffusion rate of pollutants.Urban heat island effect increases the frequency and intensity of haze occurrence.Among the variety of meteorological factors,wind and rainfall influence haze weather phenomenon most directly,and the relative humidity,temperature,and pressure also influence the haze weather at different levels.During 2008-2013,94.9% haze phenomenon in Tianjin occurred when wind speed is≤ 5m/s,and 66.4% of haze weather occurred when the relative humidity is between 50%-70%.