Spatial And Temporal Evolution Of Aerosols During Haze Days In Guanzhong Area

In recent years,the fog and haze in Guanzhong area is serious relatively,which has posed a great threat to public health and ecological safety.At present,the routine of monitoring air pollution is mainly based on sampling and monitoring by ground-based station instruments.The number of observation sites is limited,which is difficult to observe the distribution of haze and also to get haze change process on the regional scale.In addition,the emission sources in China are complex and changeable,and the differences in different regions are large.Local sampling is easily affected by local emission sources.Therefore,in recent years,more and more scholars have begun to use satellite remote sensing technology to monitor haze.In this paper,DDV and MODIS L1 B data was used,and I used 6S model to build a lookup table.Then,I computed aerosol optical thickness in Guanzhong area during 12 typical haze days periods,getting the spatial distribution pattern of aerosol optical thickness in Guanzhong region during the haze days.Using the HYSPLIT model,the ambient air quality data,terrain and population density,I analyzed temporal and spatial evolution law of haze and explored the possible sources of pollutants.The main conclusions are as follows:(1)Using DDV,I computed aerosol optical thickness in Guanzhong area during 12 typical haze days period on the platform of ENVI5.1.I found that changes of AQI and AOT is same,proving that DDV is suitable for retrieval of aerosol optical thickness in Guanzhong area.(2)Through the AOT results of multiple haze days periods,I got that in the period of severe aerosol pollution in Guanzhong area,the spatial distribution pattern of AOT generally showed the trend of North South low,middle high,west low East high.(3)Through the analysis of topographic features in Guanzhong area,it can be seen that both sides of the terrain area are leaned to the central area and the southern(Qinling Mountains)is higher than the northern(Weibei Beishan area).The east of Weihe plain located in the Guanzhong area is broader than the west.Weihe plain is connected to the Yuncheng basin and Henan Province,with little undulating terrain,which makes the pollutants in the south of Shanxi and the north of Henan may spread to the Guanzhong area so that the haze in Guanzhong area is more serious.Analysizing the topographic features and AOT results,we can find that the spatial distribution pattern of the terrain and the aerosol pollution in Guanzhong area has a very strong correlation with the agreement,in other words,AOT in the northern and southern sides with the high altitudes is relatively small,and AOT in the west of Weihe plain is smaller than AOT in the east.At the same time,considering the distribution of population density in Guanzhong area,we can find that population density in the northern and southern sides of Guanzhong area is relatively small,as the northern and southern sides to the middle,the population density is gradually increased,which has a very strong correlation with the presentation of the AOT's spatial characteristics,that is to say,aerosol pollution in the area with greater population density is more serious.(4)Analysizing the AOT results,air mass backward trajectory,terrain characteristics and population density,aerosol pollution in Guanzhong area during haze days period is mainly produced in local area,but the surrounding area would also transport a part of pollutants to Guanzhong area,including the dust pollution from the northwest and the industrial pollution from the east.Concretely,exogenous pollution is mainly from Pingliang,Qingyang,Yuncheng,Linfen,Sanmenxia,Luoyang and Part of the region in Inner Mongolia,Ningxia,Xinjiang.About evolution in time and space,aerosols pollution is produced in the central and the eastern of Guanzhong area during haze days,then it would spread from east to west,however,the aerosols pollution is limited in the Weihe plain area,and aerosol pollution in Qinling Mountains and Beishan area of Weibei is relatively light,at the same time,the surrounding area may transport part of pollutants to Guanzhong area,leading to more serious aerosol pollution,usually because of the southwest and northwest high altitude air,aerosol pollution in Guanzhong area is dissipated from west to East.