Study On PM2.5 Estimation In Beijing-Tianjin-Hebei Region Based On MODIS Data

Based on the medium-resolution MODIS data,this paper uses the Beijing-Tianjin-Hebei region as the research area to carry out the inversion of the spatial resolution of aerosol optical thickness(hereinafter referred to as AOD)in Beijing-Tianjin-Hebei region from 1 to 20 in 2014-2018.Combined with the data of ground air quality monitoring station,the relationship between AOD(550nm)and PM2.5 concentration was analyzed,and the regression fitting model of the two was established.The PM2.5 concentration was estimated by AOD,and the PM2 of BeijingTianjin-Hebei region was analyzed in the past 5 years.The spatial and temporal distribution characteristics of.5 concentration,evaluation of PM2.5 concentration and natural factors(the three meteorological elements of temperature,precipitation and wind speed and the elevation as representative of natural factors)and human factors(ground carbon monoxide concentration,ground sulfur dioxide concentration,ground PM10)The correlation and correlation between concentration,groundlevel nitrogen dioxide concentration and ground-level ozone concentration as representative of human factors provide decision-making basis for future air quality monitoring and air pollution control.The paper concludes as follows:(1)Using the dark pixel algorithm,the average and annual mean images of AOD in the Beijing-Tianjin-Hebei region from 2014 to 2018 were obtained.In the season,the AOD in the Beijing-Tianjin-Hebei region is the highest in summer,followed by spring,followed by autumn,and the winter is the smallest.The main reason for the high AOD in summer may be that the summer precipitation in the Beijing-Tianjin-Hebei region is larger than other seasons,resulting in an increase in moisture in the air.The effect of aerosol system on the weakening of light;on the annual,it shows a trend of decreasing year by year;spatial distribution,northeast is high,southwest is less,southern AOD value is mostly above 0.7,northern AOD value is generally between 0-0.4,and The distribution of DEM is similar.The main reason for this situation may be that the aerosol particles in the higher terrain are disturbed by the complex topographic airflow,which causes the weakening of the aerosol system in the northeastern part of Beijing,Tianjin and Hebei.It is larger than the northwestern part of Beijing-Tianjin-Hebei.(2)Analyze the correlation between AOD(550nm)and PM2.5 concentration,establish a regression fitting model for the whole year,season,and month,and select the optimal regression fitting model to derive PM2 from AOD(550nm)..5 concentration.(3)Annual distribution characteristics and regional differences of PM2.5 concentration in 2014-2018: The highest concentration of PM2.5 in winter,followed by spring,followed by autumn,and the lowest is summer,PM2.5 concentration decreases year by year,spatial distribution AOD is similar,and it is also high in the northeast and low in the southwest.The main reason for this situation may be that the heating pressure in the Beijing-Tianjin-Hebei region is relatively high in winter,and the fuel consumed by heating will cause an increase in the concentration of PM2.5.There are many winds in the area,sometimes accompanied by sandsanding weather.In summer,the Beijing-Tianjin-Hebei region has more precipitation,and the PM2.5 particles in the air will be washed and settled to the ground,so the winter is the highest,followed by the spring,followed by the autumn and the summer.The regional distribution difference of PM2.5 concentration is basically similar to that of AOD,mainly affected by topography.The higher concentration areas are mainly concentrated in the southeast.The PM2.5 concentration value is generally above 50μg/m3,and the low value is mostly In the northern region,the PM2.5 concentration is generally between 0-50μg/m3,and the overall PM2.5 concentration increases gradually from northwest to northeast,and the concentration of PM2.5 in the coastal areas of the Bohai Sea region is lower.(4)The relationship between PM2.5 concentration and natural factors and human factors in 2014-2018: PM2.5 concentration is mainly affected by human factors,which may be directly related to the burning of fossil fuels.PM2.5 particles may come from industry.Among the flue gases emitted from fossil fuel combustion,the influence of wind speed on PM2.5 concentration is the largest among natural factors.As the wind speed increases,PM2.5 particles will diffuse with the circulation of air,thus reducing PM2.5 in the region.concentration.