Analysis Of Temporal And Spatial Variation Of Aerosol Optical Depth In Chengdu Based On GF-1 Data

In recent years,with the rapid development of China's economy,the consumption of various types of energy sources has been increasing,and the large amount of polluting gas emissions has made the pollution of the atmospheric environment more and more serious and urgently needs to be resolved.North China-Guanzhong Plain area,East China area,South China area and Sichuan Basin are the areas with the most serious atmospheric pollution problems and the most obvious decrease in air visibility since the implementation of the reform and opening policy in 1978.It has also become a key area for scholars at home and abroad to study air pollution.However,in the past,many studies have focused on the Beijing-Tianjin-Hebei region,and there have been very few studies on the mega-city in the Sichuan Basin with special topography—Chengdu.In this paper,based on the GF-1/WFV data combined with the dark blue algorithm and the improved MODIS blue band surface reflectivity database,the inversion of Chengdu Aerosol Optical Depth(AOD)is used to reflect the pollution degree of the Chengdu atmospheric environment,And on the basis of accuracy verification,not only analyze the spatial and temporal distribution characteristics of AOD in Chengdu,but also analyze the relationship between AOD and surface characteristics in combination with the underlying surface(land cover type,vegetation factors,topographic factors)for discussion The underlying surface factors that affect the temporal and spatial changes of AOD.The research conclusion is as follows:(1)The correlation coefficient between the AOD inversion results and MODIS AOD is 0.736;the correlation coefficients with PM_2.5and PM₁₀ are 0.906 and 0.879;the correlation coefficients with the ground-based AOD is 0.988;The 0.001 level is extremely significant.This shows that the accuracy of the AOD results of the inversion in this paper is high,which proves that the GF-1/WFV data and the dark blue algorithm are suitable for the Chengdu AOD inversion.(2)From 2015 to 2018,the mean AOD of Chengdu showed the characteristics of"high-low-high-low".Qingyang District,Jinniu District,Wuhou District and Chenghua District,AOD values are generally higher,of which the highest AOD average value is Jinniu District.Chengdu has the highest AOD value in winter,followed by spring,and again in summer.The lowest AOD value is autumn.(3)When the air quality is good,the average AOD of Chengdu is 0.4472,the highest AOD is Qingyang District,followed by Wuhou District,and then Pujiang County;when the light pollution is the largest,the average AOD is Xindu District,followed by Wuhou District,once again Jinniu District;a total of 18 districts(counties and escrow cities)with an average AOD greater than 1.5 in moderate pollution;AOD distribution in severe pollution is clearly divided into two parts,the AOD value in the northwest region is mostly less than 1.0,while other regions The AOD values are all greater than 1.0.(4)NDVI,altitude,and slope are all negatively correlated with the AOD value.The correlation coefficients are-0.399,-0.389,and-0.274.Therefore,when the altitude is low,the slope is slow,or the vegetation is sparse,the AOD value is high.This is mainly due to the fact that places with lower elevations or slower slopes are suitable for human habitation or construction of industrial areas.They have many pollution sources and sparse vegetation.They do not have a strong fixation effect on the surface and poor adsorption of pollutants.(5)Different land cover types have different effects on the AOD value,which is as follows:the average AOD of different land cover types differs significantly,and the corresponding AOD averages from large to small are artificial surface,unused land,water body,cultivated land,grassland,forest land.(6)AI,PRAFRAC and MN of cultivated land are positively correlated with AOD value;AI,MN,PD,LPI,Division and PRAFRAC of artificial surface are positively correlated with AOD value;AI,PRAFRAC,MN,Division and PD of forest land are all AOD value is negatively correlated;grassland PRAFRAC and MN are significantly negatively correlated with AOD value.Therefore,when carrying out land planning,the destruction of existing forest land and grassland should be avoided,and the development of forest land and grassland in the direction of fragmentation and distribution should be avoided,and the interference of human activities on grassland and forest land should be minimized.A large amount of green vegetation should be planted on the artificial surface and around the cultivated land to avoid the excessive advantages of these two types of land cover,and at the same time,a certain dust reduction effect can be achieved through the adsorption of vegetation.