Study On Estimation Of Ground-Level PM_2.5 Based On AOD Vertical-and-RH Correcting Method

According to the requirements of national development,Sichuan Province and Chongqing City are the largest population and economic gathering places in Southwest China,They will work together to build a two-city economic circle in Chengdu-Chongqing area,and maximize the economic development in Western China,Therefore,it is anxious to study and evaluate the regional atmospheric environmental air quality.In this thesis,we notice that there are some problems in the estimation of atmospheric particulate matter concentration in Sichuan and Chongqing.First of all,due to the anxious terrain conditions in Sichuan and Chongqing region and the meteorological conditions with more cloud coverage weather,it is too difficult to estimate the PM_2.5concentration near the ground by using remote sensing,so there is less research on PM_2.5concentration estimation in this region by using satellite remote sensing.Secondly,most of the current studies use vertical correction and humidity correction methods to correct the humidity of the whole study area by fitting a hygroscopic growth factor,which can not well reflect the changes of hygroscopic growth characteristics of each site.In respect of the issues above,In Sichuan-Chongqing area,the method of fitting hygroscopic growth factors month by month and site by site to construct hygroscopic revised factor grid reflects the temporal and spatial differences in the hygroscopic growth characteristics of aerosols,and finally estimates more accurate PM2.5 concentration.The main research contents are as follows:1.Considering the complex terrain of Sichuan and Chongqing,this study uses the visibility information provided by regional encrypted meteorological monitoring stations to calculate the hight of each station;Then,the inverse distance weighted spatial interpolation method is used to get the hight of adjacent pixels,so as to get the near ground extinction coefficient of all pixels in the region,and realize the vertical correction;Based on the statistics of regional data,it is found that the moisture absorption growth characteristics of aerosol particles vary greatly in different regions and time ranges.Therefore,the traditional humidity correction is improved,that is,fitting the moisture absorption growth factor monthly to reflect the temporal differences of aerosol moisture absorption growth characteristics,fitting the moisture absorption growth factor site by site to reflect the spatial differences.Finally,the inverse distance weighted spatial interpolation method is used to construct the hygroscopic correction factor grid to accomplish regional humidity correction.Compared with the relationship between aerosol optical thickness and PM_2.5.It is verified that this method can improve the correlation between aerosol optical thickness and PM_2.5.2.After the PM_2.5 concentration on the ground near the ground in Sichuan and Chongqing region was estimated by using the vertical correction and improved humidity correction,the multiscale verification of the estimated results shows that the correlation coefficient between the satellite estimation value and the ground observation value is high,therefore,the estimation result is fine.Finally,the spatial distribution map of PM_2.5concentration was drawn based on the estimation results,and the temporal and spatial distribution of PM_2.5 concentration in Sichuan and Chongqing region from 2017 to 2018was studied.