| Along with rapid development of urbanization and industrialization,the quantity of vehicles increases rapidly;the pollutant discharge increases greatly;hazy weather has become the important problem causing air pollution in some large and medium cities in China.The pollutants discharged to atmosphere by the industry and traffic transportation industry in the middle area of Liaoning increase gradually;and the atmospheric visibility decreases.Therefore,it studies long-term spatial and temporal distribution and evolution trend of sustainable haze in the central area of Liaoning,starts from main circulation and weather system of several representative cities of Liaoning during sustainable haze period from an angle of synoptics,verifies the reason of pollution formation,development and maintenance,and has guiding significance on realizing forecast and early warning of hazy weather.The paper utilizes meteorological data(relative humidity,visibility and precipitation)of ground observation stations in six cities(Shenyang,Anshan,Benxi,Dalian,Dandong and Fushun)during 1961 to 2010 makes statistics on fog days and haze days of Liaoning by fog and haze judgment methods and gives analysis on time distribution features.According to the restrictions of six pollutant concentrations,including SO2?NO2?PM10?PM2.5?O3 and CO,in 2012 ambient air quality standards(GB3095-2012),we selected 37 continuous air pollution processes as samples from 4 atmospheric composition monitoring stations of Liaoning from Janl,2010 to Dec31,2010.And then we utilized the simultaneous NECP of the samples to analyze the date.After a general analysis to Sea Level Pressure over East Asia,we know that there are five weather systems which contribute to the persistent pollution in Liaoning----Mongolia high,denatured high,Mongolian cyclone,weak depression and Jiang-huai cyclone.At the same time,this paper also analyzes the characteristics of the five types of circulation and explains their origins.(1)The distribution characteristics of haze accidents in the middle area of Liaoning during 1961 to 2010:The fog day has certain spatial and temporal distribution rule;the frequency of its occurrence is high in coastal city and low in inland city;its annual change has large difference between the coastal city and the inland city;in terms of interannual change of the fog day,the fog day number in the eastern mountainous city of Liaoning increases in overall;the fog day number of other cities reduces in overall.The haze day in each station is in monocyclic peak-valley distribution;the haze day number reaches the maximal in Jan and the minimal during Apr.to Jul.Based on the seasons,the haze day number is large in winter and autumn and small in summer and spring.From the comparison among different cities in the middle area,the occurrence frequency of haze day is obviously higher than that of the fog day;there is no necessary connection between the haze frequency and the fog frequency in each city.From the spatial and temporal distribution rule,there is closer relationship between the fog condition and the moisture condition in terms of factor,while the relationship between fog and pollutant concentration is closer;therefore,guiding significance on specific air quality is fog.(2)The weather types causing sustainable fog and haze process in Liaoning can be divided into five types:Mongolian high-pressure type,degeneration high-pressure type,Mongolian cyclone type,weak low-pressure type and Yangtze-Huaihe cyclone type.The occurrence times of each type and the proportion of times in total times are calculated;wherein the frequency of regional sustainable haze weather caused by Mongolian cyclone is the maximal,which reaches 32.7%;the frequency of regional sustainable haze weather caused by Yangtze river and Huai river is the minimal,which reaches 6.1%.autumn and winter are prevalent seasons of sustainable hazy weather process of Mongolian high-pressure type,degeneration high-pressure type,Mongolian cyclone type,while summer is the prevalent season of weak low-pressure type and Mongolian cyclone type.Through diagnosis and analysis on relevant physical quantity fields,it discloses surface layer atmospheric diffusion before and after the hazy weather process.The result shows that Yangtze river and Huai river cyclone is close to Mongolian high-pressure type in terms of horizontal airflow convergence,vertical airflow conveying,stability of atmospheric stratification and temperature inversion trend,except that it has larger temperature inversion strength.Compared with the two types above,the other three types have equivalent horizontal convergence;but they are weaker in downdraft,stability of atmospheric stratification and temperature inversion phenomena obviously.(3)Through statistical analysis on total sustainable haze processes in the middle area of Liaoning during Jan.1,2010 to Dec.31,2012,it obtains the meteorological factor interval of critical moment when haze phenomenon occurs under different weather typing.Therefore,the sustainable haze process of weak low-pressure type and Yangtze river and Huai river cyclone type has low humidity and gives priority to haze;when the sustainable haze process of degeneration high-pressure type,weak low-pressure type and Yangtze river and Huai river cyclone type has low critical wind speed,which means three types can form and keep haze weather under calm wind and small wind conditions.(4)Comparing the third generation Models-3 for regional air quality model system to simulate the particle concentration distribution and delivery.(1)Mongolian(1)Mongolian high-pressure type,in the process of the persistent haze,anshan,liaoyang and benxi pollution sources of fine particles diffusion to disadvantage of shenyang and fushun.(2)denatured hig,the conveying of the westerly flow in the area of anshan,liaoyang fine particle diffusion to lee benxi,fine particle diffusion to fushun in shenyang;After the wind gradually into the mistral,shenyang fine particles directly to benxi.(3)Mongolia cyclone type of fog,the other cities except anshan fine particle concentration is not large,then liaoyang pollution emissions continue to increase,and anshan together,the two cities influence each other.(4)The weak depression,anshan,benxi fine particle concentration is larger,with fine particles of benxi to fushun the south wind.Since then,the wind direction change again,shenyang fine particles transported to liaoyang,anshan.The haze in the process of shenyang,anshan,benxi fine particles in some period of time into a whole,can reflect the severity of the regional haze.(5)The whole process of jianghuai cyclone type of fog in the area for the westerlies,anshan,liaoyang pollution sources to merge,always affects the lee side of benxi,the shenyang fine particle was continuously to fushun. |
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